Enevate Company was founded in California in 2005, and one of its founders and CTO, Benjamin Park, was still a doctoral student at the University of California, Irvine. After obtaining his doctoral degree, he continued to stay at the university for postdoctoral research while also managing the company. It was not until 2008 that he left the university and fully invested in the operation of the company. The company received Series A and Series B financing in 2010 and 2011 respectively, and then fell silent for several years. It was not until the launch of mature silicon negative electrode battery materials in 2017 that Enevate company once again entered the public's vision and began to obtain new investments. In February 2021, the company received its largest ever investment of $81 million, including joint ventures between Nissan and Mitsubishi, LG Chemical, Samsung, Lenovo, and others, once again attracting the attention of the lithium-ion battery industry.

Enevate's latest silicon negative electrode is the fourth generation product. According to its CTO in an interview, the silicon content in this generation of negative electrode materials exceeds 70%, and the energy density of the entire battery can reach 340Wh/kg or 800 Wh/L, and it can operate stably for more than 1000 charge discharge cycles. Due to the fact that its negative electrode energy storage material is mainly silicon, its charging and discharging speed is much faster than that of graphite negative electrode batteries. In the laboratory, it can reach 75% full charge in 5 minutes, which is expected to solve the problem of fast charging for electric vehicles. The new round of financing will be used to establish a production line, which is expected to start production in 2024. Its battery materials are expected to be equipped with electric vehicle batteries from the cooperating company starting in 2025.

Enevate briefly introduced some characteristics of its silicon negative electrode material on the company website. As shown in the figure below, its production process can directly coat porous silicon containing materials with a thickness of 10-60 microns on both sides of conductive copper foil, without using polymer adhesives at all - this is quite unexpected because the volume expansion and contraction of silicon materials during charge and discharge usually cause the loss of physical connection between particles, thereby losing conductivity. Polymer adhesives are a commonly used method to solve this problem. The company did not provide too much explanation for this characteristic, which also raises doubts about the long-term stability of its batteries.

CTO mentioned in an interview that another characteristic of its silicon negative electrode is that although silicon only accounts for 70% of the negative electrode material, battery design allows the energy of the negative electrode to be stored only in the silicon material, while the remaining 30% carbon material does not participate in energy storage at all and only provides physical support. This is because the charging voltage of silicon is lower than that of carbon, so lithium ions will be preferentially stored in the silicon material during charging until the storage of silicon reaches its limit before starting to store in the carbon material. Enevate designs the energy storage capacity of the negative electrode material to be much larger than that of the positive electrode. When the energy storage capacity of the positive electrode reaches its upper limit, the energy storage in the negative electrode is not even fully filled with silicon. This not only ensures that lithium ions only enter the silicon material, but also avoids permanent damage caused by excessive expansion rate of silicon particles.

Due to the lack of sufficient description on the company's website regarding its silicon containing porous structural materials, we analyzed the patent application of Enevate Company and discovered further information about its silicon containing porous materials. As shown in the production process described in the patent below, Enevate mixes silicon particles with polymer precursors, and then converts the polymer precursor into a pure carbon porous structure support through high-temperature carbonization. The silicon particles are encapsulated and dispersed in the carbon porous structure, allowing for free expansion of the surrounding porous pores without damaging the overall structure of the negative electrode coating.

In another patent, Enevate also mentioned that in order to protect silicon particles from direct contact with the electrolyte, they will also deposit a layer of silicon carbide film and a layer of pure carbon film on the surface of the silicon particles. However, the stability of this protective measure is questionable, as both materials are rigid films and it is difficult to ensure the integrity of expansion when silicon particles expand and contract. So this brings us back to a question at the beginning of this article, whether the long-term stability of this silicon material negative electrode can be guaranteed.

Anyway, Enevate provides a new idea for manufacturing silicon negative electrode materials. As stated by their CTO in an interview, their process does not require the use of high-purity silicon particles, as it can greatly reduce production costs and make all silicon negative electrode materials a technology that can be applied in the field of electric vehicles.

**The article is only for communication, because the official account can not open the message function, if you have questions or suggestions, please send a message to the official account, and we will reply as soon as possible, thank you! Scan the following QR code to follow ZH Energy Storage official account.

Reference:

1. Enevate's official website www.energite.com

2. US Patent 10622620, Methodsof forming composite material films

3. US Patent Application 20200227738, Surfacemodification of silicon particles for electrochemical storage

Related articles:

The energy storage density of silicon is 10 times that of existing lithium battery negative electrode materials, why not replace it?

Sila Nano, which is developing silicon negative electrode materials, has received a financing of $590 million!

Amperes, the first company to implement all silicon negative electrode lithium batteries?

Quantum Scape's Lithium Metal Solid State Battery Rush at the Bottom of Technology

Enoix has just been launched: using photolithography technology to make all silicon negative electrode batteries like making chips

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.

Introduction to ZH Energy Storage Company:

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.

Company's technical research and development direction: water-based energy storage batteries, lithium-ion battery materials, fuel cells, ion exchange membranes, coatings and adhesives, membrane separation technology.

Domestic business: Technical cooperation and academic exchange between liquid flow batteries and high-energy density lithium-ion batteries, technical lectures on the company's technology research and development direction, research and development consulting, and guidance on paper writing.