In the past 20 years, China's lithium-ion battery technology and industry have made great progress. The lithium-ion battery material system has developed from lithium cobalt oxide to lithium iron phosphate, ternary materials, and then to high-nickel and manganese-rich systems. The negative electrode has evolved from graphite to polycarbonate. materials, and then developed to lithium-containing alloys and even lithium metal. At the same time, manufacturing technology has developed from workshop-style production to automation and today's intelligence, and the scale of the industry continues to expand. China has become the world's largest producer and consumer of lithium-ion batteries. Looking to the future, the technology development trend is high specific energy, high specific power, high safety, long life, and low cost. All-solid-state batteries, new principle light metal batteries, and customized products will achieve technological breakthroughs. The industry will be intelligent and unmanned, scaled and alliance-based, and segmented and specialized.

　　Source of this article: Power Technology Magazine WeChat ID: dianyuanjishu Author: Liu Xingjiang

　　1. The origin of lithium-ion batteries and the industrialization of lithium batteries in China

　　Lithium-ion batteries work by inserting/extracting lithium ions into and out of the positive and negative electrodes and moving between the positive and negative electrodes to achieve the charge and discharge process. The principle is simple and there is no electrolyte consumption. Therefore, lithium-ion batteries are ideal high specific energy battery systems. The world's first industrialized lithium-ion battery was a lithium cobalt oxide positive electrode invented by Goodenough, a coke negative electrode combination proposed by A. Yoshino, and a mixed solvent electrolyte of propylene carbonate and diethyl carbonate of LiPF6. SONY introduced it in 1992 Achieve mass production, battery specific energy is 80Wh/kg.

　　2. Development of lithium-ion battery technology in China

　　2.1 Research on cathode materials

　　The earliest practical cathode material is layered lithium cobalt oxide (LCO) material, with a charging cut-off voltage of 4.2V and an operating voltage of 3.7V. It is mainly used in consumer electronics. After surface coating and doping, high-voltage lithium cobalt oxide materials can now be charged to 4.45V and operate stably, with a specific capacity of more than 180mAh/g. A common way to increase the charging voltage of LCO is to coat the surface of LCO particles with a layer of Al2O3, TiO2, ZrO2, etc. to prevent LCO from direct contact with the electrolyte. Later, in order to reduce costs and improve safety, the layered ternary materials Li(NiCoMn)O2 (NCM) and spinel lithium manganate LiMn2O4 attracted widespread attention and began to be mixed with lithium cobalt oxide for consumer electronics or used alone. On motivation. Nowadays, ternary materials are developing from Ni:Co:Mn ratio 1:1:1 to high nickel 532, 622, and 811. With the increase of nickel content, the specific capacity increases from 150mAh/g to 200mAh/g, but the production process environment The requirements are getting higher and higher, and battery safety is getting lower and lower. At the same time, domestic manufacturers using NCM materials patented by 3M are likely to face similar risks of patent disputes during the export process. In recent years, anionic active materials such as layered lithium-rich manganese-based materials have also achieved tremendous theoretical breakthroughs and technological progress, with specific capacities even reaching 400mAh/g. Spinel materials are developing towards Fd3m and P4332 space group miscible 5V spinel LiNi0.5Mn1.5O4. This type of material has a three-dimensional tunnel structure, lithium ions can be completely extracted, has a high diffusion coefficient and is safe. In addition, polyanionic phosphate materials, such as LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4, etc., have an olivine structure and are very stable because the oxygen in the phosphate materials is fixed in the form of strong phosphate groups. The volume changes during charging and discharging are small and safe. Good sex. Particularly worth mentioning is lithium iron phosphate (LiFePO4), which supports half of China's lithium-ion battery materials industry. This material has the advantages of good safety, long cycle life, and low cost. It is the main cathode material for power and energy storage batteries. Through nanonization and surface carbon coating, lithium iron phosphate has achieved the performance of larger power discharge, and the well-carbon-coated samples do not contain γ-Fe2O3 and Fe3+ impurities. This material has achieved the world's largest application in China. Large-scale production. Lithium iron phosphate is facing complex patent disputes, including Goodenough of the University of Texas, Nippon Telegraph & Telephone, and A123, all claiming patent rights to LFP. However, in 2015, with the efforts of industry experts, China claimed the patent rights of Canada's Hydro-Québec. It achieved “invalidation” and protected the domestic lithium iron phosphate material and battery industry. Lithium manganese iron phosphate materials have attracted the attention of the industry due to their high voltage and high specific capacity. Some manufacturers have added this type of material to ternary materials to improve the safety of lithium-ion batteries. Figure 1 shows the specific energy potential of other materials compared to traditional lithium cobalt oxide.

