Science – New solid state battery overcomes silicon challenge

2021-09-27 New solid state battery operation diagram. A new type of battery that combines two promising development technologies has shown effectiveness for a wide range of applications, from grid storage to electric vehicles. Research Policy and Technology University of California, San Diego

Madrid, 27 years old (European press)

A new type of battery that combines two promising development technologies has shown effectiveness for a wide range of applications, from grid storage to electric vehicles.

The battery uses both a solid-state electrolyte and a silicon anode, making it a solid-state silicone battery. Initial rounds of testing show that the new battery is safe, durable and energy-intensive.

The battery technology is described in the journal Science. The research was led by nanoengineers from the University of California, San Diego, in collaboration with researchers from LG Energy Solution.

Silicon anodes are known for their energy density, which is ten times higher than the graphite anodes most often used in commercial lithium-ion batteries today.

Silicon anodes, on the other hand, have a deficiency in the way they expand and contract as the battery charges and discharges, and in how they decompose with liquid electrolytes. These challenges have kept all silicon anodes out of commercial lithium-ion batteries despite their tempting energy density. New work published in Science provides a promising path for all silicon anodes, thanks to the correct electrolyte.

“With this battery configuration, we are opening new horizons for solid-state batteries that use alloy anodes such as silicon,” Darren HS Tan, lead author of the paper, said in a statement. He recently obtained a PhD in Chemical Engineering. at the Jacobs School of Engineering at the University of California, San Diego and co-founder of UNIGRID Battery, which licenses the technology.

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Next generation solid state batteries with high energy density have always relied on metallic lithium as the anode. But this imposes limitations on battery charging rates and the need for high temperatures (usually 60°C or higher) during charging. The silicon anode overcomes these limitations, allowing faster charge rates in the room at lower temperatures, while maintaining a high energy density.

The team demonstrated a complete lab-level battery that delivers 500 charge-discharge cycles while retaining 80% capacity at room temperature, an exciting advance for the silicon anode and solid-state battery communities.

In addition to removing all carbon and binders from the anode, the team also removed the liquid electrolyte. Instead, they used a solid sulfide-based electrolyte. His experiments showed that this solid electrolyte is very stable in batteries with all-silicon anodes.

The battery consists of a layer consisting of a cathode, a layer of solid sulfide electrolyte and a carbon-free silicon anode. Before charging, the separated silicon microparticles form the energy-dense anode. During the charging of the battery, the positive lithium ions move from the cathode to the positive electrode and a stable 2D interface is formed.

As more lithium ions move toward the anode, they react with the tiny silicon to form bonded molecules of the lithium-silicon (Li-Si) alloy. The reaction continues to spread throughout the electrode. The reaction causes the silicon microparticles to expand and condense, forming a dense Li-Si alloy electrode. The mechanical properties of the Li-Si alloy and the solid electrolyte play an important role in maintaining integrity and contact along the two-dimensional interface.

Aileen Morales

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