A positive electrode active material, a method for manufacturing the same, a battery, and a device using electricity

Abstract

The application discloses a positive electrode active material, a preparation method thereof, a battery and a power utilization device. The positive electrode active material comprises a core layer and a coating layer arranged on the surface of the core layer, and the coating layer comprises a nanomaterial, and the nanomaterial comprises RuOCl and M2O3, wherein M comprises at least one of Al, Ga, In or Y. The application significantly improves the electrical performance of the positive electrode active material by coating the nanomaterial composed of RuOCl and M2O3 on the surface of the cobalt-free layered positive electrode active material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to a positive electrode active material, a preparation method thereof, a battery and an electric device. BACKGROUND

[0002] Lithium ion batteries, as the core of electric vehicles and energy storage and conversion, have attracted extensive attention. Studies have shown that the positive electrode active material plays a decisive role in the energy density, safety and service life of the battery. Among the many positive electrode active materials, ternary positive electrode active materials, especially high-nickel NCM, have been widely studied. However, the nickel-rich layered oxide positive electrode has many surface side effects and microstructure defects, such as residual lithium compounds, HF corrosion, structure degradation, intergranular / intragranular cracks, and low electrical conductivity during cycling, which ultimately leads to a decrease in the cycle life of the battery. In the absence of cobalt in the cobalt-free layered positive electrode material, the material has poor electronic conductivity, slow lithium ion migration speed, serious lithium-nickel mixing, and poor layered structure, which has a greater impact on the cycle life of the cobalt-free nickel-rich layered positive electrode active material. SUMMARY

[0003] The present application provides a positive electrode active material, a preparation method thereof, a battery and an electric device, which solves the problem of poor cycle performance of the current cobalt-free layered positive electrode active material.

[0004] According to the positive electrode active material provided by the first aspect of the present application, the positive electrode active material comprises a core layer and a coating layer arranged on the surface of the core layer, and the coating layer comprises a nanomaterial, and the nanomaterial comprises RuOCl and M2O3, wherein M comprises at least one of Al, Ga, In or Y.

[0005] Optionally, in other embodiments of the present application, the material of the core layer comprises a compound of the formula Li b Ni x Mn y O2, wherein 1.05≤b≤1.15, 0.5

[0006] Optionally, in other embodiments of the present application, the nanomaterial satisfies at least one of the following characteristics:

[0007] (a) the D50 of the nanomaterial is 50nm-200nm;

[0008] (b) the specific surface area of the nanomaterial is BET, the unit is m 2 / g, and satisfies: 1000≤BET≤1500.

[0009] Optionally, in other embodiments of the present application, the molar ratio of RuOCl and M2O3 is (0.01-0.05):1.

[0010] Optionally, in other embodiments of the present application, the material of the core layer is a layered single crystal material, and the material of the core layer satisfies at least one of the following characteristics:

[0011] (i) the D50 of the material of the core layer is 2 μm-4 μm;

[0012] (ii) the specific surface area of the material of the core layer is 0.4 m 2 / g-0.8 m 2 / g.

[0013] Optionally, in other embodiments of the present application, the mass ratio of the nanomaterial to the material of the core layer is (0.1-1) : 100.

[0014] According to the preparation method of the positive electrode active material provided by the second aspect of the present application, the method comprises:

[0015] providing a nanocarbon fiber paperboard;

[0016] dropping a mixed solution of RuCl3 and a chlorinated salt on the heated nanocarbon fiber paperboard to obtain a nanomaterial;

[0017] providing a core layer material;

[0018] mixing the nanomaterial and the core layer material and calcining to obtain the positive electrode active material.

[0019] Optionally, in other embodiments of the present application, the chlorinated salt comprises at least one of AlCl3, GaCl3, InCl3 or YCl3.

[0020] Optionally, in other embodiments of the present application, the core layer material comprises a compound of the formula Li b Ni x Mn y O2, wherein 1.05≤b≤1.15, 0.5

[0021] Optionally, in other embodiments of the present application, the heating temperature of the nanocarbon fiber paperboard is 300-400℃.

