Positive electrode material and preparation method and application thereof

Abstract

The present invention belongs to the field of lithium battery cathode materials, and discloses a cathode material, a preparation method thereof, and an application. The cathode material includes a substrate material, a first coating material, and a second coating material. The first coating material coats at least a part of the surface of the substrate material, and the second coating material coats at least a part of the surface of the particles formed by the substrate material and the first coating material; the substrate material is LiNi x Co y Mn z O2, where 0.7 ≤ x < 1, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.3, and x + y + z = 1; the first coating material is cobalt sulfide selenide (CoSSe); the second coating material is aluminum oxide. Through the double coating of CoSSe and aluminum oxide, the conductivity and reaction activity of the cathode material are enhanced, and the capacity attenuation is reduced, thereby improving the cycle life of the battery.

Description

Technical Field

[0001] The present invention belongs to the field of lithium battery positive electrode materials, and specifically relates to a positive electrode material and a preparation method and application thereof. Background Art

[0002] Ternary layered oxide materials (such as LiNi x Co y Mn z O2, referred to as NCM or NCA) is widely used in portable electronic devices, electric vehicles and large-scale energy storage systems due to its high energy density, low cost and good cycle performance.

[0003] In the prior art, the electrochemical performance of the positive electrode material is usually improved by coating the surface of the positive electrode material with substances such as Al2O3, MgO, ZnO, TiO2, LiMn2O4, FePO4, etc. The commonly used coating methods are: dispersing organic aluminum in distilled water, ultrasonicating, stirring, forming a layer of aluminum hydroxide on the surface of lithium cobalt oxide, and then heating to obtain the positive electrode material of lithium cobalt oxide coated with aluminum oxide. The product obtained by this method is uniformly coated and has greatly improved stability. Under the conditions of charge and discharge with a voltage range of 2.75-4.4V and a rate of 0.2C, the reversible specific capacity can reach 168mAh / g, but its cycle capacity retention rate is low, and the battery performance decreases after a certain period of use. Summary of the invention

[0004] In view of the defects and shortcomings of the prior art, in the first aspect, the present invention provides a positive electrode material; in the second aspect, the present invention provides a method for preparing the positive electrode material; in the third aspect, the present invention provides a battery.

[0005] In a first aspect, the present invention provides a positive electrode material, comprising a base material, a first coating material and a second coating material, wherein the first coating material is coated on at least a portion of the surface of the base material, and the second coating material is coated on at least a portion of the surface of particles formed by the base material and the first coating material; the base material is LiNi x Co y Mn z O2, wherein 0.7≤x<1, 0≤y≤0.2, 0<z≤0.3, and x+y+z=1; the first coating material is cobalt selenium sulfide (CoSSe); and the second coating material is aluminum oxide.

[0006] In a second aspect, the present invention provides a method for preparing a positive electrode material, comprising the following steps:

[0007] Step 1, Mixing CoSSe and Ni x Co y Mn z(OH)2, roasting to obtain intermediate product A; wherein 0.7≤x<1, 0≤y≤0.2, 0<z≤0.3, and x+y+z=1;

[0008] Step 2, mixing the intermediate product A and the lithium salt, and calcining to obtain the intermediate product B;

[0009] Step 3: Aluminum isopropoxide (C9H 21 AlO3) powder is dispersed in anhydrous ethanol to obtain a slurry, and then the intermediate product B is added to the slurry, and heated until the anhydrous ethanol is evaporated to dryness to obtain solid particles;

[0010] Step 4, calcining the solid particles, and obtaining the positive electrode material after cooling.

[0011] Preferably, in step 1, CoSSe and Ni x Co y Mn z The mass ratio of (OH)2 is 0.5~2:100.

[0012] Preferably, in step 1, the calcination temperature is 150-250° C. and the calcination time is 3-5 hours.

[0013] Preferably, in step 2, the lithium salt is any one or more of lithium carbonate and lithium hydroxide.

