Silicon-Enriched Biomass-Derived Hard Carbon for High-Capacity Lithium-ion Battery Anodes

Silicon-Enriched Biomass-Derived Hard Carbon for High-Capacity Lithium-ion Battery Anodes | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 27 August 2025 V1 Latest version Share on Silicon-Enriched Biomass-Derived Hard Carbon for High-Capacity Lithium-ion Battery Anodes Authors : Alireza Fereydooni , Chenghao Yue , Puritut Nakhanivej , Maria Murria , Mingrui Liu , Yuexi Zeng , Zhijie Wei , Qiuju Fu , Xuebo Zhao , Melanie Loveridge , and Yimin Chao 0000-0002-8488-2690 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.175631047.70071802/v1 567 views 261 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Silicon-enriched hard carbon derived from barley husks is investigated as a high-performance anode material for lithium-ion batteries (LIBs). By systematically incorporating silica into the carbon matrix at different ratios, the resulting composite anodes exhibit a significant enhancement in specific capacity, achieving up to ”1382 mAh ” ”g” ^”-1” at C/5, far exceeding commercial graphite, which has a capacity of ”372 mAh ” ”g” ^”-1” . The synergistic interaction between silica and carbon effectively mitigates the particle disintergration originated from volume expansion of SiO₂, ensuring improved cycling stability and rate performance. A full cell was assembled using NMC622 as the cathode, delivering an energy density of ”385 Wh k” ”g” ^”-1” at C/10 and maintaining 89% capacity retention after 100 cycles, surpassing conventional graphite-based cells. The anode fabrication follows a straightforward, scalable approach, relying on simple carbonization and mechanical mixing without requiring complex synthesis steps, making it suitable for large-scale production. Comparative electrochemical analysis reveals that the prepared anodes outperform graphite in terms of both specific capacity and rate capability, making them a viable, sustainable alternative for next-generation LIB anodes. Article category: Full Paper Subcategory: Lithium Ion Batteries Silicon-Enriched Biomass-Derived Hard Carbon for High-Capacity Lithium-ion Battery Anodes Alireza Fereydooni a,b,c† , Chenghao Yue a,b† , Puritut Nakhanivej d , Maria Balart Murria d , Mingrui Liu a , Yuexi Zeng a , Zhijie Wei a , Qiuju Fu e , Xuebo Zhao e , Melanie Loveridge d , and Yimin Chao a,b * a National energy key laboratory for new hydrogen-ammonia energy technologies, Foshan Xianhu Laboratory, Foshan 528200, P. R. China. b School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK. c Tyndall Center for Climate Change Research, University of East Anglia, Norwich NR4 7TJ, UK. d Warwick Manufacturing Group (WMG), University of Warwick, Coventry CV4 7AL, UK. e Shandong Provincial Key Laboratory of Chemistry Energy Storage and Novel Cell Technology, School of Materials Science and Engineering, Qilu University of Technology (Shandong Academy of Science), Jinan 250353, China. † These authors contributed equally to this work. * Corresponding author’s E-mail address: [email protected] Keywords: anode materials, lithium-ion batteries, silicon, barley husks, sustainability Asbstract Silicon-enriched hard carbon derived from barley husks is investigated as a high-performance anode material for lithium-ion batteries (LIBs). By systematically incorporating silica into the carbon matrix at different ratios, the resulting composite anodes exhibit a significant enhancement in specific capacity, achieving up to\(\text{1382}\text{\ }\text{mAh}\text{\ }\text{g}^{\text{-1}}\) at C/5, far exceeding commercial graphite, which has a capacity of\(\text{372}\text{\ }\text{mAh}\text{\ }\text{g}^{\text{-1}}\). The synergistic interaction between silica and carbon effectively mitigates the particle disintergration originated from volume expansion of SiO₂, ensuring improved cycling stability and rate performance. A full cell was assembled using NMC622 as the cathode, delivering an energy density of \(\text{385\ Wh\ k}\text{g}^{\text{-1}}\) at C/10 and maintaining 89% capacity retention after 100 cycles, surpassing conventional graphite-based cells. The anode fabrication follows a straightforward, scalable approach, relying on simple carbonization and mechanical mixing without requiring complex synthesis steps, making it suitable for large-scale production. Comparative electrochemical analysis reveals that the prepared anodes outperform graphite in terms of both specific capacity and rate capability, making them a viable, sustainable alternative for next-generation LIB anodes. 1. Introduction The growing demand for lithium-ion batteries (LIBs) in electric vehicles, portable electronics, and grid-scale storage systems continues to drive the search for anode materials that combine high energy density with long-term cycling stability. [1, 2] Currently, graphite is the most widely used commercial anode due to its excellent structural reversibility and moderate lithiation potential. [3, 4] However, its relatively low theoretical capacity of 372 mAh g⁻¹ imposes a significant limitation on the overall energy density of next-generation LIBs. [5] Silicon, in contrast, offers a much higher theoretical capacity of ~4200 mAh g⁻¹ based on the formation of Li 22 Si 5 , making it an attractive alternative for high-capacity anode design. [6, 7] Despite this promise, silicon suffers from severe volume changes up to 400% during lithiation which leads to particle pulverization, unstable solid electrolyte interphase (SEI) formation, and rapid capacity fading over repeated cycles. [8, 9] These intrinsic mechanical and interfacial challenges have prevented the widespread implementation of silicon-based anodes in practical cells. In response to the limitations of conventional anodes, extensive efforts have