Classification and technological development of power lithium-ion batteries
- Battery cell
First, a special solvent and a binder are mixed with the powdered positive and negative active materials respectively, and the positive and negative materials are made into a slurry after being evenly stirred. Then, the positive and negative electrode slurry is uniformly coated on the surface of the metal foil by an automatic coating machine, and after automatic drying, the positive and negative electrodes are automatically cut into positive and negative electrode pieces. Secondly, according to the sequence of positive electrode sheet, diaphragm, negative electrode sheet, and diaphragm, the electrolyte is injected through winding, sealing, and positive and negative lug welding processes to complete the assembly process of the battery and make the finished battery cell. Finally, the finished battery is placed in a test cabinet for charging and discharging tests and aging, and qualified finished batteries are screened out.
- Battery pack
The operating voltage of the battery pack is very high, and multiple lithium-ion batteries must be connected in series to reach the operating voltage of the car battery. At present, electric vehicles use lithium-ion batteries as power sources, which involves the assembly, structure, design, and management of lithium-ion battery packs.
As lithium-ion batteries are increasingly used in high-power equipment, the number of batteries in series and parallel is also increasing, which will increase the complexity of the battery management system, so it is necessary to improve the integration of the management system. Because the characteristics of different types of batteries are different, research on a more versatile battery management system (BMS) has become one of the key technologies for electric vehicles. In recent years, BMS has been greatly improved, but some parts are still not perfect, especially in terms of reliability of collected data, residual charge estimation (SOC) accuracy, fast charging of batteries, equalization circuits, and safety management. Improve and improve.
At present, some large foreign automobile manufacturers and battery suppliers have done a lot of research and experiments on various batteries, and have developed many battery management systems and installed them on vehicles for trial. The more representative ones are the BATTMAN system designed by B.Hauck in Germany, the battery management system on the EVI electric vehicle produced by General Motors in the United States, the Smart Guard system developed by Aerovironment in the United States, and so on.
- Lithium-ion battery classification (by application field)
The lithium-ion battery industry is an energy storage industry, which is widely used in communication power supplies, electric vehicles, and megawatt-level energy storage power supplies (such as wind energy, solar energy, smart grid) and other fields. According to different application areas, lithium-ion batteries can be divided into electrical appliances batteries, energy storage batteries, power batteries and micro batteries.
Electrical appliances battery (high energy);
Application areas: electrical products such as information, communications, office and digital entertainment.
Features: fast updating of electrical appliances, constant power, low requirements for battery rate performance, operating temperature, cost, and cycle performance.
Performance: The battery energy density is higher than 200wh/kg, and 100% DOD is 200-300 times.
Energy storage battery (long life);
Application areas: small energy storage power supply: UPS, solar energy, fuel cell, wind power and other distributed independent power system energy storage.
Features: The requirements for battery power and energy density are not high, and the requirements for volume and weight are relatively low.
Performance: 0-20 years of service life, maintenance-free, stable performance, low price, better temperature characteristics and lower self-discharge rate.
Power battery (high power):
Application areas: all kinds of electric vehicles, electric tools, high-power appliances.
Features: It requires high power density, safety, temperature characteristics, low cost, and high self-discharge rate.
Performance: The current power density level is 800~1500wW/kg, and the target is above 2000 W/kg.
Application areas: wireless sensors, micro unmanned aircraft, implantable medical devices, micro robots, etc.
Features: Electrical appliances are difficult to maintain, and require high stability and longevity.
Performance: Long life, good stability, all solid-state batteries are required.
- Technology Roadmap
During the five years from 2010 to 2015, the electrode and electrolyte (electrolyte) technology of lithium-ion batteries did not change significantly. The current technology is still being developed. The cathode materials of lithium-ion batteries mainly include lithium titanate materials, nickel cobalt aluminum three Element materials, nickel diamond manganese ternary materials, lithium manganate materials, spinel structure manganese compounds and lithium iron phosphate. The negative electrode material will still be mainly graphite, and titanate materials will be developed at the same time. The electrolyte is made of flat lithium polymer and prismatic lithium ion materials.
In the five-year period from 2015 to 2020, the technology will undergo major changes on the original basis, and both electrode and electrolyte technologies will be greatly developed. Among them, for cathode materials, lithium titanate materials and nickel diamond aluminum ternary materials will gradually be eliminated from the market after 2015, while lithium manganese phosphate materials are expected to replace lithium iron phosphate materials. The development trend of the entire cathode materials is 2020 The cathode of lithium-ion batteries based on manganese element materials was realized in about a year. Graphite in the negative electrode material is still one of the main materials, but it is expected to be eliminated from the market around 2020, titanate will continue to be used, and it is expected to realize the preparation of negative electrodes using silicon-tin alloy and vanadium around 2020. . The electrolyte is expected to realize the preparation of an electrolyte using lithium hyperpolymer as a material around 2020 on the original basis.