CN116789185A - Positive active material for lithium secondary battery and method for preparing the same - Google Patents
Positive active material for lithium secondary battery and method for preparing the same Download PDFInfo
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- 239000007774 positive electrode material Substances 0.000 title claims abstract description 97
- 238000000034 method Methods 0.000 title claims abstract description 50
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 30
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 30
- 239000002245 particle Substances 0.000 claims abstract description 185
- 239000013078 crystal Substances 0.000 claims abstract description 75
- 238000005245 sintering Methods 0.000 claims description 160
- 238000002156 mixing Methods 0.000 claims description 53
- 239000011572 manganese Substances 0.000 claims description 50
- 239000002243 precursor Substances 0.000 claims description 50
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 48
- 229910052760 oxygen Inorganic materials 0.000 claims description 48
- 239000001301 oxygen Substances 0.000 claims description 48
- 239000011248 coating agent Substances 0.000 claims description 38
- 238000000576 coating method Methods 0.000 claims description 38
- 229910052721 tungsten Inorganic materials 0.000 claims description 17
- 229910052720 vanadium Inorganic materials 0.000 claims description 17
- 229910052727 yttrium Inorganic materials 0.000 claims description 17
- 238000000975 co-precipitation Methods 0.000 claims description 15
- 239000007791 liquid phase Substances 0.000 claims description 15
- 239000011247 coating layer Substances 0.000 claims description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims description 4
- 239000008187 granular material Substances 0.000 claims description 3
- 239000011149 active material Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 description 143
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 73
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 48
- 230000008859 change Effects 0.000 description 26
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 14
- 239000004327 boric acid Substances 0.000 description 14
- 239000000203 mixture Substances 0.000 description 12
- 230000009467 reduction Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 9
- 229910052759 nickel Inorganic materials 0.000 description 9
- 238000012360 testing method Methods 0.000 description 8
- 239000007789 gas Substances 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 229910017026 Ni0.88Co0.08Mn0.04(OH)2 Inorganic materials 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 238000005056 compaction Methods 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000007872 degassing Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000011163 secondary particle Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000004537 pulping Methods 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000004438 BET method Methods 0.000 description 1
- 239000006245 Carbon black Super-P Substances 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N NMP Substances CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 1
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000006182 cathode active material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
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- -1 cycle Substances 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000011161 development Methods 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
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- 238000001556 precipitation Methods 0.000 description 1
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- 238000011160 research Methods 0.000 description 1
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- 235000002639 sodium chloride Nutrition 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- FQENQNTWSFEDLI-UHFFFAOYSA-J sodium diphosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]P([O-])(=O)OP([O-])([O-])=O FQENQNTWSFEDLI-UHFFFAOYSA-J 0.000 description 1
- 229940048086 sodium pyrophosphate Drugs 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 235000019818 tetrasodium diphosphate Nutrition 0.000 description 1
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 229910001428 transition metal ion Inorganic materials 0.000 description 1
- ZSDSQXJSNMTJDA-UHFFFAOYSA-N trifluralin Chemical compound CCCN(CCC)C1=C([N+]([O-])=O)C=C(C(F)(F)F)C=C1[N+]([O-])=O ZSDSQXJSNMTJDA-UHFFFAOYSA-N 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- Battery Electrode And Active Subsutance (AREA)
Abstract
The present invention relates to a positive electrode active material, a method for preparing the same, and a lithium secondary battery comprising the positive electrode active material, the positive electrode active material comprising formula Li 1+a1 Ni x1 Co y1 M z1 M′ 1‑x1‑y1‑z1 O 2 Represented polycrystalline particles and formula Li 1+a2 Ni x2 Co y2 M z2 M′ 1‑x2‑y2‑z2 O 2 Single crystal grains are shown.
Description
Technical Field
The present invention relates to a positive electrode active material, a method of preparing the same, and a lithium secondary battery including the positive electrode active material.
Background
In recent years, with the increasing of energy and environmental crisis, natural energy such as wind energy and solar energy is greatly developed, but the use efficiency of these energy is low, and the energy using gap in large scale cannot be satisfied. The lithium ion battery is a green secondary battery, has the outstanding advantages of high working voltage, high energy density, good cycle life, small self-discharge, no memory effect and the like, and is rapidly developed.
In the field of lithium ion batteries, layered ternary materials (NCM) have great development potential due to their high specific capacity and stability. However, as the nickel content in the NCM increases, the stability of the material gradually decreases. High activity Ni generated during charging 4+ The reaction with the electrolyte can generate NiO-like rock salt phase, seriously damages the structure of the layered material, causes the collapse of the positive electrode structure, and further induces the dissolution of transition metal ions, phase transformation and lattice oxygen precipitation. The "secondary particles" of the conventional polycrystalline NCM at present are generally composed of a plurality of nano-scale "primary particles", and the formation of micro-cracks of the secondary particles is caused by the change of lattice parameters during the charge and discharge processes. The microcracks formed expose fresh interfaces inside the secondary particles, further accelerating performance decay. It is noted that the higher the nickel content, the more pronounced the cracking effect. In summary, the main cause of the decrease in the cycle life of NCM, especially high nickel NCM, is microcracking, which causes the simultaneous decrease in the thermal stability, structural stability and cycle stability of the cathode material.
At present, in order to improve the generation of microcracks of high-nickel polycrystalline materials, most of researches adopt technologies such as cladding, doping and the like to improve the strength of large particles, but the compaction density is difficult to improve in the process of manufacturing batteries. At the same nickel content, the capacity of the polycrystalline small particles is higher than that of the polycrystalline large particles, but the circulation and gas production performances are reduced. The morphology of single crystal small particles is different from that of polycrystalline small particles, the particle strength is relatively high, but the capacity and the gas production performance are difficult to reach ideal levels, and the sieving and pulping have larger problems.
Patent CN 109962221B adopts an aggregate-doped monocrystal-like material, and the main components are monocrystal-like lithium iron manganese phosphate material and aggregate-like multielement material, wherein the multielement and lithium iron manganese phosphate belong to two different anode materials, and the testing voltage and the application range are different, so that the two materials are forcedly mixed together, and the respective advantages are inevitably sacrificed, thereby causing resource waste. The patent number CN 107154491B mixes two materials with different conductivities, and considers the capacities of the two materials respectively, but does not consider the influence of the Ni content of the two different materials on the final product, and mixes the two materials together, so that the particle size protection range is relatively wide, and the effect of the final product is difficult to determine.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and effectively improve the defects of low capacity and poor circulation of the blended product. According to the invention, the capacity of the positive electrode active material is effectively improved by setting the content of small-particle Ni to be higher than that of large-particle Ni; in addition, by preparing the polycrystalline large particles and the monocrystalline small particles, different surface characteristics of the polycrystalline large particles and the monocrystalline small particles are controlled, and generation of microcracks of the polycrystalline large particles is effectively inhibited, so that stability of the cathode active material in a long-term circulation process is improved. The positive electrode active material provided by the invention has the characteristics of high compaction, high capacity and high stability.
