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. Poly(acrylic acid) is coated onto the LiCoO2 cathode surface via a simple drop-casting method in SSB employing poly(ethylene oxide)-based electrolyte to construct an artificial cathode electrolyte interface, achieving better electrochemical performance. Also, Li+/H+ exchange reaction is found between LCO and PAA upon cycling, which further promotes the interfacial ion transport and leads to enhanced battery kinetics. Schematic illustration of function of the Poly(acrylic acid) as an artificial cathode electrolyte interface. [Display omitted] •PAA is coated onto the LiCoO2 cathode surface via a simple drop-casting method to construct an artificial cathode electrolyte interface.•The PAA-modified batteries present a capacity retention of 93.3%. Pouch cells show a capacity of 145 mAh/g.•Li+/H+ reaction mainly happens in the initial cycles between LCO and PAA, which further promote the interfacial ion transport and battery kinetics.