Improved Performance of Solid-State Lithium–Metal Batteries by Integrating NCM622 Cathodes with LAGP Electrolytes

Thin electrolytes paired with thick cathodes are expected to deliver a higher energy density and improved areal capacity. However, high tortuosity and low ionic conductivity within thick cathodes limit the rate performance. This work proposes a dual strategy of “3D ion-transporting framework and integrated electrolyte-cathode” to simultaneously address the challenges of poor interface contact and impeded ion transport in thick cathodes. 85% Li1.5Al0.5Ge1.5(PO4)3 (LAGP) and 15% PVDF are used to prepare polymer-in-ceramic composite electrolytes (PIC-85%LAGP) with ∼30 μm thickness and ionic conductivity of 3.46 × 10–4 S cm–1 at 30 °C. By introducing 15% LAGP electrolytes into LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes, a continuous 3D ionic transport network is constructed in the thick NCM-L15 composite cathodes (80 μm thickness, 14∼16 mg cm–2 NCM622 loading), thereby enhancing the utilization efficiency of the cathode-active materials (CAMs). The integrated NCM-L15|PIC-85%LAGP|Li battery delivers an area-specific capacity of 2.28 mAh cm–2 (corresponding to 163.14 mAh g–1) at 0.2C, retains 86.35% capacity after 200 cycles, and exhibits a discharge capacity of 83.56 mAh g–1 at 1C and 30 °C. This work provides valuable strategies for achieving solid-state lithium–metal batteries with thin electrolytes and thick cathodes.