Positive electrode sheet, method for manufacturing same, electrode assembly, energy storage device, and electric device

Abstract

The application discloses a positive electrode sheet and a preparation method thereof, an electrode assembly, an energy storage device and an electric equipment. The positive electrode sheet comprises a current collector and a composite active material coated on the surface of the current collector, and the composite active material comprises a core and a shell layer coated on the surface of the core. The core comprises a first lithium-rich manganese-based material, and the shell layer comprises a second lithium-rich manganese-based material. The first lithium-rich manganese-based material is a lithium-rich manganese-based recycled material obtained through a recycling process, and the second lithium-rich manganese-based material is a newly prepared lithium-rich manganese-based material. The average particle size of the core is 0.08-0.5 times the average particle size of the composite active material. The positive electrode active material realizes waste recycling, and because the core and the shell layer are materials of the same type, the two have good compatibility, the preparation is convenient, the battery has high capacity performance, the cost of the positive electrode material is reduced, and high economic value is obtained.

Description

TECHNICAL FIELD

[0001] The present application generally relates to the field of new energy, and in particular to a positive electrode sheet, a preparation method thereof, an electrode assembly, an energy storage device and an electric device. BACKGROUND

[0002] The production process of lithium batteries produces a large amount of positive electrode sheet waste, such as serious waste in the cutting process; the production cost of lithium batteries made of lithium-rich manganese-based positive electrode materials is more than three times that of lithium iron phosphate materials, so it has high economic value to introduce lithium-rich manganese-based recycled materials as positive active materials and improve the battery performance. SUMMARY

[0003] In view of the above defects or deficiencies in the prior art, it is desirable to provide a positive electrode sheet, a preparation method thereof, an electrode assembly, an energy storage device and an electric device.

[0004] In a first aspect, the present application provides a positive electrode sheet, comprising a current collector and a composite active material coated on the surface of the current collector, the composite active material comprising a core and a shell layer coated on the surface of the core, the core comprising a first lithium-rich manganese-based material, and the shell layer comprising a second lithium-rich manganese-based material, wherein the first lithium-rich manganese-based material is a lithium-rich manganese-based recycled material obtained through a recycling process, and the second lithium-rich manganese-based material is a newly prepared lithium-rich manganese-based material; the average particle size of the core is 0.08-0.5 times the average particle size of the composite active material.

[0005] As an optional solution, the average particle size of the composite active material is 5-8 um.

[0006] As an optional solution, the average particle size of the first lithium-rich manganese-based material is 0.4-1.2 um; preferably, the average particle size of the first lithium-rich manganese-based material is 0.8-1.0 um.

[0007] As an optional solution, the chemical formula of the active material is xLi2MnO3(1-x)LiMO2, wherein M=Ni or Mn, and 0

[0008] In a second aspect, the present application provides a preparation method of the positive electrode sheet of the first aspect, comprising the following steps:

[0009] Separating and processing a scrapped lithium-rich manganese-based positive electrode sheet to obtain an active material containing lithium-rich manganese-based material;

[0010] Ball milling the active material containing lithium-rich manganese-based material and drying to obtain a first lithium-rich manganese-based material powder;

[0011] Configuring a mixed metal salt solution containing manganese salt and M metal salt, and a precipitant solution and a complexing agent solution;

[0012] The first lithium-rich manganese-based material powder, the mixed metal salt solution, the precipitant solution and the complexing agent solution are mixed to obtain a mixed solution, and the mixed solution is placed into a reaction kettle to perform a precipitation combination reaction, and then the composite active material precursor is obtained through solid-liquid separation, washing and drying.

[0013] The composite active material precursor is mixed with a carbon source and a lithium source to perform heat treatment to obtain the composite active material.

[0014] The composite active material, the positive electrode conductive agent and the binder are stirred and slurried with the solvent NMP according to the mass ratio (85%-95%):(1%-5%):(1%-5%) to obtain a positive electrode slurry, and then the positive electrode slurry is coated, dried, rolled and cut on an aluminum foil to obtain a positive electrode sheet.

[0015] As an optional solution, a process of separating and processing the scrapped lithium-rich manganese-based positive electrode sheet to obtain the active material containing the lithium-rich manganese-based material includes:

[0016] The scrapped lithium-rich manganese-based positive electrode sheet is soaked in deionized water until the aluminum foil is separated from the active material containing the lithium-rich manganese-based material to obtain the active material containing the lithium-rich manganese-based material.

[0017] As an optional solution, in the process of ball milling the active material containing the lithium-rich manganese-based material and drying to obtain the first lithium-rich manganese-based material powder, the drying method is spray drying.

[0018] As an optional solution, in the process of mixing the first lithium-rich manganese-based material powder, the mixed metal salt solution, the precipitant solution and the complexing agent solution to obtain the mixed solution and placing the mixed solution into the reaction kettle to perform the precipitation combination reaction, the pH value of the mixed solution is maintained at 10-12, the temperature of the precipitation combination reaction is 100℃-120℃, and the time is 5h-10h.

[0019] As an optional solution, in the process of mixing the composite active material precursor with a carbon source and a lithium source to perform heat treatment to obtain the composite active material, the temperature of the heat treatment is 700℃-750℃, and the time is 3h-5h.

[0020] In a third aspect, the present application provides an electrode assembly, including the positive electrode sheet of the first aspect.

