LYZP-coated doped ternary positive electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to an LYZP-coated doped ternary positive electrode material as well as a preparation method and application thereof. The invention provides an LYZP-coated doped ternary positive electrode material, which comprises a doped ternary positive electrode material and a coating layer, and the coating layer comprises LYZP; in the doped ternary positive electrode material, doped elements comprise at least one of a titanium element, an aluminum element, a yttrium element, a tungsten element, a niobium element and an indium element. The LYZP coated and doped ternary positive electrode material provided by the invention has excellent cycle performance and thermal stability on the basis of increasing the nickel content.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a LYZP-coated doped ternary positive electrode material and a preparation method and application thereof. Background Art

[0002] A key factor in the development of new energy vehicles is range, and increasing the energy density of lithium-ion batteries is an effective way to improve range. High-nickel ternary layered materials offer high specific capacity and low cost; however, increasing nickel content significantly reduces the battery's cycling performance and thermal stability. Existing technologies use doping or coating to improve the cycling performance and thermal stability of ternary high-nickel materials, but the performance gains are limited and cannot meet practical needs. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the ternary high-nickel materials modified by doping or coating in the prior art, such as poor cycle performance and thermal stability, thereby providing a LYZP-coated doped ternary positive electrode material and its preparation method and application.

[0004] To this end, the present invention provides the following technical solutions.

[0005] The present invention provides a LYZP-coated doped ternary positive electrode material, comprising a doped ternary positive electrode material and a coating layer, wherein the coating layer comprises LYZP; in the doped ternary positive electrode material, the doping element comprises at least one of titanium, aluminum, yttrium, tungsten, niobium and indium.

[0006] The chemical formula of LYZP is Li a Y b Zr c (PO4) d ; Among them, 1.2≤a≤1.4, 0.2≤b≤0.4, 1.6≤c≤1.8, 2.9≤d≤3.1;

[0007] In an optional embodiment, the molar ratio of nickel, cobalt and manganese in the doped ternary positive electrode material is (0.7-1):(0-0.1):(0-0.2); wherein the values ​​of cobalt and manganese are not 0;

[0008] In an optional embodiment, the ratio of the total molar amount of nickel, cobalt and manganese elements to the molar amount of lithium element in the doped ternary positive electrode material is 1:(1.02-1.06);

[0009] In an optional embodiment, based on the mass of the doped ternary positive electrode material, the doping amount of the doping element is 0.04-0.79 wt%;

[0010] In an optional embodiment, the mass content of LYZP in the doped ternary positive electrode material is 0.05-0.4%.

[0011] The present invention also provides a method for preparing a LYZP-coated doped ternary cathode material, comprising the following steps:

[0012] (1) preparing a doped ternary cathode material; the doping element comprises at least one of titanium, aluminum, yttrium, tungsten, niobium and indium;

[0013] (2) The doped ternary cathode material and the coating solution containing the LYZP precursor are mixed and calcined to obtain the LYZP-coated doped ternary cathode material.

[0014] If LYZP or LYZP precursor raw materials are directly dry-mixed and calcined with ternary cathode materials, the coating uniformity is poor, and a large amount of LZP and / or LYP will be mixed in the obtained coating layer, which greatly reduces the cycle performance and thermal stability of the material.

[0015] In an optional embodiment, in step (2), the coating liquid containing the LYZP precursor is added by spraying at 8-12 ml / min, and stirring is continued for 0.5-1 h after the addition is completed;

[0016] The solvent of the coating solution includes an organic solvent;

[0017] The organic solvent includes ethanol;

[0018] The molar ratio of lithium, yttrium, zirconium and phosphorus in the coating solution containing the LYZP precursor is (1.2-1.4):(0.2-0.4):(1.6-1.8):(2.9-3.1);

[0019] In an optional embodiment, the LYZP-containing precursor coating solution includes a lithium-containing compound, a yttrium-containing compound, a zirconium-containing compound and a phosphate; the lithium-containing compound does not contain any metal elements other than lithium; the yttrium-containing compound does not contain any metal elements other than yttrium; the zirconium-containing compound does not contain any metal elements other than zirconium;

[0020] In an optional embodiment, the lithium-containing compound includes lithium nitrate;

[0021] In an optional embodiment, the yttrium-containing compound comprises yttrium nitrate;

[0022] In an alternative embodiment, the zirconium-containing compound comprises zirconium nitrate;

[0023] In an alternative embodiment, the phosphate comprises ammonium dihydrogen phosphate.