[0022] According to the battery provided by the third aspect of the present application, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on the positive electrode current collector, and the positive electrode active material layer comprises the positive electrode active material described above.

[0023] According to the power utilization device provided by the fourth aspect of the present application, the device comprises the battery described above.

[0024] The positive electrode active material according to the embodiments of the present application has at least the following technical effects:

[0025] The positive electrode active material of the present application comprises a coating layer, the coating layer comprises a nanomaterial, the nanomaterial comprises RuOCl and M2O3. Because the active sites of Ru are many, RuOCl is dispersed into M2O3 with high acid resistance and high oxidation resistance, the oxidation potential is increased and the corrosion of RuOCl is slowed down, and the synergistic effect of the two makes the nanomaterial have excellent conductivity and stability. Then the nanomaterial is mixed and coated with the core layer, which significantly improves the electrical performance of the positive electrode active material, especially the cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 is an electron microscope characterization test diagram of the surface morphology of the positive electrode active material provided by the embodiments of the present application;

[0028] Figure 2 is a flow chart of the preparation method of the positive electrode active material provided by the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] In the specification, the numerical range shown by "~" indicates a range including the minimum value and the maximum value respectively recorded before and after "~".

[0031] The embodiments of the present application provide a positive electrode active material, a preparation method thereof, a battery and an electric device. The following will be described in detail respectively. It should be noted that the description order of the following embodiments is not limited as the preferred order of the embodiments.

[0032] The first aspect of the present application provides a positive electrode active material, comprising a core layer and a coating layer arranged on the surface of the core layer, the coating layer comprises a nanomaterial, the nanomaterial comprises RuOCl and M2O3, wherein M comprises at least one of Al, Ga, In or Y. The nanomaterial is denoted as RuOCl@M2O3, as shown in Figure 1The electron microscope characterization test diagram of the surface morphology of the positive electrode active material is shown. Due to the high activity site of Ru, RuOCl is dispersed into M2O3 with high acid resistance and high oxidation resistance, which increases the oxidation potential and slows down the corrosion of RuOCl, and the synergistic effect of the two makes the nanomaterial have excellent conductivity and stability. Then the nanomaterial is mixed and coated with the core layer, which significantly improves the electrical performance of the positive electrode active material, especially the cycle performance.

[0033] In some embodiments of the present application, the material of the core layer comprises a compound of Li b Ni x Mn y O2, wherein 1.05≤b≤1.15, 0.5

[0034] In some embodiments of the present application, the D50 of the nanomaterial can be 50nm-200nm, for example, it can be 70nm, 80nm, 90nm, 110nm, 120nm, 160nm, 170nm or a range formed by any two of them. In some embodiments of the present application, the D50 of the nanomaterial can also be 100nm-180nm. In some embodiments of the present application, the D50 of the nanomaterial can also be 130nm-150nm. The particle size of the nanomaterial is in nanometer level, which makes the coating effect better.

[0035] In some embodiments of the present application, the specific surface area BET of the nanomaterial, unit m 2 / g, satisfies: 1000≤BET≤1500, for example, it can be 1050, 1150, 1250, 1350, 1450 or a range formed by any two of them. In some embodiments of the present application, 1100≤BET≤1400. In some embodiments of the present application, 1200≤BET≤1300. The nanomaterial has a large specific surface area, which is beneficial to improve the coating effect.

[0036] In some embodiments of the present application, the molar ratio of RuOCl and M2O3 can be (0.01-0.05):1, also can be (0.02-0.04):1, also can be 0.03:1. When the molar ratio of RuOCl and M2O3 is in this range, the nanomaterial has excellent conductivity while also increasing the stability of the material, so that the conductivity and stability are balanced. Below this molar ratio range, the activity site is less, the conductivity is weakened, and above this molar ratio range, the material stability is poor.

