Nano engineers from the University of California, San Diego, in collaboration with LG Energy Solution researchers, have developed a new type of battery that weaves two promising battery subdivisions into a single solution. The battery uses both a solid state electrolyte and a full silicon anode, forming a solid-state silicon battery. First test runs show that the new battery is safe, long lasting and has high energy density and is reliable for a wide range of applications ranging from grid storage to electric vehicles.
Silicon anodes are famous for their energy density, which is 10 times higher than the graphite anodes most commonly used in today’s lithium ion batteries. Silicon anodes, on the other hand, are notorious for expanding and contracting as battery charges and discharges and decomposing with liquid electrolytes. These challenges have kept these types of anodes out of commercial lithium ion batteries, albeit confusing energy density. However, the new work published in Science offers a promising path for all silicon anodes, thanks to the right electrolyte.
In fact, most problems are caused by the interaction between silicon anodes and the liquid electrolytes to which they are attached. The situation is complicated by the fact that the silicon particles expand greatly during charging and discharging. This causes severe capacity losses over time.
The team led by UC San Diego took a different approach: they removed the carbon and binders commonly used with all silicon anodes, while also using micro silicon, which is less processed and less expensive than the more commonly used nano silicon. Frequently
In addition to removing all carbon and binders from the anode, the team also removed the liquid electrolyte and used a solid sulfide-based electrolyte instead. Their tests showed that this solid electrolyte was more stable than full silicon anode batteries.
In this way, the researchers avoided many of the challenges that arise when the anodes are immersed in an organic liquid electrolyte while the battery is running. At the same time, by removing the carbon in the anode, the group significantly reduces unwanted contact and side reactions with the solid electrolyte, avoiding the potential loss that usually occurs with liquid-based electrolytes.
New generation high energy density solid state batteries have always relied on lithium metal as anode. But it does impose restrictions on battery charge rates and higher temperatures (typically 60 degrees Celsius or higher) when charging. The silicon anode exceeds these limits, allowing higher charge rates while maintaining higher energy densities at lower ambient temperatures. The panel demonstrated a complete laboratory-sized cell that provides 500 charging and discharge cycles with 80% capacity retention at room temperature.
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