Power cell development faces six challenges

Wangzidong, director of the power battery laboratory at China's Northern Vehicle Research Institute, expressed his concern about the recent fire in China's new energy passenger cars and the death of one person. At present, there are 2,000 to 3,000 lithium battery manufacturers in China. Under the lack of core technology, In short supply of power batteries, many companies began to produce power batteries. But power cells and conventional lithium batteries are two different things in manufacturing technology.

The safety of electric vehicles becomes the focus of the development of power batteries facing six major challenges

The following is a transcript of Wangzidong's statement:

Power cell has become the bottleneck technology for the new industrial development of electric vehicles in China. At present, there are many battery research and production enterprises in China, but the overall strength is not strong, the industrial chain is incomplete, and we are still facing the pressure caused by foreign companies entering China. Under such a state, how do we deal with it?

We need to conduct in-depth research and systematic thinking on the deeper issues ahead, and make breakthroughs and steady progress.

The scientific research force of all parties in society needs to work together to support the sustainable development of the power battery industry in China and create opportunities.

The winner is often not because of ability, but because of ideas. The pressure on our entire industry:

The top four global lithium-ion battery companies are Samsung SDI, Panasonic, LG Chemical, and Sony. Samsung SDI has surpassed Panasonic to become the world's first. Statistics show that Samsung SDI is a company that produces and sells almost as much as China's top 10 combined.

The top 10 companies account for about 78 per cent of production and sales, which is a stark difference from global performance. There is no doubt about the fact that Chinese companies generally lack the advantage of size, and this situation may be difficult to change for some time to come. How to maintain their existence and development in the absence of economies of scale is an urgent task before Chinese enterprises.

One of the reasons for this situation is that domestic power battery companies are too loose and lack mutual loyalty. Electric car companies treat power battery companies only as parts suppliers and believe that there are many options. In this case, power battery companies are reluctant to develop suitable power batteries for electric car companies.

Power battery companies need to grow and develop simultaneously with electric car companies. These can be seen from the formation of a close R&D community between foreign companies and battery companies. These companies are not simple trading relationships in power batteries, but strategic alliance R&D relationships. And in our country, now the vehicle factory also regards the battery company as a supplier.

Challenge 1. The future of electric cars is determined not by cost but by efficiency

The most important bottleneck restricting the popularity of pure electric vehicles is not the mileage, because more batteries are installed and the mileage is high, like Tesla; Nor is it cost. With the increase in popularity, costs will eventually come down, just as Henry Ford's assembly line is for cars; It is efficiency that determines whether a new technology can eventually be popularized.

This refers not only to energy conversion efficiency, but also to pure electric power, which is much higher than traditional internal combustion engines. It is an efficient use. At present, the relatively good charging level of pure electric vehicles can only be 80 % charged in 20 minutes(about 100-120 kilometers); Assume that the average speed is 60km/h, that is, every 2 hours of driving must stop for 20 minutes! In fact, even if there are charging piles everywhere, you are unlikely to follow the charge, and it is inevitable that you will have to queue up. Assuming there are two cars in front of you, you will have to wait for an hour. Such efficiency can not be used as a daily means of transportation!

Therefore, if an electric vehicle with a charging mileage of less than 200 km can not solve the problem of rapid replenishment of electric vehicle energy, even if charging piles are popular, pure electric vehicles can not completely replace traditional cars. It can only be used as a supplement., applicable to short distances.

Ways to solve the problem: reducing weight and energy consumption; Increase battery energy; Install extenders; Install high-efficiency solar panels to supplement some of the energy; Replacement of batteries.

Challenge 2, Electric Vehicle power battery encountered low temperature charging difficulties

Most of the current electric vehicles, especially electric buses, electric taxis, and private electric vehicles, use lithium batteries. The demonstration work of new energy vehicles in Beijing, Qingdao, Changchun, tangshan and baotou all encountered difficulties in charging in winter to varying degrees, which reduced the capacity of electric buses in winter and made it difficult to ensure normal operation. The problem is twofold:

The first is the decline in battery performance in a low-temperature environment, a better drop of 10-15 %, and an almost 35 % drop, which is related to the material state, battery structure, production process, shell structure, and thermal management system function;

The second is that low temperature charging easily produces lithium, and irreversible reactions occur, which causes the battery capacity and energy to drop significantly. Severe lithium branching crystals will pierce the diaphragm, short-circuit the battery and cause a safety accident.

