Phase-regulated sodium-storage properties in CuSe and Cu2Se nanoplate anodes

Copper selenides are promising anode materials for sodium-ion batteries (SIBs), owing to high electronic conductivity, rich phase diversity, and large theoretical capacity. However, their phase-dependent sodium-storage performances remain insufficiently defined. Herein, we report a phase-controlled synthesis of CuSe and Cu 2 Se nanoplates (NPLs) to directly compare their phase-dependent electrochemical behavior. When evaluated as SIB anodes, CuSe NPLs demonstrate superior rate capability and cycling stability relative to Cu 2 Se NPLs, delivering a specific capacity of 368.8 mAh g −1 at 20 A g −1 and maintaining 337.4 mAh g −1 at 10 A g −1 after 1,000 cycles with a capacity decay of only 0.012% per cycle. Operando X-ray diffraction and electrochemical kinetic analyses reveal that sodium storage in CuSe is mediated by coupled diffusion-controlled and pseudocapacitive processes. Collectively, these findings confirm that crystal phase decisively governs sodium-storage chemistry and kinetics in copper selenides and offer guidance for high-performance conversion-type anodes for next-generation SIBs.