Mesoporous carbon layer encapsulated SnSe nanosheets via covalent bonds for high-performance sodium ion batteries

Sodium ion batteries (SIBs) have been widely studied because of their low cost, low standard redox potential, and abundant sodium availability. However, the structural rupture during the Na⁺ insertion/extraction processes and the poor conductivity of the anode material limit its cycling stability and rate capability. Herein, SnSe@C was prepared by high-temperature annealing with dopamine hydrochloride as the carbon source, while SnSe was prepared by a protein reduction method. The carbon layer not only works as a protective layer to limit the volume expansion of SnSe and reduce the dissolution of Na₂Se and poly-selenides generated during the discharge process in the electrolyte, but also as a conductive matrix to expedite electron transfer, thereby boosting the cycling stability and rate capability of SnSe@C. Benefiting from the above advantages, SnSe@C exhibits a specific capacity of 211.3 mAh g⁻¹ at 0.1 A g⁻¹ after 110 cycles and outstanging rate capability (210.1 mAh g⁻¹ at 5.0 A g⁻¹ and capacity retention rate of 63.2% from 0.1 to 1.0 A g⁻¹). This study not only proposes an idea for promoting the cycling stability and rate capability of SnSe, but also paves the way for providing anodic materials with a stable structure for SIBs.