Graphene's development momentum and resistance in the field of lithium batteries
[Domestic policy assistance: open the curtain of commercialization of graphene]
Graphene is due to its performance in electricity, mechanics, heat conduction and heat dissipation, optics, high specific surface area, etc. The outstanding performance makes it have huge application potential in the fields of electronic information, energy storage, energy saving and environmental protection, aerospace, etc., and has become one of the hot spots of research and development in recent years.
With the development of the industry, the national policy is market-oriented and gradually adjusted, and multi-sectors work together to promote a series of related policies for systematic layout. According to CGIA Research statistics, from 2012 to 2017, the number of relevant policies at the national level reached more than 20, and the number of relevant policies at the local level reached more than 140.
In terms of industrialization, in recent years, there have been many market-oriented graphene products in the country. Among them, the graphene conductive paste manufacturers used in the field of lithium batteries include: : Dongguan Hongna, Qingdao Haoxin, Huagao, etc., the graphene industry has achieved a qualitative leap from 'telling stories' to 'selling products'.
[Technical patent support: Domestic graphene patents are mainly concentrated in the field of lithium-ion batteries]
In recent years, China has Research on graphene application technology continues to grow, mainly focusing on energy storage, electronic devices, water treatment, gas treatment, chemical engineering, medical treatment, testing, aerospace, etc. The number of graphene-related patent applications in the chemical industry, energy storage, and electronic devices ranks among the top three, and the three together account for nearly 90%, becoming the main field of domestic graphene applications.
Graphene patents in the field of energy storage are mainly concentrated in the field of lithium-ion batteries. The number of patents related to lithium-ion batteries is 3,077, occupying more than 40% of the market share. The reason why there is more research and development in the field of lithium-ion batteries is that graphene has excellent electrical conductivity and can alleviate the volume expansion of electrode materials, thereby greatly improving the performance of power batteries. Therefore, graphene is used in the positive, negative, and collector of lithium-ion batteries. Fluids, diaphragms, conductive additives, etc. are widely used, and the future market prospects are particularly broad.
Secondly, the number of patents on supercapacitors is also relatively large, at 1,331, accounting for 17.5%.
[Lithium battery market is improving: China's lithium battery industry has a brighter market prospect]
my country is the most important lithium-ion battery One of the producing countries. In 2014, the output of lithium-ion batteries in my country reached 5.287 billion, accounting for 71.2% of the total global output, ranking first in the world for 10 consecutive years. As of the end of 2018, my country's lithium-ion battery production reached 13.987 billion, more than double the amount in 2014. With the technological innovation of lithium battery manufacturers and the improvement of performance and safety, people's demand for lithium batteries will continue to grow. It is estimated that by 2024, the market size of my country's lithium battery industry will exceed 150 billion yuan.
[Opportunities and difficulties coexist: Graphene is still insufficient in the field of lithium batteries]
Currently, graphene is used in lithium There are three main forms of addition in the battery: conductive additives, electrode composite materials and directly used as negative electrode materials. Among them, the conductivity and discharge performance of graphene conductive additives are far superior to traditional conductive agents. They do not involve complex synthesis processes in the preparation process, so they are more controllable, less difficult, and have a higher success rate. At present, graphene The research and development technology of conductive agent has been relatively mature.
According to data from the Graphene Industry Alliance, the price of graphene conductive agent in 2017 was $230/kg, which is roughly the same as the price of carbon nanotube conductive agent. Graphene is expected to be in 2020 The price of ene conductive agent will drop to US$113/kg, while the price of carbon nanotubes will remain at the level of US$200/kg. The price advantage of graphene conductive agent will gradually appear.
■There are still some problems in the application of graphene in the field of lithium-ion batteries:
1 The layer of graphene in the preparation process Easy to pile up, reducing the theoretical capacity.
2 The first cycle Coulomb efficiency is low, and a large amount of lithium ions cannot be extracted after being inserted, which reduces the activity of the electrolyte and the cathode material.
3 Repeated intercalation and deintercalation of lithium ions make the graphene sheet structure more compact, and the difficulty of intercalation and deintercalation of lithium ions increases, which reduces the cycle capacity.
4 Graphene has a low tap density, which reduces the power density of the battery.
In order to meet the needs of battery cycle life, fast high-current charge and discharge, and high specific capacity in practical applications, it is still necessary to strengthen the following aspects of research:< /p>
For the commercial large-scale production and application of materials, it is necessary to pay attention to the low cost of the preparation process of graphene, and design the preparation process of large-scale production of graphene;
Improve the high rate performance and cycle life of graphene and its composite electrode materials, so that they can meet the needs of practical applications.
In-depth study of the lithium storage mechanism of graphene and the relationship between the microscopic morphology and electrochemical properties in the composite material, and in-depth study of the size structure defects and pore size of graphene And so on the impact on electrochemical performance.
