Precursor of Li-ion cathode material, the preparation method thereof and Li-ion cathode material
Li-ion cathode materials with improved performance characteristics and precursors to prepare such materials are disclosed. The precursors consist of complex, mixed alkali transition metal oxides of the formula Li x A y (Mn a Ni b M c )O 2+d , where M represents one or more selected from transition metal elements beside Ni and Mn, and the groups IIA and IIIA elements of the periodic table, x is between 1 and 1.4, y is between 0.1 and 0.5, and x+y is between 1.1 and 1.5, a+b+c=1, the value of d depends on the proportions and average oxidation states of the cation elements Li, A, Mn, Ni and M such that the combined positive charge of the cation elements is balanced by the number of oxygen anions, A represents one or more elements selected from Na, K and Cs. The Li-ion cathode materials are produced by exchange of element(s) A for Li under mild conditions to limit the degree of structural reorganization that occurs during the reaction.
1. A method for preparing a precursor to a Li-ion cathode material containing at least Li, A, Ni and Mn and layered phase Li 2 MnO 3 with a composition of Li x A y (Mn a Ni b M c )O 2+d , where M represents one or more elements selected from transition metal elements beside Ni and Mn, and the groups IIA and IIIA elements of the periodic table, x is between 1 and 1.4, y is between 0.1 and 0.5, and x+y is between 1.1 and 1.5, a+b+c=1, the value of d depends on the proportions and average oxidation states of the cation elements Li, A, Mn, Ni and M such that the combined positive charge of the cation elements is balanced by the number of oxygen anions, and A represents one or more elements selected from Na, K and Cs comprising:
(1) dissolving soluble salts of Ni, Mn and M in water to obtain a solution of mixed cations;
(2) combining the solution of mixed cations with a basic solution of lithium hydroxide or lithium carbonate to obtain a solid precipitate; and
(3) mixing the solid precipitate with a combination of lithium carbonate and/or lithium hydroxide and at least one of other carbonates and/or hydroxides of Na, K, and/or Cs, and then firing the mixture.
2. The method of claim 1 wherein M represents one or more elements selected from B, Mg, Al, Ti, Fe, and Co.