Among the many companies in the United States that develop silicon negative electrode materials, there is a very young small company called Group14 Technology, which was founded in Seattle in 2016. Although this company is very young, it has attracted a lot of attention because it was closely related to some well-known companies before and after its establishment.

Group14 is an independent company named EnerG2. EnerG2 is a company that develops and produces carbon materials, established in 2003. In the more than ten years since its establishment, it has attracted a total of $30 million in financing and has been cooperating with German giant BASF since 2014. In the end, BASF acquired EnerG2 in 2016, hoping to leverage its mature technology in carbon materials to enter the commercial field of lithium battery negative electrode materials.

In the same year that EnerG2 was acquired by BASF, several leaders of EnerG2 received a $2.8 million funding from the US Department of Energy to fund research on silicon carbon composites. So they decided to use this money to establish a separate company to continue their entrepreneurship, and did not include this business in the acquisition deal with BASF. This is why Group14 was established. BASF will certainly not miss this potential opportunity, so it continues to bet on investing in Group14 to support the development of new materials.

In 2019, Group14 conducted Series A financing and raised $18 million, with investors including CATL, Showa Electric, Cabot, and BASF. At the beginning, he was very favored, indicating that everyone believed in BASF's vision.

In September 2020, Group14 teamed up with several partners to secure another $4 million R&D funding from the US Department of Energy to fund a new battery negative electrode material project. Our partners include Cabot (Carbon Materials Company), Funeng Technology (Battery Company), Silatronix (Electrode Materials Company), Arkema (French Materials Company Giant), and the Northwest Pacific National Laboratory in the United States. Xitai Laboratory has many years of research experience in silicon negative electrode materials and has published many top tier journal papers. It is a very powerful research and development engine for silicon negative electrode materials in the United States.

In December 2020, Group14 announced a Series B financing of $17 million, led by South Korean giant SK, adding another halo to the group. This means that in just two years, Group14 has received over $39 million in funding, which can be described as rapid development. Group14 announced that it will use this round of financing to increase production capacity and accelerate the production of flagship product SCC55 ™ Silicon carbon composite negative electrode materials to meet the rapidly growing demand in the power battery market. This flagship product increases energy storage density by 50% compared to traditional graphite negative electrodes. The company expects to start supplying its partners in early 2021.

According to Group14's website and previous news reports, the way Group14 produces silicon carbon composite materials is to first manufacture carbon particles with a porous structure like a sponge using polymer materials, and then add silicon nanoparticles to the pores of the carbon particles to form a composite material. In order to gain a clearer understanding of Group14's technology, we conducted in-depth research on the technology patents applied by Group14 and its predecessor EnerG2 company to explore the competition.



EnerG2 applied for several patents before 2016, describing how to prepare silicon carbon composite materials. One of the methods is shown in the figure below. Firstly, the nano silicon material (spherical, linear, or tubular) is dispersed in an organic solvent, and a monomer of polymethyl methacrylate (PMMA, commonly known as organic glass) is added to form a polymer covering the surface of the nano silicon material. Add another set of reactants and wrap a layer of resorcinol formaldehyde polymer (RF) outside the particles. Wash the particles and heat them to above 600 degrees Celsius. The inner layer of organic glass completely decomposes, leaving a layer of voids. The outer layer of RF forms carbon particles to form a protective layer, which is also commonly known as the yolk eggshell structure.

Another method for preparing silicon carbon composite particles is to dissolve the aluminum metal in the silicon aluminum alloy particles with acid, and the remaining porous silicon particles are dispersed into a polymer prepolymer solution, allowing the prepolymer to immerse into the pores. Then, the prepolymer is heated to react and transform into a polymer material. The high-temperature carbonization of the polymer transforms it into a carbon material, which fills the pores and outer layer of the silicon particles, protecting the silicon material. The following image is an electron scanning electron microscope image of a porous silicon particle.

Group14 began applying for patents around 2016, one of which described several methods for preparing silicon particles with nano pores from silicon aluminum alloys. The first method is to disperse silicon aluminum alloy particles in an acid solution, dissolve the aluminum metal in the particles using the acid solution, and the remaining silicon material becomes particles with nano micropores (as shown in the figure below). It can also be further crushed into smaller particles according to application needs. The second method is to heat the silicon aluminum alloy particles in a closed container to a high temperature of several hundred degrees, and then introduce corrosive gases such as chlorine, hydrogen chloride, fluorine, etc. The gases react with the aluminum metal to form metal salts. Then, the metal salts can be removed by water dissolution, and the remaining silicon material becomes particles with nanopores.

Group14 has also applied for several patents on how to prepare silicon carbon composite materials. The earliest method was to introduce silane gas into the pores of porous carbon particles, and by heating, the gas precipitated into silicon nanoparticles dispersed in the pores of porous carbon. The size of porous carbon particles is generally between 1 and 10 microns, and the size of silicon particles precipitated in the pores is generally below 100nm. The following electron microscope photo shows the appearance of nano silicon particles dispersed within the pores of carbon particles.

However, the cost of preparing silicon carbon composite materials mentioned above is too high and not suitable for large-scale production, so Group14 subsequently announced a new preparation method. Select specific polymer prepolymers, polymerize them into polymer materials, and carbonize the polymer materials at high temperatures to obtain carbon particles with porous structures. Inject silicon containing compounds into carbon particles, heat them to decompose the silicon containing compounds into nano silicon particles and fill them in the pores. Next, an additional layer of carbon coating can be added, which can be filled with polymer prepolymers into the pores of carbon particles, heated and decomposed to form a carbon layer covering the nano silicon particles; It is also possible to wrap the entire carbon particle inside a polymer material, and then heat and decompose it to form a carbon layer that covers the outside of the entire carbon particle. The product obtained through this method is similar to the description on the Group14 official website, as shown in the following figure - the large black and white sphere in the middle represents silicon nanoparticles and pores, and the small black dots surrounding it represent carbon atoms. Therefore, we speculate that this is the technology that Group14 will be investing in large-scale production.

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Reference:

1. Group14 company official website https://www.amprius.com/

two Compositesof porous nano-featured silicon materials and carbon materials， US Patent Application No. 20190097222.

three Nano-featuredporous silicon materials, US Patent Number 10763501.

four Compositecarbon materials comprising lithium alloying electrochemical modifiers， US Patent No. 10714744.

five Decompositionof silicon-containing precursors on porous scaffold materials， US Patent Application No. 20200020935.

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Author Introduction:

Dr. Xie Wei, Bachelor and Master of Materials Science from Tsinghua University, and Ph.D. in Chemical Engineering from the University of Texas (Austin) in the United States. Mainly engaged in the development of energy storage batteries, has held important positions in multinational corporations and startups, led multiple research and development projects funded by the US Department of Energy, and won the 2013 US Annual 100 Best Research and Development Technology Award. Published 17 papers in top journals in materials science and energy storage, served as a reviewer for 5 international journals, and has applied for 17 international invention patents.

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Shenzhen ZH Energy Storage Technology Co., Ltd. is committed to the research and development, promotion, and application of energy storage technology, aiming to help achieve China's goal of "carbon neutrality" through the application of electrochemical energy storage technology. In the early stages of development, the company focused on providing technical support and consulting services to the Chinese energy storage market by leveraging its accumulated industry experience and outstanding research and development capabilities in the field of energy storage. At the same time, the company focuses on conducting research and analysis on the Chinese energy storage market, and developing or introducing the most advanced and effective energy storage technologies for the Chinese market.

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