[0014] Preferably, in step 2, the molar ratio of the intermediate product A to the lithium in the lithium salt is 1:1.01-1.1.

[0015] Preferably, in step 2, the calcination temperature is 700-900° C. and the calcination time is 18-26 hours.

[0016] Preferably, in step 3, the concentration of aluminum isopropoxide in the slurry is 0.1-0.4 g / 100 mL.

[0017] Preferably, in step 3, the heating temperature is 80-120°C.

[0018] Preferably, in step 4, the calcination temperature is 300-500° C. and the calcination time is 3-7 hours.

[0019] In a third aspect, the present invention provides a battery, comprising the above-mentioned positive electrode material or the positive electrode material prepared by the above-mentioned preparation method.

[0020] Compared with the prior art, the present invention has the following obvious beneficial effects:

[0021] Cobalt selenium sulfide has a unique electronic structure and excellent catalytic performance, which can significantly accelerate the transmission process of lithium ions and electrons, thereby improving the charge and discharge rate and energy efficiency of the battery. The catalytic effect of CoSSe combined with the physical protection of alumina can effectively alleviate the structural collapse problem during the cycle process, thereby enhancing the cycle stability of the positive electrode material. The double coating of CoSSe and alumina not only enhances the conductivity and reaction activity of the positive electrode material, but also reduces capacity attenuation, thereby improving the cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Ni used in step 1 of Example 1 0.9 Co 0.05 Mn 0.05 SEM image of (OH)2 material;

[0023] Figure 2 is a SEM image of the intermediate product B obtained in step 2 of Example 1;

[0024] Figure 3 This is a SEM image of the CoSSe and alumina-coated positive electrode material obtained in step 4 of Example 1;

[0025] Figure 4 The positive electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3 and the uncoated LiNi 0.9 Co 0.05 Mn 0.05 Cycling performance test diagram of batteries assembled with O2. DETAILED DESCRIPTION

[0026] The present invention provides the following specific technical solutions.

[0027] In a first aspect, the present invention provides a positive electrode material, comprising a base material, a first coating material and a second coating material, wherein the first coating material is coated on at least a portion of the surface of the base material, and the second coating material is coated on at least a portion of the surface of particles formed by the base material and the first coating material; the base material is LiNi x Co y Mn z O2, wherein 0.7≤x<1, 0≤y≤0.2, 0<z≤0.3, and x+y+z=1; the first coating material is cobalt selenium sulfide (CoSSe); and the second coating material is aluminum oxide.

[0028] In the prior art, coating is a common method for modifying positive electrode materials. The Al2O3 coating layer can effectively block the direct contact between the positive electrode material and the electrolyte, thereby reducing side reactions and significantly enhancing the thermal stability and cycle stability of the material. However, relying solely on Al2O3 coating still has certain limitations in improving the cycle performance of positive electrode materials. Based on this, the inventors have found through research that cobalt selenium sulfide (CoSSe) has a unique electronic structure and excellent catalytic performance. Coating it on the surface of the positive electrode material can significantly accelerate the transmission process of lithium ions and electrons, thereby improving the cycle performance of the battery.

[0029] The inventors further discovered that by doubly coating the positive electrode material with CoSSe and alumina, the catalytic effect of CoSSe combined with the physical protection of alumina can effectively alleviate the structural collapse problem during the cycle, thereby enhancing the cycle stability of the positive electrode material; while enhancing the conductivity and reaction activity of the positive electrode material, it also reduces capacity attenuation and improves the cycle life of the battery.

