CN118213524A - Positive electrode material, preparation method thereof and lithium ion battery - Google Patents
Positive electrode material, preparation method thereof and lithium ion battery Download PDFInfo
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- 239000007774 positive electrode material Substances 0.000 title claims abstract description 169
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- 239000000463 material Substances 0.000 claims abstract description 92
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 238000005245 sintering Methods 0.000 claims description 59
- 238000005406 washing Methods 0.000 claims description 48
- 238000010438 heat treatment Methods 0.000 claims description 43
- 238000002156 mixing Methods 0.000 claims description 37
- 229910052708 sodium Inorganic materials 0.000 claims description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- 239000002243 precursor Substances 0.000 claims description 24
- 239000002245 particle Substances 0.000 claims description 22
- 229910052760 oxygen Inorganic materials 0.000 claims description 19
- 239000001301 oxygen Substances 0.000 claims description 19
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 18
- 238000009826 distribution Methods 0.000 claims description 17
- 238000001035 drying Methods 0.000 claims description 17
- 150000001875 compounds Chemical class 0.000 claims description 16
- 239000010406 cathode material Substances 0.000 claims description 15
- 229910003002 lithium salt Inorganic materials 0.000 claims description 14
- 159000000002 lithium salts Chemical class 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 13
- 238000000967 suction filtration Methods 0.000 claims description 11
- 239000011248 coating agent Substances 0.000 claims description 10
- 229910052700 potassium Inorganic materials 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 239000007788 liquid Substances 0.000 claims description 6
- 239000007790 solid phase Substances 0.000 claims description 6
- 238000000926 separation method Methods 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- 229910014638 LiaNib Inorganic materials 0.000 claims description 3
- 239000011538 cleaning material Substances 0.000 claims description 3
- 238000005108 dry cleaning Methods 0.000 claims description 3
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 abstract description 45
- 229910052723 transition metal Inorganic materials 0.000 abstract description 22
- 150000003624 transition metals Chemical class 0.000 abstract description 19
- 229910052759 nickel Inorganic materials 0.000 abstract description 18
- 230000014759 maintenance of location Effects 0.000 abstract description 16
- 238000007086 side reaction Methods 0.000 abstract description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 9
- 229910052744 lithium Inorganic materials 0.000 abstract description 9
- 238000013508 migration Methods 0.000 abstract description 5
- 230000005012 migration Effects 0.000 abstract description 5
- 210000004027 cell Anatomy 0.000 description 43
- 239000011734 sodium Substances 0.000 description 37
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 30
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 27
- 150000003839 salts Chemical class 0.000 description 23
- 230000000052 comparative effect Effects 0.000 description 22
- 238000005259 measurement Methods 0.000 description 19
- 238000001816 cooling Methods 0.000 description 17
- 238000012360 testing method Methods 0.000 description 17
- 239000010410 layer Substances 0.000 description 16
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 14
- 125000004122 cyclic group Chemical group 0.000 description 13
- 239000010405 anode material Substances 0.000 description 12
- 239000011572 manganese Substances 0.000 description 11
- 239000000126 substance Substances 0.000 description 11
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 10
- 229910017052 cobalt Inorganic materials 0.000 description 10
- GSOLWAFGMNOBSY-UHFFFAOYSA-N cobalt Chemical compound [Co][Co][Co][Co][Co][Co][Co][Co] GSOLWAFGMNOBSY-UHFFFAOYSA-N 0.000 description 10
- 239000010941 cobalt Substances 0.000 description 10
- 239000003792 electrolyte Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 239000003513 alkali Substances 0.000 description 7
- 229910000029 sodium carbonate Inorganic materials 0.000 description 7
- 238000004146 energy storage Methods 0.000 description 6
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 239000011591 potassium Substances 0.000 description 5
- -1 transition metal cations Chemical class 0.000 description 5
- 238000009792 diffusion process Methods 0.000 description 4
- 239000011777 magnesium Substances 0.000 description 4
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 238000009830 intercalation Methods 0.000 description 3
- 239000011229 interlayer Substances 0.000 description 3
- 229910052749 magnesium Inorganic materials 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 229910001413 alkali metal ion Inorganic materials 0.000 description 2
- 230000006399 behavior Effects 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 230000008093 supporting effect Effects 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 1
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 210000003850 cellular structure Anatomy 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910001947 lithium oxide Inorganic materials 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 229940031958 magnesium carbonate hydroxide Drugs 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910001453 nickel ion Inorganic materials 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
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- 230000000630 rising effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000002345 surface coating layer Substances 0.000 description 1
- 229910001428 transition metal ion Inorganic materials 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
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- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to the field of lithium ion batteries, and discloses a positive electrode material, a preparation method thereof and a lithium ion battery. The unit cell volume V of the positive electrode material obtained by XRD isThe positive electrode material has a composition: li aNibCocMndAeXfO2; the content e of element A and the unit cell volume V satisfy the following conditions: The positive electrode material has a specific unit cell volume, the unit cell volume and the content of the element A meet a specific relation, and the co-doped element successfully enters a transition metal layer of the positive electrode material, so that the rapid migration of lithium ions between the transition metal layer can be promoted, the mixed discharge of lithium and nickel is reduced, the discharge capacity of the positive electrode material under severe high-power requirements is improved, the side reaction on the surface of an electrode can be effectively reduced, and the high-power cycle retention rate of the material under high-temperature conditions is improved.
Description
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a positive electrode material, a preparation method thereof and a lithium ion battery.
