Solid State Batteries: A New High-Performance Model Surprised Even Its Developers

Nano-engineers from the University of California, San Diego, in collaboration with LG Energy Solution researchers, have created a new type of battery that weaves two promising battery subfields into a single solution. The battery uses both a solid state electrolyte and a full silicon anode, making it a solid state silicon battery. First tests show the new battery is safe, long-lasting, high energy density and promising for a wide range of applications, from grid storage to electric vehicles.

Silicon anodes are known for their energy density, which is 10 times higher than that of graphite anodes often used in commercial lithium-ion batteries. Silicon anodes, on the other hand, are notorious for the way they expand and contract with battery charging and discharging and because of the way they degrade with liquid electrolytes. These challenges have kept anodes of this type away from commercial lithium-ion batteries, despite their puzzling energy density. However, new work published in Science provides a promising pathway for all silicon anodes, thanks to the correct electrolyte.

In fact, much of the problem is caused by the interaction between the silicon anodes and the liquid electrolytes with which they are coupled. The situation is complicated by the expansion of large amounts of silicon particles during charging and discharging. This results in huge losses in capacity over time.

The team led by the University of California, San Diego, took a different approach: They got rid of the carbon and binders typically used with all-silicon anodes, while also using micro-silicon, which is less processed and less expensive than the more commonly used nanoscale silicon. frequently.

In addition to removing all the carbon and binders from the anode, the team also removed the liquid electrolyte, using a sulfide-based solid electrolyte instead. Their experiments showed that this solid electrolyte is very stable in all-silicon anode batteries.

In this way, the researchers avoided a number of related challenges that arise when the anodes themselves are immersed in the liquid organic electrolyte during battery operation. At the same time, by eliminating carbon in the anode, the team significantly reduced unwanted contact and side interactions with the solid electrolyte, avoiding the continued capacitance loss that typically occurs with liquid electrolytes.

New generation high-density solid-state batteries have always been based on lithium metal as the positive electrode. But this places limits on battery charging rates and the need for a high temperature (usually 60°C or higher) when charging. The silicon anode overcomes these limitations, allowing much higher charge rates at lower ambient temperatures while maintaining a high energy density. The team demonstrated a complete lab cell that delivers 500 charge and discharge cycles while maintaining 80% capacity at room temperature.