Mitigating effects of polysulphide shuttle in lithium polysulphide flow batteries

储能被视为净零能耗环境的关键组成部分，氧化还原液流电池在实现灵活、持久和长时间存储方面具有优于其他电池类型的特殊优势。该项目将与液流电池制造商StorTera Ltd合作开发一种多硫化锂单液流电池，由于硫的高丰度和使用回收锂的能力，该电池有望成为一种成本非常低的可持续解决方案。锂硫电池已开发多年，其能量密度（2600 W h kg-1）比锂离子电池（高达260 W h kg-1）高10倍。Li-S电池的商业化面临着重大挑战，例如由于多硫化物的运输和还原而导致的低库仑效率，称为多硫化物穿梭。锂和硫的聚合物（Li 2Sn，n=3-8）随着电池放电而变短，应该停留在阴极侧，但可以扩散到阳极并引起自放电。已经应用了多种技术来抑制穿梭，例如制造新的电极构造和配方以及添加锂钝化剂（LiNO 3）以通过在阳极上形成固体电解质中间相（SEI）来抑制穿梭。另一种选择是配置一种电池，其中阴极由可溶性多硫化物化合物的溶液组成，并与电极保持分离。这种配置具有锂金属阳极和石墨阴极，多硫化物溶液（阴极电解液）被泵送通过电池，被称为单一液体氧化还原液流电池（SLIQ）。该项目的目的是通过分析多硫化锂SLIQ来寻求对多硫化物穿梭效应和不同电荷状态下硫的形态的更好理解。这将通过利用各种技术来实现，例如：光谱电化学，以监测在放电/充电循环期间阴极电解液中硫的形态;电化学石英晶体微天平，以确定在锂阳极上形成的SEI层的沉积速率和组成。将这些技术与典型的电化学表征（如循环伏安法和阻抗谱）相结合，将创建一个工具包，用于分析将被考虑用于系统的未来材料。

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.