been directed towards developing carbon-based materials with enhanced structural flexibility and higher Li storage capacity. Among them, hard carbons derived from biomass precursors have received increasing attention due to their environmental sustainability, cost-effectiveness, and inherently disordered microstructures. [10, 11] These carbons typically exhibit turbostratic domains, hierarchical porosity, and residual heteroatoms or inorganics, all of which contribute to improved Li + accessibility and interfacial transport. In particular, their mechanical resilience and high surface area make them promising matrices for accommodating high-capacity materials like silicon, as they can partially buffer the substantial volume expansion associated with alloying reactions. [12–14] Several reports have demonstrated that integrating silicon with porous carbon frameworks derived from sources such as rice husks, [15] corn stalks, [16] or coconut shells [17] can enhance cycle stability by maintaining structural integrity and promoting stable SEI formation. However, the diversity of biomass feedstocks and the variability in their carbon–silicon interaction mechanisms highlight the need for systematic investigations into optimized hybrid architectures. In our previous work, we introduced barley husks as a viable biomass precursor for producing hard carbon anodes in LIBs. [18] That study focused on understanding the structural, compositional, and electrochemical properties of barley husks-derived carbon relative to commercial graphite. Comprehensive material characterization—including X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption analyses—revealed a predominantly amorphous carbon matrix with embedded silica phases and a moderate specific surface area. These features contributed to enhanced Li storage sites and favorable SEI formation. Electrochemical tests confirmed that barley husks-based anodes could deliver higher initial capacity and improved rate capability compared to graphite, owing to their disordered structure and hierarchical porosity. [18] While that work established barley husks as a sustainable and structurally versatile carbon source, the material was not optimized for high-capacity applications, nor was its potential as a mechanical buffer for silicon explored. Despite the growing interest in silicon–carbon composites, most prior studies have focused on synthetic carbons or commercial graphite as the host matrix, with limited emphasis on integrating high-silicon content into biomass-derived systems. While some biomass carbons have been explored in hybrid configurations, their role has largely been restricted to passive conductivity enhancement or morphological templating, without systematic investigation into their structural compatibility with silicon. [19–21] In particular, the capacity of natural biomass carbons to mitigate the severe mechanical stress and interfacial instability associated with silicon lithiation remains underexplored. Furthermore, few reports address the design of carbon–silicon hybrids where the biomass matrix inherently contains inorganic constituents—such as silica—that could contribute to mechanical buffering or improved adhesion between components. [22–24] In our earlier study, [18] the silica-rich nature of barley husks-derived carbon was identified but not fully leveraged. This raises an important question: can the structural and chemical characteristics of barley husks be exploited not only as a carbon source but also as a stabilizing framework for high-loading silicon anodes? To date, no systematic effort has been made to evaluate the electrochemical performance of barley husks and silicon hybrid anodes across varying compositions, nor to assess their full-cell integration potential against industry-relevant cathodes. In this study, we explore the use of barley husk-derived hard carbon as a functional host for silicon in high-performance LIB anodes. Building on the structural insights established in our previous work, we design a series of barley husks and silicon hybrid anodes with controlled mass ratios to systematically investigate the synergistic interaction between silicon and the silica-rich carbon matrix. The goal is to determine whether the intrinsic features of barley husks—such as their disordered carbon structure, hierarchical porosity, and embedded silica—can contribute to mitigating silicon’s volumetric expansion effects on the anode, thereby enhancing cycling stability and rate performance. We conduct comprehensive electrochemical testing, including half-cell and full-cell evaluations against NMC622 cathodes, to assess capacity retention, Coulombic efficiency, and rate capability across different hybrid compositions. The fabrication method involves only carbonization and mechanical mixing, emphasizing simplicity and scalability. Our findings demonstrate that barley husks-based hybrid anodes not only outperform graphite and pure silicon anodes but also offer a practical route toward sustainable, high-capacity anode design for next-generation LIBs. 2. Results and Discussion The electrochemical behaviour of all anodes was initially assessed using CV analysis, as shown in Figure 1 . Each anode exhibits distinct lithiation/delithiation features depending on its composition, offering insight into the underlying charge storage mechanisms and reaction reversibility. The CV profile of the Gr anode in Figure 1a exhibits electrochemical features typical of Li⁺ intercalation into graphitic carbon. During the first cathodic sweep, a broad reduction peak centred around 0.6–0.8 V vs. Li/Li + is observed, which is absent in subsequent cycles. This peak corresponds to the formation of a solid electrolyte interphase (SEI) resulting from the reductive