Abstract
With the development of wearable and flexible electronic devices, there is an increasing demand for new types of flexible energy storage power supplies. The flexible supercapacitor has the advantages of fast charging and discharging, high power density, long cycle life, good flexibility, and bendability. Therefore, it exhibits great potential for use in flexible electronics. In flexible supercapacitors, graphene materials are often used as electrode materials due to the advantages of their high specific surface area, high conductivity, good mechanical properties, etc. In this review, the classification of flexible electrodes and some common flexible substrates are firstly summarized. Secondly, we introduced the advantages and disadvantages of five graphene-based materials used in flexible supercapacitors, including graphene quantum dots (GQDs), graphene fibers (GFbs), graphene films (GFs), graphene hydrogels (GHs), and graphene aerogels (GAs). Then, we summarized the latest developments in the application of five graphene-based materials for flexible electrodes. Finally, the defects and outlooks of GQDs, GFbs, GFs, GHs, and GAs used in flexible electrodes are given.
Highlights
In recent years, people have begun to focus on clean and renewable energy such as solar, wind, and hydrogen, due to the energy shortage and environmental damage caused by the continuous consumption of fossil energy and other non-renewable resources [1,2]
As a type of energy storage equipment, supercapacitors have the advantages of long cycle life [6], high power density [7], and good safety [8]
Cai et al [98] found that the metal needle extracted from a medical syringe could be used as a spinneret to synthesize porous pure graphene fibers (GFbs), which exhibited a specific surface area of 839 m2 /g and a specific capacitance of 228 mF/cm2, far exceeding the specific capacitance (47.2 mF/cm2 ) of GFbs prepared with polytetrafluoroethylene (PTFE)
Summary
People have begun to focus on clean and renewable energy such as solar, wind, and hydrogen, due to the energy shortage and environmental damage caused by the continuous consumption of fossil energy and other non-renewable resources [1,2]. The electrode materials includes carbon materials [19], transition metal oxides [20], and conductive polymers [21] Among these materials, carbon materials are electric double-layer capacitor materials, which have the advantages of strong mechanical properties, high specific surface area, and good cycle stability. Carbon materials are electric double-layer capacitor materials, which have the advantages of strong mechanical properties, high specific surface area, and good cycle stability Their specific capacitance is low, resulting in low energy density. Transition metal oxides and conductive polymers are pseudocapacitance materials and exhibit many advantages such as high specific capacitance and a large voltage window, but the cycle stability is poor at high current density [22,23,24,25] the composite electrode materials are designed to fabricate high-performance supercapacitors [26]. Some latest developments in their application to flexible supercapacitors are summarized, and an outlook for the future development of flexible supercapacitors is presented
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