(Image: Pixabay)

University of Adelaide Professor Shizhang Qiao, Chair of Nanotechnology, and Director, Center for Materials in Energy and Catalysis, at the School of Chemical Engineering, led a team which examined the sulfur reduction reaction (SRR) which is the pivotal process governing the charge-discharge rate of Li||S batteries.

“We investigated various carbon-based transition metal electrocatalysts, including iron, cobalt, nickel, copper, and zinc during the SRR,” said Qiao, an ARC Australian Laureate Fellow. “Reaction rates increased with higher polysulfide concentrations, as polysulfide serves as the reactive intermediates during SRR.”

The team designed a nanocomposite electrocatalyst, comprising a carbon material and cobalt-zinc (CoZn) clusters.

“When the electrocatalyst CoZn is used in lithium-sulfur batteries, the resulting battery achieves an exceptional power-to-weight ratio of 26120 W kg/s,” said Qiao. “Our research shows a significant advancement, enabling lithium-sulfur batteries to achieve full charge/discharge in less than five minutes.”

High-power lithium-sulfur batteries are used in various devices such as mobile phones, laptops, and electric vehicles.

Current state-of-the-art lithium-sulfur batteries suffer from low charge-discharge rates, typically requiring several hours — typically from one to 10 hours — for a single full charge-discharge cycle.

The team’s study, which is published in the journal Nature Nanotechnology, is the first comprehensive approach to tackling the problem of slow charge/discharge rates in lithium-sulfur batteries and has significant impact for scientists designing electrocatalyst materials and experts examining the reaction mechanisms of lithium-sulfur batteries.

“Our breakthrough has the potential to revolutionize energy storage technologies and advance the development of high-performance battery systems for various applications,” said Qiao.

The high-power capabilities of these batteries make them well-suited for applications requiring rapid charging and discharging, offering enhanced performance and reliability for both consumer electronics and large-scale energy storage solutions in grid applications.

Professor Shizhang Qiao (Image: University of Adelaide)

Here is an exclusive Tech Briefs interview — edited for length and clarity — with Qiao and First Author Huan Li.

Tech Briefs: What was the biggest technical challenge you faced while developing this nanocomposite electrocatalyst?

Li/Qiao: There are many metal-based electrocatalysts so it is difficult to select the most suitable one for lithium-sulfur batteries. There is currently no design or selection principle for the nanocomposite catalyst. To achieve a rational design of the catalyst, we developed a kinetic trend for the sulfur reduction reaction (SRR) using typical Fe, Co, Ni, Cu, and Zn metal catalysts.

It was found that the SRR kinetic increases with polysulfide concentrations and the eg — t2g (a value that describes the catalysts). Using the trend, we designed and synthesized a CoZn/carbon nanocomposite electrocatalyst. Although the experimental synthetic process is simple, the biggest challenge was how to select a suitable catalyst, so we set up a kinetic trend to address this problem.

Tech Briefs: Can you explain in simple terms how everything works?

Li/Qiao: In lithium-sulfur batteries, there are lithium metal negative electrodes and sulfur positive electrodes with nanocomposite electrocatalysts inside. During the discharge process of the battery, sulfur undergoes a reduction process with polysulfide generation, and the lithium becomes lithium ions. The battery then releases its energy.

Therefore, our work is to design the nanocomposite catalysts inside the sulfur cathode, enhancing the kinetics of the sulfur reduction reactions. The aim is to improve the charge-discharge rate of lithium-sulfur batteries. The faster the kinetic for sulfur reduction, the faster the charge-discharge rates we can obtain.

Tech Briefs: How soon could we see energy storage revolutionized and batteries advanced?

Li/Qiao: Now, the most popular commercial batteries are Li-ion batteries, for example, in our laptops, mobile phones, and electric cars. Both scientific researchers and industrial workers are engaged in developing new battery systems to replace the Li-ion batteries. In this regard, the lithium-sulfur battery is a good candidate due to its low price and high energy.

However, it is hard for us to say how long it will take for the commercialization of lithium-sulfur batteries. This work is for future battery technologies. We estimate it will be 8-10 years before using it in practical applications. Although there are some companies that have produced large-size lithium-sulfur batteries, they have not brought these batteries to the market.

Tech Briefs: Going from that, what are your next steps? Any plans for further research/work/etc.?

Li/Qiao: We are going to (1) decrease the price and cost for lithium-sulfur batteries; (2) stabilize the lithium metal anode to eliminate safety concerns; (3) develop solid-state lithium-sulfur batteries that are free of liquid-type electrolytes.

Tech Briefs: If so, are there any updates you can share?

Li/Qiao: We are now working on the development of high-safety and low-cost lithium sulfur batteries. There should be some more exciting research in the future, and we will be happy to share that with the media.

Tech Briefs: Do you have any advice for engineers/researchers aiming to bring their ideas to fruition (broadly speaking)?

Li/Qiao: We hope we can do more research work with the potential for highly practical applications. We need to have discussions with a broad community, for example, scientific researchers and industrial partners, learning from each other’s knowledge and experience. The current background for research work is important. Taking battery research as an example, we need to know the current status of commercial Li-ion batteries, lead-acid batteries, etc. And then decide what we need in the following years. Our efforts should be in that direction.