Exploration of fast ion diffusion kinetics in graphene nanoscrolls encapsulated CoSe2 as advanced anode for high-rate sodium-ion batteries

Abstract

Sodium-ion batteries (SIBs) have drawn much attention due to the abundance and low cost of sodium. However, electrode materials of SIBs displayed sluggish Na+ diffusivity and fatal volume expansion, owing to the larger ionic radius of Na+ ions than Li+ ions. In this work, we built the CoSe2 nanoparticles embedded in graphene nanoscrolls (GNS) as advanced anodes for high-rate SIBs. The CoSe2/C@GNS anodes exhibited a high reversible capacity of 545 mA h g−1 at 0.2 A g−1. Moreover, they showed an outstanding cycling stability of 455 mA h g−1 after 5000 cycles at 1 A g−1, with a capacity retention of 92% calculated from 10th cycle. The CoSe2/C@GNS anode also demonstrate ultrahigh rate capabilities (212.5 mAh g−1 at 50 A g−1). In addition, with a high mass loading (6 mg cm−2), the electrode still displayed a stable capacity (412 mA h g−1 1 A g−1). The fast electron transfer and Na+ ion diffusion kinetics creates the excellent electrochemical properties, on account of the uniform arrangement of nanoparticles and unique reticular crosslinking structure of CoSe2/C@GNS. This strategy could also be constructed other electrode materials, which provides more probabilities for the development of SIBs.