Background
In recent years, with the rapid development of electronic products, the demand of high-performance energy storage devices for human society is increasing. The energy storage industry of large-scale natural energy power generation energy storage, house energy storage, communication energy storage, electric automobiles and the like is rapidly rising and coming to rapidly increase the window period. Lithium ion batteries have attracted wide attention in industry and academia as the most promising power source for new energy storage technologies. The layered transition metal oxide ternary material (hereinafter referred to as ternary positive electrode material) is used as an important class in the positive electrode material of the lithium ion battery, and has a relatively unique crystal structure. Based on a two-dimensional diffusion channel formed by alternately arranging transition metal cations, lithium ions and oxygen ions, lithium ions in the ternary positive electrode material can become carriers for charge transmission and realize reversible intercalation/deintercalation electrochemical behaviors. Although the materials have been widely used commercially at present by virtue of their high specific capacity, high safety and the like, ternary positive electrode materials have also faced a great challenge in terms of high power charge and discharge and long cycle life. Under the application scene of high current density, lithium ions can be subject to slower ion diffusion speed and narrow interlayer spacing and can not be quickly intercalated and deintercalated among transition metal ions, so that polarization is generated, mixed discharge of lithium ions and nickel ions is caused, side reaction of an interface of a positive electrode material and an electrolyte is aggravated, and finally capacity loss and quick capacity attenuation under the high-power condition are caused. It is therefore desirable to provide a solution to the above-mentioned problems.
Disclosure of Invention
Based on the defects of the existing ternary positive electrode material, such as short low-temperature discharge time and short high-temperature cycle life, in a high-power application scene, the positive electrode material, the preparation method thereof and the lithium ion battery are provided. The positive electrode material has a specific unit cell volume, the unit cell volume and the content of the doping element meet a specific relation, and the doped element successfully enters a transition metal layer of the positive electrode material, so that the rapid migration of lithium ions between the transition metal layers can be promoted, the mixed discharge of lithium and nickel is reduced, the discharge capacity of the positive electrode material under the severe high-power requirement is improved, the side reaction on the surface of an electrode can be effectively reduced, and the high-power cycle retention rate of the material under the high-temperature condition is improved.
The first aspect of the present invention provides a positive electrode material, wherein the unit cell volume V of the positive electrode material obtained by XRD is
The positive electrode material has a composition represented by formula I:
LiaNibCocMndAeXfO2,1.0≤a≤1.08,0.3≤b≤1.0,0≤c≤0.3,0.1≤d
≤0.3，0.001≤e≤0.05，0≤f≤0.1；
Wherein A is at least one element selected from Na, K, rb, cs, be, mg, ca, sr, ba; x is at least one element selected from Al, B, W, si;
the content e of the element A in the positive electrode material and the unit cell volume V of the positive electrode material obtained by XRD satisfy the following conditions: Wherein the unit of unit cell volume V is/>
The second aspect of the present invention provides a method for preparing a positive electrode material, which is characterized in that the method comprises:
S1, mixing lithium salt, a compound containing an element A and a precursor of a positive electrode material, and performing first sintering in an oxygen-containing atmosphere to obtain a first sintering material;
S2, mixing the first sintering material with water, washing under the stirring condition, performing solid-liquid separation to obtain a solid phase, and drying the solid phase to obtain a washing and drying material;
and S3, mixing the dry cleaning material with an optional coating agent, and performing second sintering in an oxygen-containing atmosphere to obtain the positive electrode material.
The third aspect of the present invention provides a positive electrode material produced by the above-described production method.
The fourth aspect of the invention provides a lithium ion battery, wherein the lithium ion battery comprises the positive electrode material.
Through the technical scheme, the positive electrode material, the preparation method thereof and the lithium ion battery provided by the invention have the following beneficial effects:
When the co-doped positive electrode material provided by the invention has a specific unit cell volume and the content of the doping element meet the above relation, the specific amount of the doping element successfully enters the transition metal layer of the positive electrode material, so that the rapid migration of lithium ions between the transition metal layers can be promoted, the mixed discharge of lithium and nickel is reduced, the discharge capacity of the positive electrode material under the severe high-power requirement is improved, the side reaction on the surface of an electrode can be effectively reduced, and the high-power cycle retention rate of the material under the high-temperature condition is improved.
Further, the positive electrode material provided by the invention has larger transition metal interlayer spacing and better layered structure, and can support lithium ions to quickly and reversibly migrate between transition metal layers, so that the positive electrode material can show excellent high-power high-temperature cycle performance and high-power low-temperature discharge performance.
According to the preparation method of the positive electrode material, the first sintering material obtained by mixing and sintering the positive electrode material precursor, the lithium salt and the compound containing the element A is washed, so that the element A is successfully incorporated between transition metal layers of the ternary positive electrode material, the co-doping element distribution in the lattice structure of the first sintering material is more uniform, and the doping effect of the co-doping element is effectively improved. In addition, the step can also effectively avoid the occurrence of electrolyte side reaction caused by residual alkali remaining on the surface of the positive electrode material.
Further, when the washing condition is controlled to enable the washing storage rate to meet a specific range, residual alkali on the surface of the material can be removed on the premise of keeping effective doping elements in the lattice structure, and the difficult problem of alkali enrichment which is difficult to solve in the common doping element doping process is solved.
Drawings
FIG. 1 is an SEM image of a sodium-doped ternary cathode material prior to water washing in example 1;
Fig. 2 is a cycle performance graph of a lithium ion battery assembled from the positive electrode materials of example 1, comparative example 2;
FIG. 3 is a graph of the cycle performance at-20℃of lithium ion batteries assembled from the positive electrode materials of example 1, comparative example 1;
fig. 4 is an SEM image of the positive electrode material of comparative example 3.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The first aspect of the present invention provides a positive electrode material, wherein the unit cell volume V of the positive electrode material obtained by XRD is
The positive electrode material has a composition represented by formula I:
LiaNibCocMndAeXfO2,1.0≤a≤1.08,0.3≤b≤1.0,0≤c≤0.3,0.1≤d
≤0.3，0.001≤e≤0.05，0≤f≤0.1；
Wherein A is at least one element selected from Na, K, rb, cs, be, mg, ca, sr, ba; x is at least one element selected from Al, B, W, si;
the content e of the element A in the positive electrode material and the unit cell volume V of the positive electrode material obtained by XRD satisfy the following conditions: Wherein the unit of unit cell volume V is/>
In the invention, when the specific unit cell volume of the positive electrode material is provided and the content of the unit cell volume and the content of the doping element meet the above relation, the specific amount of the doping element successfully enters the transition metal layer of the positive electrode material to reflect the lattice distortion of the positive electrode material, so that the rapid migration of lithium ions between the transition metal layers can be promoted, the mixed discharge of lithium and nickel can be reduced, the discharge capacity of the positive electrode material under severe high power requirement can be improved, the side reaction on the surface of an electrode can be effectively reduced, and the high power cycle retention rate of the material under high temperature condition can be improved.
