Fast and Durable Potassium Storage Enabled by Constructing Stress-Dispersed Co₃Se₄ Nanocrystallites Anchored on Graphene Sheets.

Abstract

Transition metal dichalcogenides are regarded as promising anode materials for potassium-ion batteries (PIBs) because of their high theoretical capacities. However, due to the large atomic radius of K⁺, the structural damage caused by the huge volume expansion upon potassiation is much more severe than that of their lithium counterparts. In this research, a stress-dispersed structure with Co₃Se₄ nanocrystallites orderly anchored on graphene sheets is achieved through a two-step hydrothermal treatment to alleviate the structural deterioration. The ability to reduce the contact stress by the well-dispersed Co₃Se₄ nanocrystallites during K⁺ intercalation, together with the highly conductive graphene matrix, provides a more reliable and efficient anode architecture than its two agminated counterparts. Given these advantages, the optimized electrode delivers excellent cycling stability (301.8 mA h g^-1 after 500 cycles at 1 A g^-1), as well as an outstanding rate capacity (203.8 mA h g^-1 at 5 A g^-1). Further <i>in situ</i> and <i>ex situ</i> characterizations and density functional theory calculations elucidate the potassium storage mechanism of Co₃Se₄ during the conversion reaction and reveal the fast electrochemical kinetics of the rationally designed electrode. This work provides a practical approach for constructing stable metal-selenide anodes with long cycle life and high-rate performance for PIBs.