Investigating Limiting Processes for the ElectrochemicalPerformance of Sulfidic All-Solid-State Batteries
2020
All-solid-state batteries (ASSB) are candidates for the next-generation of safe and high energy density
storage systems. However, energy and power density are currently limited by microscopic processes at
the interfaces as well as macroscopic processes on the cell level. As part of the FestBatt Cluster, we
explore the working principle of sulfidic ASSBs through a cross-platform approach combination of
theoretical and experimental methods.
In order to gain insight on the limiting processes and give directions for the development of future
ASSBs, we develop a numerical framework to capture the electrochemical processes by combining
thermodynamic consistent modelling [1] and microstructure resolved 3D simulations [2,3]. This
approach enables us to include virtual electrode reconstructions based on experimental measurements
to improve the simulation accuracy and account for additional material features.
The investigated sulfidic cell systems consist of the solid electrolyte s-LiPS4 and the nickel-rich
layered oxide NMC622 as active material. To account for the material inherent transport limitations in
the electrode, our model is further expanded through the introduction of state-of-charge dependent
transport parameters for conductivity and diffusivity. Furthermore, we account for percolating ion
transport pathways in the polycrystalline electrolyte by resolving the grain particles in the solid matter.
By introducing a modified interface flux at the grain particle interfaces the lithium ion hopping
probability between two neighbouring grains is captured. The introduced simulation framework allows
us a precise time resolved mapping of the cell performance for different cell designs, operation
conditions and material modifications.
We present a detailed study on the capacity density, the microscopic lithiation behaviour of sulfidic
cells under structural, and interfacial modification through conductive agents, solid electrolyte
delamination and current collector decontacting. The comparison against the experimental work
identifies various performance limiting processes e.g. discontinuous material properties and restricted
intercalation processes. Especially, the grain flux model allows to reproduce and identify the
experimentally observed impedance characteristics connected to solid electrolyte grain size and grain
surface effects. Our simulation based approach allows for a more economical and efficient testing of
new battery designs in order to enable high performance future ASSBs.
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