Modified lithium ion battery ternary positive electrode material and preparation method and application thereof

Abstract

The invention discloses a modified lithium ion battery ternary positive electrode material and a preparation method and application thereof, and belongs to the field of lithium ion battery materials. The preparation method of the modified ternary positive electrode material comprises the following steps: (1) uniformly mixing DyCl3 and LiCl solid powder to obtain a precursor A; (2) mixing ternary positive electrode material powder with the precursor A to obtain a precursor B; then calcining to obtain an intermediate positive electrode material; (3) mixing the intermediate positive electrode material, 3-hexylthiophene and an organic solvent to obtain a suspension; and (4) mixing the suspension and ferric chloride for reaction to obtain a solid which is the modified ternary positive electrode material. The surface of the ternary positive electrode material is coated with Li-Dy-Cl and poly-3-hexylthiophene (P3HT), and the rate and cycle performance of the high-nickel ternary positive electrode material are improved through the coordination effect of Li-Dy-Cl and poly-3-hexylthiophene (P3HT).

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion battery materials, and specifically relates to a modified ternary cathode material for lithium-ion batteries, its preparation method and application. Background Art

[0002] With the progress of science and technology, the consumption of energy is increasing, and it is urgent to develop an efficient energy conversion and storage system and a safe and pollution-free green energy to achieve the goal of sustainable development. In recent years, lithium-ion batteries, as power sources, have very broad application prospects in portable electronic products, electric vehicles and energy storage fields. As one of the important components of lithium-ion batteries, the cathode material plays a crucial role in its capacity and cycling performance.

[0003] Common cathode materials include LiCoO2, LiNiO2, LiMnO2 and LiNi x Co y Mn 1-y-z O2 (NCM). Compared with other cathode materials, NCM has the advantages of low cost, large discharge capacity, good cycling performance, etc. In order to ensure a high capacity of the battery, one method is to increase the Ni content in NCM. However, as the Ni content increases, the number of phase transitions during charge and discharge increases. When the Ni content is 33%, there is only 1 pair of redox peaks in the cyclic voltammetry test, while when the Ni content is greater than 80%, 4 pairs of redox peaks will appear in the cyclic voltammetry test. The phase transition of H2-H3 occurring at 4.2V is the main reason for the capacity decay of the high-nickel ternary material. How to suppress the occurrence of the H2-H3 phase transition during the charge and discharge of the high-nickel ternary cathode material, so as to improve the rate performance and cycling performance of the high-nickel ternary cathode material is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a modified ternary cathode material for lithium-ion batteries, its preparation method and application. In the present invention, Li-Dy-Cl and poly(3-hexylthiophene) (P3HT) are coated on the surface of the ternary cathode material, and the coordinated action of the two improves the rate and cycling performance of the high-nickel ternary cathode material.

[0005] The present invention first provides a preparation method of a modified ternary cathode material, including the following steps:

[0006] (1) Mix solid powders of DyCl3 and LiCl evenly to obtain precursor A;

[0007] (2) Mix the ternary cathode material powder and the precursor A to obtain precursor B; then calcine to obtain an intermediate cathode material;

[0008] (3) Mix the intermediate cathode material, 3-hexylthiophene, and an organic solvent to obtain a suspension;

[0009] (4) Mix the suspension and iron chloride for reaction, and the obtained solid is the modified ternary cathode material.

[0010] In the present invention, a layer of Li-Dy-Cl is first coated on the surface of the ternary cathode material. Li-Dy-Cl has good ionic conductivity and chemical stability; this layer inhibits the occurrence of the H2-H3 phase transition during charge and discharge, ensuring the interfacial stability during charge and discharge; then a layer of poly-3-hexylthiophene is in-situ polymerized and coated on the outer layer; using in-situ polymerization coating can make the polymer form a continuous layered structure on the surface of the NCM material; the coordinated action of the two layers improves the rate and cycle performance of the high-nickel ternary cathode material.

[0011] For the preparation method of the above-mentioned modified ternary cathode material, in step (1), the solid powders of DyCl3 and LiCl are mixed in a ball mill;

[0012] In step (2), the ternary cathode material powder and the precursor A are mixed in a 3D mixer.

