Self-assembly by electrostatic attraction to encapsulate Si in N-rich graphene for high performance lithium-ion batteries

Abstract

In order to improve the electrochemical performance of Si-based anodes, a nitrogen-rich Si/graphene composite anode (NR/Si/G) was synthesized by self-assembly of electrostatic attraction between amino and carboxyl groups. Due to the electrostatic attraction of the amino and carboxyl groups, Si particles were well encapsulated in graphene. Two-dimensional graphene with good flexibility and mechanical strength buffered the volume expansion of Si, protected the electrode from collapsing and flaking and prevented Si from being directly exposed to the electrolyte during cycles. It was also beneficial to form a stable SEI during charge and discharge. In addition, the three-dimensional conductive network composed of N-rich and graphene improved the conductivity of the Si-based anode and promoted the conduction of electrons. The initial coulombic efficiency of the NR/Si/G electrode reached 75.2%. The electrode still maintained a specific discharge capacity of 937 mAh/g at a current density of 1 A/g with a capacity retention ratio of 62.8% after 500 cycles, showing an excellent rate performance.