In one aspect, the present invention provides a positive electrode active material for a lithium secondary battery, characterized in that the positive electrode active material comprises polycrystalline particles represented by formula A1 and single crystal particles represented by formula A2
A1：Li 1+a1 Ni x1 Co y1 M z1 M′ 1-x1-y1-z1 O 2
A2：Li 1+a2 Ni x2 Co y2 M z2 M′ 1-x2-y2-z2 O 2
wherein ,
m is one or two elements selected from Mn and Al,
m' is one or more elements selected from B, F, mg, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W,
–0.03≤a1≤0.20，0.30≤x1≤0.99，0≤y1≤0.30，0≤z1≤0.30，0≤1–x1–y1–z1≤0.10，
–0.03≤a2≤0.20，0.31≤x2≤1.00，0≤y2≤0.30，0≤z2≤0.30，0≤1–x2–y2–z2≤0.10，
the conditions are as follows: 0< x2-x1 is less than or equal to 0.5.
In another aspect, the present invention also provides a method of preparing a positive electrode active material, comprising the steps of:
i) Preparing polycrystalline particle precursor represented by formula A3 and monocrystalline particle precursor represented by formula A4 by liquid phase coprecipitation method
A3：Ni x1 Co y1 M z1 M′ 1-x1-y1-z1 (OH) 2
A4：Ni x2 Co y2 M z2 M′ 1-x2-y2-z2 (OH) 2
wherein ,
m is one or two elements selected from Mn and Al,
m' is one or more elements selected from B, F, mg, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W,
0.30≤x1≤0.99，0≤y1≤0.30，0≤z1≤0.30，0≤1–x1–y1–z1≤0.10，
0.31≤x2≤1.00，0≤y2≤0.30，0≤z2≤0.30，0≤1–x2–y2–z2≤0.10，
the conditions are as follows: 0< x2-x1 is less than or equal to 0.5;
ii) mixing a lithium source with the polycrystalline particle precursor according to a molar ratio r1, optionally mixing M' as a doping element, wherein r1 is more than or equal to 0.97 and less than or equal to 1.20; then primary sintering is carried out in the sintering atmosphere of air or oxygen at the sintering temperature T1, wherein the temperature T1 is more than or equal to 600 ℃ and less than or equal to 1000 ℃; then crushing to obtain polycrystalline particles;
iii) Mixing a lithium source with the monocrystalline particle precursor according to a molar ratio r2, optionally mixing M' as a doping element, wherein r2 is more than or equal to 0.97 and less than or equal to 1.20; then primary sintering is carried out in the sintering atmosphere of air or oxygen at the sintering temperature T2, wherein T2 is more than or equal to 650 ℃ and less than or equal to 1050 ℃; then crushing to obtain monocrystalline particles; and
iv) blending the polycrystalline particles of step ii) with the single crystal particles of step iii) to obtain the positive electrode active material.
In still another aspect, the present application also provides a lithium secondary battery comprising the positive electrode active material according to the present application or the positive electrode active material prepared by the preparation method according to the present application.
Drawings
FIGS. 1 to 3 are SEM photographs showing the large polycrystalline particles A1 and small single crystal particles A2 of example 1, respectively, after being mixed together;
fig. 4 shows charge and discharge curves of example 1, comparative example 1, and comparative example 2; and
Fig. 5 shows cycle life of example 1, comparative example 1, and comparative example 2.
Detailed Description
Unless otherwise indicated, all publications, patent applications, patents, and other references mentioned herein are expressly incorporated by reference in their entirety for all purposes as if fully set forth.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.
If an amount, concentration, or other value or parameter is given as either a range, preferred range, or a series of upper preferable and lower preferable ranges, then this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of values is recited herein, unless otherwise stated, it is intended that the range includes the endpoints thereof, and all integers and fractions within the range.
In one aspect, the present invention relates to a positive electrode active material for a lithium secondary battery, characterized in that the positive electrode active material comprises polycrystalline particles represented by formula A1 and single crystal particles represented by formula A2
A1：Li 1+a1 Ni x1 Co y1 M z1 M′ 1-x1-y1-z1 O 2
A2：Li 1+a2 Ni x2 Co y2 M z2 M′ 1-x2-y2-z2 O 2
wherein ,
m is one or two elements selected from Mn and Al,
m' is one or more elements selected from B, F, mg, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W,
-0.03.ltoreq.a1.ltoreq.0.20, preferably-0.01.ltoreq.a1.ltoreq.0.14, more preferably 0.ltoreq.a1.ltoreq.0.10, particularly preferably 0.01.ltoreq.a1.ltoreq.0.08,
0.30.ltoreq.x1.ltoreq.0.99, preferably 0.57.ltoreq.x1.ltoreq.0.99, more preferably 0.72.ltoreq.x1.ltoreq.0.99, particularly preferably 0.80.ltoreq.x1.ltoreq.0.99,
y1 is more than or equal to 0 and less than or equal to 0.30, preferably y1 is more than or equal to 0 and less than or equal to 0.21, more preferably y1 is more than or equal to 0 and less than or equal to 0.15, particularly preferably y1 is more than or equal to 0 and less than or equal to 0.10,
0.ltoreq.z1.ltoreq.0.30, preferably 0.ltoreq.z1.ltoreq.0.18, more preferably 0.ltoreq.z1.ltoreq.0.11, particularly preferably 0.ltoreq.z1.ltoreq.0.06,
0.ltoreq.1-x 1-y1-z 1.ltoreq.0.10, preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.08, more preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.05, particularly preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.03,
-0.03.ltoreq.a2.ltoreq.0.20, preferably-0.02.ltoreq.a2.ltoreq.0.16, more preferably-0.01.ltoreq.a2.ltoreq.0.14, particularly preferably 0.ltoreq.a2.ltoreq.0.08,
0.31.ltoreq.x2.ltoreq.1.00, preferably 0.59.ltoreq.x2.ltoreq.0.995, more preferably 0.75.ltoreq.x2.ltoreq.0.995, particularly preferably 0.81.ltoreq.x2.ltoreq.0.995,
y2 is 0.ltoreq.y2.ltoreq.0.30, preferably 0.ltoreq.y2.ltoreq.0.21, more preferably 0.ltoreq.y2.ltoreq.0.15, particularly preferably 0.ltoreq.y2.ltoreq.0.10,
0.ltoreq.z2.ltoreq.0.30, preferably 0.ltoreq.z2.ltoreq.0.18, more preferably 0.ltoreq.z2.ltoreq.0.11, particularly preferably 0.ltoreq.z2.ltoreq.0.08,
0.ltoreq.1-x 2-y2-z 2.ltoreq.0.10, preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.08, more preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.05, particularly preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.03,
the conditions are as follows: 0< x2-x1 is less than or equal to 0.5, preferably 0.01 is less than or equal to x2-x1 is less than or equal to 0.27, more preferably 0.01 is less than or equal to x2-x1 is less than or equal to 0.20, even more preferably 0.015 is less than or equal to x2-x1 is less than or equal to 0.20, and particularly preferably 0.02 is less than or equal to x2-x1 is less than or equal to 0.15.
According to one embodiment of the positive electrode active material according to the present invention, a2> a1, preferably 0.01.ltoreq.a2-a1.ltoreq.0.20, more preferably 0.01.ltoreq.a2-a1.ltoreq.0.12, particularly preferably 0.01.ltoreq.a2-a1.ltoreq.0.07, particularly preferably 0.01.ltoreq.a2-a1.ltoreq.0.04.
According to another embodiment of the positive electrode active material according to the present invention, the polycrystalline particles have a particle size D 50 From 6 to 30. Mu.m, preferably from 8 to 25. Mu.m, more preferably from 9 to 20. Mu.m, particularly preferably from 10 to 18. Mu.m.
