September 11, 2024 • 4 min read
Part 2
Focusing on the ‘negatives’: addressing the environmental impact of anodes
Anodes play a crucial role in batteries, serving as one of the two electrodes. However, they are typically based on oil derived graphite. Can alternatives, such as silicon or bio-graphite, be engineered as viable lower carbon alternatives?
Graphite is the most common material in anodes. It can intercalate lithium ions during charging and release them during discharging, which allows for efficient energy storage and release. It’s typically coated on thin copper foil to create the anode electrode.
With the growing need for anodes to meet battery demand, how can the battery materials industry produce them more sustainably?
Assessing the carbon impact of anode materials
Today, most graphite used for anode production is synthetic. While this avoids the need for mining raw materials, the process emits an estimated three times as much CO2 as mining and refining natural graphite – with some estimates placing it far higher.
“Producing synthetic graphite requires high-quality petroleum or pitch coke, which are both derived from traditional fuels,” says Dave OudeNijeweme, Senior Director, Battery Materials. “Materials are heated at temperatures of over 2,600°C for weeks using electricity. It’s a highly energy-intensive process.”
The case for silicon anodes
Silicon is attracting increasing attention as an alternative material for anodes. A key advantage is silicon’s enhanced energy density.
“It’s possible to store a larger amount of lithium ions in silicon compared with graphite,” says OudeNijeweme. “Crucially, there is the supply available. When supplies of other raw materials start to become scarce, silicon is second only to oxygen in terms of abundance in Earth’s crust.”
Silicon anodes can be produced through various methods and from different feedstocks, resulting in significant variation in their characteristics. “Recently, the silane production route has been under the spotlight due to the complexity of managing the flammability and toxicity of this material. This could restrict where it can be produced, and at what quantities,” says OudeNijeweme.
Considering this environmental footprint, Minviro recently assessed several scenarios for silicon anodes. Even in the potential worst case scenarios for production, the silicon-based anodes had an impact of 6.5kg CO2e per kWh, while the best-case scenario impact could be as low as 1.8kg of CO2e per kWh.
Despite this advancement, the silicon anode is unlikely to ever become carbon negative.
“Graphite and silicon are not being recycled in a commercially viable way,” adds OudeNijeweme. “That means that if you don't recycle it, or at least reuse it in a lower grade format, you need to keep making it. And that means it's not as sustainable.”
However, there is another potential anode material that is abundant globally.
Bio-graphite: anodes made from trees
Rather than mining graphite or producing it synthetically from fossil fuels, the solution could already be growing naturally.
There are many other bio-feedstocks available that could potentially be used for anode production – from coconut shells to sawdust. But scale and consistency are important. A New Zealand-based start-up uses wood chips, another widely available product, to produce graphite materials very similar to those used in lithium-ion batteries.
The graphitization process can occur under much lower temperatures than incumbent processes, further reducing its environmental footprint. “Scaling up such processes to produce drop-in replacements for graphite-based anode materials would be a game changer,” says OudeNijeweme.
A Swedish and Finnish company is demonstrating how important expertise and by-products from different industries are for the energy transition. The company is one of the largest owners of commercial forests in the world and was previously focused on providing materials for industries such as paper. Using the byproduct lignin to produce hard carbon anode materials – which are the anode materials of choice for sodium-ion batteries – would provide a key steppingstone to a sustainable battery.
“This company is a big player in a totally different field that understands trees extremely well,” says OudeNijeweme. “They take a byproduct and upgrade it to a valuable material, and with its scale and size makes this very interesting.”
Finally, there are some novel processes being developed that produce carbon-based anode materials from captured CO2. “This demonstrates the possibilities to make significant improvements in the environmental footprint of battery anodes, especially the active materials, to a point where they become carbon negative,” says OudeNijeweme.
“We’re dedicating significant resources to creating scalable solutions to minimize the carbon footprint of each battery component, from the anodes and cathodes to electrolytes. This is an enormous task that no-one can do on their own, but strategic partnerships make it possible.”
The importance of creating partnerships to deliver the energy transition
OudeNijeweme emphasizes the value of collaboration in the battery supply chain.
“We’re seeking partners that can contribute to the energy transition,” says OudeNijeweme. “These partners can be customers, suppliers, or technology developers. We can take something from a low technology readiness level and make that into something that's commercially viable and can be scaled and deployed.
“A recent example is our announcement with NanoOne, and we’re open to partnering with other emerging industry players with new anode material processes or recycling technologies.”
For the battery minerals industry to meet its potential to contribute to net zero, industry participants will need to work together to foster greater levels of trust and collaboration between key stakeholders.
“In the journey to a net zero battery, there are many different parties,” adds Darryn Quayle, Vice President – Resources. “Handing over from one party to the other, there’s an interface and a gap that you can fall through. What we provide is that single point of contact, that golden thread throughout the whole journey, from the first-of-a-kind technology through to the execution of a commercial plant.
“It takes the right partner to take a concept through to a functioning, multibillion-dollar facility,” continues Quayle. “We have the capability to move from complex chemistries at a laboratory scale, right through to large volumes, while assisting in the qualification processes that a product needs to advance in this industry.”
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