In the present invention, the unit cell volume can be obtained by methods known in the art such as XRD refinement.
Further, the unit cell volume V of the positive electrode material obtained by XRD is
According to the invention, the element A of a specific type has a large ionic radius and has similar electronegativity with lithium ions, and the element A of the specific type can enter the transition metal layer of the positive electrode material, so that an ion diffusion channel of the positive electrode material is widened and plays a role in pinning to assist the transition metal element to maintain the stability of the material structure, thereby promoting the rapid migration of lithium ions between the transition metal layers, reducing the mixed discharge of lithium and nickel, improving the discharge capability of the positive electrode material under the severe high-power requirement, effectively reducing the side reaction of the electrode surface, and improving the high-power cycle retention rate of the material under the high-temperature condition.
In the present invention, the main elements distributed inside the positive electrode material particles are Ni, co, mn and a, and the main metal element distributed on the surface of the positive electrode material particles is X, except for Li element.
In the invention, the metal element X in the positive electrode material is mainly a coating element, and the surface coating layer comprises at least one element from a matrix Ni, co, mn, A in a lithium oxide compound of the X element and/or an oxide containing the X element.
Further, a is more than or equal to 1.02 and less than or equal to 1.06,0.5 and less than or equal to b is more than or equal to 0.98,0.01 and less than or equal to c is more than or equal to 0.3,0.05 and less than or equal to d is more than or equal to 0.25,0.001 and less than or equal to e is more than or equal to 0.03,0.01 and less than or equal to 0.05.
Further, a is selected from at least one of Na, mg, K, ca, rb.
According to the invention, the positive electrode material has a (003) diffraction peak 2 theta (003) of 18.6-18.8 degrees by XRD.
According to the present invention, the half-peak width β (003) of the (003) diffraction peak obtained by XRD of the positive electrode material is 0.150 to 0.180 °.
In the invention, when the (003) diffraction peak 2 theta (003) or half-peak width beta (003) obtained by XRD of the co-doped positive electrode material meets the range, the co-doped positive electrode material has larger transition metal layer spacing and better layered structure, and can support lithium ions to quickly and reversibly migrate between transition metal layers, so that the co-doped positive electrode material can show excellent high-power high-temperature cycle performance and high-power low-temperature discharge performance.
Further, the positive electrode material has a (003) diffraction peak 2 theta (003) of 18.660 to 18.700 ° obtained by XRD.
Further, the half-peak width β (003) of the (003) diffraction peak obtained by XRD of the positive electrode material is 0.160 to 0.174 °.
According to the invention, the grain size value D of the positive electrode material obtained by XRD is
In the invention, the grain size value D is obtained by XRD refinement and calculation by combining with a Schle formula.
In the invention, when the grain size value D of the positive electrode material meets the range, the doping element can provide better lattice supporting effect and avoid overlarge lattice volume expansion, so that the intercalation and deintercalation dynamic behaviors of lithium ions between transition metal layers are enhanced, and the lattice structure strength is improved.
Further, the grain size value D of the positive electrode material obtained by XRD is
In the present invention, the inventors have found that (003) diffraction peak 2θ (003) of the positive electrode material is related to the content of element a, and 2θ (003) is shifted to a small angle as the content of element a increases, and in one embodiment of the present invention, the following is satisfied between the content e of element in the positive electrode material and (003) diffraction peak 2θ (003) obtained by XRD of the positive electrode material: 18.681 DEG is less than or equal to 2 theta (003) DEG +0.553e is less than or equal to 18.681 deg.
In the present invention, the inventors have found that the half-peak width β (003) of the cathode material is related to the content of the element a, and that the half-peak width β (003) decreases as the content of the element a increases. In one specific embodiment of the present invention, the content e of the element a in the positive electrode material and the half-peak width β (003) of the positive electrode material obtained by XRD satisfy: beta (003)°-90.096e2 +1.6845e is more than or equal to 0.1609 DEG and less than or equal to 0.1749 deg.
In the invention, when the (003) diffraction peak 2 theta (003) of the positive electrode material or the half-peak width beta (003) of the positive electrode material meets the range, the positive electrode material has larger transition metal layer spacing and better layered structure, and can support lithium ions to quickly and reversibly migrate between transition metal layers, so that the positive electrode material can show excellent high-power high-temperature cycle performance and high-power low-temperature discharge performance.
In the present invention, the difficulty in diffusing lithium ions across the unit cell in the positive electrode material until the particle surface is reached can be jointly reacted by the unit cell volume V and the grain size value D. Preferably, as the cell volume V increases, 2θ (003) is shifted to a small angle, and β (003) is reduced, the particle size value D is a smaller value, where lithium ions diffuse across a smaller number of cells, more facilitating charge transport at high current densities and thus improving the discharge performance of the cathode material at high power.
The second aspect of the present invention provides a method for preparing a positive electrode material, which is characterized in that the method comprises:
S1, mixing lithium salt, a compound containing an element A and a precursor of a positive electrode material, and performing first sintering in an oxygen-containing atmosphere to obtain a first sintering material;
S2, mixing the first sintering material with water, washing under the stirring condition, performing solid-liquid separation to obtain a solid phase, and drying the solid phase to obtain a washing and drying material;
and S3, mixing the dry cleaning material with an optional coating agent, and performing second sintering in an oxygen-containing atmosphere to obtain the positive electrode material.
According to the preparation method provided by the invention, the surface and the inside of the prepared positive electrode material are distributed with co-doping elements. The doped element A in the positive electrode material can widen a lithium ion diffusion channel due to the larger size of the doped element A and plays a role of pinning to assist the transition metal element to maintain the stability of the material structure. However, the excessive doping elements on the surface of the material form alkaline compounds, which cause side reactions when contacting with electrolyte, thereby affecting the safety performance and capacity of the lithium ion battery.
Based on the above situation, in the invention, the first sintering material obtained by mixing and sintering the positive electrode material precursor, the lithium salt and the compound containing the element A is washed, so that the element A is successfully incorporated between transition metal layers of the ternary positive electrode material, and the co-doping element distribution in the lattice structure of the first sintering material is more uniform, thereby effectively improving the doping effect of the element. In addition, the step can also effectively avoid the occurrence of electrolyte side reaction caused by residual alkali remaining on the surface of the positive electrode material.
