Water-based processing of high-mass loading thick NMC electrodes for high-performing Li-ion batteries and microstructure visualization by X-ray computed tomography

Water-based processing of high-mass loading thick NMC electrodes for high-performing Li-ion batteries and microstructure visualization by X-ray computed tomography | 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 Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed.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. 29 November 2025 V1 Latest version Share on Water-based processing of high-mass loading thick NMC electrodes for high-performing Li-ion batteries and microstructure visualization by X-ray computed tomography Authors : Juntao Li 0000-0001-6158-604X [email protected] , Xuekun Lu , Srinivas Gadipelli 0000-0002-1362-6905 , Jie Yang , Zhu Meng , Yeshui Zhang , Dan J. L. Brett , and Paul Shearing Authors Info & Affiliations https://doi.org/10.22541/au.176438362.22844634/v1 383 views 209 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract The growing demand for high energy density storage technologies has intensified research and development on electrode design/processing routes with improved safety, cyclic-life and performance. To achieve these goals, it is crucial to understand the microstructure of cathode active materials (CAMs) and their influence on battery performance. Herein, we report a fabrication process for high mass loading, thick LiNi0.6Mn0.2Co0.2O2 (NMC622) electrodes via a modified, environmentally benign, water-based processing that facilitates a low-tortuosity structure for high performance battery. The electrodes were examined using X-ray computed tomography, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy revealing much-needed physicochemical insights. A dual-layer thick electrode is produced with a high areal capacity of 9.2 mAh cm-2 at high active material loading to 51.5 mg cm-2 while maintaining the accessible capacity at elevated C-rates. 3D microstructure-resolved modelling reveals the effect of macropores in the DLE electrode in enhancing local electrolyte transport, which is conducive to a mitigated reaction overpotential, improved lithiation exchange current density and slightly deeper degree of lithiation than the conventional NMP electrode. The electrode microstructure design and characterization tools employed in this study can also be applied to other high energy density electrochemical devices that require efficient and rapid mass transport in a specific direction. Water-based processing of high-mass loading thick NMC electrodes for high-performing Li-ion batteries and microstructure visualization by X-ray computed tomography Juntao Li * , Xuekun Lu, Srinivas Gadipelli, Jie Yang, Zhu Meng, Yeshui Zhang, Dan J. L. Brett, and Paul R. Shearing * Dr. J.Li, Prof. P.R. Shearing Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK E-mail: [email protected] , [email protected] ; Dr J.Li, Dr. S. Gadipelli, Dr. Y. Zhang Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, UK Dr. J.Li, Prof. P.R. Shearing The Faraday Institution, Quad One, Didcot OX11 0RA, UK Dr. X. Lu, Jie Yang School of Engineering and Materials Science, Queen Mary University of London, E1 4NS, London, UK Dr. S. Gadipelli College of Physics, Sichuan University, Chengdu 610064, China Dr. Z, Meng Department of Chemical Engineering, Imperial College, London, London SW7 2AZ, UK Dr. Y. Zhang School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE, UK Prof. D. J. L. Brett Prosemino Limited, The Paper Yard, Canada Water, London, SE16 7LG, UK Keywords: (lithium ion batteries, x-ray computed tomography, energy storage) The growing demand for high energy density storage technologies has intensified research and development on electrode design/processing routes to improve safety, cyclic-life and performance. To achieve these goals, it is crucial to understand the microstructure of cathode active materials (CAMs) and their influence on battery performance. Herein, we report a fabrication process for high mass loading, thick LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) electrodes via a modified, environmentally benign, water-based processing that facilitates a low-tortuosity structure for high-performance batteries. The electrodes were examined using X-ray computed tomography, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy revealing much-needed physicochemical insights. A dual-layer thick electrode (DLE) is produced with a high areal capacity of 9.2 mAh cm -2 at high active material loading to 51.5 mg cm -2 while maintaining the accessible capacity at elevated C-rates. 