E-Mobility Engineering 014 l InoBat Auto dossier l In Conversation: Brandon Fisher l Battery monitoring focus l Supercapacitor applications insight l Green-G ecarry digest l Lithium-sulphur batteries insight l Cell-to-pack batteries focus

manufacture LiS batteries for e-mobility applications. Mark Gustowski, managing director of Enserv Australia, says, “We would be looking to use the technology to enter the growing market for EVs and electronic devices. We plan to make the first lithium-sulphur batteries in Australia using Australian lithium within about 5 years.” Kevlar nano ibres Researchers from the University of Michigan in the US have used a network of aramid nanofibres, recycled from Kevlar, to boost the cycle life of a LiS cell. “There are a number of reports claiming several hundred cycles for lithium-sulphur batteries, but it is achieved at the expense of other parameters – capacity, charging rate, resilience and safety,” says Nicholas Kotov, Professor of Chemical Sciences and Engineering at the university, who led the research. “The challenge nowadays is to make a battery that increases the cycling rate from the former 10 cycles to hundreds of cycles and satisfies multiple other requirements including cost.” The team had previously used networks of aramid nanofibres infused with an electrolyte gel in a lithium-ion cell to stop the dendrites that can grow from one electrode to the other and cause a short-circuit. The toughness of aramid fibres stops the dendrites. But LiS batteries have another problem: that polysulphide shuttle effect. The membrane in the cell needs to allow lithium ions to flow from the lithium to the sulphur and back, but also has to block the polysulphides. This ability is called ion selectivity. The lithium ions and lithium polysulphides are similar in size, so it wasn’t enough to block the polysulphides by making small channels. Mimicking pores in biological membranes, the researchers added an electrical charge to the pores in the membrane. that the chemical phase has remained the same.” The cathode was tested for over a year and remains stable after more than 4000 charge-discharge cycles. Dr Kalra says, “While we are still working to understand the exact mechanism behind the creation of this stable monoclinic sulphur at room temperature, this remains an exciting discovery and one that could open a number of doors for developing more sustainable and affordable battery technology.” Having a stable sulphur cathode that works with a carbonate electrolyte also opens up the use of materials such as sodium for the anode. “Getting away from a dependence on lithium and other materials that are expensive and difficult to extract from the ground is a vital step for developing batteries and expanding our ability to use renewable energy sources,” says Dr Kalra. “Developing a viable LiS battery opens a number of pathways to replacing these materials.” Meanwhile, researchers in Australia have developed a nanoporous interlayer that sits between the two electrodes to reduce the shuttling of the polysulphides. These Porous Aromatic Frameworks have uniform 13 Å pores and internal surface areas that can be readily chemically functionalised. Appropriate sulphonation levels within these pores can deliver high lithium-ion transport rates, giving high capacity retention above 1000 mAh/g after 500 cycles at practical charge rates. “A lithium battery interlayer sits in the middle of the battery and keeps the electrodes apart, and helps lithium get from one side of the battery to the other faster,” says Professor Matthew Hill at Monash University’s Faculty of Engineering, who led the research. “The new interlayer overcomes the slower charge and discharge rates of previous generation lithium-sulphur batteries. Fellow researcher Ehsan Ghasemiestabanati says, “The interlayer stops polysulphides from moving across the battery; polysulphides interfere with the anode and shorten the battery life. It means the battery can be charged and discharged up to 2000 times without failing.” The team had previously used sugar to stabilise the sulphur in the cathode, preventing it from moving. A test cell built by them has a life of at least 1000 cycles, while still holding more capacity than equivalent lithium-ion batteries. The LiS work at Monash has been supported by CleanFuture Energy, an Australian subsidiary of the Enserv Group of Thailand, to develop and Prototype LiS cells are currently with customers for testing, with plans for volume production in 2024 (Courtesy of Lyten) 60 Summer 2022 | E-Mobility Engineering