Interconnected porous carbon with tunable pore size as a model substrate to confine LiFePO4 cathode material for energy storage

• The confinement effect of porous carbon allows controllable nano-sized LiFePO4.
• The interconnected carbon offers fast and continuous electrons transfer path.
• LiFePO4 with smaller size and suitable loading exhibits good rate performance.
• Small nanospheres confined in open-mesopore carbon leads to fast Li-ion diffusion.

LiFePO4/C composites with tunable particle size and loading content have been prepared using the porous carbon with large pore volume and controllable pore size as an interconnected conductive framework and rigid nano-confinement matrix. The large pore volume of carbon provides sufficient space for LiFePO4 hosting and the controllable pore size of carbon restricts the growth of LiFePO4 crystals to further improve the rate performance. When used as the cathode materials for lithium-ion batteries, they exhibit a stable and high reversible capacity of 161 mA h g−1 at 0.1 C, 106 mA h g−1 at 20 C and 50 mA h g−1 at 50 C. The cell retains 94% of its initial capacity at 20 C over 200 cycles with an ultrahigh specific power of 10,446 W kg−1. The high rate performance and good cycle stability can be ascribed to the small nano-sized LiFePO4 confined in the nanopores of the carbon matrix with suitable loading content and good contact between LiFePO4 and the continuous conductive carbon framework, thus allowing fast lithium-ion diffusion and electrons transfer. This structure model may be valid for better understanding the rate performance and might be extended for fabrication of other high power electrode materials.

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