Strategic cathode configuration for incorporating sacrificial materials in all-solid-state batteries: Mixed vs. separate layer

Abstract

Cathode pre-lithiation is one of the key strategies to mitigate the high irreversibility in all-solid-state batteries (ASSBs). However, the decomposition of sacrificial material mixed with cathode active materials (CAM) creates voids and resistive by-products in the CAM layer, degrading performance. Here, we propose a strategy for reconfiguring a composite cathode structure with a Li3P sacrificial material to maximize the pre-lithiation effect. Our approach was to apply Li3P as a separate layer rather than mix it into CAMs, so that the CAMs are free from damage. The location of the sacrificial layer between the current collector and the CAM layer was critically important for efficient Li ion and electron transport to the CAM. The proposed configuration achieved a significantly enhanced pre-lithiation effect, resulting in effective compensation for the high irreversibility in ASSBs. The full cells with Si and Ag anodes that include a Li3P-layer demonstrated a 124 % (Si anode) and 261 % (5 μm Ag foil anode) increase in initial discharge capacity compared to cells without Li₃P. This study provides a simple solution for implementing high-energy-density but highly irreversible anodes in ASSBs.