Ultrathin Layered SnSe Nanoplates for Low Voltage,High‐Rate,and Long‐Life Alkali–Ion Batteries

2D electrode materials with layered structures have shown huge potential in the fields of lithium‐ and sodium‐ion batteries. However, their poor conductivity limits the rate performance and cycle stability of batteries. Herein a new colloid chemistry strategy is reported for making 2D ultrathin layered SnSe nanoplates (SnSe NPs) for achieving more efficient alkali‐ion batteries. Due to the effect of weak Van der Waals forces, each semiconductive SnSe nanoplate stacks on top of each other, which can facilitate the ion transfer and accommodate volume expansion during the charge and discharge process. This unique structure as well as the narrow‐bandgap semiconductor property of SnSe simultaneously meets the requirements of achieving fast ionic and electronic conductivities for alkali‐ion batteries. They exhibit high capacity of 463.6 mAh g⁻¹ at 0.05 A g⁻¹ for Na‐ion batteries and 787.9 mAh g⁻¹ at 0.2 A g⁻¹ for Li‐ion batteries over 300 cycles, and also high stability for alkali‐ion batteries.