Study on NCA Materials for Power Lithium Battery -Lithium - Ion Battery Equipment
Driven by the increasing range of electric vehicles, the use of high nickel materials with higher capacity should be gradually popularized. Generally speaking, high nickel materials can be divided into two categories, one of which is NCA materials (typically LiNi0.80Co0.15Al0.05O2). The Ni content is about 80%. According to the process and material ratio of different manufacturers, the capacity can reach 170-200mAh/g. The second is NCM811 material, whose reversible capacity usually reaches 180-200mAh/g. In recent years, domestic material manufacturers have been relatively mature in NCM811 material technology, and have launched many products with good performance. However, the development of NCA materials is relatively lagging behind. There are few manufacturers producing NCA materials, and the products launched are also lagging behind Japan.(Lithium - Ion Battery Equipment)
Higher Ni content brings higher capacity, but also brings a series of problems: 1) High nickel materials usually have poor interface stability, and are easy to react with CO2 and H2O in the air. A layer of LiOH and Li2CO3 insulating layer is formed on the surface of particles, causing an increase in impedance; 2) The strong oxidation of Ni4+in the charging state often causes the decomposition of electrolyte on the particle surface; 3) The ionic radius of Ni2+(0.69A) is close to that of Li+(0.76A), so Li/Ni intermingling is very easy to occur in the process of material preparation and circulation. The occupation of Li site by Ni will lead to the reduction of reversible capacity and the reduction of diffusion coefficient of Li+.
Recently, Yu Yamamoto (the first author and corresponding author) of Sumika Chemical Analysis Service Co., Ltd. of Sumitomo Chemical, Japan, used high angle resolution electron channel X-ray spectroscopy to study the phase transition caused by Li/Ni mixing in NCA materials during circulation, and made a quantitative analysis of the proportion of Li/Ni mixing layers.
First, YuYamamoto analyzed the structure of NCA material coated on Al foil by means of X-ray (the X-ray spectrum is shown in the figure above). According to the calculation of X-ray diffraction data, it can be obtained that the cell size of NCA material is a=2.861A, c=14.17A. As the c value in the cell parameter is sensitive to the Li/Ni mixing ratio, while the a value is not sensitive to the mixing, and the c/a value of the material is 4.95, indicating that the NCA material has a highly ordered crystal structure, The proportion of Li/Ni mixed emission is low.
YuYamamoto's research shows that there is a transition layer between completely ordered layered structure and completely disordered rock salt structure - partially ordered structure, that is, Li/Ni is partially mixed. Through model fitting, it is also found that some ordered structures exist in the form of an independent layer, rather than uniformly distributed in the whole particle, which also indicates that the decay of NCA materials starts from the surface of particles, The interior of the gradual phase particles is transitional. YuYamamoto's work has also realized the quantitative analysis of the layered structure, rock salt structure and partial ordered structure in NCA materials, which has important guiding significance for guiding the optimization of NCA materials.
Higher Ni content brings higher capacity, but also brings a series of problems: 1) High nickel materials usually have poor interface stability, and are easy to react with CO2 and H2O in the air. A layer of LiOH and Li2CO3 insulating layer is formed on the surface of particles, causing an increase in impedance; 2) The strong oxidation of Ni4+in the charging state often causes the decomposition of electrolyte on the particle surface; 3) The ionic radius of Ni2+(0.69A) is close to that of Li+(0.76A), so Li/Ni intermingling is very easy to occur in the process of material preparation and circulation. The occupation of Li site by Ni will lead to the reduction of reversible capacity and the reduction of diffusion coefficient of Li+.
Recently, Yu Yamamoto (the first author and corresponding author) of Sumika Chemical Analysis Service Co., Ltd. of Sumitomo Chemical, Japan, used high angle resolution electron channel X-ray spectroscopy to study the phase transition caused by Li/Ni mixing in NCA materials during circulation, and made a quantitative analysis of the proportion of Li/Ni mixing layers.
First, YuYamamoto analyzed the structure of NCA material coated on Al foil by means of X-ray (the X-ray spectrum is shown in the figure above). According to the calculation of X-ray diffraction data, it can be obtained that the cell size of NCA material is a=2.861A, c=14.17A. As the c value in the cell parameter is sensitive to the Li/Ni mixing ratio, while the a value is not sensitive to the mixing, and the c/a value of the material is 4.95, indicating that the NCA material has a highly ordered crystal structure, The proportion of Li/Ni mixed emission is low.
YuYamamoto's research shows that there is a transition layer between completely ordered layered structure and completely disordered rock salt structure - partially ordered structure, that is, Li/Ni is partially mixed. Through model fitting, it is also found that some ordered structures exist in the form of an independent layer, rather than uniformly distributed in the whole particle, which also indicates that the decay of NCA materials starts from the surface of particles, The interior of the gradual phase particles is transitional. YuYamamoto's work has also realized the quantitative analysis of the layered structure, rock salt structure and partial ordered structure in NCA materials, which has important guiding significance for guiding the optimization of NCA materials.
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