According to another embodiment of the positive electrode active material according to the present invention, the single crystal particles have a particle size D 50 From 0.1 to 10. Mu.m, preferably from 0.5 to 8.0. Mu.m, more preferably from 1.0 to 6.0. Mu.m, particularly preferably from 1.5 to 4.5. Mu.m.
According to another embodiment of the positive electrode active material according to the present invention, the content of the polycrystalline particles is 20 to 90%, preferably 45 to 85%, more preferably 50 to 80%, particularly preferably 60 to 80%, and the content of the single crystal particles is 10 to 80%, preferably 10 to 70%, more preferably 15 to 60%, particularly preferably 20 to 40%, based on the weight of the positive electrode active material.
According to another embodiment of the positive electrode active material according to the present invention, the polycrystalline particles have a coating layer comprising at least one coating element selected from the group consisting of: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W, wherein the content of the coating element is from 0.1 to 2 mol%, preferably about 1 mol%, based on the polycrystalline particles; and/or the single crystal particles have a coating layer comprising at least one coating element selected from the group consisting of: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W, wherein the content of the coating element is from 0.1 to 2 mol%, preferably about 1 mol%, based on the single crystal particles; the conditions are as follows: the coating layer of the polycrystalline particles contains a coating element different from that of the coating layer of the single crystal particles.
According to another embodiment of the positive electrode active material according to the present invention, the positive electrode active material has a specific surface area BET before and after sintering at 600 ℃ in an air atmosphere for 8 hours Front part and BETRear part (S) The method meets the following conditions:
|BET rear part (S) –BET Front part |/BET Front part ≤50％，
Preferably is |BET Rear part (S) –BET Front part |/BET Front part ≤30％。
The invention uses monocrystalline particles with round surfaces and polycrystalline particles with high particle strength, and controls the material of the finished product to expose stable crystal structure in combination with the preferable blending proportion, so that the change rate of the surface pores of the finished product is lower in the further sintering process.
According to another embodiment of the positive electrode active material according to the present invention, the polycrystalline particles are sintered at 600 ℃ in an air atmosphere for a specific surface area BET before and after 8 hours Front part and BETRear part (S) The method meets the following conditions:
(BET rear part (S) –BET Front part )/BET Front part ≥15％，
Preferably 40%. Gtoreq. (BET) Rear part (S) –BET Front part )/BET Front part ≥20％。
The polycrystalline particles are composed of a plurality of nano-scale particles, and in order to maintain good circulation performance, the gaps on the surfaces of the nano-particles cannot be excessive, and the BET of the material needs to be controlled within a certain range. In general, the BET of the material is further reduced through high-temperature sintering, but the invention can play a good role in protecting the surface interface by controlling the crystallinity and the orientation of nano grains on the surface of the material and combining with the surface treatment in an in-situ molten state, and the BET of the surface of the material is unexpectedly found to be not reduced and reversely increased. The inventors have further found that polycrystalline particles having such surface BET properties, when blended with single crystal particles, the cathode materials exhibit superior compression resistance characteristics and better discharge capacity and cycle performance.
According to another embodiment of the positive electrode active material according to the present invention, the single crystal particles are sintered at 600 ℃ in an air atmosphere for about 8 hoursArea BET Front part and BETRear part (S) The method meets the following conditions:
(BET front part –BET Rear part (S) )/BET Front part ≤15％，
Preferably 0.ltoreq.BET Front part –BET Rear part (S) )/BET Front part ≤10％。
The single crystal particles have the characteristics of good crystallinity, round surface and the like, so that the structure of the single crystal particles is stable, the material does not collapse or close to a great extent in the high-temperature sintering process, and the BET change of the single crystal particles relative to that of an unsintered material is small.
According to another embodiment of the positive electrode active material according to the present invention, the positive electrode active material does not contain a nickel-free active material, such as lithium manganese iron phosphate.
According to another embodiment of the positive electrode active material according to the present invention, the positive electrode active material is composed of polycrystalline particles represented by formula A1 and single crystal particles represented by formula A2.
In another aspect, the present invention also relates to a method of preparing a positive electrode active material, comprising the steps of:
i) Preparing polycrystalline particle precursor represented by formula A3 and monocrystalline particle precursor represented by formula A4 by liquid phase coprecipitation method
A3：Ni x1 Co y1 M z1 M′ 1-x1-y1-z1 (OH) 2
A4：Ni x2 Co y2 M z2 M′ 1-x2-y2-z2 (OH) 2
wherein ,
m is one or two elements selected from Mn and Al,
M' is one or more elements selected from B, F, mg, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W,
0.30.ltoreq.x1.ltoreq.0.99, preferably 0.57.ltoreq.x1.ltoreq.0.99, more preferably 0.72.ltoreq.x1.ltoreq.0.99, particularly preferably 0.80.ltoreq.x1.ltoreq.0.99,
y1 is more than or equal to 0 and less than or equal to 0.30, preferably y1 is more than or equal to 0 and less than or equal to 0.21, more preferably y1 is more than or equal to 0 and less than or equal to 0.15, particularly preferably y1 is more than or equal to 0 and less than or equal to 0.10,
0.ltoreq.z1.ltoreq.0.30, preferably 0.ltoreq.z1.ltoreq.0.18, more preferably 0.ltoreq.z1.ltoreq.0.11, particularly preferably 0.ltoreq.z1.ltoreq.0.06,
0.ltoreq.1-x 1-y1-z 1.ltoreq.0.10, preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.08, more preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.05, particularly preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.03,
0.31.ltoreq.x2.ltoreq.1.00, preferably 0.59.ltoreq.x2.ltoreq.0.995, more preferably 0.75.ltoreq.x2.ltoreq.0.995, particularly preferably 0.81.ltoreq.x2.ltoreq.0.995,
y2 is 0.ltoreq.y2.ltoreq.0.30, preferably 0.ltoreq.y2.ltoreq.0.21, more preferably 0.ltoreq.y2.ltoreq.0.15, particularly preferably 0.ltoreq.y2.ltoreq.0.10,
0.ltoreq.z2.ltoreq.0.30, preferably 0.ltoreq.z2.ltoreq.0.18, more preferably 0.ltoreq.z2.ltoreq.0.11, particularly preferably 0.ltoreq.z2.ltoreq.0.08,
0.ltoreq.1-x 2-y2-z 2.ltoreq.0.10, preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.08, more preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.05, particularly preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.03,
The conditions are as follows: 0< x2-x1 is less than or equal to 0.5, preferably 0.01 is less than or equal to x2-x1 is less than or equal to 0.27, more preferably 0.01 is less than or equal to x2-x1 is less than or equal to 0.20, even more preferably 0.015 is less than or equal to x2-x1 is less than or equal to 0.20, and particularly preferably 0.02 is less than or equal to x2-x1 is less than or equal to 0.15;
ii) mixing a lithium source with the polycrystalline particle precursor in a molar ratio r1, optionally M'
As the doping element, 0.97.ltoreq.r1.ltoreq.1.20, preferably 0.99.ltoreq.r1.ltoreq.1.14, more preferably 1.00.ltoreq.r1.ltoreq.1.10, particularly preferably 1.01.ltoreq.r1.ltoreq.1.08; then primary sintering is carried out at a sintering temperature T1 in air or in an oxygen, preferably oxygen sintering atmosphere, wherein 600 ℃ C.ltoreq.T1.ltoreq.1000 ℃, preferably 675 ℃ C.ltoreq.T1.ltoreq.875 ℃, more preferably 690 ℃ C.ltoreq.T1.ltoreq.800 ℃, particularly preferably 690 ℃ C.ltoreq.T1.ltoreq.780 ℃; then crushing to obtain polycrystalline particles;
iii) Mixing a lithium source with the single crystal particle precursor according to a molar ratio r2, optionally mixing M' as a doping element, wherein r2 is more than or equal to 0.97 and less than or equal to 1.20, preferably r2 is more than or equal to 0.98 and less than or equal to 1.16, more preferably r2 is more than or equal to 0.99 and less than or equal to 1.14, and particularly preferably r2 is more than or equal to 1.00 and less than or equal to 1.08; then primary sintering is carried out at a sintering temperature T2 in air or in an oxygen, preferably oxygen sintering atmosphere, wherein T2 is 650 ℃ to 1050 ℃, preferably 730 ℃ to T2 to 930 ℃, more preferably 750 ℃ to T2 to 930 ℃, particularly preferably 750 ℃ to T2 to 900 ℃; then crushing to obtain monocrystalline particles; and
iv) blending the polycrystalline particles of step ii) with the single crystal particles of step iii) to obtain the positive electrode active material.
