Nickel Hydride Batteries direct sales

　　Chinese companies break through the core technology of high-nickel single crystal materials!

　　In recent years, China's new energy vehicle market has developed rapidly. In 2018, the production and sales of new energy vehicles in China both exceeded 1.2 million. China has become the world's largest new energy vehicle market.

　　In recent years, China's new energy vehicle market has developed rapidly. In 2018, the production and sales of new energy vehicles in China both exceeded 1.2 million. China has become the world's largest new energy vehicle market. In the field of passenger vehicles, the cruising range of newly launched electric vehicles continues to increase, and the NEDC comprehensive working condition cruising range of various models can reach more than 500km, which greatly improves the convenience of using electric vehicles.

　　The ever-increasing cruising range has also put forward higher and higher requirements for the energy density of the power battery. For example, among the new energy models announced by the National Development and Reform Commission in 2019, some models have a power battery system with an energy density of more than 180Wh/kg. The energy density of a single power battery is required to be at least 250Wh/kg.

　　The core of improving the energy density of power batteries lies in the development of high-capacity positive and negative electrode materials. Let’s take positive electrode materials as an example. At present, the mainstream positive electrode materials have gradually transitioned from traditional NCM111 materials to NCM523 and NCM622. The capacity of positive electrode materials has changed from 140mAh/g The left and right are increased to about 170mAh/g, and the energy density of the power battery is also increased to 230-260Wh/kg.

　　To further improve the capacity of positive electrode materials, we can mainly start from two aspects: 1) Increase Ni content, higher Ni content can bring higher specific capacity, for example, the reversible capacity of NCM811 material can reach 190-207mAh/g, if further Increase the Ni content to 0.9, and the capacity can be further increased to about 210-220mAh/g; 2) Increase the charging voltage, whether it is NCM811 or NCM622, the theoretical capacity is about 270mAh/g, which can be achieved without changing the material composition. The purpose of increasing the material capacity is achieved by increasing the charging voltage. For example, the capacity of NCM622 material at 4.3V is about 176mAh/g, but if the charging voltage is increased to 4.5V and 4.7V, its capacity can reach 201.3 and 218.1mAh/g .

　　Low temperature lithium iron phosphate battery 3.2V 20A -20℃ charge, -40℃ 3C discharge capacity ≥70%

　　Charging temperature: -20~45℃ -Discharging temperature: -40~+55℃ -40℃ supports maximum discharge rate: 3C -40℃ 3C discharge capacity retention rate≥70%

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　　However, the above measures will also lead to a significant decrease in the cycle performance and safety performance of the positive electrode material while increasing the capacity of the positive electrode material. Taking NCM622 material as an example, although the cut-off voltage of 4.7V can bring the specific capacity of NCM622 material close to 220mAh/g, But at the same time, the cycle life of the material will be seriously degraded. At 55°C, after 50 cycles of the half-cell system at a cut-off voltage of 4.7V, the capacity retention rate of the NCM622 material is only 78.9%, which is much lower than that of the NCM622 material (96.3%) cycled at 4.3V, and the high-nickel material at high voltage Cycle stability faces severe challenges.

　　Increasing the Ni content also faces the same problem. Compared with the NCM622 material, the NCM900505 material not only has a significant decrease in cycle performance, but also has a significant decrease in thermal stability. Under high voltage, NCM900505 is significantly worse than NCM622 in terms of thermal decomposition temperature and heat release, which corresponds to the poor safety of high-nickel materials in batteries.

　　These problems of high-nickel materials have seriously restricted the development of high-capacity battery products, and the emergence of single-crystal materials has opened a new direction for the development of high-capacity cathode materials. The so-called single-crystal materials are relative to traditional secondary particles. In terms of materials, traditional NCM materials are mostly secondary particles formed by the agglomeration of primary particles of 200-300nm, while single crystal materials are directly composed of independent crystals with a diameter of 2-5um. Due to higher crystallinity and more stable With layered structure and anisotropic characteristics, single crystal materials are superior to traditional secondary particle NCM materials in terms of cycle performance, thermal stability, and gas production.

　　Advantage 1: Improved cycle performance

　　The good structural stability of single crystal materials makes the material have very good cycle stability. Taking single crystal NCM523 as an example, after 300 cycles (3-4.4V, C/2) at 40°C, the single crystal NCM523 material battery’s The capacity retention rate can still reach 98%, but even the capacity retention rate of the secondary particle NCM523 material coated with Al2O3 is only 92%, and this gap will be more obvious under the high temperature condition of 55°C (single crystal> 94%, secondary particles <85%).

　　Low temperature high energy density 18650 3350mAh-40℃ 0.5C discharge capacity ≥60%

　　Charging temperature: 0~45℃ Discharging temperature: -40~+55℃ Specific energy: 240Wh/kg -40℃ discharge capacity retention rate: 0.5C discharge capacity≥60%

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　　Advantage 2: Reduced gas production

　　In recent years, with the continuous improvement of the energy density of power batteries, the market share of soft-pack batteries with higher energy density is also expanding year by year. Compared with hard-shell batteries, soft-pack batteries are more sensitive to gas production from materials, so the gas production is also One of the important indicators to measure the stability of materials. Through the floating charge experiment, it can be found that the gas production of single crystal materials is very small, and the gas production of 100h floating charge at 4.4V, 4.5V and 4.6V is only 0.01, 0.01 and 0.04ml, while the Al2O3 coated secondary The gas production of the granular NCM523 material battery reached 0.07, 0.27 and 0.62ml respectively, which once again shows that the single crystal material has a greater advantage in gas production.

　　Advantage 3: Improved thermal stability

　　Recently, many spontaneous combustion accidents of electric vehicles have brought the safety of electric vehicles to the forefront. We have already introduced that the thermal stability of materials will decrease with the increase of Ni content, and single crystal materials are more stable due to their crystal structure. Therefore, the thermal stability will also be improved accordingly. The O2 release experiment shows that the single crystal NCM523 material not only has no O2 release near 80°C, but also the O2 release peak temperature in the range of 200-350°C is higher than that of the secondary particle NCM523 material. , which also shows that single crystal materials have certain advantages in thermal stability.

　　The advantages of single crystal materials in terms of high voltage, high temperature cycle stability, thermal stability, and gas production have made it a high ground for major material manufacturers to compete. Domestic mainstream materials such as Dangsheng, Bamo and Shanshan Manufacturers have begun to launch single-crystal NCM622 and NCM523 materials, but compared with secondary granular materials, single-crystal materials have a slightly lower capacity. Therefore, single-crystal NCM622 materials cannot fully meet the needs of high specific energy batteries. Therefore, major materials Manufacturers have actively carried out the research and development of single crystal NCM811 materials with higher capacity.