A Salt-in-Metal Anode: Stabilizing the Solid Electrolyte Interphase to Enable Prolonged Battery Cycling

Metallic lithium (Li) is the ultimate anode candidate for high-energy-density rechargeable batteries. However, its practical application is hindered by serious problems, including uncontrolled dendritic Li growth and undesired side reactions. In this study a concept of "salt-in-metal" is proposed, and a Li/LiNO3 composite foil is constructed such that a classic electrolyte additive, LiNO3, is embedded successfully into the bulk structure of metallic Li by a facile mechanical kneading approach. The LiNO3 reacts with metallic Li to generate Li+ conductive species (e.g., Li3N and LiNxOy) over the entire electrode. These derivatives afford a stable solid electrolyte interphase (SEI) and effectively regulate the uniformity of the nucleation/growth of Li on initial plating, featuring a low nucleation energy barrier and large crystalline size without mossy morphology. Importantly, these derivatives combined with LiNO3 can in-situ repair the damaged SEI from the large volume change during Li plating/stripping, enabling a stable electrode-electrolyte interface and suppressing side reactions between metallic Li and electrolyte. Stable cycling with a high capacity retention of 93.1% after 100 cycles is obtained for full cells consisting of high-loading LiCoO2 cathode (approximate to 20 mg cm(-2)) and composite metallic Li anode with 25 wt% LiNO3 under a lean electrolyte condition (approximate to 12 mu L) at 0.5 C.