Future of EV Batteries: More Electric Range, Faster Charging
Electric car batteries have a lot of conflicting demands. They need to store a lot of energy; deliver high performance; have a long service life; and be safe in an accident. All at the lowest possible cost. Until now, lithium-ion batteries have been the dominant technology in electric vehicles (EVs) because they cover all those bases quite well. But lithium-ion batteries have their limitations, too, and battery engineers are constantly working on ways to improve batteries to deliver better performance and lower cost from lithium-ion cells. At the same time, there are already a number of potential successors to lithium-ion Electric Car batteries in development. Join us as we take a look at the ways lithium-ion batteries are evolving – and the next generation of EV power packs.
Optimizing Lithium Ion
In terms of energy density, pure lithium is the ideal material for the anode – one half of a battery’s chemical makeup. But lithium is also highly flammable, so for safety reasons, graphites are mixed into active anodes so they can absorb lithium ions. The combination of lithium and graphite helps increase batteries’ charging capacity, and keeps their price relatively low compared to pure lithium, which is expensive and energy-intensive to mine. Lithium and graphite also provide a relatively long service life for EV batteries: even after 3,000 charging cycles, batteries can still retain a residual capacity of 80 percent or even more. Data from the Battery Research Center at the University of Münster in Germany suggests that today’s electric car batteries could have a service life of over 600,000 miles.
Because lithium-ion Electric Vehicle batteries contain many components, each of them offers optimization potential. The anodes, which are currently graphite-intensive, could switch to silicon in the future. Silicon, which exhibits the second-highest storage capacity per weight after lithium, offers energy storage potential that is ten times higher than graphite. This could could help the next generation of lithium-ion batteries have a much higher capacity. Even better, unlike lithium silicon is the second most common element in the earth’s crust – much easier to access and less expensive than lithium. Porsche, which is just one manufacturer working on silicon anodes, says that in the future, their EV batteries could be charged from 5 to 80 percent in less than 15 minutes – significantly improving convenience for electric car drivers.
Silicon Anodes and Nickel Cathodes
The challenge with silicon is that it physically expands when lithium ions are absorbed during the chemical reaction that generates electricity. Indeed, when lithium is absorbed, pure silicon particles can expand to three times their original size, which can physically stress the material and the battery housing. This physical stress could damage the electrode surfaces and reduce the service life of the battery. Porsche’s engineers have started to mix other materials in with silicon, dialing back its proportion to 80 percent, which could help mitigate that stress.
Work is also under way to optimize the materials used for the cathode, the other half of an EV battery. For the cathode, the most important characteristic is the ability to hold a lot of charge, which is driven by the electrochemical potential of the material. Most electric car batteries currently use lithium, nickel, and cobalt-manganese-oxide in a ratio of 6:2:2 – with nickel and cobalt-manganese-oxide in equal proportion. In the future, nickel’s share of the mix could increase, reducing the use of cobalt-manganese-oxide. More nickel in an EV battery would offer higher charging capacities.
Lithium-ion batteries can also be improved by optimizing the separator, which is made up of very thin (10 to 20-micrometer) strips made of polyethylene or polypropylene. The separators add space and weight to the battery pack, but new technology should enable the production of much thinner versions. The thinner the separators are, the more layers or coils on electrodes that could fit into a battery cell. Ultimately, thinner separators would allow a same-sized battery to have much higher cell capacity and energy content.
Solid State EV Batteries – The Next Generation
An intensive amount of research is currently being lavished on solid-state batteries, which could represent the next major leap for electric car technology. Instead of using an electrolyte solution, solid state batteries use a solid material for the electrolyte; they also combine the electrolyte and separator into one piece. This means solid state batteries require significantly less installation space than a lithium-ion battery – or, alternatively, they can pack in a lot more range and capacity into the same sized space.
Researchers hope that, by eliminating electrolyte solutions, solid state batteries will have an energy density of up to 50 percent higher than lithium-ion batteries. The solid electrolyte is much less flammable, improving safety. Solid state batteries should also allow for significantly faster charging times.
Sensors and Cell Design
It’s not just battery chemistry where leaps and bounds are being made. Improved sensors will help more precisely monitor battery charge levels, allowing charging times to be further shortened by allowing faster charging in certain voltage ranges. The cooling systems for batteries could also be controlled more precisely, increasing charging speed but also helping batteries to last longer.
Innovative new packages will help make batteries more powerful and enable more range. Cell-to-pack technology would integrate the cells directly into the battery housing, instead of packing thousands of smaller cells in. Eliminating the small parts – and the walls and spaces between them – would enable an EV battery to pack more energy into the same amount of space.
What to Expect for the Future of EV Batteries
The combination of evolving lithium-ion technology, research into different chemistry, as well as innovations in sensors and packaging could help EVs go significantly further on a charge. Porsche says that the combination of new anode chemistry and dense packaging could unlock range of over 800 miles – a 30 to 50 percent increase over the longest-range EV batteries today. More importantly, those same innovations will unlock improved fast-charging capability that would one day mean charging to 80 percent of a vehicle’s range would only take as long as stopping for gas.
