Under pressure from the automobile industry, battery manufacturers are not only working on how to increase the energy density of their products, but on how to make them greener too
CHEMISTRY LESSONS
Battery manufacturers are changing the chemistry of their products to find new combinations which are cheaper or easier to procure, while also increasing performance
COBALT BLUES
Being cobalt-free or using a lot less cobalt in batteries could become a commercial advantage given the hazards of mining the substance and its history of limited supply with associated price volatility
KEY QUOTE
The tantalising potential of solid-state batteries, should the technical barriers be overcome, has secured the attention of the automobile industry
The production of a single EV battery requires up to 20 different materials sourced from around the world. As a result, calculating the emissions and climate impact of the process is challenging, says Transport & Environment, a European campaign group. The chemistries of each battery influence the type and volume of emissions and establishing these is further complicated by the way the battery cells are assembled. Even so, if the cost and performance of batteries are vital to the uptake of EVs, so too should be responsible production and control of their lifecycle green credentials, says David Reichmuth at the Union of Concerned Scientists (UCS), an American NGO. But in what is a notoriously cut-throat and complex industry, car manufacturers typically do not disclose how much energy or what sort of electricity they use in sourcing and making batteries. Workplace standards and environmental problems also vary globally. An EV is heavier than an equivalent internal combustion engine (ICE) vehicle, primarily because of the battery, meaning more material is used in EV production, resulting in more emissions. That emissions debt is paid off in fossil fuel savings during the first six months to two years of an EV’s use in the United States, which can be from 15 to 20 years, says Reichmuth. To that saving, however, emissions from grid generation to recharge the car battery must be added, although as the share of renewables increases on the network, the green credentials of EVs will improve further. Once an ICE vehicle is built, its efficiency in terms of energy used in its production is largely set, which is not the case for EVs. “Batteries are making substantial improvements each year to simultaneously reduce their specific energy, material use, and cost,” says Nic Lutsey at the International Council on Clean Transportation (ICCT) in San Francisco, which provides technical and scientific analysis to environmental regulators.
CHEMICAL OPTIONS
For EVs, lithium-ion (Li-ion) batteries, “Have become winners because they are cheap and perform well,” states DNV, a European advisory and risk management business in the maritime and energy sectors. Their production involves many chemistries—cathode and electrolyte composition—with the different combinations leading to different performance characteristics and trade-offs. Lutsey says improvements in cathode, anode, pack-level design, and manufacturing for the various chemistries are being made despite the immaturity of the supply chain. Battery companies are continually looking for new designs to improve both the performance and sustainability of their products. Better performance will not only increase EV uptake; the longer the life and the range of an EV battery, the fewer will be required, reducing their impact on the environment. StoreDot, an Israeli company backed by the likes of BP, Daimler and Samsung, announced in January 2021 it had manufactured samples of an “extreme fast-charging” battery for EVs together with partner Eve Energy in China. StoreDot claims its battery for a two-wheeled vehicle can be fully charged in five minutes. The cells use nano-scale metalloids and proprietary compounds. “Ultimately, this [StoreDot’s product] could mean fewer batteries are needed and thus less environmental damage from extracting the materials and manufacturing them,” say Rachel Lee and Solomon Brown, experts in electric vehicles and chemical engineering at Sheffield University in the UK, on The Conversation website. A battery that uses a lithium iron phosphate (LFP) chemistry is set to be used in Tesla’s upcoming $25,000 entry-level EV. The technology is more reliable but the trade-off is that it weighs more and has lower energy density compared with more expensive batteries, although it does have a long cycle life, says Madeline Tyson with RMI, a think tank in Colorado formerly known as the Rocky Mountain Institute. Other established chemistries—lithium-nickel manganese cobalt oxide (NMC) and lithium-nickel cobalt aluminium (NCA)—are also being rapidly evolved to increase energy density at an affordable price, adds Tyson. Weight saving is key. Li-ion batteries can be encased in epoxy, rather than steel, reducing the amount of the metal used—and its associated emissions—by 40%, says RMI’s Charlie Bloch. Tesla promises to produce cells surrounded by epoxy with coolant distributed below, improving cooling and reducing weight while giving a 14% increase in the driving range of an EV. Cell-vehicle integration will lower battery pack costs by 7% per kilowatt-hour (kWh), says Tesla.
