Lithium-ion battery separator is called 'third pole'. The important role of diaphragm in the comprehensive performance of lithium battery is embodied in the following three aspects: The positive and negative electrodes of the isolated battery. The diaphragm itself is not conductive and can prevent electrons from passing through the battery. To prevent short circuit caused by contact between the two poles; allow lithium ions to pass through. The micropores on the diaphragm allow lithium ions to be transferred between the positive and negative electrodes to complete the electrochemical charge and discharge process; prevent battery explosion caused by high temperature. When the battery is overheated, the diaphragm The micropores are closed, preventing lithium ions from passing through, and the internal resistance of the battery is raised to 2KΩ, forcing the battery to stop charging and discharging.
In recent years, with the development of China's new energy industry and the continuous improvement of lithium battery production technology, China has become the world's largest lithium battery manufacturing base and the second largest producer and exporter of lithium-ion batteries. The demand for lithium battery separators is also growing.
Total demand continues to grow rapidly
According to the data released by the Prospective Industry Research Institute, since 2011, China's domestic diaphragm market demand has maintained a market growth rate of more than 30%. In 2017, the market demand reached 1.516 billion square meters. Prospective Industry Research Institute believes that with China The development of new energy industry, the future lithium battery separator industry still has a good demand potential, it is expected that the market demand will reach 2.7 billion square meters by 2020.
3C digital, new energy vehicle demand accounted for over 90%
On the one hand, the continuous increase in demand, on the one hand, the demand structure of downstream products is also gradually changing.
From the demand of the main downstream market in 2017, it can be seen that China's 3C digital and new energy vehicles are the main demand areas for lithium battery separators, accounting for more than 90% of the total; energy storage batteries rank third, demand The proportion is 6.6%. Overall, the downstream demand for lithium battery separators in China is relatively concentrated, and the development of downstream markets has a greater impact on the development of lithium battery separator industry.
Based on the above analysis, the forward-looking industry research institute believes that with the continuous development of China's new energy automobile industry, the future demand for the diaphragm in this field will exceed the demand of 3C digital field, combined with new energy vehicles, 3C digital industry development forecast, and The overall forecast for lithium battery separators in the future is expected to account for more than 50% of the diaphragm demand in the new energy vehicle sector in 2020, becoming the largest demand area for the diaphragm. The current development of the energy storage sector is on the rise and is expected to maintain rapid growth in the next few years. In 2020, its demand for diaphragms will increase from the current 6.6% to 11%.
The proportion of coated film is gradually increasing
According to the product requirements, the diaphragm can be coated on one side or on both sides. The thickness is usually 1-2 um. The coated diaphragm not only improves the heat shrinkage rate, but also increases the tensile strength and the liquid absorption rate. At the same time, the porosity and the gas permeability are reduced. The higher tensile strength of the separator can improve the controllability of the cell, and the lower heat shrinkage can make the battery safer at higher temperatures, and the porosity is relatively smaller to reduce the short circuit of the cell. Rate, the increase in liquid absorption rate helps to increase the energy density of the battery.
Based on the above advantages, in recent years, the demand for coatings for lithium battery separators has been increasing. In 2017, the demand for coated membranes by major overseas battery companies was close to 50%, compared with the main domestic batteries. The demand for coated diaphragms still accounts for about 20%. Overall, compared with the leading international battery companies, the future development of coated diaphragms in China is still relatively large.