Insights into the Potassium Ion Storage Behavior and Phase Evolution of a Tailored Yolk-Shell SnSe@C Anode

Tin chalcogenides are regarded as promising anode materials for potassium ion batteries (PIBs) due to their considerable specific capacity. However, the severe volume effect, limited electronic conductivity, and the shuttle effect of the potassiation product restrict the application prospect. Herein, based on the metal evaporation reaction, a facile structural engineering strategy for yolk-shell SnSe encapsulated in carbon shell (SnSe@C) is proposed. The internal void can accommodate the volume change of the SnSe core and the carbon shell can enhance the electronic conductivity. Combining qualitative and quantitative electrochemical analyses, the distinguished electrochemical performance of SnSe@C anode is attributed to the contribution of enhanced capacitive behavior. Additionally, first-principles calculations elucidate that the heteroatomic doped carbon exhibits a preferable affinity toward potassium ions and the potassiation product K2Se, boosting the rate performance and capacity retention consequently. Furthermore, the phase evolution of SnSe@C electrode during the potassiation/depotassiation process is clarified by in situ X-ray diffraction characterization, and the crystal transition from the SnSe Pnma(62) to Cmcm(63) point group is discovered unpredictably. This work demonstrates a pragmatic avenue to tailor the SnSe@C anode via a facile structural engineering strategy and chemical regulation, providing substantial clarification for the phase evolution mechanism of SnSe-based anode for PIBs.

Automated summary

This study proposes a facile structural engineering strategy for encapsulating SnSe in a carbon shell, which improves the electrochemical performance of potassium-ion battery anode materials. The heteroatomic doped carbon shows a favorable affinity towards potassium ions and potassiation products, enhancing the rate performance and capacity retention. The in situ X-ray diffraction characterization reveals the phase evolution of the SnSe@C electrode during the potassiation/depotassiation process.