Solid-state silicon batteries could last longer and charge faster | Engadget

Researchers from UC San Diego, supported by LG Energy, have made a promising discovery that involves two popular types of battery tech. They created a solid-state battery with an all-silicon anode that could potentially deliver long life, high energy density and fast charging — potentially making EVs cheaper and more practical. 

Silicon is a highly desirable anode material as it has over ten times the energy density of current graphite anodes. The problem is that silicon anodes tend to expand and degrade quickly as a battery charges and discharges, particularly with the liquid electrolytes currently used in lithium-ion cells. That issue has helped keep them out of commercial batteries. 

Meanwhile, the challenge with solid-state batteries (with solid instead of liquid electrolytes) is that they use metallic lithium anodes that must be kept at elevated temperatures (140 degrees F) during charging. That makes them less practical in cold weather, requiring heaters that consume valuable energy.

The solution to both these problems is a special type of silicon anode in a solid-state battery, according to the US San Diego team. They eliminated the carbon and binders typically used in silicon anodes and replaced the liquid electrolyte with a sulfide-based solid electrolyte. 

With those changes, they demonstrated that the all-silicon anodes were much more stable in the solid electrolyte, retaining 80 percent capacity after 500 charge and discharge cycles done at room temperature. It also allowed for faster charging rates than previous silicon anode batteries, the team said. 

The team has already licensed the tech to a company called Unigrid battery, and LG Energy Storage plans to expand the research. The work is particularly promising for grid storage, according to lead author Darren H.S. Tan. However, it’s still in the experimental stages and “there is more work to do,” the team acknowledged. And of course, a lot of batteries that work great in labs have failed to do so in the real world. The paper was published in the Science journal and also appeared earlier on Arxiv.