With more and more people buying electric cars and storing energy at home, the global appetite for batteries is expected to grow sharply in the coming years. As Lehtonen sees it, “the demand is just mind-blowing”.
In 2015, a few hundred additional gigawatt hours (GWh) were required every year across the world’s battery stocks – but this will rocket to few thousand additional GWh required annually by 2030 as the world moves away from fossil fuels, according to management consultancy McKinsey. The problem is that the lithium ion batteries we rely on today largely depend on environmentally damaging industrial processes and mining. Plus, some of the materials for these batteries are toxic and difficult to recycle. Many are also sourced in countries with poor human rights records.
Making synthetic graphite, for example, involves heating carbon to temperatures of up to 3,000C (5,432F) for weeks at a time. The energy for this often comes from coal-fired power plants in China, according to consultancy Wood Mackenzie.
The search is on for sustainable battery materials that are more widely available. Some say we can find them in trees.
Generally, all batteries need a cathode and anode – the positive and negative electrodes, respectively, between which charged particles called ions flow. When a battery is charged, lithium or sodium ions, for example, transfer from the cathode to the anode, where they settle like cars in a multi-storey car park, explains Jill Pestana, a California-based battery scientist and engineer currently working as an independent consultant.
“The main property that you want in this parking structure of a material is that it can easily take in the lithium or sodium and let it leave, and it doesn’t crumble apart,” she explains.
When the battery is discharged in order to power something like an electric car, the ions move back to the cathode after releasing electrons – the electrons move through the wire in an electrical circuit, transferring energy to the vehicle.
Graphite, Pestana says, is a “spectacular” material because it works so well as a reliable anode that enables such reactions to take place. Alternatives including lignin-derived carbon structures have a fight on their hands to demonstrate that they are up to the job.
There are multiple firms exploring lignin’s potential in battery development, however, such as Bright Day Graphene in Sweden, which makes graphene – another form of carbon – from lignin.
Lehtonen extols the virtues of his firm’s carbon anode material, which Stora Enso has named Lignode. He won’t reveal exactly how the company turns lignin into a hard carbon structure, or what that structure is, exactly, except to say that the process involves heating the lignin – but to temperatures nowhere near as high as those required for synthetic graphite production.
One important feature of the resulting carbon structure is that it is “amorphous”, or irregular, says Lehtonen: “It actually allows a lot more mobility of the ions in and out.”
Stora Enso claims that this will help them make a lithium ion or sodium ion battery that can be charged in as little as eight minutes. Fast charging is a key goal for developers of electric vehicle batteries.