In the present invention, in order to further judge whether the degree of washing and the addition amount of the co-doping element are appropriate, the inventors found through studies that the degree of washing and the addition amount of the element can be judged by controlling the washing rate Δa=the content of a in the positive electrode material/the content of the first sintered material a×100%. In particular, when the wash-out rate satisfies: when delta a is more than or equal to 35% and less than or equal to 80%, the washing effect is better, the alkaline substance residue on the surface of the positive electrode material is less, and enough alkali metal ions enter the interlayer of the positive electrode material to play a better circulation rate improvement effect. If the higher the wash-out rate, this indicates that the alkali metal element is more present in the lattice than the material surface. However, when the washing rate is too high, the addition amount of alkali metal is not saturated, and at this time, the alkali metal ions playing a supporting role in the structure of the positive electrode material are less, and the performance improvement effect is not remarkable.
In the present invention, the content of a in the element and the content of a in the first frit are measured by ICP.
Further, 51% or more and 75% or less of Δa.
In the present invention, the conditions for washing are not particularly limited as long as the washing rate can be made to satisfy the limitations of the present invention.
In one embodiment of the present invention, in step S2, the stirring speed is 100-500rpm, and the washing time is 0.5-2min.
In a specific embodiment of the invention, the solid-liquid separation mode is suction filtration, and preferably, the suction filtration time is 2-5min.
According to the invention, the mass ratio of the first sintering material to water is 0.25-3:1.
In the invention, when the mass ratio of the first sintering material to the water is controlled to meet the range, the slurry has better fluidity.
Further, the mass ratio of the first sintering material to the water is 1-2.5:1.
In the invention, the water is preferably water with the temperature of 8-15 ℃, so that residual alkali on the surface of the particles can be washed away without excessive removal of lithium ions, structural elements and doping elements.
According to the invention, said step S1 comprises:
s1-1, mixing lithium salt with a compound containing an element A to obtain a mixture;
s1-2, mixing the mixture with a positive electrode material precursor, and performing first sintering in an oxygen-containing atmosphere to obtain a first sintered material.
According to the invention, the problem of residual alkali enrichment of the compound containing the element A during co-intercalation sintering with lithium salt can be remarkably improved by premixing the lithium salt and the compound containing the element A, and the element distribution in the lattice structure of the first sintered material obtained through the step is more uniform, so that the doping effect of the element is effectively improved. In addition, the step can also effectively avoid the occurrence of electrolyte side reaction caused by residual alkali remaining on the surface of the positive electrode material.
According to the invention, the peak intensity ratio I R＝I1st/I2nd of the strongest peak to the next strongest peak of the particle size volume distribution curve obtained by the particle size distribution instrument of the mixture is more than or equal to 1.4.
According to the invention, the peak area ratio S R＝S1st/S2nd of the strongest peak to the next strongest peak of the particle size volume distribution curve obtained by the particle size distribution instrument of the mixture is more than or equal to 82.
In the invention, when the peak intensity ratio and the peak area ratio of the strongest peak to the next strongest peak of the mixture are controlled to meet the requirements, the mixing effect of the mixed salt reaches the requirements, and the mixed salt can uniformly react with precursor particles during sintering, thereby avoiding the phenomenon of enriching alkali metal/residual lithium on the surface of the positive electrode.
Further, the peak intensity ratio I R＝I1st/I2nd of the strongest peak to the next strongest peak of the particle size volume distribution curve obtained by the particle size distribution instrument of the mixture is more than or equal to 2.0.
Further, the peak area ratio S R＝S1st/S2nd of the strongest peak to the next strongest peak of the particle size volume distribution curve obtained by the particle size distribution instrument of the mixture is more than or equal to 90.
In the invention, the variety of the compound containing the element A can influence the particle size detection result, and the uniformity of the granularity and the distribution of the mixed salt can be improved by adding the grinding process when the mixed salt cannot meet the requirement.
In the present invention, the mixing apparatus used for the premixing process is not particularly limited, and may be one of apparatuses of conventional kinds in the art, such as a mixing tank, a high mixer and a coulter mixer.
According to the invention, the lithium salt, the compound containing the element A, the positive electrode material precursor and the coating agent are used in such amounts that n (Li) n (Ni) n (Co) n (Mn) n (A) n (X) a b c e f, wherein a is 1.0-1.08,0.3-b 1.0, c is 0-0.3,0.1-d is 0.3, e is 0.001-e is 0.05 and f is 0-0.1.
In the present invention, the amounts of the lithium salt, the compound containing the element a, the positive electrode material precursor, and the coating agent to be charged are not particularly limited, as long as the contents of the respective elements in the positive electrode material to be produced satisfy the above-described requirements. Specifically, in the present invention, the first sintering material is washed with water, which causes a certain loss of Li, a, and other elements, so that the amount of the lithium salt, the compound containing element a, the precursor of the positive electrode material, and the coating agent is generally higher than the actual content in the co-doped positive electrode material.
Further, a is more than or equal to 1.02 and less than or equal to 1.06,0.5 and less than or equal to b is more than or equal to 0.98,0.01 and less than or equal to c is more than or equal to 0.3,0.05 and less than or equal to d is more than or equal to 0.25,0.001 and less than or equal to e is more than or equal to 0.03,0.01 and less than or equal to 0.05.
In the present invention, the type of lithium salt is not particularly limited, and may be one or a mixture of sulfate, nitrate, chloride, acetate, citrate, carbonate, oxide, and hydroxide.
In the present invention, the type of the compound containing the element a is not particularly limited as long as the doping element a can be provided, and for example, an oxide containing a, a salt containing a, or the like may be used.
In the present invention, the positive electrode material precursor is a ternary positive electrode material precursor, for example, ni bCocMnd(OH)2.
In the present invention, the type of the coating agent is not particularly limited as long as the coating element X can be provided, for example, one of sulfate, chloride, acetate, citrate, carbonate, oxide, hydroxide, or a mixture thereof.
