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Developing high‐capacity electrodes requires the evaluation of electrochemical behaviors with an increasing current density. Currently, the current density for evaluation of high‐capacity electrodes has reached a new stage where the polarization at the lithium counter electrode has become a technical barrier for the accurate evaluation of battery electrodes, resulting in severe performance and mechanism mischaracterizations. Here, the accurate electrochemical behavior for high‐capacity electrodes via a single‐channel three‐electrode vehicle is decoupled, by which the impact of lithium counter electrode is minimized. The testing high‐capacity graphite electrode is capable of delivering an excellent rate capability with 81.7% capacity retention at 0.3 C, as well as stable cycling performance retaining 97.5% practical reversible capacity after 225 cycles, much higher than the graphite electrode tested with traditional half‐cell testing vehicle but in close agreement with the results obtained from a well‐matched full cell, reflecting accurate electrochemical performance evaluations of high‐capacity electrodes. Moreover, detailed electrochemical mechanisms of impedance and diffusion properties for working electrodes are also successfully decoupled individually. This work uncovers the mismatch between traditional evaluation configuration and increasing testing current density and provides a guideline for accurate electrochemical evaluation for ever‐increasing high‐capacity electrodes, which is of great significance for high‐energy lithium or other alkali‐metal ion batteries. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]