Lithium Sulfur Batteries Could Have Energy Densities Higher than Nickel and Cobalt Batteries at Prices Cheaper Lower Than LFP
The transition to electric mobility is well underway. Last year, about 10 million electric vehicles were sold around the world. The leader in terms of EV market share is Norway, where for the full year 2022, market shares were 79.3% for BEVs, and 8.5% for PHEVs, combining to 87.8%. Sweden and several others are also following on this path to high shares of EV penetration in new vehicles sales. In the UK, December 2022 saw record-breaking sales. 1 in 3 vehicles sold in December was a battery-electric vehicle. For the first time in the UK, BEV sales surpassed petrol vehicles sales in one month. In term of sales volumes, China, the world’s largest auto market led the way again with over 5 million EVs sold in 2022.
There are now more than 20 million vehicles on the road worldwide and the global electric vehicle fleet is growing much faster than previously thought. A report by the IEA says the Net Zero Emissions by 2050 Scenario sees an electric car fleet of over 300 million globally in 2030. Electric cars will be accounting for 60% of new car sales by then. 2030 is only 7 years away. If we are to add the 280 million vehicles in 7 years, we need a lot of batteries made using cheaper and more abundant materials that not only maintain the level of performance from the current generation of traction batteries, but also improve on it. This comes down to the battery chemistry and having a deep dive into which materials can get us there and solving the big problems that have limited progress so far. Energy security, localizing supply chains and reducing reliance on geopolitically and ethically sensitive materials will also be key considerations.
One of the ideal compositions of batteries that will give the lowest cost and some of the highest energy densities involves paring lithium metal anodes and lithium sulfur cathodes whilst being able to access the sulfur at low electrolyte ratios, reducing cell weight. Sulfur would be a key cathode material as it offers the lowest cost and highest energy viable cathode material on the periodic table, says Conamix. Conamix, based in Ithaca, New York, is a venture-backed battery materials company led by a team of work-hardened battery experts turning sulfur cathodes from the out of reach holy-grail of lithium-ion cathodes into a global product with the energy, power, and cycle life demanded by the EV revolution. Charlotte Hamilton is the CEO and co-founder of Conamix. Conamix has a portfolio of dozens of patent families.
The challenges with cobalt for high energy density NMC lithium-ion batteries, including the high cost of cobalt and ethical sourcing issues, are well known and have been documented in great deal before. Another key component is nickel, and Elon Musk stated a few years ago that we need more nickel! The commercialization of the world’s first sulfur-based lithium battery will reduce reliance on cobalt and nickel and at the same time, significantly reduce the cost of EV batteries by 30% because sulfur is abundant and cheaper. Global production of sulfur is already around 77 million tonnes a year and the US is the world’s second largest producer. Sulfur is also a byproduct of oil and gas production.
Conamix was founded in 2014 and has only recently emerged from stealth mode. Its work builds on innovations developed at Cornell, Stanford, University of Waterloo, Berkeley Lab, and other global research institutions. Conamix closed a Series B round of funding and also secured an $8.6 million contract from the federal Intelligence Advanced Research Projects Activity.
I spoke with Charlotte Hamilton (CH) recently on the progress so far on the journey to get lithium sulfur batteries into cars and on the roads.
RJK: What are the general challenges in the EV battery industry?
CH: The EV battery industry is facing a supply crunch and a first time ever recent increase in the cost of high energy EV batteries at the cell level due to supply pressure on cobalt and high purity nickel. As the world moves to more and more EVs the existing chemistries based on scarce materials for high range vehicle batteries, the supply and price pressure is only going to get worse without a change in the core chemistry for high range EV cells.
RJK; What are some of the main challenges of lithium sulfur?
CH: Lithium sulfur has historically faced a challenge of cycle life due to the nature of sulfur as a cathode material. On the cathode side of the battery the sulfur undergoes a conversion to store and release energy. That conversion creates polysulfide materials that if not contained by the structure and chemistry of the cathode will lead to lower and lower capacity with every cycle of the battery. The other specific challenge is making lithium sulfur cathodes work at high energy and power with a very low amount of liquid electrolyte in the system. Historically, the approaches to lithium sulfur have used an excess of electrolyte to fully access the energy of the sulfur. This excess of electrolyte translates to a very low energy density when you move to multi-layer cells and complete EV packs where you don’t have the space or the weight available to accommodate excess electrolyte.
RJK: How is Conamix working to solve those challenges?
CH: Conamix has been working in stealth mode for half a decade with good venture funding to directly address both of the key challenges with sulfur. We have pushed our cells to lower and lower electrolyte ratios year over year to discover and solve new failure modes for lithium sulfur. Every time we push the battery to a failure mode we can find a new material science solution. In a low electrolyte environment, which is necessary for a high energy density EV pack, we use a variety of multifunctional additives and precise structuring of the cathode material to accomplish a high energy density cell. We’re now able to achieve automotive energy density levels on the cathode side in a low electrolyte system and we’re currently working with multiple partners to pair our advanced cathode active material with the correct anode technology to make an ultra-low cost and high energy EV cell.
We’re particularly focused on making cobalt- and nickel-free systems to relieve some of the supply chain bottlenecks that are currently facing long range lithium-ion cells for the EV market. All of our materials are designed to be drop-in materials that can be slurry coated onto cathodes with existing manufacturing methods. Sulfur and the other materials we use on the cathode side are also widely abundant globally, and with additional technical integration with other materials we’ll enable a long range EV cell to be made with abundant low cost materials. We expect to be able to meet or exceed the gravimetric and volumetric energy density performance of existing cobalt based lithium-ion systems while coming in significantly lower cost than lower energy LFP-based batteries.
Conamix uses a stack of multifunctional materials to address the issues that had stalled lithium sulfur tech. The Scanning Electron Microscope (SEM) image at the top of the page illustrates some of these materials. Conamix incorporates “Meta particles” with gradient structures to balance the transport of ions and electrons to enable improved power capability, energy density. They also use “Life Bi-functional cathode additives” that simultaneously store lithium ions and conduct electrons, thereby replacing expensive and spaces wasting carbons along with a new “binding” molecule that spatially restricts the electrochemical reaction storing the energy and thereby extends the life of the novel electrolyte components that improve basic efficiency of the electrolyte, providing improved energy density.
So, when can we expect to see these lithium sulfur batteries in our vehicles? Well, there are a lot of steps to follow to get them fully compliant and certified, but Conamix is hoping to go through all the processes and have batteries ready for integration in vehicles commercially by around 2028, which is only 5 years away. That’s less time from now till then than most OEMs take to release an updated version of one of their vehicle models. So, it is not a lifetime away before we may get some of this breakthrough battery tech in cars and on the road.
Images courtesy of Conamix