Influence of Electrode Structuring Techniques on the Performance of All-Solid-State Batteries

All-solid-state batteries (ASSBs) offer a promising route to safer batteries with superior energy density compared to conventional Li-ion batteries (LIBs). However, the design of the composite cathode and optimization of the underlying microstructure is one of the aspects requiring intensive research. Achieving both high energy and power density remains challenging due to limitations in ionic conductivity and active material loading. Using structure-resolved simulations, we investigate the potential of perforated and layered electrode designs to enhance ASSB performance. Design strategies showing significant performance increase in LIBs are evaluated regarding their application to ASSBs. Composite cathodes with solid electrolyte channels in the structure do not significantly increase cell performance compared to unstructured electrodes. However, the design with a two-layer cathode proves promising. The layered structure effectively balances improved ionic transport due to increased solid electrolyte fraction at the separator side and substantial active material loading through increased active material fraction at the current collector side of the cathode. Our research highlights key challenges in ASSB development and provides a clear direction for future studies in the field.Comment: 46 pages, 15 figure

Optimizing the Composite Cathode Microstructure in All-Solid-State Batteries by Structure-Resolved Simulations

All-solid-state batteries are considered as an enabler for applications requiring high energy and power density. However, they still fall short of their theoretical potential due to various limitations. One issue is poor charge transport kinetics resulting from both material inherit limitations and non-optimized design. Therefore, a better understanding of the relevant properties of the cathode microstructure is necessary to improve cell performance. In this article, we identify optimization potentials of the composite cathode by structure-resolved electrochemical 3D-simulations. In our simulation study, we investigate the influence of cathode active material fraction, density, particle size, and active material properties on cell performance. Special focus is set on the impact of grain boundaries on the cathode design. Based on our simulation results, we can predict target values for cell manufacturing and reveal promising optimization strategies for an improved cathode design

Effect of Particle Size and Pressure on the Transport Properties of the Fast Ion Conductor t‐Li₇SiPS₈

All‐solid‐state batteries promise higher energy and power densities as well as increased safety compared to lithium‐ion batteries by using non‐flammable solid electrolytes and metallic lithium as the anode. Ensuring permanent and close contact between the components and individual particles is crucial for long‐term operation of a solid‐state cell. This study investigates the particle size dependent compression mechanics and ionic conductivity of the mechanically soft thiophosphate solid electrolyte tetragonal Li₇SiPS₈ (t‐LiSiPS) under pressure. The effect of stack and pelletizing pressure is demonstrated as a powerful tool to influence the microstructure and, hence, ionic conductivity of t‐LiSiPS. Heckel analysis for granular powder compression reveals distinct pressure regimes, which differently impact the Li ion conductivity. The pelletizing process is simulated using the discrete element method followed by finite volume analysis to disentangle the effects of pressure‐dependent microstructure evolution from atomistic activation volume effects. Furthermore, it is found that the relative density of a tablet is a weaker descriptor for the sample's impedance compared to the particle size distribution. The multiscale experimental and theoretical study thus captures both atomistic and microstructural effects of pressure on the ionic conductivity, thus emphasizing the importance of microstructure, particle size distribution and pressure control in solid electrolytes