According to one embodiment of the process according to the invention, r2> r1, preferably 0.01.ltoreq.r2-r1.ltoreq.0.20, more preferably 0.01.ltoreq.r2-r1.ltoreq.0.12, particularly preferably 0.01.ltoreq.r2-r1.ltoreq.0.07, particularly preferably 0.01.ltoreq.r2-r1.ltoreq.0.04.
According to another embodiment of the method according to the invention, the polycrystalline particle precursor has a particle size D 50 From 6.5 to 30.5. Mu.m, preferably from 8.5 to 25.5. Mu.m, more preferably from 9.5 to 20.5. Mu.m, particularly preferably from 10.5 to 18.5. Mu.m. Particle size D of the polycrystalline particles 50 From 6 to 30. Mu.m, preferably from 8 to 25. Mu.m, more preferably from 9 to 20. Mu.m, particularly preferably from 10 to 18. Mu.m.
According to another embodiment of the method according to the invention, the particle size D of the monocrystalline particle precursor 50 From 0.1 to 30.5. Mu.m, preferably from 1.0 to 17.3. Mu.m, more preferably from 1.0 to 9.3. Mu.m, particularly preferably from 1.0 to 6.0. Mu.m. Particle size D of the monocrystalline particles 50 From 0.1 to 10. Mu.m, preferably from 0.5 to 8.0. Mu.m, more preferably from 1.0 to 6.0. Mu.m, particularly preferably from 1.5 to 4.5. Mu.m.
According to another embodiment of the method according to the present invention, the content of the polycrystalline particles is 20 to 90%, preferably 45 to 85%, more preferably 50 to 80%, particularly preferably 60 to 80%, and the content of the single crystal particles is 10 to 80%, preferably 10 to 70%, more preferably 15 to 60%, particularly preferably 20 to 40%, based on the weight of the positive electrode active material.
According to another embodiment of the method according to the invention, prior to step iv), the polycrystalline granules are mixed with a coating precursor comprising at least one coating element selected from the group consisting of: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W and then secondary sintering at a sintering temperature T3 in air or in an oxygen, preferably oxygen sintering atmosphere to give secondary sintered polycrystalline particles, wherein 250 ℃ C. Ltoreq.T3.ltoreq.800 ℃, preferably 250 ℃ C. Ltoreq.T3.ltoreq.600 ℃, more preferably 250 ℃ C. Ltoreq.T3.ltoreq.480 ℃, particularly preferably 250 ℃ C. Ltoreq.T3.ltoreq.400 ℃, wherein the content of the coating element is 0.1 to 2 mol%, preferably about 1 mol%, based on the polycrystalline particles; and/or mixing the monocrystalline particles with a coating precursor comprising at least one coating element selected from the group consisting of: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W and then secondary sintering at a sintering temperature T4 in air or in an oxygen, preferably oxygen sintering atmosphere to give secondary sintered monocrystalline particles, wherein 300 ℃ C.ltoreq.T4.ltoreq.900 ℃, preferably 460 ℃ C.ltoreq.T4.ltoreq.800 ℃, more preferably 550 ℃ C.ltoreq.T4.ltoreq.750 ℃, particularly preferably 600 ℃ C.ltoreq.T4.ltoreq.750 ℃, wherein the content of the coating element is 0.1 to 2 mol%, preferably about 1 mol%, based on the monocrystalline particles; the conditions are as follows: the coating precursor of the polycrystalline particles comprises a coating element different from the coating element of the coating precursor of the monocrystalline particles.
In another aspect, the present invention also relates to a lithium secondary battery comprising the positive electrode active material according to the present invention or the positive electrode active material prepared by the preparation method according to the present invention.
Examples
Example 1
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 750 ℃, crushing the materials after sintering, and adding boric acid containing B1mol% into the crushed materials for carrying outSecond sintering, wherein the sintering temperature is 400 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material, as shown in FIG. 1. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a change rate of 35%.
LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 812 ℃, crushing the materials after sintering, and adding Al containing Al 1mol percent into the crushed materials 2 O 3 Then the second sintering is carried out, the sintering temperature is 620 ℃, and finally D is obtained 50 Is a 3.5 μm single crystal small particle material, as shown in FIG. 2. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
The above-mentioned polycrystalline large particles and single-crystal small particles were mixed in a mass ratio of 7:3 to obtain a positive electrode active material for a lithium secondary battery, as shown in fig. 3. The positive electrode active material was treated at 600 ℃ for 8 hours, and the BET change rate thereof was increased by 24%.
Example 2
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.06, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 745 ℃, crushing the materials after sintering, adding boric acid containing 0.8mol% of B into the crushed materials for the second sintering at a sintering temperature of 380 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a 24% change rate.
LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 812 ℃, and sintering the materialsCrushing, and adding Al containing Al 1.2mol% 2 O 3 Then the second sintering is carried out, the sintering temperature is 610 ℃, and finally D is obtained 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 3%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to a mass ratio of 8:2 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and the BET change rate thereof was increased by 19%.
Example 3
First, singly preparing Ni by liquid phase coprecipitation method 0.86 Co 0.11 Mn 0.03 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.88 Co 0.08 Mn 0.04 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.86 Co 0.11 Mn 0.03 (OH) 2 Mixing according to a molar ratio of 1.06, sintering the mixed materials for the first time in an oxygen atmosphere at 725 ℃, crushing the materials after sintering, adding boric acid containing 0.8mol% of B into the crushed materials for the second sintering at 380 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a 26% change rate.
LiOH and Ni 0.88 Co 0.08 Mn 0.04 (OH) 2 Mixing according to a molar ratio of 1.11, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 805 ℃, crushing the materials after sintering, and adding Al containing Al 1.0mol% into the crushed materials 2 O 3 Then the second sintering is carried out, the sintering temperature is 610 ℃, and finally D is obtained 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and the BET change rate thereof was increased by 20%.
Example 4
First, singly preparing Ni by liquid phase coprecipitation method 0.86 Co 0.11 Mn 0.03 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.88 Co 0.08 Mn 0.04 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.86 Co 0.11 Mn 0.03 (OH) 2 Mixing according to a molar ratio of 1.06, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 685 ℃, crushing the materials after sintering, adding boric acid containing 0.8mol% of B into the crushed materials for the second sintering at a sintering temperature of 380 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a 26% change rate.
