Graphene is a two-dimensional carbon material which is peeled off from a graphite material and can be classified into single-layer graphene, multilayer graphene, and graphene microchip according to the number of carbon atom layers. The single-layer graphene refers to a strictly single-layer carbon material in which carbon atoms are arranged in a hexagonal honeycomb structure only in a two-dimensional plane, and is a semiconductor having a linear energy distribution without an energy gap, which is imparted by the electrons being freely movable in the crystal. Single layer graphene has very good electrical conductivity.

Type of graphene

Graphene single-layer carbon structure

In terms of mechanics, graphene is the strongest and highest known substance in humans, and its Young's modulus is 1Tpa, which is equivalent to single-walled carbon nanotubes. The strength is about 180 GPa, which is 100 times that of ordinary steel. In addition, graphene also has good toughness. Graphene sheets per unit area can withstand 4kg weight, and its toughness is equivalent to 20 times that of carbon fiber. In terms of thermal conductivity, graphene itself has a thermal conductivity of 5300W/moK, which is the best at room temperature. The thermal conductive material has a thermal conductivity of 1.51 times that of carbon nanotubes and 13 times that of copper. In terms of electricity, graphene is the best conductive material at room temperature. Due to its special band structure, electronic motion interference at room temperature is small. The transmission quality has been greatly improved. The electrical properties of graphene are highlighted by high carrier mobility and high current density, and the carrier mobility is 15000 cm 2 /Vos, which is 10 times that of commercial silicon wafers. The current density tolerance is 200 million A/cm2, which is equivalent to 100 times that of copper.

Special properties of graphene

In addition to excellent thermal, mechanical and electrical properties, graphene also has several special functions such as low temperature hydrogen absorption, normal temperature without scattering, strain sensing, etc., which makes graphene can be used to make hydrogen absorbing materials and non-scattering transmission devices. , strain sensors, bipolar semiconductors and catalysts. Comprehensive analysis of various excellent properties and characteristics of graphene, graphene will be widely used in the future, and mainly concentrated in the electronics industry and the chemical industry, especially in the lithium battery electrodes, touch screen, super capacitor field and chemical industry in the electronics industry. The industry's coating, insurance, adsorption, desalination areas.

Graphene application field

Unique use of graphene

Among the number of major priority patent applications in the world, the number of applications from China, South Korea and the United States ranked the top three, which were 6714, 2892 and 2632 respectively. The research and development of graphene is mainly concentrated in Asia and North America. China is a major R&D country, and the earliest priority patent applications account for about 50% of the world. Among the top ten graphene patent applicants in the world, five are Chinese universities, two are Korean universities, and only three are enterprises, and colleges and universities account for 70%. It can be seen that the main research and development of graphene is still in colleges and universities. In terms of the number of patents, the applicants with the largest number of patent applications are South Korea's Samsung, Korea High-Tech Institute and IBM, and the number of patent applications is 503, 223, and 199, respectively. It can be seen that the leading organizations of global graphene R&D technology are mainly distributed in South Korea.

Global graphene first priority patent application number distribution

The top ten graphene patent applicants in the world

Currently in the development of graphene focuses on high-end optoelectronic components. Taking the EU as an example, the European Union has drawn up a blueprint for graphene development in the next 20 years. In the near future, it will intensify efforts to develop optoelectronic components such as touch screens, electronic paper, folded OLEDs, and fiber lasers. After 2020, graphene research and development will move toward high-end optoelectronic components, mainly for transistors and optical generators, regulators and so on. At present, the research on the preparation process of graphene and the downstream application are the main development directions. The recent major achievements mainly focus on the preparation of graphene, wearable equipment, ink printing, lithium batteries and so on.

Major developments in graphene in 2012-2016

Countries such as the European Union focus on graphene performance mainly in their excellent optoelectronic properties, and have set long-term development goals, which are very optimistic about the future development of graphene. . Graphene has different key application areas in different stages of industrialization. The first stage is mainly the industrialization of low-end graphene materials. At this time, graphene preparation technology is becoming more and more mature, the downstream demand of graphene is gradually opening, the mass production of graphene and the replacement process of graphene materials for traditional materials are accelerating. From 15 years to now, the first single-layer graphene mass production base in China has settled in Xiamen. The advent of graphene electronic paper, flexible screens and graphene mobile phones all indicate that China's graphene has initially entered the stage of industrialization. With the opening of the downstream application market and the maturity of high-end graphene materials research technology, the characteristics of graphene as a high-quality material will be more fully explored, and industrialization will gradually enter the second stage. There are continuous technological breakthroughs in the preparation and application of graphene, mainly focusing on the preparation and application of graphene films. According to the development prospects of graphene, the development of graphene is mainly limited by the high cost and the price of substitutes is low. However, with the deepening of research, graphene is still the target of future development and application.

