Zinc Single-Atom-Regulated Hard Carbons for High-Rate and Low-Temperature Sodium-Ion Batteries

Hard carbons, as one of the most commercializable anode materials for sodium-ion batteries (SIBs), have to deal with the trade-off between the rate capability and specific capacity or initial Columbic efficiency (ICE), and the fast performance decline at low temperature (LT) remains poorly understood. Here, a comprehensive regulation on the interfacial/bulk electrochemistry of hard carbons through atomic Zn doping is reported, which demonstrates a record-high reversible capacity (546 mAh g(-1)), decent ICE (84%), remarkable rate capability (140 mAh g(-1) @ 50 A g(-1)), and excellent LT capacity (443 mAh g(-1) @ -40 degrees C), outperforming the state-of-the-art literature. This work reveals that the Zn doping can generally induce a local electric field to enable fast bulk Na+ transportation, and meanwhile catalyze the decomposition of NaPF6 to form a robust inorganic-rich solid-electrolyte interphase, which elaborates the underlying origin of the boosted electrochemical performance. Importantly, distinguished from room temperature, the intrinsic Na+ migration/desolvation ability of the electrolyte is disclosed to be the crucial rate-determining factors for the SIB performance at LT. This work provides a fundamental understanding on the charge-storage kinetics at varied temperatures.

Automated summary

This study demonstrates a comprehensive regulation on the interfacial/bulk electrochemistry of hard carbons through atomic Zn doping, resulting in record-high reversible capacity, decent initial Columbic efficiency, remarkable rate capability, and excellent low-temperature capacity, outperforming the state-of-the-art literature. It reveals that Zn doping induces a local electric field for fast Na+ transportation and catalyzes the formation of a robust solid-electrolyte interphase, explaining the boosted electrochemical performance.