Hierarchical C-P(=O)(-O-)n (n≤2)-linked nano-Si/N-doped C/ graphene porous foam as anodes for high-performance lithium ion batteries

Cooperative supermolecular self-assembly technique is introduced to synthesize a novel C-P(=O)(-O-)(n) (n <= 2)-linked nano-Si/N-doped C/graphene anode composite for lithium ion batteries. This composite shows three-dimensional (3D) foam structure, which integrates porous structure, hierarchical property, excellent conductivity and high flexibility. The presence of C-P(=O)(-O-)(n) (n <= 2) groups strengthens the linkage between Si nanoparticles, N-doped C and graphene. As an anode for lithium ion batteries, it delivers a stable discharge capacity of about 1130 mAh g(-1) at 200 mA g(-1). At 400 mA g(-1), a discharge capacity of about 812 mAh g(-1) is kept after 400 cycles with capacity retention of 83.5%, versus the second discharge capacity. At 3200 mA g(-1), the composite exhibits a stable discharge capacity of about 480 mAh g(-1) after 550 cycles. The excellent cycling performance and rate capability are ascribed to the improvement of conductivity, the enhancement of structural stability and the shortening of ion and electron diffusion pathways. As the coating layer of Si particles, the C-P(=O)(-O-)(n) (n <= 2)-linked N-doped C exhibits obvious advantage over the C without C-P(=O)(-O-)(n) groups in improving the cycling performance. (C) 2018 Elsevier Ltd. All rights reserved.