In Denton, Ohio, USA, there is a company called Global Graphene Group, also known as G3, founded by Taiwanese Chinese professor Zhang Bozeng. Zhang Bozeng went to the United States from Taiwan to study in 1976, and later served as a professor at Wright State University in Denton for many years, focusing on researching the manufacturing and application of graphene. He applied for the world's first patent on graphene composition, production process, and application technology in 2002. In this patent application, Zhang Bozeng clearly explains the preparation process of single atomic layer and multi-layer graphene. This is the world's earliest patent for single-layer graphene, graphene reinforced metal based, resin based, carbon based, and ceramic based composite materials.

He founded AngstronMaterials, the predecessor of G3, in 2007 and began seeking industrial production of graphene. After more than a decade of effort, the market price of graphene has been reduced from a few hundred dollars per gram to several hundred dollars per kilogram, a decrease of over a thousand times. In 2016, his team established a joint venture company in Xiamen - Hengli Shengtai Graphene Technology Co., Ltd., and began mass production of graphene in China. In his decades of research and entrepreneurship, he has applied for more than 580 patents and is recognized as the world's first person in graphene innovation.

In 2016, Zhang Bozeng integrated several graphene companies he founded and collaborated with, and established Global Graphene Group G3 Company, beginning to concentrate advantageous resources for a new round of technological innovation. G3 Company began targeting silicon negative electrode materials for lithium batteries in 2017, utilizing its technological advantages to develop silicon graphene composite materials, and quickly launched two products: silicon graphene composite materials and silicon oxide graphene composite materials.

Silicon graphene composite materials use graphene to encapsulate silicon nanoparticles to form microspheres, as shown in the following figure. The size of microspheres is generally between 3 and 15 microns, and their energy density can reach 2000-2600 mAh/g, with a first cycle efficiency of 88%. The maximum energy density of ordinary graphite negative electrode materials is only 372mAh/g, so their various parameters are very excellent. However, considering the high cost of using pure silicon nanoparticles, they have also launched another silicon oxide graphene composite material.

Silicon oxide graphene composite material uses graphene to encapsulate silicon oxide nanoparticles to form microspheres, as shown in the following figure. The size of microspheres is generally between 3 and 15 microns, and their energy density decreases to 1000-1800 mAh/g, while the first cycle efficiency drops to 74%. Its lower energy density compared to pure silicon composite materials is due to a decrease in the silicon content of the particles, while the low first cycle efficiency is due to the permanent consumption of some lithium ions by silicon oxide, which greatly reduces the first cycle efficiency.

G3 Company has adopted three innovative technologies in the development of silicon graphene composite negative electrode materials. Firstly, there is the unique design of silicon graphene microspheres. This microsphere does not tightly wrap the silicon particles with graphene, but introduces some gaps around the silicon particles, leaving some space for the silicon particles to fully expand when charged, but without damaging the surrounding graphene shell.

The second innovation is the protective shell coating of silicon graphene microspheres, which uses highly elastic polymer materials. Even if the microspheres expand during charging, the polymer coating will not be damaged due to its good elasticity; When the microspheres shrink during discharge, the polymer coating can also shrink along with them. Another function of the coating is to isolate the contact between silicon graphene and the electrolyte. Both silicon and graphene react with the electrolyte during charging, so this coating acts as a protective film for the artificial electrolyte solid interface, maintaining the energy density of the negative electrode without losing too much.

The third innovation is the use of highly elastic conductive polymer adhesives. Under normal circumstances, microsphere particles gradually lose connection with the surrounding ordinary adhesive due to repeated expansion and contraction during charging and discharging, resulting in circuit disconnection. After switching to high elastic polymer adhesives, the polymer will compensate for the gaps formed during microsphere shrinkage, thereby maintaining a close connection with the microspheres and maintaining good conductivity.

Through the above innovative technologies, G3 Company's new negative electrode material can increase the capacity density of lithium batteries to up to 400kW/h in the future. Its single-layer battery has been successfully tested in laboratory environments for over 800 cycles, which can meet the lifespan requirements of power batteries. The company has already established a certain graphene production capacity in Denton City, so with the help of existing facilities, it can quickly transform to produce silicon graphene composite materials. The company currently has a production capacity of 25 tons per year in Denton City, and aims to expand the production capacity to 1000 tons per year in 2021 to meet the rapidly growing material demand for electric vehicle power batteries.

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Reference:

1. The official website of GlobalGraphenegroup.com

two OnDemand Webinar- Si-Anode EV Battery Technology, https://www.theglobalgraphenegroup.com/on-demand-webinar-si-anode-ev-battery-technology/

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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.

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.