Dual Layer Coating Strategy Utilizing N-doped Carbon and Reduced Graphene Oxide for High-Performance LiFePO4 Cathode Material

Abstract

Lithium iron phosphate (LiFePO4, LFP) has two major drawbacks such as low lithium ion diffusivity and poor electric conductivity, which limit the wider application as a cathode material for lithium ion batteries. In this work, we report a dual carbon layer coating strategy for LFP, which uses polydopamine-derived nitrogen-doped carbon (N-doped carbon) and reduced graphene oxide (RGO). These dual carbon layers are prepared by a one-pot polymerization process and thermal treatment. The dual carbon coated LFP has a rate capability with a discharge capacity of 98mAh/g at 30C, cycling performance with a discharge capacity of 115mAh/g at 10C, and 96.18% capacity retention after 700 cycles. The high rate performance and the excellent long-term cycling stability can be attributed to the enhanced electric conductivity with N-doped carbon coating, the well-connected electron pathway, and the fast Li+ ion diffusion induced by the small size of the particles. Consequently, coating of LFP with polydopamine derived N-doped carbon and RGO produces a material suitable for high-performance lithium-ion batteries.