Pseudocapacitive TiNb 2 O 7 /reduced graphene oxide nanocomposite for high-rate lithium ion hybrid capacitors.

Lithium ion hybrid capacitors (LIHCs) have a capacitor-type cathode and a battery-type anode and are a prospective energy storage device that delivers high energy/power density. However, the kinetic imbalance between the cathode and the anode is a key obstacle to their further development and application. Herein, we prepared TiNb ₂ O ₇ nanoparticles through a facile solvothermal method and annealing treatment. Then a homogeneous three-dimensional (3D) self-supported reduced graphene oxide (rGO)-coated TiNb ₂ O ₇ (TiNb ₂ O ₇ /rGO) nanocomposite was constructed by freeze-drying, followed by a high-temperature reduction, which demonstrates an enhanced pseudocapacitive lithium ions storage performance. Benefiting from the improved electrical conductivity, ultrashort ions diffusion paths, and 3D architecture, the TiNb ₂ O ₇ /rGO nanocomposite exhibits a high specific capacity of 285.0 mA h g ^-1 , excellent rate capability (73.6% capacity retention at 8 A g ^-1 ), and superior cycling stability. More importantly, quantitative kinetics analysis reflects that the capacity of TiNb ₂ O ₇ /rGO is mainly dominated by capacitive behavior, making it perfectly match with the capacitor-type activated carbon (AC) cathode. By using pre-lithiated TiNb ₂ O ₇ /rGO as anode material and AC as cathode material, a high-rate TiNb ₂ O ₇ /rGO//AC LIHC device can be fabricated, which delivers an ultrahigh energy density of 127 Wh kg ^-1 at the power density of 200 W kg ^-1 , a maximum power density of 10 kW kg ^-1 at the energy density of 56.4 Wh kg ^-1 , and durable service life.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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