According to the invention, the first sintering comprises: heating from room temperature to 300-600deg.C at a rate of 1-10deg.C/min, heating to 700-900deg.C for 6-10 hr, and maintaining at 700-900deg.C for 4-15 hr.
In the invention, the first sintering process is adopted to improve the growth effect of the anode material crystal, shorten the whole sintering period and improve the production efficiency.
According to the invention, the sintering time of the second sintering is 7-16h, and the sintering temperature of the second sintering is 250-600 ℃.
Further, the sintering time of the second sintering is 8-14h, and the sintering temperature of the second sintering is 260-450 ℃.
In one embodiment of the present invention, the second sintering includes: heating to 250-600deg.C for 1-4 hr, and maintaining at 250-600deg.C for 6-12 hr.
The third aspect of the invention provides a co-doped positive electrode material prepared by the preparation method.
A fourth aspect of the present invention provides a lithium ion battery, which is characterized in that the lithium ion battery comprises the above co-doped cathode material.
The present invention will be described in detail by examples. In the following examples, the unit cell volume, (003) diffraction peak 2θ (003), (003) diffraction peak half-width β (003) and crystal grain size value D of the positive electrode material were measured by XRD.
The content of the elements in the positive electrode material and the first frit was measured by ICP.
The average particle diameter of the positive electrode material and the particle size volume distribution curve of the mixture were obtained by a laser particle sizer.
Example 1
(1) Sodium carbonate and lithium hydroxide are mixed according to the mass ratio of 0.0024:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 6/2/2 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered in the step (2) to 350 ℃ at a heating rate of 5 ℃/min under the oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the first sintered material.
(4) Mixing the first sintering material obtained in the step (3) with water according to the following ratio of 1:1 is added into pure water with the temperature of 12 ℃ according to the proportion, stirred for 45s according to the rotation speed of fixed 400rpm for washing, and then is subjected to suction filtration and drying for 3min to obtain sodium co-doped washing dry material.
(5) And (3) heating the washing and drying material in the step (4) to 360 ℃ for 2 hours under the air condition, preserving heat for 8 hours, and naturally cooling to obtain the sodium co-doped anode material.
The chemical formula of the positive electrode material is Li 1.05Ni0.59924Co0.19975Mn0.19975Na0.00126O2.
Specifically, measurement observation and measurement were performed on the positive electrode material in the above example 1:
(1) ICP test is carried out on the first sintering material and the sodium co-doped positive electrode material in the embodiment 1 of the invention, and the sodium element washing and storing rate delta a is calculated to be 0.60, wherein the ratio indicates that the adding amount of sodium element is moderate and the sodium element well enters the crystal lattice of the positive electrode material.
(2) The material before the step (4) in the embodiment 1 of the present invention is observed under an electron scanning microscope to obtain a scanning electron microscope image as shown in fig. 1, and as can be seen from fig. 1, the material in the embodiment 1 of the present invention, in which the premixing step is implemented, is very smooth, and no enrichment of lithium/sodium elements is seen.
(3) XRD testing of the cathode material of example 1 of the invention was conducted to determine the unit cell volume(003) Diffraction peak diffraction angle 2θ (003) = 18.680 °, diffraction peak half-width β (003) =0.1660°, and fine-tuning the average grain size/>
(4) The positive electrode material in the embodiment 1 of the invention is used for manufacturing a 2032 button cell, and the cell is subjected to a cyclic charge and discharge test under the conditions of 3.0-4.3, 45 ℃ and 2C charge and discharge, so that a cyclic performance diagram shown in fig. 2 is obtained; the battery was charged to 4.3V at 25 ℃ with a current of 0.1C, discharged to 30% SOC, and then shifted to-20 ℃ to discharge to 3.0V with a current of 1C for low-temperature power discharge performance test, thereby obtaining a low-temperature performance graph shown in fig. 3. As shown in fig. 2 and 3, the button cell made of the positive electrode material in example 1 of the present invention had an initial capacity of 182.1mAh/g after cyclic discharge, a capacity retention rate of 94.4% after 80 weeks of cycle, and a low-temperature discharge period of 412s. The sodium co-doped positive electrode material in the embodiment 1 of the invention has obviously improved high-temperature high-power cycle performance and low-temperature high-power discharge performance.
Comparative example 1
(1) The method comprises the steps of mixing two raw materials of lithium hydroxide and a ternary precursor with the nickel/cobalt/manganese element ratio of 6/2/2 according to the mass ratio of 1.05:2.1, mixing in a high-speed mixer to obtain the material to be sintered.
(2) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under the oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the ternary anode material.
The chemical formula of the positive electrode material is Li 1.05Ni0.6Co0.2Mn0.2O2.
Specifically, measurement observation and measurement were performed on the above positive electrode materials:
(1) XRD measurement was performed on the positive electrode material of comparative example 1 according to the present invention, and the unit cell volume thereof (003) Diffraction peak diffraction angle 2θ (003) = 18.733 °, diffraction peak half-width β (003) =0.175°, and fine-tuning average grain size/>
(2) The positive electrode material of comparative example 1 of the present invention was used to prepare a 2032-type coin cell, and the above-described cell was charged to 4.3V at 25 ℃ with a current of 0.1C, discharged to 30% SOC, and then shifted to-20 ℃ to discharge to 3.0V with a current of 1C for low-temperature power discharge performance test, thereby obtaining a low-temperature performance graph shown in fig. 3. The button cell made of the positive electrode material in comparative example 1 of the present invention had an initial capacity of 182.3mAh/g for cyclic discharge, a capacity retention rate of 90.9% after 80 weeks of cycle, and a low-temperature discharge period of 340s as shown in FIG. 3.
Comparative example 2
(1) Sodium carbonate and lithium hydroxide are mixed according to the mass ratio of 0.0015:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 6/2/2 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under an oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the sodium co-doped ternary cathode material.
The chemical formula of the positive electrode material is Li 1.05Ni0.59924Co0.19975Mn0.19975Na0.00126O2.
