Active Material Particles Research Articles

Concentration shift experiment with an electrode of active material for precise electrochemical analysis.

To precisely evaluate the electrochemical properties of a battery of active material, we proposed a "concentration shift experiment" using single-particle electrochemical measurement (SPEM) and a diluted electrode sheet (DES). SPEM can be used for information, such as the charge-discharge and resistance properties of only the active material (extremely dilute condition: ≈0). DES consists of concentrations varying from 1% to 100% of the active material (LiCoO2) and inactive material (α-Al2O3), electrically conductive additive and binder polymer onto an Al current collector. The resistance components derived from the LiCoO2 single particles were measured and calculated. Their apparent activation energy (Ea) was 27 kJ mol-1, which is relatively low compared with the applied-type sheet electrode (30-60 kJ mol-1). Simple electric/ionic conductive route was analyzed using SPEM cell, and the fundamental LiCoO2 originated Ea could be calculated. Resistance components attributed to LiCoO2 were also measured and extracted by alternating current impedance measurements using DES. The resistance non-linearly decreased with LiCoO2 concentration, and the percolation and inhomogeneity of LiCoO2 particles were suspected. The planful isolation of an active material particle should be critical for the overall information on an electrode particle.

State-of-charge of individual active material particles in lithium ion batteries: a perspective of analytical techniques and their capabilities.

The state-of-charge (SOC) is an essential parameter for battery management systems to reflect and monitor the remaining capacity of individual battery cells. In addition to its application at the cell level, the SOC also plays an important role in the investigation of redox processes of cathode active materials (CAMs) in lithium ion batteries (LIBs) during electrochemical cycling. These processes can be influenced by a large variety of factors such as active material properties, inhomogeneities of the electrode, degradation phenomena and the charge/discharge protocol during cycling. Consequently, non-uniform redox reactions can occur, resulting in charge heterogeneities of the active material. This heterogeneity can translate into accelerated aging of the CAM and a reduction in reversible capacity of the battery cell, since the active material is not fully utilized. To understand and monitor the SOC heterogeneity at the mesoscale, a wide range of techniques have been implemented in the past. In this perspective an overview of current state-of-the-art techniques to evaluate charge heterogeneities of CAMs in LIBs is presented. Therefore, techniques which utilize synchrotron radiation like X-ray absorption near-edge structure (XANES) and transmission X-ray spectroscopy (TXM) are presented as well as Raman spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Next to these established techniques, classification single particle inductively coupled plasma optical emission spectroscopy (CL-SP-ICP-OES) as a new approach is also discussed in this perspective. For these techniques, the areas of application, advantages as well as drawbacks are highlighted and discussed.

An advanced 3D gel cathode with continuous ion and electron transport pathway for solid-state lithium batteries

Ta-doped Li7La3Zr2O12 (LLZTO) is known as a garnet-type solid-state electrolyte with high ionic conductivity and good stability against lithium metal anode, which is regarded as one of the most promising electrolytes for the commercialization of solid-state batteries (SSBs). However, the poor electron and ion transport among cathode active material particles, as well as the large interfacial impedance between LLZTO ceramic pellet and cathode, remain major issues for SSBs. In this work, we proposed a novel 3D gel cathode based on the “cation-π” interaction between the organic cations in ionic liquid (IL) and the large electron-rich π-system in single-walled carbon nanotubes (SWNTs). The designed gel cathode, which is composed of SWNTs, IL and LiFePO4 (LFP) without binder, possesses a good wettability with the LLZTO ceramic pellet and affords highly efficient conductive pathways for electrons and ions through the interface and entire cathode. As a consequence, the assembled SSBs with the gel cathode exhibit excellent long-term cycling stability with a high capacity retention of 91.74% after 700 cycles at 0.5C, and a high coulombic efficiency close to 100% can be achieved over the course of cycling at 25 °C.

