Scientists from East China Normal University and the Shanghai Institute of Applied Physics have collaborated on a new paper exploring the development of supercapacitor devices for flexible and wearable applications. Their research has appeared in the journalACS Applied Energy Materials。
Study:Flexible High-Energy-Density Hybrid Supercapacitors with Alkaline Hydrogel Electrolytes。Image Credit: mind_photo/Shutterstock.com
Background to the Study
近年来，针对医疗监测，运动检测和软机器人技术等应用的灵活和可穿戴设备的研究已有所增加。这些设备在生物医学科学，采矿和机器人技术等众多领域中找到了研究应用。欧洲杯线上买球这些设备的核心是可靠，安全和高效的电源存储和供应。
Designing materials and device components that can withstand significant deformation whilst retaining their performance is central to this field of electronics. Traditional electrolyte systems cannot meet these demands, being inflexible and susceptible to damage and unable to retain their electrochemical performance under mechanical stress.
Research into alternative, flexible electrolytes has become a key focus in the fields of materials science and microelectronics. Many types of flexible electrolytes have been evaluated for their performance and reliability, including gel electrolytes, polymer electrolytes, and composite electrolytes.
Cycling compressing curves of PEGMA with 3.95 wt% KOH(A)and 1.32 wt% KOH(B)at a compressive strain of 50%. Image Credit: Ni, M et al., ACS Applied Energy Materials
Ionic conductive hydrogels have displayed great promise in the field of flexible electrolytes due to their exceptional mechanical performance and electrical conductivity. Based on their outstanding performance and durability, ionic conductive hydrogel supercapacitors have been designed in recent years to meet the demands of flexible and wearable devices.
Current flexible hydrogel supercapacitors, however, are limited by their low power densities and narrow working window. Furthermore, at high current densities, they suffer from unstable cycle lives, which further hinders their application as flexible energy storage devices.
Some efforts have been made recently to overcome the issues with these electrolytes, including creating zwitterionic hydrogels for use as supercapacitors. Whilst research has demonstrated enhanced electrochemical performance, these hydrogels still suffer from low power densities.
In the past few years, Zn-ion hybrid supercapacitors have emerged as promising candidates. These hydrogel supercapacitors have the benefit of low cost, zinc resource abundance, and non-flammability. Additionally, alkaline aqueous electrolytes have shown promise in recent research due to their ability to improve supercapacitor stability and current density.
在杂化离子导电水凝胶超级电容器中利用碱性电解质，为设计具有较高能量密度和功率密度的设备提供了机会。到目前为止，尚未深入探讨这一研究领域。
(A)CV曲线以不同的扫描速率和(B)在2.0 V的电压窗口中，使用1.32 wt％KOH的GCD曲线使用PEGMA超级电容器的各种密度。(C)具有PEGMA-1.32 wt％KOH的超级电容器的容量在各种当前密度（1-5 A G-1）下。(D)CV曲线以不同的扫描速率和(E)GCD curves at various current densities of supercapacitor of PEGMA using 3.95 wt% KOH in a voltage window of 2.0 V.（F）Capacities of supercapacitor with PEGMA-3.95 wt% KOH at various current densities (1-5 A g-1). Image Credit: Ni, M et al., ACS Applied Energy Materials
研究
该论文提出了一种创新的方法来设计基于水凝胶的柔性超级电容器。在研究中，制备了一种新型碱性离子导电凝胶，并详细分析了其电化学和机械性能。
Acrylamide, MEA, and PEGA were used as polymer chains in the hydrogel, and the prepared material possessed either neutral or alkaline pH. The supercapacitor was constructed from the hydrogel electrolyte, a zinc anode, and an activated carbon cathode. To investigate the supercapacitor’s effectiveness as a real-world device, the authors used it to power an electronic watch.
A universal tensile testing machine was used to evaluate the hydrogel’s compressing properties under a compressive speed of 1 mm min-1。Polymer-water interactions were verified using L-NMR. FTIR, XRD, and SEM tests were used to analyze the prepared hydrogels. Cyclic voltammetry and GCD tests were performed for electrochemical measurements.
Reciprocal of spin-relaxation time of KOH aqueous solution and alkaline gel polymer electrolyte. Image Credit: Ni, M et al., ACS Applied Energy Materials
结果
准备好的水凝胶表现出极好的电导率和良好的机械柔韧性，使其成为高性能柔性和可穿戴设备的吸引力。当用作手表的能源时，超级电容器提供了三周的功率，证明了它作为可穿戴能源存储设备的可靠性。水凝胶表现出极好的弹性。
准备好的超级电容器可以在宽的工作电压中传递高特异性电容，并具有高能量和功率密度。此外，它具有显着的电化学稳定性。在不同的弯曲角度最多180o, the proposed supercapacitor maintained over 95.43% capacity.
After 10,000 cycles, the device maintained near 100% Coulombic efficiency and capacity retention. Furthermore, the results of the practical test demonstrated stable electrochemical performance and excellent flexibility, further demonstrating the suitability of the ionic hydrogel-based supercapacitor presented in the paper.
总之
制备的水凝胶和超级电容器表现出极好的电化学稳定性和对机械变形的抗性。作者观察到多个循环后的容量保留，并成功地将提出的超级电容器应用于电子手表中以证明其实际应用。
根据他们的分析和观察，作者提出，这种柔性碱性离子电解质水凝胶超级电容器可以被认为是在多个下一代柔性和可穿戴电子设备中存储和电源的合适候选者。
进一步阅读
Ni, M et al. (2022) Flexible High-Energy-Density Hybrid Supercapacitors with Alkaline Hydrogel ElectrolytesACS Applied Energy Materials[online] pubs.acs.org. Available at:https://pubs.acs.org/doi/10.1021/acsaem.2c00334
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