Tuning Crystalline Preferred Orientation of SnSe₂ Anode by Co-doping to Enhance Pseudocapacitive Behaviors for High-Performance Sodium Storage

SnSe₂ has attracted great attention due to its unique 2D-layered structure, which makes it capable of sodium ion storage and higher theoretical capacities compared to traditional anode materials like hard carbon for sodium ion batteries (SIBs). However, SnSe₂-based materials will cause structural damage due to volume expansion during ion storage, leading to poor cycle stability and rate capacity. In this work, Co-doped SnSe₂ (Co-SnSe₂) with preferred crystal orientation was fabricated by a one-step solvothermal method. It has been found that after doping Co, the lower (001) crystal plane located at 14.4° replaced the higher (101) plane at 30.7° as the dominant crystal plane in Co-SnSe₂, which significantly promoted ion diffusion and enhanced the pseudocapacitance behavior. Therefore, this Co-SnSe₂ anode achieves a high capacity of 504 mAh g^-1 at 1 A g^-1, and a high-rate cycle stability, delivering a reversible capacity of 302 mAh g^-1 at 5 A g^-1 after 1800 cycles with a retained capacity rate of 94%. Moreover, the Na₃V₂(PO₄)₃||Co-SnSe₂ full cell exhibits a stable cycle performance of over 300 cycles at 1 A g^-1, demonstrating great promise for practical applications. This work provides an effective reference for the exploration of high-performance sodium storage anode materials.