Bridging Covalently Functionalized Black Phosphorus on Graphene for High-Performance Sodium-Ion Battery

Black phosphorus (BP) has recently aroused researchers' great interest as promising anode material for sodium-ion battery (SIB), owing to its high theoretical capacity (2596 mAh g^-1) and good electric conductivity (about 300 S m^-1). However, the large volume variation during electrochemical cycling makes it difficult to use for practical applications. Herein, the reversible performance of BP in SIB is significantly enhanced by bridging covalently functionalized BP on graphene. The enhanced interaction between the chemical functionalized BP and graphene improves the stability of BP during long-cycle running of SIB. The bridging reduces the surface energy and increases thickness of BP available for enlarging the channel between BP nanosheet and graphene. The enlarged channel stores more sodium ions for improving cycle performance. Significantly, two types of phosphorus-carbon bond are first detected during experimental analysis. Benefiting from the strategy, the BP-based SIB anode exhibits 1472 mAh g^-1 specific capacity at 0.1 A g^-1 in the 50th cycle and 650 mAh g^-1 at 1 A g^-1 after 200 cycles.