Ni-rich cathode material with isolated porous layer hindering crack propagation under 4.5 V high cut-off voltage cycling

This study reports on a preparation of novel Ni-rich cathode material with isolated porous layer and its application into cathode in lithium ion batteries extending cut-off potential into 4.5 V. Using intermittent addition of Al salt during co-precipitation of NixCo1-x(OH)2 (0 < x < 1), the isolated porous layer is easily formed inside the final active material particles maintaining overall mechanical integrity and their spherical shape without the change of external particle morphology. Even under severe cut-off potential of 4.5 V, volume expansion/contraction by anisotropic mechanical stress from hexagonal 2 to 3 (H2 → H3) phase transition is greatly reduced by hindering inner particle crack propagation into the external area at particle surface. Due to this phenomena, 227 mAh/g initial capacity at 0.1C was obtained upon 86 mol% of Ni content, with 75 % cathode capacity retention after 100 cycles under 1C, which is highest available capacity value among ever reported. Under full cell configuration, capacity retention at 100 cycles was 77 % and total available energy was increased into 15 % when compared with normal cycling condition of 4.3 V cut-off. From microtomic transmission electron microscope analysis, the porosity of inner particle was maintained as low as 6.67 % under 12 % increase of average primary particle size even after 100 cycles under 4.5 V cut-off voltage. From our advanced utilization of capacity and cut-off voltage, available energy in full cell application of our Ni-rich cathode material exhibited 20 % increase when compared with 4.3 V cut-off voltage.

Design of active-material/solid-electrolyte composite particles with conductive additives for all-solid-state lithium-ion batteries

All-solid-state lithium-ion batteries (ASSLIBs) are promising candidates for next-generation electric vehicle batteries. The contact interface between the active material (AM) and solid electrolyte (SE) is an important factor that affects the performance of ASSLIB. Composite particles, which are SE-coated AM particles, can form electrodes with large AM-SE contact interfaces. However, they can decrease in cell capacity because of the SE coating layer with electrical non-conductance. This study designed composite particles with conductive additives (CAs) using dry-coating. Acetylene black (AB) and vapor-grown carbon fiber (VGCF) were used as typical CAs, and the composite particles with these CAs were compared with those without CAs and simple mixture. Although the addition of CAs improved the cell capacity and decreased internal resistance, the type of CA significantly affected the rate performance. Because the VGCFs were barely incorporated into the SE coating layer, the incorporation of VGCFs did not improve the rate performance. However, the ABs were effectively incorporated into SE coating layer, resulting in the best rate performance in this study. This difference was due to the ease of supplying electrons to the AM particles. Therefore, AB was suitable for the CA of the composite particles to improve the performance of the ASSLIB.

Lithium ion battery electrode manufacturing model accounting for 3D realistic shapes of active material particles

The demand for lithium ion batteries (LIBs) in the market has gradually risen, with production increasing and expected to be boosted through the massive emergence of gigafactories. To meet industrial needs, the development of digital twins designed to accelerate the optimization of LIB manufacturing processes is essential. We report here a new three-dimensional physics-based modeling workflow able to predict the influence of manufacturing parameters on the electrode microstructure. This novel modeling workflow accounts for real active material particle shapes obtained from X-ray micro-computed tomography, upgrading our previous models where the particles were considered to be spherical. The modeling workflow is supported on Coarse-Grained Molecular Dynamics simulating the slurry, its drying and the calendering of the electrode resulting from the drying simulation. This model enables to link the manufacturing parameters with the real microstructure of the electrodes and to better observe the effect of the former on the heterogeneity of the electrodes. By using as user case electrodes containing LiNi0.33Co0.33Mn0.33O2 as active material, the simulations allow us, among others, to observe the alteration of the electrode heterogeneity during the manufacturing process and the deformation of the secondary particles of active material.

Simulation-Based and Data-Driven Techniques for Quantifying the Influence of the Carbon Binder Domain on Electrochemical Properties of Li-Ion Batteries

Most cathode materials for Li-ion batteries exhibit a low electronic conductivity. Therefore, a considerable amount of conductive additives is added during electrode production. A mixed phase of carbon and binder provides a 3D network for electron transport and at the same time improves the mechanical stability of the electrodes. However, this so-called carbon binder domain (CBD) hinders the transport of lithium ions through the electrolyte and reduces the specific energy of the cells. Therefore, the CBD content is an important design parameter for optimal battery performance. In the present study, stochastic 3D microstructure modeling, microstructure characterization, conductivity simulations as well as microstructure-resolved electrochemical simulations are performed to identify the influence of the CBD content and its spatial distribution on electrode performance. The electrochemical simulations on virtual, but realistic, electrode microstructures with different active material content and particle size distributions provide insights to limiting transport mechanisms and optimal electrode configurations. Furthermore, we use the results of both the microstructure characterization and electrochemical simulations to deduce extensions of homogenized cell models providing improved predictions of cell performance at low CBD contents relevant for high energy density batteries.

