New energy technology is recognized as a high-tech in the 21st century. As an important part of the new energy field, the battery industry has become a new hot spot in the global economic development. At present, lithium-ion batteries have been widely used as an important energy source. Whether in the field of electronic communication or transportation, she plays an extremely important role and has broad application prospects.
Lithium-ion battery is a kind of secondary battery. It is a new type of battery developed on the basis of lithium battery. It mainly relies on lithium ions moving between the positive and negative electrodes to work. Since the 1970s, various high specific energy lithium primary batteries using lithium metal as a negative electrode have been introduced and widely used.
Lithium-ion battery has high operating voltage, high specific energy, large capacity, small self-discharge, good cycle, long service life, light weight and small size. It is a representative of modern high-performance batteries and is a portable electronic device such as mobile phones and notebook computers. The ideal power source is expected to become one of the main power sources for electric vehicles and cordless power tools in the future.
The development history of lithium-ion battery industry in China is not long, but it is developing very fast. In 2012, the total output of ion batteries in China reached 4.18 billion. In the international lithium-ion battery market, China, Japan and South Korea have formed a three-legged situation. The technological development of China's lithium-ion battery industry began with imitating foreign mature technology. In the process, process innovation is the main achievement of the early development of China's lithium-ion battery industry. In recent years, with the increasing investment in technology innovation, China The lithium-ion battery industry has developed rapidly in terms of technological innovation, and has formed a basic industrial core competitiveness, and has accumulated certain technological advantages in certain fields.
Research Status and Development Trend of Lithium Ion Battery Materials
The main structures of lithium ion batteries are a positive electrode, a negative electrode, an electrolyte capable of conducting lithium ions, and a separator separating the positive and negative electrodes. The electrochemical performance of lithium-ion batteries depends mainly on the structure and properties of the electrode materials and dielectric materials used. In particular, the choice and quality of the electrode materials directly determine the characteristics and price of the lithium-ion battery.
At present, the research on cathode materials of lithium ion batteries mainly focuses on lithium cobalt oxide and lithium nickelate. At the same time, the rise of some new cathode materials (such as Li-Mn-O materials and conductive polymers) is also the cathode material for lithium ion batteries. The development has injected new vitality, and it is an important research content in this field to find a new system for developing lithium ion secondary battery cathode materials with high voltage, high specific capacity and good cycle performance. At present, the positive electrode materials of lithium ion batteries are still transition metal oxides such as LiCoO2, LiNiO2, LiMn2O4 and their composite materials. From 2005 to 2010, high energy density polymer cathode materials and organic sulfides and inorganic sulfides become lithium ion batteries. A new generation of cathode materials. The anode materials of lithium-ion batteries mainly include carbon materials, lithium metal alloys, metal oxides, metal nitrides, nano-silicones, etc. Among them, carbon materials are the main negative electrode materials for commercial applications, and lithium metal alloys and nano-silicones have become hot spots for research and development. . The electrolyte material of lithium ion battery is mainly used to electrolyze its solvent into anhydrous organic matter, and most of them use mixed solvents such as EC-DMC and PC-DMC. LiPF6 is the most commonly used conductive salt.
For lithium-ion battery cathode materials, lithium cobalt oxide cathode materials still have strong vitality in the future. In the current commercial lithium-ion battery system, lithium cobalt oxide batteries rely on their high charge cut-off voltage and high-voltage solid density. The advantage is still the preferred battery system for high-end 3C battery products; while the layered LiNixCo1–x–yMnyO2 cathode material not only has high energy density, but also has the properties of material safety, cycle stability, high temperature performance and preparation cost. It is relatively excellent. The proportion of cathode materials used in the world has increased year by year. It has not only gradually replaced some applications of lithium cobalt oxide materials, but also emerged in the application of new energy vehicle power batteries. It is one of the most promising cathode materials in the future. In the near future, the mainstream direction of lithium ion wire cathode materials is still dominated by lithium cobalt oxide and LiNixCo1–x–yMnyO2 materials. Lithium iron phosphate and spinel manganese-based materials not only have lower preparation cost and resource advantages, but also have excellent safety and cycle stability. They are the preferred cathode materials for power batteries, especially LiNi0.5Mn1.5O4/Li4Ti5O12. The system power battery can achieve rapid charge and discharge, which is one of the mainstream directions of new energy vehicle power batteries in the future. High-energy density NCA cathode materials have a place in high-end 3C product batteries and new energy vehicle power batteries, but high cost, harsh battery manufacturing environment and other factors limit its wide range of applications. Lithium iron phosphate, potassium manganate, and NCA cathode materials have always occupied a certain position in the current cathode material structure. The layered lithium-rich manganese-based material is the next-generation industrialized cathode material with the highest energy density, and the market has broad application prospects. However, the problems of high irreversible capacity and poor rate performance caused by its own structural problems still need to be carried out by researchers. In-depth study.
