Current Status of Chinese Patent Application for Silicon-based Anode Materials for Lithium Ion Batteries

Current Status of Chinese Patent Application for Silicon-based Anode Materials for Lithium Ion Batteries

I. Overview
Lithium-ion secondary batteries are currently the most widely used rechargeable batteries in the industry. Compared with traditional lead-acid batteries and nickel-hydrogen batteries, it not only has the characteristics of high energy density, wide operating temperature range, no memory effect, long storage life, etc., but also has low pollution and meets the requirements of current green environmental protection. Lithium-ion battery anode materials currently used in commercial applications are mainly graphite-based anode materials. However, graphite anode materials have disadvantages of low energy density (375 mAh/g) and safety of lithium deposition during electrochemical processes. Therefore, in recent years, the industry has conducted extensive research on anode materials with low cost, high safety performance, high energy density and long cycle life [1-3].
Compared with conventional anode materials, silicon anode materials have higher energy density and lower electrochemical potential. The theoretical capacity of the silicon negative electrode material is 4 200 mAh/g, which is 2 to 10 times that of the graphite negative electrode material and 4 to 20 times that of the spinel structure lithium titanate (Li4Ti5O12) material. Considering the volume effect of the silicon-containing lithium compound during charge and discharge, the energy density of the silicon negative electrode material is still 2 to 5 times that of graphite and lithium titanate. However, the biggest problem in the application of silicon anode materials is that there is a large volume change with lithium-silicon/desilicon, resulting in severe cracking and bulging of the electrodes, which in turn causes electrical contact between the electrode particles, so that the battery has a large irreversible capacity and Severe capacity attenuation [1]. In order to solve the above problems, a considerable number of patent layouts have been made for lithium-ion battery silicon-based anode materials in domestic and foreign patent applications.
This paper takes the patent application of lithium-ion battery silicon-based anode material in China as an analytical sample. Based on the analysis and summary of the status quo of Chinese patent application in this field, this paper puts forward the development direction and trend of silicon-based anode material for lithium-ion battery in China. Suggest.
Second, the analysis of patent status
The research object of this paper is silicon (Si) based anode material is a lithium ion battery anode material containing Si element, specifically including Si particle material (Si nanoparticle, porous Si, etc.), Si Thin film material, Si-carbon (C) material, Si-M alloy material (M represents metal or non-metal element such as tin or antimony), silicon oxide, other silicon materials (materials other than the above five materials), and the following silicon negative electrode The materials are all defined by this.

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The search uses keywords combined with classification numbers. Due to the large number of documents after retrieval, a total of 883 Chinese patent applications involving Si-based anode materials were obtained after manual noise reduction screening (the search termination date is 2016 5) On the 27th of the month, a statistical analysis was conducted.
1. Time distribution of patent application quantity
Figure 1 shows the time distribution of lithium-ion battery silicon-based anode material in Chinese patent application. It can be seen that the patent application for lithium-ion battery silicon-based anode material begins. In 1997, and between 1997 and 2002, the patent application for silicon-based anode materials was in the nascent stage of technology, and the number of related patent applications has remained at a low level with little change; while the lithium-ion battery silicon-based anode material field The number of patent applications has been growing since 2003 and 2007. Although there has been a certain reduction in 2008, it has shown a rapid growth rate from 2009 to 2013, up from 159 in 2013. Since 2014, due to the procedure of the patent application, the patent data has not been fully disclosed, resulting in a small amount of data. Since the carbon anode material currently used for commercial applications is limited by the energy density, it can be expected that the research and application amount of the silicon anode material will remain at a high level for a long period of time.
2. Regional Distribution of Patent Applications

