3,3'-二硫代二丙酸作为锂硫电池功能电解质添加剂的研究

3,3'-dithiodipropionic acid as a functional electrolyte additive in lithium-sulfur battery

锂硫电池由于其高理论容量、高能量密度以及较低的原料价格,被认为是目前最具潜力的储能电池之一。但是在实际应用中,锂硫电池的发展受到充放电过程中的“穿梭效应”和低活性材料利用率等的限制。本文探究了一种新型电解质添加剂3,3′-二硫代二丙酸(DTPA)对锂硫电池电化学性能提高的影响机制。结果表明,DTPA添加剂能与分散在电解液中的多硫化物相互作用,促进长链多硫化物转化为Li2S2和Li2S,从而缓解长链多硫化物向阳极的穿梭行为,提高氧化还原动力学和活性物质的利用率。添加DTPA后,锂硫电池的电化学性能得到了提高,在0.5C下,使用了1.5 wt.%DTPA作为电解液添加剂的锂硫电池初始循环容量为1093.4 mA·h/g,经过250次循环后容量为714.8 mA·h/g。此外,含DTPA的电池具有更高的电化学稳定性,其在2C下相对于0.1C的容量保持率为57.5%。本文的研究结果证明,DTPA作为电解质添加剂对锂硫电池的性能提高具有显著效果,为减少多硫化物的穿梭效应以增加锂硫电池的容量提供了一种可行的解决方案。

High-energy-density lithium-sulfur(Li-S)batteries are among the most promising energy storage devices,but their potential has been constrained by the shuttle effect and poor active material utilization.Here,3,3'-dithiodipropionic acid(DTPA),an efficient electrolyte additive,is applied to Li-S batteries while its underlying mechanism on the electrochemical performance is examined.The results show that the DTPA additive can quickly interact with the polysulfides scattered in the electrolyte,facilitating the conversion of long-chain polysulfides to Li2S2 and Li2S.In this way,by lessening the shuttle effect of long-chain polysulfides towards the anode,the redox kinetics and the usage of active materials can both be improved.The electrochemical performance of Li-S batteries is thus enhanced by the addition of DTPA,with capacities of 1093.4 mA∙h/g for the initial cycle and 714.8 mA·h/g after 250 cycles at 0.5C(DTPA concentration is 1.5 wt.%).Also,the DTPA-containing batteries have higher electrochemical stability,with a capacity retention rate of 57.5%relative to 0.1C at 2C.The improved performance demonstrates the importance of electrolyte additives,and the DTPA introduced in this work offers a potential solution for reducing the shuttle effect of polysulfide to increase the capacity of Li-S batteries.