The recent engineering production and Research Institute of lithium (GGII) visited more than and 50 enterprises and participated in a number of forums, found that the current lithium battery has a major breakthrough in high energy density technology.
The development route of high energy density include: high voltage cathode material, high G capacity, positive and negative pole material. High voltage cathode materials are usually used to refer to the positive electrode material with a higher voltage than 4.2V. Lithium cobalt oxide, lithium manganese oxide, ternary of high voltage material.
High voltage lithium cobalt acid has been very mature, a large number of high-end digital products, the energy density of ternary higher than the average battery. At present, high voltage co - acid - Li - battery voltage is usually 4.35V, the next 4.4V years 3-5, 4.5V high voltage cobalt acid lithium battery or can be large-scale application.
Three high voltage cathode materials are very few, and are in the research stage. But ternary high voltage cathode materials may be a breakthrough in the future to achieve 300Wh/kg energy density.
At present, ternary NCM811 grams capacity has more than 180mAh/g, coated or doped by high voltage can be achieved at the same time, it will further improve the capacity of G (high voltage material equivalent to low voltage when no active lithium activation, greater use of materials). However, there are still a lot of technical problems in the current ternary of high voltage material is not resolved, the stability of the material itself has not yet been resolved.
LMO charging potential is 4.7V, the lattice structure is very stable.
At present, lithium battery energy density 150Wh/kg, higher than that of lithium iron phosphate battery energy density. Lithium manganese oxide crystal structure stability, good thermal stability, safety of the lithium battery is very high. The application prospect of lithium manganate - lithium titanate battery has an excellent system in the field of fast charging.
Lithium iron phosphate due to the capacity of the play has been close to the theory, it is difficult to activate more lithium by high voltage, the effect is very limited. However, iron manganese phosphate (vanadium) lithium, lithium iron silicate energy density is higher, is a lot of research institutes and enterprises in the hot areas of research, lithium iron silicate molecules contain two lithium ions, the theoretical capacity of up to 332mAh/g.
High voltage cathode material needs high voltage electrolyte to make the whole battery system running well. In order to stabilize the electrolyte in a high voltage environment, it is necessary to improve the oxidation resistance of the solvent, and to block the direct contact between the cathode and the electrolyte. The method for improving the oxidation resistance of the electrolytic solution includes the following steps, the price is too high, and the large-scale application is difficult to realize.
Other new antioxidant solvents such as ionic liquid, with good ionic conductivity and antioxidant capacity, is a good solvent for lithium battery, but the current price is high, it is difficult to large-scale promotion. The method of blocking the direct contact between the electrolyte and the electrolyte comprises the anode material coating, and the positive electrode film forming additive. Cathode material coating and additives research is very much, the effect is very obvious, is an important means to enhance the future of oxidation.
The large-scale development and application of ternary materials is relatively late, there is much room for improvement in the aspect of energy density. Currently mainstream material manufacturers have been able to do the 180mAh/g level, while the theoretical capacity of ternary of high nickel materials up to 270mAh/g, there is a lot of room for improvement. At present, there are some characteristics of high capacity ternary materials, such as water sensitivity, low efficiency, poor circulation and so on. These problems can be solved with the development of technology, and the anode of lithium is also a hot spot of many research institutes and enterprises.
On the other hand, silicon based anode materials can greatly enhance the capacity of the negative electrode. Cathode materials have been mainly graphite, graphite anode technology has been very mature, the actual capacity has been very close to the theoretical capacity. Other materials must be used to increase the capacity of negative pole.
Silicon tin and other metal anode is a very suitable choice, the first Japanese Sony has used tin composite anode to enhance the battery energy density, has launched a high capacity of 18650 products to the market. In recent years, silicon composite anode has been paid more attention, in which the technology of silicon carbon composite cathode and silicon oxide / graphite composite anode is more mature, and Japan and South Korea enterprises have been applied to high capacity products.
At present, the domestic material factory, the electric core factory has also gradually introduced a series of silicon cathode high capacity products. The theoretical capacity of silicon is 4200mAh/g, but the volume expansion effect is very large, so it is more influenced by the graphite composite to reduce the expansion. The lithium metal anode has a higher capacity than the silicon cathode, but the dendrite is not solved, and the safety risk is high. The metal lithium is easy to react with the electrolyte, and the cycle life of the electrolyte is reduced. At present, the metal lithium anode battery is still difficult to scale to the market.
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