canrd

  I. Material systems and basic theory 1.1 Chemical composition and crystal structure of trivalent materials The crystal structure of the ternary cathode materials (lini _ xCo _ yMn _ zO _ 2 or lini _ xCo _ yAl _ zO _ 2) is a lamellar a-NaFeO _ 2 type, with space group R-3m. Nickel cobalt manganese (aluminum) ions occupy the 3a position, lithium ions occupy the 3b position, and oxygen ions occupy the 6c position. Nickel content directly affects: Specific capacity : Ni²+ / Ni⁴+ redox couple provides the main capacity （ about 15-20mAh / g per 10% increase in Ni content ） Structural stability : High Ni material （ Ni ≥ 80 % ） is prone to H2 → H3 phase transition , resulting in lattice distortion rate of more than 6 % Thermal stability : Thermal decomposition temperature decreases by about 15 ℃ per 10 % increase in nickel content 1.2 Technology comparison of low- and medium-nickel and high-nickel systems System type Typical Model Nickel content Specific capacity (mAh / g) Heat out of co...