(Invited) Artistic: An AI and Modeling-Supported Digital Infrastructure for Battery Manufacturing Optimization

Energy, power, lifetime and safety of Lithium ion batteries (LIBs) are determined in part by the internal microstructure of the electrodes. That microstructure is characterized by the spatial location and the resulting interfaces between the active material particles, the conductive additive, the binder and the pores. The microstructure is determined by the manufacturing process of the electrodes, which encompasses, in its traditional wet form, multiple steps and numerous parameters. Therefore, its optimization is difficult and can be time consuming and costly if carried out only on the basis of a trial and error approach.In this lecture I discuss a digital infrastructure for accelerated optimization of the manufacturing process of LIBs that we are developing since few years: ARTISTIC.1 Such digital infrastructure is supported on a hybrid approach encompassing a physics-based multiscale modeling workflow, Artificial Intelligence (AI)/machine learning models and high throughput experimental characterizations.2 ARTISTIC simulates different steps along the battery cells manufacturing process, such as the electrode slurry preparation, the coating, the drying, the calendering and the electrolyte infiltration. For that purpose, it uses a combination of sequentially-coupled 3D-resolved physical models based on experimentally-validated Coarse Grained Molecular Dynamics, Discrete Element Method and Lattice Boltzmann Method. This allows predicting the impact of the manufacturing process parameters on the final electrode microstructure in three dimensions. The predicted electrode microstructures are then injected in a continuum performance simulator capturing the influence of the electrode microstructure on the solid electrolyte interphase formation (for anodes) and the electrochemical response (of anodes vs. lithium, cathodes vs. lithium and the full cells). Machine learning models are used to unravel manufacturing parameters interdependencies from the physical models’ predictions and experimental data, and to suggest manufacturing process optimizations. The predictive capabilities and chemistry-neutrality of the ARTISTIC digital infrastructure are illustrated with results for different LIB electrode formulations and chemistries (NMC, LFP, graphite, silicon/graphite blends) and also for organic active materials for sodium ion batteries. Finally, I discuss the free online battery manufacturing simulation services (online caculator and associated databases) offered by our project and that you can use interactively from your Internet Browser.3

Enhanced Structural Stability and Capacity Retention of Ni-Rich LiNi0.91Co0.06Mn0.03O2 Cathode Material By Dual Doping and Coating for Libs

Nickel-rich layered cathode material has been received a lot of attention due to their superior cycle-ability, high energy density and improved safety. However, there are some issues which are needed to be resolved to ensure the long term application. The hostile attack of electrolyte with the charged cathode electrode results in the growth of thick solid electrolyte interphase (SEI) at the expense of Li+ consumption and increase in interfacial resistance. In addition, de/intercalation of Li+ leads to the continuous contraction and expansion of lattice structure that leads to the crack formation in the active material particles during extended cycling.In this work, a facile technique has been adopted to resolve the mentioned problems. In this study, Li3BO3 has been coated on the NCM surface to protect the active material against the continuous attack of electrolyte and boron is doped to enhance the structural stability of LiNi0.91Co0.06Mn0.03O2 NCM cathode material. The samples were characterized by XPS, XRD, SEM and TEM and the electrochemical properties were measured by assembling the coin cells. The XRD results confirm the shifting of (003) diffraction peak towards low angle which validates the boron doping in the crystal structure. The presence of B1s is confirmed on the surface of modified NCM by XPS analysis. The FETEM images shows a uniform and distinct coating layer of 12 nm on the surface of 0.05 wt% coated NCM. The 0.05 wt% NCM samples offers the highest discharge capacity of 215.3 mAh g-1 at 0.1C and capacity retention of 81.6% at 0.5C (1C = 202 mA g-1) after 100 cycles. The reason behind enhanced cycling is the high bond dissociation energy of B−O (ΔHf298 = 402 kJ mol−1) than Ni–O (ΔHf298 = 391.6 kJ mol−1), Co–O (ΔHf298 = 368 kJ mol−1) and even Mn–O (ΔHf298 = 402 kJ mol−1). Even at 2C cycling, LBO-0.05 NCM sample demonstrated a capacity retention of 79.4% after 100 cycles while pristine shows only 67.3%. The modified samples displayed superior rate performance as compare to pristine NCM, especially at high current density. The cyclic voltammetry and EIS results are in-line with the cycling data. The presence of B3+ doping in host structure and Li3BO3 coating on the NCM surface results in the superior electrochemical performance of modified NCM.

