2024 AIChE Annual Meeting
Enhanced Performance of Lithium-Sulfur Batteries with Trace Water Electrolyte
With the growing demand for energy storage systems capable of delivering high energy densities, lithium-sulfur (Li-S) batteries have emerged as a promising solution. These batteries offer a significantly higher theoretical specific capacity of 1672 mAh/g, which exceeds the capacities of many conventional battery technologies. The reason behind this high capacity lies in the two-electron transfer per sulfur atom, which enables efficient energy storage. However, the practical realization of this potential is hindered by the polysulfide shuttling effect. This phenomenon occurs when intermediate lithium polysulfides (Li2Sx, 4<x<8) formed during the discharge process dissolve into the electrolyte and migrate to the lithium anode. These polysulfides can react with the lithium anode, leading to capacity loss and reduced battery efficiency. One of the strategies to mitigate the polysulfide shuttling effect is to modify the electrolyte. Some works add lithium nitrate to protect the lithium anode to stop the direct reaction of the polysulfides with the lithium anode while others change the solvents to decrease the solubility and mobility of the polysulfides. In our research, we explore an approach by adding trace amounts of water to the electrolyte to restrict the mobility of polysulfides. Through this modification, the shuttling of polysulfides is significantly reduced, preventing their unwanted interactions with the lithium anode. Initial charge-discharge tests conducted on coin cells demonstrate a promising outcome: the introduction of 1000 ppm (parts per million) of water into the electrolyte results in a 25% improvement in specific capacity. However, the amount of water added must be carefully controlled. While trace amounts enhance performance, excessive water can degrade the battery's lifecycle by promoting side reactions that impact stability and longevity. Achieving the right balance between improving specific capacity and maintaining battery longevity is critical to advancing Li-S battery technology. Our research contributes to the ongoing optimization of electrolyte formulations, potentially bringing Li-S batteries closer to commercial viability and supporting future energy storage needs.