Specifically, the positive electrode material in the above comparative example 2 was observed and measured:
(1) XRD measurement was performed on the positive electrode material of comparative example 2 according to the present invention, which had a unit cell volume (003) Diffraction peak diffraction angle 2θ (003) = 18.639 °, diffraction peak half-width β (003) =0.158°, and fine-tuning average grain size/>
(2) As shown in FIG. 2, the button cell made of the positive electrode material in the comparative example of the invention has an initial capacity of 178.1mAh/g after cyclic discharge in comparative example 2, a capacity retention rate of 90.6% after 80 weeks of cycle, and a low-temperature discharge duration of 383s.
Comparative example 3
(1) Sodium carbonate and lithium hydroxide are mixed according to the mass ratio of 0.0024:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 6/2/2 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under an oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the sodium co-doped ternary anode material before water washing.
The chemical formula of the positive electrode material is Li 1.05Ni0.59874Co0.19958Mn0.19958Na0.00211O2.
Specifically, the positive electrode material in the above comparative example 3 was measured:
(1) XRD measurement was performed on the positive electrode material in comparative example 3 of the present invention, which had a unit cell volume (003) Diffraction peak diffraction angle 2θ (003) = 18.649 °, diffraction peak half-width β (003) =0.157°, and fine-tuning the average grain size/>
(2) The positive electrode material in comparative example 3 of the present invention was observed under an electron scanning microscope to obtain a scanning electron microscope image as shown in fig. 4, and as can be seen from fig. 4, the surface of the positive electrode material in comparative example 3 of the present invention has more dark color concentrate, which is rich in alkaline lithium or sodium element.
(3) The button cell made of the positive electrode material in comparative example 3 has an initial capacity of 177.8mAh/g after cyclic discharge, a capacity retention rate of 87.8% after 80 weeks of cycle, and a low-temperature discharge time of 350s.
Example 2
(1) Sodium carbonate and lithium hydroxide are mixed according to the mass ratio of 0.01:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 6/2/2 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under the oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the first sintered material.
(4) And (3) mixing the first sintering material obtained in the step (3) with water according to the mass ratio of 1:1 is added into pure water with the temperature of 11 ℃ according to the proportion, stirred for 45s according to the rotation speed of fixed 400rpm for washing, and then is subjected to suction filtration and drying for 3min to obtain sodium co-doped washing dry material.
(5) And (3) heating the washing and drying material in the step (4) to 360 ℃ for 2 hours under the air condition, preserving heat for 8 hours, and naturally cooling to obtain the sodium co-doped anode material.
The chemical formula of the positive electrode material is Li 1.05Ni0.59715Co0.19905Mn0.19905Na0.00474O2.
Specifically, measurement observation and measurement were performed on the positive electrode material in the above example 2:
(1) ICP test is carried out on the first sintering material and the sodium co-doped positive electrode material in the embodiment 2 of the invention, and the sodium element washing and storing rate delta a is calculated to be 0.55.
(2) Its unit cell volume(003) Diffraction peak diffraction angle 2θ (003) =18.678°, (003) diffraction peak half-width β (003) =0.162°, and average crystal grain size/>
(3) The positive electrode material in example 2 of the present invention was used to prepare a 2032-type button cell, the initial capacity of cyclic discharge was 177.7mAh/g, the capacity retention after 80 weeks of cycle was 93.2%, and the low-temperature discharge period was 377s.
Example 3
(1) Sodium carbonate and lithium hydroxide are mixed according to the mass ratio of 0.0035:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 6/2/2 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under the oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the first sintered material.
(4) Mixing the first sintering material obtained in the step (3) with water according to a mass ratio of 1:1 is added into pure water with the temperature of 15 ℃ according to the proportion, and is stirred for 150 seconds according to the rotation speed of fixed 400rpm for washing, and then is subjected to suction filtration and drying for 3 minutes, so as to obtain the sodium co-doped washing dry material.
(5) And (3) heating the washing and drying material in the step (4) to 360 ℃ for 2 hours under the air condition, preserving heat for 8 hours, and naturally cooling to obtain the sodium co-doped anode material.
The chemical formula of the positive electrode material is Li 1.05Ni0.59924Co0.19975Mn0.19975Na0.00126O2.
Specifically, measurement observation and measurement were performed on the positive electrode material in the above example 3:
(1) ICP test is carried out on the first sintering material and the sodium co-doped anode material in the embodiment 3 of the invention, and the sodium element washing and storing rate delta a is calculated to be 0.42.
(2) XRD testing of the cathode material of example 3 of the invention was conducted, with its unit cell volume
(003) Diffraction peak diffraction angle 2θ (003) = 18.680 °, diffraction peak half-width β (003) =0.165°, and fine-tuning the average grain size/>
(3) The button cell made of the positive electrode material in the embodiment of the invention has the initial capacity of 178.3mAh/g after cyclic discharge, the capacity retention rate of 92.1% after 80 weeks of cycle and the low-temperature discharge duration of 378s.
Example 4
(1) Sodium carbonate and lithium hydroxide are mixed according to the mass ratio of 0.0019:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 6/2/2 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under the oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the first sintered material.
(4) Mixing the first sintering material obtained in the step (3) with water according to a mass ratio of 1:1 is added into pure water with the temperature of 6 ℃ according to the proportion, and is stirred for 15s according to the fixed rotating speed of 300rpm to wash, and then the sodium co-doped washing dry material is obtained after 3min of suction filtration and drying.
(5) And (3) heating the washing and drying material in the step (4) to 360 ℃ for 2 hours under the air condition, preserving heat for 8 hours, and naturally cooling to obtain the sodium co-doped anode material.
The chemical formula of the positive electrode material is Li 1.05Ni0.59924Co0.19975Mn0.19975Na0.00126O2.
Specifically, measurement observation and measurement were performed on the positive electrode material in the above example 4:
(1) ICP test is carried out on the first sintering material and the sodium co-doped positive electrode material in the embodiment 4 of the invention, and the sodium element washing and storing rate delta a is calculated to be 0.77.
(2) XRD testing of the cathode material of example 4 of the invention was conducted to determine the unit cell volume
(003) Diffraction peak diffraction angle 2θ (003) = 18.680 °, diffraction peak half-width β (003) =0.168°, and fine-tuning average grain size/>
(3) The button cell made of the positive electrode material in the embodiment of the invention has the initial capacity of 180.3mAh/g after cyclic discharge, the capacity retention rate after 80 weeks of cycle is 92.2%, and the low-temperature discharge duration is 392s.