Understanding the Effects of the Mixing Processes on the Performance of NMC-LMO Blend Electrodes Made By a Dry Electrostatic Spray Deposition Process

Improving the manufacturing process of making lithium-ion batteries (LIBs) is a key to further decreasing the cost and expanding the market of LIBs for many applications, especially for electric vehicles. Since electric vehicles require durable, sustainable, and cost-effective battery systems for their continued enlargement, advanced manufacturing processes of LIBs need to be investigated. The conventional wet slurry operation for LIB electrode manufacturing imposes several limitations on cost and performance mostly due to solvent usage. The drying process for the evaporation and recovery of organic solvent requires the use of unwanted solvents that do not contribute to the final product, thus consuming energy. If solvent evaporation is not controlled well, issues such as binder migration, segregation, and cracking of the electrode can occur, affecting the performance of the battery. Therefore, using a solventless dry process for electrode manufacturing has the potential to reduce the cost and environmental impact by eliminating solvent usage.In this work, electrostatic spray deposition (ESD) without the use of a solvent is investigated for manufacturing thick NMC811/LMO electrodes. Comparing two different dry powder mixing methods, we showed that dry powder mixing prior to ESD has a significant effect on the electrode microstructure and, consequently, its performance. Electrodes made by ball mill mixing retained better discharge capacity, which was attributed to the low charge transfer resistance and improved ionic conductivity due to porous conductive pathways formed between and on the active material particles. High speed mixing, on the other hand, caused dense layers of binder and conductive agent agglomerates, limiting the contact area of the electrolyte with active materials and increasing the resistance.

(Digital Presentation) Prediction of an in-Plane Anomalous Current Using Numerical Simulation and Machine Learning

Even normally shipped batteries may contain disturbing factors such as very small amounts of foreign matter or structural inhomogeneity, which can cause serious accidents such as thermal runaway or explosions. Since dismantling and identifying the cause is time-consuming and costly, nondestructive techniques for identifying the cause are required. A method for detecting abnormal current distribution by magnetic field inverse analysis has been proposed as one such method, but it is difficult to directly elucidate the factors that cause the abnormal current distribution itself. In this study, we first focused on the effect of different separator structures and analyzed the in-plane directional current distribution using machine learning in order to construct a non-destructive model for estimating the causes.A one-dimensional model based on porous electrode theory [1] was used. Constant current charging, homogeneous electrode layer structure, uniform Li concentration in active material particles, and isothermal conditions were assumed. The electrode layer was assumed to be a porous body consisting of active material, electrolyte, and auxiliary materials (conductivity assistant and binder). Using the previously reported structural information and physical properties [2], [3], Case 1 was a coin cell using LiNi1/3Co1/3Mn1/3O2 as the cathode active material, and Case 2 was a laminated cell using LiCoO2 as the cathode active material. The anode active material was graphite and the electrolyte was 1.0 M LiPF6 solution in EC・DEC solvent for both Case 1 and 2. The degree of flexure of the cathode and anode was determined using the formulas from previous studies [4]. Cross-sectional images of the actual biaxially oriented separator were obtained using a focused ion beam scanning electron microscope, and the three-dimensional simulated structure was reproduced based on these images (Sep. A). Similarly, a nonwoven fabric structure (Sep. B) and a foam structure (Sep. C) were also reproduced.Since the collector foils are connected in-plane, the potentials at both ends of the cell must be uniform. Under this constraint, the ion current distribution can be estimated depending on the in-plane structure distribution of the separator. In this study, the correlation between the local porosity (ε) of the separator and the local ion current (denoted as C-rate) was determined using a nonlinear regression method called Support Vector Regression (SVR) [5]. 100 points were taken randomly from 0.4~1.0 and 5~10 for ε and C-rate, respectively, and used as explanatory variables. Each charging curve was compared with the charging curve at the in-plane mean value of (ε, C) = (0.545, 7.5), and the RMSE (root mean square error) of the voltage was calculated as the objective variable.The in-plane reaction distribution was obtained from the voltage error predicted from ε and C-rate by SVR and the porosity distribution of the separator. The mesh size was 40 nm/pixel. For each separator, the difference between high and low reaction profiles was more clearly observed in Case 2. The reaction overvoltage distribution at a certain point in Case 2 was acquired, and it was confirmed that the reaction was concentrated near the separator of the negative electrode. This also made it possible to estimate the Li deposition point, which is the starting point of degradation.Using machine learning to analyze the in-plane current distribution, it was found that the current distribution differs depending on the electrode conditions even for the same separator. We will use this technology to develop a technique for identifying factors based on the current distribution obtained by nondestructive measurement.

