One way out of this problem is to sprinkle small amounts of silicon oxide—better known as sand—throughout a graphite anode. This is what Tesla currently does with its batteries. Silicon oxide comes pre-puffed, so it reduces the stress on the anode from swelling during charging. But it also limits the amount of lithium that can be stored in the anode. Juicing a battery this way isn’t enough to produce double-digit performance gains, but it’s better than nothing.
Cary Hayner, cofounder and CTO of NanoGraf, thinks it’s possible to get the best of silicon and graphite without the loss of energy capacity from silicon oxide. At NanoGraf, he and his colleagues are boosting the energy of carbon-silicon batteries by embedding silicon particles in graphene, graphite’s Nobel Prize-winning cousin. Their design uses a graphene matrix to give silicon room to swell and to protect the anode from damaging reactions with the electrolyte. Hayner says a graphene-silicon anode can increase the amount of energy in a lithium-ion battery by up to 30 percent.
But to push that number into the 40 to 50 percent range, you have to take graphite completely out of the picture. Scientists have known how to make silicon anodes for years, but they have struggled to scale the advanced nanoengineering processes involved in manufacturing them.
Courtesy of SilaNanoTech
Sila was one of the first companies to figure out how to mass-manufacture silicon nanoparticles. Their solution involves packing silicon nanoparticles into a rigid shell, which protects them from damaging interactions with the battery’s electrolyte. The inside of the shell is basically a silicon sponge, and its porosity means it can accommodate swelling when the battery is charging.
This is similar to the approach used by materials manufacturer Advano, which is producing silicon nanoparticles by the ton in its New Orleans factory. To lower the costs of producing nanoparticles, Advano sources its raw material from silicon wafer scrap from companies that make solar panels and other electronics. The Advano factory uses a chemical process to grind the wafers down into highly engineered nanoparticles that can be used for battery anodes.
“The real problem is not ‘Can we get a battery that is powerful?’ It’s ‘Can we make that battery cheap enough to build trillions of them?’” says Alexander Girau, Advano’s founder and CEO. With this scrap-to-anode pipeline, Girau believes he has a solution.
So far, none of these companies have seen their anode material used in a consumer product, but each is in talks with battery manufacturers to make it happen. Sila expects its anodes to be in unnamed wireless earbuds and smartwatches within a year. Advano, which counts iPod cocreator Tony Fadell among its investors, is also in talks to have its anodes placed in consumer electronics in the near future. It’s a long way from EVs, but proving the tech works in gadgets is a small step in that direction.