3D microstructure-resolved modelling reveals the effect of macropores in the DLE electrode in enhancing local electrolyte transport, which is conducive to a mitigated reaction overpotential, improved lithiation exchange current density and slightly deeper degree of lithiation than the conventional NMP electrode. The electrode microstructure design and characterization tools employed in this study can also be applied to other high-energy-density electrochemical devices that require efficient and rapid mass transport in a specific direction. Introduction Lithium-ion batteries (LIBs) are the main components of current commercial high-energy-density storage systems. [1] However, further improvements are needed for their safe and sustainable processing, affordability, life-cycle, and energy density to further advance their applications in increasingly demanding sectors such as heavy-duty vehicles. LIBs are widely used in portable electronic devices as well as in electric vehicles [2] and grid scale energy storage systems. [3] Further performance improvements can be achieved through new electrode processing routes to design high-mass-loading cathodes. Here it is worth mentioning that cathode materials are the lithium-ion reserves in commercial cells (which generally comprise surplus anode materials for safety) and, thus directly govern the energy density, lifespan, and safety of the LIBs. A more sustainable and efficient electrode design method is required to manufacture high mass loading, thick cathodes. [4] Widely adopted electrode manufacturing routes not only suffer from low production efficiency, high energy consumption, and waste generation, but also offer limited morphological control, thereby limiting their deliverable energy density. [5–7] A potential strategy for enhancing gravimetric and volumetric energy densities is to produce high-mass-loading electrodes, thereby decreasing the relative proportion of inactive components, such as current collectors and separators. [1] As an example, 1000 cm 2 of Al foil is required to assemble a 3000 mAh cell, which consists of a 3.0 mAh cm -2 cathode, whereas, only 750 cm 2 of Al foil is needed to fabricate a 3000 mAh cell with a cathode loading level of 4.0 mAh cm -2 . [7] This decrease in current collector material directly reduces the overall volume and weight of the cell, and therefore energy densities of LIBs are enhanced with respect to the increased mass loading of the cathode. However, in practice, such proportional benefit is not practically attained as the electrode develops ionic/electronic diffusive/resistive paths with the increase of mass loading levels, which can induce inferior charge kinetics, poor electrode structural stability as well as poor rate performance at higher rates. Accordingly, electrochemical performance with enhanced mass loading levels or electrode thickness/densities are often not clearly correlated to deliverable specific energy. For example, Li ǁNMC811 cells with high cathode loadings have significantly degraded capacity retention, indicating that lower loading could improve durability. Furthermore, higher CAM loading may increase mechanical defects and contact loss. [8] Meanwhile, the use of N-methyl-2-pyrrolidone (NMP) solvents in cathode fabrication process raises concerns regarding toxicity, environmental impact and cost. As a result, there has been a growing interest in developing alternative solvents and solvent-free methods, such as the use of water-based or non-toxic organic solvents. [9,10] Water-based electrodes can provide high performance in terms of energy density, power density, and cyclic stability. [11,12] Recently, Maria et al. reported progress on water-based NMC532 by adding 0.5 wt% H 3 PO 4 to improve the cyclic stability but limited to low mass loading. [13] A LiFePO 4 water-based slurry has also been report by Tsai et al, however it lacks studying on the electrode thickness over 80 µm. [14] Water based process can be advantageous with respect to the less processing time and energy consumption over NMP alternatives. [15-17] for manufacturing CAMs. NMP is a polar aprotic solvent with high boiling point, low vapor pressure, and good solvating properties and has been extensively used in the production of CAMs with binder elements (CBD). [10,18] However, its high toxicity and potential environmental hazards [15] along with the production, recovery and disposal has raised concerns for the economic and environmental sustainability. Furthermore, the conventional methods of electrode fabrication, via slurry coating, make it difficult to produce thick electrodes with NMP solvents without risking cracking or delamination of the current collector. This is because the drying process creates capillary forces that leads to the accumulation of internal strains and stresses. [12,19,20] Despite these advances, research on the relationship between manufacturing processes and the resulting morphology of water-based electrodes remains limited. In this study, high-mass-loading LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) cathodes are fabricated with a water-based process. For comparison, a typical (NMP/PVDF)-based cathode is also fabricated. These electrodes are thoroughly characterised using several methods, including powder X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and optical microscopy. A novel dual-layer electrode (DLE) is designed with a high areal capacity of 9.2 mAh cm -2 at 0.22 mA cm -2 and a high active material loading of 51.5 mg cm -2 . In addition to comprehensive electrochemical characterization, X-ray computed tomography (CT) is applied to further understand the porosity and pore size distribution (PSD) of the electrodes and their microstructure/performance relationships. X-ray CT is a highly effective imaging technique for analysing the microstructure of the electrodes as it is a