Dynamic Multi-Dimensional Numerical Transport Study of Lithium-Ion Battery Active Material Microstructures for Automotive Applications

Conventional porous electrode battery modeling for a variety of applications makes assumptions to reduce the complexity of the simulation where tradeoffs between computational complexity and electrode detail can be realized without significantly impacting the accuracy of the results. The most common porous electrode battery model is the pseudo-two-dimensional (P2D) model as popularized by Newman and colleagues. These porous electrode battery models typically focus on simulating gradients in two dimensions; the primary dimension through the thickness of the battery cell electrodes and separators, and the secondary dimension in the radial direction of spherical active material particles. The particles are distributed throughout what is assumed to be a homogeneous porous electrode domain. Typically, uniformity in particle size, porosity, and tortuosity is assumed.In this work, the development of a three-dimensional microstructure (3DMS) lithium-ion battery model will be presented. With the increase in computational resources available in academia and industry, simulation of the microstructure in 3D is possible. Active material domains of both the anode and cathode can be generated stochastically to create microstructures representing the electrodes, with voids surrounding the particle representing the electrolyte. A comparison between the P2D and 3DMS models with sensitivity analysis focused on items that can be probed with microstructure simulations will be discussed and similarities and/or differences in charge/discharge characteristics, overpotentials, and concentration profiles will be presented. The findings from this work will provide a path to simulate at the microstructure level, drive electrode design, and translate the effects of heterogeneity into a homogenous porous electrode model.

Molten Salt Synthesis of High-Performance Cobalt Free Lithium Excess Cathodes

The cobalt free lithium excess chemistry cathode material of the compositional series Li[NixLi(1/3-2x/3)Mn(2/3-x/3)]O2 despite its high capacity has many shortcomings, such as voltage fade, poor materials stability, and poor rate capability 1–10. Our past investigations, among others, have highlighted the importance of the synthetic route on the on the performance of this material 6,11–13. This investigation found a novel synthesis route for Li[NixLi(1/3-2x/3)Mn(2/3-x/3)]O2 (x = 0.25) involving the use of molten salts during the 900 °C synthesis step would reduce the degree of voltage fade seen in materials cycling, and increase the overall stability of the material over the course of cycling. Our samples we prepared using a standard sol-gel approach where the post 500 °C precursor oxide was mixed with NaCl, Li2SO4, or LiNO3, before the final 900 °C calcination, all samples where then rapidly water quenched to stabilize the meta-stable materials phase, but also to dissolve any residual salts and wash the powders before use. These salts were selected due to their different chemistries and molten ranges. NaCl is thermodynamically and chemically stable enough where it likely functioned as an observer species, and Li2SO4 and LiNO3 could have served as additional lithiation sources. Thermogravimetric analysis was used to help determine the behaviors of these salts through range for each salts’ molten regime as well as to help determine any salt behaviors up to 900 °C; compared to the control sample NaCl sample was found to have rapid mass lost starting at 850 °C; Li2SO4 was found to cause less mass loss than the control sample; LiNO3 had rapid mass lost starting at 600 °C when compared to the control sample, suggesting a shorter window of molten-salt synthesis environment. Galvanostatic testing revealed that each molten salt sample had distinct electrochemical behaviors, and many had enhanced voltage and capacity stability. Analysis of the samples surfaces through the use of high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), energy dispersive spectroscopy (EDS), suggest the formation of doped surface facets, and changes in the preferred facet orientation of samples. These methods also revealed that the molten salt synthesis conditions can lower the diffusion barrier between active material particles encouraging Ostwald ripening, as well as increased batch homogeneity.Sources: C. R. Fell et al., Chemistry of Materials, 1621–1629 (2013).Z. Lu, L. Y. Beaulieu, R. A. Donaberger, C. L. Thomas, and J. R. Dahn, Journal of The Electrochemical Society, 149, A778–A791 (2002).Y. Wu and A. Manthiram, Electrochemical and Solid-State Letters, 9, A221–A224 (2006).Z. Lu and J. R. Dahn, Journal of The Electrochemical Society, 149, A1454–A1459 (2002).N. Dupré, M. Cuisinier, E. Legall, D. War, and D. Guyomard, Journal of Power Sources, 299, 231–240 (2015).K. A. Jarvis et al., Acta Materialia, 108, 264–270 (2016).J. Wang et al., Int. J. Electrochem. Sci, 11, 333–342 (2016).M. Jiang, B. Key, Y. S. Meng, and C. P. Grey, Chemistry of Materials, 21, 2733–2745 (2009).J. Bréger et al., J Am Chem Soc, 127, 7529–7537 (2005).Y. J. Park, Y.-S. Hong, X. Wu, K. S. Ryu, and S. H. Chang, Journal of Power Sources, 129, 288–295 (2004).S. Burke and J. F. Whitacre, Journal of The Electrochemical Society, 167, 160518 (2020).S. Hy et al., Energy and Environmental Science, 9, 1931–1954 (2016).S. Laubach et al., Physical Chemistry Chemical Physics, 11, 3278–3289 (2009). Figure 1

