COMPOSITE POSITIVE ELECTRODE MATERIAL FOR LITHIUM ION BATTERY, PREPARATION METHOD THEREFOR, AND USE THEREOF

Abstract

A composite positive electrode material for a lithium ion battery, a preparation method therefor, and a use thereof. The composite positive electrode material comprises a positive electrode material core and a halide coating layer that is coated on the surface of the positive electrode material core, wherein halide comprises Li.sub.3YX.sub.6, and X is at least one among halogens. By means of the coating of the halide coating layer, the ionic conductivity and structural stability of the positive electrode material are greatly increased, which reduces the surface impedance of the material.

Claims

1. A composite cathode material for a lithium-ion battery, comprising a cathode material core and a halide cladding layer cladded on the surface of the cathode material core, wherein the halide comprises Li.sub.3YX.sub.6, wherein X is at least one of halogens.

2. The composite cathode material for a lithium-ion battery according to claim 1, wherein the halide is Li.sub.3YCl.sub.6 and/or Li.sub.3YBr.sub.6.

3. The composite cathode material for a lithium-ion battery according to claim 1, wherein the cathode material core comprises a cobalt-free cathode material.

4. The composite cathode material for a lithium-ion battery according to claim 1, wherein the cathode material core comprises a lithium nickel manganate cathode material.

5. The composite cathode material for a lithium-ion battery according to claim 4, wherein the lithium nickel manganate cathode material has a chemical formula of LiNi.sub.xMn.sub.yO.sub.2, wherein x is greater than or equal to 0.55 and less than or equal to 0.95, and y is greater than or equal to 0.05 and less than or equal to 0.45.

6. The composite cathode material for a lithium-ion battery according to claim 1, wherein the content of Y element in Li.sub.3YX.sub.6 is 0.1% to 1% based on 100% of the mass of the cathode material core.

7. The composite cathode material for a lithium-ion battery according to claim 1, wherein the content of Y element in the Li.sub.3YX.sub.6 is 0.1% to 0.3% based on 100% of the mass of the cathode material core.

8. The composite cathode material for a lithium-ion battery according to claim 1, wherein the cathode material core has a particle size D50 of 1 μm to 5 μm.

9. (canceled)

10. The composite cathode material for a lithium-ion battery according to claim 1, wherein the Li.sub.3YX.sub.6 has a particle size D.sub.50 of 5 nm to 500 nm.

11. (canceled)

12. A method for preparing the composite cathode material for a lithium-ion battery according to claim 1, comprising the following steps: mixing a cladding agent with a matrix cathode material, and then performing high-temperature treatment at 400° C. to 800° C. under an oxygen-containing atmosphere to obtain a composite cathode material; wherein the cladding agent comprises Li.sub.3YX.sub.6, and X is at least one of halogens.

13. The method according to claim 10, wherein oxygen is present at a volume concentration of 20% to 100% in the oxygen-containing atmosphere.

14-20. (canceled)

21. The method according to claim 12, wherein the matrix cathode material is lithium nickel manganate, and a method for preparing the lithium nickel manganate comprises: (a) mixing a lithium source and a precursor Ni.sub.xMn.sub.y(OH).sub.2 uniformly, wherein x is greater than or equal to 0.55 and less than or equal to 0.95, and y is greater than or equal to 0.05 and less than or equal to 0.45; and (b) performing a high-temperature reaction at 800° C. to 1000° C. to obtain the lithium nickel manganate.

22. The method according to claim 21, wherein the lithium source in step (a) is LiOH.

23. The method according to claim 21, wherein the mixing in step (a) is: mixing in high-speed mixing equipment at a rotational speed of 2000 rpm to 3000 rpm for 10 minutes to 20 minutes.

24. The method according to claim 21, wherein the high-temperature reaction in step (b) is performed for 8 hours to 12 hours.

25. The method according to claim 21, wherein the high-temperature reaction in step (b) is performed under an oxygen-containing atmosphere having a volume concentration of oxygen greater than 90%.

26. The method according to claim 25, wherein the gas flow rate of the oxygen-containing atmosphere is 2 L/min to 20 L/min.

