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 (CoSe 2 /BNG and CoS 2 /BNG). When used as anodes for sodium‐ion batteries, the CoSe 2 /BNG and CoS 2 /BNG deliver excellent sodium‐storage performance. The CoSe 2 /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 CoS 2 /BNG shows 387 mAh g −1 at 10 A g −1 , demonstrating its superior high rate performance. The enhanced sodium‐storage properties of the CoSe 2 /BNG and CoS 2 /BNG nanocomposites may be attributed to the high conductive graphene network, enhanced sodium storage of B,N‐codoping in graphene, and the small CoSe 2 and CoS 2 nanocrystallites that shorten the electronic and ionic diffusion length throughout the electrode.