Humankind’s constantly growing energy demands are being met by ever more sources, including ones that come with risks. With so much power being produced, safely storing it has become a pressing issue. For many years, Lu Yi-chun, a professor in CUHK’s Department of Mechanical and Automation Engineering, has toiled away on a solution that she hopes will enhance the safety of battery storage but still be cost-effective. Her work on polysulfide flow batteries has long garnered acclaim, and now she is taking her mission to the next level with a funding boost from the RAISe+ project.
Standing firm on cost and safety
The two most widely available battery options on the market these days both come with significant problems. The lithium-ion battery is commonly found in electrical appliances and electric vehicles (EVs) and is relatively cheap; but having studied them as a postgraduate student at the Massachusetts Institute of Technology, Professor Lu knows just how easily they can overheat or even explode.
“After I graduated, I came to CUHK and I wanted to work on something that can support larger-scale energy storage, and do so with intrinsic safety: I want technology to be completely safe,” she says.
Since the 1980s, an alternative known as flow batteries has emerged, where chemical energy is provided by pairing electrolyte-rich solutions through a membrane. Although such batteries are certainly safer, most of the options available currently use vanadium, a limited and relatively expensive element, making mass production difficult.
Professor Lu hit on a solution that was much more affordable: sulfur. “Using sulfur in a flow battery system will simultaneously lower costs and achieve intrinsic safety.”
Using a specifically designed charge-reinforced ion-selective (CRIS) membrane – developed by her and her team, and now a patented technology – which stops the solutions that make up the battery from mixing with each other, the team have since perfected a battery that not only lasts longer but also allows for more stable chemical reactions; given that the raw materials of the battery are water fluids, there is little chance of the final product overheating or catching fire.
A successful showcase
Professor Lu knows she has a dependable product that combines the best of both worlds. In December 2020, she established the startup Luquos Energy with members of her research team in a bid to present the invention to the commercial sector. From a prototype that barely measured 5 cm in length, they have since developed batteries capable of charging electric vehicles. In July 2024, they cooperated with major Hong Kong energy provider Towngas to set up an electric vehicle charging station.
The professor talks about how the supplier readily accepted the plausibility of using polysulfide flow batteries to power such a facility: “That’s the nice thing about our technology – it’s intrinsically safe, made of water, so you do not even need to convince them.”
Situated in a Towngas charging station in Shenzhen’s Bao’an district, the LEAPLUG battery system consists of a flow battery and an energy conversion system, both of which are in a small container at the back of the station. As Professor Lu explains, “the battery essentially stores electricity during the night time” when electricity costs are lower in the city, “and then sells it back to the grid in the daytime” through charging points; in doing so, the system saves almost 70% of electricity costs, increasing the commercial viability of the project.
For Professor Lu, this demonstration project has amply shown the untapped potential of her team’s flow batteries. “The system we have in Shenzhen is not a very big one but it’s big enough to show the viability of the technology, and the fact that it has operated for more than a year in a real application further verifies its viability.”
‘All technology is going to benefit’
With its safety and cost-effectiveness proven by the LEAPLUG project, Professor Lu is ready to take her team’s research to a wider stage. This type of battery will be particularly useful for utility companies that hope to integrate renewables into their supply. Likewise, water treatment companies and data centres that operate 24/7 will need a constant, reliable source of energy, as well as a way of storing it.
Luquos plans to establish a prototype that can be mass-produced within the next three years, and the new RAISe+ funding ensures the continuation of its research. “We do not have a production line yet, so we still need more R&D to go to pilot scale, to something that can be financially viable in a commercial setting.”
Professor Lu also believes that flow battery technology can be brought to a wider audience. She has just come back from Germany, where she witnessed for herself the widespread need for energy storage. “From big metropolitan cities like Hong Kong, all the way to much more remote areas in Europe, they all have their own solar roofs; they need a battery to store the energy.” The transition to clean energy is proceeding apace in many parts of the world, and once this type of flow battery is in widespread use, she says, “globally, all technology is going to benefit.”
This article is first published in the e-newsletter “CUHK in Focus”.