27. (canceled)

28. The method according to claim 12, comprising the following steps: (1) preparing a matrix cathode material lithium nickel manganate: (a) mixing LiOH and a precursor Ni.sub.xMn.sub.y(OH).sub.2 in high-speed mixing equipment at a rotational speed of 2000 rpm to 3000 rpm for 10 minutes to 20 minutes, wherein x is greater than or equal to 0.55 and less than or equal to 0.95, and y is greater than or equal to 0.05 and less than or equal to 0.45; and (b) performing a high-temperature reaction at 800° C. to 1000° C. for 8 hours to 12 hours under an oxygen-containing atmosphere having a volume concentration of oxygen greater than 90% to obtain lithium nickel manganate, cooling and crushing for later use, wherein the gas flow rate of the oxygen-containing atmosphere is 2 L/min to 20 L/min; and (2) mixing a cladding agent and the matrix cathode material in mixing equipment at a rotational speed of 2000 rpm to 3000 rpm for 10 minutes to 20 minutes, wherein the cladding agent is Li.sub.3YCl.sub.6 and/or Li.sub.3YBr.sub.6, performing high-temperature treatment at 400° C. to 700° C. for 4 hours to 8 hours under an oxygen-containing atmosphere, wherein oxygen is present at a volume concentration of 20% to 100% in the oxygen-containing atmosphere, grinding and sieving by a sieve with a mesh size of 300 to 400 to obtain a composite cathode material, wherein the composite cathode material comprises lithium nickel manganate and a cladding layer cladded on the surface of the lithium nickel manganate, wherein the cladding layer is Li.sub.3YCl.sub.6 and/or Li.sub.3YBr.sub.6; wherein the content of Y element in the cladding layer is 0.1% to 1% based on 100% of the mass of a cathode material core.

29. A cathode, comprising the composite cathode material for a lithium-ion battery according to claim 1.

30. A lithium-ion battery, comprising the cathode according to claim 29.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0056] The drawings are used to provide a further understanding of the solutions of the present disclosure, constitute a part of the description, explain the solutions of the present disclosure in conjunction with the embodiments of the present application, and do not limit the solutions of the present disclosure.

[0057] FIGS. 1a and 1b show SEM diagrams of a material before cladding (cathode material prepared in a comparative example provided in the present disclosure) at different multiples;

[0058] FIGS. 2a and 1b show SEM diagrams of a material after cladding (cathode material prepared in an example provided in the present disclosure) at different multiples;

[0059] FIG. 3 shows initial charge-discharge curves of the materials before and after cladding, where two curves marked by arrows in the figure correspond to the composite cathode material after cladding, and two curves not marked by arrows correspond to the cathode material before cladding, where the material before cladding corresponds to a cathode material prepared in a comparative example, and the material after cladding corresponds to a composite cathode material prepared in an example; and

[0060] FIG. 4 shows cycling performance curves of materials before and after the cladding, where the material before cladding corresponds to a cathode material prepared in a comparative example, and the material after cladding corresponds to a composite cathode material prepared in an example.

DETAILED DESCRIPTION

[0061] Technical solutions of the present disclosure are further described below through specific embodiments in conjunction with the drawings.

Example 1

[0062] This example provided a composite cathode material for a lithium-ion battery. The composite cathode material included a cathode material core and a halide cladding layer cladded on the surface of the cathode material core. The cathode material core was LiNi.sub.0.75Mn.sub.0.25O.sub.2, and the halide was Li.sub.3YCl.sub.6. The content of Y element in Li.sub.3YCl.sub.6 was 0.5% based on 100% of the mass of the cathode material core, and the particle size D50 of the cathode material core was 3 μm.

[0063] This example further provided a method for preparing the composite cathode material. The method included the following steps.

[0064] (1) A matrix cathode material lithium nickel manganate was prepared through the following steps.

[0065] (a) LiOH and a precursor Ni.sub.0.75Mn.sub.0.25(OH).sub.2 were mixed in high-speed mixing equipment at a rotational speed of 2500 rpm for 15 minutes.

[0066] (b) A high-temperature reaction was performed at 900° C. for 10 hours under an oxygen atmosphere at the gas flow rate of oxygen of 10 L/min to obtain lithium nickel manganate LiNi.sub.0.75M.sub.0.25O.sub.2, and the lithium nickel manganate was cooled and crushed for later use.

[0067] (2) A cladding agent Li.sub.3YCl.sub.6 and the matrix cathode material were mixed in mixing equipment at a rotational speed of 2200 rpm for 20 minutes, high-temperature treatment was performed at 600° C. for 5 hours under an oxygen-containing atmosphere which was a mixed atmosphere of oxygen and nitrogen with volume concentrations of 60% and 40%, respectively, and the treated mixture was ground and sieved by a sieve with a mesh size of 300 to obtain a composite cathode material.