[0037] In some embodiments of the present application, the material of the core layer is a layered single crystal material, and the D50 of the material of the core layer can be 2-4 μm, for example, 2.2 μm, 2.3 μm, 2.5 μm, 2.7 μm, 2.8 μm or a range formed by any two of them. When the D50 of the material of the core layer is in this range, the direct current resistance (DCR) is low, the capacity is normal, and the cycle stability is better. When the D50 of the material of the core layer is lower than this range, the DCR is low, the capacity is high, but the cycle stability is poor, the gas production is serious, and the safety performance is poor; when the D50 of the material of the core layer is higher than this range, the DCR increases, and the capacity is low.

[0038] In some embodiments of the present application, the specific surface area of the material of the core layer can be 0.4 m 2 / g-0.8 m 2 / g, for example, 0.45 m 2 / g, 0.55 m 2 / g, 0.65 m 2 / g, 0.75 m 2 / g or a range formed by any two of them. In some embodiments of the present application, the specific surface area of the material of the core layer can also be 0.5 m 2 / g-0.7 m 2 / g. In some embodiments of the present application, the specific surface area of the material of the core layer can also be 0.6 m 2 / g. The material of the core layer with a specific surface area in this range has less fine powder and a smoother particle surface. When the specific surface area of the material of the core layer is higher than this range, the fine powder is more, the surface is rough, and the stability of the material of the core layer is poor.

[0039] In some embodiments of the present application, the mass ratio of the nanomaterial to the material of the core layer can be (0.1-1) : 100, (0.2-0.8) : 100 or (0.5-0.7) : 100. When the mass ratio of the nanomaterial to the material of the core layer is in this range, the coating effect of the nanomaterial is good, the positive electrode active material has good conductivity and good cycle performance. When the mass ratio is lower than this range, the thickness of the coating layer is small, and the positive electrode active material has poor cycle performance; when the mass ratio is higher than this range, the coating layer is thick, which hinders the diffusion of ions and cannot develop the capacity.

[0040] Correspondingly, the second aspect of the present application provides a preparation method of a positive electrode active material, as shown in formula (I), comprising: Figure 2

[0041] S1: providing a nanocarbon fiber paper board;

[0042] S2: dropping a mixed solution of RuCl3 and a chloride salt on the heated nanocarbon fiber paper board to obtain a nanomaterial;

[0043] ​S3: providing a core layer material;

[0044] S4: mixing the nanomaterial and the core layer material and calcining to obtain the positive electrode active material.

[0045] The obtained positive electrode active material is a cobalt-free layered single-crystal positive electrode active material, denoted as Li b Ni x Mn y O2@aRuOCl@M2O3, wherein a is the molar ratio of RuOCl to M2O3.

[0046] The nanomaterial is prepared by dropping a mixed solution of RuCl3 and a chlorinated salt into a heated carbon nanofiber paperboard (CFP) in the present application. Due to the porous structure of the nanometer CFP, the prepared nanomaterial has a large specific surface area and a nanometer level particle size, which is beneficial to the coating effect in the later stage.

[0047] In some embodiments of the present application, the chlorinated salt includes at least one of AlCl3, GaCl3, InCl3 or YCl3.

[0048] In some embodiments of the present application, the core layer material includes a compound of the chemical formula Li b Ni x Mn y O2, wherein 1.05≤b≤1.15, 0.5

[0049] In some embodiments of the present application, the heating temperature of the carbon nanofiber paperboard can be 300℃-400℃, or 320℃-380℃, or 350℃-370℃. The heating temperature in this range can make the obtained nanomaterial have a lighter degree of agglomeration and a larger specific surface area.

[0050] Specifically, in step S4, the calcination temperature can be 300℃-400℃, or 320℃-380℃, or 350℃-370℃; the calcination time can be 4-8 hours, or 5-7 hours, or 6 hours; and the calcination atmosphere is oxygen or air.

[0051] In specific implementation, the preparation method of the positive electrode active material includes:

[0052] 1) The carbon nanofiber paperboard (CFP) is first cleaned with acetone, ethanol and deionized water in sequence, and then heated and treated on a hot plate at 250℃-300℃, and left still in air for 20 min.

