High tap density lithium positive electrode active material, intermediate and process of preparation
A lithium positive electrode active material intermediate comprising less than 80 wt % spinel phase and a net chemical composition of Li x Ni y Mn 2-y O 4-δ wherein 0.9≤x≤1.1; 0.4≤y≤0.5; and 0.1≤δ; where the lithium positive electrode active material intermediate has been heat treated in a reducing atmosphere at a temperature of from 300° C. to 1200° C. A process for the preparation of a lithium positive electrode active material with high tap density for a high voltage secondary battery where the cathode is fully or partially operated above 4.4 V vs. Li/Li+, comprising the steps of a) heating a precursor in a reducing atmosphere at a temperature of from 300° C. to 1200° C. to obtain a lithium positive electrode active material intermediate; b) heating the product of step a. in a non-reducing atmosphere at a temperature of from 300° C. to 1200° C.
1. A lithium positive electrode active material intermediate comprising less than 80 wt % spinel phase and having a net chemical composition of Li x Ni y Mn 2-y O 4-δ wherein:
0≤ x≤ 1.1;
0.4 ≤y≤ 0.5;
0.1≤δ;
and has been heat treated in a reducing atmosphere to a temperature of between 300° C. and 750° C.,
wherein the reducing atmosphere is selected from the group consisting of a gas containing less than 15 vol % oxygen and a gas containing an added substance, which is capable of removing all or part of oxidizing species present in the gas.
2. A lithium positive electrode active material intermediate according to claim 1 , wherein 0.9≤x≤1.1 in the chemical composition Li x Ni y Mn 2-y O 4-δ .
3. A lithium positive electrode active material intermediate according to claim 1 , wherein the tap density of the intermediate is equal to or greater than 1.8 g cm −3 .
4. A lithium positive electrode active material intermediate according to claim 1 , where said intermediate has been produced from two or more starting materials and where said starting materials have been partly or fully decomposed by heat treatment.
5. A lithium positive electrode active material intermediate according to claim 1 , further comprising up to 2 mol % of one or more other elements than Li, Ni, Mn and O.