LiOH and Ni 0.88 Co 0.08 Mn 0.04 (OH) 2 Mixing according to a molar ratio of 1.11, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 805 ℃, crushing the materials after sintering, and adding Al containing Al 1.0mol% into the crushed materials 2 O 3 Then the second sintering is carried out, the sintering temperature is 610 ℃, and finally D is obtained 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to a mass ratio of 3:7 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and the BET change rate thereof was increased by 6%.
Example 5
First, singly preparing Ni by liquid phase coprecipitation method 0.88 Co 0.10 Mn 0.02 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.90 Co 0.08 Mn 0.02 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.88 Co 0.10 Mn 0.02 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at 780 ℃, crushing the materials after sintering, adding boric acid containing B1mol% into the crushed materials for the second sintering at 400 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a 32% change rate.
LiOH and Ni 0.90 Co 0.08 Mn 0.02 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 812 ℃, crushing the materials after sintering, and adding Al containing Al 1mol percent into the crushed materials 2 O 3 Then the second sintering is carried out, the sintering temperature is 620 ℃, and finally D is obtained 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and the BET change rate thereof was increased by 22%.
Example 6
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 750 ℃, crushing the materials after sintering, adding boric acid containing B1mol% into the crushed materials for the second sintering at a sintering temperature of 400 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a change rate of 35%.
LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 812 ℃, crushing the materials after sintering, sintering the crushed materials for the second time after boric acid with B of 0.4mol percent and sintering at a sintering temperature of 400 ℃ to finally obtain D 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with an increase in BET and a 9% change rate.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600℃for 8 hours, and the BET change rate thereof was increased by 27%.
Example 7
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 750 ℃, crushing the materials after sintering, adding boric acid containing 0.5mol% of B into the crushed materials for the second sintering at a sintering temperature of 400 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a change of 11%.
LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 812 ℃, crushing the materials after sintering, and adding Al containing Al 1mol percent into the crushed materials 2 O 3 Then the second sintering is carried out, the sintering temperature is 620 ℃, and finally D is obtained 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and the BET change rate thereof was increased by 7%.
Example 8
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 750 ℃, crushing the materials after sintering, and adding Al containing Al 1 mol%into the crushed materials 2 O 3 Performing second sintering at 620 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with a BET reduction of 3%.
LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 812 ℃, crushing the materials after sintering, and adding Al containing Al 1mol percent into the crushed materials 2 O 3 Then the second sintering is carried out, the sintering temperature is 620 ℃, and finally D is obtained 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and the BET change rate thereof was reduced by 3%.
Example 9
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor andthe composition is Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 750 ℃, crushing the materials after sintering, adding boric acid containing 0.5mol% of B into the crushed materials for the second sintering at a sintering temperature of 400 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a change of 11%.
LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 812 ℃, crushing the materials after sintering, sintering the crushed materials for the second time after boric acid with B of 0.4mol percent and sintering at a sintering temperature of 400 ℃ to finally obtain D 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with an increase in BET and a 9% change rate.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600℃for 8 hours, and the BET change rate thereof was increased by 10%.
Example 10
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.84 Co 0.08 Mn 0.08 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 750 ℃, crushing the materials after sintering, adding boric acid containing 0.5mol% of B into the crushed materials for the second sintering at a sintering temperature of 400 ℃ to obtain D 50 10.0 mum polycrystalline large particulate material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a change rate of 35%.
LiOH and Ni 0.84 Co 0.08 Mn 0.08 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 812 ℃, crushing the materials after sintering, sintering the crushed materials for the second time after boric acid with B of 0.4mol percent and sintering at a sintering temperature of 400 ℃ to finally obtain D 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and the BET change rate thereof was increased by 24%.
Comparative example 1
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.80 Co 0.11 Mn 0.09 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 750 ℃, crushing the materials after sintering, adding boric acid containing B1mol% into the crushed materials for the second sintering at a sintering temperature of 400 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a change rate of 35%.
LiOH and Ni 0.80 Co 0.11 Mn 0.09 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 820 ℃, crushing the materials after sintering, and adding Al containing Al 1 mol%into the crushed materials 2 O 3 Then the second sintering is carried out, the sintering temperature is 620 ℃, and finally D is obtained 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and its BET increased by 25%.
Comparative example 2
First, singly preparing Ni by liquid phase coprecipitation method 0.83 Co 0.11 Mn 0.06 (OH) 2 10.5 μm polycrystalline positive electrode precursor and composition Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 A 4 μm single crystal positive electrode precursor of (a).
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.08, sintering the mixed materials for the first time in an oxygen atmosphere at a sintering temperature of 750 ℃, crushing the materials after sintering, adding boric acid containing B1mol% into the crushed materials for the second sintering at a sintering temperature of 400 ℃ to obtain D 50 Is a 10.0 μm polycrystalline large particle material. The polycrystalline material was treated at 600 ℃ for 8 hours with an increase in BET and a change rate of 35%.
LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 Mixing according to a molar ratio of 1.12, sintering the mixed materials for the first time in an oxygen atmosphere at 816 ℃, crushing the materials after sintering, and adding Al containing Al 1 mol%into the crushed materials 2 O 3 Then the second sintering is carried out, the sintering temperature is 620 ℃, and finally D is obtained 50 Is 3.5 mu m single crystal small particle material. The single crystal material was treated at 600 ℃ for 8 hours with a BET reduction of 2%.
And mixing the polycrystalline large particles and the monocrystalline small particles according to the mass ratio of 7:3 to obtain the positive electrode active material for the lithium secondary battery. The positive electrode active material was treated at 600 ℃ for 8 hours, and its BET increased by 25%.
Specific surface area measurement:
the test was performed using a Tri-star 3020 specific surface meter, 3 grams of sample were weighed and the sample tube was mounted onto a vacuum fitting on the degas station port. Setting the heating temperature at 300 ℃, and degassing for 120min, and cooling the sample tube after the degassing is finished. Inputting the mass of an empty sample tube and the mass of the sample and the sample tube after degassing at a software interface of the tester, recording the specific surface area data (BET method) output after software calculation, and completing the test of the specific surface area of the sample of the positive electrode material;
particle size measurement:
testing was performed using a Mastersizer2000 laser particle sizer. Modifying the sample test time and background test time of the test times item in the measurement in the software to be 6 seconds; the number of cycles of the measurement cycle term was 3, the delay time was 5 seconds, and clicks created an average result record from the measurement. Secondly, clicking the start to automatically measure the background; after the automatic measurement is completed, 40 ml of sodium pyrophosphate is added, then a small amount of sample is added by using a medicine spoon until the shading degree reaches 1/2 of the visual 10-20% area, the start is clicked, and the three results and the average value are finally recorded. Preparing a button cell:
First, a composite nickel-cobalt-manganese multi-element positive electrode active material for a nonaqueous electrolyte secondary battery, acetylene black and polyvinylidene fluoride (PVDF) were mixed, coated on an aluminum foil, and subjected to a baking treatment. And assembling the dried positive electrode plate, the dried diaphragm, the dried negative electrode plate and the electrolyte into a 2025 type button cell in an Ar gas glove box with water content and oxygen content of less than 5 ppm.
