Ternary positive electrode material and preparation method thereof

Abstract

The invention provides a ternary positive electrode material and a preparation method thereof, and relates to the field of lithium ion battery positive electrode materials. The preparation method of the ternary positive electrode material comprises the following steps: S1, uniformly mixing Li2S and TiS2, and carrying out ball milling treatment to obtain a precursor A; s2, adding NCM powder into the precursor A, and uniformly mixing to obtain a precursor B; s3, carrying out calcination treatment on the precursor B to obtain LTS-coated NCM; s4, ultrasonically dispersing LTS-coated NCM and pyrrole in water to obtain a suspension C; and S5, adding ferric chloride into the suspension C, stirring in a protective gas atmosphere, centrifuging and drying to obtain the ternary positive electrode material PPy / LTS-coated NCM. The ternary positive electrode material provided by the invention improves the rate and cycle performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery positive electrode materials, and in particular to a ternary positive electrode material and a preparation method thereof. Background Art

[0002] With the advancement of science and technology, energy consumption is increasing, and there is an urgent need to develop efficient energy conversion and storage systems and safe, pollution-free green energy to achieve the goal of sustainable development. In recent years, lithium-ion batteries have a very broad application prospect as a power source in portable electronic products, power vehicles and energy storage fields, and positive electrode materials, as one of the important components of lithium-ion batteries, play a vital role in their capacity and cycle performance.

[0003] Common positive electrode materials include LiCoO2, LiNiO2, LiMnO2 and LiNi x Co y Mn 1-y-z O2 (NCM), NCM has the advantages of low cost, large discharge capacity, and good cycle performance compared to other positive electrode materials. In order to ensure the high capacity of the battery, one method is to increase the Ni content in NCM. However, with the increase of Ni content, the number of phase changes during the charge and discharge process increases. When the Ni content is 33%, there is only one pair of redox peaks in the cyclic voltammetry test, and when the Ni content is greater than 80%, there will be 4 pairs of redox peaks in the cyclic voltammetry test. Among them, the H2-H3 phase change at 4.2V is the main reason for the capacity attenuation of high-nickel ternary materials. Therefore, it is urgent to develop a ternary positive electrode material, which is of great significance to the development of lithium-ion batteries. Summary of the invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a ternary positive electrode material and a preparation method thereof.

[0005] A method for preparing a ternary positive electrode material proposed by the present invention comprises the following steps:

[0006] S1, Li2S and TiS2 are mixed evenly and then ball-milled to obtain precursor A;

[0007] S2, adding NCM powder to precursor A and mixing evenly to obtain precursor B;

[0008] S3, calcining the precursor B to obtain LTS@NCM;

[0009] S4, ultrasonically dispersing LTS@NCM and pyrrole in water to obtain a suspension C;

[0010] S5. Add ferric chloride to the suspension C, stir under a protective gas atmosphere, and obtain the ternary positive electrode material PPy / LTS@NCM by centrifugation and drying.

[0011] Through the preparation method of the present invention, the precursor of Li2TiS3 (LTS) is obtained in sequence, and the LTS@NCM composite material is obtained after calcination, and then a layer of polypyrrole (PPy) is in situ polymerized on the surface of the LTS@NCM composite material to obtain the ternary positive electrode material PPy / LTS@NCM with excellent cycle performance. The modification method of the present invention is simple, the raw materials are abundant, the energy consumption is low, the production process is safe and reliable, the production cost is low, and it is easy to mass produce.

[0012] Preferably, in the S1, the molar ratio of Li2S to TiS2 is (0.8-1.2):(0.8-1.2).

[0013] By controlling the molar ratio of Li2S and TiS2 within a suitable range, it is helpful to obtain Li2TiS3 (LTS) coated on the NCM surface, accelerating the Li + The diffusion rate is increased and the side reactions on the NCM surface are inhibited, ensuring the interface stability during the charge and discharge process, thereby improving the battery's rate and cycle performance.

