High-performance spinel-rich Li_1.5MnTiO_4+δ ultralong nanofibers as cathode materials for Li-ion batteries

Recently, composite materials based on Li-Mn-Ti-O system were developed to target low cost and environmentally benign cathodes for Li-ion batteries. The spinel-layered Li_1.5MnTiO_4+δ bulk particles showed excellent cycle stability but poor rate performance. To address this drawback, ultralong nanofibers of a Li_1.5MnTiO_4+δ spinel-layered heterostructure were synthesized by electrospinning. Uniform nanofibers with diameters of about 80 nm were formed of tiny octahedral particles wrapped together into 30 μm long fibers. The Li_1.5MnTiO_4+δ nanofibers exhibited an improved rate capability compared to both Li_1.5MnTiO_4+δ nanoparticles and bulk particles. The uniform one-dimensional nanostructure of the composite cathode exhibited enhanced capacities of 235 and 170 mAh g^-1 at C/5 and 1 C rates, respectively. Its unique structure provided a large effective contact area for Li⁺ diffusion, and low charge transfer resistance. Moreover, the layered phase contributed to its capacity in over 3 V region, which increased specific energy (726 Wh kg^-1) compared to the bulk particles (534 Wh kg^-1).