[0013] For the preparation method of the above-mentioned modified ternary cathode material, in step (1), the mass ratio of the total mass of the solid powders of DyCl3 and LiCl to the mass of zirconia balls is 1:(50 - 100), specifically 1:70;

[0014] The rotation speed of the ball mill is 500 - 600 r / min; the ball milling time is 15 - 20 h;

[0015] In step (2), the mixing frequency is 22.5 - 26.5 Hz, and the mixing time is 2 - 5 h.

[0016] For the preparation method of the above-mentioned modified ternary cathode material, in step (1), the molar ratio of DyCl3 to LiCl is (0.7 - 1.2):(1.8 - 2.5), specifically 1:2.5;

[0017] In step (2), the mass ratio of the ternary cathode material powder to the precursor A is (90 - 110):1;

[0018] The ternary cathode material is LiNi x CoyMn 1-x-y O2, where 0.6 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.3; specifically, x is 0.8 and y is 0.1;.

[0019] For the preparation method of the above-mentioned modified ternary cathode material, in step (2), the calcination temperature is 500 - 600 °C; the calcination time is 6 - 20 h;

[0020] The heating rate of the calcination is 2-10 °C·min -1 , specifically it can be 5 °C·min -1 ;

[0021] The environment of the calcination is oxygen.

[0022] In the preparation method of the above modified ternary cathode material, in step (3), the organic solvent is at least one of chloroform, dichloromethane and nitromethane;

[0023] The mass ratio of the intermediate cathode material to 3-hexylthiophene is 1:(0.005-0.02), specifically it can be 1:0.01, 1:0.005, 1:0.015;

[0024] The mass ratio of the intermediate cathode material to the volume of the organic solvent is 1 g:5-15 mL.

[0025] In the preparation method of the above modified ternary cathode material, in step (4), the mass ratio of 3-hexylthiophene and iron chloride in the suspension is 1:(0.3-2.0), specifically it can be 1:0.66, 1:1.3 or 1:0.44;

[0026] The reaction is to stir at 1-5 °C for 4-8 h;

[0027] The rotation speed of the stirring is 300-500 r / min.

[0028] In the preparation method of the above modified ternary cathode material, in step (4), there are also steps of centrifugation and drying after the reaction.

[0029] The present invention further provides a modified ternary cathode material prepared by the above preparation method.

[0030] The application of the above modified ternary cathode material in the preparation of the cathode of a lithium-ion battery also belongs to the protection scope of the present invention.

[0031] Finally, the present invention provides a battery cathode, and its active ingredient includes the above modified ternary cathode material.

[0032] A lithium-ion battery includes the above battery cathode.

[0033] The present invention has the following beneficial effects:

[0034] (1) The present invention uses a double-layer coating method to modify the LiNi x Co y Mn 1-y-z O2 (NCM) material, and a layer of Li 2.7 Dy1.1 C l6 (Li-Dy-Cl), Li-Dy-Cl has good ionic conductivity and chemical stability; this coating layer can accelerate the diffusion rate of Li + and, due to the existence of the coating layer interface, effectively inhibits the side reactions between the NCM surface and the electrolyte, inhibits the occurrence of the H2-H3 phase transition during charge and discharge, ensures the interface stability during charge and discharge, and thus improves the performance of the battery such as rate and cycle performance;

[0035] (2) On the basis of coating Li-Dy-Cl on the inner layer, the present invention in-situ polymerizes and coats a layer of poly(3-hexylthiophene) (P3HT) on the outer layer; using in-situ polymerization coating can enable the polymer to form a continuous layered structure on the surface of the NCM material. P3HT has excellent electrical conductivity, accelerates the transfer of internal Li + and improves the cycle performance of the battery;

[0036] (3) The modification method of the ternary cathode material of the lithium-ion battery of the present invention is simple, with rich raw materials, low energy consumption, safe and reliable production process, low production cost, and is easy to scale up production. Brief Description of the Drawings

[0037] Figure 1 It is the rate curve graphs of the cathode materials of Example 1 and Comparative Example 1 at 0.2C, 0.33C, 0.5C, 1C, 0.2C and the 50-cycle curve graph at 1C. Detailed Embodiments

[0038] The present invention will be further described in detail below in conjunction with the detailed embodiments. The embodiments given are only for clarifying the present invention, rather than limiting the scope of the present invention.

