Atomically distributed asymmetrical five-coordinated Co-N5 moieties on N-rich doped C enabling enhanced redox kinetics for advanced Li-S batteries

摘要

Lithium-sulfur (Li-S) batteries show great promise to serve as high-energy-density energy storage devices. Nevertheless, the practical applications of Li-S batteries are significantly limited by the shuttle effect and sluggish sulfur redox reaction (SROR) kinetics. Herein, an ingenious urea-mediated pyrolysis strategy is for the first time reported to obtain well-defined atomically distributed asymmetrical five-coordinated Co-N-5 moieties anchored on nitrogen-rich (30.0 at%) doped carbon (CoN5 SA/NC) as a highly efficient SROR electrocatalyst. CoN5 SA/NC with a high atomically distributed Co loading (2.12 wt%) effectively catalyzes the liquid-liquid and liquid-solid conversions of lithium polysulfides greatly accelerating the SROR kinetics. When CoN5 SA/NC is served as a coating layer for the separator, the Li-S battery exhibits outstanding capacity properties (1060 mA h g(-1) at 1C and 922 mA h g(-1) at 2C) and superior cycling stability (ultralow decay of 0.033% per cycle at 3C for 1600 cycles). An ultrahigh areal capacity of 7.25 mA h cm(-2) can be acquired for the CoN5 SA/NC based Li-S battery even with a high sulfur loading of 6.5 mg cm(-2). Obviously, the asymmetrical single-atom site engineering strategy demonstrates great potential for practical applications of advanced metal-S batteries.

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