Materials for Supercapacitor Separators

超级电容器隔膜材料

• 批准号: 2105107
• 金额: --
• 依托单位: University of Surrey
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2105107
• 关键词: Materials; Supercapacitor; Separators

One of the main technological concerns for the uptake of renewable energy sources and the strive for more efficient and transport systems is the lack of high power and high energy storage capabilities. The Supercapacitor is one of the most promising technologies to fulfil our growing need for electrical energy storage as the power output of supercapacitors can reach up to 10kW kg-1 but lack in energy density compared to that of batteries. Currently, a considerable amount of research is focused on the production of high capacitive electrode materials, to increase the energy density of these devices without sacrificing the innate power density. This has been mainly using high specific surface area carbon material or redox active pseudocapacitive elements.An important yet often overlooked component of the device is the separator material, which provides a physical barrier between the electrodes to prevent shorting and high porosity to allow the flow of electrolyte for charging and discharging. Traditionally micro-porous membranes such as polyethylene and polypropylene are used as electrode separators due to their chemical stability and their significant mechanical properties. However, these materials suffer from low porosity, resulting in weak ion conductivity which inhibits charge/discharge rates within the device. Polyvinylidene fluoride (PVDF) nanofibers have been seen to exhibit an ionic conductivity of over 1.8 mScm-1 as they provide low interfacial resistance and higher ion diffusion rate due to the controllable porosity when manufacturing via electrospinning [1]. What's also interesting about these PVDF materials is that they are one of the few polymer materials that exhibit piezoelectric properties being able to crystallise into 4 different phases. This has opened opportunities for providing multifunctionality with supercapacitor devices, as replacing the separator material with (beta) phase crystallized PVDF has let to research in the development of enhanced supercapacitor devices with the benefit of self-charging under the influence of mechanical force [2]. Mechanical stress upon the device will induce an internal electric field upon the separator, forcing ions in the electrolyte to separate to the cathode and anode, thus self-charging of the device upon application of a mechanical force. This project sets out to study the effect of incorporating both piezoelectric energy harvesting and supercapacitor energy storage into one device. Focussing on experiments to optimise the separator component in the aim to maximise ionic conductivity and provide a high piezoelectric coefficient for charge separation and self-charging. Studies will go beyond the current research into the use of PVDF nanofibers, exploring different piezoelectric polymer nanostructures such as Nylon-11, which has been shown to inhibit strong piezoelectric behaviours [3]. Fabrication of device components will be based on electrospinning of polymer nanofibers and carbon fibre electrodes to produce high power density devices with fast self-charging capabilities.

吸收可再生能源和努力提高效率和运输系统的主要技术问题之一是缺乏高功率和高能量储存能力。超级电容器是满足我们日益增长的电能存储需求的最有前途的技术之一，因为超级电容器的功率输出可以达到10 kW kg-1，但与电池相比，能量密度不足。目前，大量的研究集中在高电容电极材料的生产上，以在不牺牲固有功率密度的情况下增加这些器件的能量密度。这主要是使用高比表面积的碳材料或氧化还原活性赝电容元件。设备的一个重要但经常被忽视的组件是隔膜材料，它在电极之间提供物理屏障以防止短路，并提供高孔隙率以允许电解质流动以进行充电和放电。传统上，微孔膜如聚乙烯和聚丙烯由于其化学稳定性和显著的机械性能而被用作电极隔膜。然而，这些材料的孔隙率低，导致离子传导性弱，这抑制了装置内的充电/放电速率。聚偏二氟乙烯（PVDF）纳米纤维已被视为表现出超过1.8 mScm-l的离子电导率，因为当通过静电纺丝制造时，由于可控的孔隙率，它们提供低界面电阻和较高的离子扩散速率[1]。这些PVDF材料的另一个有趣之处在于，它们是少数几种表现出压电特性的聚合物材料之一，能够结晶成4种不同的相。这为超级电容器装置提供多功能性提供了机会，因为用（β）相结晶的PVDF代替隔膜材料使得研究开发增强型超级电容器装置，其具有在机械力的影响下自充电的益处[2]。装置上的机械应力将在隔板上诱导内部电场，迫使电解质中的离子分离到阴极和阳极，从而在施加机械力时装置自充电。该项目旨在研究将压电能量收集和超级电容器能量存储整合到一个设备中的效果。专注于优化分离器组件的实验，旨在最大限度地提高离子电导率，并为电荷分离和自充电提供高压电系数。研究将超越目前使用PVDF纳米纤维的研究，探索不同的压电聚合物纳米结构，如尼龙-11，它已被证明可以抑制强压电行为[3]。设备组件的制造将基于聚合物纳米纤维和碳纤维电极的静电纺丝，以生产具有快速自充电能力的高功率密度设备。