Environmental problems including climate change are caused by human activity and population explosion, and are becoming serious issues because of the increase in greenhouse gases such as methane and carbon dioxide (CO2). Replacing petroleum consuming cars with hybrid, electric, and fuel cell cars is one of the ways to reduce CO2 emissions from automobiles. Also, building smart-grid society and replacing coal based thermal power generation is another efficient way to reduce greenhouse gases. Rechargeable batteries are very important devices since they can store electricity which is produced by sustainable energy sources such as wind power and solar cells. So far, lithium ion batteries are one of the representative rechargeable batteries in a modern society. Therefore, the challenge to increase the capacity of lithium ion batteries is an extremely important task.
Green Science Alliance is the medium sized startup company in Japan that focuses on researching cutting edge technology, especially in the field of energy and environmental green science. One of their businesses is developing cutting edge rechargeable batteries. They synthesize electrode, electrolyte material themselves. In addition, they make coating ink, test the battery, measure their electrochemical properties, and analyze the detail and all procedures can be done within their company.
Silicon metal and silicon monoxide have great potential to become an excellent anode material for lithium ion battery because their theoretical capacity is 4200 mAh/g for silicon metal, and 2007 mAh/g for silicon monoxide. However, their large volume change caused by charge discharge cell cycle is the big problem and is why those materials have not been largely practically used yet in the lithium ion battery industry.
Mr. Katsuji Konishi and Dr. Ryohei Mori at Green Science Alliance Co., Ltd. have developed SiO (silicon monoxide) based lithium ion battery. They used commercially available SiO powder (even Green Science Alliance synthesize various type of electrode, solid electrolyte, SiO is an exception, and used SiO powder from other company) and prepared coating ink, and made SiO based lithium ion battery. After long time effort, when they applied one of SiO coating ink and used as an anode for lithium ion battery, it exhibited large capacity such as approximately 1700 – 1800 mAh/g, which means that the capacity is 4 - 5 times larger than that of normally used graphite anode. Capacity decay was within 5% after 20 - 30 times cell cycle which is quite stable. The test battery was composed of SiO electrode prepared by Green Science Alliance, and lithium metal as counter electrode. Electrolyte was ordinate carbonate based electrolyte and measurement was performed with 0.1 – 0.2 C of charge discharge current at room temperature.
This is a big step for the lithium ion battery industry.
They will keep investigating the stability against higher current, and longer cell cycles. They will also combine with other materials such as LLZO solid electrolyte, ionic based electrolyte, in order to increase safety of the battery, as well as reaching for higher lithium ion battery capacity. Green Science Alliance is planning to manufacture lithium ion battery in the near future.