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Figure 2 shows the comparison of the number of applications between domestic applicants and foreign applicants in the Chinese patent application for silicon-based anode materials during 1997-2016. It can be seen from Figure 2 that in China, the field of silicon anode materials is mainly foreign applicants (57%), and the number of domestic applicants is less than that of foreign applicants, indicating that Chinese applicants are still relatively weak in this field. status.
The above-mentioned patent analysis samples are counted according to the country/province of the patent application, and the results are shown in Table 1. It can be seen from the above that: among foreign applicants, most of the patent applications for silicon-based anode materials come from Japan and South Korea accounted for 42% and 11.5% of China's patent applications, respectively, highlighting the dominance of Japan and South Korea in the field of silicon-based anode materials, and also indicating that these two countries are the most advanced and active in silicon-based anode materials research. country. Among the domestic applicants, Guangdong, Zhejiang, Jiangsu, Beijing, and Shanghai ranked among the top five applicants. These provinces are economically developed regions, and the production companies and research institutions for lithium-ion batteries are also concentrated. There are also quite a few.
3. Main Applicant Composition
Figure 3 shows the ranking of patent applicants for silicon-based anode materials in China, which macroscopically reflects the number of applications for the top 10 major applicants in China. As can be seen from Figure 4, the top 6 domestic applicants in the field of silicon-based anode materials are Japanese and Korean companies, South Korea's Samsung Group has 58 monopolies, followed by Japan's Matsushita Electric and Sony Corporation with 55 pieces respectively. It shows the great advantages and control of Japanese and Korean companies in this field. Compared with this, only China's domestic applicants are listed by Shenzhen Beitray New Energy Materials Co., Ltd., BYD Co., Chery Automobile Co., Ltd. and Shanghai Jiaotong University, but the gap between the number of applications and the previous few Larger. Due to the widespread use of electric bicycles in China and the rapid development of new energy industries such as electric vehicles in recent years, Chinese companies and university research institutions have increased research and development in this field and applied for a certain number of patents, but in general Compared with the number of foreign applicants in China, the number of patents differs greatly, and it is urgent to increase the quantity and quality of patent applications.

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4. Technology branch analysis
Figure 4 shows the main patent technology research and development direction in the field of silicon anode materials. It can be seen from Figure 5 that in China, the main technical direction of patent applications in the field of silicon anode materials since 1997 is Si-C composite materials, Si alloy materials, Si particles, silicon oxide, etc., among which the first three digits account for The total application volume is 32%, 24% and 22%; the Si-containing film is relatively less than the application amount, which may be due to the fact that the Si-containing film material is mostly prepared by the gas phase method, and the cost is high, which is limited in practical applications.
From the trend of application volume in various technical directions (Fig. 5), Si alloy material is the first Si-containing anode material (1997). Before 2007, it has been the application amount in all technical directions. The highest, until 2008, was exceeded by Si particles; in addition, after 2010, the application volume of Si-C composites increased rapidly, and in 2012 became the largest technical direction of application, indicating the applicant's technical direction. The highest level of attention was paid; silica was first applied in 1999, and although the number of applications per year was not very high, it has always attracted applicants to have a stable technical layout in this direction. The rest of the technical direction appeared later, and the number of applications was relatively low.
Since Si-C composites have the highest total application volume in all technical directions, the technical direction of Si-C composites is analyzed in detail. The results are shown in Fig. 6. It can be seen from Fig. 7 that the technical direction of preparing Si-pyrolysis carbon by pyrolysis of carbonaceous materials is the most applied in all Si-C composite materials, and it also indicates that this direction is the current research focus; The cost is low, and the Si-graphite material which is composed of Si material and the graphite material of the traditional lithium ion battery anode material is also a research hotspot. This direction has a large price advantage; graphene is a research hotspot in recent years, with a large ratio Surface area, good electrical conductivity and thermal conductivity are potential energy storage materials for lithium ion battery applications, and the application amount of Si-graphene is also high. At the same time, as can be seen from Figure 7, Si-MC (M is metal or non-metal) and SiSiOx-C, which are compounded by various techniques, is also a research hotspot. In recent years, the application rate has increased rapidly, and it is very likely Be the focus of the future layout.
China's silicon anode materials research started late, with the increasing number of patent applications in the field The number of domestic applications is still far behind Japan and South Korea. At present, most enterprises in China pay more attention to production and sales links to obtain economic benefits, and insufficient investment in scientific research and development; while research institutes and colleges and universities face the problem of transforming scientific research results to further accumulate research funds. Therefore, it is urgent to strengthen exchanges, cooperation and joint research and development between domestic enterprises, research institutes and universities. In addition, the newly emerging technology direction with fewer foreign companies should follow up and expand the layout in a timely manner. Finally, domestic enterprises should not only pay attention to domestic patent applications, but also should effectively distribute patents in key countries or regions. Prepare for the future of silicon-based anode materials and corresponding lithium-ion batteries.
References
[1] Zhang Weijun.A review of the Electrochemical performance of alloy anodes for lithium-ion batteries [J].Journal of Power Sources,2011,196(1):13-24.\u003cbr \u003e [2] Ji Liwen, Lin Zhan, Alcoutlabi M, et al. Recent developments in nanostructured anode materials for rechargeable lithium-ion batteries [J]. Energy \u0026 Environmental Science, 2011, 4: 2682-2699.
[3] LEI Cheng-cheng,SHI Lei,WU Fei.Research Progress in Anode Materials for Lithium Ion Batteries[J].,2011,31(6):10-13.

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