The need for automated production of lithium-ion power batteries

The development of new energy vehicles is inseparable from the progress of power batteries. After years of development, China has formed a complete industrial chain of lithium battery from the development of upstream resources, to the manufacturing of mid-stream production equipment, to the application of lithium battery in the downstream. However, problems such as high battery cost, low energy density and short range remain to be solved.

Compared with other countries in the world, what is the gap between China and other countries in the level of power battery technology? What is the relationship between battery automation and battery consistency? Which batteries are safer? What are the prospects for battery recycling? In response to the above questions, the reporter interviewed xue jiayu, chief scientist of shandong yuhuang new energy technology co., ltd. and a special expert of the national "thousand talents plan".

Lithium battery production needs to be automated

China energy news: you have been studying lithium ion batteries for more than 20 years. From abroad to China, what do you think is the fundamental for the safety of lithium ion batteries?

Xue jiayu: lithium ion battery has been developed for 25 years. In the first 20 years, the main application field was limited to small electrical appliances (mobile phones, laptops, etc.). Its security has never been fully addressed. In recent years, with the development of electric vehicles, the development of lithium battery has entered a new climax.

Many companies have flocked to the industry. But in the end, it must be those who can survive the quality of the enterprise. To talk about the safety of the battery, first of all to ensure the consistency of battery performance, otherwise the safety of the battery is out of the question.

As we all know, tesla USES 18650 battery, which is the industry standard in lithium industry, and it was mainly used in laptop computer products before. Tesla USES thousands of 18,650 batteries assembled in cars as power sources. When so many batteries are put together, each battery has two soldering wires (one positive and one negative), so there are a lot of connecting wires, and any loose soldering can cause the battery to lose function. Why did tesla use the 18650 battery? Although not specifically designed for electric vehicles, the 18650 battery is the oldest product in the industry, or industry benchmark. It has relatively complete safety protection system and better product consistency. If large capacity single battery can achieve the consistency of 18650, people will certainly use large capacity power battery, which can reduce the number of solder joints, improve reliability.

China energy news: China's lithium battery life is not optimistic, what do you think?

Xue jiayu: to take a simple example, the fengfeng storage and transportation demonstration station in zhangbei, China, has installed energy storage batteries, including those produced by well-known lithium battery manufacturers in China. After 4-5 years of operation, the batteries have almost been replaced. That is to say, the life of ordinary lithium battery is still not good enough to meet the needs of energy storage applications. Such a lithium-ion battery would be almost impossible to run on an electric car without replacing the battery for five to eight years.

China energy news: is there a big gap between China and the world in the field of power lithium-ion batteries?

Xue jiayu: the lithium battery production in the world is mainly in Asia, where there are three major players -- Japan, South Korea and China. The main technological gap between China and Japan and South Korea is in automation and solid research into battery chemistry. Until now, Chinese manufacturers of lithium-ion batteries for mobile phones have been unable to compete with Japanese and south Korean manufacturers, mainly because of the automation of battery production. Automated batteries often produce products that are more consistent than those produced by hand or by so-called "critical process automation." Product consistency is good, relative safety is higher.

Now with the rise of the power battery market, the consistency of products has been put forward higher requirements than small batteries. This is a promotion for the upgrading of China's lithium electric enterprises, but also a glimmer of vitality. The Chinese government's strong support for electric vehicles and energy storage is a big plus. Chinese lithium - electric enterprises must seize this opportunity. China is flush with cash for making power batteries, so automated lithium production is possible.

China energy news: is there a necessary relationship between battery consistency and battery production automation?

Xue jiayu: that's for sure. Lithium battery production needs automation, and is fully automated better than semi-automatic. For example, in the process of handling the battery in the semi-automatic production line, the battery may accidentally fall to the ground, causing internal injuries that cannot be seen on the surface, which will cause irreversible damage to the battery performance. People are the most variable factor in the lithium battery production process, but automatic machines are basically the same under normal operation. So only automation to do lithium battery can maximize product consistency.

China energy news: now the country advocates industry 4.0, automation has been adopted by many enterprises.

