Extraordinarily harvesting waste heat by thermally regenerative Zn-ion battery

Extraordinarily harvesting waste heat by thermally regenerative Zn-ion battery | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Extraordinarily harvesting waste heat by thermally regenerative Zn-ion battery Lidong Chen, Xiaoling Sun, Hongyi Chen, Yitong Li, Dewen Zeng, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3679010/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Typical technologies that can convert waste heat into electricity include thermoelectrics, thermionic capacitors, thermo-cells, thermal charge cells, and thermally regenerative electrochemical cycles. They have small thermal-to-electrical conversion efficiency or poor stability, severely hindering the efficient recovery of waste heat. Herein, we successfully developed a thermally regenerative Zn-ion battery to work under Carnot-like mode to efficiently harvest waste heat into electricity. Through introducing Layered Double Hydroxides to modify battery’s anode reaction, a record absolute high temperature coefficient of 2.944 mV/K is achieved in NiHCF/Zn battery, leading to a high thermal-to-electrical conversion efficiency of 29.24% of the Carnot efficiency and an extraordinary energy efficiency of 104.11% when the battery is charged at 50 ℃ and discharged at 5 ℃. This work demonstrates that the thermally regenerative batteries can effectively harvest waste heat to provide a powerful energy conversion technology. Physical sciences/Materials science/Materials for energy and catalysis/Batteries Physical sciences/Energy science and technology/Energy storage/Batteries Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction More than 50% of global energy ends up as waste heat, including all manner of human activities, natural systems, and all organisms. Among various technologies for waste heat recovery, thermoelectrics have a simple working structure with the advantages of quiet, reliable, and long service life, but they have small open voltages and low energy conversion efficiency because their working substance is electrons or holes 1–5 . Thermionic capacitors 6–8 and thermo-cells 9–11 based on ion diffusion and/or reactions have the advantages of large open voltages, but the generated electricity is intermittent and working modes are usually very complicated. Combining the technology of thermo-cells and regular batteries leads to the discovery of thermal charging cells. It has the advantage of a relatively high average output voltage (0-0.5 V) as compared with thermos-cells, but a large temperature difference between anode and cathode is required that is hardly realized in practical batteries 12–14 . All the above technologies work under a certain temperature gradient, which is far beyond the equilibrium state. Thus, many of the heat energy is dissipated into the environment and the thermal-to-electrical energy conversion efficiency ( η TTE ) is low (usually less than 12% of the Carnot efficiency η C under a temperature difference of 50 ℃). In addition, the measured output voltage in thermo-cells and thermal charging cells contains the contributions from ion diffusion, interface polarization, and the voltage temperature coefficient of battery. The former two terms are one-off, leading to the rapid decay in the output voltage during working. The term of battery’s voltage temperature coefficient can provide a stable and continuous electric output, but the absolute value is very small (usually less than 10% of the output voltage) that has not been accurately measured yet. Carnot-like cycle is a near equilibrium process. Thus, the η TTE can be very high because the heat energy dissipated into the environment is extremely small. Thermally regenerative electrochemical cycle (TREC) is a typical Carnot-like (Stirling-like electrical) cycle. During working, the system is charged at high temperature, and then naturally cooled to low temperature and finally discharged at this temperature. If the temperature coefficient of system’s voltage ( α ) is negative, the absorbed heat at high temperature can be converted to electricity at low temperature and finally released along with the charged electricity. An absolute larger α value leads to a higher η TTE . Currently, the | α| in TREC is in the range of 0.74–2.27 mV/K and relative Carnot efficiency ( η TTE / η C ) is in the range of 5.6–25% 15–25 . However, these electrochemical cells usually have small working voltages (< 0.8 V) and/or poor cycling stability (10–160 cycles at 5% capacity attenuation), which greatly impede their wide applications in energy conversion and storage. In contrast, regular batteries have the advantages of large working voltage (1.4–3.8 V), good cycling stability (400–3000 cycles), fast response speed, and portability 26–31 as well as extremely high energy conversion efficiency between chemical energy and electricity 32–35 . Using regular batteries to harvest waste heat under Carnot-like mode can realize a novel and efficient thermally regenerative battery (TRB) technology, but it has not been realized until today because of the low (0.05–1.46 mV/K) 25,36,37 or the absence of battery’s temperature coefficient. Herein, we successfully developed a thermally regenerative Zn-ion battery to work under Carnot-like mode to extraordinarily harvest waste heat (Fig. 1 a). By introducing a Layered Double Hydroxides (LDH) into the anode reaction, extremely high battery’s temperature coefficient of 2.944 mV/K and η TTE / η C of 29.24% (Fig. 1 b and Table 1 ), and extraordinary charge-discharge Energy Efficiency ( EE ) of 104.11% (Fig. 1 c) with a large working voltage (1.49 V) and good cycling stability (up to 650 cycles with a capacity attenuation of 1.93%) are realized when the battery is charged at 50 ℃ and then naturally cooled to 5 ℃ for discharge. This study suggests that TRB is one of the most promising technologies for harvesting waste heat (Table 1 ), which can effectively collect extra electricity in the daytime and then efficiently provide more than 100% of the charged electricity to users such as electric vehicles at night (Fig. 1 a). The structure of NiHCF/Zn battery is shown in Fig. 1 a. Nickel hexacyanoferrate (KNi II Fe III (CN) 6 , NiHCF) is taken as cathode, zinc is taken as anode, and KCF 3 SO 3 and Zn(CF 3 SO 3 ) 2 are taken as the mixed electrolyte. The chemical reactions of two half cells are shown in Reaction S1 and S2. In order to realize a Carnot-like mode, a Stirling-like electrical cycle is built. It contains four steps (Fig. 2 a). For the first step, the battery is heated to a high temperature with the open circuit voltage (OCV) decreasing to V ( T H ). For the second step, the battery is charged at this high temperature with the heat energy and electricity stored as chemical energy. For the third step, the battery is cooled to a low temperature with the OCV increased to V ( T L ). During this step, part of the absorbed heat is converted to chemical energy. For the fourth step, the battery is discharged at this low temperature with all the stored chemical energy released. Table 1 | Summary of various technologies for harvesting waste heat. Thermo-electrics Thermionic capacitors Thermo-cells Thermal charge cells TREC TRB Temperature gradient across the device Yes Yes Yes Yes No No working under equilibrium state No No No No Near Near η TTE / η C 5-16% 0.03-8.46% 0.01-12% 5.2-7.25% 5.6-25% 29.24% Output voltage Stable Unstable Unstable Unstable Stable Stable Output voltage for single-pair device 0-0.1V 0-0.03V 0-0.1V 0-0.5V 0.21-0.81V 1.49V Working lifetime > several years 15-1000 cycles at 6% capacity attenuation >100 hours 50-100 cycles 10~160 cycles at 5% capacity attenuation 650 cycles at 1.93% capacity attenuation extra heat exchange Yes Yes Yes Yes No No Battery’s temperature coefficient of voltage ( α cell ) directly determines how much heat energy can be converted to chemical energy during the electrochemical Stirling-like cycle. It contains the contributions from the reactions at anode ( α + ) and cathode ( α − ). Thus, the α cell = α + - α − , where the α + and α − can be given by the Nernst equation (Eqs. (S3 and S4)). The battery’s temperature coefficient of voltage is carefully measured. Both the α + and α − increase when increasing K + and Zn 2+ concentrations, which can be well described by the Nernst equation (see Fig. 2 f,g). The minimum α + (-0.826 mV/K) and maximum α − (0.692 mV/K) are obtained when the K + and Zn 2+ concentrations are 0.2 mol/L and 1.0 mol/L, respectively. However, the battery is unstable and has larger polarization when K + concentration is lower than 0.5 mol/L. Therefore, the NiHCF/Zn battery is assembled using the K + concentration of 0.5 mol/L and Zn 2+ concentration of 1.0 mol/L, leading to a total α of -1.221 mV/K. We further test the battery’s performance. A η TTE / η C of 14.60% is obtained when the battery is charged at 50 ℃ and then discharged at 5 ℃, resulting in an EE of 95.05% as compared with the value of 92.01% when the battery is charged and discharged at 5 ℃. Battery’s temperature coefficient is determined by its entropy ( ΔS ), which can be significantly changed by modifying ion’s types and concentrations ( \(\varDelta S\stackrel{\scriptscriptstyle\text{def}}{=}-{k}_{B}\text{ln}\left(\right[x\left]\right)\) ) 20 , where k B is the Boltzmann constant and x is the effective concentration of ions. Here, by adding 0.05 mol/L of NiSO 4 into the electrolyte, an extra chemical reaction occurs at the surface of Zn/Zn 2+ electrode Zn-2e + x Ni 2+ + y SO 4 2− + z OH − + w H 2 O ↔ ZnNi x (SO 4 ) y (OH) z · w H 2 O ( 1 ) ZnNi x (SO 4 ) y (OH) z · w H 2 O has a typical Layered Double Hydroxides (LDH) structure (shown in Fig. 2 b). It has two layers. One layer is ZnNi x (OH) z , and another is ZnSO 4 and water. Strong hydrogen bonds are existed between these layers. Except Zn 2+ , the LDH material contains Ni 2+ and SO 4 2− , which may give additional contributions to battery’s temperature coefficient. The LDH material on anode’s surface is characterized and confirmed by various techniques. Scanning electron microscope (SEM) measurements show that numerous nanoscale flakes are observed (Fig. 2 c and Extended Data Fig. 1 a), which are consistent with the character of layered structure in LDH 45,46 . Energy Dispersive Spectrometer (EDS) mapping revealed the uniform distribution of Zn, Ni, O, and S elements from 100 nm to 10 µm and the molar ratio of Ni: S close to 1: 1 (Extended Data Fig. 1 a). The X-Ray Diffractometer (XRD) pattern matches well with that of Zn 3.52 Ni 1.63 (SO 4 ) 1.33 (OH) 7.64 ·4.67H 2 O (Fig. 2 d) 47 . Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectra (Fig. 2 e) show that the absorption peaks locate at 400–800 cm − 1 , 964 cm − 1 , and 1635 cm − 1 , which are also consistent with the characteristic vibration peaks of Zn/Ni-OH, SO 4 2− and H 2 O in LDH materials 48–50 , respectively. Compared with the pristine battery, the α + in the modified battery is slightly decreased to about 0.02 mV/K. It still increases with the increase of K + concentration, consistent with the Nernst equation (Fig. 2 f). However, the α − in the modified battery is greatly different from the previous one (see Fig. 2 g). It is increased to 2.120 mV/K, 3.18 times of the pristine one, when the Zn 2+ concentration is 0.05 mol/L and K + concentration is 0.5 mol/L. Furthermore, the α − decreases when increasing Zn 2+ concentration, which is completely different from the Nernst equation. The temperature coefficient of the full NiHCF/Zn-LDH battery is measured at 50% state of charge (SOC). The battery has accurate and rapid response to temperature (Extended Data Fig. 5b). The potentials show linear changes to temperature (Extended Data Fig. 3 d) and the slope is the temperature coefficient. It is -0.827 mV/K and 2.116 mV/K for the reactions at the cathode and anode, respectively. Ultimately, the NiHCF/Zn-LDH battery has a very high absolute α of 2.944 mV/K, superior to all the reported electrochemical cells near room temperature (Fig. 2 h). We simulate the Stirling-like cycle for NiHCF/Zn-LDH battery with the data shown in Fig. 3 a,b. A charging and discharging range of 15–85% SOC is chosen. First, the battery is charged at various high temperatures but discharged at 5 ℃ under a current density of 11.2 mA·g − 1 (0.2 C). Although the charging temperature is different, the difference in discharge voltage is small with the error bar less than 1.85%, indicating that battery’s discharging performance is rarely affected. However, the charging voltages are significantly reduced when increasing charging temperature. Specifically, we test the battery via charging at 50 ℃ and discharging at 5 ℃ under different current densities. When the current density increases, battery’s discharge voltage gradually increases while the charging voltage decreases. The maximum P and EE values reach 104.13% and 104.11%, respectively, when the battery is charged under 0.2 C and worked when charging at 50 ℃ and discharging at 5 ℃ (Fig. 3 c,d). This is the first reported EE value above 100% for various batteries. Compared with the normal working mode, it can provide 13.26% extra electricity when the waste heat is collected and recovered (Fig. 3 e). Thus, the calculated η TTE / η C is 29.24%, which is superior to all the values for various harvesting waste heat technologies (see Fig. 1 b and Table 1 ). For example, it requires an average thermoelectric figure of merit ( ZT ) ave of 2 for thermoelectrics to compete this value, which is far larger than current best thermoelectric materials near room temperature. We also assemble a soft pack battery for performance test. It is charged at 48 ℃ in the daytime and at 5 ℃ in the basement at night (Fig. 3 f). At the same capacity, the charging voltage at 5 ℃ is 1.726 V but it is decreased to 1.517 V at 48 ℃ with a reduction of 12.11%. This further strongly suggests that harvesting waste heat can greatly improve battery’s performance. The high η TTE / η C can be understood from the point view of working principle of thermal engine. Firstly, all the four processes are nearly isothermal and thus there is no extra heat loss during working. Secondly, low working current density leads to the small Joule heat. Both of them are responsible for the observed high energy conversion efficiency. The LDH material plays an important role on battery’s performance. We conduct FTIR, Raman, in situ XRD and EDS measurements to investigate the variation of LDH material during charging and discharging processes. In situ XRD data (Fig. 4 a) shows the diffraction peak belonging to the Zn-LDH phase gradually appears at 32.8° during discharging, suggesting the generation of the LDH material. Extended Data Fig. 6b shows the Ni and S contents on the electrode surface gradually decrease during charging process, indicating that the LDH is gradually decomposed. The characteristic peaks of H 2 O, SO 4 2− , and M-OH in FTIR (Extended Data Fig. 6c) and Raman (Fig. 4 b) are also gradually strengthened when battery’s capacity is decreased, implying that the formation of LDH material. All the data indicate that the LDH material is obviously involved in battery’s working. It is gradually generated during discharging but decomposed during charging processes. The above data shows that the chemical reactions at anode contain Reaction S2 and Reaction 1. Thus, the temperature coefficient α − should also have the contributions from these two reactions, which can be given by a modified Nernst equation (see the details in supplementary section 3). The relationship between the total temperature coefficient of these two reactions ( α mix ) and Zn 2+ concentration is given by Eq. S16, which shows an opposite trend with the previous Nernst equation (Eq. S4). The Zn 2+ concentration not only influences the ionic entropy, but also affects the occurring proportion of Reaction S2 and Reaction 1. When Zn 2+ concentration is high, the α mix is dominated by Reaction S2; however, when Zn 2+ concentration is low, the α mix is dominated by Reaction 1 (Extended Data Fig. 6d). The experiment data can be well fitted by the modified Nernst equation (Eq. S16) (see Fig. 2 g). High α mix is expected when Zn 2+ concentration is small and/or the temperature coefficient of Reaction 1 is high. However, very small Zn 2+ concentration (< 0.05 mol/L) leads to large polarization and thus low P and EE . Therefore, the Zn 2+ concentration is chosen as 0.05 mol/L in this work to realize high performance NiHCF/Zn-LDH battery. The previous NiHCF/Zn battery has low