Lithium nickelate-based positive electrode active substance particles and process for producing the same, and non-aqueous electrolyte secondary battery
The present invention provides lithium nickelate-based positive electrode active substance particles having a high energy density which are excellent in charge/discharge cycle characteristics when highly charged, and hardly suffer from generation of gases upon storage under high-temperature conditions, and a process for producing the positive electrode active substance particles, as well as a non-aqueous electrolyte secondary battery. The present invention relates to positive electrode active substance particles each comprising a core particle X comprising a lithium nickelate composite oxide having a layer structure which is represented by the formula: Li 1+a Ni 1-b-c Co b M c O 2 wherein M is at least one element selected from the group consisting of Mn, Al, B, Mg, Ti, Sn, Zn and Zr; a is a number of −0.1 to 0.2 (−0.1≤a≤0.2); b is a number of 0.05 to 0.5 (0.05≤b≤0.5); and c is a number of 0.01 to 0.4 (0.01≤c≤0.4); a coating compound Y comprising at least one element selected from the group consisting of Al, Mg, Zr, Ti and Si; and a coating compound Z comprising an Li element, in which a content of lithium hydroxide LiOH in the positive electrode active substance particles is not more than 0.40% by weight, a content of lithium carbonate Li 2 CO 3 in the positive electrode active substance particles is not more than 0.65% by weight, and a weight ratio of the content of lithium carbonate to the content of lithium hydroxide is not less than 1.
1. Positive electrode active substance particles each comprising:
a core particle X comprising a lithium nickelate composite oxide having a layer structure which is represented by the formula:
Li 1+a Ni 1-b-c Co b M c O 2
wherein M is at least one element selected from the group consisting of Mn, Al, B, Mg, Ti, Sn, Zn and Zr; and wherein:
−0.1≤a≤0.2;
0.05≤b≤0.5; and
0.01≤c≤0.4;
a coating compound Y comprising at least one element selected from the group consisting of Al, Mg, Zr, Ti and Si, wherein compound Y comprises an oxide, carbonate, or hydroxide; and
a coating compound Z comprising an Li element, wherein coating compound Z comprises an oxide, carbonate, or hydroxide,
in which a content of lithium hydroxide (LiOH) in the coating compound Z is 0 to 0.40% by weight, a content of lithium carbonate (Li 2 CO 3 ) in the coating compound Z is 0 to 0.65% by weight, and a weight ratio of the content of lithium carbonate to the content of lithium hydroxide in the coating compound Z is not less than 1 and not greater than 3.42,
wherein coating compound Y and coating compound Z are separate coating compounds.
2. The positive electrode active substance particles according to claim 1 , wherein a weight ratio of the coating compound Z to the coating compound Y is in the range of 1 to 100.
3. The positive electrode active substance particles according to claim 1 , wherein the positive electrode active substance particles have a BET specific surface area of 0.05 to 0.70 m 2 /g, a median diameter D 50 of aggregated particles of 1 to 30 μm, and a 2% powder pH value of not more than 11.40.
4. A non-aqueous electrolyte secondary battery comprising a positive electrode active substance comprising the positive electrode active substance particles as claimed in claim 1 .
5. A process for producing the positive electrode active substance particles as claimed in claim 1 , comprising the steps of:
forming the coating compound Y on a surface of the core particle X by a vapor phase epitaxy method; and then
subjecting the resulting particle to humidification treatment and heat treatment in atmospheric air at a temperature of 150 to 450° C. to form the coating compound Z on the particle.
6. A process for producing the positive electrode active substance particles as claimed in claim 1 , comprising the steps of:
subjecting the core particle X to humidification treatment and heat treatment in atmospheric air at a temperature of 150 to 450° C. to form the coating compound Z on a surface of the core particle X; and then
forming the coating compound Y on the resulting particle by a vapor phase epitaxy method.