[0024] In an optional embodiment, the calcination is carried out under an oxygen atmosphere;

[0025] In an optional embodiment, the heating rate of the calcination is 1.5-5°C / min;

[0026] In an optional embodiment, the calcination temperature is 600-800°C;

[0027] In an optional embodiment, the calcination time is 3-7 hours.

[0028] In an optional embodiment, the preparation step of the doped ternary cathode material includes: mixing a ternary precursor, a lithium source and an additive, and sintering to obtain a doped ternary cathode material; the additive contains at least one of titanium, aluminum, yttrium, tungsten, niobium and indium;

[0029] Preferably, the ratio of the total molar amount of nickel, cobalt and manganese in the ternary precursor to the molar amount of lithium in the lithium source is 1:(1.02-1.06);

[0030] Preferably, the ternary precursor comprises nickel-cobalt-manganese hydroxide, the chemical composition of which comprises Ni x Co y Mn 1-x-y (OH)2, 0.7≤x<1, 0<y≤0.1;

[0031] Preferably, the lithium source comprises lithium hydroxide;

[0032] Preferably, based on the mass of the ternary precursor, the amount of the additive added is 0.05-0.8 wt%.

[0033] In an optional embodiment, the sintering is carried out in an oxygen atmosphere;

[0034] In an optional embodiment, the sintering heating rate is 1-5°C / min;

[0035] In an optional embodiment, the sintering includes a first sintering and a second sintering.

[0036] In an optional embodiment, the temperature of the first sintering is 400-600°C;

[0037] In an optional embodiment, the first sintering time is 2-5h;

[0038] In an optional embodiment, the temperature of the second sintering is 650-900°C;

[0039] In an optional embodiment, the second sintering time is 8-12 hours.

[0040] The present invention also provides an application of the above-mentioned LYZP coated and doped ternary positive electrode material or the LYZP coated and doped ternary positive electrode material prepared by the above-mentioned preparation method in a lithium ion battery.

[0041] The technical solution of the present invention has the following advantages:

[0042] 1. The LYZP-coated doped ternary cathode material provided herein comprises a doped ternary cathode material and a coating layer, the coating layer comprising LYZP. The doped ternary cathode material comprises at least one of titanium, aluminum, yttrium, tungsten, niobium, and indium. The LYZP-coated doped ternary cathode material provided herein exhibits excellent cycling performance and thermal stability while increasing nickel content. On the one hand, the doping element increases the likelihood of achieving a reversible H2-H3 phase transition, reduces structural damage, and simultaneously reduces the activity of surface lattice oxygen, inhibiting oxygen evolution. On the other hand, the surface-coated LYZP, acting as a fast ion conductor coating, exhibits high lithium ion conductivity, significantly improving lithium ion diffusion kinetics. LYZP also inhibits interfacial side reactions on the cathode material surface. The phosphate groups in the LYZP form strong covalent bonds with metal ions such as lithium, zirconium, and yttrium. These two combined effects impart excellent structural stability to both the interior and surface of the cathode material, enhancing the battery's cycling performance and thermal stability.

[0043] 2. The preparation method of the LYZP-coated doped ternary positive electrode material provided by the present invention adopts a LYZP coating liquid for wet coating, which has good coating uniformity and further improves the cycle performance and thermal stability of the obtained battery. DETAILED DESCRIPTION

[0044] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0045] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0046] Example 1

[0047] This embodiment provides a method for preparing a LYZP-coated doped ternary cathode material, comprising the following steps:

[0048] (1) Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor, lithium hydroxide, titanium dioxide, yttrium trioxide, tungsten trioxide and indium trioxide were mixed evenly, heated to 450℃ at 2℃ / min for the first sintering for 3h, the heating rate was 2℃ / min, and then heated to 790℃ at 2℃ / min for the second sintering for 10h, and naturally cooled to room temperature to obtain a doped ternary positive electrode material; wherein, Ni 0.8 Co 0.1 Mn 0.1 The ratio of the total molar amount of nickel ions, cobalt ions and manganese ions in the (OH)2 precursor to the molar amount of lithium ions in lithium hydroxide is 1:1.04; the mass ratio of titanium dioxide, yttrium trioxide, tungsten trioxide and indium trioxide is 1:0.001:0.002:0.001:0.001; in the LYZP coated doped ternary positive electrode material, the mass content of titanium, yttrium, tungsten and indium elements in the doped ternary positive electrode material is 0.46%.

