Synchronous Hetero-Interface and Vacancy Engineering for Construction of Pitaya-Like CoSe1-x/C@NC@ZnSe Nanosphere Toward Ultrastable Sodium-Ion Half/Full Batteries

Abstract

Transition metal selenides have attracted extensive attention as promising anode materials for sodium-ion batteries (SIBs) due to their fascinating physical chemistry characteristics. However, its cycling performance especially at high currents, is still unsatisfactory owing to the intrinsic limited conductivity. Herein, N-doped carbon shell coated and ZnSe bonded Se-vacancy enriched CoSe_1-x (CoSe_1-x/C@NC@ZnSe, CZSCV) nanospheres with abundant hetero-interfaces are designed through an in situ Se transfer strategy. Owing to the ingenious structure, as an anode material in SIBs, CZSCV demonstrates superior cycling stability (363.5 mAh g⁻¹ at 10 A g⁻¹ after 1000 cycles) and high-rate sodium storage capability (193.9 mAh g⁻¹ at 20 A g⁻¹ after 5000 cycles). Meanwhile, in the CZSCV//Na₃V₂(PO₄)₃@C full cell, it also delivers a stable capacity of 201.4 mAh g⁻¹ at 1.0 A g⁻¹ and provides a high energy density of 397.4 Wh kg⁻¹ with a power density of 231.6 W kg⁻¹. Based on the kinetics analysis and the density functional theory calculation, the hetero-interfaces and enriched Se-vacancies can synergistically accelerate the Na⁺/electron transfer, owing to the charge redistribution, the decreased diffusion barrier of Na⁺ and increased pseudo-capacitive capacity contribution. As a result, excellent high-rate anode material can be achieved for the SIBs.