Nanosheet-assembled hierarchical Li4Ti5O12 microspheres for high-volumetric-density and high-rate Li-ion battery anode

Fast-charging (high-rate) is a critical need for lithium-ion batteries (LIBs). While superior rate performance can be achieved by nanostructured electrodes, their tap density is often low, which leads to low volumetric energy density and limits their practical applications. Here, we report nanosheet-assembled Li4Ti5O12 (LTO) hierarchical microspheres which can simultaneously achieve high tap density, high rate performance and long cycle life. These microspheres were prepared with high yield by facile solvothermal reaction followed by a short thermal annealing process. The formation mechanism of such LTO microspheres was systematically investigated to understand their morphology evolution and phase transformation process. These well-designed hierarchical microspheres with controlled features on both nanometer- and micrometer-scales enable dense particle packing, easy lithium-ion diffusion and high structure robustness. Optimal LTO microspheres can offer extremely high rate capability (e.g., 155 mAh g−1 at 50 C), and excellent cycling stability (99.5% capacity retention after 2000 cycles at 50 C, 95.4% capacity retention after 3000 cycles at 30 C) with a tap density of 1.32 g cm−3. Furthermore, their superior performance was also demonstrated with LiNi0.5Mn1.5O4 cathode in full cells, which showed 93.4% of capacity retention after 1000 cycles at 3C. These results suggest the great promise of using such high-volumetric-density LTO as an anode material for high-rate and long-life LIBs.