[0053] 2) Take an appropriate amount of RuCl3 and chlorinated salt, dissolve in 100 mL of deionized water. Then drop the mixed solution on the nano CFP heated to 300-400°C, continue to heat for 10-30 min, get nanomaterials.

[0054] 3) Provide the core layer material.

[0055] 4) Mix the nanomaterial obtained in (2) with the core layer material in (3) according to a certain proportion (0.1%-1% of nanomaterial to core layer material), stir in a high-speed mixer at 3000-4000 rpm for 20-30 min, then calcine the obtained mixture, the calcination temperature is 300-500°C, the calcination time is 4-8 h, the calcination atmosphere is oxygen or air, to obtain the positive electrode active material.

[0056] In addition, the third aspect of the application provides a battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer comprising the above-mentioned positive electrode active material.

[0057] In specific implementation, the above-mentioned positive electrode active material, conductive agent, binder and solvent are stirred uniformly, and then subjected to processes such as sieving, coating, rolling, slitting and cutting to form the positive electrode sheet.

[0058] Specifically, the type of conductive agent is not limited, and any known conductive agent can be used. Examples of the conductive agent can include, but are not limited to, natural graphite, artificial graphite, Super P conductive carbon black, acetylene black, needle coke, carbon nanotubes, graphene and other carbon materials. The above-mentioned positive electrode conductive agent can be used alone or in any combination.

[0059] The type of binder used in the manufacture of the positive electrode active material layer is not particularly limited, and in the case of a coating method, it is only required to be a material that can be dissolved or dispersed in the liquid medium used in the electrode manufacturing process. Examples of the binder can include, but are not limited to, one or more of the following: polyethylene, polypropylene, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, etc. The above-mentioned binder can be used alone or in any combination.

[0060] The type of solvent used to form the positive electrode slurry is not limited, as long as it is a solvent that can dissolve or disperse the positive electrode active material, conductive agent and binder. Examples of the solvent used to form the positive electrode slurry can include any one of water-based solvents and organic-based solvents. Examples of the water-based medium can include, but are not limited to, water and a mixed medium of alcohol and water, etc. Examples of the organic-based medium can include, but are not limited to, hexane, benzene, toluene, xylene, pyridine, acetone, tetrahydrofuran (THF), N-methyl pyrrolidone (NMP), etc.

[0061] Specifically, the battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, and the positive electrode sheet is the positive electrode sheet described above. In specific implementation, the positive electrode sheet described above is assembled with the negative electrode sheet, the separator and the electrolyte to form a lithium ion battery. The negative electrode material used in the negative electrode sheet can be one or more of artificial graphite, natural graphite, mesocarbon microbeads, amorphous carbon, lithium titanate or silicon-carbon alloy. The negative electrode material also needs to have high compaction density, high mass specific capacity and high volume specific capacity.

[0062] The fourth aspect of the application provides a power consumption device comprising the battery described above.

[0063] In some embodiments, the power consumption device of the application is, but is not limited to, a backup power supply, an electric motor, an electric vehicle, an electric motorcycle, a power-assisted bicycle, a bicycle, an electric tool, a household large storage battery and the like.

[0064] The following will be described in conjunction with specific embodiments.

[0065] Embodiment 1,

[0066] The embodiment provides a preparation method of the positive electrode active material, comprising the following steps:

[0067] 1) The nanocarbon fiber paperboard (CFP) is sequentially cleaned with acetone, ethanol and deionized water, and then heated and treated on a hot plate at 250°C, and left still in air for 20 min;

[0068] 2) 0.85g of RuCl3 and 53.87g of AlCl3 are weighed and dissolved in 100mL of deionized water to prepare a mixed solution. Then the mixed solution is dropped on the nanometer CFP heated to 350°C, and continues to be heated for 20 min. The prepared nanomaterial 0.02RuOCl@Al2O3 has a median particle size D50 of 89nm and a BET of 1347m 2 / g;

[0069] 3) A cobalt-free single-crystal layered core layer material Li 2 Ni 1.1 Mn 0.75 O2 with a median particle size D50 of 2.88μm and a specific surface area of 0.49m 0.25 / g is provided;

[0070] 4) The nanomaterial and the core layer material obtained above are mixed at a mass ratio of 0.4:100 at high speed, stirred at 3500rpm for 25 min, and calcined at 350°C for 5h in an oxygen atmosphere, to obtain the finished positive electrode active material Li 1.1 Ni 0.75 Mn 0.25 O2@0.02RuOCl@Al2O3.

