GS Yuasa Corporation (Tokyo Stock Exchange: 6674) today announced that consolidated subsidiary GS Yuasa International Ltd. (“GS Yuasa”) has developed a technology that achieves both higher energy density and longer service life through a series of improvements in silicon based negative electrode batteries, which face many practical challenges. We applied this technology to demonstrate a high energy density of 400 Wh/kg, higher than that of conventional lithium-ion batteries, and confirmed that superior charge-discharge cycle life performance can be obtained with an energy density retention rate of over 90% after 200 cycles and a retention rate of over 85% after 300 cycles. This silicon based negative electrode technology is also applicable to all-solid-state batteries, which are expected to see technological innovation and widespread use going forward.

Although many studies have been conducted on silicon based negative electrode active materials as new alternatives to carbon-based negative electrodes due to their high theoretical capacity per mass and abundant resources, practical applications have been difficult due to the challenges caused by the volume change associated with charging and discharging. GS Yuasa has now achieved substantial progress in terms of the practical application of advanced lithium-ion batteries using silicon based negative electrodes through improvements in binders and electrolytes.

[Features of silicon based negative electrode batteries]
- Very high theoretical capacity per unit mass compared to conventional graphite negative electrodes
- Abundance of resources

[Issues associated with silicon based negative electrode batteries]
- Isolation of silicon based negative electrode active material progresses *1 due to the volume change associated with charging and discharging, leading to a decrease in charge-discharge cycle life performance.
- Volume change causes cracks in the SEI coating *2 and electrolyte decomposition and lithium consumption progress during the repair process, resulting in deterioration of charge-discharge cycle life performance or gas generation problems.

[Technology developed by GS Yuasa]
- Successfully reduced isolation of silicon based negative electrode active materials by improving the binder.
- Successfully reduced lithium consumption during charge-discharge cycles by improving the electrolyte, almost eliminating gas generation.
- Improved the battery design based on the results of the abovementioned elemental technologies.

We will continue to improve battery performance with the aim of bringing these technologies into active use as soon as possible. GS Yuasa will continue to contribute to achieving carbon neutrality by developing high-performance batteries, including those with higher energy density.

*1 A phenomenon in which the active material in an electrode ceases to contribute to charging and discharging due to a broken conductive path.
*2 A coating formed on the surface of the negative electrode active material particles as a result of the reductive decomposition of the electrolyte. The coating acts as a passivation, preventing further reductive decomposition of the electrolyte.