Abstract:

As typical conversion reaction-type anode materials for sodium-ion batteries (SIBs), iron-base sulfides possess high theoretical capacity, nontoxicity, and nature abundance, making them one of the potential anode materials that can be used in SIBs. However, iron-base sulfides with poor electron/ionic conductivity present a sluggish sodium storage kinetics, which restricts their practical applications. This study utilized iron disulfide (FeS₂) as an example and applies the ion doping strategy to modify the crystal structure and investigate the sample's sodium storage performance. Co²⁺-doped FeS₂ is specifically prepared through a feasible and controllable hydrothermal method. The characterization results reveal that the Co²⁺ amount in the precursor solution plays a key role in regulating the sample's microstructure. Moreover, an enlarged interplanar spacing of (200) is observed in FeS₂. The electrochemical test reveals that the doped materials obtain enhanced rate capabilities and cyclic stability. The optimized sample has revisable specific capacities of 264.3, 224.9, and 193.4 mAh/g at current densities of 1, 2, and 4 A/g, respectively. A 229.8 mAh/g reversible discharge capacity is maintained at 1 A/g current density after 400 cycles, corresponding to 74.6% capacity retention. The kinetics analysis illustrates that the doped FeS₂ presents an improved Na⁺ diffusion coefficient and a capacitive dominated sodium storage mechanism. This study provides theoretical reference for the fabrication of high-performance anode materials for SIBs.

Key words: sodium-ion batteries, heteroatom doping, anode materials, FeS₂, reaction mechanism