How Does Mg Transport in MgCr2O4 - a Cathode Active Material?

Conventionally, we expect the transport of intercalated species in battery active particles is limited by diffusion. MgCr2O4 has been identified as a candidate active material for the Mg batteries based on its theoretical Mg-storing capacity, high open circuit potential, and acceptable diffusion barrier for Mg-ion transport (1,2). However, when operated electrochemically, its performance does not match the promised potential (3). Motivated by these observations, we examine charge transport in dense MgCr2O4 pellets in an electrolyte-free setup to conclusively probe bulk Mg transport. We find that the ion transport in this material cannot be explained by using the conventional understanding. We propose a new theory that extends the conventional picture and accounts for the unusual behavior in MgCr2O4 (4). We further discuss the implications of this understanding for engineering active material particles in MgCr2O4 porous electrodes. References Canepa, P.; Sai Gautam, G.; Hannah, D. C.; Malik, R.; Liu, M.; Gallagher, K. G.; Persson, K. A.; Ceder, G. (2017) "Odyssey of Multivalent Cathode Materials: Open Questions and Future Challenges." Chem. Rev., 117 (5), 4287–4341. DOI: 10.1021/acs.chemrev.6b00614.Bayliss, R. D.; Key, B.; Sai Gautam, G.; Canepa, P.; Kwon, B. J.; Lapidus, S. H.; Dogan, F.; Adil, A. A.; Lipton, A. S.; Baker, P. J.; Ceder, G.; Vaughey, J. T.; Cabana, J. (2020) "Probing Mg Migration in Spinel Oxides." Chem. Mater., 32 (2), 663–670. DOI: 10.1021/acs.chemmater.9b02450. Hu, L.; Johnson, I. D.; Kim, S.; Nolis, G. M.; Freeland, J. W.; Yoo, H. D.; Fister, T. T.; McCafferty, L.; Ashton, T. E.; Darr, J. A.; Cabana, J. (2019) "Tailoring the Electrochemical Activity of Magnesium Chromium Oxide towards Mg Batteries through Control of Size and Crystal Structure." Nanoscale, 11 (2), 639–646. DOI: 10.1039/C8NR08347A. Johnson, I.D.; Mistry, A.; Yin, L.; Murphy, M.; Wolfman, M.; Fister, T. T.; Lapidus, S. H.; Cabana, J.; Srinivasan, V.; Ingram, B. J. (2022) "Investigating Charge Transport in MgCr2O4 Extends the Understanding of Battery Intercalation Hosts.", under review

(Digital Presentation) 3D Electrochemical Model Revealing Electrode Manufacturing Parameters’ Effects on Battery Performance

