RENA leans on solar knowledge to develop mass etching process for lithium-ion batteries

RENA Technologies, a German supplier of wet chemical processing equipment for the solar industry, has teamed with the Christian Albrecht University in Kiel (CAU) to develop a new manufacturing process for silicon anodes in lithium-ion batteries that leans on the similar inline techniques employed by RENA in the solar industry.

Boasting vast experience in developing machinery for the processing of solar cells, RENA turned its attention and expertise to the growing storage industry, specifically in the development of silicon anodes that can be used to boost the efficacy and performance of lithium-ion batteries, which are the most commonly used chemistries in stationary storage applications.

Working alongside CAU experts, RENA and the team discovered that silicon is able to handle a greater number of lithium ions than graphite, which is the go-to material used for the production of anodes.

Anodes made from silicon, however, boast energy density ten times greater than graphite. The problem has long been that silicon becomes unstable when loaded with lithium ions, meaning that silicon anodes’ cycle life is very short.

To overcome this shortfall, CAU researchers employed an electrochemical etching step to structure the silicon in such a way as to incorporate voids in the anode that allow silicon to expand without fracturing.

This process, though effective, was not suitable for mass production because it typically requires the sealing of processed substrates in order to avoid short currents between positive and negative electrodes. Hence, anything that requires a high throughput in production – such as lithium-ion batteries – would be unsuitable for the etching process.

Enter RENA. The German firm can adapt its solar cell inline process by simplifying its machine to handle electrochemical etching of silicon at mass volume, and is currently working with CAU to better understand the delicacies at hand.

“RENA’s experience in equipment and process development is an important factor to transfer this technology into industry,”, CAU researcher Sandra Hansen said.

Franck Delahaye, business development manager at RENA added: “CAU’s profound knowledge in material science, silicon anodes and battery manufacturing will be key to integrate the silicon material processed on our system into high performance lithium ion batteries.”

Beyond battery manufacturing, the inline system is also suitable for further high throughput applications such as solar cell manufacturing. “There the porous silicon can serve as detachment layer to separate epitaxial structures such as solar cells or wafers that are deposited onto the silicon wafer following the electrochemical etching step”, Delahaye concluded.