decomposition of the electrolyte components on the graphite surface. The disappearance of this peak in the following cycles indicates the development of a passivating SEI layer that stabilizes the electrode–electrolyte interface, a phenomenon known to contribute to the initial irreversible capacity loss in graphite anodes. [25] As the potential further decreases, a sharp cathodic peak below 0.25 V vs Li/Li + appears, corresponding to stage-wise Li⁺ intercalation into graphite layers, culminating in the formation of the LiC₆ phase. This is followed by a narrow anodic peak at ~0.2–0.25 V vs Li/Li + in the reverse sweep, associated with the delithiation of LiC₆ back to graphite. [25, 26] The symmetry and consistency of these intercalation/deintercalation peaks across the second and third cycles confirm the high reversibility and stable kinetics of Li storage in graphite. This behaviour is characteristic of well-ordered graphitic structures and reflects minimal polarization and effective SEI passivation. The BH anode (Figure 1b) exhibits a distinctly different electrochemical profile compared to graphite, reflecting the behaviour of disordered hard carbon. The first cathodic scan shows a broad hump between associated with surface-controlled Li storage, including SEI formation, Li⁺ adsorption at defect sites, and interactions with surface functionalities and residual silica phases. [27] A subtle shoulder near 0.4–0.6 V vs Li/Li + corresponds to partial reduction of surface oxygen groups or interactions with the embedded SiO₂ content. Below ~0.2 V vs Li/Li + , the current gradually increases in a sloping fashion, indicating Li⁺ insertion into pores and disordered carbon domains, rather than graphitic staging transitions. On the anodic sweep, a broad delithiation feature appears around 0.2–0.5 V vs Li/Li + , stabilizing after the first cycle, which confirms improved interfacial kinetics and SEI maturation from cycle 2 onward. [18, 28] Upon introducing silicon into the BH matrix, a progressive evolution in the CV features is observed (Figures 1c–1e). The BH50–Si20 hybrid anode (Figure 1c), with a lower Si content, retains much of the broad BH-like lithiation profile while beginning to exhibit a distinct cathodic peak below 0.1 V vs Li/Li + , characteristic of Si alloying with Li (Li x Si formation). [29] This new peak confirms the electrochemical activity of the silicon component, while the overall smoother profile and broader anodic feature suggest that the BH matrix continues to buffer and regulate the reaction environment. As the Si content increases to 35 wt% and 50 wt% in BH35–Si35 and BH20–Si50 anodes (Figures 1d and 1e), respectively, the intensity of the sharp lithiation peak below 0.1 V vs Li/Li + significantly increases, and the anodic scan develops more pronounced features around 0.35–0.55 V vs Li/Li + , corresponding to the stepwise dealloying of Li x Si species. At the same time, the underlying BH signal is still discernible, seen as broad current responses from 0.2 to 0.6 V vs Li/Li + . This overlapping behaviour suggests that both components remain electrochemically active and that the BH matrix continues to modulate the volume change and charge distribution during cycling. Notably, the cathodic and anodic peaks in BH35–Si35 anode are sharper and better defined than in BH50–Si20 anode, indicating enhanced Si utilization, while still maintaining cycling stability — likely due to the optimal balance between mechanical buffering and active capacity. In contrast, the Gr20–Si50 anode (Figure 1f), which contains the same Si content as BH20–Si50 anode, shows more polarized and asymmetric peaks, particularly in the first cycle. The sharp lithiation and delithiation features below 0.1 V vs Li/Li + and above 0.4 V vs Li/Li + are present, but the broader separation between anodic and cathodic peaks suggests higher overpotential and poorer reaction reversibility. This behaviour implies that graphite is less effective than BH in stabilizing the Si network, likely due to its less porous (graphite: 69.254 Å ≈ 6.93 nm; BH: 51.844 Å ≈ 5.18 nm), less compliant structure, which is prone to interfacial instability and SEI breakdown. Finally, the pure Si anode (Figure 1g) shows the most pronounced and narrow lithiation peak below 0.1 V vs Li/Li + , along with steep delithiation peaks between 0.35 and 0.55 V vs Li/Li + . However, the rapid drop in current intensity and the peak shift across the cycles indicate significant SEI formation, electrode degradation, and Li trapping, all of which are well-documented limitations of Si anodes. [30] Compared to this baseline, the BH–Si hybrid anodes clearly demonstrate a more gradual, stabilized electrochemical response, particularly in BH35–Si35 anode, which balances capacity, reversibility, and kinetic accessibility. Figure 1. CV curves of a) graphite (Gr), b) pure barley husk (BH), c) BH50–Si20, d) BH35–Si35, e) BH20–Si50, f) Gr20–Si50, and g) pure silicon (Si) anodes recorded at a scan rate of 0.2 mV s⁻¹ in the voltage range of 3.0–0.01 V vs Li/Li + during the first three cycles. Galvanostatic charge–discharge profiles at C/5 are reported for the first and third cycles, as shown in Figure 2. The Gr anode (Figure 2a) displays a well-defined discharge plateau below 0.2 V vs Li/Li + and a sharp charge plateau at intercalation and deintercalation into graphite layers. The narrow voltage hysteresis (~0.07 V) and stable profile across cycles reflect efficient charge transfer and high reversibility, consistent with its low irreversible capacity loss (~11%) and initial Coulombic efficiency (ICE) of ~89%. The BH anode (Figure 2b) however, exhibits a sloped voltage profile with no distinct plateaus, spanning the entire 0.01–1.0 V vs Li/Li + range. This behaviour aligns with its broad