Rational design of TiO2(B)@C@Fe3O4 core-shell-branch hybrid nanoarrays as advanced 3D anodes for lithium-ion microbatteries

Three dimensional (3D) electrodes have been proposed to maximize the energy density and power density within a given footprint area for lithium-ion microbatteries. However, current 3D electrodes consisting of a single type of material can hardly achieve high areal capacity, high rate capability and long cycle life simultaneously. In this work, we report a rational design of 3D TiO2(B)@C@Fe3O4 core-shell-branch hybrid nanoarrays on Ti foil by a stepwise hydrothermal method. Combining the high electronic conductivity of two-dimensional structured carbon layer, the large specific capacity of Fe3O4 branch, and the high structure stability of TiO2(B) core, the 3D TiO2(B)@C@Fe3O4 electrode exhibits greatly enhanced electrochemical performance. In specific, the TiO2(B) @C@Fe3O4 anode delivers large specific mass capacity (757 mAh g(-1) at 0.1 mA g(-1)), high areal capacity (similar to 1200 mu Ah cm(-2) at 0.1 mA g(-1)), good rate capability (230 mA h g(-1) at 5 A g(-1)), as well as good cycling stability (93% capacity retention after 200 cycles), outclassing the performance of the bare TiO2(B) and TiO2(B) @C electrodes. This work not only provides a new approach for hybrid core-shell-branch nanoarrays preparation, but also offers an insight into rational design of advanced 3D electrodes for lithium-ion microbatteries.