In the UK, a total of £100 million was invested in the establishment of graphene research and development institutions in 2014-2015; the US government invested US$28 million in further research on graphene in 2014, and the international giant graphene giant IBM is expected to invest 3 billion in the next five years. The US dollar researches graphene-related chip technology; the EU has raised graphene research to a strategic height, and plans to invest 1 billion euros in funding by 2023; South Korea is expected to invest about 300 million US dollars in graphene research and development in 2012-2018. Industrialization; Japan’s Ministry of Economy, Trade and Industry has invested 900 million yen to focus on the synthesis of carbon nanotubes and graphene.

The recent layout of graphene in the EU and countries

China has incorporated graphene into the new materials encouraged by the “12th Five-Year Development Plan for New Materials Industry”, while “Made in China 2025” further clarifies the development path of China's graphene industry in the next decade. The overall goal is to form in 2020. The scale of 10 billion yuan has exceeded 100 billion in 2025. The focus is on the scale of graphene production and the industrialization of energy storage electrochemical devices.

The overall layout of 2025 graphene materials made in China

At present, the preparation of the 13th Five-Year Plan for new materials has basically ended. Public information shows that the frontier new materials field will focus on the development of four categories of 14 categories of materials such as graphene, 3D printing, superconductivity and intelligent bionics, and form a batch of potential market scales ranging from 10 billion to 100 billion. industry. The 13th Five-Year Plan for new materials will lead to a large market of trillions of scales. Graphene is a cutting-edge material with excellent performance, and its industrialization will usher in a historic opportunity of leap-forward development.

Global Patent graphene most concentrated prior art are five sub-cell lithium, biochemical sensor, a supercapacitor, a catalyst and a conductive composite material. The number of patents for lithium-ion battery applications is the highest, at 646, accounting for 12.7% of all patents in all fields. It can be seen that the application research of graphene is the most mature in the field of lithium batteries , and the technical difficulty in industrialization promotion is the lowest.

Ten areas where graphene patents are most concentrated

According to the downstream demand situation, application advantages and major obstacles of graphene in the field of electronics, it can be concluded that graphene will first be industrialized in the field of lithium battery electrode additives. Since the research and development technology of graphite lithium battery electrode additive is relatively mature, and the mass production difficulty is mainly due to the uniformity of graphene distribution in the composite material, it has advantages in synthesis control and cost, and thus the industrialization time is more than other electronic fields. early. Secondly, for the thermal film and touch screen, due to the mature R&D technology, the industrialization is expected to be 1-2 years ahead of the flexible conductive film and super capacitor.

The industrialization status of graphene in the field of electronics

From the perspective of the industrial chain, the scaly graphite ore is processed into a graphene product after initial processing and deep processing. The addition forms of graphene in lithium batteries mainly include conductive additives, electrode composite materials and direct use as negative electrode materials. Lithium batteries after the addition of graphene are mainly used in downstream areas such as smartphones, notebook computers, mobile power and wearable devices, electric vehicles and industrial energy storage.

Graphene-lithium battery industry chain

The global power lithium battery market is gradually expanding. In 2012, the power lithium battery market is about 30 billion yuan. It is expected to maintain an average annual growth rate of about 30%. By 2020, the global power lithium battery market will reach 210 billion yuan for 2012. 7 times. At the same time, power lithium battery manufacturers in various countries have expanded their production capacity. Taking China as an example, in 2017, the domestic expansion capacity is expected to be about 15.2Gwh, while the domestic power lithium battery capacity in 15 years is 18.97Gwh, and the capacity expansion is nearly 80%.

Global Power Lithium Battery Market Size and Forecast 2012-2020

New capacity of domestic major power lithium battery manufacturers in 2016

The global portable lithium battery market has grown year by year since 2012 and is expected to maintain an average annual growth rate of approximately 10% by 2020. Where the demand for lithium batteries in mobile phones, tablet PCs and notebook regard will maintain an annual average growth rate of 8% is expected by 2017 portable lithium battery in mobile phones, tablet PCs and notebook terms demand reached 45,000MWh.