[0014] Preferably, in S1, the ball milling treatment includes using zirconium oxide balls for ball milling treatment, with a rotation speed of 300-400 r / min and a ball milling time of 25-35 h.

[0015] Controlling the conditions of ball milling treatment helps to achieve uniform ball milling within a certain range and improve the rate performance of the positive electrode material.

[0016] Preferably, in the S1, the mass ratio of the sum of the masses of Li2S and TiS2 to the mass of the zirconia ball is 1:50-100.

[0017] Preferably, in S2, the mixing frequency is 22.5-26.5 Hz, and the mixing time is 2-5 h.

[0018] Controlling the mixing frequency and time within a certain range is conducive to uniform mixing and energy saving; too slow mixing frequency will lead to too long mixing time, and too fast mixing frequency may cause the raw materials to not be fully mixed during the mixing process; too short time may lead to uneven mixing, and too long mixing time will not only cause the temperature in the mixing bin to be too high, but also cause energy waste.

[0019] Preferably, in the S2, NCM is LiNi x Co y Mn 1-x-y O2(0.6≤x≤1.0, 0≤y≤0.3).

[0020] Preferably, in S3, the calcination treatment comprises calcining the precursor B at 300-400° C. for 1-3 h, and then calcining at 600-700° C. for 2-4 h in an oxygen environment.

[0021] The calcination treatment is divided into two steps. The calcination helps the reaction to occur evenly, so that the generated LTS is evenly formed on the surface of the NCM. In addition, the two-step calcination can more effectively utilize energy and avoid energy waste.

[0022] Preferably, in S4 and S5, the mass ratio of LTS@NCM, pyrrole and ferric chloride is 1:(0.001-0.01):(0.001-0.02).

[0023] By controlling the mass ratio of LTS@NCM and pyrrole within an appropriate range, it is helpful to in-situ polymerize and coat a layer of polypyrrole (PPy) on the outer layer based on the inner layer coated with LTS. The in-situ polymerization coating can make the polymer form a continuous layered structure on the surface of the NCM material. PPy not only has excellent conductive properties, but its functional groups can also form a stable binding force with the transition element atoms, inhibiting the occurrence of H2-H3 phase transition during charging and discharging, thereby improving the interface stability, further inhibiting the side reactions on the surface, and improving the rate performance of the ternary positive electrode material.

[0024] The present invention also provides a ternary positive electrode material prepared by the above preparation method.

[0025] A ternary positive electrode material or the application of the ternary positive electrode material prepared by the above preparation method in a lithium ion battery.

[0026] The beneficial effects of the present invention are:

[0027] The present invention adopts a double-layer coating method to modify the NCM material. On the basis of coating the inner layer with LTS, a layer of polypyrrole (PPy) is in-situ polymerized and coated on the outer layer. LTS effectively inhibits the side reaction between the NCM surface and the electrolyte, ensuring the interface stability during the charge and discharge process. The PPy functional group can form a stable binding force with the transition element atoms, inhibiting the occurrence of H2-H3 phase transition during the charge and discharge process. The coordinated effect of the two improves the rate performance of the high-nickel ternary material. After the ternary positive electrode material is modified, the rate performance is improved, thereby improving the charge and discharge performance of the entire battery system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is a discharge capacity curve diagram of Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described in detail through specific embodiments.

[0030] Unless otherwise specified, the materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial sources.

[0031] Example 1

[0032] A method for preparing a ternary positive electrode material comprises the following steps:

[0033] S1. 6.7 mg Li2S and 16.4 mg TiS2 were mixed evenly to obtain a mixed powder, and the mixed powder was ball-milled with zirconium oxide balls at a mass ratio of 1:90, with a rotation speed of 350 r / min and a ball-milling time of 30 h to obtain a precursor A;

[0034] S2, 10g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder was added to precursor A and mixed using a 3D mixer at a mixing frequency of 25.8 Hz and a mixing time of 3.5 h to obtain a black precursor B;

[0035] S3: Precursor B was first calcined at 350°C for 2 h in an oxygen environment, and then calcined at 650°C for 3 h, with a heating rate of 2°C min -1 , get LTS@NCM;

[0036] S4, 10 g LTS@NCM and 0.04 g pyrrole were ultrasonically dispersed in water to obtain suspension C;

[0037] S5. Add 0.048 g of ferric chloride to the suspension C, stir for 12 h under N2 atmosphere, 25°C, and 400 r / min speed conditions, and obtain the ternary positive electrode material PPy / LTS@NCM by centrifugation and drying.

