Soft-template construction of three-dimensionally ordered inverse opal structure from Li2FeSiO4/C composite nanofibers for high-rate lithium-ion batteries.

Exploring a new method to fabricate small-sized nanofibers is essential to achieve superior performances for energy conversion and storage devices. Here, a novel soft-template strategy is developed to synthesize a three-dimensionally ordered macroporous (3DOM) architecture constructed from small-sized nanofibers. The effectiveness of a nanofiber-assembled three-dimensional inverse opal material as an electrode for high-rate lithium-ion batteries is demonstrated. The small-sized Li2FeSiO4/C composite nanofibers with a diameter of 20-30 nm are grown by employing a tri-block copolymer P123 as a structure directing agent. Accordingly, the macro-mesoporous hierarchical 3DOM architecture constructed from Li2FeSiO4/C nanofibers is further templated from P123 for the nanofibers and a polystyrene colloidal crystal array for the 3DOM architecture. We find that the thermal stability of the nanofiber morphology depends on the self-limited growth of Li2FeSiO4 nanocrystals in a crystalline-amorphous hybrid. As a cathode for a lithium-ion battery, the 3D hierarchical macro-mesoporous cathodes exhibit outstanding high-rate and ultralong-life performances with a capacity retention of 84% after 1500 cycles at 5 C in the voltage window of 1.5-4.5 V, which is greatly improved compared with a simple 3DOM Li2FeSiO4/C nanocomposite.

Three-dimensionally ordered macroporous Li3V2(PO4)3/C nanocomposite cathode material for high-capacity and high-rate Li-ion batteries.

A three-dimensionally ordered macroporous (3DOM) Li3V2(PO4)3/C cathode material with small-sized macropores (50-140 nm) is successfully synthesized using a colloidal crystal array. The 3DOM architecture is built up from fully densely sintered Li3V2(PO4)3/C nanocomposite ceramics particles. Such a 3DOM Li3V2(PO4)3/C micrometer sized particle combines the advantages of both Li3V2(PO4)3 nanocrystal and micrometer sized particle. The resultant 3DOM Li3V2(PO4)3/C nanocomposite exhibits a stable and highly reversible discharge capacity up to 151 mA g(-1) at 0.1 C, and an excellent high-rate capability of 132 mA g(-1) at 5 C in the voltage range of 3.0-4.4 V. Compared to the corresponding bulk nanocomposite, the 3DOM Li3V2(PO4)3/C cathode exhibits a significantly improved high-rate performance, which promises new opportunities in the development of high energy and high power lithium-ion batteries.