CV response and reflects Li storage via surface interaction, defect trapping, and pore filling. The lower ICE (~60%) and absence of sharp features point to initial SEI formation and capacitive behaviour, typical of hard carbon. Upon Si addition, the hybrids show evolving voltage characteristics. BH50–Si20 anode (Figure 2c) retains BH’s sloping profile but begins to exhibit a weak lithiation plateau near 0.1 V vs Li/Li + , confirming partial Si activation. BH35–Si35 and BH20–Si50 anodes (Figures 2d and 2e, respectively) develop increasingly pronounced plateaus below 0.1 V vs Li/Li + and broad delithiation features at 0.35–0.55 V vs Li/Li + , consistent with Li x Si alloying/dealloying. BH35–Si35 anode achieves a balanced behaviour, with an ICE of ~87% and moderate hysteresis (~0.12 V vs Li/Li + ), suggesting improved Si utilization while preserving BH’s buffering role. In BH20–Si50 anode, the increased Si content enhances capacity but also introduces higher polarization and a slight drop in CE (~80%). The Gr20–Si50 anode (Figure 2f) shows sharper plateaus but greater hysteresis (~0.18 V vs Li/Li + ) than BH20–Si50 anode, reflecting sluggish kinetics and interfacial stress. This matches the CV observation of broader peak separation and underscores graphite’s limited capacity to buffer Si expansion. Pure Si (Figure 2g) shows the steepest and most defined lithiation/delithiation plateaus but suffers severe capacity loss by the third cycle and the lowest ICE (~72%), indicative of unstable SEI growth and Li trapping. Overlaid profiles (Figures 2h and 2k) summarize the performance spectrum: Gr and BH anode at either end with stable but modest profiles, Si with high but fading capacity, and BH–Si hybrid anodes—especially BH35–Si35—offering a favourable compromise between capacity, reversibility, and structural stability. Figure 2. Galvanostatic charge–discharge voltage profiles of a) graphite (Gr), b) pure barley husk (BH), c) BH50–Si20, d) BH35–Si35, e) BH20–Si50, f) Gr20–Si50, and g) pure silicon (Si) anodes at a current rate of C/5, showing the 1st and 3rd cycles. h) and k) comparative overlays of all anode types in the 1 st and 3 rd cycles, respectively. All profiles are recorded within the voltage range of 0.01–3.0 V vs Li/Li + . The cycling stability and rate capability results shown in Figure 3 further validate the electrochemical behaviour inferred from CV (Figure 1) and voltage profiles (Figure 2). At a constant current rate of C/5, the cycling performance (Figure 3a) highlights substantial differences in both capacity and stability across the electrode formulations. The Gr and BH anodes deliver stable but modest capacities of respectively, in line with their theoretical and structural limitations. Notably, BH exhibits slightly higher capacity than graphite due to additional Li storage at defect sites and within micro- and mesopores, consistent with its sloping voltage profile and broad CV features. Both maintain >95% of their capacity over 50 cycles, reflecting minimal volume change and well-established SEI stabilization. Upon Si incorporation, the BH–Si hybrid anodes demonstrate enhanced capacities. BH50–Si20 anode achieves ~670 mAh g⁻¹ after 50 cycles, while BH35–Si35 and BH20–Si50 anodes reach respectively. Despite increasing Si content, all BH–Si hybrid anodes retain good stability with gradual capacity fade and no sudden drops, underscoring the role of BH in mitigating Si volume expansion. In contrast, Gr20–Si50, which has the same Si loading as BH20–Si50, shows faster capacity decay (~960 to a mechanical buffer. The pure Si anode, while initially achieving by cycle 50 — confirming its poor structural resilience. Coulombic efficiency trends (Figure 3b) provide additional insight. In the present study, all anodes stabilize above 98% within 10 cycles, indicating effective SEI formation. BH–Si hybrid anodes exhibit slightly delayed CE stabilization compared to graphite and BH, due to increased interfacial activity from Si. Among them, BH35–Si35 anode reaches >99% by cycle 15 and maintains consistent CE thereafter, highlighting its balance between capacity and interfacial stability. Rate performance (Figure 3c) further differentiates the anodes under dynamic operating conditions. BH20–Si50 anode consistently delivers the highest capacity across all current rates, retaining to C/10. BH35–Si35 and BH50–Si20 anodes follow with intermediate capacities (~820 mAh g⁻¹ and anodes show excellent rate response and capacity recovery, confirming robust structural integrity and fast ion transport. In contrast, Gr20–Si50 shows diminished rate tolerance, while performing poorly at higher C-rates due to its diffusion-limited intercalation mechanism. The long-term cycling stability of the anodes is shown in Figure 3d. The pure Si anode rapidly loses capacity, dropping to negligible levels within the initial few cycles due to severe structural failure from extensive volume changes. In contrast, the Gr anode demonstrates excellent stability, retaining 96.6%, 94.4%, 90.9%, 87.7%, and 84.6% of its initial capacity after 100, 200, 300, 400, and 500 cycles, respectively. Similarly, the pure BH anode shows stable but moderate performance, with retention values of 97.9%, 96.4%, 93.9%, 88.0%, and 80.8% at these intervals, confirming its robust structural integrity. For Si-containing BH composites, increasing Si content results in higher initial capacity but gradually decreases cycling stability. BH50–Si20 anode shows notably stable cycling performance, maintaining 97.6%, 90.3%, 87.2%, 82.7%, and 78.1% after each interval. BH35–Si35 anode retains slightly lower values at 89.0%, 84.1%, 79.9%, 77.5%, and 72.9%, which remain commendable given the higher Si fraction. BH20–Si50 anode, despite the highest Si content, retains