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Over‐Potential Tailored Thin and Dense Lithium Carbonate Growth in Solid Electrolyte Interphase for Advanced Lithium Ion Batteries

A stable solid electrolyte interphase (SEI) is highly desired to prevent parasitic reactions during normal operation of lithium‐ion batteries (LIBs). Lithium carbonate (Li2CO3) is one of the most significant components for smooth SEI passivation layers; while the formation mechanism and special distribution of the Li2CO3 layer has not yet been illustrated. Here, an over‐potential tailored Li2CO3 growth mechanism based on the typical hard carbon anode is demonstrated. With an increase in the over‐potential, the size of Li2CO3 decreases gradually as the amount increases. When the over‐potential is large (potential at 0.01 V), a Li2CO3‐rich thin and dense inorganic layer with the average thickness of 4.4 nm in the SEI is constructed. The special SEI the completely wraps the boundaries of the anode enables a larger Li‐ion de‐solvation energy barrier and a lower Li‐ion diffusion energy barrier, which supports low self‐discharge behavior and a fast kinetic rate at the anode. More generally, this Li2CO3 growth mechanism is also applicable to commercialized graphite anodes and similar results are also obtained. Therefore, this work provides a new insight into the Li2CO3 growth mechanism in SEIs, as well as a guideline for the design of stable artificial SEIs.