Testing for taxonomic bias in the future diversity of Australian Odonata

Aim Invertebrates are often overlooked in assessments of climate change impacts. Odonata (dragonflies and damselflies) are a significant component of freshwater macroinvertebrate diversity and are likely to be highly responsive to a changing climate. We investigate whether climate change could lead to significant alteration of continental patterns of diversity and whether vulnerable species are taxonomically clustered. Location Australia. Methods Habitat suitability of 270 odonate species was modelled, and a simplified phylogeny was developed based on taxonomic relationships and expert opinion. These maps were then combined to compare species richness, endemism, taxonomic diversity (TD) and taxonomic endemism (TE) under climate change scenarios, and estimate turnover in species composition. Based on the concentration of vulnerable species in regions associated with Gondwanan relicts, we tested the possibility that a focus on species loss would underestimate loss of evolutionary diversity. Results Species richness of Australian Odonata is concentrated in the Wet Tropics, central‐north Australia and south‐east Queensland. Several additional regions support endemic assemblages, including the Victorian alpine region, the Pilbara and far south‐western Australia. Major shifts in composition are expected across most of the east coast in response to climate change, and Tasmania has the potential to become a major refuge for mainland species. For many regions, the loss of TD is greater than expected based on the changes in species richness, and the loss of suitable habitat was unevenly distributed among families. However, the potential loss of evolutionary diversity among vulnerable species was not significantly different from random. Main conclusions The major shifts in the distribution of Australian odonate diversity predicted to occur under climate change imply major challenges for conservation of freshwater biodiversity overall. Although major evolutionary losses may be avoided, climate change is still a serious threat to Australia's Odonata and poses an even greater threat to Australian freshwater biodiversity as a whole

Identifying Limiting Processes in the Composite Cathode of All-Solid-State-Batteries by Structure-Resolved Simulations

All-solid-state batteries (ASSBs) are a promising technology for applications that demand high energy and power density. The utilization of solid electrolytes (SE) potentially enables the use of Li-metal anodes, theoretically providing a significant increase in energy density. However, practical values still fall short due to inadequate electrode design and degradation mechanisms. This is especially important for the composite cathode, which consists of a 3D-network of SE and cathode active material (CAM) particles. Cell performance is significantly influenced by the transport processes in the composite cathode that depend on its geometrical properties including CAM fraction, density and particle sizes. Additionally, interfacial stability issues between SE and CAM can lead to degradation phenomena during the manufacturing process and cycling of the cells [1,2]. Potentially, secondary phases can form a resistive layer and impede charge transfer at the interface. The additional charge transfer resistance is one explanation for the low measured cell capacity of garnet-based cells at room temperature [3]. In this contribution, we use structure-resolved simulations in the simulation framework BEST [4] to identify limitations of the cell performance. We focus on the optimization of the microstructure and correlate cell performance to geometrical properties of the composite cathode. This allows us to identify target values for the cell production regarding CAM fraction, sinter density as well as SE and CAM particle size. Additionally, we investigate the effect of secondary phases at the SE/CAM interface. In doing so, we can determine the influence on cell performance depending on the properties of the degradation products and provide possible explanations for the reduction in performance observed experimentally. References [1] Ihrig, M., Finsterbusch, M., Laptev, A. M., Tu, C. H., Tran, N. T. T., Lin, C. A., ... & Guillon, O. (2022). Study of LiCoO2/Li7La3Zr2O12: Ta interface degradation in all-solid-state lithium batteries. ACS applied materials & interfaces, 14(9), 11288-11299. [2] Vardar, G., Bowman, W. J., Lu, Q., Wang, J., Chater, R. J., Aguadero, A., ... & Yildiz, B. (2018). Structure, chemistry, and charge transfer resistance of the interface between Li7La3Zr2O12 electrolyte and LiCoO2 cathode. Chemistry of Materials, 30(18), 6259-6276. [3] Finsterbusch, M., Danner, T., Tsai, C. L., Uhlenbruck, S., Latz, A., & Guillon, O. (2018). High capacity garnet-based all-solid-state lithium batteries: fabrication and 3D-microstructure resolved modeling. ACS applied materials & interfaces, 10(26), 22329-22339. [4] Latz, A., & Zausch, J. (2011). Thermodynamic consistent transport theory of Li-ion batteries. Journal of Power Sources, 196(6), 3296-3302

Determining the limiting effect of secondary phases on the cell performance of all-solid-state-batteries by continuum modelling and simulation