non-destructive technique and provides important information on particle size distribution, pore structure/arrangement, and electrode degradation, which affects their performance and stability/lifespan in practical cells. [21] In water-based electrodes, the hydrogen evolution from the electrode slurry during the drying process may form with low tortuosity between the active materials. In principle, the channels can help accelerate the ion transport. Therefore, X-ray CT analysis provides important insights of the volume fraction and distribution of particle size with respect to the distance from the current collector. Compared to other techniques, X-ray CT can capture deep microstructural information essential to create accurate 3D models and visualization of the electrode structures [5,21–23] which can then be used for simulations and further optimization purposes. Our water-based NMC622 cathodes at high mass loading show high performance in delivering 6.4 mAh cm -2 and than typical NMP/PVDF processed NMC622 with a mass loading of 35.3 mg cm -2 exhibiting 5.4 mAh cm -2 and ~ 18.9 mWh cm -2 . Moreover, our dual-layer electrodes at high mass loading also offer high-rate capability and deliver impressive cyclic stability compared to the conventional NMP-based electrode. 2. Results and discussion NMC622-based cathodes with the same mass loading made by water, water with isopropyl alcohol (IPA) and NMP solvents were manufactured (denoted as WT, IPA and NMP, respectively). Optical microscopy images and virtual slices of reconstructed X-ray CT images reveal the profound microstructural differences of these as fabricated electrodes (Figure 1a-f and S1) . As can be seen, the NMP electrode is homogenous with high particle packing density (Figure 1a and 1d; Fig. S1). In contrast, in the WT electrode (without IPA addition) shows significant fraction of voids and cracks (Figure 1b and 1c; Fig. S1), which are reduced with the addition of IPA (IPA electrode in Figure 1c and 1f; Fig. S1). This can be attributed to hydrogen evolution during the drying process and can be mitigated with IPA, which helps reduce the surface tension. [11,15] Figure 1. Microstructure characteristics of the electrodes. a-c) Optical images of NMP, WT and IPA based NMC electrodes. d-f) Reconstructed X-ray CT images of NMC electrode disks. All cathodes were cut into 0.8 mm disks and the unit of scale bar in all images is in microns. Particle and pore diameters are obtained by applying image segmentation techniques to each grey-scale image, segmenting it into two binary images representing active particles and non-particle space within the sample. Pore size distribution (PSD) is measured by labelling individual pores and then using the pore network modelling module for simulation in Avizo (Figure 2a-g). Figure 2h-i and S2 depict the relationship between particle size and separator distance for all samples. The average pore diameter calculated for IPA is 8.6 µm and the average pore size for WT is 25 µm (Figure 2j). The conventional thin NMP electrode shows a more even distribution with a uniform particle size distribution along the thickness direction (Figure S2). In contrast, for the WT electrode, particles are not densely packed due to the formation of large voids resembling hollow structures (Figure 2d). Figure 2j and S2, show the histogram of the particle diameter of different electrodes. Figure 2. X-ray CT characteristics of the electrodes. Binary and segmented image of a-c) IPA and d-f) WT electrode obtained from X-ray CT scan. g) An example of model pore network of electrode. h-i) Particle size distribution as a function of distance from the separator, the particle size is classified into three different ranges: 0-5 μm (black), 5-20 μm (red), and >20 μm (blue). j) PSD of WT and IPA electrodes indicate relatively narrow PSD, populated around 8 μm within the 2 and 15 μm region for IPA electrode over a broader PSD between 3 and 45 μm for WT electrode. Three different thicknesses (100, 140 and 170 μm) of each of the electrodes are made to examine the effect on the rate capability (Figure 3a-b). The thicker electrodes formed at higher mass loadings of NMC experience a sharp drop in capacity at C/2 or above rates. This can be mainly linked to the sluggish Li-ion diffusion/transport. According to the specific discharge capacity curves of thick electrodes (~170 μm of NMP, WT, IPA, presented in Figure 3c), the IPA processed electrode shows the best rate performance with specific capacity of 166.4 mAh g -1 at 0.1C among the electrodes; WT and NMP processed electrodes exhibit relatively poor rate performance (e.g. ~70 vs 91 mAh g -1 at 1C for WT (or NMP) against IPA electrode) with lower capacities of about 150 mAh g -1 . Electrochemical impedance spectroscopy (EIS) assesses the transport characteristics of charge carriers through the electrolyte and resistance of the current collectors in the high frequency range and the Li + ion migration at the electrode surface. As shown in Figure 3d, the semicircle diameters of Nyquist plots increase in the order of IPA, WT and NMP electrodes. The smaller diameter semicircle in the high frequency region indicates a lower interface charge-transfer resistance at the IPA electrode. This facilitates