Example 5
(1) Sodium carbonate and lithium hydroxide are mixed according to the mass ratio of 0.0030:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 76.5/1.5/22 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under the oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the first sintered material.
(4) And (3) mixing the first sintering material obtained in the step (3) with water according to a mass ratio of 2.5:1 is added into pure water with the temperature of 11 ℃ according to the proportion, and is stirred for 100s according to the fixed rotation speed of 200rpm for washing, and then is subjected to suction filtration and drying for 5min, thus obtaining the sodium co-doped washing dry material.
(5) The dry washing material and boric acid in the step (4) are mixed according to the following ratio of 1: mixing according to the proportion of 0.0069, heating to 360 ℃ for 2 hours under the air condition, preserving heat for 8 hours, and naturally cooling to obtain the sodium co-doped anode material.
The chemical formula of the positive electrode material is Li 1.05Ni0.76371Co0.01497Mn0.21963Na0.0169B0.0107O2.
Specifically, measurement observation and measurement were performed on the positive electrode material in the above example 5:
(1) ICP test is carried out on the first sintering material and the sodium co-doped positive electrode material in the embodiment 5 of the invention, and the sodium element washing and storing rate delta a is calculated to be 0.63.
(2) XRD testing of the cathode material of example 5 of the invention was conducted to determine the unit cell volume
(003) Diffraction peak diffraction angle 2θ (003) = 18.666 °, diffraction peak half-width β (003) =0.172°, and fine-tuning average grain size/>
(3) The button cell made of the positive electrode material in the embodiment of the invention has initial capacity of 203.2mAh/g in cyclic discharge, capacity retention rate of 95.3% after 80 weeks in cycle and low-temperature discharge time of 324s.
Example 6
(1) Magnesium carbonate and lithium hydroxide are mixed according to the mass ratio of 0.0018:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 6/2/2 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under the oxygen condition, heating to 840 ℃ for 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the first sintered material.
(4) Mixing the first sintering material obtained in the step (3) with water according to a mass ratio of 1:1 is added into pure water with the temperature of 12 ℃ according to the proportion, stirred for 45s according to the rotation speed of fixed 400rpm for washing, and then is subjected to suction filtration and drying for 3min to obtain the potassium co-doped washing dry material.
(5) And (3) heating the dry washing material in the step (4) to 360 ℃ for 2 hours under the air condition, preserving heat for 8 hours, and naturally cooling to obtain the magnesium co-doped anode material.
The chemical formula of the positive electrode material is Li 1.05Ni0.59915Co0.19972Mn0.19972Mg0.00142O2.
Specifically, measurement observation and measurement were performed on the positive electrode material in the above example 6:
(1) ICP test is carried out on the first sintering material and the magnesium co-doped anode material in the embodiment 6 of the invention, and the magnesium element washing and storing rate delta a is calculated to be 0.71.
(2) XRD testing of the cathode material of example 6 of the invention was conducted to determine the unit cell volume
(003) Diffraction peak diffraction angle 2θ (003) =18.675°, diffraction peak half-width (003) β (003) =0.169°, and fine-tuning the average grain size/>
(3) The button cell made of the positive electrode material in the embodiment 6 of the invention has the initial capacity of 181.3mAh/g after cyclic discharge, the capacity retention rate of 93.8% after 80 weeks of cycle and the low-temperature discharge time of 408s.
Example 7
(1) Potassium hydroxide and lithium hydroxide are mixed according to the mass ratio of 0.0045:1 in a high-speed mixer to obtain mixed salt.
(2) The ternary precursor with the ratio of the mixed salt obtained in the step (1) to nickel/cobalt/manganese element of 6/2/2 is prepared according to the following formula 1: mixing in a high-speed mixer in a proportion of 2.12 to obtain the material to be sintered.
(3) And (3) heating the material to be sintered to 350 ℃ at a heating rate of 5 ℃/min under the oxygen condition, heating to 845 ℃ after 10 hours, preserving heat for 7 hours, and naturally cooling to obtain the first sintered material.
(4) Mixing the first sintering material obtained in the step (3) with water according to a mass ratio of 1:1 is added into pure water with the temperature of 11 ℃ according to the proportion, stirred for 45s according to the rotation speed of fixed 400rpm for washing, and then is subjected to suction filtration and drying for 3min to obtain the potassium co-doped washing dry material.
(5) And (3) heating the dry washing material in the step (4) to 360 ℃ for 2 hours under the air condition, preserving heat for 8 hours, and naturally cooling to obtain the potassium co-doped positive electrode material, wherein the chemical formula of the positive electrode material is Li 1.05Ni0.59870Co0.19957Mn0.19957K0.00217O2.
Specifically, measurement observation and measurement were performed on the positive electrode material in the above example 7:
(1) ICP test is carried out on the first sintering material and the potassium co-doped anode material in the embodiment 7 of the invention, and the potassium element washing and storing rate delta a is calculated to be 0.73.
(2) XRD testing of the cathode material of example 7 of the invention was conducted, with its unit cell volume(003) Diffraction peak diffraction angle 2θ (003) = 18.670 °, diffraction peak half-width β (003) =0.171°, and fine-tuning average grain size/>
(3) The button cell made of the positive electrode material in the embodiment 7 of the invention has the initial capacity of 180.9mAh/g after cyclic discharge, the capacity retention rate after 80 weeks of cycle is 93.6%, and the low-temperature discharge time is 402s.
TABLE 1
Note that: formulas I-V+740.07e 2 -18.466e; formula II-2θ (003) +0.553e; formula III-beta (003)-90.096e2 +1.6845e
Test case
The positive electrode materials of the examples and comparative examples were prepared into 2032-type coin cells, and specifically, the coin cell components were assembled in the following order: the method comprises the steps of positive electrode shell, electrolyte, pole piece, diaphragm, electrolyte, liquid absorbing paper, lithium piece, foam nickel, electrolyte and negative electrode shell, wherein 18 drops of electrolyte are manually injected by using a plastic dropper (3 mL) in the process. Wherein, the positive electrode material in the pole piece: conductive agent: the mass ratio of the binder is 95:2.5:2.5.
