Many potential consumers are deterred by the short range and high cost of electric vehicles.

　　The energy density of lithium-ion power batteries has become a bottleneck for its industrialization. For this reason, the United States, Japan, South Korea and other countries have formulated relevant industrial policies, all of which aim at "energy density reaching 300Wh/kg in 2020." Recently, with the support of national key projects, the R&D team of CATL New Energy Technology Co., Ltd. has conquered key core technologies such as high-nickel ternary materials and silicon-carbon anode materials, and has taken the lead in developing a specific energy (mass energy density) of 304Wh/kg. The battery sample won the first prize in this international competition.

　　Open up the "two channels of Ren and Du" and make up for the shortcomings of cathode materials

　　Lithium-ion power batteries are currently the most widely used new energy vehicle power batteries and are the core part of new energy vehicles. Its advantages lie in high energy density and long cycle life. Its technical difficulties lie in high stability and safety requirements and complex preparation process. This core production technology has always been in the hands of a few countries in the world.

　　The energy density of a battery refers to the electrical energy released by the average unit volume or mass of the battery. "The current increase in energy density has become the biggest bottleneck restricting the development of lithium-ion batteries, which are facing many world-class problems." Wu Kai, chief scientist of CATL, said that battery manufacturers can achieve the effect of power expansion by increasing battery size, but battery capacity Core "getting fat" or "growing taller" only treats the symptoms, not the root cause.

　　What exactly limits the energy density of lithium batteries?

　　Wu Kai said that the chemical system behind the battery is the main reason. Generally speaking, the four parts of a lithium battery are very critical: positive electrode, negative electrode, electrolyte, and diaphragm. The positive and negative electrodes are where chemical reactions occur, which are equivalent to the "Ren and Du meridians" of the human body.

　　Since the energy density of the current negative electrode material is much greater than that of the positive electrode, the positive electrode material has become the "short board of the barrel" - the lower limit of energy density of lithium-ion batteries depends on the positive electrode material, so increasing energy density requires continuous upgrading of positive electrode materials. However, the development of high-nickel materials in my country started late, the technology accumulation is relatively weak, and the preparation technology and equipment conditions are relatively backward.

　　"The stable supply of high-performance high-nickel cathode materials in batches is one of the key technical difficulties in the development of high-specific energy power batteries." Wu Kai said. To this end, CATL relies on major scientific research such as the National Engineering Research Center and the Fujian Provincial Key Laboratory. The platform, through collaborative development with upstream and downstream partners in the industry chain, optimizes raw material synthesis process conditions, improves structural stability, adjusts microstructure, controls material morphology and size distribution, and gradually realizes the large-scale production and application of domestic high-nickel materials. .

　　Compared with similar materials from Japanese and Korean competitors, the current domestic high-nickel materials have the characteristics of high reversible capacity, high compaction density, and relatively stable surface and bulk structures. They will break the Japanese and Korean technology monopoly and improve the technical level of the domestic industrial chain and The core competitiveness of domestic power batteries has eliminated the “first obstacle” on the road to innovation.

　　Subvert the tradition and solve the shortcomings of negative electrode materials

　　The negative electrode material is also one of the core materials of lithium-ion batteries. Currently, graphite is mostly used as the negative electrode material. As the demand for cruising range continues to escalate, traditional graphite anodes can no longer meet market expectations for battery energy density.

　　According to calculations, the specific capacity of silicon-based anode materials can be up to 10 times that of graphite anodes, and it is regarded as a "substitute" for the latter. The application of traditional silicon-based materials mainly uses carbon coating technology, which is to compound a layer of carbon material on the surface of silicon materials. Wu Kai said that due to the volume change of the silicon material during charging and discharging as high as 300%, the surface-coated carbon material will break and fall off after multiple cycles, and the protective effect on the silicon material will be greatly weakened, resulting in poor battery cycle performance.

　　This world-class problem has plagued the industry like a "ghost" for the past 10 years.

　　CATL abandoned traditional carbon coating technology and turned to research on artificial electrolyte interface film coating technology. It took more than 2 years to apply this technology to the preparation of silicon materials, and developed a new artificial electrolyte interface film-coated silicon-carbon composite anode material with independent intellectual property rights. Its cycle performance is significantly better than that of foreign products, breaking the innovation path. The "second stumbling block".

　　“Compared with carbon materials, the artificial electrolyte interface film has stronger binding force with silicon materials, better elasticity, is not easily broken or pulverized, and plays a very good protective role for silicon materials, so it can greatly increase the silicon content during cycles. The interface stability of the material will improve the cycle life of the battery." Wu Kai said that this move will promote our country to fully master core technologies such as material modification and precursor synthesis, and realize the localization of key material technologies to provide silicon carbon The gradual commercial promotion and application of composite anodes provides an important guarantee.

　　Perfect "slimming", the first to use special grade "7 series aluminum"

　　When energy consumption remains unchanged and volume and weight are limited, the cruising range of new energy vehicles mainly depends on the energy density of the battery pack.

　　"This tests the researchers' ability to 'slim down' the battery pack." Wu Kai said that for the first time, CATL applied special grade "7 series aluminum" to the lower box of the battery pack. "7 series aluminum", the "combat aluminum" among aluminum, is often used to make aircraft landing gears and has the characteristics of lightness, strength and safety.

　　Wu Kai told reporters that the application of "7 series aluminum" also has many risks, especially the phenomenon of stress corrosion (metal materials break in certain specific media due to the combined action of corrosive media and stress).

　　"The industry generally believes that this is a technical difficulty of '7 series aluminum', and even a technical forbidden area." Wu Kai said that for this reason, they have controlled the stress corrosion index at the highest level in the industry through hundreds of experiments and related process improvements. . At present, CATL has successfully developed the "7 Series Aluminum" lower box and has put it into mass production.

　　So far, the company's lightweight design of the battery pack's lower box has been at the world's leading level. This new energy density power battery can increase the load capacity (total power of the battery) by about 50% on the existing basis of the B-class pure electric car battery compartment without adding additional space; the energy of the vehicle-mounted power battery system Increase by 50%; the weight of the entire vehicle can be reduced by 250 kilograms on the existing basis, increasing the driving range of this model to more than 600 kilometers under standard operating conditions.

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