[0030] In a second aspect, the present invention provides a method for preparing a positive electrode material, comprising the following steps:

[0031] Step 1, Mixing CoSSe and Ni x Co y Mn z (OH)2, calcined to obtain an intermediate product A; wherein 0.7≤x<1, 0≤y≤0.2, 0<z≤0.3, and x+y+z=1;

[0032] Step 2, mixing the intermediate product A and the lithium salt, and calcining to obtain the intermediate product B;

[0033] Step 3: Aluminum isopropoxide (C9H 21 AlO3) powder is dispersed in anhydrous ethanol to obtain a slurry, and then the intermediate product B is added to the slurry, and heated until the anhydrous ethanol is evaporated to dryness to obtain solid particles;

[0034] Step 4, calcining the solid particles, and obtaining the positive electrode material after cooling.

[0035] During the preparation process, CoSSe is coated on the surface of the precursor and then mixed with lithium and calcined, which can further optimize the ion transmission path of the material; then alumina is coated on the surface of the intermediate product B to consolidate the structural stability and thermal stability of the material.

[0036] Preferably, in step 1, CoSSe and Ni x Co y Mn z The mass ratio of (OH)2 is 0.5~2:100.

[0037] Excessive CoSSe coating may be detrimental to lithium ion migration and affect capacity, while too little CoSSe coating may not have a significant catalytic effect.

[0038] Preferably, in step 1, the calcination temperature is 150-250° C. and the calcination time is 3-5 hours.

[0039] Preferably, in step 2, the lithium salt is any one or more of lithium carbonate and lithium hydroxide.

[0040] Preferably, in step 2, the molar ratio of the intermediate product A to the lithium in the lithium salt is 1:1.01-1.1.

[0041] Preferably, in step 2, the calcination temperature is 700-900° C. and the calcination time is 18-26 hours.

[0042] The inventors have found that if the calcination temperature is too high after mixing the intermediate product A and the lithium salt, the material will lose water and become loose, causing the crystal structure to change, thereby affecting the charge and discharge capacity and battery cycle performance. If the calcination temperature is too low, the binding force between particles will be insufficient, the overall strength will be reduced, and the grain growth will be incomplete, which will also affect the electrochemical performance of the positive electrode material.

[0043] Preferably, in step 3, the concentration of aluminum isopropoxide in the slurry is 0.1-0.4 g / 100 mL.

[0044] Preferably, in step 3, the heating temperature is 80-120°C.

[0045] Preferably, in step 4, the calcination temperature is 300-500° C. and the calcination time is 3-7 hours.

[0046] In order to make the technical problems, technical solutions and technical advantages to be solved by the present invention more clear, they will be described in detail below with reference to specific examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0047] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0048] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0049] The CoSSe used in Examples 1 to 3 and Comparative Examples 1 to 3 was prepared by the following preparation method:

[0050] Step S1, add 0.1455g Co(NO3)2·6H2O, 0.0790g selenium powder, 0.0320g sulfur powder, 16mL ethylenediamine (EDA) and 4mL H2O into a 30mL reactor and stir evenly, then transfer the reactor to an oven at 180°C for 16 hours to obtain an intermediate product.

[0051] Step S2, washing the intermediate product by centrifugation, and then drying the intermediate product in an oven at 60° C. for 12 h to obtain a CoSSe sample.

[0052] Embodiment 1:

[0053] A method for preparing a positive electrode material comprises the following steps:

[0054] Step 1, Mixing CoSSe and Ni 0.9 Co 0.05 Mn 0.05 (OH)2 was then calcined at 250 °C for 4 h in an oxygen-containing atmosphere to obtain intermediate product A; CoSSe and Ni 0.9 Co 0.05 Mn 0.05 The mass ratio of (OH)2 is 1:100;

[0055] Step 2, after mixing the intermediate product A and lithium hydroxide, calcining at 800°C for 22h in an oxygen-containing atmosphere to obtain the intermediate product B; the molar ratio of the intermediate product A to the lithium in the lithium salt is 1:1.05; Step 3, 0.2g of aluminum isopropoxide (C9H 21 AlO3) powder was dispersed in 100 ml of anhydrous ethanol to obtain a slurry, and then 10 g of the intermediate product B was added to the slurry, and the mixture was stirred for 2 h to be uniformly mixed, and then heated and stirred at 120°C until the anhydrous ethanol was evaporated to dryness, and then filtered to obtain solid particles;

[0056] Step 4, heating to 400° C. at a heating rate of 3° C. / min and calcining the solid particles for 5 h in an oxygen-containing atmosphere, and obtaining a positive electrode material coated with CoSSe and alumina after cooling.

