In a new study, researchers at the US Department of Energy’s Argonne National Laboratory have improved sulfur-based battery research by creating a layer in the battery that increases energy storage capacity and virtually eliminates the traditional corrosion problem of sulfur batteries.
The researchers explain in their paper that a promising battery design combines a sulfur-containing cathode with a lithium metal anode. Among these components is an electrolyte, or a substance that allows ions to pass between the two ends of the battery.
Early lithium-sulfur (Li-S) batteries did not work well because sulfur species (polysulfides) dissolved in the electrolyte, causing it to corrode. This polysulfide effect has a negative effect on battery life and reduces the number of times the battery can be charged.
To avoid this polysulfide immersion, previous studies focused on placing a redox-inactive spacer between the cathode and anode. The term “non-reduced” means that the material does not experience reactions similar to those of the electrode.
However, this protective interlayer is heavy and dense, which reduces the energy storage capacity per unit mass of the battery. It also does not reduce transportation enough.
To solve this, the Argonne group developed a porous interlayer containing sulfur. Laboratory tests have shown that Li-S cells with this active, inactive interlayer have approximately three times the initial capacity. Even more impressive, cells equipped with an active interlayer maintained high capacity for more than 700 charge-discharge cycles.
“Previous experiments with cells with a redox-inactive layer only suppressed the transition, but in doing so they sacrificed energy for a given cell mass because the layer added weight,” said Guiliang Xu, a chemist and co-author of the study. “In contrast, our redox-active layer increases the energy storage capacity and weakens the shuttle effect.”
To better understand the redox layer, the team conducted experiments in the 17-BM beam of the Argonne Advanced Photon Source. The data collected by exposing the cells in this layer to X-rays allowed them to verify the benefits of the middle layer.
Data confirmed that a redox-active interlayer can reduce transport, reduce negative battery reactions, and increase battery capacity to hold more charge and last longer cycles. “These results show that the redox-active interlayer can have a great impact on Li-S battery development,” said APS radio researcher Wenqian Xu. “We are one step closer to seeing this technology in our everyday lives.”
In the future, the team wants to assess the growth potential of redox-active interlayer technology. “We want to try to make it much thinner and lighter,” Guiliang Xu said.
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