New energy development needs to be more cautious domestic lithium battery diaphragm is in urgent need of a breakthrough

"I don't know how long this car's battery will last?"

"Zhou zhen, director of the institute of new energy materials chemistry at nankai university and a doctoral supervisor, said to himself as he looked out the window at another new energy vehicle passing by on the morning of June 15.

Engaged in new energy materials research for more than 20 years, looking at the growing number of new energy vehicles, Zhou zhen is happy, but still worry, "lithium battery basic materials research, we and the world-class level, especially high-end battery diaphragm materials still rely on imports.

Zhou zhen and other experts in the industry, as the new energy car "heart", domestic lithium ion battery (hereinafter referred to as lithium battery) at present "jump" is not stable enough.

The four-nation game across the Pacific

Last year, Chinese companies accounted for seven of the top 10 global sales of power batteries, surpassing Japan in market share and ranking first in the world. It is expected that China will account for more than 70% of the global battery market by 2020. At present, China has more than 200 battery manufacturers, which is the largest number of lithium battery manufacturers in the world... However, this series of figures did not make the industry proud. Many people pointed out in the interview that although China has formed a relatively complete industrial chain of power batteries, the battery industry is large enough, but it is far from strong.

There is a four-nation game across the Pacific for lithium batteries. "From the perspective of the industry, the United States has relatively strong r & d and design capabilities, and is still leading the original innovation of lithium batteries and the research and development of core materials. As a big country of battery material manufacturing, Japan has strict production specifications and can be the first to produce new finished batteries. China and South Korea as the second tier, follow up... "Compared with Japan and South Korea, China's low-end lithium battery products have more advantages, mainly due to the relatively cheap labor and raw materials, but there is still a big gap in some high-end products, especially the core materials and manufacturing processes related to battery safety," zhou explained.

It is understood that the battery four core materials, positive, negative material, electrolyte have achieved domestic, but the diaphragm is still a short board. Domestic diaphragm mainly supplies low-end 3C battery market, high-end diaphragm is still heavily dependent on imports. The lack of core patents and the failure of diaphragm and other key materials have not only caused unbearable pain for domestic lithium batteries, but also dragged the domestic lithium battery enterprises to "go out".

A person in charge of Tianjin lishen battery told the reporter that the core patents of ternary materials at the forefront of lithium battery lie in the hands of 3M and argonne national laboratory. 3M holds the patents of NMC materials of conventional stoichiometric ratio, and argonne national laboratory holds the patents of layered lithium-rich materials. At present, Panasonic, Samsung, LG and other mainstream manufacturers have to pay for the relevant patent licensing. "Domestic lithium battery enterprises are numerous, and entering the international market in the future. Facing the competition from international giants, the lack of core patents and material technology is the biggest worry and shortcoming of Chinese battery enterprises in the future. The person in charge said.

A thin film makes two days

In the interview, a battery material expert told the reporter, diaphragm is one of the key components of lithium battery, membrane is mainly made of porous polymer film, including polyethylene and polypropylene. The diaphragm used in lithium batteries has strict requirements for safety, permeability, porosity and thickness.

"In the lithium battery, charged ions flow between the positive and negative poles to form current, and the diaphragm is located between the positive and negative poles in the battery, which should not only prevent direct contact between the positive and negative poles, but also ensure the smooth passage of electrolyte ions. Zhou explained graphically that battery electrolyte is like a river, lithium ion is like a boat running on the river, diaphragm is built around the waist of the dam, a diaphragm hole is like the sluice gate on the dam, under normal circumstances, ions free shuttle to the positive and negative poles, complete the cycle of charge and discharge.

"If the electrolyte gets too hot and the material expands, the pores close like a sluice gate, cutting off the ion exchange and preventing the battery from catching fire and exploding." Zhou zhen introduced that the diaphragm is a kind of material with the highest technical barriers in lithium electric materials, and its technical difficulties lie in the engineering technology of making holes, matrix materials, and manufacturing equipment. "The technology is demanding and the price is expensive, accounting for more than 10 percent of the total cost of the battery."

At present, the best lithium battery membrane materials in the world come from two Japanese companies, asahi chemical and toru chemical, and 90% of the domestic lithium battery aluminum plastic film market share is also monopolized by showa denko and other Japanese manufacturers. Tianjin lishen company engineers told reporters, compared with Japan, China's high-end diaphragm gap is obvious. Domestic diaphragm product consistency is not high, there are not up to the standard porosity, thickness, pore distribution and pore diameter distribution is not equal.

The quality of diaphragm directly affects battery capacity, cycle life of charge and discharge, flame retardant and explosion stop safety performance and other indicators. The personage inside course of study regrets: "one layer of diaphragm two days, stride past is a fine day!"

Domestic diaphragm is in urgent need of breakthrough

At present, the manufacturing process of lithium battery diaphragm is mainly divided into wet method and dry method. In the interview, the reporter learned that China has entered the world's first square in the dry process technology, but in the wet process diaphragm field, although domestic enterprises master the method, but the overall is still difficult to compete with foreign giants, in addition, the core production equipment is mainly dependent on imports.

Data shows that in 2017, the domestic lithium battery market reached about 113 billion Yuan, including about 60 billion Yuan for power lithium batteries. According to the energy conservation and new energy vehicle industry development plan (2011-2020) issued by the ministry of industry and information technology, China's production capacity of pure electric vehicles and plug-in hybrid electric vehicles will reach 2 million per year by 2020. According to the estimation of the battery industry association, China will need several hundred million square meters of high-quality diaphragm materials for vehicle power batteries every year in the future.

"Lithium battery development should not be controlled by others, and high-end materials such as diaphragm cannot be avoided! Wu mengtao, general manager of Tianjin palmer co., believes that such a huge market demand, completely dependent on foreign manufacturers, is not only unrealistic, but also will be the biggest worry of domestic power lithium battery.

High-end diaphragm technology has a rather high threshold, not only to invest a huge amount of money, but also need to have a strong r & d and production team, skilled process technology and high level of production lines. "For wet manufacturing processes, the extrusion mixing process of resin materials and additives and the stretching process are two core difficulties." Zhou Zhen believes that domestic diaphragm enterprises want to have more as, must be in the base material surface treatment technology, such as tensile adhesive technics, stamping products involving materials, equipment and process control, and other areas of the three "lessons", in addition, the diaphragm industrial chain upstream, including domestic coating machine etc, the core production equipment also needs to catch up, as soon as possible to realize localization of greater breakthrough.

"It's like climbing a mountain. The closer you are to the top, the better your chances of reaching the top. "Zhou zhen said.

The page contains the contents of the machine translation.