Desulfurization‐Induced Formation of Amorphized Substoichiometric Tin Sulfide for Super High‐Rate Capacity and Degradation‐Free Cycling of Na Ion Storage

Abstract This work reports an amorphization and partial desulfurization method to improve the performance of sulfide‐based materials for Na⁺ storage. Specifically, the polypyrrole derived carbon coated amorphous substoichiometric tin sulfide supported on aminated carbon nanotubes (PPY‐C@SnS_x/ACNTs) with amorphized and substoichiometric tin sulfide (SnS_x) is synthesized by simply thermal annealing the PPY‐C@SnS₂/ACNTs. The PPY‐C@SnS_x/ACNTs shows stable reversible capacities of 410.2 mAh g⁻¹ for Na⁺ storage at 0.1 A g⁻¹ and excellent rate capacities of 270.2, 235.5, 217.4, and 210.0 mAh g⁻¹ at 5.0, 10.0, 20.0, and 30.0 A g⁻¹, respectively. Nearly zero drops on the reversible capacities can be observed when it is sodiated/desodiated at 2.0, 5.0, and 10.0 A g⁻¹ for up to 1000, 6500, 8000 cycles, respectively. Its outstanding rate capacities and degradation‐free cycling stabilities mainly arise from the amorphized and substoichiometric structure of SnS_x, which improve the reversible capacities and Na⁺ diffusivities of the PPY‐C@SnS_x/ACNTs. The density functional theory (DFT) calculations indicate that the partial desulfurization can improve the electric conductivity and promote the sodiation/desodiation of SnS_x. It explains why the PPY‐C@SnS_x/ACNTs can exhibit high performance for Na⁺ storage well.