Free-standing TiNb6O17/rGO composites as a superior anode host for high-performance Li-ion capacitor

Li-ion capacitors are very enticing power sources having high energy and power density as they exemplify the benefits of both Lithium-ion battery (LIB) and supercapacitors (SCs) together. However, the high performance of LIC is limited due to low specific capacity and slow reaction kinetics of electrodes. Herein, pseudo-capacitive titanium niobium oxide (TiNb6O17: TNO) and reduced graphene oxide (rGO) composite material was fabricated and investigated as a unique anode material for LIC. The application of TNO-rGO composite electrode (RTNO) as insertion anode material in LIC has been investigated due to its excellent electrochemical performance, intrinsic fast pseudo-capacitive behavior along with good reversibility and cyclability. A novel LIC was fabricated using R-TNO electrode as an innovative insertion type anode and activated carbon (AC) as cathode for the first time. Compared to conventional method (with binder), here the electrodes are prepared using binder-free and current-collector tape casting method to further enhance the energy and power density. As a result, the flexible and free-standing electrodes were acquired and used as anode for flexible LIC application. Comprehensive electrochemical analysis elucidates the improved storage behavior of composite electrode with rapid reaction kinetics, high reversibility and excellent cyclic stability. Novel R-TNO/AC LIC exhibited maximum energy density of 142.10 Wh/kg and power density of 18.75 kW/kg. The LIC device illustrated 88% cyclic stability even after 10,000 cycles, confirming its good electrochemical stability during electrochemical process. The extraordinary performance of LIC device is ascribed to collective effect of pseudo-capacitive behavior of TiNb6O17 particles and the buffering effect provided by rGO sheets. The results obtained are encouraging and propose the utilization of fabricated intercalation anode materials for the development of safe and high performance LICs.