faster charge-transfer and efficient electrolyte diffusion; thus, IPA performs batter compared to NMP electrode. The porosity of the electrodes (Figures 1-2) impact significantly on the mass loading and electrochemical performance. [24] Porosity improves the surface area and facilitates ion diffusion, which can lead to improved electrochemical performance. However, high porosity can cause poor mechanical stability, which can contribute to poor life cycle performance, as well as compromising active material loading and reducing volumetric energy density. Accordingly, as shown in Figure 3e, the IPA electrode with an optimal average porosity (about 0.58) value, that is between the low and high porosity NMP and WT electrodes (with respective average porosities of about 0.45 and 0.70) exhibits relatively high capacity and rate performance when compared with NMP and WT electrodes based cells (Figure 3c). To isolate the effects of thickness, three IPA electrodes of different thicknesses (100, 140 and 170 μm) identical to NMP electrodes were fabricated and compared with respect to their measured rate capabilities (in Figure 3f-h). It can be seen that both IPA and NMP electrodes at 0.1C show a very similar capacity values against electrode thickness. Likewise, a high rate capability behaviour is observed in thin electrodes of 100 μm. However, this behaviour changes significantly in thick cathodes; NMP electrode with low porosity exhibits relatively poor rate performance with significantly reduced capacities compared to the IPA electrodes with increased thickness. The IPA with optimal porosity facilitates high rate capability. Figure 3. Electrochemical characteristics of the electrodes in half-cell. a-b) Rate capability (a) and specific discharge capacity (b) of NMP electrodes with increased thickness, measured at different C-rates. c-e) Specific capacity/rate capability curves, measured at 0.1C (solid line), 0.5C (short dash line) and 1C (dash line) rates (c), Nyquist plots (d) and average porosity as a function of distance from the current collector (e) of NMP, WT and IPA electrodes with similar mass loading. f-h) Specific discharge capacity values of the IPA and NMC electrodes of 100, 140 and 170 µm thick. Restricted by the limitations associated with manufacturing thick NMP-based electrodes to achieve high energy density (as discussed above), a dual-layer assembly electrode (DLE) was further designed to attain high performing from a 170 µm thickness. For this, a thin layer of 100 µm wet thickness was first formed with NMP slurry coating and another thick layer of 300 µm thick over coating was produced using IPA slurry. When dried, this DLE comprises thin NMP and thick IPA electrode assembly as is visualised by X-ray CT as presented in Figure 4 and S3. The bottom NMP layer has lower mass loading (~15 mg cm -2 ) of NMC to reduce the internal resistance (as discussed before, Figure 3) and to maintain good mechanical structure. The IPA overlayer has a higher mass loading (~30 mg cm -2 ) of NMC to increase the overall energy density. Figure 4. X-ray CT characteristic visualisation of DLE assembly. a) X-ray CT image showing the 0.8 mm disk. b-c) Reconstructed volume and segmented tomography slices. (Colour code – yellow and black represent the NMC particle architecture and porosity respectively). d-f) NMC volume fraction plots as a function of distance from the current collector for different NMC sample d) WT, e) IPA, f) DLE. For comparative understanding, the high mass loading of thick WT, IPA and DLE electrode volume fraction as a function of distance from the current collector is presented in Fig. 4d-f. The volume fraction was calculated from X-ray CT. The WT electrode exhibits relatively low volume fraction of NMC (about 19%) compared to IPA and DLE electrodes, which shows high volume fraction of 30 to 48%. The bottom NMP layer of the DLE appears to have high volume fraction of active NMC particles compared to an IPA overlayer (Figure 4f). It is interesting to note that the difference in boiling point (202 °C), density (1.03 g cm - ³) and molecular size as well as viscosity of NMP and water as well as IPA (82.3 °C; 0.786 g cm - ³) can result in faster drying of an overlayer than the NMP layer with varied volume fraction of particle assembly due to the void formation. [17] Powder XRD patterns confirm the predominantly similar crystal structure in NMP, WT, IPA and DLE electrodes (Figure 5a). The noticeable changes in the relative peak intensities and their shifts to lower angle can be attributed to the lattice strain and electrode structure formation. For example, NMP and IPA electrodes exhibit identical XRD patterns with similar peak intensity pattern compared to the WT and DLE electrode. Likewise, WT and IPA electrodes appear to show peak shifts to low angle compared to the NMP. FTIR spectra of the electrodes with prominent peaks at 556 and 667 cm -1 are attributed to the metal-O stretching vibration (Figure 5b). [25,26] Such M-O modes are also evident in Raman spectra with two peaks at are belong to A 1g and E g modes of the R̅3m structure of NMC622 (Figure 5c). [26,27] XPS spectra further show different elemental coordination environments in the electrodes. For example, those peaks at 