Courtesy of UCR Today
Courtesy of UCR Today

UCR researchers have made strides in preparing a battery with 10 times more power than conventional batteries for commercialization. The research team has found a way to combat the lithium-sulfur (Li-S) battery’s short lifespan, one of the major obstacles to Li-S batteries becoming widely available.

Every battery contains two electrodes, the negative anode (the “minus side”) and the positive cathode (the “plus side”). A battery has separate pathways for electrons and ions to move, operating by either charging, where ions travel to the negative side, or discharging, where ions travel to the positive side. When the battery is discharged, the lithium ions react with the sulfur cathode and produce polysulfide.

A Li-S battery’s lifespan is so short because the polysulfide dissolves in the battery’s electrolyte — the liquid in the battery that conducts electricity and lies between the two electrodes — and travels to the anode permanently where it becomes insoluble. This phenomenon, called polysulfide shuttling, causes the battery’s capacity to decrease over time, lasting for only a few tens of charges.

The team, managed by engineering professors Mihri and Cengiz Ozkan, targeted this obstacle. They created microscopic glass-coated sulfur particles to trap the polysulfide product, rendering it unable to travel to and deposit itself on the anode. Graphene oxide was later added to hold the glass and sulfur together, since the glass showed a tendency to break during the cycle. This eliminates the problem of polysulfide shuttling, increasing the battery’s lifespan from 10 percent to 50 percent of a conventional battery’s.

According to Brennan Campbell, engineering graduate student who designed the experiments and first author of the research paper, many companies are looking to use Li-S batteries for electric vehicles and military machinery in the future.

“It is obvious to most of us that there are serious issues humanity will face in terms of energy supply, management, storage and consumption.” Campbell said about the importance of the project.

But despite the team’s successes, there are other issues standing in the way of these batteries’ commercialization. “Safety is a major concern in any battery system, especially for batteries to be used in electric vehicles,” said Mihri Ozkan. Campbell explained that a pure lithium anode is necessary to maximize the energy between lithium and sulfur, and this introduces a risk of the battery catching fire.

Regardless, the team remains optimistic about their commercial future. “Li-S batteries are the next wave of high performing batteries,” said Mihri Ozkan.