Engineering 3D bicontinuous hierarchically macro-mesoporous LiFePO₄/C nanocomposite for lithium storage with high rate capability and long cycle stability

A highly crystalline three dimensional (3D) bicontinuous hierarchically macro-mesoporous LiFePO₄/C nanocomposite constructed by nanoparticles in the range of 50∼100 nm via a rapid microwave assisted solvothermal process followed by carbon coating have been synthesized as cathode material for high performance lithium-ion batteries. The abundant 3D macropores allow better penetration of electrolyte to promote Li⁺ diffusion, the mesopores provide more electrochemical reaction sites and the carbon layers outside LiFePO₄ nanoparticles increase the electrical conductivity, thus ultimately facilitating reverse reaction of Fe³⁺ to Fe²⁺ and alleviating electrode polarization. In addition, the particle size in nanoscale can provide short diffusion lengths for the Li⁺ intercalation-deintercalation. As a result, the 3D macro-mesoporous nanosized LiFePO₄/C electrode exhibits excellent rate capability (129.1 mA h/g at 2 C; 110.9 mA h/g at 10 C) and cycling stability (87.2% capacity retention at 2 C after 1000 cycles, 76.3% at 5 C after 500 cycles and 87.8% at 10 C after 500 cycles, respectively), which are much better than many reported LiFePO₄/C structures. Our demonstration here offers the opportunity to develop nanoscaled hierarchically porous LiFePO₄/C structures for high performance lithium-ion batteries through microwave assisted solvothermal method.