Engineers Have Developed a New Solid-state Battery with a Pure-Silicon Anode

With the increasing adoption of electric vehicles and more interest in grid energy storage devices, there is a rising demand for new battery technologies that provide significant advantages relative to currently dominating energy storage devices.

Lithium-ion technology is currently dominating the rechargeable battery space. In lithium-ion batteries, during charging, lithium flows to the anode typically made of graphite. If we swap graphite with silicon, more lithium ions can be stored in the anode, which increases the energy storage capacity of the battery.

Silicon anodes exhibit 10 times greater energy density than the graphite anodes commercially used. Moreover, silicon anodes can enable fast-charging batteries. Solid-state batteries with high energy densities incorporate metallic lithium as an anode. But that limits the rate of charging and requires elevated temperatures for fast charging. Silicon anodes overcome these issues and hence allows for faster charge rates at room temperatures. 

However, silicon anodes change their volumes significantly (approximately 400%) during charging and discharging. Therefore, commercial battery anodes only consist of small amounts of silicon for boosting performance, but the commercialization of all-silicon anodes in lithium-ion batteries is hampered due to these challenges.

Researchers from the University of California San Diego have combined the benefits of an all-silicon anode and solid-state electrolyte into a single silicon-all-solid-state battery. The tests performed by the researchers show that the developed battery is safe, long-lasting, and energy-dense.

 

Replacing Graphite for Silicon

Considering the potential of silicon for high energy density batteries, researchers across the globe have looked into replacing conventional graphite anodes for silicon. However, silicon anodes, in addition to volume change, suffer from performance degradation over various charge-discharge cycles. This degradation is due to the interaction between silicon and the highly reactive liquid electrolytes. The degradation combined with volume expansion results in severe capacity loss over time.

The UCSD researchers eliminated carbon and the binders that are usually inserted with all-silicon anodes. Moreover, they replaced the liquid electrolyte with a sulfide-based electrolyte due to its stability with all-silicon anodes. In addition, they used micro-silicon, which is less expensive than nano-silicon and easy to manufacture. 

The elimination of carbon in the anode significantly reduces the interfacial contact with a solid electrolyte, which could have resulted in continuous capacity loss.

Eliminating carbon from the anode and replacing liquid electrolytes allowed the researchers to fully exploit the benefits of low cost, high energy density, and eco-friendliness.

The all solid-state battery with a sulfide solid electrolyte layer during the charging process. Image Courtesy of UC San Diego.

 

The study has been supported by LG Energy Solutions Open Innovation Program. According to the researchers, the work will continue at UCSD, including additional research collaboration with LG Energy Solution.

"LG Energy Solution is delighted that the latest research on battery technology with UC San Diego made it into the journal of Science, a meaningful acknowledgment," said Myung-hwan Kim, President, and Chief Procurement Officer at LG Energy Solution. "With the latest finding, LG Energy Solution is much closer to realizing all-solid-state battery techniques, which would greatly diversify our battery product lineup." 

The research “Carbon Free High Loading Silicon Anodes Enabled by Sulfide Solid Electrolytes,” appeared in the Sept. 24, 2021 issue of Science.

 

Researchers Involved in this Project

Darren H. S. Tan, Yu-Ting Chen, Hedi Yang, Wurigumula Bao, Bhagath Sreenarayanan, Jean-Marie Doux, Weikang Li, Bingyu Lu, So-Yeon Ham, Baharak Sayahpour, Jonathan Scharf, Erik A. Wu, Grayson Deysher, Zheng Chen, and Ying Shirley Meng from the Department of NanoEngineering, Program of Chemical Engineering, and Sustainable Power & Energy Center (SPEC) University of California San Diego Jacobs School of Engineering.

Hyea Eun Han, Hoe Jin Hah, Hyeri Jeong, Jeong Beom Lee, from LG Energy Solution, Ltd.