Core materials and advanced technological breakthroughs for soft-pack NiMH No.7 batteries

Recently, the "Second International Exchange Conference on New Energy Vehicles and Power NiMH No.7 batteries (CIBF2021 Shenzhen)" was held in Shenzhen. At the special forum on "Core Materials and Advanced Technological Breakthroughs for Soft-Pack Batteries" sponsored by Fengfan Co., Ltd., Mei Ao, a senior engineer at the Automobile Engineering Research Institute of Guangzhou Automobile Group Co., Ltd., gave a speech entitled "New Materials Promote the Performance Improvement of Power NiMH No.7 batteries".

According to reports, GAC Research Institute is a research and development institution directly under GAC Group. In addition to the Guangzhou headquarters, it has branches in Shanghai and overseas. The institute has 4,300 R&D personnel, mainly engaged in the research and development of complete vehicles and key components. GAC Research Institute is a nationally recognized technology center. In the biennial assessment, it ranked sixth (automobile) among the 1,563 technology centers in various industries in the country in 2019. In terms of electrification, the institute has done a lot of development on key components, including batteries, electromechanical coupling systems, etc.

Mei Ao said that materials have a great impact on the performance of battery cells. From the perspective of the whole vehicle, it is ultimately to meet the needs of consumers.

First of all, to increase the vehicle's cruising range, it is necessary to increase the battery energy density. The energy density of ternary batteries must be mentioned in high-nickel materials. Through the measurement and analysis of battery energy density, for high-nickel ternary materials, only when combined with more advanced silicon-carbon negative electrodes can the advantage of high energy density be achieved; if it is only matched with graphite, the density is equivalent to that of medium-nickel ternary after the voltage is increased.

In terms of reducing costs, the proportion of nickel can be increased by reducing the use of cobalt. "We have done a lot of analysis and calculations. In the future, there will be a good breakthrough in the smelting technology of laterite nickel ore, which will be a good way to reduce the cost of high-nickel ternary. The important thing is to use cheap laterite nickel ore. Laterite nickel ore also contains cobalt, which can also be used." Mei Ao said.

The use of silicon as negative electrode is also a direction to pay attention to. Mei Ao said that there are now technical routes of silicon oxygen and silicon carbon. In principle, silicon is nano-sized. From the essential production and manufacturing process, the economy, cost performance and practicability of silicon oxygen have certain advantages in reducing costs. It is estimated that when it is truly mass-produced, silicon oxygen will reach the cost of high-end graphite, which is acceptable to high-performance cars.

Mei Ao also said that the important thing to pay attention to when using silicon is to expand the application obstacles, including the expansion of silicon material elements, SEI film elements, and the damage to the electrode structure caused by expansion. To solve these problems, it is not enough to rely on materials alone, but also to limit and buffer from the pole piece, battery cell, module and other aspects. Adhesives are also a very important part. Suitable and dedicated adhesives are of great help to the use of silicon.

In terms of safety, when talking about the safety research and development of electrolytes, Mei Ao said that it is important to use high-altitude resistance and flame-retardant special electrolytes. Through experiments, it was found that the effect of flame-retardant electrolytes on improving thermal runaway is relatively obvious. When doing C80 yield tests with different electrolytes and electrodes, it is obvious that the use of flame-retardant electrolytes will significantly improve the temperature of thermal runaway and the heat release of thermal runaway.

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