Significantly\nImproved Sodium-Ion Storage Performance of CuS Nanosheets Anchored\ninto Reduced Graphene Oxide with Ether-Based Electrolyte

Abstract

Currently\nsodium-ion batteries (SIBs) as energy storage technology have attracted\nlots of interest due to their safe, cost-effective, and nonpoisonous\nadvantages. However, many challenges remain for development of SIBs\nwith high specific capacity, high rate capability, and long cycle\nlife. Therefore, CuS as an important earth-abundant, low-cost semiconductor\nwas applied as anode of SIBs with ether-based electrolyte instead\nof conventional ester-based electrolyte. By incorporating reduced\ngraphene oxide (RGO) into CuS nanosheets and optimizing the cutoff\nvoltage, it is found that the sodium-ion storage performance can be\ngreatly enhanced using ether-based electrolyte. The CuS-RGO composites\ndeliver an initial Coulombic efficiency of 94% and a maximum specific\ncapacity of 392.9 mAh g^–1 after 50 cycles at a current\ndensity of 100 mA g^–1. And a specific capacity of\n345 mAh g^–1 is kept after 450 cycles at a current\ndensity of 1 A g^–1. Such an excellent electrochemical\nperformance is ascribed to the conductive network construction of\nCuS-RGO composites, the suppression of dissolved polysulfide intermediates\nby using ether-based electrolyte, and the avoidance of conversion-type\nreaction by optimizing the cutoff voltage.