Lithium manganate positive electrode active material as well as positive electrode sheet, secondary battery, battery module, battery pack and powered device comprising the same
A lithium manganate positive electrode active material, comprising a lithium manganate matrix and a cladding layer as a “barrier layer” and a “functional layer” are described. The cladding layer can not only “prevent” the transition metal ions which have been produced by the lithium manganate matrix from directly “running” into the electrolyte solution, but also “prevent” the hydrofluoric acid in the electrolyte solution from directly contacting with the lithium manganate substrate, and then prevent the lithium manganate matrix from dissolving out more transition metal manganese ions; as a “functional layer”, the cladding layer contains various effective ingredients inside, which can reduce the transition metal manganese ions already present inside the battery through chemical reactions or adsorption effects, thus slowing down the generation of transition metal manganese and the decomposition of the SEI film (solid electrolyte interphase film) catalyzed by the transition metal manganese.
1. A lithium manganate positive electrode active material comprising a lithium manganate matrix and a cladding layer, wherein the cladding layer comprises an inner layer provided on the surface of the lithium manganate matrix, an interlayer provided on the surface of the inner layer, and an outer layer provided on the surface of the interlayer, wherein,
the inner layer comprises one or more of oxyacid salt of aluminum, calcium and/or magnesium, wherein
the oxyacid salt of aluminum, calcium and/or magnesium is selected from one or more of potassium aluminate, magnesium aluminate, calcium carbonate, calcium aluminate, magnesium carbonate, and magnesium aluminate;
the interlayer is an organic bonding material layer; and
the outer layer is an oxalate and/or silicate layer, wherein
the lithium manganate positive electrode active material has a multi-level pore structure with an average pore size of 15-20 nm and a porosity of 10-20%.
2. The lithium manganate positive electrode active material according to claim 1 , wherein,
the organic bonding material is selected from one or more of carboxymethyl cellulose salt, alginate salt, and polyacrylate salt.
3. The lithium manganate positive electrode active material according to claim 1 , wherein,
the oxalate is selected from an alkali metal salt, an alkaline earth metal salt or an ammonium salt of oxalic acid;
the silicate is selected from an alkali metal salt, an alkaline earth metal salt or an ammonium salt of silicic acid.
4. The lithium manganate positive electrode active material according to claim 1 , wherein,
the mass ratio of the inner layer to the lithium manganate matrix is 0.01-3:100;
optionally, the mass ratio of the interlayer to the lithium manganate matrix is 0.5-3:100; and
optionally, the mass ratio of the outer layer to the lithium manganate matrix is 0.5-12:100.
5. The lithium manganate positive electrode active material according to claim 1 , wherein,
the mass ratio of the inner layer:interlayer:outer layer is 1-2:1-2:0.5-6.
6. The lithium manganate positive electrode active material according to claim 1 , wherein,
the mass ratio of the oxalate to the silicate is 0.01-99:1.
7. The lithium manganate positive electrode active material according to claim 1 , wherein,
the lithium manganate positive electrode active material has a volume average particle size D50 of 12-14 μm.
8. The lithium manganate positive electrode active material according to claim 1 , wherein,
the interlayer has a rough surface obtained by hydrochloric acid etching.
9. The lithium manganate positive electrode active material according to claim 1 , wherein,
the cladding layer has a thickness of 0.3-5.2 μm.
10. A positive electrode sheet, wherein,
the positive electrode sheet comprises the lithium manganate positive electrode active material according to claim 1 .
11. The positive electrode sheet according to claim 10 , wherein,
the positive electrode sheet comprises a ternary nickel-cobalt-manganese material, and the mass ratio of the ternary nickel-cobalt-manganese material to the lithium manganate positive electrode active material is 0.01-0.99:1.
12. A lithium-ion battery
comprising one or more of the lithium manganate positive electrode active material according to claim 1 .
13. A battery module comprising the lithium-ion battery of claim 12 .
14. A lithium manganate positive electrode active material comprising a lithium manganate matrix and a cladding layer, wherein the cladding layer comprises an inner layer provided on the surface of the lithium manganate matrix, an interlayer provided on the surface of the inner layer, and an outer layer provided on the surface of the interlayer, wherein,
the inner layer comprises one or more of fluoride of aluminum, calcium and/or magnesium;
the interlayer is an organic bonding material layer; and
the outer layer is an oxalate and/or silicate layer.
15. The lithium manganate positive electrode active material according to claim 14 , wherein,
the fluoride is one or more of aluminum fluoride, calcium fluoride, and magnesium fluoride.