2012-2020 global portable lithium battery market size forecast

Demand for portable lithium batteries for mobile phones, tablets and notebooks in 2013-2017

At present, the domestic manufacturers of graphene are mainly Qingdao Xinxin, Dongguan Hongna New Materials, Beijing Moten, Deyangene Carbon, Jining Lite and Sixth Element, with the expansion of domestic lithium battery downstream capacity, and production technology. Progress, manufacturers' research and development power is full, and the development prospects are expected.

The graphene conductive agent can be classified into a water slurry, an NMP slurry, and a powder-based conductive agent according to the type of the solvent. In the aqueous slurry and the NMP slurry type conductive agent, the graphene content is generally 5.0 ± 0.1% by weight, and the dispersant content is 0 - 0.5 wt%. Powder graphene conductive agent, need to add water or NMP and dispersant, formulated into water slurry and NMP pulp

The material type conductive agent can be added to the positive and negative electrodes of the lithium battery.

Compared with traditional conductive agents, graphene is mainly contacted by “face-to-point”. Due to its extremely thin particle size and freely moving electrons in the crystal phase, the conductivity of graphene reaches 1000 S/cm, which is conductive carbon. 100 times black. In the range of 1-6 wt% of the conductive additive, the resistivity of the graphene conductive agent is only 1/40-60 of the same concentration of conductive carbon black, and is only about 1/10 of the carbon nanotubes of the same concentration. Regarding the discharge performance, at 10C and the battery capacity is 0-133 mAhog-1, the discharge voltage of graphene is significantly higher than that of conductive carbon black, and it can be seen that the electrical properties of graphene are far superior to those of conventional conductive agents.

Effect of different addition amounts on electrode resistivity (Ω*cm)

Graphene and conductive carbon black discharge rate curve at 10C

Graphene conductive agent compared with traditional conductive agent

The current methods for preparing graphene mainly include micro-mechanical glass method, vapor deposition method, epitaxial growth method and graphite oxide reduction method. The key factor in determining mass production is the size of the product, followed by manufacturing costs and product quality. Both the graphite oxide reduction method and the vapor deposition method can produce large-sized graphene. Although the former is easy to cause the molecular structure of the graphene to be destroyed, it has a cost advantage, and the latter has a quality advantage despite the high cost. The maturity of the method for preparing graphene provides a prerequisite for industrialization. The Chinese government has also clearly stated in "Made in China 2025" that it will realize the large-scale production of graphene raw materials in 2020. It is expected that with the support of the government and the improvement of production technology, the industrialization of graphene raw materials will accelerate, and graphene conductive agents will be rapidly popularized in the downstream market under the condition of sufficient supply of graphene raw materials.

Comparison of four graphene preparation methods

According to Graphenea, the current cost of producing single-layer graphene by CVD is about 7 Euro/cm2. In the next few years, as the graphene production process matures, the production cost will be further reduced. It is estimated that the cost of producing single-layer graphite by CVD will be reduced to 0.07 Euro/cm2 by 2020. The sharp reduction in the production price of graphene will cause graphene conductive agents to break through the cost bottleneck and thus occupy the downstream market at a more reasonable price.

According to statistics from the Graphene Industry Alliance, the price of graphene conductive agent in 2015 was US$230/kg, which is about the same as the price of carbon nanotube conductive agent. However, the price of graphene conductive agent will fall much faster than the price of carbon nanotube conductive agent. It is expected that the price of graphene conductive agent will drop to US$113/kg by 2020, and the price of carbon nanotubes will remain at 200. At the dollar/kg level, the price advantage of graphene conductive agents has gradually become prominent.

Expected price changes for various types of conductive agents (US$/kg)

Graphene composite electrode materials can be mainly divided into positive electrode composite materials and negative electrode composite materials. Compared with pure electrode materials, the electrode cycle performance can be greatly improved, the transfer resistance can be reduced, and the conductivity of the electrode can be significantly improved.

Types and advantages of graphene composite electrode materials in lithium batteries

At present, there are about 124 patents related to graphene composite electrodes in China, including 51 patents in 2014, and the number of patents is the largest in calendar years. Graphene electrode composite material wherein a lithium battery is about 14, the main use of the negative electrode. Among the patent applicants, only 35% of the enterprises are involved. It can be seen that the research and development of the graphene composite materials for lithium batteries is still a research institution, but many companies have also invested in research. Since graphene is relatively mature in lithium battery composite electrode materials, considering the control factors of synthetic process, it is expected that the industrialization time will be 1-2 years later than graphene conductive agent.

Number of domestic graphene composite electrode materials patents from 2009 to 2015

Patent distribution of domestic lithium battery graphene electrode composite materials

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