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As demand soars for lithium-ion batteries to power new technology, including electrical vehicles, smart phones and laptops, so does demand for battery-grade minerals, like graphite, to make them.
However, the environmental and financial costs associated with current methods of purifying graphite are high.
Graphite is a key component of a range of everyday things from batteries, brakes and refractory bricks, to lubricants, fire retardants, inks and electronics. It is used extensively across the steel, automotive, aircraft, electronics, energy and nuclear industries.
Almost 800,000 tonnes of tiny graphite crystalline flakes, ranging from one to 300 microns, are sold annually.
It's expected that global demand for battery-grade graphite will increase by 300 to 400 per cent by 2020.
The automotive industry in particular will contribute significantly to this surge in demand with the rapid move toward electrical vehicles across Europe and Asia.
This means that Australian exploration company, Kibaran Resources, will not only have to find better ways to locate and access more graphite, but also better ways to process it.
Getting ahead in the battery market
"As the market develops for electrical vehicles and energy storage, the awareness of ethical and environmentally-friendly raw materials is becoming more prominent. People want a more environmentally-friendly source," Kibaran managing director, Andrew Spinks, says.
Kibaran, a company that is focussed on the mineral-rich landscapes of Tanzania in east Africa, wanted to create a more cost-effective, "greener" battery-grade graphite to meet the needs of the growing European market.
"We started working with CSIRO initially to understand the graphite occurrence with respect to the mineralogy and metamorphism. We looked at how we could recover the graphite more efficiently," Mr Spinks says.
The company then engaged CSIRO and GR Engineering Services to create a better shaping and purification process for this vital mineral.
Meeting the needs of battery manufacturers
Processing battery-grade graphite involves two-stages: mechanically shaping natural graphite into small balls – "spheronising" it – then purifying it.
While all but two to three per cent of minerals can be removed from graphite by standard physical methods, battery‑grade graphite needs to be at least 99.95 per cent pure to create long‑lasting, better‑performing batteries.
There are several ways to purify graphite, including chemical and thermal methods. All battery-grade graphite is currently processed in China using hydrofluoric acid and other noxious chemicals.
"One of the reasons that the hydrofluoric acid method is so popular is because hydrofluoric acid will eat just about anything, but doesn't eat graphite," CSIRO director for minerals processing research, Chris Vernon, says.
"It sounds like a very logical way of treating the graphite, however, hydrofluoric acid has to be neutralised and then recycled or dumped, so it doesn't make much sense environmentally."
Although there are alternate ways of processing graphite, they are not currently competitive. And, with each battery manufacturer having slightly different specifications for graphite, CSIRO and Kibaran had a lot of work to do to optimise the purification process and meet the various specifications.
Purifying graphite to battery grade
The biggest challenge for producing battery-grade graphite is the purification process. It's particularly difficult to remove the resistant minerals. Silica, for example, has several forms and each form must be identified before it can be removed from graphite.
"We were able to use our knowledge that we’ve built up over decades in, for example, alumina processing to understand how the silica species were going to behave while we tried to treat the graphite," Dr Vernon says.
"It's that kind of deep know-how around mineral chemistry, phase equilibria and solution reactions that was brought to bear to make this a success."
Despite CSIRO's world-class capability and know-how in minerals identification and chemistry, it wasn't always easy to find the right solution.
"Even with in-depth knowledge of the major impurity minerals, there's still a considerable amount of experimentation before arriving at the optimum solution," Dr Vernon says.
"The real enemies are the very low levels of highly refractory, unreactive minerals that you're trying to coax out of the graphite.
"Instead of hitting them with a big hammer [hydrofluoric acid], we are basically tickling them out with a feather."
CSIRO scientists used various characterisation tools to identify minerals and understand the different reaction chemistries possible.
They then manipulated the chemistry with dilute solutions at modest process temperatures.
"What we delivered for Kibaran was a greener process that's relatively cheap to operate, and that uses minimal quantities of plentiful and low-impact reagents," Dr Vernon says.
"We achieved greater than 99.95 per cent purity in the graphite – in a process time of only a few hours – by understanding how impurity minerals are going to react."
Process innovation for a range of deposits and minerals
While this exciting new process was bespoke to Kibaran's mineral chemistry needs, the general principles behind it can be readily adapted to suit other companies – particularly those facing similar issues around producing battery‑grade materials.
"The battery industry is going to grow and grow," Dr Vernon says.
"There's a strong focus on lithium, that's for sure. But, we also need all of the other chemicals that act like "vitamins" in the lithium batteries, such as high‑purity nickel and cobalt.
"There are also other battery chemistries, requiring high-purity vanadium, manganese and other metals.
"There are quite a lot of approaches from industry at the moment on understanding how to purify their materials to those levels without spending a fortune to do it. A lot of the lessons we’ve learned out of the project with Kibaran are immediately transferable to those other industries."
Currently, Kibaran is working with several new graphite sources and producers to meet market needs. It has also applied for patents for the new shaping and purification processes that the company recently tested in its new pilot plant in Germany.
"We are very much at the back end of finalising and finishing that piloting work, and we look forward to seeing the results, probably in the next month or two," Mr Spinks says.