Wearable high power flexible lithium-ion capacitors with adjustable areal loading

Flexible power sources are a vital component for smart and wearable electronics. The portability and functionality of these devices are limited by the size, weight, and flexibility of the available batteries. Herein, using the high-pressure solvothermal method, we explored the controllable mass-loading of active materials for flexible lithium-ion capacitor (LIC) and a representative of "PDA-carbon encapsulated reduced graphene oxide supported Ti2Nb10O29" (TNO/rGO@NC) anode and "three-dimensional holey graphene sheets" (HGS) cathode. When using a commercial application mass-loading level of 10.5 mg cm-2 for study, the TNO/rGO@NC anode achieves a high specific areal capacity of 2.4 mAh cm-2 at 0.5C, and 1.2 mAh cm-2 at an ultra-high rate of 50C, while maintaining 92.4% of initial capacity over 500 cycles at 10C. For the cathode part, the HGS shows 125 mAh g- 1 at 1C and no degeneration after 1500 cycles. The assembled LICs achieves a high power density of 6230 kW kg- 1 with 123 Wh kg- 1 energy density, and good cycling retention of 82.2 % over 1000 cycles at 10C in 0.5-4.0 V. The advantages of flexibility, facile shape design, high mass-loading, high energy/power densities make it a promising energy-storage candidate for wearable and smart electronic devices.