The first discharge capacity test method comprises the following steps: after the button cell is manufactured and placed for 2 hours, after the open circuit voltage is stable, charging the positive electrode to the cut-off voltage of 4.3V in a mode that the current density of the positive electrode is 0.1C, then charging the battery for 30 minutes at a constant voltage, and then discharging the battery to the cut-off voltage of 3.0V at the same current density; the discharge capacity was further 1 time in the same manner, and was regarded as the first discharge capacity. Fig. 4 shows charge and discharge curves of the button cells prepared from the positive electrode materials of example 1 and comparative examples 1 and 2, and it can be seen that the positive electrode material of example 1 has a higher first discharge capacity than that of the comparative example.
Preparing a full battery and testing gas production:
and (3) putting the nickel cobalt lithium manganate positive electrode material, the graphite negative electrode material, the carbon black conductive agent and the binder PVDF into a vacuum oven at 120 ℃ to dry for 12 hours. And uniformly mixing the dried positive electrode material, the carbon black conductive agent, PVDF and NMP to prepare positive electrode slurry. The slurry is coated on aluminum foil by a lithium battery coating machine and dried, a pole piece is cut by a pole piece dividing and cutting machine, and a pole piece roller press is used for rolling the pole piece.
950 grams of dried artificial graphite, 13 grams of Super-P, 14 grams of CMC, 46 grams of SBR solution and 1200 grams of deionized water are uniformly mixed to prepare negative electrode slurry. The slurry was coated onto copper foil using a lithium battery coater and dried. And drying the coated negative electrode sheet by using a vacuum oven, cutting the electrode sheet by using a pole piece dividing and cutting machine, and rolling the pole piece by using a pole piece roller press.
And winding the positive plate and the negative plate by adopting a conventional manufacturing method, and injecting electrolyte to manufacture the full battery. The initial thickness of the full cell after formation was measured, and after 7 days of standing in a 45 ℃ incubator, the full cell thickness was again tested, and the rate of increase of the thickness was used to characterize the gassing of the positive electrode material in the full cell. Fig. 5 shows the cycle life changes of the full cells made of the positive electrode materials in example 1 and comparative examples 1 and 2, and it can be seen that the full cells made of the positive electrode materials in example 1 have better stability and longer cycle life.
The positive electrode active material and the lithium ion battery provided by the invention have the following beneficial effects:
1) Compared with the polycrystalline material, the monocrystal with the same nickel content has better cycle life and lower gas production performance, so that the addition of the monocrystal can effectively improve the performances of the mixed material such as cycle, gas production and the like;
2) The single crystal material has a special single crystal morphology, and gram capacity is lower than that of the polycrystal with the same nickel content, so that the single crystal with slightly higher nickel content is adopted to make up a short plate with low gram capacity, and the performances of circulation, gas production and the like of the single crystal material are kept at the same level with the polycrystal with low nickel content;
3) The mixed small-particle monocrystalline material can enter gaps among large polycrystalline particles to form a synergistic effect of mutual support and gap filling with the large-particle polycrystalline particles, so that the compaction density of the material is effectively improved;
4) A small amount of large-particle-size polycrystalline spherical particles are added into a system mainly comprising small monocrystalline particles, so that the problems of poor flowability, difficulty in screening, pulping and the like of monocrystalline materials can be effectively solved.
While specific embodiments have been described, these embodiments are presented by way of example only and are not meant to limit the scope of the invention. It is intended that the appended claims and equivalents thereof cover all modifications, alternatives, and variations that fall within the scope and spirit of the present invention.
Claims (28)
1. A positive electrode active material for a lithium secondary battery, characterized in that the positive electrode active material comprises polycrystalline particles represented by formula A1 and single crystal particles represented by formula A2
A1：Li 1+a1 Ni x1 Co y1 M z1 M′ 1-x1-y1-z1 O 2
A2：Li 1+a2 Ni x2 Co y2 M z2 M′ 1-x2-y2-z2 O 2
wherein ,
M is one or two elements selected from Mn and Al,
m' is one or more elements selected from B, F, mg, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W,
-0.03.ltoreq.a1.ltoreq.0.20, preferably-0.01.ltoreq.a1.ltoreq.0.14, more preferably 0.ltoreq.a1.ltoreq.0.10, particularly preferably 0.01.ltoreq.a1.ltoreq.0.08,
0.30.ltoreq.x1.ltoreq.0.99, preferably 0.57.ltoreq.x1.ltoreq.0.99, more preferably 0.72.ltoreq.x1.ltoreq.0.99, particularly preferably 0.80.ltoreq.x1.ltoreq.0.99,
y1 is more than or equal to 0 and less than or equal to 0.30, preferably y1 is more than or equal to 0 and less than or equal to 0.21, more preferably y1 is more than or equal to 0 and less than or equal to 0.15, particularly preferably y1 is more than or equal to 0 and less than or equal to 0.10,
0.ltoreq.z1.ltoreq.0.30, preferably 0.ltoreq.z1.ltoreq.0.18, more preferably 0.ltoreq.z1.ltoreq.0.11, particularly preferably 0.ltoreq.z1.ltoreq.0.06,
0.ltoreq.1-x 1-y1-z 1.ltoreq.0.10, preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.08, more preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.05, particularly preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.03,
-0.03.ltoreq.a2.ltoreq.0.20, preferably-0.02.ltoreq.a2.ltoreq.0.16, more preferably-0.01.ltoreq.a2.ltoreq.0.14, particularly preferably 0.ltoreq.a2.ltoreq.0.08,
0.31.ltoreq.x2.ltoreq.1.00, preferably 0.59.ltoreq.x2.ltoreq.0.995, more preferably 0.75.ltoreq.x2.ltoreq.0.995, particularly preferably 0.81.ltoreq.x2.ltoreq.0.995,
y2 is 0.ltoreq.y2.ltoreq.0.30, preferably 0.ltoreq.y2.ltoreq.0.21, more preferably 0.ltoreq.y2.ltoreq.0.15, particularly preferably 0.ltoreq.y2.ltoreq.0.10,
0.ltoreq.z2.ltoreq.0.30, preferably 0.ltoreq.z2.ltoreq.0.18, more preferably 0.ltoreq.z2.ltoreq.0.11, particularly preferably 0.ltoreq.z2.ltoreq.0.08,
0.ltoreq.1-x 2-y2-z 2.ltoreq.0.10, preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.08, more preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.05, particularly preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.03,
the conditions are as follows: 0< x2-x1 is less than or equal to 0.5, preferably 0.01 is less than or equal to x2-x1 is less than or equal to 0.27, more preferably 0.01 is less than or equal to x2-x1 is less than or equal to 0.20, even more preferably 0.015 is less than or equal to x2-x1 is less than or equal to 0.20, and particularly preferably 0.02 is less than or equal to x2-x1 is less than or equal to 0.15.
2. The positive electrode active material according to claim 1, wherein a2> a1, preferably 0.01.ltoreq.a2-a1.ltoreq.0.20, more preferably 0.01.ltoreq.a2-a1.ltoreq.0.12, particularly preferably 0.01.ltoreq.a2-a1.ltoreq.0.07, particularly preferably 0.01.ltoreq.a2-a1.ltoreq.0.04.
3. The positive electrode active material according to claim 1 or 2, wherein the polycrystalline particles have a particle size D 50 From 6 to 30. Mu.m, preferably from 8 to 25. Mu.m, more preferably from 9 to 20. Mu.m, particularly preferably10 to 18 μm.
