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Optimized Cycle and Safety Performance of Lithium–Metal Batteries with the Sustained‐Release Effect of Nano CaCO3

The capacity attenuation and poor safety caused by lithium dendrite and interface side reactions have hindered the application of lithium–metal batteries (LMBs) for a long time. To solve this problem, some liquid or salt additives have been added to the electrolyte to promote the uniform stripping/plating of lithium, however, the consumption of electrolyte during cycles reduces the concentration of active components, resulting in the gradual failure of additives. Herein, a new solid additive (nano CaCO3) working under the principle of sustained release is proposed: the homo‐dispersed nano CaCO3 particles can continuously absorb the decomposition by‐products generated during the side reaction and release Ca2+, which cannot only inhibit the tip deposition of Li+ through electrostatic shielding effect but also effectively promote the formation of stable F‐rich solid–electrolyte interphase (SEI). As the consequence, a notably optimized electrochemical performance for commercial carbonate electrolyte after adding 3 wt.% nano CaCO3 is observed, and the cycle life of symmetric Li||Li cells is extended from <400 h to over 800 h at 1 mA cm−2. In addition, the modified emulsion‐like electrolyte has lower volatility and its protective effect on the separator is confirmed by ex situ optical observation, reflecting the safety improvement of LMBs.