[0038] Example 2

[0039] A method for preparing a ternary positive electrode material comprises the following steps:

[0040] S1. 6.7 mg Li2S and 16.4 mg TiS2 were mixed evenly to obtain a mixed powder, and the mixed powder was ball-milled with zirconium oxide balls at a mass ratio of 1:90, with a rotation speed of 350 r / min and a ball-milling time of 30 h to obtain a precursor A;

[0041] S2, 10g of LiNi 0.8 Co 0.1 Mn 0.1O2 powder was added to precursor A and mixed using a 3D mixer at a mixing frequency of 25.8 Hz and a mixing time of 3.5 h to obtain a black precursor B;

[0042] S3: Precursor B was first calcined at 350°C for 2 h in an oxygen environment, and then calcined at 650°C for 3 h, with a heating rate of 2°C min -1 , get LTS@NCM;

[0043] S4, 10 g LTS@NCM and 0.02 g pyrrole were ultrasonically dispersed in water to obtain suspension C;

[0044] S5. Add 0.048 g of ferric chloride to the suspension C, stir for 12 h under N2 atmosphere, 25°C, and 400 r / min speed, and obtain the ternary positive electrode material PPy / LTS@NCM by centrifugation and drying.

[0045] Example 3

[0046] A method for preparing a ternary positive electrode material comprises the following steps:

[0047] S1. 6.7 mg Li2S and 16.4 mg TiS2 were mixed evenly to obtain a mixed powder, and the mixed powder was ball-milled with zirconium oxide balls at a mass ratio of 1:90, with a rotation speed of 350 r / min and a ball-milling time of 30 h to obtain a precursor A;

[0048] S2, 10g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder was added to precursor A and mixed using a 3D mixer at a mixing frequency of 25.8 Hz and a mixing time of 3.5 h to obtain a black precursor B;

[0049] S3: Precursor B was first calcined at 350°C for 2 h in an oxygen environment, and then calcined at 650°C for 3 h, with a heating rate of 2°C min -1 , get LTS@NCM;

[0050] S4, 10 g LTS@NCM and 0.06 g pyrrole were ultrasonically dispersed in water to obtain suspension C;

[0051] S5. Add 0.048 g of ferric chloride to the suspension C, stir for 12 h under N2 atmosphere, 25°C, and 400 r / min speed conditions, and obtain the ternary positive electrode material PPy / LTS@NCM by centrifugation and drying.

[0052] Comparative Example 1

[0053] Ternary cathode material is LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0054] Comparative Example 2

[0055] A method for preparing a ternary positive electrode material comprises the following steps:

[0056] S1. 6.7 mg Li2S and 16.4 mg TiS2 were mixed evenly to obtain a mixed powder, and the mixed powder was ball-milled with zirconium oxide balls at a mass ratio of 1:90, with a rotation speed of 350 r / min and a ball-milling time of 30 h to obtain a precursor A;

[0057] S2, 10g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder was added to precursor A and mixed using a 3D mixer at a mixing frequency of 25.8 Hz and a mixing time of 3.5 h to obtain a black precursor B;

[0058] S3: Precursor B was first calcined at 350°C for 2 h in an oxygen environment, and then calcined at 650°C for 3 h, with a heating rate of 2°C min -1 , and obtain the ternary positive electrode material LTS@NCM.

