Singapore researchers create 'safer' lithium-sulfur battery without compromising performance

Researchers at A*STAR's NanoBio Lab say they have created a semi-solid electrolyte that produces more stable lithium-sulfur batteries while maintaining robust performance, which then can be used in a wider range of electronic and energy storage devices.
Written by Eileen Yu, Senior Contributing Editor

Researchers at Singapore's NanoBio Lab (NBL) say they have found a way to manufacture more stable lithium-sulfur batteries without compromising their performance. This means the power source can potentially be used in a wider range of electronic and energy storage devices. 

Safety considerations had limited the use of lithium batteries in some environments due to their highly flammable liquid organic electrolytes that leaked easily, said the Singapore lab in a statement Monday. A lab incubator that focuses on the use of nanotechnology to create new materials, NBL is parked under government R&D agency, the Agency for Science, Technology and Research (A*STAR).

Liquid electrolytes also depended on thermally and mechanically unstable electrode separators, said NBL. It further noted that solid-state electrolytes could improve the safety of lithium batteries, but had poor electrode/electrolyte contact and limited ionic conductivity. This meant poorer performance and major conductivity bottlenecks, it said.

Its research team, comprising Ayman AbdelHamid, Jackie Y. Ying, and Cheong Jian Liang, created a semi-solid electrolyte that the lab said reduced the risk of leakage and was more stable than liquid alternatives. 

Ying, who heads the NBL research team, explained: "Hybrid quasi-solid electrolytes comprising both liquid and solid components have emerged as a practical compromise to obtain safer batteries while maintaining good performance. However, the high resistance of the solid component has, thus far, limited the performance of such batteries. 

"To overcome this, we have reengineered the microstructure of the solid component. Our solution eliminates electrolyte leakage, and is thermally and mechanically stable," she said. 

Its hybrid quasi-solid electrolyte comprises a liquid-infused porous membrane made of Li7La3Zr2O12 (LLZO) sheets, which were selected for their high ionic conductivity as well as good chemical and electrochemical stability, said NBL. It added that the electrolyte's non-rigid form also enables it to have good contact with electrodes and prevents it from cracking during handling and battery assembly.

The semi-solid electrolyte also is able to maintain its stability over a wide voltage range, allowing it to be used with different lithium battery electrode materials such as high-voltage cathodes.

The NBL researchers also developed a method of fabricating LLZO sheets to form a 3D-sheet framework for the electrolyte. Dubbed the "cupcake" method, the team said this one-step process involves dissolving metal precursors and sucrose in water, which then is placed in a pre-programmed furnace. The solution is heated to form a brown "cupcake" inside the furnace and heated at a high temperature to form the LLZO sheets.

According to NBL, lithium-sulfur batteries made with its hybrid quasi-solid electrolyte displayed high capacity, as well as fast charge and discharge capabilities. During tests, the electrolyte clocked rate capability of ~515 and ~340 mAh/g at 1 and 2C, respectively, at 1.5 mg/cm2 loading density. The lab said these results were amongst the highest known performance achieved by hybrid quasi-solid lithium-sulfur batteries.

The same research team last October revealed they had created a way to develop lithium-sulfur cathodes that was less complex and time-consuming than current methods. This, it said, could pave the way for the component to become a viable alternative for lithium-ion battery and for use in electronic vehicles and devices. Lithium-sulfur batteries are touted to store up to 10 times more energy than lithium-ion ones, the latter of which are used widely today to power communication devices.


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