The advancement of electric vehicle (EV) battery technology is crucial to electrification’s success. Lithium-ion, still the most widely used battery chemistry, has come a long way in the last 15 years. Whereas the average EV battery had a volumetric density of around 55 watt-hours per litre (Wh/L) in 2008, many new models produced today are capable of exceeding 300Wh/L.
At the same time, traditional batteries are showing their limitations. Charging speeds are often limited by the rate at which lithium can diffuse in the anode, and the use of highly flammable organic separators presents a safety risk. Battery longevity also remains an issue, with most models having a useful life of around 600 to 700 cycles before needing to be replaced.
Solid-state batteries—long in development—promise to resolve these problems while also delivering next-generation improvements on energy density and range. A number of hurdles have impeded their realisation, including manufacturing complexity and material compatibility. Such issues led zero-emission nonprofit The Faraday Institution to conclude that solid-state technology may only be viable for commercial use from the 2030s onwards.
Battery technology firm Quantumscape is one of the leading firms developing solid-state. The ‘unicorn’ start-up—meaning a valuation in excess of US$1bn—has attracted more than US$2bn of investment to date, and Volkswagen holds a 17% stake. Quantumscape believes its proprietary technologies could deliver a generational leap forward over incumbent battery solutions and even beat pessimistic timelines for the commercial deployment of solid-state. At present, it aims to see its products in commercially-available EVs before the end of the decade.
Range, speed and weight
“When Quantumscape was founded, the whole concept was to try to create a better battery,” states Asim Hussain, Chief Marketing Officer. “Whatever technology you’re using, that means achieving more power from the same amount of space and weight.” He acknowledges that solid-state is a “challenging technology” but emphasises that the solution lies in finding the right approach and then building upon it.
For Quantumscape, the answer was to find a solid material that could act as a separator for the battery’s bi-layer cathode stack, allowing the lithium to plate without the need for a traditional thermoplastic material. Instead, the company uses a proprietary ceramic. This enables a “lithium-metal anode-free” architecture where the standard carbon or silicon anodes are switched out with a lithium-metal anode that boasts significantly higher energy density. It is “anode-free” in the sense that the battery is manufactured without one in its initial discharged state. The anode forms in situ when it is charged for the first time.
“Suddenly, you have this energy density advantage that enables range while also having power density that allows you to charge and discharge really quickly,” Hussain tells Automotive World. Unlike a traditional anode, the solid electrolyte used by Quantumscape has very high ionic conductivity. By switching the material, a bottleneck is removed around power density—the company has demonstrated that its test units can deliver a 10-80% fast charge in less than 15 minutes. It believes this solution is ideal for reaching the company’s lofty energy density targets.
These benefits can be applied to both nickel-manganese-cobalt (NMC) and lithium-iron-phosphate (LFP) chemistries. However, NMC is arguably the most promising: its volumetric energy density could reach as high as 1,000 Wh/L compared to LFP’s 550 Wh/L. These are the targets Quantumscape is aiming to achieve in its commercial units.
No replacement needed
Energy and power density are crucial for addressing concerns around range and charging time, but customers weighing a potential EV purchase are also concerned about longevity and reliability. Typical battery warranties end at 700 to 800 cycles—roughly seven to eight years—or when the battery degrades to around 70% of its initial capacity. Depending on the manufacturer and battery size, an out-of-warranty unit can cost between US$6,500 and US$20,000 to replace.
Given the technology’s relative novelty, replacement costs have yet to become a common complaint among current owners; most EVs are still using their original batteries. However, concerns are manifesting in the used market: a 2023 report by the Green Finance Institute reveals that 62% of UK drivers cited battery lifespan as the single biggest impediment to purchasing a used EV.
While lowering the cost of battery production is important, Chris Dekmezian, Principal Product Lead at Quantumscape, believes it may be better to extend the lifespan of the original battery. As part of Volkswagen’s ongoing collaboration with Quantumscape, it trialled several of the latter’s non-commercial “A-sample” test units. After 1,000 test cycles—or around 500,000km—the automaker found that “no significant degradation” of the battery had taken place. “We were able to keep it above a 95% state of health, which is pretty crazy,” claims Dekmezian. “It’s among the best that I’ve seen to date for any battery, regardless of who produced it.”
However, he is quick to highlight that the testing procedures may not necessarily reflect real-world usage with pinpoint accuracy. The testing involved a three-hour charge and two-hour steady discharge—a rate both more consistent and less intensive than in most real-world driving scenarios. The goal is to test more intensive conditions in the near future. “We’re not quite at our target of five amp hours yet, but we’re fast approaching it.”
Ramping up to production
Quantumscape’s next step with Volkswagen will be to provide “B-sample” batteries intended for use in test vehicles. “If the B-sample models meet all of Volkswagen’s criteria, then we can lock in the module and pack designs,” Hussain states. “We can then look at creating an infrastructure for putting them in commercially available EVs,” says Hussain.
We’re not quite at our target of five amp hours yet, but we’re fast approaching it
There has already been some progress in this area. On 11 July 2024, it was announced that Quantumscape will enter a joint agreement with PowerCo—a battery manufacturer founded by Volkswagen—to industrialise its solid-state technology. Pending satisfactory technical progress and royalty payments on the part of PowerCo, the battery maker will be granted the license to manufacture up to 40GWh of capacity per year, with the option to expand to 80GWh. According to PowerCo Chief Executive Frank Blome: “Quantumscape’s technology is poised to enter a pivotal stage where PowerCo’s specialised expertise, resources, and global factories can help facilitate the transition to industrial-scale production.”
Given that much of the foundational research and development is already complete, commercialisation is becoming a priority for Quantumscape. “That’s what we’re really excited about in the next couple of years; it’ll allow us to bring the technology to market in the second half of this decade and then create scale,” says Hussain. At the time of writing, it is unclear whether Volkswagen’s 1 August 2024 commitment to slashing capex to “well below €170bn” between 2025 and 2029 will affect this timeline.
In any case, Hussain is not deterred by a challenge. “It’s been a process to make it this far. It has been really hard, and we always knew it would be. If it was easy, these batteries would already be in production everywhere.”