4. A positive electrode active material according to any one of claims 1 to 3, wherein the single crystal particles have a particle size D 50 From 0.1 to 10. Mu.m, preferably from 0.5 to 8.0. Mu.m, more preferably from 1.0 to 6.0. Mu.m, particularly preferably from 1.5 to 4.5. Mu.m.
5. The positive electrode active material according to one of claims 1 to 4, characterized in that the content of the polycrystalline particles is 20 to 90%, preferably 45 to 85%, more preferably 50 to 80%, particularly preferably 60 to 80%, based on the weight of the positive electrode active material.
6. The positive electrode active material according to one of claims 1 to 5, characterized in that the content of the single crystal particles is 10 to 80%, preferably 10 to 70%, more preferably 15 to 60%, particularly preferably 20 to 40% based on the weight of the positive electrode active material.
7. The positive electrode active material according to any one of claims 1 to 6, wherein the polycrystalline particles have a coating layer containing at least one coating element selected from the group consisting of: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W, wherein the content of the coating element is 0.1 to 2 mol%, preferably about 1 mol%, based on the polycrystalline particles.
8. The positive electrode active material according to one of claims 1 to 7, wherein the single crystal particles have a coating layer containing at least one coating element selected from the group consisting of: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W, wherein the content of the coating element is 0.1 to 2 mol%, preferably about 1 mol%, based on the single crystal particles.
9. The positive electrode active material according to one of claims 1 to 8, wherein the polycrystalline particles and the single crystal particles each have a coating layer containing at least one coating element selected from the group consisting of: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W, wherein the content of the coating element is 0.1 to 2 mol%, preferably about 1 mol%, based on the polycrystalline particles and the monocrystalline particles, respectively.
10. The positive electrode active material according to claim 9, wherein the coating layer of the polycrystalline particles contains a coating element different from that of the coating layer of the single crystal particles.
11. The positive electrode active material according to any one of claims 1 to 10, characterized in that the positive electrode active material has a specific surface area BET before and after sintering at 600 ℃ in an air atmosphere for 8 hours Front part and BETRear part (S) The method meets the following conditions:
|BET rear part (S) –BET Front part |/BET Front part ≤50％，
Preferably is |BET Rear part (S) –BET Front part |/BET Front part ≤30％。
12. The positive electrode active material according to any one of claims 1 to 11, wherein the polycrystalline particles have a specific surface area BET before and after sintering at 600 ℃ in an air atmosphere for 8 hours Front part and BETRear part (S) The method meets the following conditions:
(BET rear part (S) –BET Front part )/BET Front part ≥15％，
Preferably 40%. Gtoreq. (BET) Rear part (S) –BET Front part )/BET Front part ≥20％。
13. The positive electrode active material according to any one of claims 1 to 12, wherein the single crystal particles have a specific surface area BET before and after sintering at 600 ℃ in an air atmosphere for 8 hours Front part and BETRear part (S) The method meets the following conditions:
(BET front part –BET Rear part (S) )/BET Front part ≤15％，
Preferably 0.ltoreq.BET Front part –BET Rear part (S) )/BET Front part ≤10％。
14. The positive electrode active material according to one of claims 1 to 13, characterized in that the positive electrode active material does not contain a nickel-free active material, such as lithium manganese iron phosphate.
15. The positive electrode active material according to one of claims 1 to 14, characterized in that the positive electrode active material is composed of polycrystalline particles represented by formula A1 and single crystal particles represented by formula A2.
16. A method of preparing a positive electrode active material, comprising the steps of:
i) Preparing polycrystalline particle precursor represented by formula A3 and monocrystalline particle precursor represented by formula A4 by liquid phase coprecipitation method
A3：Ni x1 Co y1 M z1 M′ 1-x1-y1-z1 (OH) 2
A4：Ni x2 Co y2 M z2 M′ 1-x2-y2-z2 (OH) 2
wherein ,
m is one or two elements selected from Mn and Al,
m' is one or more elements selected from B, F, mg, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W,
0.30.ltoreq.x1.ltoreq.0.99, preferably 0.57.ltoreq.x1.ltoreq.0.99, more preferably 0.72.ltoreq.x1.ltoreq.0.99, particularly preferably 0.80.ltoreq.x1.ltoreq.0.99,
Y1 is more than or equal to 0 and less than or equal to 0.30, preferably y1 is more than or equal to 0 and less than or equal to 0.21, more preferably y1 is more than or equal to 0 and less than or equal to 0.15, particularly preferably y1 is more than or equal to 0 and less than or equal to 0.10,
0.ltoreq.z1.ltoreq.0.30, preferably 0.ltoreq.z1.ltoreq.0.18, more preferably 0.ltoreq.z1.ltoreq.0.11, particularly preferably 0.ltoreq.z1.ltoreq.0.06,
0.ltoreq.1-x 1-y1-z 1.ltoreq.0.10, preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.08, more preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.05, particularly preferably 0.ltoreq.1-x 1-y1-z 1.ltoreq.0.03,
0.31.ltoreq.x2.ltoreq.1.00, preferably 0.59.ltoreq.x2.ltoreq.0.995, more preferably 0.75.ltoreq.x2.ltoreq.0.995, particularly preferably 0.81.ltoreq.x2.ltoreq.0.995,
y2 is 0.ltoreq.y2.ltoreq.0.30, preferably 0.ltoreq.y2.ltoreq.0.21, more preferably 0.ltoreq.y2.ltoreq.0.15, particularly preferably 0.ltoreq.y2.ltoreq.0.10,
0.ltoreq.z2.ltoreq.0.30, preferably 0.ltoreq.z2.ltoreq.0.18, more preferably 0.ltoreq.z2.ltoreq.0.11, particularly preferably 0.ltoreq.z2.ltoreq.0.08,
0.ltoreq.1-x 2-y2-z 2.ltoreq.0.10, preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.08, more preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.05, particularly preferably 0.ltoreq.1-x 2-y2-z 2.ltoreq.0.03,
the conditions are as follows: 0< x2-x1 is less than or equal to 0.5, preferably 0.01 is less than or equal to x2-x1 is less than or equal to 0.27, more preferably 0.01 is less than or equal to x2-x1 is less than or equal to 0.20, even more preferably 0.015 is less than or equal to x2-x1 is less than or equal to 0.20, and particularly preferably 0.02 is less than or equal to x2-x1 is less than or equal to 0.15;
ii) mixing a lithium source with the polycrystalline particle precursor in a molar ratio r1, optionally mixing M' as doping element, wherein 0.97.ltoreq.r1.ltoreq.1.20, preferably 0.99.ltoreq.r1.ltoreq.1.14, more preferably 1.00.ltoreq.r1.ltoreq.1.10, particularly preferably 1.01.ltoreq.r1.ltoreq.1.08; then primary sintering is carried out at a sintering temperature T1 in air or in an oxygen, preferably oxygen sintering atmosphere, wherein 600 ℃ C.ltoreq.T1.ltoreq.1000 ℃, preferably 675 ℃ C.ltoreq.T1.ltoreq.875 ℃, more preferably 690 ℃ C.ltoreq.T1.ltoreq.800 ℃, particularly preferably 690 ℃ C.ltoreq.T1.ltoreq.780 ℃; then crushing to obtain polycrystalline particles;
iii) Mixing a lithium source with the single crystal particle precursor according to a molar ratio r2, optionally mixing M' as a doping element, wherein r2 is more than or equal to 0.97 and less than or equal to 1.20, preferably r2 is more than or equal to 0.98 and less than or equal to 1.16, more preferably r2 is more than or equal to 0.99 and less than or equal to 1.14, and particularly preferably r2 is more than or equal to 1.00 and less than or equal to 1.08; then primary sintering is carried out at a sintering temperature T2 in air or in an oxygen, preferably oxygen sintering atmosphere, wherein T2 is 650 ℃ to 1050 ℃, preferably 730 ℃ to T2 to 930 ℃, more preferably 750 ℃ to T2 to 930 ℃, particularly preferably 750 ℃ to T2 to 900 ℃; then crushing to obtain monocrystalline particles; and
iv) blending the polycrystalline particles of step ii) with the single crystal particles of step iii) to obtain the positive electrode active material.
