TiO₂ polymorphs in 'rocking-chair' Li-ion batteries

This review describes the overall research activities focused on developing high-performance Li-ion batteries (LIBs) fabricated with various TiO₂ polymorphs as insertion anodes. Although several polymorphs of TiO₂ have been reported, only the anatase, rutile, bronze, and brookite phases have proven promising. The bronze phase's lower insertion potential, high reversibility and high current performance makes it an attractive candidate for constructing high power and high energy density Li-ion power packs. In addition, the bronze phase exhibits superior performance over the conventional, commercialized spinel Li₄Ti₅O₁₂ anodes when coupled with the olivine phase LiFePO₄. This exceptional behavior of the bronze phase opens new avenues for the development of high power LIBs capable of powering zero emission transportation and grid storage.