CoS2/S-Doped C with In Situ Constructing Heterojunction Structure for Boosted K-Ion Diffusion and Highly Efficient Storage

Exploring the desired anode materials to address the issues of poor structural stability tardy redox kinetics caused by large potassium ionic radius are fatal for the realization of large-scale applications of potassium-ion batteries. In this work, the feasibility to achieve promoted K+ storage by constructing the model of CoS2 enfolded in carbon was verified by the density functional theory calculations. And the results predicted a faster electron/potassium ion transport kinetics than bare CoS2 by increasing electron carrier density and narrowing diffusion barrier. Therefore, an interfacial engineering strategy was applied and implemented to synthesize the CoS2 nanoparticles enveloped in the S-doped carbon (CoS2/SC) under this inspiration. The as-prepared CoS2/SC composite exhibited a prominent rate capability and long cycling lifespan, delivering the high capacity of 375 mA h g(-1) at 0.2 A g(-1) at the 100th cycle and 273 mA h g(-1) at 2 A g(-1) over 300 cycles. The in/ex situ characterizations unraveled the converse mechanism of CoS2/SC in K+ storage, showing an eventually reversible phase transformation of KxCoS2 <-> Co$$ {\mathrm{K}}_{\mathrm{x}}\mathrm{Co}{\mathrm{S}}_2\leftrightarrow \mathrm{Co} $$ within the electrochemical reactions.

Automated summary

The feasibility of using CoS2 enfolded in carbon to achieve enhanced K+ storage was verified by density functional theory calculations. An interfacial engineering strategy was used to synthesize CoS2 nanoparticles enveloped in S-doped carbon. The resulting CoS2/SC composite exhibited excellent rate capability and long cycling lifespan.