Lithium metal oxide cathode materials and method to make them
A method for forming lithium metal oxides comprised of Ni, Mn and Co useful for making lithium ion batteries comprises providing precursor particulates of Ni and Co that are of a particular size that allows the formation of improved lithium metal oxides. The method allows the formation of lithium metal oxides having improved safety while retaining good capacity and rate capability. In particular, the method allows for the formation of lithium metal oxide where the primary particle surface Mn/Ni ratio is greater than the bulk Mn/Ni. Likewise the method allows the formation of lithium metal oxides with secondary particles having much higher densities allowing for higher cathode densities and battery capacities while retaining good capacity and rate performance.
1. A method to make a lithium metal oxide powder comprised of Li, Ni, Mn, Co and oxygen useful to make a lithium ion battery cathode, comprising
(a) providing a precursor mixture comprising a particulate precursor comprised of Li, Ni, Co and oxygen and providing a Mn particulate precursor devoid of Ni and Co, wherein the particulate precursor comprising Li, Ni, Co, and oxygen has an unagglomerated primary particle size having a D50 of 0.1 to 0.8 micrometer, D10 of 0.05 to 0.3 micrometer, D90 of 0.35 to 1.5 micrometer and no particles essentially larger than 3 micrometers, wherein the Mn particulate precursor is milled separately from the particulate precursor comprised of Li, Ni, Co, and oxygen,
(b) agglomerating the precursor mixture to form secondary particles comprised of primary particles of the particulate precursor comprised of Li, Ni, Co and oxygen and the Mn particulate precursor,
(c) heating the secondary particles under an oxygen containing atmosphere to a temperature of from 930° C. to 960° C. and time to form the lithium metal oxide powder.
2. The method of claim 1 , wherein each particulate precursor is an oxide, hydroxide, carbonate or combination thereof.
3. The method of claim 1 , wherein the Mn particulate precursor is devoid of Li.
4. The method of claim 3 , wherein the precursor mixture is comprised of a Ni particulate precursor, a Co particulate precursor and a Li particulate precursor and the Mn particulate precursor in which each of the Ni particulate precursor, the Co particulate precursor, the Li particulate precursor, and the Mn particulate precursor does not contain a metal in any of the other particulate precursors.
5. The method of claim 1 , wherein the Mn particulate precursor has an unagglomerated primary particle size D50 that is larger than the D50 of the particulate precursor comprised of Li, Ni, Co and oxygen.
6. The method of claim 1 , wherein the heating is to a maximum temperature and at least one lower interim temperature that is held for a period of time.
7. The method of claim 1 , wherein the atmosphere is an oxidizing atmosphere where oxygen is present in an amount of at least 0.01 to 0.3 oxygen partial pressure in atmospheres.
8. The method of claim 7 , wherein the oxygen partial pressure decreases during the heating.