Enabling High‐Performance NASICON‐Based Solid‐State Lithium Metal Batteries Towards Practical Conditions

Abstract

AbstractSolid‐state lithium metal batteries (SSLMBs) are promising next‐generation high‐energy rechargeable batteries. However, the practical energy densities of the reported SSLMBs have been significantly overstated due to the use of thick solid‐state electrolytes, thick lithium (Li) anodes, and thin cathodes. Here, a high‐performance NASICON‐based SSLMB using a thin (60 µm) Li1.5Al0.5Ge1.5(PO4)3 (LAGP) electrolyte, ultrathin (36 µm) Li metal, and high‐loading (8 mg cm−2) LiFePO4 (LFP) cathode is reported. The thin and dense LAGP electrolyte prepared by hot‐pressing exhibits a high Li ionic conductivity of 1 × 10−3 S cm−1 at 80 °C. The assembled SSLMB can thus deliver an increased areal capacity of ≈1 mAh cm−2 at C/5 with a high capacity retention of ≈96% after 50 cycles under 80 °C. Furthermore, it is revealed by synchrotron X‐ray absorption spectroscopy and in situ high‐energy X‐ray diffraction that the side reactions between LAGP electrolyte and LFP cathode are significantly suppressed, while rational surface protection is required for Ni‐rich layered cathodes. This study provides valuable insights and guidelines for the development of high‐energy SSLMBs towards practical conditions.