286.3 and 284.6 eV in the C 1s spectra are related to C‒O and C‒C/C‒H, and peak at 288.2 eV is from C=O of the binder elements (Figure 5d). The O 1s spectra exhibit two peaks at 533.8 and 531.8 eV due to the presence of C−O and C=O functional groups of the binder elements, e.g. CMC (Figure 5e) as is seen with F 1s spectra for the PVDF binder (Figure 5f). [28,29] Figure 5. Structural characteristics of NMP, WT, IPA and DLE electrodes. a) XRD patterns. b) FTIR spectra. c) Raman spectra. d-f) XPS core-level spectra of C 1s, O 1s and F 1s. To compare the electrochemical performance of electrodes made with different methods, CV (cyclic voltammetry) was conducted between 3.0 V and 4.5 V at a scan rate of 0.05 mV s -1 (Figure 6a). For the NMP electrode, in the forward scan anodic peak at around 3.8 V vs. Li/Li + corresponds to the oxidation of the transition metal ions (Ni, Mn, Co) to their higher oxidation state, which results in the extraction of Li ions from the electrode. In the reverse scan, the cathodic peak at around 3.6 V vs. Li/Li + , corresponds to the reduction reaction, and indicates a good electrochemical reversibility of electrode. [30] Compared to this, the IPA and DLE electrodes are less prone to such oxidation-reduction reactions meaning that these cathodes can deliver better electrochemical performance, and DLE in particular provides improvements as evidenced by EIS data (Figure 6b). Both IPA and DLE electrodes show similarly efficient electrolyte diffusion characteristics compared to NMP electrode, which exhibits more sluggish ionic transport. In agreement with CV and EIS data, the DLE electrode with active material loading of 51.5 mg cm -2 exhibits an exceptional areal capacity of 9.2 mAh cm -2 when discharged at a rate of 0.22 mA cm -2 (Figure 6c). Likewise, as shown in Figure 6d, DLE electrode delivers a specific capacity of ~163 mAh g ‑1 at 0.1C rate, higher than the value offered by NMP electrode along with the high rate performance (Figure 6e). The sudden discharge capacity loss of NMP at ≥1C rates is mainly attributed to the limited Li ion diffusion. [31] The better rate capability of DLE electrode can be associated to the optimal porous architecture (Fig. 4) that facilitates the desirable transport properties. Both high internal resistance and Li ion diffusion contribute to the premature cutoff caused by polarization effect. Such electrode formulation also yields better cyclic stability (Figure 6f). Figure 6. Battery characteristics of NMP, IPA and DLE electrodes. a) CV at a scan rate of 0.05 mV s -1 . b) Nyquist plot. c) Areal capacity against current density. d) Charge and discharge profiles recorded at 0.1C and 1C. e) Rate capability. f) Cycling test at 0.5 mA cm -2 . 3D microstructure-resolved model can further provide a physics-based understanding of the effectiveness of the DLE design in comparison of the NMP electrode. The reconstructed 3D microstructures of the electrodes from X-ray CT data were segmented, meshed and used for model development (see Method section for details). Figure. 7a and b compares the electrolyte concentration distribution of the DLE and NMP electrodes at 30% SOC under 1C lithiation. Due to the large thickness of the electrodes, concentration gradient is observed in both electrodes. However, the macropores in the DLE electrode effectively boost the local electrolyte transport, as evidenced by a higher electrolyte concentration at the proximity of the macropore (Figure. 7c) than that in the NMP electrode (Figure. 7d). This leads to a higher overpotential at the reaction interface in the NMP electrode (Figure. 7f) than the DLE electrode (Figure. 7e). As the reaction kinetics is highly dependent on the concentration of the reactants, such difference of local electrolyte concentration also contributes to a slightly higher lithiation current density in the DLE electrode (Figure. 7g) than NMP (Figure. 7h), and thus a slightly higher degree of lithiation in the DLE electrode (Figure. 7i) than NMP (Figure. 7j) at the bottom half of the electrode at 50% SOC, although both electrodes exhibit drastic global lithiation gradient due to the electrolyte concentration gradient. Figure 7. 3D structure reconstruction and electrochemical modelling. a) Electrode geometry for DLE (red) and NMP (black). b) Pore size plots as a function of distance from the current collector for different NMC samples in cross section. c) Simulated discharge curve of the reconstructed DLE and NMP. d) State of lithiation in particles for DLE (top) and NMP (bottom). 