Lithium composite compound particles and process for producing the same, and non-aqueous electrolyte secondary battery
The present invention relates to lithium composite compound particles having a composition represented by the formula: Li 1+x Ni 1−y−z Co y M z O 2 (M=B or Al), wherein the lithium composite compound particles have an ionic strength ratio A (LiO − /NiO 2 − ) of not more than 0.3 and an ionic strength ratio B (Li 3 CO 3 + /Ni + ) of not more than 20 as measured on a surface of the respective lithium composite compound particles using a time-of-flight secondary ion mass spectrometer. The lithium composite compound particles of the present invention can be used as a positive electrode active substance of a secondary battery which has good cycle characteristics and an excellent high-temperature storage property.
1. A process for producing the lithium composite compound particles comprising a lithium composite compound represented by the following compositional formula 1, which lithium composite compound particles have an ionic strength ratio A (LiO − /NiO 2 − ) of not more than 0.3 and an ionic strength ratio B (Li 3 CO 3 + /Ni + ) of not more than 20 as measured on a surface of the respective lithium composite compound particles using a time-of-flight secondary ion mass spectrometer:
Li 1+x Ni 1−y−z CO y M z O 2 Compositional formula 1
wherein M is at least one element selected from the group consisting of B and Al; and x, y and z satisfy −0.02≦x≦0.02, 0<y≦0.20 and 0<z≦0.10, respectively,
the process comprising the steps of (1) treating lithium composite compound particles with a water solvent to remove impurities therefrom; and (2) subjecting the lithium composite compound particles obtained in the step (1) to drying and then to heat treatment in a temperature range of 500 to 850° C. in an air or oxygen atmosphere having a carbon dioxide concentration of not more than 100 ppm,
wherein a ratio of a total molar amount of lithium to a total molar amount of a transition element, aluminum and boron in the lithium composite compound particles used in the step (1) being not less than 1.02 and not more than 1.10.
2. A process according to claim 1 , wherein the heat treatment is conducted in a temperature range of 600 to 850° C.