The company has shrunk the size of the battery by half by swapping graphite for thin, high-energy lithium-metal foil, which can hold more ions and which is about one-fifth the thickness of a traditional lithium metal anode, as well as several times thinner and lighter than traditional graphite, carbon, or silicon anodes.
Qichao Hu, co-inventor of the battery and CEO of SolidEnergy said: “Electric vehicles typically go at least 200 miles on a single charge. Despite making the battery half the size and half the weight, it will travel the same distance. Alternatively, we can make it the same size and same weight, and it will go 400 miles on a single charge.”
Solid Energy had to address a number of technical issues. Lithium metal tends to reacts poorly with the electrolyte and forms compounds that increase both resistance in the battery and reduce cycle life. This reaction also creates dendrites on the anode, which lead to short circuits, generating high heat that can ignite the flammable electrolyte, and make the battery non rechargeable. Another major setback was that the battery only worked at 80°C or higher.
These problems were addressed by developing a solid and liquid hybrid electrolyte solution. According to Hu, he coated the lithium metal foil with a thin, solid electrolyte that didn’t need to be heated to function. He also created a quasi-ionic non-flammable liquid electrolyte and added chemical modifications to the separator and cell design to stop it from negatively reacting with the lithium metal.
SolidEnergy plans to bring the batteries to smartphones and wearables in early 2017, and to electric cars in 2018. But the first application will be drones, coming this November.