cycling stability. After the first 20 cycles, the capacity is quickly decreased to 13.89%. However, the modified NiHCF/Zn-LDH battery has much better cycling stability because the LDH material can isolate water from Zinc electrodes. The galvanostatic charge/discharge (GCD) test at 1C shows that the battery has an attenuation rate of 1.93% after 650 cycles (Fig. 4 c). In addition, the reversible capacity in rate performance test can recover to 96.63% when the current switches back to 0.1 C from 3C (Extended Data Fig. 7h). Table 1 summarize the performance of various technologies for harvesting waste heat. TRB shows great advances as compared with the others, and thus is one of the most promising waste heat recovery technologies. In conclusion, we have successfully developed thermally regenerative Zn-ion battery to efficiently collect and recover the waste heat. The very high energy conversion efficiency and excellent battery’s performance indicate that harvesting waste heat by TRB is very powerful and useful. This strategy is expected to be extended to other batteries such as Li-ion, Na-ion, and K-ion batteries in the future. Materials And Methods Materials preparation NiHCF was synthesized from the high purity Ni(NO 3 ) 2 (99.99%, Aladdin) and K 3 Fe(CN) 6 (99.95%, Aladdin). 100 mL of 30 mM Ni(NO 3 ) 2 was added to 100 mL of 15 mM K 3 Fe(CN) 6 using a rate of one drop per second under strong stirring. The mixture solution was ultrasound for 30 min. The precipitation was centrifuged and washed with deionized water for three times. The product was dried in a vacuum at 40 ℃ for 12 hours. The NiHCF electrode slurry was prepared by mixing 70 wt% NiHCF, 20 wt% acetylene black and 10 wt% polyvinylidene fluoride (99.9%, Canrd) in N-methyl-2-pyrrolidone (99.9%, Jiuding chemistry) and then stirred for 2 hours. The obtained slurry was cast onto titanium mesh and dried at 70 ℃ in a vacuum oven. Zinc anode was prepared by pure zinc foil (99.995%, Zhongnuo New Material). The zinc foil was immersed in dilute hydrochloric acid (3vol%) to remove the oxide layer. Then it was sanded until the silvery-white color is observed on its surface. The electrolyte was prepared by dissolving KCF 3 SO 3 (99.22%, Bidepharm), Zn(CF 3 SO 3 ) 2 (99.9%, Bidepharm), and NiSO 4 (99.99%, Aladdin) in water. The specific concentrations were adjusted according to the experimental requirements. Materials characterization SEM and energy dispersive spectrometer (EDS) were performed on a JEOL/JSM-7610FPlus field-emission SEM instrument. XRD studies were performed on an Ultima IV X-ray diffractometer with Cu Kα radiation (40 kV, 40 mA, λ=1.5418 Å). X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha) was employed to probe the surface’s elemental information. Fourier Transform Infrared Spectroscopy (FTIR) was measured using a Thermo Nicolet Summit X instrument with the Attenuated Total Reflectance method. Raman characterization was performed by using a Raman spectrometer (inVia Reflex) with an excitation wavelength of 532 nm. Electrochemical measurements The measurements on temperature coefficient were carried out in a sealed electrolytic cell using a three-electrode configuration with Hg/Hg 2 Cl 2 as the reference electrode (RE). The voltage and temperature changes of the battery were monitored by the keysight B2901A (Keysight Technology Co., Ltd.). A precision thermostat Liyida LT-V6R5 (Suzhou Liyida Co., Ltd.) equipment was used to control battery’s temperature. The CV, GCD and EIS measurements were measured by the electrochemical workstation (DH7000C, Jiangsu Donghua Analytical Instruments Co. Ltd.). The CV test was investigated at a scanning rate of 0.1 mV/s within the voltage range of 1.0-2.0 V. The electrochemical EIS test was studied over the frequency range of 100 kHz to 10 mHz. NiHCF/Zn and NiHCF/Zn-LDH batteries were galvanostatically tested between 1.1 V and 1.9 V on a Neware CT-4008 testing system (Shenzhen NEWARE Electronics. Ltd., China) at various current densities. Declarations Data availability The raw/processed data required to reproduce these findings are available from the corresponding author on reasonable request. Code availability The codes that support the findings of this study are available from the corresponding authors upon reasonable request. Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant No. 52002406, U20A20247, 2022JJ20062, and 52232010). We are grateful to the High Performance Computing Center of Central South University for partial support of this work. Author contributions H. Chen, X. Shi and X. Sun designed the project. X. Sun, Y. Li and X. Ji prepared the samples and carried out the transport measurements. H. Chen performed the first-principles calculations. X. Shi and H. 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Infrared and Raman study of interlayer anions CO 3 2- , NO 3 - , SO 4 2- and ClO 4 - in Mg/Al-hydrotalcite[J]. Am. Mineral. 87 , 623-629 (2002). Nait-Merzoug, A. et al. Ni/Zn layered double hydroxide (LDH) micro/nanosystems and their azorubine adsorption performance[J]. Appl. Sci. 11 , 8899 (2021). Additional Declarations There is NO Competing Interest. Supplementary Files SuppInfo.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3679010","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":307223565,"identity":"b0a5dd59-cb25-4ef6-b44b-08d0174e68b0","order_by":0,"name":"Lidong Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyUlEQVRIiWNgGAWjYDACdgbDBwwMEjIMDIwNRGphZjA2AGrhIUmLmQSQ4iHeXfzNzNuqbtRY8DDwH278wFBjx8A/m4BtEofZym7nHAM6TCKxWYLhWDKDxJ0D+LUYMPOY3c5hA2lhbGNgYDvAYCCRQFhLcc4/oBb+g0At/4jUwpzbBgqxxDYGxjYitAD9Uiyd2yfBwwbyS2JfMo/EDQJa+NubN37O+VYnx89//OGHD9/s5PhnENACB2wgIoGkCBoFo2AUjIJRgBMAAJa/Mj+J3hXXAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-9683-037X","institution":"Shanghai Institute of Ceramics","correspondingAuthor":true,"prefix":"","firstName":"Lidong","middleName":"","lastName":"Chen","suffix":""},{"id":307223566,"identity":"13ca738d-5684-4e79-8fbb-64cbe6b1e59a","order_by":1,"name":"Xiaoling Sun","email":"","orcid":"","institution":"Central South University","correspondingAuthor":false,"prefix":"","firstName":"Xiaoling","middleName":"","lastName":"Sun","suffix":""},{"id":307223567,"identity":"c233330e-f18d-4f7b-a3db-663db3b82024","order_by":2,"name":"Hongyi Chen","email":"","orcid":"https://orcid.org/0000-0001-5529-2942","institution":"Central South University","correspondingAuthor":false,"prefix":"","firstName":"Hongyi","middleName":"","lastName":"Chen","suffix":""},{"id":307223568,"identity":"f3ca85e0-a1f1-4a1c-ae43-29642134b617","order_by":3,"name":"Yitong Li","email":"","orcid":"","institution":"Central South University","correspondingAuthor":false,"prefix":"","firstName":"Yitong","middleName":"","lastName":"Li","suffix":""},{"id":307223569,"identity":"044cbffe-1dc1-471c-9b47-c031446c355c","order_by":4,"name":"Dewen Zeng","email":"","orcid":"","institution":"Central South University","correspondingAuthor":false,"prefix":"","firstName":"Dewen","middleName":"","lastName":"Zeng","suffix":""},{"id":307223570,"identity":"c222f129-7dd8-4847-8e32-0bf09b1892c8","order_by":5,"name":"Pengfei Qiu","email":"","orcid":"https://orcid.org/0000-0001-6011-1210","institution":"Shanghai Institute of Ceramics","correspondingAuthor":false,"prefix":"","firstName":"Pengfei","middleName":"","lastName":"Qiu","suffix":""},{"id":307223571,"identity":"784c8b5b-0186-4237-86b2-bd4c8867b1fd","order_by":6,"name":"Huarong Zeng","email":"","orcid":"","institution":"Shanghai Institute of Ceramics","correspondingAuthor":false,"prefix":"","firstName":"Huarong","middleName":"","lastName":"Zeng","suffix":""},{"id":307223572,"identity":"d45ce89e-f4f4-4fe3-a04d-45803b5e8fda","order_by":7,"name":"Xiaobo Ji","email":"","orcid":"","institution":"Central South University","correspondingAuthor":false,"prefix":"","firstName":"Xiaobo","middleName":"","lastName":"Ji","suffix":""},{"id":307223573,"identity":"b4394034-08bc-4a5a-8ec8-bb3fccbb5520","order_by":8,"name":"Xun Shi","email":"","orcid":"https://orcid.org/0000-0002-8086-6407","institution":"Shanghai Institute of Ceramics","correspondingAuthor":false,"prefix":"","firstName":"Xun","middleName":"","lastName":"Shi","suffix":""}],"badges":[],"createdAt":"2023-11-29 01:55:47","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3679010/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3679010/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":57331839,"identity":"4c8ae8c1-7aeb-44a9-9b52-4f0818ad33b8","added_by":"auto","created_at":"2024-05-29 08:38:37","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":537398,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHarvesting waste heat by thermally regenerative Zn-ion battery.