Revealing the evolution of doping anions and their impact on K-Ion storage: A case study of Se-doped In2S3

Anion doping has been proven to be an effective way to enhance the rate capability and cyclability of conversion-type anode materials for lithium-ion/sodium-ion batteries. However, it is still a burgeoning methodology in potassium-ion batteries. In addition, the evolution of doping anions and their impact on the K+ storage during the conversion reaction are indeterminate. Herein, Se anions are purposefully doped into a model conversion-type In2S3@C anode material, which is labeled as In2S3–xSex@C. Elaborate analytical techniques and theoretical simulations reveal that Se doping regulates the electronic structure and weakens the bonding strength of In2S3–xSex, resulting in fast K+ intercalation and high conversion reactivity. The advantages of Se doping can be maintained upon the whole cycling because Se exists in the form of doping after potassiation (doped into K2S: K2S1–x/3Sex/3) and depotassiation (re-doped into In2S3: In2S3–xSex), which is proved by various electrochemical analyses and ex-situ observations. Therefore, In2S3–xSex@C exhibits a high reversible capacity (709 mA h g–1 at 0.1 A g–1) and excellent cyclability (118 mA h g–1 at 10.0 A g–1 after 1000 cycles). Moreover, full cells with the In2S3–xSex@C anode achieve a satisfying energy density of 146 Wh kg–1. This work provides a new guideline for designing advanced anion-doping conversion-type anode materials of potassium-ion batteries.