Carbon-coated SiO 2 /TiO 2 (SiO 2 /TiO 2 @C) nanosheets consisting of TiO 2 nanoparticles uniformly embedded in SiO 2 matrix and a carbon-coating layer are fabricated by using acidified titanosilicate JDF-L1 nanosheets as template and precursor. SiO 2 /TiO 2 @C has unique structural features of sheetlike nanostructure, ultrafine TiO 2 nanoparticles distributed in SiO 2 matrix, and carbon coating, which can expedite ion diffusion and electron transfer and relieve volume expansion efficiently, and thus, the synergetic combination of these advantages significantly enhances its Li storage capability. As anode of lithium-ion batteries (LIBs), SiO 2 /TiO 2 @C nanosheets exhibit a high capacity of 998 mAh g −1 at 100 mA g −1 after 100 cycles. Moreover, an ultrahigh capacity of 410 mAh g −1 retains at 2000 mA g −1 after 400 cycles. A mixed reaction mechanism of capacitance and diffusioncontrolled intercalation is revealed by qualitative and quantitative analysis.
TiO2-based nanocomposites w ith rationally designed size, structure and composition are highly desirable for Na-ion storage. In this w ork, various TiO2/N-doped porous carbon nanocomposites (TiO2/NC) have been fabricated by directly carbonizing NH2-MIL-125(Ti) at different temperatures. These TiO2/NC nanocomposites exhibit unique structure features, such as ultrafine TiO2 nanoparticl es, micro-mesoporous structure, and N-doped carbon coating, whi ch can shorten the Na ions diffusion distance, enhance the electroni c conductivity, and prevent nanosized-TiO2 from aggregation. When applied as sodium ion battery anodes, TiO2/NC-600 exhibits the best sodium storage properties among the TiO2/NC nanocomposites produced at different carbonization temperatures. The correlations betw een electrochemical properties and size/structure/compositi on of the TiO2/NC nanocomposites are disclosed. TiO2/NC-600 delivers a high reversible capacity of 190 mA h g -1 up to 500 cycles at 1 C (1 C = 335 mA g -1 ), an ultrahigh capacity of 76 mA h g -1 at a high rate of 20 C, and an excellent long-term cycling stability w ith a capacity of 159 mA h g -1 retained after 2500 cycles at 5 C. The outstanding sodium storage performances of TiO2/NC-600 are attributed to the appropriate crystalline structure, particle size and high nitrogendoping content.
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