High-performance PEO-based solid-state LiCoO2 lithium metal battery enabled by poly(acrylic acid) artificial cathode electrolyte interface

Solid-state lithium metal batteries (SSBs) have attracted ever-increasing attention because of the enhanced energy density and safety. However, the solid-solid contact resistance and interfacial stability pose a huge challenge in the practical application of SSBs. In this work, poly(acrylic acid) (PAA) is coated onto the LiCoO2 (LCO) cathode surface via a simple drop-casting method in SSB employing poly(ethylene oxide) (PEO)-based electrolyte to construct an artificial cathode electrolyte interface (ACEI). It proves that the ACEI can not only form percolating Li+ pathways across the electrode, but also protect the PEO electrolyte from being oxidized. Besides, Li+/H+ exchange reaction is found between LCO and PAA during the initial cycles, which further promote the interfacial ion transport and lead to enhanced battery kinetics. Galvanostatic charge/discharge and electrochemical impedance spectroscopy test indicate that the 0.5% PAA-treated LCO presents superior capacity retention of 93.3% after 120 cycles at 0.4 C when it works at 60 °C. PAA-LCO|PEO|Li pouch cells are also prepared and a reversible capacity of 145 mAh/g after 50 cycles at 0.1 C is achieved, which further demonstrates the feasibility of this strategy.