Contact loss and its improvement at the interface between the cathode and solid electrolyte in all solid-state batteries based on multi-scale and multi-physics analysis

Abstract

All-solid-state battery (ASB) systems are considered a promising energy-storage system to advance the next generation of electronic devices. However, it is known that LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) as an electrode provokes a contact-loss problem at the interface with Li₁₀GeP₂S₁₂ (LGPS) as the solid electrolyte (SE). Also, the fundamental mechanism of contact loss has not been comprehensively described yet. For these reasons, we designed an electro-chemo-mechanical multi-scale and multi-physics model initially to examine the mechanism of contact loss. The electrochemical and mechanical properties of NCM811 and LGPS were calculated at the nanoscale. Then, the complex phenomenon of contact loss considering the electrochemical and mechanical physics was analyzed at the micro/macro scale together with the calculated properties. Using designed methodology bridging the nano scale and micro/macro scale with combined physics, we confirmed that the contraction of NCM811 during the charge directly leads to a swelling of LGPS. The compliant LGPS instantly absorbs the displacement fields from NCM811 and then undergoes crack generation at the interface. Contact loss limits the flow of Li ions and causes a short circuit. In addition, we confirmed that applying a polymer filler with hyperelasticity at the interface and external pressure to the cell can be considered as possible solutions to relieve the contact loss, and both remedies could effectively suppress the contact loss. The introduction of both remedies at the same time also showed synergetic effects, whereby applying a thin filler with external pressure could suppress contact loss as much as applying a thick filler.