3. Conclusion We have developed a method to increase the thickness of an electrode without sacrificing its electrochemical performance in the battery. This involves applying a thin layer of NMP-based slurry as the base, followed by a second layer of IPA-assisted water-based slurry with a thickness of approximately 170 µm. By using a modified water-based NMC electrode processing technique we achieve a high areal capacity of 9.2 mAh cm -2 and a high active material loading of 51.5 mg cm -2 . Various characterization methods employed to evaluate the feasibility of producing high-mass loading, thick electrodes of NMC622. In particular, X-ray CT on four different cathodes not only helps on visualization but also evidences the volume fraction and particle size distribution of electrodes processed by different solvents. The qualitative and quantitative information obtained by X-ray CT can guide and correlate the process-relevant thick/high mass loading electrode formation and relevant electrochemical performance to produce LIBs with high energy densities/specific capacities. Besides, with the 3D microstructure-resolved modelling reveals the effect of macropores in the DLE electrode in enhancing local electrolyte transport, which is conducive to a mitigated reaction overpotential, improved lithiation exchange current density and slightly deeper degree of lithiation than the conventional NMP electrode. Our method can be adapted for other energy storage and conversion devices that necessitate efficient and rapid mass transport. 4. Experimental Section Electrode components The NMP-based cathode slurry consists 93 wt% LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622, purchased from BASF), 3.5 wt% PVDF (Solvay) and 3.5 wt% C65 (Imerys). The water-based cathode slurry consists 90 wt% LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622, BASF), 1.5 wt% CMC (Sodium carboxymethyl cellulose, BVH8, Ashland), 3.5 wt% SBR (Styrene-Butadiene Rubber, BM451-B, Zeon), and 5 wt% C65 (Imerys). The IPA (Isopropyl Alcohol) assisted water-based cathode slurry has 90 wt% LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622, BASF), 1.5 wt% CMC (BVH8, Ashland), 3.5 wt% SBR (BM451-B, Zeon), 1.5 wt% IPA and 5 wt% C65 (Imerys). Electrode processing The procedure for making the electrode slurries and coatings have been reported previously. [32] A THINKY mixer (ARE-20, Intertronics) was used to mix the cathode binder solution (NMP/PVDF) at 2000 rpm for 15 min. Then, NMC622 and C65 were added slowly to the binder solution to form a slurry with a solid content of 60 wt%. The slurry was then mixed again at 2000 rpm for two periods of 15 min and 5 min, to cool down the slurry. The homogenous slurry was degassed in the THINKY mixer at a speed of 2000 rpm for 2 min. The slurry was then coated onto aluminium foil using a doctor blade thin-film applicator. For a dual-layer electrode, the NMP slurry was first coated in wetting thickness of ~100 µm and then IPA slurry was coated on top of the NMP slurry in a wetting thickness of ~300 µm. All the electrodes were dried at 120 °C in a vacuum oven over 12 h to remove moisture. Materials characterization Powder XRD data was collected using a Stoe Stadi-P diffractometer with Mo–K-alpha radiation. FTIR data was obtained by a Bruker ALPHA FTIR Spectrometer (Platinum-ATR) with background correction. XPS (Al–K-alpha, Thermo Scientific) data and optical microscopy (Keyence) measurements were carried out on the samples supported on a current collector. For X-ray CT, the cathodes were cut into 0.8 mm disks using a Series/Compact Laser Micromachining System (Oxford Lasers, Oxford, UK) with an embedded Class 4, 532 nm wavelength laser. All CT imaging was performed using a Zeiss Xradia 520 Versa (Carl Zeiss Microscopy Inc., Pleasanton, US) micro-CT instrument. X-ray CT scans were carried out with an X-ray source tube voltage of 120 kV with an exposure time of 25s per projection image. A total of 1601 projection images were collected per scan with a 20x lens. Reconstruction of the radiographic data was achieved using a cone-beam filtered back-projection algorithm implemented in Zeiss Scout and Scan software resulting in a reconstructed voxel size of ~0.37 µm. Post-processing of the reconstructed X-ray CT data was conducted using Avizo 9.4 (Thermo Fisher Scientific, UK) and ilastik (machine-learning-based, open-source segmentation software) for evaluation of particle distribution. Cell assembly and Electrochemical testing The electrodes were cut into 15 mm discs for coin cell assembly against a lithium metal counter electrode with a glass fiber separator. All the coin cell components, namely the cut electrodes, separators, and other coin cell parts (spacer thickness was 1 mm) were dried overnight in a vacuum oven at 120 °C to remove any moisture before assembly in an Ar filled glovebox. A 100 µL of electrolyte (Solvionic, 1 mol L -1 lithium hexafluorophosphate in (1:1 vol%) ethylene carbonate/dimethyl carbonate with 2 wt% vinylene carbonate – 99.9%) was used. Electrochemical tests were carried out using a BCS-805 Biologic battery cycler (Biologic, France). An electrochemical test formation step composed of two CC–CV charge–discharge cycles at a C-rate of C/20 (C/50 cut-off during constant voltage) within a voltage window of 2.5 to 4.2 V vs. Li/Li + for cathode half-cells. The cells were then charged at a constant current at a C/10 rate and subjected to rate capability tests using C- rates of C/10, C/5, C/2, C and 2C. Electrochemical impedance spectroscopy (EIS) and cyclic stability tests were obtained between 0.01 to 10 MHz and 0.5 mA cm -2 . Modelling The 3D volume of the NMC622 electrode prepared with NMP (100×100×150 mm 3 ) was segmented into binary data using a marker-based watershed algorithm. The foreground was labelled as the NMC particle phase, while the background was defined as the combined nanoporous + CBD phase. The effective mass transport parameter for this lumped phase