Long-cycling lithium polymer battery enabled by interface integration between cathode and solid electrolyte

To minimize the interfacial resistance between the solid-state electrolyte (SSE) and electrode, we proposed an interface integrated cathode/SSE (ICSE) process for the fabrication of high-performance lithium polymer metal battery (LPMB) by directly casting an ultrathin robust semi-interpenetrating network (semi-IPN) SSE on the cathode layer prepared by ion conductive binder. This integrated interfacial structure builds a continuous ion transport pathway at both cathode layer and SSE/cathode interface. Moreover, it significantly enhances the interfacial contact between the cathode and SSE layers for better adhesion. Meanwhile, the robust semi-IPN structure endows the SSEs with thin thickness with excellent mechanical strength and ion conductivity. The SSE displayed a wide electrochemical window of 5.24 V vs. Li/Li⁺, a high tensile strength beyond 15.4 MPa, and stable thermal stability over 260 °C. As a result, the integrated LiFePO₄ LPMB exhibited a high capacity of 157 mAh g⁻¹ with discharge capacity retention of 98.7% after 500 cycles at 0.1 C and room temperature (RT). Even applying high voltage LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) with high loading mass of 5 mg cm⁻², the ICSE-NCM battery could still illustrate a decent capacity of 149 mAh g⁻¹ at 0.5 C and RT. The proposed ICSE design represents a promising strategy for the practical application of high-performance LPMB.