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Cobalt phosphides are potential catalysts to assist the conversion of lithium polysulfides (LiPSs) in lithium-sulfur (Li-S) batteries. However, existing synthesis methods have difficulty precisely tuning their band valences, which is crucial to balancing intermediate products' adsorption and conversion abilities in Li-S batteries. Moreover, studies on the relationship between their band structures and electrochemical performance are limited. Herein, we report cobalt phosphides (Co x P) with a heterogeneous interface of CoP/Co 2 P embedded in hollow carbon nanofibers (denoted as Co x P@HCNF) via a one-step sequential phosphorization and carbonization strategy, which is applied as an effective interlayer for Li-S batteries. The Co band valence in Co x P was adjusted to regulate the d-p band gap. Theoretical calculations predict that Co x P with a narrowed d-p band center can optimize the electron transfer kinetics and the adsorption affinity with LiPSs. Li-S full cells with a Co x P@HCNF interlayer demonstrated a high specific capacity of 1265 mA h g −1 at 0.2C and excellent cycle stability of 788 mA h g −1 over 400 cycles at 2.0C. A cell with a lean electrolyte (6.0 μL mg −1 ) and a high sulfur loading (6.2 mg cm −2 ) delivered a high areal capacity of 4.5 mA h cm −2 at 0.5C. This study demonstrates that bimetallic coupling-induced electronic-state modulation effectively balances the chemical adsorption and catalytic capability for developing high-performance Li-S batteries.
Lv et al. (Fri,) studied this question.