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, Schematic diagrams of NiHCF/Zn battery bank charged in the daytime (left picture), and discharged at night (right picture). the detailed schematic diagrams of NiHCF/Zn battery are shown in middle picture. \u003cstrong\u003eb\u003c/strong\u003e, \u003cem\u003eh\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e/\u003cem\u003eη\u003c/em\u003e\u003csub\u003eC\u003c/sub\u003e \u003cem\u003evs\u003c/em\u003e temperature difference. The low temperature is fixed at room temperature. \u003cem\u003eZT\u003c/em\u003e is the thermoelectric figure of merit. \u003cstrong\u003ec\u003c/strong\u003e, \u003cem\u003eEE\u003c/em\u003e \u003cem\u003evs\u003c/em\u003e \u003cem\u003eP\u003c/em\u003e. The stars represent the data in this work and the others are taken from Refs. 7, 9, 10, 15, 18, 20, 34, 35, 38-44. \u003cem\u003eP\u003c/em\u003e is the ratio of average discharge voltage to average charge voltage.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-3679010/v1/c983bc7b7b78a968e41e75c0.png"},{"id":57333003,"identity":"151eae5e-ab48-460a-9536-c489b04981ad","added_by":"auto","created_at":"2024-05-29 08:54:37","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":618220,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacterization and performance of Zn-LDH material.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, Electrochemical Stirling-like cycle. \u003cstrong\u003eb\u003c/strong\u003e, Crystal structure of Zn-LDH material. \u003cstrong\u003ec\u003c/strong\u003e, SEM image of Zn-LDH electrode. \u003cstrong\u003ed\u003c/strong\u003e,\u003cstrong\u003ee\u003c/strong\u003e, XRD patterns (\u003cstrong\u003ed\u003c/strong\u003e) and FTIR/Raman spectra (\u003cstrong\u003ee\u003c/strong\u003e) for Zn-LDH powders. \u003cstrong\u003ef\u003c/strong\u003e, \u003cem\u003eα\u003c/em\u003e\u003csub\u003e\u003cstrong\u003e+\u003c/strong\u003e\u003c/sub\u003e \u003cem\u003evs\u003c/em\u003e K\u003csup\u003e\u003cstrong\u003e+\u003c/strong\u003e\u003c/sup\u003e concentration. \u003cstrong\u003eg\u003c/strong\u003e, \u003cem\u003eα\u003c/em\u003e\u003csub\u003e\u003cem\u003e-\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e vs\u003c/em\u003e Zn\u003csup\u003e2\u003c/sup\u003e\u003csup\u003e\u003cstrong\u003e+\u003c/strong\u003e\u003c/sup\u003e concentration. \u003cstrong\u003eh\u003c/strong\u003e, Comparison of absolute \u003cem\u003eα \u003c/em\u003evalues for various electrochemical cells.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-3679010/v1/0400c37e83a6307f2c723f06.png"},{"id":57331838,"identity":"3a3db5b3-4bf6-40c8-b19b-6fbb1826b87f","added_by":"auto","created_at":"2024-05-29 08:38:37","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":501610,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePerformance of the NiHCF/Zn-LDH battery.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, Voltage \u003cem\u003evs \u003c/em\u003ecapacity for the battery worked under different temperature differences with a current densities of 0.2 C. The discharging temperature is fixed at 5 ℃. \u003cstrong\u003eb\u003c/strong\u003e, Voltage \u003cem\u003evs \u003c/em\u003ecapacity for the battery charged at 50 ℃ and discharged at 5 ℃ under various current densities. The solid lines in (\u003cstrong\u003ea\u003c/strong\u003e) and (\u003cstrong\u003eb\u003c/strong\u003e) represent charging curves and the dotted lines represent discharging curves. \u003cstrong\u003ec\u003c/strong\u003e,\u003cstrong\u003ed\u003c/strong\u003e, \u003cem\u003eP\u003c/em\u003e and \u003cem\u003eEE\u003c/em\u003e \u003cem\u003evs\u003c/em\u003e \u003cem\u003eΔT\u003c/em\u003e (\u003cstrong\u003ec\u003c/strong\u003e) and current densities (\u003cstrong\u003ed\u003c/strong\u003e). \u003cstrong\u003ee\u003c/strong\u003e, Battery’s performance when it is discharged at 5 ℃ but charged at 5 ℃ and 50 ℃. The current density is 0.2 C. \u003cstrong\u003ef\u003c/strong\u003e, Charging voltages of the soft pack battery at 5 ℃ and 48℃.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-3679010/v1/a78af002abddccabc8f123b8.png"},{"id":57331840,"identity":"bb408278-653c-41db-ae9f-67c465780279","added_by":"auto","created_at":"2024-05-29 08:38:37","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":338199,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eIn-situ characterization of LDH material during working and battery’s cycling performance.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, In situ XRD contour map for Zn-LDH material collected within 1.1-1.9 V during charging and discharging processes. \u003cstrong\u003eb\u003c/strong\u003e, Variation of characteristic peaks for the Zn-LDH material by Raman spectra. \u003cstrong\u003ec\u003c/strong\u003e, Cycling performance of NiHCF/Zn and NiHCF/Zn-LDH batteries at 1C.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-3679010/v1/00ec4b54d1b11a6847315093.png"},{"id":58525372,"identity":"8c17b516-4d41-41f2-9bd7-5319e3d22ba0","added_by":"auto","created_at":"2024-06-17 20:33:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2695944,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3679010/v1/a3aa8619-fc98-44f6-abb9-a91f0559c4ae.pdf"},{"id":57332617,"identity":"080a8099-3fb2-41d9-a37d-9673f76f9b4a","added_by":"auto","created_at":"2024-05-29 08:46:37","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":7899406,"visible":true,"origin":"","legend":"","description":"","filename":"SuppInfo.docx","url":"https://assets-eu.researchsquare.com/files/rs-3679010/v1/e7346506a32ceefe81cbf369.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Extraordinarily harvesting waste heat by thermally regenerative Zn-ion battery","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMore than 50% of global energy ends up as waste heat, including all manner of human activities, natural systems, and all organisms. Among various technologies for waste heat recovery, thermoelectrics have a simple working structure with the advantages of quiet, reliable, and long service life, but they have small open voltages and low energy conversion efficiency because their working substance is electrons or holes\u003csup\u003e1\u0026ndash;5\u003c/sup\u003e. Thermionic capacitors\u003csup\u003e6\u0026ndash;8\u003c/sup\u003e and thermo-cells\u003csup\u003e9\u0026ndash;11\u003c/sup\u003e based on ion diffusion and/or reactions have the advantages of large open voltages, but the generated electricity is intermittent and working modes are usually very complicated. Combining the technology of thermo-cells and regular batteries leads to the discovery of thermal charging cells. It has the advantage of a relatively high average output voltage (0-0.5 V) as compared with thermos-cells, but a large temperature difference between anode and cathode is required that is hardly realized in practical batteries\u003csup\u003e12\u0026ndash;14\u003c/sup\u003e. All the above technologies work under a certain temperature gradient, which is far beyond the equilibrium state. Thus, many of the heat energy is dissipated into the environment and the thermal-to-electrical energy conversion efficiency (\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e) is low (usually less than 12% of the Carnot efficiency \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eC\u003c/sub\u003e under a temperature difference of 50 ℃). In addition, the measured output voltage in thermo-cells and thermal charging cells contains the contributions from ion diffusion, interface polarization, and the voltage temperature coefficient of battery. The former two terms are one-off, leading to the rapid decay in the output voltage during working. The term of battery\u0026rsquo;s voltage temperature coefficient can provide a stable and continuous electric output, but the absolute value is very small (usually less than 10% of the output voltage) that has not been accurately measured yet.