Modified ternary material and precursor thereof and preparation methods for modified ternary material and precursor

A process for preparing a precursor of a modified ternary material for a lithium ion battery positive electrode material, wherein the particular steps are as follows:

• (1) adding a ternary salt solution A of nickel, cobalt and manganese into a reaction kettle at a certain rate, wherein the molar ratio of Ni:Co:Mn=(⅓−x):(⅓+2x):(⅓−x), where 0<x≦⅓), carrying out a coprecipitation reaction with an alkali solution to obtain a solid-liquid mixture, the molecular formula of the precipitated solid being (Ni1/3−xCo1/3+2xMn1/3−x)(OH)2, where 0<x≦⅓, so as to form an inner layer part of the precursor;
• (2) in the following course of injecting the ternary salt solution A of nickel, cobalt and manganese and a ternary salt solution B of nickel, cobalt and manganese, adjusting the flow rate of the alkali solution at any time to keep the pH value of the solution in the reaction kettle between 10-12;
• first, continuing the addition of the ternary salt solution A of nickel, cobalt and manganese into the reaction kettle at a decreasing rate with a decrement of 100-1,000 ml per hour, and at the same time, gradually adding the ternary salt solution B of nickel, cobalt and manganese with the same total molar ratio concentration into the reaction kettle at an increasing rate with a increment of 100-1,000 ml per hour from zero, wherein the molar ratio of Ni:Co:Mn=(0.5−y):
• 2y:(0.5−y), where 0≦y<⅙;
• so as to form an intermediate layer part of the above precursor which connects the inner layer and the outer layer and has a concentration gradient in the precursor;
• (3) when the injection speed of the ternary salt solution A of nickel, cobalt and manganese has decreased to zero, continuing the injection of the solution B until the complete injection into the reaction kettle with a constant speed at a certain rate, so as to form an outer layer of the precursor coated outside of the intermediate layer part of the above precursor;
• and
• (4) separating the solid-liquid mixture after the reaction in step (3) is completed by means of centrifugal filtration, washing the same to be neutral, and oven-drying the same at 60° C.-200° C. for 4-10 h;
• the general molecular formula of the precipitated solid obtained being (Ni1/3Co1/3Mn1/3)(OH)2, and the precipitated solid being the precursor of the modified ternary material.

A process for preparing a modified ternary material for a lithium ion battery positive electrode material, wherein the modified ternary material includes a precursor that has a composition of the following molecular formula:

• Ni1/3Co1/3Mn1/3(OH)2;
• and consists of three layers, wherein:
• an inner layer of the precursor is a ternary material with a cobalt content of greater than ⅓ and identical nickel and manganese contents, and the molecular formula of said inner layer of the precursor is:
• (Ni0.5−yCo2yMn0.5−y)(OH)2, where 0<x≦⅓;
• an outer layer of the precursor is a ternary material with a cobalt content of 0 to ⅓ and equal nickel and manganese contents, and the molecular formula of said outer layer of the precursor is:
• (Ni0.5−yCO2yMn0.5−y)(OH)2, where 0≦y<⅙;
• and
• an intermediate layer of the precursor is a concentration-gradient composite material of the above two materials of the inner layer and the outer layer of the precursor, and wherein the modified ternary material is prepared by crushing the precursor, then mixing the same with a lithium source and calcining, i.e., mixing the powder of said precursor with the lithium source and calcining at 300° C.-1,200° C. for 8-30 h to form the modified ternary material.