[0057] Figure 1 Ni used in step 1 of Example 1 0.9 Co 0.05 Mn 0.05 SEM image of (OH)2 material, Figure 1 You know 0.9 Co 0.05 Mn 0.05 The particles of (OH)2 material are spherical and have a smooth surface.

[0058] Figure 2 This is a SEM image of the intermediate product B (CoSSe-coated positive electrode material) obtained in step 2 of Example 1. Figure 2 It can be observed that the particle surface is Figure 1 It is relatively rough, which indirectly proves that CoSSe has been successfully coated on the surface of the positive electrode material.

[0059] Figure 3 is a SEM image of the positive electrode material obtained in step 4 of Example 1, Figure 3 The particle surface was observed to be relatively Figure 2 It is rougher than the surface of the positive electrode material, which indirectly proves that aluminum oxide has been coated on the surface of the positive electrode material.

[0060] Embodiment 2:

[0061] A method for preparing a positive electrode material comprises the following steps:

[0062] Step 1, Mixing CoSSe and Ni 0.8 Co 0.1 Mn 0.1 (OH)2 was then calcined at 150 °C for 3 h in an oxygen-containing atmosphere to obtain intermediate product A; CoSSe and Ni 0.8 Co 0.1 Mn 0.1 The mass ratio of (OH)2 is 0.5:100;

[0063] Step 2, after mixing the intermediate product A and lithium carbonate, calcining at 700°C for 18h in an oxygen-containing atmosphere to obtain the intermediate product B; the molar ratio of the intermediate product A to the lithium in the lithium salt is 1:1.01; Step 3, 0.1g of aluminum isopropoxide (C9H 21 AlO3) powder was dispersed in 100 ml of anhydrous ethanol to obtain a slurry, and then 10 g of the intermediate product B was added to the slurry, and the mixture was stirred for 2 h to be uniformly mixed, and then heated and stirred at 80°C until the anhydrous ethanol was evaporated to dryness, and then filtered to obtain solid particles;

[0064] Step 4, heating to 300° C. at a heating rate of 3° C. / min and calcining the solid particles for 3 h in an oxygen-containing atmosphere, and obtaining a positive electrode material coated with CoSSe and alumina after cooling.

[0065] Embodiment 3:

[0066] A method for preparing a positive electrode material comprises the following steps:

[0067] Step 1, Mixing CoSSe and Ni 0.7 Co 0.15 Mn 0.15 (OH)2 was then calcined at 250 °C for 4 h in an oxygen-containing atmosphere to obtain intermediate product A; CoSSe and Ni 0.7 Co 0.15 Mn 0.15 The mass ratio of (OH)2 is 2:100;

[0068] Step 2, mixing the intermediate product A and lithium hydroxide and calcining the mixture at 900° C. for 26 hours in an oxygen-containing atmosphere to obtain an intermediate product B; the molar ratio of the intermediate product A to the lithium in the lithium salt is 1:1.1;

[0069] Step 3: 0.4 g aluminum isopropoxide (C9H 21 AlO3) powder was dispersed in 100 ml of anhydrous ethanol to obtain a slurry, and then 10 g of the intermediate product B was added to the slurry, and the mixture was stirred for 2 h to be uniformly mixed, and then heated and stirred at 100 °C until the anhydrous ethanol was evaporated to dryness, and then filtered to obtain solid particles;

[0070] Step 4, heating to 500° C. at a heating rate of 3° C. / min and calcining the solid particles for 7 h in an oxygen-containing atmosphere, and obtaining a positive electrode material coated with CoSSe and alumina after cooling.

