Three-dimensional hierarchical wreath-like Co3O4@ TiO2 as an anode for lithium-ion batteries

Wreath-like Co 3 O 4 particles consisting of microplates are synthesized by a facile solvothermal method and subsequently surface-modified with TiO 2 ultrathin layer using a low-temperature hydrolysis process. Comparing with pure Co 3 O 4 , Co 3 O 4 @TiO 2 exhibits superior electrochemical performances in terms of reversible capacity, rate capability and cycling stability. Co 3 O 4 @TiO 2 exhibits high reversible capacity of 813.0 mAhg −1 at 500 mAg −1 after 180 cycles while the pristine Co 3 O 4 only has a discharge capacity of 512.5 mAhg −1 . The filling of TiO 2 nanoparticles in porous Co 3 O 4 sheets and the TiO 2 -coating on Co 3 O 4 surface, could effectively suppress large volume expansion of Co 3 O 4 and consequently enhance structural stability during the Li-ion insertion/extraction processes. Analysis from the electrochemical measurements reveals that the improved performances should be attributed to reduced the charge-transfer resistance and enhanced Li-ion diffusion kinetics because of TiO 2 -coating. In addition, the reduced work function induced by TiO 2 -coating is helpful to facilitate electron transfer in composites. Moreover, the built-in electric field resulting from the difference in work function between Co 3 O 4 and TiO 2 , would facilitate electron-transfer and Li-ion migration across heterojunction interfaces.