Rigid TiO 2- x coated mesoporous hollow Si nanospheres with high structure stability for lithium-ion battery anodes.

Rigid oxygen-deficient TiO 2- x coated mesoporous hollow Si nanospheres with a mechanically and electrically robust structure have been constructed through a facile method for high-performance Li-ion battery anodes. The mesoporous hollow structure provides enough inner void space for the expansion of Si. The oxygen-deficient TiO 2- x coating has functions in three aspects: (1) avoiding direct contact between Si and the electrolyte; (2) suppressing the outward expansion of the mesoporous hollow Si nanospheres; (3) improving the conductivity of the composite. The combined effect leads to high interfacial stability and structural integrity of both the material nanoparticles and the whole electrode. By virtue of the rational design, the composite yields a high reversible specific capacity of 1750.4 mA h g -1 at 0.2 A g -1 , an excellent cycling stability of 1303.1 mA h g -1 at 2 A g -1 with 84.5% capacity retention after 500 cycles, and a high rate capability of 907.6 mA h g -1 even at 4 A g -1 .