was set to 0.17, based on previous measurement. [33] The same procedure was applied to the DLE, with an additional phase representing the macroporosity segmented and assigned an effective mass transport parameter of 1 (corresponding to a fully porous region with porosity = 1 and tortuosity factor = 1). These were then imported into the commercial software package Simpleware ScanIP for meshing. The meshed volumes consisting of 15 million tetrahedral elements were then imported into COMSOL Multiphysics 6.0 to build the electrochemical model with a half-cell configuration. Generalized Poisson-Nernst-Planck (gPNP) equations [34] were implemented using a series of partial differential equations (PDE). Concentrated solution theory and electro-neutrality were implemented to describe mass transport in the electrolyte, while Fick’s law was used for Li diffusion in the active material particles and Ohm’s law for electron transport in the CBD phase and active material particles. The charge-transfer reaction follows a kinetic expression originating from non-equilibrium thermodynamics, resulting in a Butler-Volmer-type expression. Details of the governing equations and parameters have been reported previously. [35] Supporting Information Supporting Information is available from the Wiley Online Library or from the author. Acknowledgements The authors gratefully acknowledge funding from the Faraday Institution through the NEXTRODE project ((Grant FIRG015, FIRG066)) and Engineering and Physical Sciences Research Council (EP/X000702/1) 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] J. Liu, Z. Bao, Y. Cui, E. J. Dufek, J. B. Goodenough, P. Khalifah, Q. Li, B. Y. Liaw, P. Liu, A. Manthiram, Y. S. Meng, V. R. Subramanian, M. F. Toney, V. V. Viswanathan, M. S. Whittingham, J. Xiao, W. Xu, J. Yang, X.-Q. Yang, J.-G. Zhang, Nat. Energy 2019 , 4 , 180.[2] J. Deng, C. Bae, A. Denlinger, T. Miller, Joule 2020 , 4 , 511.[3] B. Dunn, H. Kamath, J. M. Tarascon, Science 2011 , 334 , 928.[4] P.-E. Delannoy, B. Riou, T. Brousse, J. Le Bideau, D. Guyomard, B. Lestriez, J. Power Sources 2015 , 287 , 261.[5] A. M. Boyce, D. J. Cumming, C. Huang, S. P. Zankowski, P. S. Grant, D. J. L. Brett, P. R. Shearing, ACS Nano 2021 , 15 , 18624.[6] M. R. Barr, R. Jervis, Y. Zhang, A. J. Bodey, C. Rau, P. R. Shearing, D. J. L. Brett, M. ‐M Titirici, R. Volpe, Sci. Rep. 2021 , 11 , 1.[7] F. Wu, M. Liu, Y. Li, X. Feng, K. Zhang, Y. Bai, X. Wang, C. Wu, Electrochem. Energy Rev. 2021 , 4 , 382.[8] K. V. Carballo, X. Wang, M. Benamara, X. Meng, Nanotechnology 2024 , 35 , 075401.[9] Y. S. Zhang, N. E. Courtier, Z. Zhang, K. Liu, J. J. Bailey, A. M. Boyce, G. Richardson, P. R. Shearing, E. Kendrick, D. J. L. Brett, Adv. Energy Mater. 2022 , 12 , 2102233.[10] J. Li, Y. Lu, T. Yang, D. Ge, D. L. Wood, Z. Li, iScience 2020 , 23 , 101081.[11] Z. Du, K. M. Rollag, J. Li, S. J. An, M. Wood, Y. Sheng, P. P. Mukherjee, C. Daniel, D. L. Wood, J. Power Sources 2017 , 354 , 200.[12] C. Huang, M. Dontigny, K. Zaghib, P. S. Grant, J. Mater. Chem. A 2019 , 7 , 21421.[13] M. Bichon, D. Sotta, E. De Vito, W. Porcher, B. Lestriez, J. Power Sources 2021 , 483 , 229097.[14] F.-Y. Tsai, J.-H. Jhang, H.-W. Hsieh, C.-C. Li, J. Power Sources 2016 , 310 , 47.[15] R. Sahore, D. L. Wood, A. Kukay, K. M. Grady, J. Li, I. Belharouak, ACS Sustain. Chem. Eng. 2020 , 8 , 3162.[16] D. L. Wood, J. D. Quass, J. Li, S. Ahmed, D. Ventola, C. Daniel, Dry. Technol. 2018 , 36 , 234.[17] A. Kukay, G. Polizos, E. Bott, A. Ielvev, R. Tao, J. Sharma, J. Li, Batter. Supercaps 2024 , 7 .[18] D. L. Wood, J. Li, C. Daniel, J. Power Sources 2015 , 275 , 234.[19] C. Chen, Y. Zhang, Y. Li, Y. Kuang, J. Song, W. Luo, Y. Wang, Y. Yao, G. Pastel, J. Xie, L. Hu, Adv. Energy Mater. 2017 , 7 , 1700595.[20] M. Singh, J. Kaiser, H. Hahn, J. Electrochem. Soc. 2015 , 162 , A1196.[21] Y. S. Zhang, J. J. Bailey, Y. Sun, A. M. Boyce, W. Dawson, C. D. Reynolds, Z. Zhang, X. Lu, P. Grant, E. Kendrick, P. R. Shearing, D. J. L. Brett, J. Mater. Chem. A 2022 , 10593.[22] H. Xu, J. Zhu, D. P. Finegan, H. Zhao, X. Lu, W. Li, N. Hoffman, A. Bertei, P. Shearing, M. Z. Bazant, Adv. Energy Mater. 2021 , 11 , 2003908.[23] X. Lu, A. Bertei, D. P. Finegan, C. Tan, S. R. Daemi, J. S. Weaving, K. B. O’Regan, T. M. M. Heenan, G. Hinds, E. Kendrick, D. J. L. Brett, P. R. Shearing, Nat. Commun. 2020 , 11 , 2079.[24] Z. Chen, D. L. Danilov, R. Eichel, P. H. L. Notten, 2022 , 2201506.[25] E. Flores, N. Vonrüti, P. Novák, U. Aschauer, E. J. Berg, Chem. Mater. 2018 , 30 , 4694.[26] R. Baddour-Hadjean, J.-P. Pereira-Ramos, Chem. Rev. 2010 , 110 , 1278.[27] R. E. Ruther, A. F. Callender, H. Zhou, S. K. Martha, J. Nanda, J. Electrochem. Soc. 2015 , 162 , A98.[28] P. Viswanath, M. Yoshimura, SN Appl. Sci. 2019 , 1 , 1519.[29] N. D. Phillip, C. Daniel, G. M. Veith, J. Electrochem. Soc. 2020 , 167 , 040521.[30] R. Hausbrand, G. Cherkashinin, H. Ehrenberg, M. Gröting, K. Albe, C. Hess, W. Jaegermann, Mater. Sci. Eng. B 2015 , 192 , 3.[31] H. Zheng, J. Li, X. Song, G. Liu, V. S. Battaglia, Electrochim. Acta 2012 , 71 , 258.[32] Y. S. Zhang, J. B. Robinson, R. E. Owen, A. N. P. Radhakrishnan, J. Li, J. O. Majasan, P. R. Shearing, E. Kendrick, D. J. L. Brett, ACS Appl. Mater. Interfaces 2022 , 14 , 2092.