High-Areal-Capacity All-Solid-State Lithium Batteries Enabled by Electronically Conductive Li-Deficient LiNiO₂ Cathode

All-solid-state lithium batteries (ASSLBs) with Ni-rich cathodes are promising candidates for achieving high energy and improved safety. However, their electrochemical performance is limited by cathode loading, especially in the absence of conductive agents. Herein, we utilize electronically conductive Li-deficient LiNiO₂ (LD-LNO) to construct high-areal-capacity ASSLBs under high cathode loading. This LD-LNO shows an inherent enhanced electronic conductivity and minimal surface impurities. Electrochemical analysis combined with solid-state nuclear magnetic resonance spectroscopy demonstrates the mitigation of the detrimental H3 phase transition and the side reactions at the LD-LNO/Li₆PS₅Cl interface. As a result, LD-LNO-based ASSLBs achieve competitive cyclability and rate capability without the need for cathode modifications. A high reversible areal capacity of 15.2 mAh cm^-2 is attained at 35 °C under a 133.8 mg cm^-2 LD-LNO mass loading. This work sheds light on electronically conductive cathodes, providing a perspective for addressing the high cathode loading issue in ASSLBs.