Lithium–sulfur battery designed to improve recycling options

As the world transitions to renewable energies, the need for more sustainable energy storage solutions is becoming critical.

In a recent paper, PhD student Declan McNamara, Professor Matthew Hill and Professor Mainak Majumder of Monash Engineering, with Dr Makhdokht Shaibani of RMIT University, outline how applying a nanoporous polymer directly onto a lithium foil anode can create a battery design that uses less lithium, has more energy per unit volume, lasts longer and will potentially be half the price of lithium-ion batteries. 

A lithium–sulfur (Li–S) battery is an emerging energy storage technology that uses metallic lithium and sulfur to deliver more energy per gram than lithium-ion batteries. While Li–S batteries are efficient, the process of finding, extracting and transporting lithium can leave a significant environmental footprint, so using as little lithium as possible remains important.  

Li–S batteries also have their limitations. Typically they contain a lithium anode (negative electrode) and sulfur cathode (positive electrode) with a separating layer. When the battery charges and discharges, large amounts of lithium and sulfur are reacted with one another, placing the lithium metal under a lot of strain.  

McNamara said the thin polymer coating on lithium improved the number of times the battery could be cycled. 

“The polymer contains tiny holes less than a nanometre in size — one billionth of a metre — which allow lithium ions to move freely while blocking other chemicals that would attack the lithium. The coating also acts as a scaffold for lithium, and helps it charge and discharge repeatedly,” McNamara said.

“Metallic lithium is a bit of a double-edged sword. Lithium is packed full of energy, but in a bad battery, this energy is wasted on side reactions. On the other hand, if the energy is channelled correctly, it can make some incredible energy storage devices that are easier to make. This coating is a step towards highly efficient, easily manufactured Li–S batteries.”

The new design, which doesn’t require nickel or cobalt, is seen as a promising step towards more widespread adoption of Li–S batteries and other lithium metal-based energy storage systems.

“The market for electric vehicles, drones and electronic devices is on a steep growth pattern and this research is commercially ready for manufacturing to support that growth. Producing more economical and environmentally sensitive battery options in Australia would be a great use of this technology, and we look forward to working with commercial partners to develop and manufacture this technology,” Hill said.

Image caption: SEM image of nanoporous polymer coating on lithium.