[0071] Example 2,

[0072] The preparation method of the positive electrode active material of Example 2 is the same as that of Example 1, except that 0.85 g of RuCl3 and 71.14 g of GaCl3 are weighed to form a mixed solution, and finally the finished positive electrode active material Li 1.1 Ni 0.75 Mn 0.25 O2@0.02RuOCl@Ga2O3.

[0073] Example 3,

[0074] The preparation method of the positive electrode active material of Example 3 is the same as that of Example 1, except that 0.42 g of RuCl3 and 53.87 g of AlCl3 are weighed to form a mixed solution, and finally the finished positive electrode active material Li 1.1 Ni 0.75 Mn 0.25 O2@0.01RuOCl@Al2O3.

[0075] Example 4,

[0076] The preparation method of the positive electrode active material of Example 4 is the same as that of Example 1, except that 2.11 g of RuCl3 and 53.87 g of AlCl3 are weighed to form a mixed solution, and finally the finished positive electrode active material Li 1.1 Ni 0.75 Mn 0.25 O2@0.05RuOCl@Al2O3.

[0077] Example 5,

[0078] The preparation method of the positive electrode active material of Example 5 is the same as that of Example 1, except that the median particle size D50 of the core layer material provided is 3.42 μm, and the specific surface area is 0.41 m 2 / g.

[0079] Example 6,

[0080] The preparation method of the positive electrode active material of Example 6 is the same as that of Example 1, except that the median particle size D50 of the core layer material provided is 2.26 μm, and the specific surface area is 0.69 m 2 / g.

[0081] Example 7,

[0082] The preparation method of the positive electrode active material of Example 7 is the same as that of Example 1, except that the mass ratio of the nanomaterial and the core layer material is 0.1:100.

[0083] Example 8,

[0084] The preparation method of the positive electrode active material of Example 8 is the same as that of Example 1, except that the mass ratio of the nanomaterial and the core layer material is 1:100.

[0085] Comparative Example 1,

[0086] The preparation method of the positive electrode active material of Comparative Example 1 is the same as that of Example 1, except that the same proportion of Al2O3 is coated directly on the surface of the provided cobalt-free layered core layer material.

[0087] Comparative Example 2,

[0088] The preparation method of the positive electrode active material of Comparative Example 2 is the same as that of Example 1, except that 4.23 g of RuCl3 and 53.87 g of AlCl3 are weighed to make a mixed solution, and finally the finished positive electrode active material Li 1.1 Ni 0.75 Mn 0.25 O2@0.1RuOCl@Al2O3.

[0089] Comparative Example 3,

[0090] The preparation method of the positive electrode active material of Comparative Example 3 is the same as that of Example 1, except that the mass ratio of the nanomaterial and the core layer material is 1.5:100.

[0091] The positive electrode active materials prepared in the examples and comparative examples, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) are added to N-methyl pyrrolidone (NMP) in a mass ratio of 92:4:4, mixed uniformly, and then coated on an aluminum foil. After drying at 100°C for 4h, the positive electrode sheet is cut into a diameter of 12mm, assembled into a button half cell, and left to stand for 12h. Electrochemical tests are performed.

[0092] The test method is as follows, and the results are shown in Table 1:

[0093] Capacity test: using a new Wei or blue electric detection cabinet, 0.1C charging, cut-off voltage 4.3V, 0.1C discharging, cut-off voltage 3V.

[0094] Cycle test: using a new Wei or blue electric detection cabinet, 0.5C charging, cut-off voltage 4.3V, 1C discharging, cut-off voltage 3V, and cycling for 50 cycles.