reasonable stability with retention values of 86.3%, 80.5%, 75.6%, 71.3%, and 65.8%, highlighting the effective buffering capability of BH at substantial Si loadings. In sharp contrast, the Gr20–Si50 composite suffers rapid capacity fading, with significant deterioration observed after each interval (67.6%, 49.8%, 33.2%, 17.2%, and ultimately just 2.4% after 500 cycles). This rapid decline underscores graphite’s inadequacy in accommodating Si-induced volume expansion compared to BH-based matrices. Together, these results confirm that BH–Si hybrid anodes offer a compelling combination of high capacity, rate capability, and stability. In particular, BH35–Si35 emerges as the optimal formulation, balancing structural buffering, electrochemical reversibility, and performance retention under practical cycling conditions. Figure 3. a) Cycling performance of all anodes at a current rate of C/5 over 50 cycles, (b) Corresponding Coulombic efficiency (CE) profiles during cycling, c) Rate capability of selected anodes evaluated across multiple current densities (C/10 to 2C) and returned to C/10, and (d) Long-term cycling performance of all anodes over 500 charge–discharge cycles. The differential capacity (dQ/dV) profiles in Figure 4 provide further insight into the redox mechanisms and cycling stability of the anodes by tracking the evolution of lithiation/delithiation processes over time. For the Gr anode (Figure 4a), sharp and well-defined peaks appear at Li/Li + in the cathodic and anodic directions, respectively, corresponding to the reversible staging transitions between graphite and LiC₆. These features remain highly stable across 50 cycles, confirming excellent reversibility and minimal degradation, in agreement with the consistent CV and voltage profiles observed earlier. In contrast, the BH anode (Figure 4b) displays broad and diffuse dQ/dV features, with cathodic activity spread from ~1.0 to 0.1 V vs Li/Li + and a similarly wide anodic region from ~0.1 to 0.6 V vs Li/Li + . These broad signals are indicative of pseudocapacitive and diffusion-limited Li⁺ storage within disordered carbon domains and pores. Importantly, the curves remain relatively stable from cycle 3 to 50, confirming the structural robustness and interfacial stability of the BH matrix. For the BH–Si hybrid anodes, the dQ/dV profiles reveal the progressive influence of Si on the redox behaviour. BH50–Si20 anode (Figure 4c) shows both the broad BH-related features and emerging sharp peaks near Li/Li + (delithiation), characteristic of Li x Si alloying/dealloying. These peaks intensify with increasing Si content in BH35–Si35 and BH20–Si50 anodes (Figures 4d and 4e, respectively), where they become more pronounced and better defined. These hybrid systems maintain reasonably stable peak positions through cycle 50, especially in BH35–Si35 anode, which displays minimal peak broadening or shift—highlighting its balanced kinetics and structural integrity. In contrast, BH20–Si50 anode begins to show slight peak smearing by cycle 50, suggesting moderate polarization growth likely due to higher silicon content and increasing mechanical stress. Gr20–Si50 (Figure 4f), which contains the same Si content as BH20–Si50 anode but uses graphite as the host, shows more significant peak distortion and broadening over time, particularly in the anodic region. This degradation in signal definition implies poorer structural accommodation of silicon and greater instability at the graphite–Si interface. This correlates with the faster capacity fading and greater voltage hysteresis seen earlier. The pure Si anode (Figure 4g) exhibits the highest peak intensity initially, with steep lithiation and delithiation peaks corresponding to multi-step Li x Si alloying transitions. However, these peaks quickly decay and broaden with cycling, accompanied by a noticeable drop in peak height by cycle 50. This confirms substantial SEI reformation, Li trapping, and degradation of active Si, which is consistent with its rapid capacity loss and low Coulombic efficiency. Overall, the dQ/dV analysis reinforces the earlier observations: BH-derived hard carbon acts as an effective host for Si, stabilizing the redox behaviour while suppressing interfacial degradation. Among all hybrids, BH35–Si35 anode demonstrates the most stable reaction profile, reflecting its optimal balance between active material content and structural buffering capacity. Figure 4. Differential capacity (dQ/dV) plots of a) graphite (Gr), b) barley husk (BH), c) BH50–Si20, d) BH35–Si35, e) BH20–Si50, f) Gr20–Si50, and g) silicon (Si) anodes recorded at a current rate of C/5 over selected cycles (1st, 2nd, 3rd, 10th, and 50th). To further investigate the structural and morphological stability of Si-containing anodes during cycling, SEM analysis was performed comparing the BH20–Si50 and Gr20–Si50 anodes before cycling and after 100 cycles (Figure 5). Prior to cycling, both anodes display relatively homogeneous particle distributions with distinct morphologies. BH20–Si50 anode exhibits a porous, irregular structure characteristic of biomass-derived carbon, while Gr20–Si50 shows smoother, plate-like graphite particles uniformly mixed with silicon particles. After 100 cycles, the BH20–Si50 anode maintains notable structural integrity, retaining its porous architecture with only minor particle fragmentation and surface roughening. This observation confirms the effectiveness of the BH matrix in buffering the significant volume changes caused by repeated Si lithiation/delithiation, resulting in stable long-term cycling performance. In contrast, the Gr20–Si50 anode shows severe structural degradation after cycling, with extensive particle cracking, pulverization, and loss of the original morphology. The substantial morphological