Example 2

[0068] This example provided a composite cathode material for a lithium-ion battery. The composite cathode material included a cathode material core and a halide cladding layer cladded on the surface of the cathode material core. The cathode material core was LiNi.sub.0.6Mn.sub.0.4O.sub.2, and the halide was Li.sub.3YBr.sub.6. The content of Y element in Li.sub.3YBr.sub.6 was 0.3% based on 100% of the mass of the cathode material core, and the particle size D50 of the cathode material core was 3 μm.

[0069] This example further provided a method for preparing the composite cathode material. The method included the following steps.

[0070] (1) A matrix cathode material lithium nickel manganate was prepared through the following steps.

[0071] (a) LiOH and a precursor Ni.sub.0.6Mn.sub.0.4(OH).sub.2 were mixed in high-speed mixing equipment at a rotational speed of 2000 rpm for 20 minutes.

[0072] (b) A high-temperature reaction was performed at 1000° C. for 8 hours under an oxygen atmosphere at the gas flow rate of oxygen of 5 L/min to obtain lithium nickel manganate LiNi.sub.0.6Mn.sub.0.4O.sub.2, and the lithium nickel manganate was cooled and crushed for later use.

[0073] (2) A cladding agent Li.sub.3YBr.sub.6 and the matrix cathode material were mixed in mixing equipment at a rotational speed of 2750 rpm for 10 minutes, high-temperature treatment was performed at 500° C. for 5.5 hours under an oxygen-containing atmosphere which was a mixed atmosphere of oxygen and nitrogen with volume concentrations of 40% and 60%, respectively, and the treated mixture was ground and sieved by a sieve with a mesh size of 300 to obtain a composite cathode material.

Example 3

[0074] This example provided a composite cathode material for a lithium-ion battery. The composite cathode material included a cathode material core and a halide cladding layer cladded on the surface of the cathode material core. The cathode material core was LiNi.sub.0.7Mn.sub.0.3O.sub.2, and the halide was Li.sub.3YCl.sub.6. The content of Y element in Li.sub.3YCl.sub.6 was 0.8% based on 100% of the mass of the cathode material core, and the particle size D50 of the cathode material core was 3 μm.

[0075] This example further provided a method for preparing the composite cathode material. The method included the following steps.

[0076] (1) A matrix cathode material lithium nickel manganate was prepared through the following steps.

[0077] (a) Li.sub.2CO.sub.3 and a precursor Ni.sub.0.7Mn.sub.0.3(OH).sub.2 were mixed in high-speed mixing equipment at a rotational speed of 2800 rpm for 16 minutes.

[0078] (b) A high-temperature reaction was performed at 800° C. for 12 hours under an oxygen atmosphere at the gas flow rate of oxygen of 15 L/min to obtain lithium nickel manganate LiNi.sub.0.7Mn.sub.0.3O.sub.2, and the lithium nickel manganate was cooled and crushed for later use.

[0079] (2) A cladding agent Li.sub.3YCl.sub.6 and the matrix cathode material were mixed in mixing equipment at a rotational speed of 2250 rpm for 15 minutes, high-temperature treatment was performed at 450° C. for 8 hours under an oxygen-containing atmosphere which was a mixed atmosphere of oxygen and nitrogen with volume concentrations of 85% and 15%, respectively, and the treated mixture was ground and sieved by a sieve with a mesh size of 400 to obtain a composite cathode material.

Example 4

[0080] This example provided a composite cathode material for a lithium-ion battery. The composite cathode material included a cathode material core and a halide cladding layer cladded on the surface of the cathode material core. The cathode material core was lithium iron phosphate, and the halide was Li.sub.3YCl.sub.6. The content of Y element in Li.sub.3YCl.sub.6 was 0.7% based on 100% of the mass of the cathode material core, and the particle size D50 of the cathode material core was 3.5 μm.

[0081] The matrix material lithium iron phosphate was prepared through the following steps.

[0082] (1) Phosphoric acid and ferrous sulfate were added into a three-neck flask and stirred for about 15 minutes at a rotational speed of 300 rpm, then excessive hydrogen peroxide was added, and the pH of the solution was adjusted with ammonia water until white precipitation appeared. (2) The white precipitate was filtered, washed, and dried under vacuum at 60° C. to obtain iron phosphate (FePO.sub.4.2H.sub.2O) powder. (3) The white powder, lithium hydroxide, and acetylene black were mixed in mixing equipment and reacted at 600° C. for 12 hours under a nitrogen atmosphere at the gas flow rate of nitrogen of 15 L/min to obtain lithium iron phosphate powder as the matrix material, and the lithium iron phosphate powder was cooled and crushed for later use.