[0039] The experimental methods in the following embodiments are all conventional methods unless otherwise specified.

[0040] For the quantitative tests in the following embodiments, unless otherwise specified, three repeated experiments are set, and the results are averaged.

[0041] The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0042] Example 1

[0043] The modified ternary cathode material of this example is prepared through the following steps:

[0044] a. Place 57.6 mg of DyCl3 and 22.3 mg of LiCl in a ball milling jar. The mass ratio of the mixed powder to the zirconia balls is 1:70, the rotation speed is 550 r / min, and the ball milling time is 16 h;

[0045] 8 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder and the above-mentioned ball-milled powder are mixed using a 3D mixer. The mixing frequency is 25.8 Hz and the mixing time is 3.5 h to form a uniformly mixed black powder;

[0046] First, the uniformly mixed black powder is calcined at 550 °C for 16 h. All calcination environments are oxygen and the heating rate is 5 °C·min -1 , to obtain an intermediate cathode material;

[0047] b. 8 g of the intermediate cathode material and 0.08 g of 3-hexylthiophene liquid (the mass ratio of the intermediate cathode material to 3-hexylthiophene is 1:0.01) are ultrasonically dispersed in 60 mL of chloroform to obtain a first suspension;

[0048] 0.053 g of ferric chloride is added to the first suspension and stirred under the condition of a water bath. After centrifugation and drying, a modified ternary cathode material is obtained;

[0049] Among them, during the stirring process, the rotation speed is 400 r / min, the time is 6 h, and the water bath temperature is 2 °C.

[0050] Example 2

[0051] The preparation method of the modified ternary cathode material in this example is basically the same as that in Example 1, except that: the addition amount of 3-hexylthiophene is 0.04 g.

[0052] Example 3

[0053] The preparation method of the modified ternary cathode material in this example is basically the same as that in Example 1, except that: the addition amount of 3-hexylthiophene is 0.12 g.

[0054] Comparative Example 1

[0055] The cathode material in this comparative example is LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0056] Comparative Example 2

[0057] The preparation method of the modified ternary cathode material in this comparative example is basically the same as that in Example 1, except that: step b is not included, and the cathode material is formed through step a. The specific preparation method is as follows:

[0058] a. Place 57.6 mg of DyCl3 and 22.3 mg of LiCl in a ball milling jar. The mass ratio of the mixed powder to zirconia balls is 1:70, the rotation speed is 550 r / min, and the ball milling time is 16 h;

[0059] Put 8 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder and the above ball milled powder are mixed using a 3D mixer. The mixing frequency is 25.8 Hz and the mixing time is 3.5 h to form a uniformly mixed black powder;

[0060] First, calcine the uniformly mixed black powder at 550 °C for 16 h. All calcination environments are oxygen, and the heating rate is 5 °C·min -1 , to obtain an intermediate cathode material, that is, the modified ternary cathode material of this comparative example.

[0061] Comparative Example 3

[0062] The preparation method of the modified ternary cathode material in this comparative example is basically the same as that in Example 1, except that: step a is not included, and the intermediate cathode material in step b is replaced with LiNi 0.8 Co 0.1 Mn 0.1 O2. The specific preparation method is as follows:

[0063] Disperse 8 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder and 0.08 g of 3 - hexylthiophene liquid by ultrasonic in 60 mL of chloroform to obtain a first suspension;

[0064] Add 0.053 g of ferric chloride to the first suspension and stir under the condition of a water bath. After centrifugation and drying, a modified ternary cathode material is obtained;

[0065] Among them, during the stirring process, the rotation speed is 400 r / min, the time is 6 h, and the water bath temperature is 2 °C.

[0066] Example 4

[0067] Prepare the cathode sheets from the cathode materials in Examples 1 - 3 and Comparative Examples 1 - 3. The specific method is as follows: Dissolve the cathode material, Super P, and PVDF in NMP, stir for 2 h to form a cathode slurry, and coat the cathode slurry on both surfaces of the aluminum foil (surface density is 190 g / m 2 ), then vacuum dry at 110 °C for 20 h, and then perform rolling, slicing, and weighing to obtain the cathode sheet. In the cathode active layer, the mass ratio of the cathode material, Super P, and PVDF is 8:1:1;

[0068] In a glove box filled with argon gas, a CR2016 coin cell was assembled with a positive electrode sheet, a lithium metal sheet, and a separator prepared by a wet process (purchased from Enjie). The electrolyte consisted of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1, and the solute was 1.0 mol / L LiPF6.

