Thermal evaporation emerges as a promising strategy for scalable solid-state battery production

Solid-state lithium batteries are promising energy storage solutions that utilize solid electrolytes as opposed to the liquid or gel electrolytes found in traditional lithium-ion batteries (LiBs). Compared to LiBs and other batteries that are used worldwide, these batteries could attain significantly higher energy densities of more than 500 Wh/kg⁻¹ and 1,000 Wh/l⁻¹, which could be advantageous for powering electric vehicles and other electronics for longer periods of time.

Despite their possible advantages, existing solid-state lithium batteries exhibit significant limitations that have so far prevented their large-scale deployment. These include the active lithium loss that can occur while the batteries are charged and discharged, which can reduce their efficiency and overall performance.

This loss of lithium is caused by an inhomogeneous lithium plating. Devising effective strategies and thin lithium metal foils that could limit the loss of lithium in solid-state batteries is thus a key goal for the energy research community.

Researchers at University of Oxford, the Faraday Institution, Nissan Motor Co. Ltd. and other research institutes recently carried out a study exploring the different technologies and processes for creating thin lithium metal anodes for solid-state batteries. Their paper, published in Nature Energy, summarizes the results of a detailed technical and economic analysis, suggesting that thermal evaporation could be a promising strategy for the scalable fabrication of these films.

“Solid-state lithium metal batteries show substantial promise for overcoming theoretical limitations of Li-ion batteries to enable gravimetric and volumetric energy densities upwards of 500 Wh kg⁻¹ and 1,000 Wh l⁻¹, respectively,” wrote Matthew Burton, Sudarshan Narayanan and their colleagues in their paper.

“While zero-lithium-excess configurations are particularly attractive, inhomogeneous lithium plating on charge results in active lithium loss and a subsequent coulombic efficiency penalty.”

Current approaches to tackle the active lithium losses observed in solid-state batteries rely on the use of excess lithium. Yet excess lithium adversely impacts the batteries’ energy density, thus the reliable fabrication of lithium foils with limited thickness is of utmost importance.

Burton, Narayanan and their colleagues performed various analyses and calculations aimed at investigating the potential of different manufacturing methods and technologies for fabricating these thin lithium films on a large scale. Their analyses suggest that thermal evaporation could be a particularly promising and cost-effective method for creating these key solid-state battery components.

“We discuss the viability of various technologies for realizing thin lithium films that can be scaled up to the volumes required for gigafactory production,” wrote Burton, Narayanan and their colleagues.

“We identify thermal evaporation as a potentially cost-effective route to address these challenges and provide a techno-economic assessment of the projected costs associated with the fabrication of thin, dense lithium metal foils using this process. Finally, we estimate solid-state pack costs made using thermally evaporated lithium foils.”

The paper by Burton, Narayanan and their colleagues could inspire future efforts aimed at developing scalable solid-state lithium batteries, for instance, encouraging more researchers to create lithium metal anodes with thermal evaporation. Eventually, this could help to improve the performance and reliability of these promising battery solutions, which could in turn contribute to their commercialization and widespread adoption.

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