Electrician prepares a new type of integrated solid-state flexible super capacitor

Recently, the research team of the Institute of Electrical Engineering of the Chinese Academy of Sciences Ma Yanwei has developed a new type of solid-state flexible supercapacitor with high area specific capacity, excellent charge and discharge cycle performance, and flexibility. The relevant research results were published in the international material journal Adv. Mater (2015, doi:10.1002/adma.201503543) and have applied for national invention patents.

Current solid-state flexible supercapacitors are mostly multi-layer film stacks formed by stacking two self-supporting flexible electrode films and intermediate gel electrolyte films. The high viscosity and diffusion kinetics of the gel limit the diffusivity of the electrolyte ions inside the electrode, so it is difficult to obtain a higher area specific capacitance. In addition, the multilayer stacked device tends to cause mechanical peeling damage between the layers when it is continuously bent, so that the internal resistance of the device rises, and even the overall capacitance performance declines. Therefore, how to prepare a high-performance flexible super capacitor is still full of challenges.

In order to solve these problems, the research team designed the electrode-electrolyte-electrode layer, the key component of the flexible supercapacitor, to be integrated on a single flexible hydrogel film to form an all-in-one novel device structure. 1 shows. Compared with the conventional device structure in which the multilayer film is stacked, this structure is advantageous for the diffusion of the gel electrolyte ions inside the thicker electrode layer and improves the mechanical bending resistance performance.

In the specific preparation process, the team prepared a self-supporting chemical hydrogel film using a chemically crosslinked-cast film method. The film has excellent ionic conductivity (0.082S cm-1) and mechanical tensile properties (can be Stretch to 300%) as shown in Figures 2a-c. Then the conductive polymer was deposited on both the upper and lower surfaces of the hydrogel and the near surface by chemical in-situ polymerization to form a composite hydrogel film. As shown in FIGS. 2d-e, the film has an arrangement of a conductive polymer layer-hydrogel layer-conductive polymer layer inside, and thus an All-in-one integrated solid state flexible supercapacitor can be formed. This new type of structured solid-state flexible supercapacitor has a very outstanding area specific capacity (488 mF cm-2) and excellent charge-discharge cycle stability (no attenuation in the cycle of 10,000 times capacity), as shown in FIG. 3 . In addition, continuous bending thousands of times, its capacitance performance is not attenuated. Excellent performance is expected to make this new type of flexible supercapacitor a power-type energy storage device for next-generation wearable electronic devices.

In the related research work of the research group, the researchers discussed the application of gel electrode materials in solid-state flexible supercapacitors. The researchers prepared conductive polyaniline hydrogel based electrode materials. Compared with the solid electrode material, the gel electrode material exhibits excellent capacitance performance and charge/discharge rate performance due to more sufficient ion reachability. The relevant research results were published in the "Material Chemistry: A Series" of the Royal Society of Chemistry (J. Mater. Chem. A, 2014, 2, 19726).

The above research has received strong support from the National Natural Science Foundation of China and the Institute of Electrical Engineering for the introduction of innovative talents.