[0069] The following performance tests were carried out on the assembled coin cells respectively. The test voltage range was 2.8 - 4.35 V. First, charge and discharge were carried out once at a constant current of 0.2C, 0.33C, and 0.1C respectively, then charge and discharge were carried out once at a constant current of 0.2C, and finally, charge and discharge were carried out 50 times in a cycle at a constant current of 1C. The test results are shown in Table 1 and Figure 1 。

[0070] Table 1 Electrochemical data of Examples 1 - 3 and Comparative Examples 1 - 3

[0071]

[0072] From the above data, it can be seen that compared with Comparative Examples 1 - 3, the discharge capacity of Examples 1 - 3 has been significantly improved, and at the same time, the initial efficiency has been significantly enhanced, which also indicates that the electrical properties of the material itself have been greatly improved after coating. At the same time, according to Figure 1 the cyclic voltammetry curves of Example 1 and Comparative Example 1 in [], it can also be clearly seen that the rate performance of the material has been significantly improved.

Claims

1. A preparation method of a modified ternary cathode material, comprising the following steps: (1) Mix solid powders of DyCl3 and LiCl evenly to obtain precursor A; (2) Mix the ternary cathode material powder and the precursor A to obtain precursor B; then carry out calcination to obtain an intermediate cathode material; (3) Mix the intermediate cathode material, 3-hexylthiophene and an organic solvent to obtain a suspension; (4) Mix the suspension and iron chloride for reaction, and the obtained solid is the modified ternary cathode material.

2. The preparation method of the modified ternary cathode material according to claim 1, characterized in that: In step (1), the solid powders of DyCl3 and LiCl are mixed in a ball mill; In step (2), the ternary cathode material powder and the precursor A are mixed in a 3D mixer.

3. The preparation method of the modified ternary cathode material according to claim 2, wherein: In step (1), the mass ratio of the total mass of the solid powders of DyCl3 and LiCl to the mass of zirconia balls is 1:(50 - 100); The rotation speed of the ball mill is 500 - 600 r / min; the ball milling time is 15 - 20 h; In step (2), the mixing frequency is 22.5 - 26.5 Hz, and the mixing time is 2 - 5 h.

4. The preparation method of the modified ternary cathode material according to any one of claims 1-3, characterized in that: In step (1), the molar ratio of DyCl3 to LiCl is (0.7 - 1.2):(1.8 - 2.5); In step (2), the mass ratio of the ternary cathode material powder to the precursor A is (90 - 110):1; The ternary cathode material is LiNi x CoyMn 1-x-y O2, where 0.6 ≤ x ≤ 1.0 and 0 ≤ y ≤ 0.

3.

5. The preparation method of the modified ternary cathode material according to any one of claims 1-3, characterized in that: In step (2), the calcination temperature is 500 - 600 °C; the calcination time is 6 - 20 h; The heating rate of the calcination is 2-10 °C·min -1 ; The calcination environment is oxygen.

6. The preparation method of the modified ternary cathode material according to any one of claims 1-3, characterized in that: In step (3), the organic solvent is at least one of chloroform, dichloromethane and nitromethane; The mass ratio of the intermediate cathode material to 3-hexylthiophene is 1:(0.005 - 0.02); The mass ratio of the intermediate cathode material to the volume of the organic solvent is 1 g:5 - 15 mL.

7. The preparation method of the modified ternary cathode material according to any one of claims 1-3, characterized in that: In step (4), the mass ratio of 3-hexylthiophene in the suspension to iron chloride is 1:0.3 - 2.0; The reaction is to stir at 1 - 5 °C for 4 - 8 h; The rotation speed of the stirring is 300 - 500 r / min.

8. The modified ternary cathode material prepared by the preparation method according to any one of claims 1 - 7.

9. A battery cathode, the active ingredient of which comprises the modified ternary cathode material according to claim 8.

10. A lithium-ion battery, which comprises the battery cathode according to claim 9.

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