Silicon Anode Materials Rising as Next-gen Option

Silicon, a material for anode materials, is emerging as a “game changer” that will significantly increase driving ranges on a single charge or shorten charging time.

According to the secondary battery material industry on Aug. 16, leading Korean companies such as SK, LG, and POSCO have begun preempting the market and technology by selecting silicon as a next-generation anode material. Graphite is mainly used for anodes for batteries, but silicon can easily increase battery density and dramatically shorten charging time.

SKC established a subsidiary named Ultimus last month to start the silicon anode material business in earnest, and plans to start pilot production within this year. On the other hand, it acquired a 22 percent stake in the U.K.’s Nexeon, which is promoting the establishment of a silicon anode material plant in Gunsan, North Jeolla Province in Korea. SK materials also partnered with U.S.-based Group14 Technologies to establish SK materials Group14 as a joint venture and will invest 250 billion won over six years until 2027 to put a production facility in place in Sangju, North Gyeongsang Province in Korea.

POSCO changed the name of Terra Technos, which it acquired in 2022, to POSCO Silicon Solution and is building a 5,000-ton-per-year silicon anode material plant in Pohang, North Gyeongsang Province in Korea. The project will cost 300 billion won by 2025. The goal is to increase the capacity to 25,000 tons per year by 2030. In July, Lotte Energy Materials also invested 7.9 billion won in Enwires, a French startup company developing silicon nanomaterials for lithium ion batteries used in electric vehicles (EVs).

Silicon, tin oxide (SnO2), and aluminum (AL) are considered candidates to replace graphite for anode materials. Of these, silicon has the highest development speed with the introduction of a method to incorporate less than 5 percent silicon oxide (SiOx) into graphite. Graphite can store one lithium ion per every six atoms, while silicon can store 15 lithium ions for every four atoms, which can increase battery capacity by about 20 times. In terms of energy density, graphite has 350 milliamps (mAh) per gram, while silicon has 1,500 to 2,000 mAh, which is more than four times higher.

“If the proportion of silicon anode materials exceeds 10 percent, the charging time of electric vehicles, which usually takes more than 30 minutes, can be reduced to about 5 minutes,” said an industry insider. “It is expected that the charging time of electric vehicles and gasoline time will be similar, which will trigger the explosive growth of the electric vehicle market.”

Industry insiders expect silicon-carbon (SiC) technology to become a standard in the future. The technology wraps carbon around silicon to suppress volume changes. This is because, although the technology is more difficult, it is more stable and allows for higher silicon content. Currently, China’s BTR is the only company to commercialize SiC technology.

The market is also on the uptick. Hana Securities predicts that the global silicon anode market will grow to US$28.7 billion in 2032, up from US$400 million in 2022. Tesla is considering using silicon anode materials in its next-generation battery, the 4680 cylindrical battery (46 millimeters in diameter and 80 millimeters tall). Porsche is planning to expand the use of silicon anode material-based batteries in the Tycan EV. LG Energy Solution and SK energy are also developing products with silicon anode materials making up more than 10 percent of them.

However, the stability of silicon anode materials and its inability to recover its original form when discharged is a challenge for the battery industry. During battery charging, lithium ions move from the anode to the cathode, causing physical volume expansion of the anode material. This causes battery structure changes and decreases capacity. Silicon anode materials’ volume expansion is about four times larger than that of graphite.