In the company that develops silicon negative electrode materials, Amperes is a pioneer and currently a leader in the industry. The founder of the company is Chinese professor Cui Yi from Stanford University in the United States. His research team published a research article on the use of silicon nanowires as negative electrode materials for lithium batteries in the Nature journal in 2008, which has been cited more than 6000 times so far. In the same year, he founded Amperes, preparing to commercialize silicon nanowire negative electrode materials.

In the era of 2008, while other researchers were still studying silicon nanoparticles, Professor Cui Yi had already seen the limitations of nanoparticles - repeated expansion and contraction would eventually lead to particle rupture, so he proposed the concept of silicon nanowires. As shown in the figure below, silicon nanowires are grown on conductive metal foils like mushrooms, and when charged, they absorb lithium ions, which become thicker and longer. Due to its small diameter (such as 89 nanometers), even if all lithium ions are absorbed, it will only increase to 141 nanometers, and the expansion ratio is much smaller than that of nanoparticles, so its cycling charging stability is much higher than that of silicon nanoparticles. At the same time, because silicon nanowires grow directly from conductive metal foil, their connection is very stable and will not detach from the metal foil after multiple charges and discharges, thus maintaining good conductivity. Using such a silicon nanowire negative electrode, Professor Cui's research team successfully measured the actual energy storage density of silicon materials to be 4277 milliampere hours per gram, which is basically consistent with the theoretical speculation of silicon energy storage density (4200 milliampere hours per gram).

In the years following its establishment, Amperes devoted itself to research and development. In 2016, it established a factory in Wuxi, China to produce lithium batteries with silicon negative electrodes, which had an energy density exceeding 10% of the same type of graphite negative electrode batteries at that time. They were mainly supplied to mobile devices such as mobile phones. Although Amperes' US official website has already claimed that it can produce negative electrode batteries containing 100% silicon materials, based on this performance, it can be inferred that batteries produced in China at that time may not have fully achieved 100% silicon negative electrode materials and are still silicon carbon composite materials.

In the same year, Amperes USA announced the completion of the validation work for the rapid production line. They use a roll to roll assembly line to integrate multiple production steps, and directly grow three-dimensional silicon nanowire negative electrode materials on copper foil through chemical vapor precipitation. According to a microscope photo released on the company's official website, this process can grow silicon nanowires on both sides of a copper foil, with a very balanced morphology, indicating that the process control of the precipitation method has been done very well. According to the official website, the thickness of the silicon nanowire negative electrode produced by this process is only about half of that of graphite negative electrodes of the same type, and it has both micro pores and macro pores. Macro pores can be understood as the space between different nanowires, while micro pores may refer to the hollow structure inside a single nanowire, thus avoiding the damage to stability caused by excessive expansion of the nanowire.

In 2018, Airbus developed the high-altitude solar powered drone "Hefeng" using Amperes' all silicon negative electrode battery, which can fly continuously at an altitude of over 20000 meters for more than 25 days in one flight, setting a new record for the endurance time of solar powered drones. The "Hefeng" drone uses solar energy to power its two propeller engines, allowing it to operate entirely on solar energy during the day. At night, it relies on the energy stored in onboard batteries during the day to continue flying. Due to the use of all silicon negative electrode batteries with higher energy density, their battery life has more than doubled compared to the previous highest of 11 days.

From the comparison chart provided by Amperes, it can be seen that there is a significant difference in energy density among different battery systems. And batteries containing all silicon negative electrodes are superior to other types of batteries in terms of weight energy density and volume energy density, reaching 435 Wh/kg or 1200 Wh/L or above. The advantage of its volumetric energy density is particularly evident, almost double that of the second highest battery type.

Amperes has been established for 13 years and has raised a total of 160 million US dollars. It has not yet gone public. With the gradual maturity of its all silicon negative electrode assembly line technology, it is expected that corresponding products will also be quickly launched to occupy the market. Just before Tesla held its first Battery Day in September 2020, there were rumors that Tesla was likely to acquire Amperes and announce it on Battery Day. This speculation is based on the following two clues:

1. Amperes moved across the street from Tesla's factory. As shown in the satellite image below.

On Tesla's first battery day promotional website, the background image seems to be an electron scanning electron microscope image of a silicon nanowire.

However, Tesla did not mention the negative electrode material of silicon nanowires or any content related to Amperes on Battery Day, leaving the general public confused. However, such speculation also indirectly confirms everyone's optimism about the negative electrode of silicon nanowires and their expectations for the future of Amperes.

**The article is for communication, because the official account cannot 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. Amperes official website https://www.amprius.com/

2. High performance lithium battery anodes using silicon nanowires, Nature Nanotechnology 3, 31-35 (2008)

three Tesla& Amprius — What Is Going On? https://cleantechnica.com/2020/08/26/tesla-amprius-what-is-going-on/

Related articles:

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

The energy storage density of silicon is 10 times that of existing lithium battery negative electrode materials, why not replace it?
How can silicon materials with 10 times energy density be used as negative electrodes in batteries?

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, academic exchange, technical lectures on company technology research and development, research and development consulting, and guidance on paper writing.