\u003c/p\u003e\n\u003cp\u003eCarnot-like cycle is a near equilibrium process. Thus, the \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e can be very high because the heat energy dissipated into the environment is extremely small. Thermally regenerative electrochemical cycle (TREC) is a typical Carnot-like (Stirling-like electrical) cycle. During working, the system is charged at high temperature, and then naturally cooled to low temperature and finally discharged at this temperature. If the temperature coefficient of system\u0026rsquo;s voltage (\u003cem\u003e\u0026alpha;\u003c/em\u003e) is negative, the absorbed heat at high temperature can be converted to electricity at low temperature and finally released along with the charged electricity. An absolute larger \u003cem\u003e\u0026alpha;\u003c/em\u003e value leads to a higher \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e. Currently, the |\u003cem\u003e\u0026alpha;|\u003c/em\u003e in TREC is in the range of 0.74\u0026ndash;2.27 mV/K and relative Carnot efficiency (\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e/\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eC\u003c/sub\u003e) is in the range of 5.6\u0026ndash;25%\u003csup\u003e15\u0026ndash;25\u003c/sup\u003e. However, these electrochemical cells usually have small working voltages (\u0026lt;\u0026thinsp;0.8 V) and/or poor cycling stability (10\u0026ndash;160 cycles at 5% capacity attenuation), which greatly impede their wide applications in energy conversion and storage. In contrast, regular batteries have the advantages of large working voltage (1.4\u0026ndash;3.8 V), good cycling stability (400\u0026ndash;3000 cycles), fast response speed, and portability\u003csup\u003e26\u0026ndash;31\u003c/sup\u003e as well as extremely high energy conversion efficiency between chemical energy and electricity\u003csup\u003e32\u0026ndash;35\u003c/sup\u003e. Using regular batteries to harvest waste heat under Carnot-like mode can realize a novel and efficient thermally regenerative battery (TRB) technology, but it has not been realized until today because of the low (0.05\u0026ndash;1.46 mV/K) \u003csup\u003e25,36,37\u003c/sup\u003e or the absence of battery\u0026rsquo;s temperature coefficient.\u003c/p\u003e\n\u003cp\u003eHerein, we successfully developed a thermally regenerative Zn-ion battery to work under Carnot-like mode to extraordinarily harvest waste heat (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea). By introducing a Layered Double Hydroxides (LDH) into the anode reaction, extremely high battery\u0026rsquo;s temperature coefficient of 2.944 mV/K and \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e/\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eC\u003c/sub\u003e of 29.24% (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eb and Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), and extraordinary charge-discharge Energy Efficiency (\u003cem\u003eEE\u003c/em\u003e) of 104.11% (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ec) with a large working voltage (1.49 V) and good cycling stability (up to 650 cycles with a capacity attenuation of 1.93%) are realized when the battery is charged at 50 ℃ and then naturally cooled to 5 ℃ for discharge. This study suggests that TRB is one of the most promising technologies for harvesting waste heat (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), which can effectively collect extra electricity in the daytime and then efficiently provide more than 100% of the charged electricity to users such as electric vehicles at night (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea).\u003c/p\u003e\n\u003cp\u003eThe structure of NiHCF/Zn battery is shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea. Nickel hexacyanoferrate (KNi\u003csup\u003eII\u003c/sup\u003eFe\u003csup\u003eIII\u003c/sup\u003e(CN)\u003csub\u003e6\u003c/sub\u003e, NiHCF) is taken as cathode, zinc is taken as anode, and KCF\u003csub\u003e3\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e and Zn(CF\u003csub\u003e3\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e are taken as the mixed electrolyte. The chemical reactions of two half cells are shown in Reaction S1 and S2. In order to realize a Carnot-like mode, a Stirling-like electrical cycle is built. It contains four steps (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea). For the first step, the battery is heated to a high temperature with the open circuit voltage (OCV) decreasing to \u003cem\u003eV\u003c/em\u003e(\u003cem\u003eT\u003c/em\u003e\u003csub\u003eH\u003c/sub\u003e). For the second step, the battery is charged at this high temperature with the heat energy and electricity stored as chemical energy. For the third step, the battery is cooled to a low temperature with the OCV increased to \u003cem\u003eV\u003c/em\u003e(\u003cem\u003eT\u003c/em\u003e\u003csub\u003eL\u003c/sub\u003e). During this step, part of the absorbed heat is converted to chemical energy. For the fourth step, the battery is discharged at this low temperature with all the stored chemical energy released.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1 | Summary of various technologies for harvesting waste heat.\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"629\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.85987261146497%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.509554140127388%\"\u003e\n \u003cp\u003e\u003cstrong\u003eThermo-electrics\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.375796178343949%\"\u003e\n \u003cp\u003e\u003cstrong\u003eThermionic capacitors\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003e\u003cstrong\u003eThermo-cells\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003e\u003cstrong\u003eThermal charge cells\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.401273885350317%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTREC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.968152866242038%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTRB\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.85987261146497%\"\u003e\n \u003cp\u003eTemperature gradient across the device\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.509554140127388%\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.375796178343949%\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.401273885350317%\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.968152866242038%\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.85987261146497%\"\u003e\n \u003cp\u003eworking under equilibrium state\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.509554140127388%\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.375796178343949%\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.401273885350317%\"\u003e\n \u003cp\u003eNear\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.968152866242038%\"\u003e\n \u003cp\u003eNear\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.85987261146497%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e/\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eC\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.509554140127388%\"\u003e\n \u003cp\u003e5-16%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.375796178343949%\"\u003e\n \u003cp\u003e0.03-8.46%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003e0.01-12%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003e5.2-7.25%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.401273885350317%\"\u003e\n \u003cp\u003e5.6-25%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.968152866242038%\"\u003e\n \u003cp\u003e29.24%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.85987261146497%\"\u003e\n \u003cp\u003eOutput voltage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.509554140127388%\"\u003e\n \u003cp\u003eStable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.375796178343949%\"\u003e\n \u003cp\u003eUnstable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003eUnstable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003eUnstable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.401273885350317%\"\u003e\n \u003cp\u003eStable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.968152866242038%\"\u003e\n \u003cp\u003eStable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.85987261146497%\"\u003e\n \u003cp\u003eOutput voltage for single-pair device\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.509554140127388%\"\u003e\n \u003cp\u003e0-0.1V\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.375796178343949%\"\u003e\n \u003cp\u003e0-0.03V\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003e0-0.1V\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003e0-0.5V\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.401273885350317%\"\u003e\n \u003cp\u003e0.21-0.81V\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.968152866242038%\"\u003e\n \u003cp\u003e1.49V\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.85987261146497%\"\u003e\n \u003cp\u003eWorking lifetime\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.509554140127388%\"\u003e\n \u003cp\u003e\u0026gt; several years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.375796178343949%\"\u003e\n \u003cp\u003e15-1000\u0026nbsp;cycles at 6% capacity attenuation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003e\u0026gt;100 hours\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003e50-100 cycles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.401273885350317%\"\u003e\n \u003cp\u003e10~160\u0026nbsp;cycles at 5% capacity attenuation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.968152866242038%\"\u003e\n \u003cp\u003e650 cycles at 1.93% capacity attenuation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.85987261146497%\"\u003e\n \u003cp\u003eextra heat exchange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.509554140127388%\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.375796178343949%\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.94267515923567%\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.401273885350317%\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.968152866242038%\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eBattery\u0026rsquo;s temperature coefficient of voltage (\u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003ecell\u003c/sub\u003e) directly determines how much heat energy can be converted to chemical energy during the electrochemical Stirling-like cycle. It contains the contributions from the reactions at anode (\u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e+\u003c/sub\u003e) and cathode (\u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u0026minus;\u003c/sub\u003e). Thus, the \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003ecell\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;\u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e+\u003c/sub\u003e-\u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u0026minus;\u003c/sub\u003e, where the \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e+\u003c/sub\u003e and \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u0026minus;\u003c/sub\u003e can be given by the Nernst equation (Eqs. (S3 and S4)). The battery\u0026rsquo;s temperature coefficient of voltage is carefully measured. Both the \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u003cem\u003e+\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026minus;\u003c/em\u003e\u003c/sub\u003e increase when increasing K\u003csup\u003e+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e concentrations, which can be well described by the Nernst equation (see Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ef,g). The minimum \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e+\u003c/sub\u003e (-0.826 mV/K) and maximum \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u0026minus;\u003c/sub\u003e (0.692 mV/K) are obtained when the K\u003csup\u003e+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e concentrations are 0.2 mol/L and 1.0 mol/L, respectively. However, the battery is unstable and has larger polarization when K\u003csup\u003e+\u003c/sup\u003e concentration is lower than 0.5 mol/L. Therefore, the NiHCF/Zn battery is assembled using the K\u003csup\u003e+\u003c/sup\u003e concentration of 0.5 mol/L and Zn\u003csup\u003e2+\u003c/sup\u003e concentration of 1.0 mol/L, leading to a total \u003cem\u003e\u0026alpha;\u003c/em\u003e of -1.221 mV/K. We further test the battery\u0026rsquo;s performance. A \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e/\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eC\u003c/sub\u003e of 14.60% is obtained when the battery is charged at 50 ℃ and then discharged at 5 ℃, resulting in an \u003cem\u003eEE\u003c/em\u003e of 95.05% as compared with the value of 92.01% when the battery is charged and discharged at 5 ℃.\u003c/p\u003e\n\u003cp\u003eBattery\u0026rsquo;s temperature coefficient is determined by its entropy (\u003cem\u003e\u0026Delta;S\u003c/em\u003e), which can be significantly changed by modifying ion\u0026rsquo;s types and concentrations (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varDelta S\\stackrel{\\scriptscriptstyle\\text{def}}{=}-{k}_{B}\\text{ln}\\left(\\right[x\\left]\\right)\\)\u003c/span\u003e\u003c/span\u003e) \u003csup\u003e20\u003c/sup\u003e, where \u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003eB\u003c/em\u003e\u003c/sub\u003e is the Boltzmann constant and \u003cem\u003ex\u003c/em\u003e is the effective concentration of ions. Here, by adding 0.05 mol/L of NiSO\u003csub\u003e4\u003c/sub\u003e into the electrolyte, an extra chemical reaction occurs at the surface of Zn/Zn\u003csup\u003e2+\u003c/sup\u003e electrode\u003c/p\u003e\n\u003cp\u003eZn-2e\u0026thinsp;+\u0026thinsp;\u003cem\u003ex\u003c/em\u003eNi\u003csup\u003e2+\u003c/sup\u003e+\u003cem\u003ey\u003c/em\u003eSO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e+\u003cem\u003ez\u003c/em\u003eOH\u003csup\u003e\u0026minus;\u003c/sup\u003e+\u003cem\u003ew\u003c/em\u003eH\u003csub\u003e2\u003c/sub\u003eO \u0026harr; ZnNi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e(OH)\u003csub\u003e\u003cem\u003ez\u003c/em\u003e\u003c/sub\u003e\u0026middot;\u003cem\u003ew\u003c/em\u003eH\u003csub\u003e2\u003c/sub\u003eO (\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e\n\u003cp\u003eZnNi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e(OH)\u003csub\u003e\u003cem\u003ez\u003c/em\u003e\u003c/sub\u003e\u0026middot;\u003cem\u003ew\u003c/em\u003eH\u003csub\u003e2\u003c/sub\u003eO has a typical Layered Double Hydroxides (LDH) structure (shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb). It has two layers. One layer is ZnNi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e(OH)\u003csub\u003e\u003cem\u003ez\u003c/em\u003e\u003c/sub\u003e, and another is ZnSO\u003csub\u003e4\u003c/sub\u003e and water. Strong hydrogen bonds are existed between these layers. Except Zn\u003csup\u003e2+\u003c/sup\u003e, the LDH material contains Ni\u003csup\u003e2+\u003c/sup\u003e and SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, which may give additional contributions to battery\u0026rsquo;s temperature coefficient.\u003c/p\u003e\n\u003cp\u003eThe LDH material on anode\u0026rsquo;s surface is characterized and confirmed by various techniques. Scanning electron microscope (SEM) measurements show that numerous nanoscale flakes are observed (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec and Extended Data Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea), which are consistent with the character of layered structure in LDH\u003csup\u003e45,46\u003c/sup\u003e. Energy Dispersive Spectrometer (EDS) mapping revealed the uniform distribution of Zn, Ni, O, and S elements from 100 nm to 10 \u0026micro;m and the molar ratio of Ni: S close to 1: 1 (Extended Data Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea). The X-Ray Diffractometer (XRD) pattern matches well with that of Zn\u003csub\u003e3.52\u003c/sub\u003eNi\u003csub\u003e1.63\u003c/sub\u003e(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e1.33\u003c/sub\u003e(OH)\u003csub\u003e7.64\u003c/sub\u003e\u0026middot;4.67H\u003csub\u003e2\u003c/sub\u003eO (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ed) \u003csup\u003e47\u003c/sup\u003e. Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectra (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ee) show that the absorption peaks locate at 400\u0026ndash;800 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 964 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 1635 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which are also consistent with the characteristic vibration peaks of Zn/Ni-OH, SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e and H\u003csub\u003e2\u003c/sub\u003eO in LDH materials\u003csup\u003e48\u0026ndash;50\u003c/sup\u003e, respectively.\u003c/p\u003e\n\u003cp\u003eCompared with the pristine battery, the \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e+\u003c/sub\u003e in the modified battery is slightly decreased to about 0.02 mV/K. It still increases with the increase of K\u003csup\u003e+\u003c/sup\u003e concentration, consistent with the Nernst equation (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ef). However, the \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026minus;\u003c/em\u003e\u003c/sub\u003e in the modified battery is greatly different from the previous one (see Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eg). It is increased to 2.120 mV/K, 3.18 times of the pristine one, when the Zn\u003csup\u003e2+\u003c/sup\u003e concentration is 0.05 mol/L and K\u003csup\u003e+\u003c/sup\u003e concentration is 0.5 mol/L. Furthermore, the \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u0026minus;\u003c/sub\u003e decreases when increasing Zn\u003csup\u003e2+\u003c/sup\u003e concentration, which is completely different from the Nernst equation.\u003c/p\u003e\n\u003cp\u003eThe temperature coefficient of the full NiHCF/Zn-LDH battery is measured at 50% state of charge (SOC). The battery has accurate and rapid response to temperature (Extended Data Fig. 5b). The potentials show linear changes to temperature (Extended Data Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ed) and the slope is the temperature coefficient. It is -0.827 mV/K and 2.116 mV/K for the reactions at the cathode and anode, respectively. Ultimately, the NiHCF/Zn-LDH battery has a very high absolute \u003cem\u003e\u0026alpha;\u003c/em\u003e of 2.944 mV/K, superior to all the reported electrochemical cells near room temperature (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eh).\u003c/p\u003e\n\u003cp\u003eWe simulate the Stirling-like cycle for NiHCF/Zn-LDH battery with the data shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea,b. A charging and discharging range of 15\u0026ndash;85% SOC is chosen. First, the battery is charged at various high temperatures but discharged at 5 ℃ under a current density of 11.2 mA\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (0.2 C). Although the charging temperature is different, the difference in discharge voltage is small with the error bar less than 1.85%, indicating that battery\u0026rsquo;s discharging performance is rarely affected. However, the charging voltages are significantly reduced when increasing charging temperature. Specifically, we test the battery via charging at 50 ℃ and discharging at 5 ℃ under different current densities. When the current density increases, battery\u0026rsquo;s discharge voltage gradually increases while the charging voltage decreases.\u003c/p\u003e\n\u003cp\u003eThe maximum \u003cem\u003eP\u003c/em\u003e and \u003cem\u003eEE\u003c/em\u003e values reach 104.13% and 104.11%, respectively, when the battery is charged under 0.2 C and worked when charging at 50 ℃ and discharging at 5 ℃ (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ec,d). This is the first reported \u003cem\u003eEE\u003c/em\u003e value above 100% for various batteries. Compared with the normal working mode, it can provide 13.26% extra electricity when the waste heat is collected and recovered (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ee). Thus, the calculated \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e/\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eC\u003c/sub\u003e is 29.24%, which is superior to all the values for various harvesting waste heat technologies (see Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eb and Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). For example, it requires an average thermoelectric figure of merit (\u003cem\u003eZT\u003c/em\u003e)\u003csub\u003eave\u003c/sub\u003e of 2 for thermoelectrics to compete this value, which is far larger than current best thermoelectric materials near room temperature. We also assemble a soft pack battery for performance test. It is charged at 48 ℃ in the daytime and at 5 ℃ in the basement at night (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ef). At the same capacity, the charging voltage at 5 ℃ is 1.726 V but it is decreased to 1.517 V at 48 ℃ with a reduction of 12.11%. This further strongly suggests that harvesting waste heat can greatly improve battery\u0026rsquo;s performance. The high \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eTTE\u003c/sub\u003e/\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003eC\u003c/sub\u003e can be understood from the point view of working principle of thermal engine. Firstly, all the four processes are nearly isothermal and thus there is no extra heat loss during working. Secondly, low working current density leads to the small Joule heat. Both of them are responsible for the observed high energy conversion efficiency.\u003c/p\u003e\n\u003cp\u003eThe LDH material plays an important role on battery\u0026rsquo;s performance. We conduct FTIR, Raman, in situ XRD and EDS measurements to investigate the variation of LDH material during charging and discharging processes. In situ XRD data (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea) shows the diffraction peak belonging to the Zn-LDH phase gradually appears at 32.8\u0026deg; during discharging, suggesting the generation of the LDH material. Extended Data Fig.\u0026nbsp;6b shows the Ni and S contents on the electrode surface gradually decrease during charging process, indicating that the LDH is gradually decomposed. The characteristic peaks of H\u003csub\u003e2\u003c/sub\u003eO, SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, and M-OH in FTIR (Extended Data Fig. 6c) and Raman (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eb) are also gradually strengthened when battery\u0026rsquo;s capacity is decreased, implying that the formation of LDH material. All the data indicate that the LDH material is obviously involved in battery\u0026rsquo;s working. It is gradually generated during discharging but decomposed during charging processes.\u003c/p\u003e\n\u003cp\u003eThe above data shows that the chemical reactions at anode contain Reaction S2 and Reaction 1. Thus, the temperature coefficient \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026minus;\u003c/em\u003e\u003c/sub\u003e should also have the contributions from these two reactions, which can be given by a modified Nernst equation (see the details in supplementary section 3). The relationship between the total temperature coefficient of these two reactions (\u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003e\u003cem\u003emix\u003c/em\u003e\u003c/sub\u003e) and Zn\u003csup\u003e2+\u003c/sup\u003e concentration is given by Eq. S16, which shows an opposite trend with the previous Nernst equation (Eq. S4). The Zn\u003csup\u003e2+\u003c/sup\u003e concentration not only influences the ionic entropy, but also affects the occurring proportion of Reaction S2 and Reaction 1. When Zn\u003csup\u003e2+\u003c/sup\u003e concentration is high, the \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003emix\u003c/sub\u003e is dominated by Reaction S2; however, when Zn\u003csup\u003e2+\u003c/sup\u003e concentration is low, the \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003emix\u003c/sub\u003e is dominated by Reaction 1 (Extended Data Fig. 6d). The experiment data can be well fitted by the modified Nernst equation (Eq. S16) (see Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eg). High \u003cem\u003e\u0026alpha;\u003c/em\u003e\u003csub\u003emix\u003c/sub\u003e is expected when Zn\u003csup\u003e2+\u003c/sup\u003econcentration is small and/or the temperature coefficient of Reaction 1 is high. However, very small Zn\u003csup\u003e2+\u003c/sup\u003e concentration (\u0026lt;\u0026thinsp;0.05 mol/L) leads to large polarization and thus low \u003cem\u003eP\u003c/em\u003e and \u003cem\u003eEE\u003c/em\u003e. Therefore, the Zn\u003csup\u003e2+\u003c/sup\u003e concentration is chosen as 0.05 mol/L in this work to realize high performance NiHCF/Zn-LDH battery.