Wet‐Processable Binder in Composite Cathode for High Energy Density All‐Solid‐State Lithium Batteries

Abstract Sulfide‐based all‐solid‐state lithium batteries (ASSLBs) are potential alternatives to conventional lithium‐ion batteries for enhancing energy density and battery safety. However, the industrial sector encounters technical challenges in the fabrication of high‐mass‐loaded composite cathodes to improve the energy densities of ASSLBs. Thus, the selection of an appropriate binder and cathode active material is very important for achieving a good cycling performance of ASSLBs. In this study, wet‐processable poly(ethylene‐co‐methyl acrylate‐co‐glycidyl methacrylate) (EMG) binder and full‐concentration gradient (FCG) LiNi 0.78 Co 0.10 Mn 0.12 O 2 (NCM) cathode active material are employed to fabricate the composite cathode with high active mass loading (21.4 mg cm −2 ). The EMG binder provided strong binding properties to the cathode constituents and improved the electrical conductivity of the composite cathode. The FCG NCM mitigated the morphology damages caused by volume changes in the cathode active material during cycling. Consequently, the solid‐state lithium battery with the composite cathode employing EMG binder and FCG NCM delivered a high discharge capacity of 196.6 mAh g −1 corresponding to an areal capacity of 4.21 mAh cm −2 and showed good capacity retention of 85.1% after 300 cycles at 0.2 C rate and 30 °C.