[0049] (2) LiNO3, Y(NO3)3·6H2O, Zr(NO3)4·5H2O, and NH4H2PO4 were dissolved in ethanol to obtain a mixed solution, wherein the molar ratio of lithium in LiNO3, yttrium in Y(NO3)3·6H2O, zirconium in Zr(NO3)4·5H2O, and phosphorus in NH4H2PO4 was 1.3:0.3:1.7:3; the doped ternary cathode material was placed in a stirring tank, and the mixed solution was sprayed into the stirring tank at 8 ml / min. After the spraying of the mixed solution was completed, stirring was continued for 0.5 h; the temperature was increased to 700°C at 2°C / min in an oxygen atmosphere, calcined for 4 h, and naturally cooled to room temperature to obtain a LYZP-coated doped ternary cathode material. The mass content of LYZP in the doped ternary cathode material was 0.2%.

[0050] Example 2

[0051] This embodiment provides a method for preparing a LYZP-coated doped ternary cathode material, comprising the following steps:

[0052] (1) Ni 0.7 Co 0.1 Mn 0.2 (OH)2 precursor, lithium hydroxide, titanium dioxide, yttrium trioxide, tungsten trioxide and niobium tetroxide were mixed evenly, heated to 500℃ at 5℃ / min for the first sintering for 5h, then heated to 850℃ at 5℃ / min for the second sintering for 12h, and naturally cooled to room temperature to obtain a doped ternary positive electrode material; wherein Ni 0.7 Co 0.1 Mn 0.2The ratio of the total molar amount of nickel ions, cobalt ions and manganese ions in the (OH)2 precursor to the molar amount of lithium ions in lithium hydroxide is 1:1.05; the mass ratio of titanium dioxide, yttrium trioxide, tungsten trioxide and niobium tetroxide is 1:0.001:0.002:0.001:0.002; in the LYZP coated doped ternary positive electrode material, the mass content of titanium, yttrium, tungsten and indium elements in the doped ternary positive electrode material is 0.56%.

[0053] (2) LiNO3, Y(NO3)3·6H2O, Zr(NO3)4·5H2O, and NH4H2PO4 were dissolved in ethanol to obtain a mixed solution, wherein the molar ratio of lithium element in LiNO3, yttrium element in Y(NO3)3·6H2O, zirconium element in Zr(NO3)4·5H2O, and phosphorus element in NH4H2PO4 was 1.2:0.4:1.8:2.9; the doped ternary cathode material was placed in a stirring tank, and the mixed solution was sprayed into the stirring tank at a rate of 12 ml / min. After the spraying of the mixed solution was completed, stirring was continued for 1 hour; the temperature was increased to 600°C at 5°C / min in an oxygen atmosphere, and calcined for 4 hours, and then naturally cooled to room temperature to obtain a LYZP-coated doped ternary cathode material. The mass content of LYZP in the doped ternary cathode material was 0.3%.

[0054] Example 3

[0055] This embodiment provides a method for preparing a LYZP-coated doped ternary cathode material, comprising the following steps:

[0056] (1) Ni 0.7 Co 0.1 Mn 0.2 The (OH)2 precursor, lithium hydroxide, titanium dioxide, tungsten trioxide and niobium tetroxide were mixed evenly, heated to 600℃ at 3℃ / min for the first sintering for 4h, then heated to 600℃ at 3℃ / min for the second sintering for 8h, and naturally cooled to room temperature to obtain a doped ternary cathode material; wherein Ni 0.7 Co 0.1 Mn 0.2 The ratio of the total molar amount of nickel ions, cobalt ions and manganese ions in the (OH)2 precursor to the molar amount of lithium ions in lithium hydroxide is 1:1.02; the mass ratio of titanium dioxide, yttrium trioxide, tungsten trioxide and niobium tetroxide is 1:0.001:0.001:0.001; in the LYZP coated doped ternary positive electrode material, the mass content of titanium, yttrium, tungsten and indium elements in the doped ternary positive electrode material is 0.27%.