[0071] Comparative Example 1: A method for preparing a positive electrode material, comprising the following steps:

[0072] Step 1, Mixing CoSSe and Ni 0.9 Co 0.05 Mn 0.05 (OH)2 was then calcined at 250 °C for 4 h in an oxygen-containing atmosphere to obtain intermediate product A; CoSSe and Ni 0.9 Co 0.05 Mn 0.05 The mass ratio of (OH)2 is 1:100;

[0073] Step 2, mixing the intermediate product A and lithium hydroxide, wherein the molar ratio of the intermediate product A to the lithium in the lithium salt is 1:1.05, and calcining at 800° C. for 22 hours in an oxygen-containing atmosphere to obtain a positive electrode material.

[0074] Comparative Example 2: A method for preparing a positive electrode material, comprising the following steps:

[0075] Step 1: Ni 0.9 Co 0.05 Mn 0.05 (OH)2 was calcined at 250℃ for 4h in an oxygen-containing atmosphere to obtain intermediate product A;

[0076] Step 2, mixing the intermediate product A and lithium hydroxide and calcining the mixture at 800° C. for 22 hours in an oxygen-containing atmosphere to obtain an intermediate product B; the molar ratio of the intermediate product A to the lithium in the lithium salt is 1:1.05;

[0077] Step 3: 0.2 g aluminum isopropoxide (C9H 21AlO3) powder was dispersed in 100 ml of anhydrous ethanol to obtain a slurry, and then 10 g of the intermediate product B was added to the slurry, and the mixture was stirred for 2 h to be uniformly mixed, and then heated and stirred at 120°C until the anhydrous ethanol was evaporated to dryness, and then filtered to obtain solid particles;

[0078] Step 4, heating to 400° C. at a heating rate of 3° C. / min and calcining the solid particles for 5 h in an oxygen-containing atmosphere, and obtaining an alumina-coated positive electrode material after cooling.

[0079] Comparative Example 3:

[0080] A method for preparing a positive electrode material comprises the following steps:

[0081] Step 1: 0.2 g aluminum isopropoxide (C9H 21 AlO3) powder was dispersed in 100 ml of anhydrous ethanol to obtain a slurry, and then 10 g of Ni 0.9 Co 0.05 Mn 0.05 (OH)2 was added to the slurry, and the mixture was stirred for 2 h to be uniformly mixed, and then heated and stirred at 120°C until the anhydrous ethanol was evaporated to dryness, and then filtered to obtain the intermediate product A;

[0082] Step 2, calcining the intermediate product A, heating the temperature to 400° C. at a heating rate of 3° C. / min and calcining for 5 h in an oxygen-containing atmosphere to obtain an intermediate product B;

[0083] Step 3, mixing the intermediate product B and lithium hydroxide and calcining the mixture at 800° C. for 22 hours in an oxygen-containing atmosphere to obtain an intermediate product C; the molar ratio of the intermediate product B to the lithium in the lithium salt is 1:1.05;

[0084] Step 4, after mixing CoSSe and the intermediate product C, calcining at 250° C. for 4 h in an oxygen-containing atmosphere to obtain solid particles, wherein the mass ratio of CoSSe to the intermediate product C is 1:100.

[0085] The positive electrode materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 and the uncoated LiNi 0.9 Co 0.05 Mn 0.05O2 was prepared and ground according to the ratio of positive electrode material: conductive graphite: PVDF = 8:1:1, and then the mixed powder was dissolved in an appropriate amount of N-methylpyrrolidone (NMP) and stirred evenly to form a slurry. The slurry was then coated on the current collector aluminum foil and placed in a blast dryer at 90°C for 12 hours, and punched into a disc electrode with a diameter of 12 mm. The disc electrode was used as the positive electrode, the metal lithium sheet was used as the negative electrode, the lithium ion secondary electrolyte LB-037 (1M LiPF6 in DEC:EC:EMC=1:1:1 Vol%) was used as the electrolyte, and Celgard 2325 was used as the separator to assemble the LIR2032 button cell. The button cell was assembled in the glove box according to the assembly sequence of the button cell.