[0083] The cladding process was as follows: a cladding agent (Li.sub.3YCl.sub.6) and the matrix material were mixed in mixing equipment, high-temperature treatment was performed at 450° C. for 8 hours under an oxygen-containing atmosphere which was a mixed atmosphere of oxygen and nitrogen with volume concentrations of 85% and 15%, respectively, and the treated mixture was ground and sieved by a sieve with a mesh size of 400 to obtain a composite cathode material.

Example 5

[0084] This example provided a composite cathode material for a lithium-ion battery. The composite cathode material included a cathode material core and a halide cladding layer cladded on the surface of the cathode material core. The cathode material core was LiNi.sub.0.8Mn.sub.0.2O.sub.2, and the halide was Li.sub.3YCl.sub.6. The content of Y element in Li.sub.3YCl.sub.6 was 0.15% based on 100% of the mass of the cathode material core, and the particle size D50 of the cathode material core was 5 μm.

[0085] This example further provided a method for preparing the composite cathode material. The method included the following steps.

[0086] (1) A matrix cathode material lithium nickel manganate was prepared through the following steps.

[0087] (a) LiOH and a precursor Ni.sub.0.8Mn.sub.0.2(OH).sub.2 were mixed in high-speed mixing equipment at a rotational speed of 2000 rpm for 20 minutes.

[0088] (b) A high-temperature reaction was performed at 950° C. for 9 hours under an oxygen atmosphere at the gas flow rate of oxygen of 12 L/min to obtain lithium nickel manganate LiNi.sub.0.8Mn.sub.0.2O.sub.2, and the lithium nickel manganate was cooled and crushed for later use.

[0089] (2) A cladding agent Li.sub.3YCl.sub.6 and the matrix cathode material were mixed in mixing equipment at a rotational speed of 2600 rpm for 15 minutes, high-temperature treatment was performed at 550° C. for 7 hours under an oxygen-containing atmosphere which was a mixed atmosphere of oxygen and argon with volume concentrations of 90% and 10%, respectively, and the treated mixture was ground and sieved by a sieve with a mesh size of 250 to obtain a composite cathode material.

Example 6

[0090] The preparation method and conditions are the same as those in Example 1 except that the content of Y element in Li.sub.3YCl.sub.6 was 1.5% based on 100% of the mass of the cathode material core.

Example 7

[0091] The preparation method and conditions are the same as those in Example 1 except that the content of Y element in Li.sub.3YCl.sub.6 was 0.05% based on 100% of the mass of the cathode material core.

Comparative Example 1

[0092] This comparative example was uncladded cathode material LiNi.sub.0.75Mn.sub.0.25O.sub.2.

Comparative Example 2

[0093] The preparation method and conditions were the same as those in Example 1 except that Li.sub.3YCl.sub.6 was replaced with an oxide solid electrolyte LLZO (Li.sub.7La.sub.3Zr.sub.2O.sub.12).

Comparative Example 3

[0094] The preparation method and conditions were the same as those in Example 1 except that Li.sub.3YCl.sub.6 was replaced with a sulfide solid electrolyte LGPS (Li.sub.10GeP.sub.2Si.sub.2).

Comparative Example 4

[0095] The preparation method and conditions were the same as those in Example 1 except that the temperature of the high-temperature treatment was adjusted to 300° C. in step (2).

Comparative Example 5

[0096] The preparation method and conditions were the same as those in Example 1 except that the temperature of the high-temperature treatment was adjusted to 820° C. in step (2).

[0097] Test:

[0098] The morphology of the materials before and after cladding was analyzed by scanning electron microscope (SEM). FIGS. 1a and 1b show SEM diagrams of a material before cladding (the cathode material prepared in Comparative Example 1) at different multiples, and FIGS. 2a and 1b show SEM diagrams of a material after cladding (the composite cathode material prepared in Example 1) at different multiples. As can be seen from the figures, flaked cladding materials were distributed on the particles of the sample after cladding.

[0099] The diffusion coefficient of lithium ions in the materials was calculated by galvanostatic intermittent titration technique (GITT). The data is shown in Table 1.

TABLE-US-00001 TABLE 1 No. Sample D (cm.sup.2/s) Comparative Example 1 Before cladding 1.32 * 10.sup.−8 Example 1 After cladding 1.65 * 10.sup.−7 Comparative Example 2 Replaced with an oxide 0.93 * 10.sup.−7 electrolyte Comparative Example 3 Replaced with a sulfide 1.33 * 10.sup.−7 electrolyte

[0100] As can be seen from Table 1, the diffusion rate of lithium ions was increased and the conductivity of the material was improved after cladded with Li.sub.3YCl.sub.6.

