Hierarchical Encapsulation and Rich sp² N Assist Sb₂Se₃-Based Conversion-Alloying Anode for Long-Life Sodium- and Potassium-Ion Storage

Sodium- and potassium-ion batteries have exhibited great application potential in grid-scale energy storage due to the abundant natural resources of Na and K. Conversion-alloying anodes with high theoretical capacity and low-operating voltage are ideal option for SIBs and PIBs but suffer the tremendous volume variations. Herein, a hierarchically structural design and sp² N-doping assist a conversion-alloying material, Sb₂Se₃, to achieve superior life span more than 1000 cycles. It is confirmed that the Sb₂Se₃ evolves into nano grains that absorb on the sp² N sites and in situ form chemical bonding of C-N-Sb after initial discharge. Simulation results indicate that sp² N has more robust interaction with Sb and stronger adsorption capacities to Na⁺ and K⁺ than that of sp³ N, which contributes to the durable cycling ability and high electrochemical activity, respectively. The ex situ transmission electron microscopy and X-ray photoelectron spectroscopy results suggest that the Sb₂Se₃ electrode experiences conversion-alloying dual mechanisms based on 12-electron transfer per formula unit.