Xue jiayu: in the process of automatic production, only advanced equipment can not make good battery products. For example, if a complete set of equipment is imported from Japan, but cannot produce batteries of the same quality as in Japan, there must be an engineering team that knows how to use automation equipment. In addition, the management philosophy of the upper management of the company must be changed. The cost of automated production is still high. It can efficiently make qualified products, but also can efficiently make unqualified defective products. At present the domestic factory can achieve the full automation production or the unmanned workshop enterprise is not many. Many large enterprises and groups in China have invested a lot of money in the automated production line. The investment is not a problem, but whether there are technical and management talents who know how to build, operate and maintain the automated production line and a complete set of company system.

Lithium titanate batteries may be coming back

China energy news: now at home and abroad commonly reported some cases of electric car battery explosion, lithium battery field which is relatively good safety?

Xue jiayu: the current lithium titanate battery is the battery with the longest life and the highest safety. In terms of life cycle, ordinary lithium ion battery is about 1000-2000 cycles, while lithium titanate is 10-20 thousand cycles. In addition, lithium titanate battery has excellent power characteristics and high and low temperature performance, the only deficiency is low energy density. Previously, there were concerns about bloating in lithium titanate batteries, a problem that had been technically addressed. The mass production technology of lithium titanate battery is also mature, but many lithium battery enterprises have not really mastered the technical essentials of mass production of lithium titanate battery.

Of course, one-sided emphasis on the safety of lithium titanate materials is also wrong. The entire electric vehicle power system is a system engineering, any part of which can produce a safety accident.

China energy news: what are the main applications of lithium titanate batteries?

Xue jiayu: lithium titanate battery has a certain market share in new energy vehicles, but it is not easy to become a mainstream product because of its low energy density. But it has a lot of potential in energy storage because it requires relatively little weight. If we consider the life cycle of lithium titanate batteries and the low cost, this technology is very attractive. Compared to the current lithium ion energy storage battery, the life of lithium titanate battery is five times that, which is 15 years. The cost of battery replacement, downtime, debugging and maintenance, and possible trouble caused by the mixed use of old and new batteries, etc. are considerable savings in these aspects when using lithium titanate batteries. Whether batteries are used for automobile power or energy storage, the most fundamental performance requirement is good consistency and high cost performance.

China energy news: what about other types of batteries, such as lithium air batteries, all-solid batteries and graphene batteries?

Xue jiayu: at present, there are still a lot of laboratory problems to be solved for lithium air battery and all-solid battery, which are far from industrialization. The so-called superior performance of graphene batteries is hard to believe because some properties of this material have been amplified by theoretical calculation.

Difficulty in recycling

China energy news: there are different opinions in the industry about the recycling or cascade utilization of power batteries. Some people think it can be used in echelon to avoid waste, but others think it is not operable. What do you think?

Xue jiayu: frankly speaking, I'm not very optimistic about cascade utilization. The reason is that batteries are different, consistent, and with different histories of production and use, putting them together is no easy task.

China energy news: is there no way to test battery consistency?

Xue jiayu: yes, but it's very difficult! Good consistency refers to the consistency or dynamic consistency of the whole life cycle cycle. Specifically, a group of batteries is required to have the same capacity and internal resistance over the actual long life of the battery, at least in a narrow band without divergence. But in reality, a group of batteries at some unknown moment may have one or several batteries with varying degrees of capacity decline or internal resistance increase. In this way, when charging, the average amount of power that is also applicable to the whole group of batteries will overcharge the battery whose capacity has decayed, which is a potential safety hazard that may cause fire or explosion. So, the amount of charge a battery gets depends on the worst battery.

Consistency of each cell in a battery pack is important. It can be a nightmare to put together batteries with lots of different histories, manufacturer dates, and raw material recipes for positive and negative electrodes that are not completely clear. Although some control can be done through a power management system (BMS), the control capability is limited. The safety of old batteries is a difficult subject to guarantee.

China energy news: what about recycling used batteries as a resource?

Xue jiayu: in the previous recycling of lithium batteries, the main elements with recycling value were cobalt and nickel. The state encourages the recycling of resources and there is nothing wrong with taking precautions. With the continuous expansion of the industrial scale, resource recovery makes the entire lithium battery industry chain form a closed loop, which is conducive to the development of the industry. But from a business perspective, recycling is an unprofitable business. The state may have to subsidize recycling and utilization of resources, or withhold some profits from some high-profit links of the industrial chain to subsidize battery recycling enterprises, so as to maintain environmental protection and harmony of the industrial chain of lithium battery.

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