Internal interface engineering of yolk-shell structure toward fast and robust potassium storage

Advanced anode materials with stable and fast K-ion storage behavior are of great significance for potassium-ion batteries (PIBs) toward large-scale applications, while it still remains a big challenging due to their intrinsic poor conductivity and large volume variation during cycles. Herein, we develop an internal interfacial engineering by encapsulating core-shell NiS2@C nanoparticles within MOF-derived hollow carbon shell for superior PIB anodes. As-prepared yolk-shell NiS2@C@C composite integrates the structure superiority of abundant interior void space, outer protective carbon shell and internal conductive carbon layer. Comprehensive experimental and theoretical methods illuminate that internal NiS2/C interface is conductive to boost charge transport kinetics, enhance pseudocapacitive behavior, and mitigate mechanical stress in outer carbon shell. As a result, it manifests an ultrahigh capacity of 481 mA h g(-1) at 0.2 A g-1, and guarantees the rate capability of 306 mA h g(-1) at 20 A g-1. Moreover, it presents excellent cycle stability (358 mA h g(-1) after 1600 cycles at 1 A g(-1)), which is extremely competitive among the best reported conversion anodes for PIBs.

Automated summary

Advanced anode materials with stable and fast K-ion storage behavior are developed by encapsulating core-shell NiS2@C nanoparticles within MOF-derived hollow carbon shell. The internal interfacial engineering enhances the charge transport kinetics, pseudocapacitive behavior, and mitigates mechanical stress in the outer carbon shell. The yolk-shell NiS2@C@C composite exhibits ultrahigh capacity and excellent cycle stability, making it highly competitive for potassium-ion batteries.