Electrode manufacturing is in the core of Li-ion battery manufacturing process. The electrode mesostructure and the associated electrochemical performance is determined by the adopted manufacturing parameters. However, in view of the strong interdependencies between these parameters, evaluating their influence on the performance is not a trivial task, and our ERC-funded ARTISTIC project1,2 is providing a theoretical framework to rationalize and optimize the manufacturing process of Li-ion battery cells. Over the years, the discussion of importance of electrode mesostructure in cell behavior has become increasingly lively. Many modeling researchers have been conducted studies to explain the influences of electrode mesostructure on its electrochemical performance3–6. However, many studies did not include manufacturing parameters as inputs, which hinders universality in regards of these electrochemical models’ application. With the aim of going into the scope of real electrode manufacturing parameters, we present here a calibrated 3D-resolved electrochemical model for NMC111-electrodes which reveals how slurry formulation and compression rate affect the electrode performance. A series of electrodes with different formulations and compression rates were manufactured. Corresponding models were built based on the basis of these manufacturing parameters, using the manufacturing process simulation workflow previously developed in ARTISTIC7. The results of simulations and experiments were compared individually. We found that one of the major factors affecting the electrode performance is the carbon-binder domain (CBD) distribution, which highly changes the conductive network within the electrode. A well-connected conductive network throughout the electrode is vital for ensuring full utilization of active material. Other features such as porosity, tortuosity factor, active material particle packing, and etc. also play important roles in different ways. This work provides systematic insights on the essence of how electrode manufacturing process takes effect on electrode performance, through a digital twin experimentally validated under multiple experimental conditions.References Artistic http://www.erc-artistic.eu/. Artistic http://www.erc-artistic.eu/scientific-production/publications.X. Lu et al., Energy Environ. Sci., 14, 5929–5946 (2021).M. E. Ferraro, B. L. Trembacki, V. E. Brunini, D. R. Noble, and S. A. Roberts, J. Electrochem. Soc., 167, 013543 (2020).X. Lu et al., Nat. Commun., 11, 2079 (2020).L. S. Kremer et al., Energy Technol., 8, 1900167 (2020).T. Lombardo et al., Batter. Supercaps, 5, e202100324 (2022).

On Accuracy of Porous Electrode Design in the Presence of Negative Effects of Carbon-Binder Networks

Porous electrodes for Li-ion batteries are composed of energy storing active material particles, carbon-binder networks, and electrolyte filled pores 1. The carbon-binder networks improve the electronic conduction through the porous electrode, and are expected to improve electrode performance at finite currents. Accordingly, the porous electrode designs treat carbon-binder networks as a positive influence. In this talk, by using systematic experiments of electrochemical performance for different electrode compositions, we will show that the carbon-binder networks also exhibit negative effects 2. These negative effects deteriorate performance by decreasing the area available for intercalation reaction as well as increasing the resistance to ion transport. These effects are prominent for electrodes even with low carbon-binder content, e.g., 5%wt (of dry electrode). We will discuss the implications of these results in the context of predicting porous electrode performance 3, and in turn, designing these electrodes for different operations. Liu et al. (2012) Particles and Polymer Binder Interaction: A Controlling Factor in Lithium-ion Electrode Performance, J. Electrochem. Soc. 159(3), pp. A214-A221, https://doi.org/10.1149/2.024203jes Mistry et al. (2021) Quantifying Negative Effects of Carbon-binder Networks from Electrochemical Performance of Porous Li-ion Electrodes, J. Electrochem. Soc. 168(7), 070536, https://doi.org/10.1149/1945-7111/ac1033 Doyle, Fuller & Newman (1993) Modeling of Galvanostatic Charge and Discharge of Lithium/Polymer/Insertion Cell, J. Electrochem. Soc. 140(6), pp. 1526-1533, https://doi.org/10.1149/1.2221597 Figure 1

Evaluating Kinetics of Composite Cathodes of All-Solid-State Batteries

ASSBs (all-solid-state batteries) are promoted as an energy dense and safe alternative to current Li-ion batteries (LIBs) and attract great interest from academia and industry. In contrast to LIBs, which employ a liquid organic electrolyte, they utilize a solid electrolyte. This substitution promises to eliminate the flammability of the battery and to simplify the cell design.While recent research efforts have concentrated on miniaturizing and eventually even removing the anode host material in batteries, the relative portion of the cathode needs to be maximized, as cathodes are the only component that can increase energy density by increasing its fraction. In a simplified view, the cathode kinetics are determined by the cathode microstructure, the volume fractions of the constituents and the properties of electrolyte and cathode active material (CAM).Liquid electrolytes can easily penetrate porous composite cathodes, but rigid SEs can not do the same, resulting in residual porosity in the cathode. This porosity can lower active interface area between CAM and SE, and increase tortuosity of ionic and electronic charge transport pathways. Sufficient ionic and electronic transport pathways in composite cathode structures are, however, essential because cathode active material particles that are either electronically or ionically isolated cannot contribute to the charging or discharging process.We analyse the requirements for SSB cathodes and determine charge transport bottlenecks by impedance spectroscopy of a reference system consisting of a thiophosphate based solid electrolyte and a nickel rich layered CAM. Different cathode microstructures are analysed and their charge transport properties are quantified as partial conductivities. From the obtained partial conductivities, we calculated tortuosity factors and correlated them to cell performance with complementary cycling data of all-solid-state batteries in order to determine charge transport bottlenecks. We find, that ionic charge transport and consequently cathode kinetics are highly dependent on the SE particle size distributionIn addition, we analyse the requirements for CAMs for SSBs and develop design principles for different CAM types that aim to further increase cathode performance.