[0086] Test the electrical performance of the battery: In a 25℃ constant temperature box, charge the battery at a constant current rate of 0.1C to a voltage of 4.3V, then charge it at a constant voltage rate of 0.01C, and then discharge it at 0.1C to 3V. Repeat this cycle twice. Then charge the battery at a constant current rate of 0.5C to a voltage of 4.3V, then charge it at a constant voltage rate of 0.5C, and then discharge it at 0.5C to 3V. Record the charge and discharge capacity. The relationship between the number of cycles and the discharge specific capacity is as follows: Figure 4 shown.

[0087] Depend on Figure 4 It can be seen that the uncoated LiNi 0.9 Co 0.05 Mn 0.05 The capacity of the O2 positive electrode material is the lowest. By comparing Example 1 with Comparative Example 1 and Comparative Example 2, it can be seen that Example 1 has a more excellent discharge specific capacity and cycle stability, indicating that under the synergistic effect of CoSSe and alumina, the cycle performance and cycle life of the positive electrode material are further improved.

[0088] The embodiments described above are only preferred specific implementation modes 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 solutions and concepts of the present invention within the technical scope of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that: The invention comprises a base material, a first coating material and a second coating material, wherein the first coating material is coated on at least a part of the surface of the base material, and the second coating material is coated on at least a part of the surface of the particles formed by the base material and the first coating material; the base material is LiNi x Co y Mn z O2, wherein 0.7≤x<1, 0≤y≤0.2, 0<z≤0.3, and x+y+z=1; the first coating material is cobalt selenium sulfide (CoSSe); and the second coating material is aluminum oxide.

2. The method for preparing the positive electrode material according to claim 1, characterized in that: The steps include: Step 1, Mixing CoSSe and Ni x Co y Mn z (OH)2, roasting to obtain intermediate product A; wherein 0.7≤x<1, 0≤y≤0.2, 0<z≤0.3, and x+y+z=1; Step 2, mixing the intermediate product A and the lithium salt, and calcining to obtain the intermediate product B; Step 3: Aluminum isopropoxide (C9H 21 AlO3) powder is dispersed in anhydrous ethanol to obtain a slurry, and then the intermediate product B is added to the slurry, and the slurry is heated until the anhydrous ethanol is evaporated to dryness to obtain solid particles; Step 4, calcining the solid particles, and obtaining the positive electrode material after cooling.

3. The method for preparing the positive electrode material according to claim 2, characterized in that: In step 1, CoSSe and Ni x Co y Mn z The mass ratio of (OH)2 is 0.5~2:

100.

4. The method for preparing the positive electrode material according to claim 2, characterized in that: In step 1, the calcination temperature is 150-250° C. and the calcination time is 3-5 hours.

5. The method for preparing the positive electrode material according to claim 2, characterized in that: In step 2, the lithium salt is any one or more of lithium carbonate and lithium hydroxide; the molar ratio of the intermediate product A to the lithium in the lithium salt is 1:1.01-1.

1.

6. The method for preparing the positive electrode material according to claim 2, characterized in that: In step 2, the calcination temperature is 700-900° C. and the calcination time is 18-26 hours.

7. The method for preparing the positive electrode material according to claim 2, characterized in that: The concentration of aluminum isopropoxide in the slurry is 0.1-0.4 g / 100 mL.

8. The method for preparing the positive electrode material according to claim 2, characterized in that: In step 3, the heating temperature is 80-120°C.

9. The method for preparing the positive electrode material according to claim 2, characterized in that: In step 4, the calcination temperature is 300-500° C. and the calcination time is 3-7 hours.

10. A battery, characterized in that: Including the positive electrode material according to claim 1 or the positive electrode material prepared by the preparation method according to any one of claims 2 to 9.

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