Since the commercialization of lithium-ion batteries in the 1990s, carbon materials have been widely used in lithium-ion batteries and will continue to be the key base materials for lithium-ion batteries. In the new carbon anode, the future development will focus on high-power graphite anodes and non-graphite high-capacity carbon anodes to meet the needs of future power and high-energy batteries. Carbon conductive agents have an important impact on battery performance. The research of new conductive agents will focus on the development of high-ionic to characteristic carbon black and composite conductive agents obtained by compounding new carbon materials such as carbon nanotubes and graphene. Due to the special and two-dimensional flexible structure, carbon nanotube composite conductive agents have been widely used in the field of lithium ion batteries in recent years. Carbon nanotubes and graphene composite electrode materials are expected to be widely used in high-capacity lithium-ion batteries and lithium-ion power batteries after being improved by appropriate electrochemical performance and optimized in use.
Lithium-ion battery market status and development trend
The lithium-ion battery market can always be divided into three major markets: the consumer electronics market, the electric vehicle market, the industrial and energy storage applications market. The former is generally referred to as the 3C small lithium-ion battery market, and the latter two are the power lithium-ion battery market.
The development of lithium-ion battery industry has been concentrated in the 3C industry for more than 20 years, and it is less used in the market for larger energy storage and power batteries (instantaneously requiring large currents), which covers pure electric vehicles and hybrid electric vehicles. Vehicles, medium and large UPS, solar energy, large energy storage batteries, electric hand tools, electric motorcycles, electric bicycles, aerospace equipment and aircraft batteries. One of the main reasons is that the lithium cobalt oxide cathode material (LiCoO2, which is the most common lithium ion battery) used in lithium batteries in the past is costly and difficult to apply to special environments such as puncture, collision, high temperature and low temperature. More importantly, it has been criticized for failing to meet people's absolute requirements for safety. Colleagues, lithium cobalt oxide batteries can not achieve the purpose of fast charging and completely avoid secondary pollution, and must design protection circuits to prevent overcharging or over-discharging, otherwise it will cause explosion and other dangers, even if the explosion of Sony battery causes global The brand NB industry has invested heavily in recycling.
Currently, global and Chinese lithium-ion battery sales are mainly concentrated in the consumer electronics market, although its market share is declining. In 2012, 72.28% of the 38.176 million kWh lithium-ion batteries sold worldwide were in the consumer electronics market. In the Chinese market, the ratio was 65.40% (the total sales of lithium-ion batteries was 66.20 million kWh). In 2012, the total amount of lithium-ion batteries for mobile phones in the world was 108,600,100 kWh, which was lower than the 1,094.20 million kWh in 2011. However, in the Chinese market, the total number of lithium-ion batteries for mobile phones increased by 6.30%. In China, smartphones are rapidly replacing traditional feature phones. At present, most smartphones are equipped with battery tubes for less than a day, which means that even if the energy density of lithium-ion batteries is doubled, it is difficult to meet the demand. Therefore, for some time to come, The mobile power market, where consumer electronics is charging at any time, will grow rapidly. In 2012, the global demand for 1.23 million kWh mobile power lithium-ion batteries, more than 80% of which is made in China, of which the Chinese market has consumed 52.20 million kWh, which is the leading force in this market. China's tablet PC market is also developing rapidly and steadily. The annual growth rate is higher than the global average. The rapid increase in tablet PC sales has directly boosted the sales of lithium-ion batteries. In 2012, the sales volume of lithium-ion batteries for tablet PCs in China reached 284,900. kWh, an increase of 91.97%.
The lithium-ion battery used in the industrial & energy storage market is mainly divided into three categories: power tools, mobile base station power supplies, and wind power generation. In 2012, the total demand for lithium-ion batteries in the world, the industrial & energy storage market consumed 4.736 million kWh, accounting for 12.25%; China's market consumed a total of 731,500 kWh of lithium-ion batteries, the proportion is 15.65%, which is higher than the global .