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Cathode charge7/5/2023 The thin, porous materials also allow a depleted battery to be brought to a 90 percent state of charge in 10 minutes. The company’s choice of pure silicon is the reason for the battery’s high energy density, says Ionel Stefan, chief technology officer. The nanowires do not swell as much as spherical nanoparticles. The company has improved the process to grow nanowires directly from the metal current collector substrate. Others soon put different spins on this, with spherical silicon nanoparticles, core-shell-type particles made up of silicon cores with protective coatings around them, and silicon particles with etched surfaces.Ĭui cofounded Amprius in 2008 to commercialize the silicon nanowire anode technology. Stanford materials science professor Yi Cui and his lab set off this field of research with a 2008 paper in Nature Nanotechnology on silicon nanowires that withstood swelling. Most of them are looking at nano-engineered silicon as a workaround to the swelling and side-reaction problems. But silicon anode startups want to go much further. Some commercial battery makers, including Tesla, have boosted the lithium-holding capacity of their batteries’ anodes by adding a small amount (usually up to 5 percent) of silicon. And adverse side reactions complicated the process during charging and shortened battery life as well. When researchers first began to explore silicon for lithium battery anodes-as noted above, in 1976, before graphite became the compromise solution-silicon’s drastic swelling and shrinking during charge and discharge quickly disintegrated the anode. Tesla has reportedly added up to 5 percent silicon in its batteries’ anodes. As things stand, nearly all graphite anode material is processed in China. And as the most abundant metal in Earth’s crust, it should be cheaper and less susceptible to supply-chain issues. It not only soaks up more lithium ions, it also shuttles them across the battery’s membrane faster. Silicon promises longer-range, faster-charging and more-affordable EVs than those whose batteries feature today’s graphite anodes. “Silicon has transformed the way we store information, and now it’s transforming the way we store energy,” says Group14’s chief technology officer, Rick Costantino. Group14 began construction of a 20-gigawatt plant in Moses Lake, Wash., in April. All three plan to have domestic gigawatt-scale factories up and running in the next few years. Department of Energy and, for Group14, another $214 million in private investment. In late 2022, Group14, Sila, and Amprius Technologies in Fremont, Calif., raised nearly half a billion dollars to commercialize their anode materials, with US $250 million from the U.S. Group14 Technologies, in Woodinville, Wash., should have its silicon battery setup in a Porsche EV by next year. Alameda, Calif.–based Sila Nanotechnologies’ silicon anode, which has powered the Whoop fitness tracker since 2021, will be in the Mercedes G-Class SUV by 2026. General Motors and OneD Battery Sciences in Palo Alto, Calif., are putting OneD’s silicon nanotechnology into GM’s Ultium battery cells. Some carmakers and silicon anode startups have teamed up to produce longer-range, lower-cost EVs that could be on the road by mid-decade. “Silicon has transformed the way we store information, and now it’s transforming the way we store energy.” –Rick Costantino, Group14 Now, however, after some 15 years of incremental improvements and dashed hopes, silicon’s time as a mainstay material in batteries has finally arrived. But experiments with that element have been plagued by technical challenges-including volume expansion of the anode when loaded with lithium ions and the resulting material fracture that can happen when an anode expands and contracts. In fact, silicon’s first documented use as a lithium battery anode even predates that of graphite- by seven years. Silicon has long held out promise as a medium for anodes, because it can hold 10 times as many lithium ions by weight as graphite. Lithium-ion batteries’ graphite anodes, by contrast, have largely stayed the same. And yet even for the technology’s vast advancements-a staggering thirtyfold drop in price between 19, for instance-the biggest improvements have taken place mostly on the lithium-metal-oxide cathode side. Since lithium-ion batteries’ commercial debut three decades ago, this portable and high-density (and Nobel Prize–winning) energy storage technology has revolutionized the fields of consumer electronics, electric vehicles, and large-scale energy storage.
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