Solid state battery vs lithium ion12/26/2023 ![]() Lithium is at least malleable at room temperature and can be pressed into the craggy surfaces of a material, but there's still the connection to the cathode. They must match the relatively easy seal between a liquid electrolyte and the cathode and anode-the liquid simply forms around them. Solid electrolytes present additional challenges. And if dendrites still manage to push through the ceramic electrolyte, there’s no flammable reactivity. Scientists eventually landed on a solution that prevented the growth of dendrites and eliminated the risk of fire: a solid electrolyte-often made of a ceramic similar to a semiconductor-that replaced the flammable liquid electrolyte and physically blocked the growth of dendrites. The liquid electrolyte is a flammable solvent just waiting to be ignited-it’s the fuel behind the battery fires on airplanes that have made recent headlines. In a traditional lithium-ion battery with a liquid electrolyte, that can lead to a fire. Dendrites, which are also a problem for lithium-ion batteries, can puncture battery parts and short-circuit the cell. The main form of lithium corrosion in batteries are dendrites, which are branched lithium structures that grow out from the anode. You can think of it as corrosion-if you get it in contact with anything, it corrodes everything.” “The difficulty is, lithium metal is too reactive. Chief among them, says Liu, is its reactivity. To tap lithium’s potential, researchers have spent decades working through the metal’s numerous roadblocks. However, lithium metal’s capacity is 10 times that of graphite. This material is plentiful, conducts well, and is easy to work with. ![]() The cathode (positive electrode) is a lithium compound, and the anode (negative electrode)-which determines total storage-is made of graphite. Current lithium-ion batteries use a liquid electrolyte where ions flow back and forth between the anode and cathode, recharging and discharging electrons (see How Lithium-Ion Batteries Work, below). The energy density of lithium-ion cells is as much as four times greater than that of the nickel-cadmium batteries they’ve largely replaced. And compared with other alkalis, such as potassium or sodium, lithium has the smallest ion size-and third-lowest atomic weight on the periodic table-meaning more electrons and charge for a given battery size. ![]() “That creates a really high voltage,” he explains. Like its fellow alkali metals on the far left of the periodic table, lithium has a single outer electron that it easily gives up, says Jeff Sakamoto, Ph.D., a mechanical engineering professor at University of Michigan who specializes in solid-state battery research. Lithium has been the focus of battery research for decades because it’s an excellent conductor. Sakamoto and his team created a battery with double the output of lithium ion. He felt confident, but a little apprehensive: “We knew we could make something that looked like a battery cell, but there was still a chance we’d have a brick.” Josh Buettner-Garrett, Solid Power’s chief technology officer, monitored from his office. ![]() Then on August 7, 2021, three engineers donned protective Tyvek “bunny suits,” entered the dry room, and drew voltage from the largest prototype lithium-metal battery to date. Solid Power was aiming for more modest gains in its first prototypes, but could still see an 80 percent improvement in the near future. The technology, in theory, sounded too good to be true: a 10x jump in power (or 10x drop in size) from traditional lithium-ion cells. The cells, a shining silver contrast to their surroundings, were a moonshot. It’s here in the humidity- and contaminant-free production area where Solid Power produced their first full-size solid-state lithium-metal battery cells. The dry room at Solid Power’s Louisville, Colorado, facility is abrasively bright, and yet the low, encompassing hum of the fans and chillers is oddly soothing. ![]()
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