17. The method according to claim 16, characterized in that r2> r1, preferably 0.01.ltoreq.r2-r1.ltoreq.0.20, more preferably 0.01.ltoreq.r2-r1.ltoreq.0.12, particularly preferably 0.01.ltoreq.r2-r1.ltoreq.0.07, particularly preferably 0.01.ltoreq.r2-r1.ltoreq.0.04.
18. The method of claim 16 or 17, wherein the polycrystalline particle precursor has a particle size D 50 From 6.5 to 30.5. Mu.m, preferably from 8.5 to 25.5. Mu.m, more preferably from 9.5 to 20.5. Mu.m, particularly preferably from 10.5 to 18.5. Mu.m.
19. The method according to any one of claims 16 to 18, wherein the polycrystalline particles have a particle size D 50 From 6 to 30. Mu.m, preferably from 8 to 25. Mu.m, more preferably from 9 to 20. Mu.m, particularly preferably from 10 to 18. Mu.m.
20. The method according to one of claims 16 to 19, characterized in that the particle size D of the monocrystalline particle precursor 50 From 0.1 to 30.5. Mu.m, preferably from 1.0 to 17.3. Mu.m, more preferably from 1.0 to 9.3. Mu.m, particularly preferably from 1.0 to 6.0. Mu.m.
21. The method according to one of claims 16 to 20, characterized in that the single crystal particles have a particle size D 50 From 0.1 to 10. Mu.m, preferably from 0.5 to 8.0. Mu.m, more preferably from 1.0 to 6.0. Mu.m, particularly preferably from 1.5 to 4.5. Mu.m.
22. The method according to one of claims 16 to 21, characterized in that the content of the polycrystalline particles is 20 to 90%, preferably 45 to 85%, more preferably 50 to 80%, particularly preferably 60 to 80%, based on the weight of the positive electrode active material.
23. The method according to one of claims 16 to 22, characterized in that the content of single-crystal particles is 10 to 80%, preferably 10 to 70%, more preferably 15 to 60%, particularly preferably 20 to 40% based on the weight of the positive electrode active material.
24. The method according to one of claims 16 to 23, characterized in that prior to step iv) the polycrystalline granules are mixed with a coating precursor comprising at least one coating element selected from the group: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W and then secondary sintering at a sintering temperature T3 in air or in an oxygen, preferably oxygen sintering atmosphere to give secondary sintered polycrystalline particles, wherein 250 ℃ C.ltoreq.T3.ltoreq.800 ℃, preferably 250 ℃ C.ltoreq.T3.ltoreq.600 ℃, more preferably 250 ℃ C.ltoreq.T3.ltoreq.480 ℃, particularly preferably 250 ℃ C.ltoreq.T3.ltoreq.400 ℃, wherein the content of the coating element is 0.1 to 2 mol%, preferably about 1 mol%, based on the polycrystalline particles.
25. The method according to one of claims 16 to 24, characterized in that prior to step iv) the monocrystalline particles are mixed with a coating precursor comprising at least one coating element selected from the group: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W and then secondary sintering at a sintering temperature T4 in air or in an oxygen, preferably oxygen sintering atmosphere to give secondary sintered monocrystalline particles, wherein 300 ℃ C.ltoreq.T4.ltoreq.900 ℃, preferably 460 ℃ C.ltoreq.T4.ltoreq.800 ℃, more preferably 550 ℃ C.ltoreq.T4.ltoreq.750 ℃, particularly preferably 600 ℃ C.ltoreq.T4.ltoreq.750 ℃, wherein the content of the coating element is 0.1 to 2 mol%, preferably about 1 mol%, based on the monocrystalline particles.
26. The method according to one of claims 16 to 25, characterized in that prior to step iv) the polycrystalline granules are mixed with a coating precursor comprising at least one coating element selected from the group: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W and then secondary sintering at a sintering temperature T3 in air or in an oxygen, preferably oxygen sintering atmosphere to give secondary sintered polycrystalline particles, wherein 250 ℃ C. Ltoreq.T3.ltoreq.800 ℃, preferably 250 ℃ C. Ltoreq.T3.ltoreq.600 ℃, more preferably 250 ℃ C. Ltoreq.T3.ltoreq.480 ℃, particularly preferably 250 ℃ C. Ltoreq.T3.ltoreq.450 ℃, and additionally mixing the monocrystalline particles with a coating precursor comprising at least one coating element selected from the group: B. f, mg, al, si, P, ca, ti, V, cr, fe, ga, sr, Y, zr, nb, mo, sn, ba, la, ce, W and then secondary sintering at a sintering temperature T4 in air or in an oxygen, preferably oxygen sintering atmosphere to give secondary sintered monocrystalline particles, wherein 250 ℃ C.ltoreq.T4.ltoreq.900 ℃, preferably 250 ℃ C.ltoreq.T4.ltoreq.750 ℃, more preferably 250 ℃ C.ltoreq.T4.ltoreq.700 ℃, particularly preferably 300 ℃ C.ltoreq.T4.ltoreq.700 ℃, wherein the content of the coating element is 0.1 to 2 mol%, preferably about 1 mol%, based on the polycrystalline particles and the monocrystalline particles, respectively.
27. The method of claim 26, wherein the coating precursor of the polycrystalline particles comprises a coating element different from the coating element of the coating precursor of the monocrystalline particles.
28. A lithium secondary battery comprising the positive electrode active material according to one of claims 1 to 13 or the positive electrode active material produced by the method according to one of claims 16 to 27.
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| CN117276532A (en) * | 2023-11-21 | 2023-12-22 | 宜宾锂宝新材料有限公司 | High-tap-density positive electrode material, preparation method thereof and lithium battery |
| CN117410478A (en) * | 2023-12-11 | 2024-01-16 | 英德市科恒新能源科技有限公司 | Polycrystalline ternary positive electrode material, preparation method thereof and lithium ion battery |
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| CN117276532A (en) * | 2023-11-21 | 2023-12-22 | 宜宾锂宝新材料有限公司 | High-tap-density positive electrode material, preparation method thereof and lithium battery |
| CN117276532B (en) * | 2023-11-21 | 2024-03-29 | 宜宾锂宝新材料有限公司 | High-tap-density positive electrode material, preparation method thereof and lithium battery |
| CN117410478A (en) * | 2023-12-11 | 2024-01-16 | 英德市科恒新能源科技有限公司 | Polycrystalline ternary positive electrode material, preparation method thereof and lithium ion battery |
| CN117410478B (en) * | 2023-12-11 | 2024-03-29 | 英德市科恒新能源科技有限公司 | Polycrystalline ternary positive electrode material, preparation method thereof and lithium ion battery |
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