\u003c/p\u003e\n\u003cp\u003eThe previous NiHCF/Zn battery has low cycling stability. After the first 20 cycles, the capacity is quickly decreased to 13.89%. However, the modified NiHCF/Zn-LDH battery has much better cycling stability because the LDH material can isolate water from Zinc electrodes. The galvanostatic charge/discharge (GCD) test at 1C shows that the battery has an attenuation rate of 1.93% after 650 cycles (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec). In addition, the reversible capacity in rate performance test can recover to 96.63% when the current switches back to 0.1 C from 3C (Extended Data Fig. 7h). Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e summarize the performance of various technologies for harvesting waste heat. TRB shows great advances as compared with the others, and thus is one of the most promising waste heat recovery technologies.\u003c/p\u003e\n\u003cp\u003eIn conclusion, we have successfully developed thermally regenerative Zn-ion battery to efficiently collect and recover the waste heat. The very high energy conversion efficiency and excellent battery\u0026rsquo;s performance indicate that harvesting waste heat by TRB is very powerful and useful. This strategy is expected to be extended to other batteries such as Li-ion, Na-ion, and K-ion batteries in the future.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003ch2\u003eMaterials preparation\u003c/h2\u003e\n\u003cp\u003eNiHCF was synthesized from the high purity\u0026nbsp;Ni(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (99.99%, Aladdin) and K\u003csub\u003e3\u003c/sub\u003eFe(CN)\u003csub\u003e6\u003c/sub\u003e (99.95%, Aladdin). 100 mL of 30 mM Ni(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u0026nbsp;\u003c/sub\u003ewas added to 100 mL of 15 mM K\u003csub\u003e3\u003c/sub\u003eFe(CN)\u003csub\u003e6\u003c/sub\u003e using a rate of one drop per second under strong stirring. The mixture solution was ultrasound for 30 min. The precipitation was centrifuged and washed with deionized water for three times. The product was dried in a vacuum at 40 ℃ for 12 hours. The NiHCF electrode slurry was prepared by mixing 70 wt% NiHCF, 20 wt% acetylene black and 10 wt% polyvinylidene fluoride (99.9%, Canrd) in N-methyl-2-pyrrolidone (99.9%, Jiuding chemistry) and then stirred for 2 hours. The obtained slurry was cast onto titanium mesh and dried at 70 ℃ in a vacuum oven. Zinc anode was prepared by pure zinc foil (99.995%, Zhongnuo New Material). The zinc foil was immersed in dilute hydrochloric acid (3vol%) to remove the oxide layer. Then it was sanded until the silvery-white color is observed on its surface. The electrolyte was prepared by dissolving KCF\u003csub\u003e3\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e (99.22%, Bidepharm), Zn(CF\u003csub\u003e3\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (99.9%, Bidepharm), and NiSO\u003csub\u003e4\u003c/sub\u003e (99.99%, Aladdin) in water. The specific concentrations were adjusted according to the experimental requirements.\u003c/p\u003e\n\u003ch2\u003eMaterials characterization\u003c/h2\u003e\n\u003cp\u003eSEM and energy dispersive spectrometer (EDS) were performed on a JEOL/JSM-7610FPlus field-emission SEM instrument. XRD studies were performed on an Ultima IV X-ray diffractometer with Cu K\u0026alpha; radiation (40 kV, 40 mA, \u0026lambda;=1.5418 \u0026Aring;). X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha) was employed to probe the surface\u0026rsquo;s elemental information. Fourier Transform Infrared Spectroscopy (FTIR) was measured using a Thermo Nicolet Summit X instrument with the Attenuated Total Reflectance method. Raman characterization was performed by using a Raman spectrometer (inVia Reflex) with an excitation wavelength of 532 nm.\u003c/p\u003e\n\u003ch2\u003eElectrochemical measurements\u003c/h2\u003e\n\u003cp\u003eThe\u0026nbsp;measurements on\u0026nbsp;temperature coefficient\u0026nbsp;were carried out in a sealed electrolytic cell using a three-electrode configuration with Hg/Hg\u003csub\u003e2\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e as the reference electrode (RE). The voltage and temperature changes of the battery were monitored by the keysight B2901A (Keysight Technology Co., Ltd.). A precision thermostat Liyida LT-V6R5 (Suzhou Liyida Co., Ltd.) equipment was used to control battery\u0026rsquo;s temperature. The CV, GCD and EIS measurements were measured by the electrochemical workstation (DH7000C, Jiangsu Donghua Analytical Instruments Co. Ltd.). The CV test was investigated at a scanning rate of 0.1 mV/s within the voltage range of 1.0-2.0 V. The electrochemical EIS test was studied over the frequency range of 100 kHz to 10 mHz. NiHCF/Zn and NiHCF/Zn-LDH batteries were galvanostatically tested between 1.1 V and 1.9 V on a Neware CT-4008 testing system (Shenzhen NEWARE Electronics. Ltd., China) at various current densities. \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe raw/processed data required to reproduce these findings are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCode availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe codes that support the findings of this study are available from the corresponding authors upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (Grant No. 52002406, U20A20247, 2022JJ20062, and 52232010). We are grateful to the High Performance Computing Center of Central South University for partial support of this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eH. Chen, X. Shi and X. Sun designed the project. X. Sun, Y. Li and X. Ji prepared the samples and carried out the transport measurements. H. Chen performed the first-principles calculations. X. Shi and H. Chen constructed the theoretical framework. H. Chen, X. Sun, D. Zeng, D. Zhen, H. Zeng, P. Qiu, and X. Shi analyzed the data. H. Chen, X. Sun, and X. Shi wrote the original manuscript. X. Shi, X. Ji and L. Chen supervised the project. All the authors reviewed and edited the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe raw/processed data required to reproduce these findings are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary information\u003c/strong\u003e The online version contains supplementary material available at https://doi.org xx.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSnyder, G. J. \u0026amp; Toberer, E. S. Complex thermoelectric materials[J]. \u003cem\u003eNat. 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They have small thermal-to-electrical conversion efficiency or poor stability, severely hindering the efficient recovery of waste heat. Herein, we successfully developed a thermally regenerative Zn-ion battery to work under Carnot-like mode to efficiently harvest waste heat into electricity. Through introducing Layered Double Hydroxides to modify battery’s anode reaction, a record absolute high temperature coefficient of 2.944 mV/K is achieved in NiHCF/Zn battery, leading to a high thermal-to-electrical conversion efficiency of 29.24% of the Carnot efficiency and an extraordinary energy efficiency of 104.11% when the battery is charged at 50 ℃ and discharged at 5 ℃. This work demonstrates that the thermally regenerative batteries can effectively harvest waste heat to provide a powerful energy conversion technology.","manuscriptTitle":"Extraordinarily harvesting waste heat by thermally regenerative Zn-ion battery","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-29 08:38:32","doi":"10.21203/rs.3.rs-3679010/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"76439461-0339-40f8-a061-50cb29b46804","owner":[],"postedDate":"May 29th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":32448855,"name":"Physical sciences/Materials science/Materials for energy and catalysis/Batteries"},{"id":32448856,"name":"Physical sciences/Energy science and technology/Energy storage/Batteries"}],"tags":[],"updatedAt":"2024-06-17T20:25:14+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-29 08:38:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3679010","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3679010","identity":"rs-3679010","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}