Mitigating effects of polysulphide shuttle in lithium polysulphide flow batteries

能量存储被视为净零能耗格局的关键组成部分，氧化还原液流电池相对于其他类型的电池具有独特的优势，可以实现灵活、持久和长时间的存储。该项目将与液流电池制造商StorTera有限公司合作开发一种多硫化锂单液液流电池，由于硫的高度丰度和使用回收锂的能力，这有望成为一种非常低成本、可持续的解决方案。多年来，锂硫电池一直在开发中，其能量密度(2600W h kg-1)有望比锂离子电池(高达260W h kg-1)高10倍。将Li-S电池商业化面临重大挑战，例如，由于多硫化物的传输和还原(称为多硫化物穿梭)，库仑效率较低。锂和硫的聚合物(Li2Sn，n=3-8)，随着电池放电而变短，应该留在阴极侧，但可以扩散到阳极，导致自放电。已有多种技术被应用于抑制穿梭，如制造新的电极结构和配方，以及添加锂钝化剂(LiNO3)以通过在阳极上形成固体电解质界面(SEI)来抑制穿梭。另一种选择是配置电池，其中阴极由可溶多硫化物的溶液组成，并与电极分开。这种结构具有锂金属阳极和石墨阴极，多硫化物溶液(阴极)通过电池泵送，被称为单液体氧化还原液流电池(SLIQ)。该项目的目的是通过对多硫化锂SLIQ的分析，寻求对多硫化物穿梭效应和不同荷电状态下硫的形态的更好的了解。这将通过使用各种技术来实现，例如：光谱电化学，以监测放电/充电循环期间阴极液中硫的形态；电化学石英晶体微天平，以确定在锂阳极上形成的SEI层的沉积速度和成分。将这些技术与循环伏安法和阻抗谱等典型的电化学特性相结合，将创建一个工具包，用于分析将被考虑在系统中使用的未来材料。

Energy storage is seen as a crucial component of a net zero energy landscape, and redox flow batteries have particular advantages over other battery types to enable flexible, long-lasting and long-duration storage. This project will work with flow battery manufacturer StorTera Ltd to develop a lithium polysulphide single-liquid flow battery, which promises to be a very low cost, sustainable solution thanks to the high abundance of sulphur and ability to use recycled lithium. Lithium-sulphur batteries have been under development for many years, with the promise of 10x higher energy density (2600 W h kg-1) than Li-ion batteries (up to 260 W h kg-1). There are major challenges to commercialise the Li-S cell such as a low coulombic efficiency due to the transport and reduction of polysulphides, known as polysulphide shuttle. Polymers of lithium and sulphur (Li2Sn , n=3-8), which get shorter as the battery discharges, should stay on the cathode side but can diffuse to the anode and cause self-discharge. A variety of technologies have been applied to inhibit the shuttle such as making new electrode constructions and formulations as well as the addition of lithium passivating agents (LiNO3) to inhibit the shuttle by forming a solid electrolyte interphase (SEI) on the anode. An alternative option is to configure a battery where the cathode consists of a solution of the soluble polysulphide compounds and is kept separate from the electrodes. This configuration has a lithium metal anode and graphite cathode with the polysulphide solution (catholyte) being pumped through the cell, known as a single liquid redox flow battery (SLIQ).The aim of this project is to seek a greater understanding of the polysulphide shuttle effect and the speciation of sulphur at different states of charge by analysis of the lithium polysulphide SLIQ. This will be achieved by utilising a variety of techniques, such as; spectroelectrochemistry to monitor the speciation of sulphur in the catholyte during a discharge/charge cycle; electrochemical quartz crystal microbalance to determine the deposition rates and composition of the SEI layer formed on the lithium anode. A combination of these techniques alongside typical electrochemical characterisations such as cyclic voltammetry and impedance spectroscopy will create a toolkit for analysis of future materials that will be considered for use in the system.