New technology may cut electric vehicle charging times and boost their range
Atechnology that could dramatically increase the range and decrease the charging time of electric vehicle (EV) batteries could soon be in many more cars. The technology swaps the graphite normally used on the negatively charged anodes of lithium-ion EV batteries for silicon. Panasonic recently announced a partnership with Sila Nanotechnologies, which makes the silicon anodes, to integrate the technology into the company’s existing battery production line in 2024.
Over 14 million electric vehicles were sold in 2023, and their popularity is expected to increase in the coming years. Currently, these vehicles use high-performance lithium-ion batteries. While these batteries are getting better every day, some obstacles still limit their usability and convenience. “The capability of a battery to store energy in relation to its size and weight, known as energy density, is a key factor for electric vehicles, as it affects the distance they can cover on a single charge,” said Azin Fahimi, chief scientific officer at Sienza Energy, who leads a team working on a different silicon anode implementation than Sila. “Another crucial aspect is power density, which refers to how quickly a battery can supply energy.” In other words, if a car can’t go very far between charges, it’s a nonstarter for many consumers. So why does the new silicon anode have such a dramatic impact on the range and charge time?
Batteries rely on the movement of charged particles, known as ions, between the electrodes, or two electrical conductors. During charging, lithium ions move from the positive electrode, called the cathode, through a conducting solution called the electrolyte and into the negative electrode – the anode – where they are stored until power is needed. “When the battery is providing power to a device, the lithium ions move back from the anode to the cathode,” Fahimi said. “This movement of ions allows electrons to flow through the external circuit, generating an electric current that powers the device.”
Because the ions are stored on the anode until they’re needed to power the car, the anode material plays a critical role in a battery’s performance. “A good anode should possess a high lithium storage capacity to ensure high energy density, good electrical conductivity to facilitate efficient electron flow and fast ion transport for rapid charging capabilities,” Fahimi said. The anode also needs a stable structure that doesn’t change in volume when ions are flowing in and out of it, as this can damage the surface.
Conventionally, lithium-ion batteries have used graphite anodes. The layered structure of this conducting material means ions can move into and out of the anode without it changing much in volume. However, due to its chemistry, silicon can hold more than tenfold more energy per gram. “This higher capacity means that silicon can store more lithium ions, resulting in a higher energy density,” Fahimi said. “A higher energy density translates to a longer range for electric vehicles on a single charge.” Unfortunately, silicon swells to three or four times its original size when filled with lithium ions, leading to “mechanical stress and eventual degradation of the anode material.” Careful nanoscale design of the silicon anode is crucial to overcoming this challenge.