[0057] (2) LiNO3, Y(NO3)3·6H2O, Zr(NO3)4·5H2O, and NH4H2PO4 were dissolved in ethanol to obtain a mixed solution, wherein the molar ratio of lithium in LiNO3, yttrium in Y(NO3)3·6H2O, zirconium in Zr(NO3)4·5H2O, and phosphorus in NH4H2PO4 was 1.4:0.2:1.6:3.1; the doped ternary cathode material was placed in a stirring tank, and the mixed solution was sprayed into the stirring tank at a rate of 10 ml / min. After the spraying of the mixed solution was completed, stirring was continued for 1 hour; the temperature was increased to 800°C at 3°C / min in an oxygen atmosphere, and calcined for 7 hours, and then naturally cooled to room temperature to obtain a LYZP-coated doped ternary cathode material. The mass content of LYZP in the doped ternary cathode material was 0.08%.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing a high-nickel doped ternary positive electrode material. Compared with Example 1, the only difference is that step (2) is not performed.

[0060] Comparative Example 2

[0061] This comparative example provides a preparation method of a coated doped ternary positive electrode material. Compared with comparative example 1, the only difference is that it further includes step (2). Step (2) is as follows:

[0062] Li2TiO3 was dissolved in ethanol to obtain a mixed liquid, the doped ternary cathode material was placed in a stirring tank, and the mixed liquid was sprayed into the stirring tank at a certain rate. After the spraying of the mixed liquid was completed, stirring was continued for 0.5h; the mass ratio of the doped ternary cathode material and Li2TiO3 was 1:0.002; the temperature was raised to 700℃ at 2℃ / min in an oxygen atmosphere and calcined for 4h, and then naturally cooled to room temperature to obtain a coated doped ternary cathode material.

[0063] Comparative Example 3

[0064] This comparative example provides a preparation method of a coated doped ternary positive electrode material. Compared with Example 1, the only difference is that titanium dioxide, yttrium trioxide, tungsten trioxide and indium trioxide are not added.

[0065] Comparative Example 4

[0066] This comparative example provides a method for preparing a ternary positive electrode material. Compared with Example 1, the only difference is that titanium dioxide, yttrium trioxide, tungsten trioxide and indium trioxide are not added in step (1).

[0067] Step (2) is not performed.

[0068] Comparative Example 5

[0069] This comparative example provides a method for preparing a coated ternary positive electrode material, comprising the following steps:

[0070] (1) Prepare a ternary positive electrode material according to Example 1;

[0071] (2) The ternary cathode material was uniformly mixed with lithium nitrate, yttrium nitrate, zirconium nitrate, and ammonium dihydrogen phosphate, and the mixture was heated to 600°C at a rate of 2°C / min in an oxygen atmosphere for 4 hours, and then naturally cooled to room temperature to obtain a coated ternary cathode material. The molar ratio of lithium in lithium nitrate, yttrium in yttrium nitrate, zirconium in zirconium nitrate, and phosphorus in ammonium dihydrogen phosphate was 1.3:0.3:1.7:3; the ratio of the sum of the mass of lithium nitrate, yttrium nitrate, zirconium nitrate, and ammonium dihydrogen phosphate to the mass of the ternary cathode material was 0.002:1.

[0072] Test Case

[0073] The performance tests of the ternary materials prepared in Examples 1-3 and Comparative Examples 1-5 were carried out as follows:

[0074] The ternary material, polyvinylidene fluoride (PVDF), and Super P (SP) were weighed and homogenized according to the mass ratio of 97.2:1.3:1.5, and then the aluminum foil was spread flat on the coating machine for coating (surface density of 15 mg / cm 2 ), placed in an 80°C forced air drying oven and dried for 2 hours; then punching, weighing, and baking the electrode to obtain a positive electrode; using a lithium sheet as the negative electrode, a CR2032 button battery was made according to the assembly order of negative electrode shell, lithium sheet, electrolyte (1 mol / L LiPF6, solvent is a mixture of ethylene carbonate (EC) / dimethyl carbonate (DMC) with a volume ratio of 1:1), PP separator, electrolyte, positive electrode sheet, gasket, spring, and positive electrode shell.

[0075] The performance test of the battery prepared above is as follows:

[0076] (1) Cycling performance test: At room temperature, the battery was placed in a blue battery test system, charged to 4.25V at a charge rate of 1C, and then discharged to 3V at a discharge rate of 1C. The number of cycles was 100. The results are shown in Table 1. The cycling performance is the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle.

