But pushing so many lithium atoms into a silicon matrix can cause the anode material to swell up to four times in size. Each silicon atom is able to bind four lithium ions, compared with only one for every six carbon atoms in graphite. Fifteen years ago, Cui and others showed anodes made from silicon can increase how much charge a battery can store and enable faster charging. In a 23 December 2021 Nature paper, Cui and his colleagues reported that doubling the discharge rate for the first 2 minutes a battery is in use essentially melts away any built-up lithium dendrites, which can extend a lithium-ion battery’s lifetime by 29% and make it stand up better to fast charging.Īnother emerging option is to change the anode material altogether. Even if that doesn’t happen, high-voltage charging can cause irreversible structural changes in the graphite that shorten the battery’s lifetime.Ī partial solution may come from simply changing the rates at which graphite-containing batteries are discharged. But these nearly 500-volt chargers can cause lithium ions in the graphite to pile up into metal needles called dendrites that can short out the battery and cause it to catch fire. Still higher voltage 元 chargers, such as Tesla Superchargers, can charge an EV to 80% capacity within 45 minutes. Even L2 chargers can require 10 hours or more to fully charge an EV with a typical 500-kilometer range. Most chargers in the United States today use either a standard household voltage of 120 volts (an L1 charger) or 240 volts (L2). As the car drives, the lithium lets go of the electrons and travels back to the cathode, while the electrons are routed through the motor, which converts some of their energy into motion, before returning to the cathode.īut graphite anodes are difficult to charge quickly. During charging, the applied voltage pushes electrons into the graphite, attracting lithium ions from the other electrode, the cathode. Graphite has dominated the market because it’s cheap, abundant, and able to store enough lithium ions to give cars a range of about 500 kilometers. Most EVs today use lithium-ion batteries in which one of the two electrodes, the anode, is made of graphite. The need for fast charging, he says, “will definitely provide opportunities for new battery chemistries to emerge.” By using new materials for electrodes or charge-carrying ions, he and others have already come up with promising candidates. He predicts the broad adoption of EVs will force a revolution in battery design. Yi Cui, a materials scientist at Stanford University, agrees. “There will be a pushback unless there is a faster charging solution,” says Sarah Tolbert, a battery expert at the University of California (UC), Los Angeles. Whereas filling a gas tank only takes a few minutes, recharging an EV takes anywhere from the better part of an hour to a day, depending on the charging equipment and the size of the battery. But along with high prices and modest range, current EVs have another big drawback: They are slow to recharge. Most new car sales are expected to shift to battery-powered electric vehicles (EVs). California, known for leading the United States in climate regulations, dropped a bombshell last month: By 2035, the state will ban sales of new gasoline powered cars and light trucks.
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