All-solid-state-batteries (ASSB) are regarded as a key technology for future battery applications because they prepare the way towards higher energy densities and an increased safety in operation. A crucial part in the development of ASSB is the optimization of the solid electrolyte which determines battery capacity and cycling stability. Due to a high ionic conductivity and a wide electrochemical stability window, the ceramic LLZO garnet is a promising candidate. While providing high capacity at elevated temperature and low current densities, garnet-based ASSB still show a large polarization at room temperature [1]. Latter is attributed to secondary phases, formed due to high temperature exposure and electrochemical degradation of electrolyte and cathode active material (CAM) in the composite cathode. In our contribution, we investigate the limiting effect of secondary phases in the composite cathode by microstructural resolved modelling and simulation [2]. While it is challenging to experimentally determine properties and composition of existing secondary phases, simulations can elucidate the underlying processes and mechanisms. A model for a resistive film between electrolyte and CAM was implemented in the simulation framework. It takes into account the properties of a blocking layer resulting from degradation processes. Furthermore, we consider grain boundaries in the solid electrolyte and anisotropic properties of the CAM and, thus, are able to depict the complex charge transport in the composite cathode [3]. The underlying 3D-microstructure of the composite cathode is reconstructed from FIB-SEM-measurements in order to include the influence of structural properties like tortuosity and pore distribu- tion. Our results show the limiting effect of secondary phases on the cell performance. The slow Li-diffusion in the resistive layer between solid electrolyte and CAM limits the ion transfer across the LLZO/CAM interface which can lead to reduced CAM utilisation. For small assumed diffusivities of the secondary phases, the simulated capacities are in a similar range as measured in experiments

Identifying limiting factors on the cell performance of all-solid-state batteries by microstructural resolved simulations

All-solid-state batteries (ASSBs) are predicted to play an important role in future battery applications, because they potentially provide high energy densities and an enhanced safety in operation. The ceramic electrolyte LLZO is a promising choice for the solid electrolyte (SE), as it is stable against Li-metal and shows a high ionic conductivity which is essential for a high cell performance. However, experimental results still show low capacities for garnet-based ASSBs at room temperature and a severe capacity fade after the cycling of the cells. In this contribution we explore the reasons for the observed limitations and show possible optimization strategies by continuum modelling and simulations. First, we perform microstructural-resolved simulations on a set of virtual composite cathodes to identify the limitations of the underlying microstructure. In doing so we want to provide advantageous target values for the cell production regarding active material content, sinter density and particle sizes. Furthermore, we focus on the role of secondary phases in the composite cathode that can form as a result of degradation phenomena at the interface between the SE and cathode active material (CAM). By extending our simulation environment with an interface model, we show that a resistive layer at the interface SE/CAM resulting from secondary phase formation is a plausible explanation for the low measured capacities at room temperature. An increase in layer thickness when cycling the cell due to electrochemical degradation is a possible mechanism for the observed capacity fade

Microstructure-resolved modelling of solid-state batteries: The importance of anisotropy and secondary phases in the composite cathode

All-solid-state batteries are being considered to play an important role in future battery systems due to an increased safety in operation and the possible deployment of Li-metal at the anode of the cell. A promising candidate for the solid electrolyte is the garnet-type oxide LLZO, which shows a high stability towards Li-metal while providing a high ionic conductivity. However, thermal and electrochemical induced degradation of the electrolyte and active material in the composite cathode can lead to the formation of secondary phases, which hinder the lithiation of the active material and limit the cell performance. The optimization of the composite cathode is further complicated by the existence of grain boundaries in the electrolyte and anisotropic properties of the often- deployed layered oxides, which may show a preferential crystallographic orientation in the microstructure. In this contribution we investigate the influence of secondary phase formation and anisotropy of the cathode active material on the battery performance by continuum-modelling and simulation. By including an interface model in our simulation environment, we determine the limiting effect of existing secondary phases on the cell performance. Furthermore, we include anisotropic transport parameters for the active material to account for the hindered Li-transport in the direction of the crystallographic c-axis. Our results show a strong reduction of battery capacity due to secondary phases forming in the composite cathode. The slow Li-diffusion at the interface between active material and electrolyte results in an increasing blocking of the active material which could explain the small measured capacities at room temperature. While the anisotropic properties of the active material play a minor role for homogeneous composite cathodes with moderate active material fractions, there is a stronger effect when considering inhomogeneous microstructures. Longer diffusion paths resulting from an unfavourable particle orientation hinder the Lithiation of the active material and cause smaller capacities