[33] X. Lu, R. E. Owen, W. Du, Z. Zhang, A. Bertei, R. Soni, X. Zhang, F. Iacoviello, D. Li, A. Llewellyn, J. Chen, H. Zhang, X. Yao, Q. Li, Y. Zhao, S. Marathe, C. Rau, P. R. Shearing, Nat. Nanotechnol. 2025 , 20 , 1656.[34] W. Lai, F. Ciucci, Electrochim. Acta 2011 , 56 , 4369.[35] X. Lu, X. Zhang, C. Tan, T. M. M. Heenan, M. Lagnoni, K. O’Regan, S. Daemi, A. Bertei, H. G. Jones, G. Hinds, J. Park, E. Kendrick, D. J. L. Brett, P. R. Shearing, Energy Environ. Sci. 2021 , 14 , 5929. ToC figure The designed electrode demonstrates enhanced capacity and state of lithiation within the electrode structure. The electrode microstructure design and characterization tools employed in this study can also be applied to other high energy density electrochemical devices that require efficient and rapid mass transport in a specific direction. Supporting Information Water-based processing of high-mass loading thick NMC electrodes for high-performing Li-ion batteries and microstructure visualization by X-ray computed tomography Juntao Li, Xuekun Lu, Srinivas Gadipelli, Jie Yang, Zhu Meng, Yeshui Zhang, Dan J.L. Brett, and Paul R. Shearing * Figure S1. Optical images of NMP, WT and IPA -based electrodes. Figure S2. Inter-particle gap of the corresponding three types of electrodes(left). Particle size distribution as a function of distance from the separator for NMP (right). Figure S3. SEM images of the DLE. Information & Authors Information Version history V1 Version 1 29 November 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords batteries electrodes environmental materials modeling sustainability Authors Affiliations Juntao Li 0000-0001-6158-604X [email protected] University of Oxford View all articles by this author Xuekun Lu Queen Mary University of London View all articles by this author Srinivas Gadipelli 0000-0002-1362-6905 University College London View all articles by this author Jie Yang Queen Mary University of London School of Engineering and Materials Science View all articles by this author Zhu Meng Imperial College London View all articles by this author Yeshui Zhang University of Aberdeen View all articles by this author Dan J. L. Brett Prosemino Limited View all articles by this author Paul Shearing University of Oxford View all articles by this author Metrics & Citations Metrics Article Usage 383 views 209 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Juntao Li, Xuekun Lu, Srinivas Gadipelli, et al. Water-based processing of high-mass loading thick NMC electrodes for high-performing Li-ion batteries and microstructure visualization by X-ray computed tomography. Authorea . 29 November 2025. DOI: https://doi.org/10.22541/au.176438362.22844634/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . Format Please select one from the list RIS (ProCite, Reference Manager) EndNote BibTex Medlars RefWorks Direct import Tips for downloading citations document.getElementById('citMgrHelpLink').addEventListener('click', function() { popupHelp(this.href); return false; }); $(".js__slcInclude").on("change", function(e){ if ($(this).val() == 'refworks') $('#direct').prop("checked", false); $('#direct').prop("disabled", ($(this).val() == 'refworks')); }); View Options View options PDF View PDF Figures Tables Media Share Share Share article link Copy Link Copied! Copying failed. Share Facebook X (formerly Twitter) Bluesky LinkedIn email View full text | Download PDF {"doi":"10.22541/au.176438362.22844634/v1","type":"Article"} Now Reading: Share Figures Tables Close figure viewer Back to article Figure title goes here Change zoom level Go to figure location within the article Download figure Toggle share panel Toggle share panel Share Toggle information panel Toggle information panel Go to previous graphic Go to next graphic Go to previous table Go to next table All figures All tables View all material View all material xrefBack.goTo xrefBack.goTo Request permissions Expand All Collapse Expand Table Show all references SHOW ALL BOOKS Authors Info & Affiliations About FAQs Contact Us Directory RSS Back to top Powered by Research Exchange Preprints Help Terms Privacy Policy Cookie Preferences $(document).ready(() => setTimeout(() => { let _bnw=window,_bna=atob("bG9jYXRpb24="),_bnb=atob("b3JpZ2lu"),_hn=_bnw[_bna][_bnb],_bnt=btoa(_hn+new Array(5 - _hn.length % 4).join(" ")); $.get("/resource/lodash?t="+_bnt); },4000)); (function(){function c(){var b=a.contentDocument||a.contentWindow.document;if(b){var d=b.createElement('script');d.innerHTML="window.__CF$cv$params={r:'9ffe0cb9ba6ae2c5',t:'MTc3OTQ3NjI3OQ=='};var a=document.createElement('script');a.src='/cdn-cgi/challenge-platform/scripts/jsd/main.js';document.getElementsByTagName('head')[0].appendChild(a);";b.getElementsByTagName('head')[0].appendChild(d)}}if(document.body){var a=document.createElement('iframe');a.height=1;a.width=1;a.style.position='absolute';a.style.top=0;a.style.left=0;a.style.border='none';a.style.visibility='hidden';document.body.appendChild(a);if('loading'!==document.readyState)c();else if(window.addEventListener)document.addEventListener('DOMContentLoaded',c);else{var e=document.onreadystatechange||function(){};document.onreadystatechange=function(b){e(b);'loading'!==document.readyState&&(document.onreadystatechange=e,c())}}}})();