Optimization Effect on the Interfacial Impedance and Contact Stress of the ASSLB with Porous Polymer Buffer Layer

The contact loss and interface impedance of all-solid-state lithium-ion batteries (ASSLBs) have greatly restricted their commercial applications. This study simulates the ASSLB composed of a LiNi_0.8Co_0.1Mn_0.1O₂ (NMC811) cathode, silicon–carbon composite (SiC) anode, and Li₁₀GeP₂S₁₂ (LGPS) solid electrolyte and analyzes the interfacial electrochemical and mechanical behavior. The electrical contact resistance and interface stress are obtained by the fractal network model and contact mechanics theory. According to the interface reaction kinetics and Nernst–Planck–Poisson equations, the analytical electric field of the space charge layer (SCL) in the case of symmetric carrier movement is acquired. In addition, the optimization effect of coating the porous poly(ethylene oxide) (PEO) layer on the interface is studied theoretically. Based on the equivalent circuit model (ECM), the electrochemical impedance spectra (EIS) of the whole cell are simulated by Comsol Multiphysics. To investigate the evolution of the SCL capacitance, the contact resistance, and the interfacial impedance, the relevant physical parameters are reasonably regulated. The results show that when the buffer layer of a higher initial porosity is taken with a thickness of 1.5–2.5 × 10^–7m, the interface stress can be relieved and the actual contact can be improved. What’s more, the relative permittivity of the solid electrolytes in the range of 10–50 can reduce the interfacial impedance as well.