[0101] Batteries were prepared by using the materials of each example and comparative example, and tested for initial charge-discharge performance and cycling performance. The batteries were prepared through the following steps. Firstly, the obtained cathode material, conductive agent SP, polyvinylidene fluoride, and N-methylpyrrolidone were mixed to prepare a paste, where the mass ratio of the cathode material, conductive agent, and polyvinylidene fluoride was 92:4:4, and the N-methylpyrrolidone was added in an amount that allowed the solid content of the paste to be 50%. Secondarily, the paste was uniformly cladded onto an aluminum foil, and the aluminum foil was dried at 100° C. for 12 hours to prepare an electrode. Then, the electrode was subjected to blanking into a round electrode with a diameter of 14 μm and prepared into a button half-cell in a glove box. Finally, the button cell was put on hold and subjected to the charge-discharge test. The initial charge-discharge performance test and cycling test were performed under the same test steps. Test conditions were as follows: in a 25° C. incubator, the charge rate and the discharge rate of the initial efficiency test were 0.1 C and 0.1 C, respectively; the charge rate and the discharge rate of the cycling test were 0.5 C and 1 C, respectively. The test results are shown in Table 2.

TABLE-US-00002 TABLE 2 Initial Capacity retention rate No. efficiency (%) after cycling (%) Example 1 87.68 96.02 Example 2 86.23 96.11 Example 3 86.59 95.13 Example 4 (lithium iron 98.37 93.74 phosphate matrix after cladding) Example 5 87.02 96.45 Example 6 87.51 97.27 Example 7 86.83 96.13 Comparative Example 1 86.66 95.13 Comparative Example 2 86.84 93.52 Comparative Example 3 87.21 94.53 Comparative Example 4 85.73 94.86 Comparative Example 5 84.25 94.66 Comparative Example 6 96.32 92.93 (lithium iron phosphate matrix after cladding)

[0102] FIG. 3 shows initial charge-discharge curves of the materials before and after cladding. In the figures, two curves marked by arrows in the figure correspond to the composite cathode material after cladding, and two curves not marked by arrows correspond to the cathode material before cladding, where the material before cladding corresponds to the cathode material prepared in Comparative Example 1, and the material after cladding corresponds to the composite cathode material prepared in Example 1. As can be seen from the figure, the discharge capacity of the uncladded material at 0.1 C was 183.4 mAh/g, and the initial efficiency was 86.7%; the discharge capacity of the cladded material of the present disclosure at 0.1 C was 192.2 mAh/g, and the initial efficiency was 87.29%. Therefore, after cladded with Li.sub.3YCl.sub.6, the electrochemical performance of the material was improved.

[0103] FIG. 4 shows cycling performance curves of materials before and after the cladding, where the material before cladding corresponds to the cathode material prepared in Comparative Example 1, and the material after cladding corresponds to the composite cathode material prepared in Example 1. As can be seen from the curves, the material after cladding had good cycling stability, and the reason for the improvement in stability is that the halide cladding formed on the surface of the material had good stability and formed a stable and firm connection with the matrix material, which prevented the cathode material from being in contact with the electrolyte and reduced the occurrence of side reactions. The reason for the improvement in the initial efficiency is that the interaction between the halogen anions having a valence state of −1 in the halide and the lithium ions was weak, which caused good lithium-ion conductivity and reduced the surface impedance, and the large radius of halogen ions was beneficial to the migration of lithium ions.

[0104] With the comparison between Example 1 and Comparative Example 2, it indicates that when the cladding material was an oxide solid electrolyte, the ionic conductivity was poor, resulting in the decrease of the electrochemical performance of the material.

[0105] With the comparison between Example 1 and Comparative Example 3, it indicates that when the cladding material was a sulfide solid electrolyte, the stability during the cycling process was poor, resulting in the decrease of the cycling performance of the material.

[0106] With the comparison between Example 1 and Comparative Example 4, it indicates that when the cladding temperature was 300° C., the cladding material and the matrix material were not tightly bonded, resulting in the decrease of the cycling stability of the material.

[0107] With the comparison between Example 1 and Comparative Example 5, it indicates that when the cladding temperature was 820° C., the structure of the cladding material might change, affecting the cycling stability of the material.

[0108] With the comparison between Example 1 and Example 6, it indicates that when the thickness of the cladding layer was increased, it was difficult for lithium ions to deintercalate during the charge-discharge process.

[0109] With the comparison between Example 1 and Example 7, the amount of the halide cladding layer in Example 7 was small, resulting in poor improvement of the ionic conductivity.