Tuning Crystalline\nPreferred Orientation of SnSe<sub>2</sub> Anode by Co-doping to Enhance\nPseudocapacitive Behaviors\nfor High-Performance Sodium Storage

SnSe<sub>2</sub> has attracted great attention due to\nits unique\n2D-layered structure, which makes it capable of sodium ion storage\nand higher theoretical capacities compared to traditional anode materials\nlike hard carbon for sodium ion batteries (SIBs). However, SnSe<sub>2</sub>-based materials will cause structural damage due to volume\nexpansion during ion storage, leading to poor cycle stability and\nrate capacity. In this work, Co-doped SnSe<sub>2</sub> (Co-SnSe<sub>2</sub>) with preferred crystal orientation was fabricated by a one-step\nsolvothermal method. It has been found that after doping Co, the lower\n(001) crystal plane located at 14.4° replaced the higher (101)\nplane at 30.7° as the dominant crystal plane in Co-SnSe<sub>2</sub>, which significantly promoted ion diffusion and enhanced the pseudocapacitance\nbehavior. Therefore, this Co-SnSe<sub>2</sub> anode achieves a high\ncapacity of 504 mAh g<sup>–1</sup> at 1 A g<sup>–1</sup>, and a high-rate cycle stability, delivering a reversible capacity\nof 302 mAh g<sup>–1</sup> at 5 A g<sup>–1</sup> after\n1800 cycles with a retained capacity rate of 94%. Moreover, the Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>||Co-SnSe<sub>2</sub> full cell exhibits a stable cycle performance of over 300 cycles\nat 1 A g<sup>–1</sup>, demonstrating great promise for practical\napplications. This work provides an effective reference for the exploration\nof high-performance sodium storage anode materials.