　　Figure 1 Comparison of relative energy densities of various cathode materials

　　2.2. Research on negative electrode materials

　　The rapid rise of graphite materials benefits from technological innovations in electrolytes and graphite materials. Graphite materials can be mainly divided into artificial graphite and natural graphite. China's industrial research on lithium-ion battery anode materials started with artificial graphite. Among them, mesocarbon microsphere (MCMB) material has the advantages of high tap density and low specific surface area, which reduces the formation of SEI film during the first charging process and reduces the irreversible capacity. Therefore, MCMB is widely used. However, its production temperature is as high as 2800°C, so the cost has remained high. Natural graphite is very low in cost, but the co-embedding problem of PC affects the application of natural graphite. Therefore, natural graphite requires an electrolyte with a high EC content or modification of the surface of natural graphite, and surface-modified natural graphite It is the mainstream of the current market. In addition, soft carbon and hard carbon materials have high lithium ion insertion potential, especially hard carbon materials with a layer spacing of 0.372nm, which is easier for lithium ion diffusion. Therefore, soft carbon and hard carbon materials have been used as part of composite anodes for power battery anodes to meet the requirements of fast charging and low-temperature charging. During this period, alloy anode materials also received widespread attention, such as Si and Sn materials, but the huge volume expansion of these materials during the lithium insertion process limited their applications. Now, in pursuit of higher energy density, significant progress has been made in the development of Si-C materials and SiO materials.

　　2.3. Electrolyte research

　　LiPF6's carbonate mixed solvent electrolyte was first used in commercial lithium-ion batteries. With the technological advancement of electrode materials, matching electrolytes are also constantly developing. During the initial charging process, the electrolyte will form a layer of SEI film on the surface of the graphite negative electrode. If the SEI film is not completely inert, the electrolyte will decompose on the surface of the negative electrode in each subsequent cycle, increasing the resistance of the negative electrode and causing consumption. electrolyte, so if the SEI membrane cannot be controlled well, good cycle performance cannot be obtained. In the early days, efforts to improve the performance of the electrolyte were mainly focused on the purification of the solvent (removal of water). Later, the concept of functional electrolyte additives was proposed. Common additives mainly include SEI film-forming additives EC, FEC, etc., as well as resistors. Combustion additives, anti-overcharge additives, wetting additives, etc. Functional additives also drive technological advancements in high-capacity graphite materials. Polyoxyethylene and other polymer electrolytes can only be used above 60°C. In order to solve this problem, a part of the liquid electrolyte can be added to polymers such as PEO, PAN, PMMA, PVdF-HFP, etc. to form a so-called gel electrolyte. Bell The laboratory once launched a battery using PVdF-HFP gel electrolyte. This technology has also attracted widespread attention from the Chinese industry. With the help of this gel electrolyte, we do not need to use a hard shell structure to exert a certain squeezing force on the battery, so we can use a lighter plastic shell (such as aluminum plastic film) to increase the mass specific energy of the lithium-ion battery. .