The prepared battery is subjected to cyclic charge and discharge test under the conditions of 3.0-4.3, 45 ℃ and 2C charge and discharge; the prepared battery was charged to 4.3V at 25 ℃ with a current of 0.1C, discharged to 30% SOC, and then shifted to-20 ℃ to discharge to 3.0V with a current of 1C for low-temperature power discharge performance test, and the test results are shown in table 2.
TABLE 2
| Initial capacity | Capacity retention after 80 weeks of cycling | Duration of low-temperature discharge | |
| mAh/g | ％ | s | |
| Example 1 | 182.1 | 94.4 | 412 |
| Comparative example 1 | 182.3 | 90.9 | 340 |
| Comparative example 2 | 178.1 | 90.6 | 383 |
| Comparative example 3 | 177.8 | 87.8 | 350 |
| Example 2 | 177.7 | 93.2 | 377 |
| Example 3 | 178.3 | 92.1 | 378 |
| Example 4 | 180.3 | 92.2 | 392 |
| Example 5 | 203.2 | 95.3 | 324 |
| Example 6 | 181.3 | 93.8 | 408 |
| Example 7 | 180.9 | 93.6 | 402 |
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (10)
1. A positive electrode material characterized in that the positive electrode material has a unit cell volume V obtained by XRD of
The positive electrode material has a composition represented by formula I:
LiaNibCocMndAeXfO2,1.0≤a≤1.08,0.3≤b≤1.0,0≤c≤0.3,0.1≤d
≤0.3，0.001≤e≤0.05，0≤f≤0.1；
Wherein A is at least one element selected from Na, K, rb, cs, be, mg, ca, sr, ba; x is at least one element selected from Al, B, W, si;
the content e of the element A in the positive electrode material and the unit cell volume V of the positive electrode material obtained by XRD satisfy the following conditions: Wherein the unit of unit cell volume V is/>
2. The positive electrode material according to claim 1, wherein a unit cell volume V of the positive electrode material obtained by XRD is
Preferably, the positive electrode material has a (003) diffraction peak 2 theta (003) of 18.6 to 18.8 degrees by XRD;
preferably, the half-peak width β (003) of the (003) diffraction peak obtained by XRD of the positive electrode material is 0.150 to 0.180 °;
preferably, the positive electrode material has a grain size value D obtained by XRD of
3. The co-doped cathode material according to claim 1 or 2, wherein the content e of element a in the cathode material and the (003) diffraction peak 2Θ (003) obtained by XRD of the cathode material satisfy: 18.651 DEG or less 2 theta (003) DEG+ 0.553 DEG e or less 18.711 DEG;
preferably, the content e of the element a in the positive electrode material and the half-peak width β (003) of the positive electrode material obtained by XRD satisfy: beta (003)°-90.096°e2 and 1.6845 degrees e which are more than or equal to 0.1609 degrees and less than or equal to 0.1749 degrees.
4. A method for preparing a positive electrode material, comprising:
S1, mixing lithium salt, a compound containing an element A and a precursor of a positive electrode material, and performing first sintering in an oxygen-containing atmosphere to obtain a first sintering material;
S2, mixing the first sintering material with water, washing under the stirring condition, performing solid-liquid separation to obtain a solid phase, and drying the solid phase to obtain a washing and drying material;
and S3, mixing the dry cleaning material with an optional coating agent, and performing second sintering in an oxygen-containing atmosphere to obtain the positive electrode material.
5. The production method according to claim 4, wherein the washing is such that a washing yield Δa=a content in the positive electrode material/a content in the first sintered material x 100% satisfies: delta a is more than or equal to 35% and less than or equal to 80%, preferably, delta a is more than or equal to 45% and less than or equal to 75%, and more preferably, delta a is more than or equal to 51% and less than or equal to 75%;
preferably, in the step S2, the stirring speed is 100-500rpm, and the washing time is 0.5-2min;
preferably, the solid-liquid separation mode is suction filtration, and more preferably, the suction filtration time is 2-5min;
Preferably, the mass ratio of the first sintering material to water is 0.25-3:1.
6. The preparation method according to claim 4 or 5, wherein the step S1 comprises:
s1-1, mixing lithium salt with a compound containing an element A to obtain a mixture;
S1-2, mixing the mixture with a positive electrode material precursor, and performing first sintering in an oxygen-containing atmosphere to obtain a first sintered material;
Preferably, the peak intensity ratio I R＝I1st/I2nd of the strongest peak to the next strongest peak of the particle size volume distribution curve obtained by the particle size distribution instrument of the mixture is more than or equal to 1.4;
Preferably, the peak area ratio S R＝S1st/S2nd of the strongest peak to the next strongest peak of the particle size volume distribution curve obtained by the particle size distribution instrument of the mixture is more than or equal to 82.
7. The production method according to any one of claims 4 to 6, wherein the lithium salt, the element A-containing compound, the positive electrode material precursor, and the coating agent are used in such amounts that n (Li) n (Ni) n (Co) n (Mn) n (A) n (X) a b c e f, wherein 1.0.ltoreq.a.ltoreq. 1.08,0.3.ltoreq.b.ltoreq.1.0, 0.ltoreq.c.ltoreq. 0.3,0.1.ltoreq.d.ltoreq.0.3, 0.001.ltoreq.e.ltoreq.0.05, and 0.ltoreq.f.ltoreq.0.1 in the Co-doped positive electrode material.
8. The production method according to any one of claims 4 to 7, wherein the first sintering includes: heating from room temperature to 300-600deg.C at a rate of 1-10deg.C/min, heating to 700-900deg.C for 6-10h, and maintaining at 700-900deg.C for 4-15h;
preferably, the sintering time of the second sintering is 7-16h, and the sintering temperature of the second sintering is 250-600 ℃;
Preferably, the second sintering includes: heating to 250-600deg.C for 1-4 hr, and maintaining at 250-600deg.C for 6-12 hr.
9. A co-doped cathode material produced by the production method according to any one of claims 4 to 8.
10. A lithium ion battery, characterized in that it comprises a co-doped positive electrode material according to any one of claims 1-3 and 9.
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