Abstract
It is desirable to develop an energy storage system with both high energy density and high power density along with excellent cycling stability to meet practical application requirements. Lithium-ion capacitors (LICs) are very promising due to the combined merits of the high power density of electrochemical capacitors and the high energy density of batteries. However, the lack of high rate performance anode materials has been the major challenge of lithium-ion capacitors. Herein, we designed and synthesized holey graphene-wrapped porous TiNb24O62 as an anode material for lithium-ion capacitors. Pseudocapacitive storage behaviors with fast kinetics, high reversibility, and excellent cycling stability were demonstrated. The hybrid material can deliver a high capacity of 323 mAh g−1 at 0.1 A g−1, retaining 183 mAh g−1 at 10 A g−1. Coupled with a carbon nanosheet-based cathode, an LIC with an ultrahigh energy density of 103.9 Wh kg−1 was obtained, and it retained 28.9 Wh kg−1 even under a high power density of 17.9 kW kg−1 with a high capacity retention of 81.8% after 10,000 cycles.
Highlights
With increasing demand for consumer electronics, electronic vehicles (EVs) and hybrid electric vehicles (HEVs), energy storage systems that possess both high energy and high power density as well as long-term stability have attracted more interest in recent years[1,2,3]
The as-synthesized holey graphene-wrapped porous TiNb24O62 microparticles (HG-TNO) material exhibits a high reversible capacity of approximately 323 mAh g−1 at a current of 0.1Ag−1, an outstanding rate capability of 183 mAh g−1 at a high current of 10 A g−1, and an excellent cycling stability of 85% after 1000 charge/discharge cycles
The characteristic peaks of PDA disappeared, and peaks located at 1568 and 1298 cm−1 were observed instead in the HG-TNO-3 sample, which can be ascribed to the C=C and C–O–C stretching in the PDA-derived N-doped carbon (N–C)
Summary
With increasing demand for consumer electronics, electronic vehicles (EVs) and hybrid electric vehicles (HEVs), energy storage systems that possess both high energy and high power density as well as long-term stability have attracted more interest in recent years[1,2,3]. TiNb2O7 and Ti2Nb10O29, have been regarded as promising candidates for high-rate-capability and highenergy-density LIBs anode material, and they have similar working potentials to that of Li4Ti5O12 and possess higher theoretical capacities of 388 and 396 mAh g−1 due to multiple Ti3+/Ti4+, Nb3+/Nb4+, and Nb4+/Nb5+ redox couples, respectively[6,14,15].
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