deterioration directly correlates with its rapid capacity fading observed previously. These findings visually reinforce the critical role of the BH matrix in mitigating the mechanical stresses associated with silicon expansion, thus enhancing structural integrity and improving cycling stability compared to graphite-based composites. Figure 5. SEM images of BH20–Si50 anode (a) before cycling and (b) after 100 cycles, and Gr20–Si50 anode (c) before cycling and (d) after 100 cycles, all cycled at C/5. To construct a full cell, we selected NMC622 as the cathode material due to its favourable balance of high capacity, structural stability, and cost-effectiveness. Its electrochemical performance was first evaluated in a half-cell configuration using Li metal as the counter/reference electrode, and the results are summarized in Figure 6. As shown in Figure 6a, the charge–discharge profiles at the 1 st and 50 th cycles display the characteristic sloping behaviour of layered oxide cathodes, with a well-defined voltage plateau centred around 3.8 V vs. Li⁺/Li, consistent with reversible Li⁺ intercalation/deintercalation. The anode demonstrates robust cycling stability, with a capacity retention of 92% after 50 cycles at C/5 (Figure 6b) and maintains a high Coulombic efficiency approaching 100% throughout cycling. Rate capability results (Figures 6c and 6d) further confirm the reliable kinetics of the NMC622 cathode. The voltage profiles remain smooth and consistent across increasing current rates, and the electrode retains 82% of its initial capacity when the rate is increased from C/10 to 2C. Importantly, full capacity recovery is observed when the current is returned to C/10, confirming good structural reversibility. These results validate NMC622 as a stable and high-performing cathode and support its integration into full-cell systems. Its reliable rate response and cycling retention make it an appropriate cathode for pairing with high-capacity anodes, such as the BH20–Si50 composite, in practical full-cell configurations. Figure 6. Electrochemical performance of NMC622 in half-cell configuration; a) Voltage profiles at 1 st and 50 th cycles at C/5 current, (b) Cycling stability and Coulombic efficiency at C/5 current, (c) Voltage profiles at various rates from C/10 to 2C, and (d) Rate capability and capacity recovery. To assess the practical applicability of the BH20–Si50 composite anode, full coin cells were assembled using NMC622 as the cathode and evaluated under various testing conditions. As shown in Figure 7a, the voltage profiles at the 1 st and 100 th cycles exhibit typical sloping behaviour, with a discharge plateau near 3.6 V and a gradual increase in polarization over extended cycling—indicative of mild resistance growth and interfacial evolution. The cycling performance of the full cell is presented in Figure 7b. At a current rate of C/5, the cell delivers an initial discharge capacity of 165 mAh g⁻¹ (based on the cathode mass), with a high ICE of 98.3%. After 100 cycles, the discharge capacity remains at 147 mAh g⁻¹, corresponding to a capacity retention of 89%, while the Coulombic efficiency improves to 99.5%, reflecting stable Li utilization and effective SEI passivation across the cell. Figures 7c and 7d show the voltage profiles and rate capability of the full cell under various current rates from C/10 to 2C. The cell retains C/10, indicating good structural reversibility and kinetic accessibility. At 2C, however, the capacity drops to 113 mAh g⁻¹, reflecting a rate capability of 63%, likely due to increased kinetic limitations and interfacial polarization on both electrodes. Based on the total active material and electrolyte mass, the estimated energy density of the full cell is calculated to be 385, 373, 361, 344, and 245 Wh kg⁻¹ at C/10, C/5, C/3, 1C, and 2C, respectively. This performance enhancement over conventional graphite//NMC full cells can be attributed to the incorporation of Si into the biomass-derived carbon matrix, which provides mechanical buffering, enhances capacity, and effectively mitigates particle disintegration during repeated cycling. These results confirm the electrochemical compatibility of BH20–Si50 anode with high-voltage cathodes and demonstrate its feasibility for practical Li-ion full-cell applications with high energy density and reliable cycling performance. Figure 7. Electrochemical performance of the BH20–Si50 // NMC622 full cell. a) Charge–discharge voltage profiles at the 1st and 100th cycles, b) cycling stability and Coulombic efficiency over 100 cycles at C/5, c) Voltage profiles at varying current densities from C/10 to 2C, and (d) Rate capability and capacity recovery. 3. Conclusion In summary, we demonstrated that barley husk-derived carbon (BH) is an effective host material for accommodating high silicon (Si) loadings in LIB anodes. BH–Si composite anodes showed significantly enhanced electrochemical performance compared to graphite–Si counterparts, attributed to the structural and morphological stability provided by the BH matrix. Among various compositions tested, the BH20–Si50 composite exhibited remarkable cycling stability, maintaining approximately 65.8% of its initial capacity after 500 cycles, alongside superior rate performance and improved structural integrity, as confirmed by post-cycling SEM analyses. A full cell pairing BH20–Si50 anode with an NMC622 cathode achieved stable cycling with 89% capacity retention after 100 cycles and an impressive energy density of up to 385 Wh kg⁻¹. These results highlight the potential of biomass-derived carbon matrices, particularly BH, as sustainable and structurally robust materials for high-performance, Si-based anodes in next-generation LIBs. 4. Experimental Section 4.1. Material preparation