Hierarchical Hollow Microspheres Constructed by Carbon Skeleton Supported TiO_2–<i>x</i> Few-Layer Nanosheets Enable High Rate Capability and Excellent Cycling Stability for Lithium Storage

Rational design and facile synthesis of TiO₂ based hybrid electrodes with hierarchical microstructure have great advantages for exploration of advanced electrodes for lithium-ion batteries (LIBs). We design and synthesize hierarchical hollow microspheres with inner carbon skeleton supported outer TiO_2–<i>x</i> few-layer nanosheets (C@TiO_2–<i>x</i>). The “core–shell” C@TiO_2–<i>x</i> microspheres exhibit relatively high specific surface area and a remarkable electric conductivity (0.264 μS cm^–1). The lithium kinetics of C@TiO_2–<i>x</i> microspheres is significantly improved due to synergistic effects of few-layer TiO_2–<i>x</i> nanosheets and conductive carbon skeleton. The C@TiO_2–<i>x</i> microspheres manifest an excellent reversible capacity of 323 mAh g^–1, together with an ultralong cycling lifetime that the capacity shows ∼220 mAh g^–1 after 1000 cycles at 1.0 C. The C@TiO_2–<i>x</i> microspheres also deliver a relatively high performance in rate capacity (108 mAh g^–1 at 20 C). When they are assembled into a hybrid lithium-ion capacitor, relatively high capacitance of 58 F g^–1 is achieved so that high power density reaches 14 kW kg<sup>–1