California, known for leading the United States in climate regulations, will ban the sale of new gasoline powered cars and light trucks by the year 2035. Most new car sales are expected to be battery powered. Current EV's are slow to charge and have other drawbacks. The amount of time it takes to charge an EV depends on the charging equipment and the size of the battery.
Sarah Tolbert is a battery expert at the University of California, Los Angeles. Yi Cui is a scientist at the university. A revolution in battery design is predicted by him. He says the need for fast charging will give opportunities for new battery chemistries. He and others have come up with promising candidates because of the use of new materials.
The anode of most EV batteries is made ofGraphite. It is cheap, abundant and able to store enough batteries to give cars a range of 500 kilometers. The applied voltage causes the electrons in the graphite to go into the other part of the battery. The electrons are routed through the motor to convert some of their energy into motion when the car is driving.
It's hard to charge the anodes quickly. The United States uses either a standard household voltage of 120 or a higher one of 220. It can take 10 hours or more to charge an EV with a 500 kilometer range. The electric vehicle can be charged to 80% capacity within 45 minutes. The dendrites that can short out the battery and cause it to catch fire are caused by the nearly 500-volt charger. If that doesn't happen, high-voltage charging can cause irreversible structural changes in the battery that shortens its lifetime.
Changing the rates at which batteries are discharged could be a partial solution. Cui and his colleagues reported in a Nature paper that doubling the discharge rate for the first 2 minutes can extend the life of a battery by 29%.
It is possible to change the material completely. Fifteen years ago, Cui and others showed a way to increase how much charge a battery can hold. Each Silicon atom is able to bind more than one carbon atom. The anode material can swell up to four times in size when pushed into a Silicon matrix. The battery is killed when it is repeatedly charged and discharged.
Modifications to the structure of the Silicon can allow it to swell and shrink without fracturing, which can extend the battery life. The company that was spun out of Cui has developed a battery that is nearly double the size of the cells used in current electric vehicles. The new cells can charge to 80% of capacity in just 6 minutes. The company sells batteries for drones and is trying to scale up the technology for electric vehicles.
Other materials are being worked on. A group of people, including a colleague from UC Los Angeles, reported that anodes made from niobium would enable higher capacity and faster charging. Niobium oxide was processed into a spongelike form, made up of tendrils shot through with small particles. The material has a high surface area that allows it to hold a lot of lithium and the larger channels allow it to charge quickly. The structure of the niobium-oxide does not change when it is grabbed and released. As the battery goes through repeated charge/discharge cycles, it will be less damaged due to the fact that lithium ion nestles close to niobium atoms.
UC Los Angeles granted its technology to a startup. The company reported last month that it has made cells that can charge to 80% of capacity in 10 minutes. Thousands of similar-size cells are used in the current EV. During fast charging, Battery Streak's cells warm up by just 8C, which is less than half the temperature of the batteries that heat by 50C. Dan Alpern, Battery Streak's vice president of marketing, says that it should prolong the life of the cells more than 10-fold. The price of niobium is more than 30 times that ofGraphite. Amprius scales up its batteries for EV's.
Replacing the charge-carryinglithium ion with other materials can help. A novel battery design that relies on aluminum ion was reported in the August issue of Nature. The prototype has the same capacity as conventional batteries, but can be charged in minutes. The battery needs to operate near the boiling point of water in order to allow aluminum ion to move through the device. Sadoway and his team are trying to lower the temperature. The cost of materials for the batteries would be 85% less if they were successful.
Gil Tal is a transportation technology expert at UC Davis. He believes that large-scale EV adoption will cause the battery market to splinter, allowing users to choose their batteries based on whether they prioritize the lowest cost, the fastest charging, or the longest life. Tal believes that the market will be more diverse by the year 2035.
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