Barley husks were obtained from a local brewery near Norwich, United Kingdom. The raw barley husks were first ground into fine fragments and thoroughly washed with deionized (DI) water to remove surface impurities. The cleaned biomass was dried at 60 °C overnight in a conventional oven. For carbonization, 35 g of the dried barley husks was transferred to ceramic crucibles and subjected to pyrolysis in a tube furnace (Carbolite TZF 12/65/550) under a continuous nitrogen flow. The temperature was raised to 1150 °C at a rate of 5 °C min⁻¹ and held for 2 hours. After natural cooling to ambient temperature, the carbonized product, containing both carbon and silica phases, was collected as a black powder (BHs-SiO₂/C). To improve homogeneity and enhance the electrochemical interface, the BHs-SiO₂/C powder underwent mechanical ball milling using 1/2-inch stainless steel balls in a high-energy mixer mill (Spex 8000D) at 1400 rpm for 20 minutes. The milled powder was then immersed in 1 M hydrochloric acid (Merck) for 8 hours at room temperature to remove residual inorganic impurities. Following acid treatment, the mixture was vacuum filtered and washed repeatedly with DI water until neutral pH was achieved. The purified material was dried at 50 °C overnight, yielding the final barley husks-based active powder (denoted as BH). To fabricate the silicon-enhanced anode materials, commercially available synthetic silicon powder (Siligrain e-Si 410 from Elkem, 99.8%, approximately 400 nm) was mechanically blended with the BH powder in three different mass ratios: 20:50, 35:35, and 50:20 (BH:Si), maintaining a total active material content of 70 wt% and the rest 30% are belonged to C65 (20%) and PAA (10%). The resulting composites were designated as BH20-Si50, BH35-Si35, and BH50-Si20, respectively. The mixtures were further homogenized by additional ball milling under the same conditions described above to ensure uniform dispersion of Si within the BH matrix. For comparative analysis, additional anode compositions were prepared: a silicon-only anode (Si) containing 70 wt% synthetic Si; a binary mixture of graphite and Si (Gr20-Si50) with a 20:50 weight ratio; and two control anodes based solely on either barley husks (BH) or commercial graphite (Gr, Acros Organics, battery grade). All active materials were used as 70 wt% of the total electrode mass and the rest 30% belonged to C65 (20%) and PAA (10%). The labels used for each anode configuration are summarized in Table 1 and will be used consistently throughout this manuscript for clarity and brevity. Table 1. Composition and labels of prepared anode materials. Gr 70% Graphite + 20% C65 + 10% PAA Conventional graphite control BH 70% BH + 20% C65 + 10% PAA barley husks-based control BH50-Si20 50% BH + 20% Si + 20% C65 + 10% PAA BH-dominant hybrid BH35-Si35 35% BH + 35% Si + 20% C65 + 10% PAA Balanced BH and Si hybrid BH20-Si50 20% BH + 50% Si + 20% C65 + 10% PAA Si-rich hybrid Gr20-Si50 20% Graphite + 50% Si + 20% C65 + 10% PAA Graphite-supported Si composite Si 70% Si + 20% C65 + 10% PAA Pure silicon anode 4.2. Characterization and measurements Comprehensive structural and compositional characterization was carried out on the primary active materials—BH, Si, and Gr—to evaluate their morphological, crystallographic, and surface chemical properties prior to electrode fabrication. The morphology and particle distribution of the powders were examined via scanning electron microscopy (SEM, Zeiss Gemini 300 FE), while elemental mapping using energy-dispersive X-ray spectroscopy (EDX, Oxford Instruments Ultim Max 170) provided spatial distribution of carbon, silicon, and oxygen. X-ray diffraction (XRD, Rigaku Smartlab SE) with Cu Kα radiation (λ = 1.540 Å, 40 kV, 50 mA) was employed over a 2θ range of 10°–80° to investigate crystallinity and phase composition. Each electrode slurry was prepared by mixing the active material (70 wt%), carbon black C65 (20 wt%) as the conductive additive, and polyacrylic acid (10 wt%) as the binder, dispersed in DI water to form a uniform paste. The slurry was then cast onto copper foil substrates using a doctor blade with a wet film thickness of 200 μm, followed by vacuum drying at 80 °C for 12 hours. Dried electrodes were punched into 14 mm diameter disks for cell assembly and electrochemical testing. All electrochemical evaluations were conducted using 2016-type coin cells assembled in an argon-filled glovebox (MBRAUN UNIlab Plus ECO) with both oxygen and moisture levels maintained below 0.5 ppm. Lithium metal chips were employed as the counter electrode, while a microporous polypropylene membrane (Celgard 2325) ) served as the separator. The electrolyte was purchased from Shenzhen Laborxing Technology Ltd and consisted of 1.2 M LiPF₆ in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a 1:3 volumetric ratio, supplemented with 15 wt% fluoroethylene carbonate (FEC) and 3 wt% vinylene carbonate (VC) as SEI-forming additives. The assembled half-cells were allowed to rest for 24 hours at room temperature before testing. Galvanostatic charge–discharge measurements were performed using a Biologic BCS-850 CLand CT3001ALand CT3001A battery tester within a voltage range of 0.01–3.0 V (vs. Li⁺/Li). Cyclic voltammetry (CV) was carried out at a scan rate of 0.2 mV s⁻¹ using a CHI 660E electrochemical workstation, and electrochemical impedance spectroscopy (EIS) was measured over a frequency range of 100 kHz to 0.01 Hz with a 5 mV perturbation amplitude. In addition to half-cell studies, full cells were assembled to further assess the practical applicability of the most promising anode compositions. Nickel manganese cobalt oxide (NMC622) was selected as the cathode. The full cells were balanced according to the theoretical capacity ratio between