Hierarchical flower-like NiCo2O4@TiO2 hetero-nanosheets as anodes for lithium ion batteries
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Zhigao
Huang
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Abstract
Flower-like NiCo2O4 consisting of nanosheets are synthesized by hydrothermal technique and subsequently surface-modified with a TiO2 ultrathin layer by a hydrolysis process at low temperature. It is found that NiCo2O4@TiO2 exhibits superior electrochemical performances over NiCo2O4 in terms of rate capability and cyclability. After 60 cycles at 100 mA g−1, NiCo2O4@TiO2 showed 78% capacity retention compared with 57% for bare NiCo2O4. Analysis from the electrochemical measurements indicates that the improved electrochemical performances of NiCo2O4@TiO2 might be attributed to a higher lithium diffusion rate, smaller charge-transfer resistance and more structural stability. Kelvin probe force microscopy measurements reveal that NiCo2O4@TiO2 has a lower work function than those of the pristine one, which help to facilitate electron transfer in composites. In addition, the electric field between NiCo2O4 and TiO2 resulting from the difference in work functions is also expected to enhance the electrochemical performances.
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