[0095] Table 1

[0096]

[0097]

[0098] Comparing Examples 1-8 and Comparative Example 1, the discharge capacity and cycle retention rate of Examples 1-8 are higher than that of Comparative Example 1, and Examples 1-8 are coated with the nanomaterial of the application, while Comparative Example 1 is only coated with Al2O3, which shows that the nanomaterial of the application can significantly improve the electrical properties of the positive active material, including the cycle performance.

[0099] Comparing Examples 1-4 and Comparative Example 2, the discharge capacity and cycle retention rate of Examples 1-4 are higher than that of Comparative Example 2, and the molar ratio of RuOCl and Al2O3 in Examples 1-4 is within the range of the application, which shows that when the molar ratio of RuOCl and Al2O3 is within the range of the application, the nanomaterial prepared has better stability, and the effect of coating the nanomaterial is better, which can significantly improve the electrical properties of the positive active material.

[0100] Comparing Examples 7-8 and Comparative Example 3, the discharge capacity and cycle retention rate of Examples 7-8 are higher than that of Comparative Example 3, and the mass ratio of the nanomaterial and the core layer material in Examples 7-8 is within the range of the application, which shows that when the mass ratio of the nanomaterial and the core layer material is within the range of the application, the effect of coating the nanomaterial is better, which can significantly improve the electrical properties of the positive active material, the positive active material has good conductivity and excellent cycle performance.

[0101] The application significantly improves the electrical properties of the positive active material by coating the surface of the cobalt-free layered positive active material with a nanomaterial composed of RuOCl and M2O3.

[0102] The above provides a detailed introduction to the positive active material, its preparation method, battery and electrical device provided by the application, and the principles and implementation modes of the application are described by applying specific examples; the above examples are only used to help understand the method and core idea of the application; at the same time, for those skilled in the art, according to the idea of the application, the specific implementation mode and application range will be changed, and the above description should not be understood as a limitation of the application.

Claims

1. A positive electrode active material, characterized in that, It includes a core layer and a coating layer disposed on the surface of the core layer, the coating layer including nanomaterials, the nanomaterials including RuOCl and M2O3, wherein M includes at least one of Al, Ga, In or Y; The method for preparing the positive electrode active material includes: We provide nano-carbon fiber paperboard; A mixed solution of RuCl3 and chloride salt was added dropwise onto the heated carbon nanofiber paperboard to obtain nanomaterials; Provide core layer material; The nanomaterial and the core layer material are mixed and calcined to obtain the positive electrode active material.

2. The positive electrode active material according to claim 1, characterized in that, The core layer material includes Li b Ni x Mn y Compounds of O2, wherein 1.05 ≤ b ≤ 1.15, 0.5 < x < 1, x + y = 1.

3. The positive electrode active material according to claim 1, characterized in that, The nanomaterial satisfies at least one of the following characteristics: (a) The D50 of the nanomaterial is 50 nm to 200 nm; (b) The specific surface area (BET) of the nanomaterial, in m² 2 / g, satisfying: 1000≤BET≤1500.

4. The positive electrode active material according to claim 1, characterized in that, The molar ratio of RuOCl to M2O3 is (0.01 to 0.05):

1.

5. The positive electrode active material according to claim 1, characterized in that, The core layer is a layered single-crystal material, and the material of the core layer satisfies at least one of the following characteristics: (i) The D50 of the core layer material is 2μm to 4μm; (ii) The specific surface area of ​​the core layer material is 0.4 m². 2 / g~0.8m 2 / g.

6. The positive electrode active material according to claim 1, characterized in that, The mass ratio of the nanomaterial to the core layer material is (0.1-1):

100.

7. The positive electrode active material according to claim 1, characterized in that, The chloride salt includes at least one of AlCl3, GaCl3, InCl3, or YCl3; and / or, The heating temperature of the nano-carbon fiber paperboard is 300℃~400℃.

8. A battery, comprising a positive electrode, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer disposed on the positive current collector, wherein the positive active material layer includes the positive active material as described in any one of claims 1 to 7.

9. An electrical device, characterized in that, It includes the battery as described in claim 8.

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