So far, the basic design of lithium-ion batteries is still the same as SONY’s patent application published in 1989. The shapes of the monomers are cylindrical, square metal shell (aluminum/steel) and square soft pack bulk. Cylindrical batteries were originally used in notebook computers. Now Tesla and other companies use 18650 cylindrical batteries for electric vehicles. The prismatic battery generally has a large capacity, and the battery cell is made by winding, Z-shaped lamination, winding + lamination, positive electrode coating lamination, lamination + winding, etc. Cylindrical batteries have the most mature technology and lower manufacturing costs, but large cylindrical batteries have poor heat dissipation capabilities, so small cylindrical batteries are generally used. The car battery pack has a large capacity and a large number of batteries, and the management system is more complicated and expensive. The manufacturing process of the wound structure battery in the square battery is relatively simple, but it is mainly suitable for the soft pole piece battery. This method can be used for batteries using lithium iron phosphate and ternary materials except for the spinel cathode material. The laminated battery with high reliability and long life is suitable for various material systems. The batteries of the GM Volt plug-in hybrid electric vehicle and the Nissan Leaf pure electric vehicle are manufactured by the laminated technology. By 2015, the specific energy of lithium iron phosphate battery will reach 140W·h/kg, and the specific energy of ternary material mixed lithium manganate battery will reach 180W·h/kg. The specific energy of small cylindrical batteries of NCA is adopted internationally. Reaching 240W·h/kg, the specific energy of lithium-ion single cells will further increase in the next few years, and it is expected to reach 300W·h/kg by 2020.
With its excellent mechanical properties, good electrochemical stability and relatively cheap characteristics, polyolefin microporous membranes are currently the main varieties in the lithium-ion battery separator market . Including polyethylene (PE) single layer film, polypropylene (PP) single layer film and PP/PE/PP three-layer composite microporous film. There are many domestic manufacturers that use dry process production, and many companies have mass production of wet process PE diaphragms. With the promotion of ceramic coating technology, high-temperature and high-voltage diaphragms will become the direction of future research and development.