A highly flexible graphene free-standing film with hierarchical structure is prepared by a facile template method. With a porous structure, the film can be easily bent and cut, and forms a composite with another material as a scaffold. The 3D graphene film exhibits excellent rate capability and its capacitance is further improved by forming a composite with polyaniline nanowire arrays. The flexible hierarchical composite proves to be an excellent electrode material for flexible supercapacitors.

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With the enormous development of the electric vehicle market, fast charging battery technology is highly required. However, the slow kinetics and lithium plating under fast charging condition of traditional graphite anode hinder the fast charging capability of lithium‐ion batteries. To develop anode materials with rapid Li‐ions diffusion capability and fast reaction kinetics has received widely attentions. This review summarizes the current status in the exploration of fast charging anode materials, mainly including the critical challenge of achieving fast charging capability, the inherent structures and lithium storage mechanisms of various anode materials, as well as the recent progress to improve the rate performance involving morphology regulation, structure design, surface/interface modification, as well as forming multiphase systems. Finally, the challenges and future directions of developing fast charging Li‐ion batteries are highlighted.

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Different from solid electrodes, conducting polymer hydrogel electrodes swollen with water and ions, can reach contact with the electrolyte solution at the molecular level, which will result in more efficient electrochemical process of supercapacitors. Besides, the inherent soft nature of hydrogel material offers the electrode superior flexibility, which benefits to gain high flexibility for devices. Here, this perspective briefly introduces the current research progress in the field of conducting polymer hydrogel electrodes-based flexible solid-state supercapacitor and gives an outlook on the future trend of research.Keywords: Conducting polymer hydrogels, flexible supercapacitor, soft electrode, polyaniline, integrated device Nowadays, flexible energy storage devices (batteries and supercapacitors) have received widely attentions as the rapid progress of flexible and wearable electronics [1,2]. Flexible solid-state supercapacitors represent a new type of supercapacitor that can work under consecutive bending, stretching and even twisting states [3][4][5]. However, it remains a large challenge to obtain a flexible solid-state supercapacitor with high electrochemical performance and superior flexibility. The performance of a flexible supercapacitor mainly depends on the properties of electrode materials and the device configuration [6]. The electrode materials of supercapacitor include various nanocarbons, conducting polymers and transition metal oxides [7][8][9][10][11][12]. Conducting polymer electrodes possess several merits, such as high electric conductivity, large capacitance, inherent flexibility and easy to processing [13][14][15][16][17][18]. However, the separations of the molecular chains in conducting polymers are generally small relative to the double layer thickness, which results in low capacitance [19]. Besides, the low ionic mobility in the polymer matrix reduces the maximum power density of such electrodes [20].On the other hand, the current device configuration of the flexible solid-state supercapacitor somewhat hinders the device to gain better performance. Generally, a flexible solid-state supercapacitor consists of a "sandwich" laminated structure, including two flexible solid electrodes and the middle gel polymer electrolyte layer [21]. In terms of this structure, the solid electrode materials hardly make a sufficient contact with the gel polymer electrolyte that possesses large viscosity and poor diffusion, which results in low capacitance and sluggish the electrochemical response.Hydrogel is made up of solid three-dimensional polymeric networks and large amounts of water medium [22]. Generally, the hydrogels are employed as solid-state electrolyte of supercapacitors, such as polyvinyl alcohol (PVA) gel polymer electrolyte. Recently, conducting polymer hydrogels were used as electrode materials for supercapacitors instead of traditional solid electrodes [19,[23][24][25]. This "aqua material electrode" is conducting polymer matrix swollen with water and ions, which hence produce a...

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