N-doped 3D carbon encapsulating nickel selenide nanoarchitecture with cation defect engineering: An ultrafast and long-life anode for sodium-ion batteries

Transition metal chalcogenides (TMCs) hold great potential for sodium-ion batteries (SIBs) owing to their multielectron conversion reactions, yet face challenges of poor intrinsic conductivity, sluggish diffusion kinetics, severe phase transitions, and structural collapse during cycling. Herein, a self-templating strategy is proposed for the synthesis of a class of metal cobalt-doped NiSe nanoparticles confined within three-dimensional (3D) N -doped macroporous carbon matrix nanohybrids (Co-NiSe/NMC). The cation defect engineering within the developed Co-NiSe and 3D N -doped carbon plays a crucial role in enhancing intrinsic conductivity, reinforcing structural stability , and reducing the barrier to sodium ion diffusion, which are verified by a series of electrochemical kinetic analyses and density functional theory calculations. Significantly, such cation defect engineering not only reduces overpotential but also accelerates conversion reaction kinetics, ensuring both exceptional high-rate capability and extended durability. Consequently, the optimally engineered Co-NiSe/NMC demonstrates a remarkable rate performance, delivering 390 mAh g −1 at 10 A g −1 . Moreover, it exhibits an unprecedented lifespan, maintaining a remarkable capacity of 403 mAh g −1 after 1400 cycles and 318 mAh g −1 after 4000 cycles, even at high rates of 1.0 and 2.0 A g −1 , respectively. This work marks a substantial advancement in achieving both high performance and prolonged cycle life in sodium-ion batteries.