Binding Nanosized Cobalt Chalcogenides in B,N-Codoped Graphene for Enhanced Sodium Storage

A general process is developed to prepare binding nanosized cobalt chalcogenides in B,N-codoped graphene (CoSe2/BNG and CoS2/BNG). When used as anodes for sodium-ion batteries, the CoSe2/BNG and CoS2/BNG deliver excellent sodium-storage performance. The CoSe2/BNG displays a reversible capacity of 270 mAh g(-1) after 2000 cycles at a current density of 1 A g(-1). Even at 20 A g(-1), it can still give a capacity of 187 mAh g(-1). Moreover, the CoS2/BNG shows 387 mAh g(-1) at 10 A g(-1), demonstrating its superior high rate performance. The enhanced sodium-storage properties of the CoSe2/BNG and CoS2/BNG nanocomposites may be attributed to the high conductive graphene network, enhanced sodium storage of B,N-codoping in graphene, and the small CoSe2 and CoS2 nanocrystallites that shorten the electronic and ionic diffusion length throughout the electrode.