In the previous article, we introduced the Global Graphene Group, also known as G3, located in Denton, Ohio, USA. It was founded by Taiwanese Chinese professor Zhang Bozeng. The company started with the research and development of graphene and has shifted to the production of silicon negative electrode materials in recent years. At the same time, Zhang Bozeng has also started to focus on the research and development of solid-state metal lithium batteries and has applied for 38 related patents in this area. In this article, we will take you through some innovations of G3 Company in the research and development of solid-state metal lithium batteries.

Although we have previously introduced the technological challenges of solid-state lithium metal batteries in an article titled "Quantum Scape's Lithium Metal Solid State Battery Wave at the Bottom of the Technology", here we briefly explain the several major challenges currently faced by solid-state lithium metal batteries:

1. Lithium metal will react with liquid electrolytes, causing a rapid decrease in battery capacity;

2. During charging, lithium metal deposits onto the negative electrode conductive foil. Due to uneven current distribution, local deposition may be too fast, resulting in the formation of sharp lithium dendrites, as shown in the following figure. Lithium dendrites can puncture the polymer separator, causing a short circuit in the battery and resulting in failure.

3. Similarly, due to rapid local deposition, some protruding lithium metal ends will separate from large metal blocks, becoming isolated lithium particles, losing connection with the negative electrode conductive foil, losing conductivity, and becoming useless free metal particles, gradually reducing the battery capacity.

4. The lithium metal block in the negative electrode continuously generates and dissolves, causing deformation in the negative electrode space. The metal block gradually loses its tight connection with the conductive metal foil, and the conductivity gradually weakens, resulting in lower energy efficiency.

In response to the above issues, G3 Company has proposed the following solutions in their solid-state lithium metal battery patents:

1. Add a graphene protective layer on the negative electrode metal conductive foil to limit the generation and growth of crystal branches;

2. Graphene protective layer, due to its good ductility, can also function as a tight connection between lithium metal and solid electrolyte;

3. Use a conductive polymer protective layer with good elasticity to prevent contact between lithium metal and liquid electrolyte.

Let's analyze these innovative solutions of G3 company from a specific technical perspective. Firstly, there is a graphene protective layer. Graphene, due to its unique thin layer structure, can easily form a porous structure similar to a "house of cards" as shown in the figure below. These gaps provide a predetermined space for the deposition of metallic lithium, and the strong support strength of graphene ensures that the negative electrode material is not crushed during assembly. This porous structure effectively solves the spatial variation problem of metal lithium batteries during charge discharge cycles, and can prevent separation and circuit breaking between different material layers of the negative electrode.

Meanwhile, due to the excellent conductivity of graphene, it can avoid excessive local current generated by lithium metal growing on its surface, thereby avoiding the generation and expansion of lithium dendrites. If the generation of lithium dendrites can be successfully avoided, traditional polymer separators can continue to be used, which not only greatly saves costs but also improves the performance of the battery.

The second innovative direction of G3 company is to use conductive polymer protective layers with high elasticity. This polymer layer will be placed between the lithium metal and the separator, with the main purpose of utilizing its high elasticity to compensate for the spatial changes during discharge. This innovation has been used by many companies in the design of silicon negative electrodes, so it is not surprising that it can help improve the cycle life of lithium metal batteries.

The third innovative direction is to add transition metal particles to the porous structure of graphene, as some transition metals can reduce the chemical energy of lithium metal deposition on the surface of graphene, acting like catalysts. This can reduce the probability of lithium metal depositing on existing metal blocks and increase the probability of lithium metal depositing on the surface of graphene that has not yet been covered. In short, it can effectively avoid local concentrated deposition, make the deposition layer of lithium metal smoother, and thus reduce the generation of lithium crystal branches.

The fourth innovation direction is to artificially synthesize electrolyte solid interface facial mask on the surface of graphene to protect lithium metal from contact with liquid electrolyte. This measure has also been widely applied in silicon negative electrode materials, so it will not be repeated.

The final innovative direction is to add silicon lithium alloys that have been combined with lithium metals into the porous structure of graphene. This method sounds more inclined towards a solution for silicon negative electrode materials, and has little relevance to solid-state lithium metal batteries, after all, lithium exists in the form of silicon lithium alloys at the negative electrode, rather than simply lithium metal.

In summary, among the innovation directions proposed by G3 Company, the first three are closely related to solid-state lithium metal batteries, and from a theoretical perspective, they also have good rationality. At the level of technological implementation, these directions all pose great challenges. How to better and faster implement these measures will be the goal of efforts in the field of solid-state lithium metal batteries in the coming years.

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Reference:

1. The official website of GlobalGraphenegroup.com

two OnDemand Webinar- The Path Forward for Solid-State EV Batteries, https://www.theglobalgraphenegroup.com/ondemand-webinar-the-path-forward-for-solid-state-ev-batteries/

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How to integrate the best two types of negative electrode materials for lithium batteries using silicon graphene as the negative electrode

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

How can silicon materials with 10 times energy density be used as negative electrodes in batteries?

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

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.