[0059] Comparative Example 3

[0060] A method for preparing a ternary positive electrode material comprises the following steps:

[0061] S1, 10g LiNi 0.8 Co 0.1 Mn 0.1 O2, 0.04 g pyrrole were ultrasonically dispersed in water to obtain a suspension;

[0062] S2. Add 0.048 g of ferric chloride to the suspension, stir for 12 h under N2 atmosphere, 25°C, and 400 r / min speed, and obtain the ternary positive electrode material PPy@NCM by centrifugation and drying.

[0063] The ternary positive electrode material prepared above is prepared into a positive electrode sheet, specifically including: dissolving the positive electrode material, SuperP and PVDF in NMP, stirring for 2 hours to form a positive electrode slurry, coating the positive electrode slurry on both surfaces of the aluminum foil, and then vacuum drying at 110°C for 20 hours, and then rolling, slicing, and weighing to obtain a positive electrode sheet including a positive electrode active layer, in which the mass ratio of the positive electrode material, SuperP and PVDF is 8:1:1.

[0064] In a glove box with argon atmosphere, the positive electrode sheet, the metal lithium sheet and the diaphragm prepared by the wet process were assembled into a CR2016 button battery. The electrolyte included EC, DEC and EMC in a volume ratio of 1:1:1, and the solute was 1.0 mol / L LiPF6.

[0065] The assembled button cell was subjected to the following performance tests, with a test voltage range of 2.8-4.35V. First, the battery was charged and discharged once at 0.2C, 0.33C, and 1C constant currents, then charged and discharged once at 0.2C constant current, and finally charged and discharged 50 times at 1C constant current. The test results are shown in Table 1 and Figure 1 .

[0066] Table 1 Electrochemical data of Examples 1-3 and Comparative Examples 1-3

[0067]

[0068] From Table 1, Figure 1 It can be seen from the data that the battery assembled from the ternary positive electrode material prepared by the present invention has a higher discharge capacity, first coulombic efficiency, and cycle retention rate, and has excellent gram capacity at high rate.

[0069] from Figure 1 It can be seen that the battery is charged and discharged once at 0.2C, 0.33C, and 1C constant currents in sequence, then charged and discharged once at 0.2C constant current, and finally charged and discharged 50 times at 1C constant current. According to the cycle curves of Example 1 and Comparative Example 1, it can be clearly seen that the rate performance of the material is significantly improved.

[0070] In summary, the ternary cathode material provided by the present invention improves the rate and cycle performance of the battery.

[0071] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a ternary positive electrode material, characterized in that: The following steps are involved: S1, Li2S and TiS2 are mixed evenly and then ball-milled to obtain precursor A; S2, adding NCM powder to precursor A and mixing evenly to obtain precursor B; S3, calcining the precursor B to obtain LTS@NCM; S4, ultrasonically dispersing LTS@NCM and pyrrole in water to obtain a suspension C; S5. Add ferric chloride to the suspension C, stir under a protective gas atmosphere, and obtain the ternary positive electrode material PPy / LTS@NCM by centrifugation and drying.

2. The preparation method according to claim 1, characterized in that: In the S1, the molar ratio of Li2S and TiS2 is (0.8-1.2):(0.8-1.2).

3. The preparation method according to claim 1, characterized in that: In the S1, the ball milling treatment includes using zirconium oxide balls for ball milling treatment, with a rotation speed of 300-400 r / min and a ball milling time of 25-35 h.

4. The preparation method according to claim 1, characterized in that: In the S2, the mixing frequency is 22.5-26.5 Hz, and the mixing time is 2-5 h.

5. The preparation method according to claim 1, characterized in that: In the above-mentioned S3, the calcination treatment includes calcining the precursor B at 300-400° C. for 1-3 hours in an oxygen environment, and then calcining at 600-700° C. for 2-4 hours.

6. The preparation method according to claim 1, characterized in that: In the S4 and S5, the mass ratio of LTS@NCM, pyrrole and ferric chloride is 1:(0.001-0.01):(0.001-0.02).

7. A ternary positive electrode material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the ternary positive electrode material according to claim 7 or the ternary positive electrode material prepared by the preparation method according to any one of claims 1 to 6 in a lithium ion battery.

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