anode and cathode to ensure optimal performance. Full-cell assembly followed similar procedures under inert conditions, with Si-rich hybrid anode paired against NMC622 cathode using the same electrolyte and separator system. Following electrochemical cycling, selected coin cells were disassembled inside an argon-filled glovebox. The anodes were carefully extracted, and any remaining electrolyte was gently rinsed off using anhydrous dimethyl carbonate (DMC, Sigma-Aldrich). The electrodes were then dried under inert conditions within the glovebox for 12–24 hours. No thermal treatment was conducted to maintain the surface morphology for postmortem SEM analysis. Acknowledgements This work is supported by UEA’s Critical Decade for Climate Change Doctoral Training Program, funded by the Leverhulme Trust under their Doctoral Scholarship Scheme. We are also grateful to the funding from Xianhu Lab under the codes XHQD2022-001, XHR2024-001, and XHR2023-003. Author 1 and Author 2 contributed equally to this work. Received: (will be filled in by the editorial staff) Revised: (will be filled in by the editorial staff) Published online: (will be filled in by the editorial staff) References [1] F. Degen, M. Winter, D. Bendig, J. Tübke. Nat Energy 2023,8,1284–1295. [2] N.A. Sepulveda, J.D. Jenkins, A. Edington, D.S. Mallapragada, R.K. Lester. Nat Energy 2021,6,506–516. [3] M.H. Hossain, M.A. Chowdhury, N. Hossain, M.A. Islam, M.H. Mobarak. Chemical Engineering Journal 2023,16,100569. [4] J. Asenbauer, T. Eisenmann, M. Kuenzel, A. Kazzazi, Z. Chen, D. Bresser. Sustainable Energy and Fuels 2020,4,5387–5416. [5] S. Link, L. Schneider, A. Stephan, L. Weymann, P. Plötz. Nat Energy 2025,1-9. [6] L. Sun, Y. Liu, R. Shao, J. Wu, R. Jiang, Z. Jin. Energy Storage Mater 2022,46,482–502. [7] G.G. Eshetu, H. Zhang, X. Judez, H. Adenusi, M. Armand, S. Passerini, E. Figgemeier. Nat Commun 2021,12,5459. [8] A. Fereydooni, C. Yue, Y. Chao. Small 2024,20,2307275. [9] A. Paravannoor, D. Panoth, P. Pattathil. Chemical Engineering Journal Advances 2020,4,10037. [10] A. V. Baskar, G. Singh, A.M. Ruban, J.M. Davidraj, R. Bahadur, P. Sooriyakumar, P. Kumar, A. Karakoti, J. Yi, A. Vinu. Adv Funct Mater 2023,33,2208349. [11] Y. Feng, L. Liu, X. Liu, Y. Teng, Y. Li, Y. Guo, Y. Zhu, X. Wang, Y. Chao. Electrochim Acta 2020,359,136933. [12] X. Gao, Zan and Zhang, Yunya and Song, Ningning and Li. Mater Res Lett 2017,5,69–88. [13] C. Zhu, Youyu and Chen, Mingming and Li, Qi and Yuan, Chao and Wang. Carbon N Y 2018,129,695-701. [14] Y. Li, L. Liu, X. Liu, Y. Feng, B. Xue, L. Yu, L. Ma, Y. Zhu, Y. Chao, X. Wang. Mater Chem Phys 2021,262,124331. [15] M.K. Rybarczyk, Y. Li, M. Qiao, Y. Hu, M. Titirici, M. Lieder . Journal of Energy Chemistry 2019,29,17–22. [16] L. Sbrascini, A. Staffolani, L. Bottoni, H. Darjazi, L. Minnetti, M. Minicucci, F. Nobili. ACS Appl Mater Interfaces 2022,14,33257–33273. [17] S. Chen, H. Yang, Q. Chen, L. Liu, X. Hou, L. Luo, C. Lin, C. Li, Y. Chen. Electrochimica Acta 2020,346,136239. [18] C. Yue, A. Fereydooni, P. Nakhanivej, M.B. Murria, M. Liu, Y. Zeng, Z. Wei, Q. Fu, X. Zhao, M.J. Loveridge, Y. Chao. RSC Sustainability 2025,3,2915. [19] C. del M. Saavedra Rios, V. Simone, L. Simonin, S. Martinet, C. Dupont. Biomass Bioenergy 2018,117,32–37. [20] A. Rodriguez Correa, Catalina and Kruse. Materials 2018,11,1568. [21] Y. Li, L. Liu, X. Liu, Y. Feng, L. Yu, Z. He, X. Cui, M. Zhang, Y. Zhu. Ionics (Kiel) 2022,151–160. [22] C. Liang, L. Zhou, C. Zhou, H. Huang, S. Liang, Y. Xia, Y. Gan, X. Tao, J. Zhang, W. Zhang. Mater Res Bull 2017,96,347–353. [23] W. An, J. Fu, J. Su, L. Wang, X. Peng, K. Wu, Q. Chen, Y. Bi, B. Gao, X. Zhang. J Power Sources 2017,345,227–236. [24] Y. Feng, X. Liu, L. Liu, Z. Zhang, Y. Teng, D. Yu, J. Sui, X. Wang . Chemistry Select 2018,3,10338–10344. [25] S.J. An, J. Li, C. Daniel, D. Mohanty, S. Nagpure, D.L. Wood. Carbon N Y 2016,105,52–76. [26] J. Collins, G. Gourdin, M. Foster, D. Qu. Carbon N Y 2015,92,193–244. [27] Z. Yang, Y. Du, G. Hou, Y. Ouyang, F. Ding, F. Yuan. Electrochimica Acta 2020,329,135141. [28] W. Wu, M. Wang, J. Wang, C. Wang, Y. Deng. ACS Appl Energy Mater 2020,3,3884–3892. [29] J. Tu, Y. Yuan, P. Zhan, H. Jiao, X. Wang, H. Zhu, S. Jiao. Journal of Physical Chemistry C 2014,118,7357–7362. [30] J. Rohrer, K. Albe. Journal of Physical Chemistry C 2013,117,18796–18803. Supplementary Material File (image11.emf) Download 67.33 KB File (image13.emf) Download 121.61 KB File (image4.emf) Download 174.50 KB File (image6.emf) Download 177.39 KB Information & Authors Information Version history V1 Version 1 27 August 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords anode materials barley husks lithium-ion batteries silicon sustainability Authors Affiliations Alireza Fereydooni Foshan Xianhu Laboratory View all articles by this author Chenghao Yue Foshan Xianhu Laboratory View all articles by this author Puritut Nakhanivej University of Warwick View all articles by this author Maria Murria University of Warwick View all articles by this author Mingrui Liu Foshan Xianhu Laboratory View all articles by this author Yuexi Zeng Foshan Xianhu Laboratory View all articles by this author Zhijie Wei Foshan Xianhu Laboratory View all articles by this author Qiuju Fu Qilu University of Technology View all articles by this author Xuebo Zhao Qilu University of Technology View all articles by this author Melanie Loveridge University of Warwick View all articles by this author Yimin Chao 0000-0002-8488-2690 [email protected] Foshan Xianhu Laboratory View all articles by this author Metrics & Citations Metrics Article Usage 567 views 261 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Alireza Fereydooni, Chenghao Yue, Puritut Nakhanivej, et al. 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