[0077] (2) Thermal stability test method: At 45°C, place the battery in a blue battery test system, charge it to 4.25V at a charge rate of 1C, and then discharge it to 3V at a discharge rate of 1C. The number of cycles is 100. The results are shown in Table 1. Thermal stability refers to the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle at 45°C.

[0078] Table 1

[0079] Cycle performance% Thermal stability% Example 1 94.8 93.1 Example 2 95.1 93.9 Example 3 95.0 93.7 Comparative Example 1 90.2 87.5 Comparative Example 2 91.9 90.3 Comparative Example 3 92.1 90.2 Comparative Example 4 87.4 83.1 Comparative Example 5 91.9 90.5

[0080] As can be seen from Table 1, the LYZP-coated doped ternary positive electrode material provided by the present invention not only increases the nickel content, but the LYZP and doping elements work together to make the interior and surface of the positive electrode material have good structural stability, so that the prepared battery has excellent cycle performance and thermal stability.

[0081] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A LYZP coated doped ternary cathode material, characterized in that: It comprises a doped ternary positive electrode material and a coating layer, wherein the coating layer comprises LYZP; in the doped ternary positive electrode material, the doping element comprises at least one of titanium, aluminum, yttrium, tungsten, niobium and indium.

2. The LYZP coated doped ternary cathode material according to claim 1, characterized in that: The molar ratio of nickel, cobalt and manganese in the doped ternary positive electrode material is (0.7-1):(0-0.1):(0-0.2); wherein the values ​​of cobalt and manganese are not 0; and / or, The ratio of the total molar amount of nickel, cobalt and manganese elements to the molar amount of lithium element in the doped ternary positive electrode material is 1:(1.02-1.06); and / or, Based on the mass of the doped ternary cathode material, the doping amount of the doping element is 0.04-0.79 wt%; and / or, The mass content of LYZP in the doped ternary positive electrode material is 0.05-0.4%.

3. A method for preparing a LYZP-coated doped ternary cathode material, characterized in that: The steps include: (1) preparing a doped ternary cathode material; the doping element comprises at least one of titanium, aluminum, yttrium, tungsten, niobium and indium; (2) The doped ternary cathode material and the coating solution containing the LYZP precursor are mixed and calcined to obtain the LYZP-coated doped ternary cathode material.

4. The preparation method according to claim 3, characterized in that The LYZP-containing precursor coating solution comprises a lithium-containing compound, a yttrium-containing compound, a zirconium-containing compound and phosphate.

5. The preparation method according to claim 4, characterized in that The lithium-containing compound includes lithium nitrate; and / or, The yttrium-containing compound includes yttrium nitrate; and / or, The zirconium-containing compound comprises zirconium nitrate; and / or, The phosphate includes ammonium dihydrogen phosphate.

6. The preparation method according to any one of claims 3 to 5, characterized in that The calcination is carried out under an oxygen atmosphere; and / or, The heating rate of the calcination is 1.5-5°C / min; and / or, The calcination temperature is 600-800°C; and / or, The calcination time is 3-7h.

7. The preparation method according to any one of claims 3 to 6, characterized in that The preparation steps of the doped ternary cathode material include: mixing a ternary precursor, a lithium source and an additive, and sintering to obtain the doped ternary cathode material; the additive contains at least one of titanium, aluminum, yttrium, tungsten, niobium and indium; Preferably, the ratio of the total molar amount of nickel, cobalt and manganese in the ternary precursor to the molar amount of lithium in the lithium source is 1:(1.02-1.06); Preferably, the ternary precursor comprises nickel-cobalt-manganese hydroxide, the chemical composition of which comprises Ni x Co y Mn 1-x-y (OH)2, 0.7≤x<1, 0<y≤0.1; Preferably, the lithium source comprises lithium hydroxide.

8. The preparation method according to claim 7, characterized in that The sintering is carried out in an oxygen atmosphere; and / or, The sintering heating rate is 1-5°C / min; and / or, The sintering includes a first sintering and a second sintering.

9. The preparation method according to claim 8, characterized in that The temperature of the first sintering is 400-600° C.; and / or, The first sintering time is 2-5 hours; and / or, The temperature of the second sintering is 650-900° C.; and / or, The second sintering time is 8-12 hours.

10. Use of the LYZP coated and doped ternary cathode material according to any one of claims 1 to 2 or the LYZP coated and doped ternary cathode material prepared by the preparation method according to any one of claims 3 to 9 in a lithium-ion battery.