What are the research hot spots of high energy technology of lithium battery?

Recently, the Institute of High Industrial Production and Research Lithium Research Institute(GGII) visited more than 50 companies and participated in multiple forums. It was found that lithium batteries currently have major breakthroughs in high-energy density technology.

The development routes of high energy density include: high voltage positive electrode materials and Gao Ke capacity positive and negative electrode materials. The high voltage positive electrode material usually refers to a positive electrode material with a battery voltage higher than 4.2 V. Lithium cobalt acid, lithium manganese acid, and ternary have high voltage materials.

Among them, the commercialization of lithium high voltage has been very mature, and it is widely used in high-end digital products. Its energy density is higher than that of ordinary ternary batteries. At present, the voltage of the lithium high voltage battery is usually 4.35 V, and in the next 3-5 years 4.4 V and 4.5 V high voltage battery may be applied on a large scale.

There are few applications of high voltage positive electrode materials and they are basically in the research stage. However, the ternary high voltage positive electrode material may be the breakthrough for reaching 300 Wh / kg of energy density in the future.

At present, the capacity of the ternary NCM811 material has exceeded 180 mAh/g, and the capacity of the material can be achieved by encapsulating or mixing. At the same time, the capacity of the material will be further increased(high voltage material is equivalent to activating the inactive lithium at low voltage. More limited use of materials). However, there are still many technical problems in the high voltage of ternary materials, and the stability of the material itself has not yet been solved.

The lithium manganate cathode material has a charging potential of up to 4.7V and a very stable lattice structure.

At present, the energy density of lithium manganese acid batteries is 150 Wh / kg, which is higher than the energy density of lithium iron phosphate batteries. Lithium manganate crystal has stable structure and good thermal stability. The safety of lithium manganate battery is very high. Lithium-titanate system batteries have excellent application prospects in the fast charging field.

lithium iron phosphate is close to the theory because of its capacity, and it is difficult to activate more lithium through high voltage, and the effect is very limited. However, ferromanganese phosphate(vanadium) lithium and lithium ferric silicate have a higher energy density and are popular areas for research by many research institutions and companies. Lithium ferric silicate molecules contain two lithium ions, and their theoretical gram capacity is as high as 332 mAh/g.

high voltage 's positive material requires high voltage electrolytes to cooperate to make the entire battery system work well. In order to make the electrolyte run stably in the high voltage environment, it is necessary to improve the oxidation resistance of the solvent and to block the direct contact between the positive electrode and the electrolyte. The methods for improving the antioxidant properties of electrolytes include fluorinated solvents. The price of fluorinated solvents is too high and it is difficult to achieve large-scale applications.

Other new antioxidant solvents such as Ionic liquids have good Ionic conductivity and antioxidant capabilities. They are excellent lithium battery solvents, but they are currently expensive and difficult to promote on a large scale. The methods of blocking direct contact between electrolytes and electrolytes include positive polar material coating and positive polar film forming additives. There are many studies on the coating and additives of positive materials, and the effect is very obvious. It is an important means to enhance the antioxidant properties in the future.

The large-scale development and application of ternary materials are relatively late, and there is still a lot of room for improvement in energy density. At present, mainstream material manufacturers have been able to achieve a 180mAh/g level, while the theoretical capacity of ternary high nickel materials can reach 270mAh/g, and there is still great room for improvement. At present, high-capacity ternary materials have the characteristics of water sensitivity, low efficiency for the first time, and poor circulation. Lithium-rich positive poles are also hot spots in many research institutions and enterprises as the process technology progresses and these problems may be solved.

On the other hand, Silicon negative electrode materials can greatly increase the negative gram capacity. The negative electrode material has been dominated by graphite, and the graphite negative electrode technology has become very mature. The actual capacity is already very close to the theoretical capacity. To increase the negative gram capacity, other materials must be used.

The negative electrode of metal such as Silicon tin is a very suitable choice. The earliest Japanese Sony used tin composite negative poles to increase the battery energy density and has already introduced high-capacity 1,8650 products to the market. In recent years, the Silicon composite negative electrode has been paid attention, among which the Silicon carbon composite negative electrode and the silicon-graphite oxide composite negative electrode technology are relatively mature, and Japanese and Korean enterprises have been applied to high-capacity products.

At present, domestic materials factories, electric core plants have gradually introduced Silicon series negative extremely high capacity products. Silicon's theoretical gram capacity is 4200mAh/g, but the volumetric expansion effect is very large, so it is mostly combined with graphite to reduce the impact of expansion. The negative electrode of metallic lithium has higher capacity than the negative electrode of Silicon, but its dendrites problem has not been solved and the safety risk is high. The metal lithium reacts easily with the electrolyte and reduces its cycle life. At present, metal lithium negative electrode batteries are still difficult to market on a large scale.

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