Batteries are everywhere in everyday life, from mobile phones and smart watches to the growing number of electric vehicles. Most of these devices use the well-known batteries” lithium-ion batteries. And although lithium-ion batteries have come a long way since they were first introduced, they also have some known disadvantages, such as short life, overheating, and power chain challenges for certain raw materials.
Scientists at the US Department of Energy’s (DOE) Argonne National Laboratory are investigating solutions to these problems by testing new materials in battery construction. One such material is sulfur. Sulfur is extremely abundant and cost-effective, and can hold more energy than traditional ion batteries.
In a new study, researchers have advanced sulfur-based battery research by creating a layer in the battery that increases energy storage capacity while nearly eliminating the traditional sulfur battery problem of corrosion.
Wenqian Xu, beamline scientist at APS said “These results show that a redox-active interlayer could have a huge impact on the development of Li-S batteries. We are one step closer to seeing this technology in our everyday lives”.
A promising battery design combines a sulfur-containing positive electrode (cathode) with a lithium metal negative electrode (anode). Among these components is an electrolyte, or substance that allows ions to pass between the two ends of the battery.
Earlier lithium-sulfur (Li-S) batteries did not perform well because sulfur species (polysulfides) dissolved in the electrolyte and caused it to corrode. This polysulfide pendulum effect negatively affects battery life and reduces the number of times the battery can be recharged.
To avoid this polysulfide shuttling, previous researchers attempted to place a redox-inactive interlayer between the cathode and anode. The term “redox-inactive” means that the material does not undergo reactions like an electrode. However, this protective interlayer is heavy and dense, which reduces the energy storage capacity per unit weight of the battery. It also doesn’t reduce the commute enough. This has proven to be a major obstacle to the commercialization of Li-S batteries.
To solve this problem, the researchers developed and tested a porous sulfur-containing interlayer. Tests in the laboratory showed an initial capacity about three times higher in Li-S cells with this active, as opposed to inactive, interlayer. Even more impressively, the cells with the active interlayer maintained their high capacity for 700 charge-discharge cycles.
Guiliang Xu, an Argonne chemist and co-author of the pape says “Previous experiments with cells with a redox-inactive layer only suppressed the shuttle, but in doing so sacrificed energy for a given mass of the cell because the layer added extra weight, on the contrary, our redox-active layer increases the energy storage capacity and suppresses the shuttle effect.”
To further study the redox active layer, the team conducted experiments at the 17-BM beamline of Argonne’s Advanced Photon Source (APS), a DOE Office of Science user facility. Data obtained from exposing cells with this layer to X-rays allowed the team to discover the benefits of the interlayer.
Wenqian Xu, a beam scientist at APS also says “The data confirmed that the redox-active interlayer can reduce shuttling, reduce harmful reactions in the battery, and increase the battery’s capacity to hold more charge and last more cycles. These results show that a redox-active interlayer could have a huge impact on the development of Li-S batteries, we are one step closer to seeing this technology in our everyday lives.”
In the future, the team wants to evaluate the growth potential of the redox-active interlayer technology. This research was sponsored by the DOE’s Office of Energy Efficiency and Renewable Energy, the Vehicle Technology Battery Materials Research Program, and the National Research Foundation of Korea.