Important Impact of the Slurry Mixing Speed on Water-Processed Li4Ti5O12 Lithium-Ion Anodes in the Presence of H3PO4 as the Processing Additive.

The aqueous processing of lithium transition metal oxides into battery electrodes is attracting a lot of attention as it would allow for avoiding the use of harmful N-methyl-2-pyrrolidone (NMP) from the cell fabrication process and, thus, render it more sustainable. The addition of slurry additives, for instance phosphoric acid (PA), has been proven to be highly effective for overcoming the corresponding challenges such as aluminum current collector corrosion and stabilization of the active material particle. Herein, a comprehensive investigation of the effect of the ball-milling speed on the effectiveness of PA as a slurry additive is reported using Li4Ti5O12 (LTO) as an exemplary lithium transition metal oxide. Interestingly, at elevated ball-milling speeds, rod-shaped lithium phosphate particles are formed, which remain absent at lower ball-milling speeds. A detailed surface characterization by means of SEM, EDX, HRTEM, STEM-EDX, XPS, and EIS revealed that in the latter case, a thin protective phosphate layer is formed on the LTO particles, leading to an improved electrochemical performance. As a result, the corresponding lithium-ion cells comprising LTO anodes and LiNi0.5Mn0.3Co0.2O2 (NMC532) cathodes reveal greater long-term cycling stability and higher capacity retention after more than 800 cycles. This superior performance originates from the less resistive electrode-electrolyte interphase evolving upon cycling, owing to the interface-stabilizing effect of the lithium phosphate coating formed during electrode preparation. The results highlight the importance of commonly neglected─frequently not even reported─electrode preparation parameters.

Investigation of the diffusion phenomena in lithium-ion batteries with distribution of relaxation times

The distribution of relaxation times method (DRT) has been widely used to quantify the numbers and characterize the properties of the physico-chemical processes inside the Li-ion battery (LIB). While most of the published works focused on the mid-high frequency range, the processes in the low frequency area, such as diffusion, have garnered less attention. The difficulties of applying the DRT to the diffusion processes include the more complicated mathematical treatment involved, the unknown influence of the porous electrode on the DRT spectra and the evaluation of the measured impedance with the developed theory. The galvanostatic intermittent titration technique (GITT) has been widely applied to determine the solid diffusion coefficient for the LIB. However, the GITT does not consider the geometry of the active material particles and cannot effectively separate the contribution of the solid diffusion from other processes, such as liquid diffusion. In the present work, a comprehensive theory is developed to investigate the DRT spectra of a LIB with a physics-based impedance model. Furthermore, an analytical expression is developed for the DRT spectra and analyzed in detail. The developed theory can help to determine the solid phase diffusion coefficient with a firm physico-chemical background. Based on the developed theory, the solid diffusion coefficients of the silicon graphite (SiC) and NMC811 are determined with a commercial cell. Besides, the galvanostatic intermittent titration technique (GITT) has been applied to the same cells and the measurement results are compared with that using the DRT method. The comparison indicates that GITT cannot exclude the influence of the liquid diffusion and the solid diffusion coefficients will be underestimated.

Multi-scale analysis of cathode microstructural effects on electrochemical and stress responses of lithium-ion batteries

The electrochemical and stress responses of lithium-ion batteries (LIBs) are highly dependent on the three-dimensional (3D) microstructure of electrodes, and substantial fundamental research is required to optimize the electrode design for high-energy, high-power LIBs with fast charging capabilities. Herein, we report a multi-scale LIB model that enables the examination of full-cell battery performance while investigating the detailed electrochemical and stress responses of the cathode using the variational multi-scale enrichment method. With the high computational efficiency of the developed model, the cathode microstructural effects were studied systematically by varying the particle size, volume fraction, and particle arrangement of 3D cathode microstructures at different C-rates. The results show that the arrangement of active material particles and their interconnectivity, rather than the particle size itself, are the determining factors for the spatial lithium-ion concentration and stress distribution of the cathode, affecting the overall electrochemical performance of LIBs. Our study provides valuable insights into the design and optimization of the cathode architecture to maximize the electrochemical performance under different operating conditions.