Self-Supporting Electrode Composed of SnSe Nanosheets, Thermally Treated Protein, and Reduced Graphene Oxide with Enhanced Pseudocapacitance for Advanced Sodium-Ion Batteries

A self-supporting electrode composed of carbon-coated tin selenide nanosheets, thermally treated protein, and reduced graphene oxide was prepared for sodium-ion batteries via a protein-assisted self-assembly, cost-efficient vacuum filtration, and subsequent low-temperature annealing. During this process, the hierarchical three-dimensional framework has been achieved, in which tin selenide nanosheets consisted of nanocrystals with diameter of about 5 nm, and confined in a highly conductive interconnected reduced graphene oxide network by thermally treated bovine serum albumin. The unique structure not only promises structural stability and the reaction kinetics of the electrode during charge-discharge process, but also possesses substantial interfacial sites for Na+ redox reaction giving rise to additional pseudocapacitance. Therefore, the self-supporting composite as anode exhibits an outstanding capacity of 617.5 mA h g(-1) at 0.1 A g(-1), high rate capability of 213.8 mA h g(-1) at 5 A g(-1), and superior cyclic performance of 503.9 mA h g(-1) at 0.1 A g(-1) after 100 cycles. Therefore, the electrode materials have large potential in advanced sodium-ion batteries in portable, flexible, and wearable electronics.