| Supercapacitors（SCs）are cost-effective energy storage devices with high capacity,stable operation,short charging time and low environmental impact.The main factors affecting the performance of SC are the physical and chemical properties and structure of the active material,which is why attention has been paid to the development of active materials.Compared to other active materials,carbon is fascinatingly stable,highly conductive and inexpensive,making it one of the most sought-after research targets.Carbon fibre（CF）materials are often used in the development of flexible SC materials because they are easy to handle and have excellent mechanical flexibility.This paper therefore focuses on the in situ growth of metal oxides on CF as a flexible substrate by the hydrothermal method and explores its essential properties.（1）In this work,we designed a photoassisted SC electrode（Ti O2/CF）that integrates photoelectrode（Ti O2）and capacitive electrode（CF）to realize photoelectric cooperative charge storage.It was found that spherical titanium dioxide precursors collide,expand,integrate,stretch and tear to form a network structure.The mesh of titanium dioxide ensures lighting and can increase the utilization of solar energy.Compared with the dark condition,the capacitive performance of Ti O2/CF electrode under light condition is significantly increased by about 1.9 times.In addition,the Ti O2/CF photoassisted electrode can still reach99.19% capacitance after 5000 cycles,showing its long life.In addition,the enhancement mechanism is expounded: these high-energy photoelectrons will participate in charge transfer,thereby increasing the total energy of the process and thus improving the capacitance performance.In addition,these photoelectron-hole pairs act as additional charge carriers to facilitate charge accumulation.This work may offer new prospects for developing light-assisted energy systems that harness solar energy.（2）In this work,we synthesized a composite material（CF/Ti O2）of honeycomb structure Ti O2 and CF,which was used as an electrode material for flexible SC.The in situ growth of Ti O2 significantly increased the specific surface area（SSA）of CF.In addition,we propose an effective strategy to improve the intrinsic conductivity of Ti O2 by constructing oxygen defects through Na BH4 solution.Surprisingly,the reduced CF/Ti O2 electrode exhibited the highest specific capacity of 115.2 F g-1 at 1200 m A g-1.In addition,its capacity retention rate maintains 98.37% capacitance after 10,000 cycles,demonstrating its long life.In addition,we also performed density functional theory（DFT）analysis to reveal the enhancement mechanism of oxygen defects on electrode performance.In addition,the aqueous symmetric ultracapacitors based on CF/R-Ti O2 exhibit a high energy density of 49.6 WH kg-1 at a power density of 1440 W kg-1.At the same time,the assembled quasi-solid flexible SC exerts good flexibility.The results show that the synergistic effect of oxygen defect and honeycomb structure gives CF/R-Ti O2 electrode great potential in application.（3）In this work,we report the application of in situ growth of mixed metal oxides（R-Ti O2/WO3）containing oxygen vacancies on CF surfaces to flexible SC.It is found that the synergistic effect of Ti O2/WO3 heterojunction and oxygen vacancy engineering can significantly reduce work function and accelerate charge transport at electrode/electrolyte interface,thus significantly improving the electrochemical performance.At 1000 m A g-1,the specific capacity of R-Ti O2/WO3/CF electrode is 102 F g-1.At a power density of 2160 W kg-1,the aqueous symmetric ultracapacitors based on R-Ti O2/WO3/CF exhibit an energy density of61.2Wh kg-1.In addition,the assembled all-solid flexible SC has good stability and flexibility.The oxygen-vacancy rich R-Ti O2/WO3/CF composite shows great potential in the next generation of intelligent energy systems due to its convenient assembly,good flexibility and excellent electrochemical performance. |
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