Challenge 3. Cost: Cost of power batteries

For the current battery production technology, carry out core cost analysis:

1, 100 Ah lithium iron phosphate battery material cost:

Positive material 0.8 kg-100 yuan, negative material 0.4 kg-25 yuan, diaphragm 5m2 -40 yuan, electrolyte 0.5 kg-40 yuan, shell 40 yuan / set, processing fee 55 yuan, total 300 yuan, equivalent to: 0.938 yuan / Wh;

2.100 Ah material cost of lithium battery:

Positive material 0.7 kg-100 yuan, negative material 0.4 kg-25 yuan, diaphragm 5m2 -40 yuan, electrolyte 0.5 kg-40 yuan, shell 40 yuan / set, processing fee 55 yuan, total 300 yuan, equivalent to: 0.834 yuan / Wh;

3, 100 Ah lithium manganese acid material battery material cost:

Positive material 0.95 kg-88 yuan, negative material 0.4 kg-25 yuan, diaphragm 5m2 -40 yuan, electrolyte 0.5 kg-40 yuan, shell 40 kg/sleeve, processing fee 55 yuan, total 288 yuan, equivalent to: 0.78 yuan / Wh.

Other cost connotations of the core:

Design fee, test fee, die fee, development fee;

Material utilization rate, raw material purchase cost, product conformity rate;

Equipment depreciation, financial costs, sales costs, management fees, personnel training fees;

Taxes and fees, employee benefits, insurance premiums, enterprise profits.

At present, due to the small volume, the core cost becomes 2 yuan or more after amortization of various expenses.

Cost of batteries:

Technology development costs.

The battery pack has a winter charging and heating system, a system for cooling during summer work, an anti-vibration structure in use, a waterproof structure in rainy days, an anti-impact structure in accidents, a reliability design for connections, and a BMS reliability design.

The system increases the cost of components.

The battery pack is convenient for installation and has a convenient structure for maintenance inspection.

Performance test fee, reliability assessment fee;

Equipment depreciation fee, personnel training fee, product transportation fee;

Financial expenses, sales expenses, management fees, taxes, welfare expenses, insurance premiums, and corporate profits.

The cost of stealth.

The cost of the combined battery pack becomes more than 3 yuan/Wh.

Challenge 4. Security

The safety of power batteries is crucial to the development of the electric car industry. In recent years, with the increase in the number of trials and operations of various energy-saving and new-energy vehicles, safety accidents have occurred from time to time, and the distribution of accidents has been viewed vertically: in processing, manufacturing, converting into shelving, transportation, testing, use, charging and maintenance, and recycling. There have been problems.

From the horizontal point of view: domestic and foreign in mobile phones, computers, electric bicycles, electric motorcycles, electric cars, electric buses, hybrid cars and other fields of application, there have also been problems. Most of the current power cell problems occur when charging, and low temperature charging increases the probability of problems. How to improve the reliability and safety of power cells has become the focus of attention in the industry.

Challenge 5, long life use. So-Called battery consistency, reliability

1) The ability to control battery consistency during production, which can be controlled by automated production equipment and "correct production processes"(it is important to find a process that can control product quality). In addition, the structure design of the battery should meet the requirements of large-scale mechanized production equipment.

2) The ability to control battery consistency during use is also important.

A. Reasonable battery structure reduces the temperature imbalance of the battery itself at low temperatures;

B. Improve battery power performance by minimizing cell contact resistance while reducing local temperature rise;

C. Pay attention to the cooling effect of each cell surface, select a scientific and reasonable ventilation structure, so that the temperature field of the entire battery can be uniform, so as to ensure the environmental consistency of the battery during the use of the low temperature environment. For the problem of battery system consistency, there are obvious misunderstandings:

It is believed that battery manufacturers should achieve a ± 1 % range of battery consistency. In fact, battery companies provide power batteries for vehicle companies. Consistency can be controlled within this range, but why is the consistency of the group different? 10 %?

The problem is that in the process of group formation and integration, the temperature is inconsistent, resulting in different efficiencies in the work of the battery, resulting in inconsistent batteries.

In addition, the unreasonable charging method of the battery pack also has a relatively large impact.

Challenge 6. Business models for electric vehicle development, use and promotion?

Electric vehicles do not offer users the same value for money as electric bicycles or mobile phones, or solve problems for users. That is, they do not reflect the added value of users. Users are most concerned about what features they need to use electric vehicles.

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