THE COBALT PROBLEM
Attention is being given to reducing cobalt in EV batteries and to making the mining of the metal more sustainable. In late January 2021, Chinese firm SVOLT Energy Technology announced that its new cobalt-free Li-ion batteries are available. The SVOLT uses 75% nickel and 25% manganese in the cathode. Meantime, General Motors, a giant American automaker, is developing a battery using 70% less cobalt than conventional Li-ion batteries, reliant instead on an energy-dense Li-nickel manganese cobalt and aluminium chemistry. It has an expected capacity of up to 200 kWh, roughly double the storage of Tesla’s most powerful pack. Being cobalt-free or using a lot less cobalt could become a commercial advantage. Over half of the mined and processed cobalt globally is now used in batteries. But it has a high and volatile price: availability is limited or inflexible making it susceptible to a tightening of the supply chain. Cobalt is mostly sourced from the Democratic Republic of Congo where many of the small artisanal mines are notorious for local pollution and hazardous conditions for miners, including children. Lithium mining also needs to be made more sustainable. German carmaker BMW appears to be on the job, with a study commissioned in December 2020 to analyse water consumption. The mining uses approximately two million litres of water per tonne of lithium, with the risk of environmental damage near the mine. Other issues with some of the niche metals used in EV batteries include the processing of sulphide ore, such as lithium sulphide, which is energy-intensive and emits sulphur oxides (SOx), a contributor to acid rain.
SOLID-STATE BATTERIES
A potential option for greening EVs is the use of solid-state batteries. In theory, they can help extend range, reduce charge time, and lengthen battery cell life even in cold climates. Proponents say that solid-state batteries are safer because they contain no flammable material. Li-ion batteries in EVs have been known to catch fire, and are less efficient in low temperatures. The use of “solid-state” ceramic or polymers over a liquid electrolyte avoids the problem. Solid-state batteries can theoretically hold twice the energy of a lithium-ion counterpart and operate in sub-zero temperatures, which is a challenge for a Li-ion battery. But they have yet to be produced commercially. “Solid-state batteries are currently on a low technology readiness level and basic research is still ongoing,” says Hans Anton Tvete and Davion Hill in DNV’s Technology Outlook 2030 series. They point to concerns about high production cost and scalability. Nonetheless, Japan’s Toyota plans to unveil a prototype solid-state battery for EV use with a single-charge range of around 500 kilometres and the ability to fully recharge in ten minutes. A high-profile unveiling is expected at this summer’s Tokyo Olympics, which looks to be a scaled-back event. RMI’s Tyson notes that solid-state batteries with lithium can achieve twice the energy density of Li-ion batteries today. A lithium metal anode is more energy-dense than conventional anodes. “Higher energy density can help enable new use cases, especially mobility-related, which can make more things sustainable climate-wise,” she says. The tantalising potential of solid-state batteries, should the technical barriers be overcome, has secured the attention of the automobile industry. Germany’s Volkswagen has a strategic partnership with a California start-up, QuantumScape, backed by technology entrepreneur Bill Gates, which has developed batteries that use a ceramic electrolyte separator between a cathode and anode instead of a liquid electrolyte. The materials used are nickel, manganese, cobalt oxide and lithium, which Tyson notes is the composition of a typical NMC Li-ion battery. A ceramic electrolyte, however, helps prevent dendritic growth, a critical safety problem, and which occurs more easily in liquid electrolytes, notes Bloch. Whether liquid or solid-state, batteries that store greater amounts of energy without increasing their volume and are made using materials and processes that meet the highest environmental standards are within technical and economic reach. DNV projects that by 2032, 50% of all new passenger vehicle sales will be electric. “With a market breakthrough of solid-state batteries, it’s likely that these numbers will grow even further,” it says.
TEXT Ros Davidson