　　In recent years, in order to further improve the specific energy and safety of lithium batteries, there has been an upsurge in solid-state lithium battery research in China. Its core technologies are highly stable and high conductivity solid electrolyte materials and interface control technology between solid electrolytes and electrode materials. Solid-state lithium batteries work on the same principle as traditional lithium batteries. However, because the key components are all solid, the interface is more complex, and interface compatibility directly affects the performance of solid-state batteries. Solid electrolytes mainly include polymers, oxides and sulfides. The performance comparison of various solid electrolytes is shown in Table 2. At present, Japan, represented by Toyota, uses sulfide solid electrolyte as the main system. The bipolar solid-state battery developed at the same time has an average voltage of 14.4V. It is expected to launch the first electric vehicle equipped with a solid-state battery in 2022. The technical level is internationally Leading; South Korea mainly uses sulfide and inorganic/organic composites. Samsung Yokohama Research Institute has developed a 2Ah sulfide solid-state battery, which can obtain specific energy of 200Wh/kg and 500Wh/L. It is in the small-scale trial stage; France and Canada use PEO Mainly based on polymers, it has small-scale production capabilities; the research focus of Sakti3 (Dyson) and others in the United States is LiPON-based ultra-thin oxide solid-state batteries, but it is currently in the laboratory stage; a hundred flowers are blooming in China, and organic/inorganic composite solid electrolytes are practical It is advancing rapidly, especially Ganfeng Lithium Industry, which is the first in China to prepare soft-package all-solid-state lithium batteries with a capacity of 4~10Ah, with a specific energy of up to 286Wh/kg (628Wh/L), and a thousand-cycle capacity retention rate of 87.6%. Investment 240 million to build the first-generation solid-state lithium battery research and development pilot production line.

　　3. Development and current situation of China’s lithium battery industry

　　China's lithium-ion battery industry technology has gradually moved from tracking research and imitation to independent innovation, and product applications have gradually moved from the initial mobile phones and laptops to power and energy storage applications. After 20 years of development, China has become a major manufacturer and consumer of lithium-ion batteries. It has grown from a few companies to hundreds, with the most complete industrial chain, and its global market share has reached 52%. Figure 2 shows the statistical chart of China's lithium-ion battery production in recent years. In 2017, total production reached 100.9 billion watt-hours, and sales revenue reached 158.9 billion yuan. Figure 3 is a list of China’s top 20 power batteries. Among them, CATL has developed into the world’s largest lithium-ion battery manufacturer. Driven by the electric vehicle subsidy policy, lithium-ion batteries for power have developed rapidly. Cylindrical, square, and polymer battery types coexist, but square accounts for up to 54%, cylindrical accounts for 26%, and polymer accounts for 20%. The material system has developed from 70% lithium iron phosphate system in 2016 to the coexistence of lithium iron phosphate and ternary systems in 2017 (accounting for 49% and 45% respectively). The electrical performance of batteries has also been continuously improved. The specific energy of large-capacity square lithium iron phosphate single cells has exceeded 170Wh/kg, and the specific energy of high-nickel material 21700 batteries has reached 240~280Wh/kg. But in 2018, people have realized the importance of safety from the frequent fire accidents of electric vehicles. The phosphate system has certain advantages in terms of energy and safety, which may affect the layout of phosphate and high-nickel systems in power batteries.

　　And upstream material production is also expanding rapidly. Among them, the ranking of ternary cathode materials is Hunan Shanshan, Xiamen Tungsten Industry, Ningbo Jinhe, Shenzhen Zhenhua, Xinxiang Tianli, Beijing Dangsheng, etc., with a single monthly output of more than 10,000 tons; the ranking of anode materials is Beterui , Shanshan, Jiangxi Zichen, Kaijin, etc. The domestic matching rate of electrolytes and separators has increased rapidly, and there has been a trend of overcapacity.

　　Regarding lithium primary batteries, due to its small overall market size, it is only a market of more than 3 billion yuan, with an annual growth rate of about 15%. At the same time, its chemical system is shown in Table 3 with less changes. There are only a few R&D and production units in China such as Yiwei Lithium Energy, the state-owned 752 Factory, and Wuhan Lixing. The 18th Institute of China Electronics Technology took the lead in developing new system primary batteries such as lithium fluorocarbon with the highest specific energy, with a specific energy of 700Wh/kg, filling a domestic gap.

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