electric vehicle battery

Solid-state battery promises high energy density

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A new type of battery that combines a solid-state electrolyte with an all-silicon anode to deliver superior energy density has been developed by researchers from University of California San Diego.

The team said that initial tests have demonstrated that the battery is safe and long lasting and believe it holds promise for applications such as grid storage or electric vehicles.

Silicon anodes typically have an energy density around 10 times greater than the graphite anodes most often used in lithium ion batteries. But the anodes also expand and contract as the battery charges and discharges and degrade quickly with liquid electrolytes.

Until now, these factors have kept all-silicon anodes out of commercial lithium ion batteries despite their tantalising energy density.

“With this battery configuration, we are opening a new territory for solid-state batteries using alloy anodes such as silicon,” said Darren HS Tan, the lead author on the paper.

Next-generation solid-state batteries with high energy densities have always relied on metallic lithium as an anode.

But that places restrictions on the battery charge rates and need for elevated temperature (usually 60 degrees Celsius or higher) during charging. The silicon anode overcomes these limitations, allowing much faster charge rates at room temperatures, while maintaining high energy densities.

The team demonstrated a laboratory scale full cell that delivers 500 charge and discharge cycles with 80 per cent capacity retention at room temperature.

By swapping out the liquid electrolyte for a solid electrolyte, and at the same time removing the carbon and binders from the silicon anode, the researchers avoided a series of challenges that arise when anodes become soaked in the organic liquid electrolyte as the battery functions.

The team also significantly reduced the interfacial contact, which often causes unwanted side reactions, with the solid electrolyte, avoiding continuous capacity loss that typically occurs with liquid-based electrolytes.

“The solid-state silicon approach overcomes many limitations in conventional batteries. It presents exciting opportunities for us to meet market demands for higher volumetric energy, lowered costs, and safer batteries especially for grid energy storage,” Tan added.

The study was carried out with support from LG Energy Solution, which hopes to be able to use the technology in commercial products eventually.

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