[0021] In a fourth aspect, the present application provides an energy storage device, including the positive electrode sheet of the first aspect or the electrode assembly of the third aspect.

[0022] In a fifth aspect, the present application provides an electric device, including the energy storage device of the fourth aspect, and the energy storage device supplies power to the electric device.

[0023] The positive electrode sheet provided by the application solves the problems of high cost of the existing lithium-rich manganese-based positive electrode material and poor performance of the lithium-rich manganese-based recycled material battery by taking the recycled lithium-rich manganese-based recycled material as the core and the newly prepared lithium-rich manganese-based material as the shell to obtain the composite positive electrode material. The composite active material provided by the application takes the lithium-rich manganese-based recycled material as the core and the newly prepared lithium-rich manganese-based material as the shell, realizes waste recycling, and has good compatibility between the core and the shell due to the same type of materials, is convenient to prepare, ensures high capacity performance of the battery, reduces the cost of the positive electrode material, and has high economic value. BRIEF DESCRIPTION OF DRAWINGS

[0024] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments made with reference to the drawings:

[0025] Figure 1 The particle size distribution diagram of the lithium-rich manganese-based recycled material and the composite active material of Example 1 of the application;

[0026] Figure 2 The particle morphology of the composite active material of Example 1 of the application;

[0027] Figure 3 The XRD diagram of the composite active material of Example 1 of the application. DETAILED DESCRIPTION

[0028] The application will be further described in detail below with reference to the examples. It can be understood that the specific examples described herein are only used to explain the related application, and not to limit the application.

[0029] It should be noted that the examples in the application and the features in the examples can be combined with each other without conflict. The application will be described in detail below with reference to the examples.

[0030] In a first aspect, the examples of the application provide a positive electrode sheet, which comprises a current collector and a composite active material coated on the surface of the current collector, the composite active material comprises a core and a shell coated on the surface of the core, the core comprises a first lithium-rich manganese-based material, and the shell comprises a second lithium-rich manganese-based material, wherein the first lithium-rich manganese-based material is a lithium-rich manganese-based recycled material obtained through a recycling process, and the second lithium-rich manganese-based material is a newly prepared lithium-rich manganese-based material; the average particle size of the core is 0.08-0.5 times the average particle size of the composite active material.

[0031] It can be understood that the current collector can be an aluminum foil or a copper foil, etc., and the examples of the application do not limit this.

[0032] When the particle size of the lithium-rich manganese-based material is relatively large, the lithium ions inside the lithium-rich manganese-based material are generally difficult to participate in electrochemical reactions, and do not play a significant role, i.e., forming "dead lithium". By taking the lithium-rich manganese-based recycled material as the core and the newly prepared lithium-rich manganese-based material as the shell coated on the surface of the lithium-rich manganese-based recycled material, the two can be well compatible, the preparation method is simple, and the waste recycling and reuse are realized, thereby reducing the generation cost and obtaining high economic value, while the battery performance of the composite positive electrode material with the lithium-rich manganese-based material is also ensured.

[0033] The lithium-rich manganese-based material is a kind of substance, and can be any existing lithium-rich manganese-based material with a specific structural formula, for example, can be xLi2MnO3(1-x)LiNi 0.5 Mn 0.5 O2, Li2MnO3LiNi 1-x Mn x O2, wherein 0 < x < 1, and the specific structure of the above three substances is not limited in the embodiments of the present application.

[0034] It can also be understood that the lithium-rich manganese-based recycled material as the core is mainly used to support the newly prepared lithium-rich manganese-based material coated on the outer layer, reduce the use of the newly prepared lithium-rich manganese-based material, and reduce the cost of the positive electrode sheet. Therefore, in order to ensure that the composite active material has good battery performance, the particle size of the core should not be too large. In the embodiments of the present application, the particle size of the core is 0.08-0.5 times the particle size of the composite active material, for example, can be 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, etc. The particle size here refers to the average particle size, which can be represented by D50 in specific embodiments. D50 is the median particle size, which is the particle size corresponding to 50% of the cumulative particle size distribution percentage of a sample.

[0035] The size of the core in the embodiments of the present application is beneficial to reduce the cost of the composite active material while ensuring that the newly prepared lithium-rich manganese-based material of the shell layer can reliably coat the lithium-rich manganese-based recycled material core, thereby ensuring that the newly prepared lithium-rich manganese-based material can better perform and have good battery performance.

[0036] The positive electrode sheet of the embodiments of the present application solves the problems of high cost of the existing lithium-rich manganese-based positive electrode material and poor battery performance of the lithium-rich manganese-based recycled material. The composite active material of the embodiments of the present application takes the lithium-rich manganese-based recycled material as the core and the newly prepared lithium-rich manganese-based material as the shell layer, realizes waste recycling and reuse, and because the core and the shell layer are the same type of material, they have good compatibility, the preparation is convenient, the battery has high capacity performance, and the cost of the positive electrode material is reduced, thereby obtaining high economic value.

[0037] As a preferred embodiment, the average particle size of the composite active material is 5-8 um. The average particle size of the composite active material is generally represented by the size of D50. The average particle size of the composite active material can be 5 um, 6 um, 7 um or 8 um. The average particle size range of the composite active material in this embodiment is advantageous to ensure that the composite active material has good battery performance, avoids that the newly prepared lithium-rich manganese-based material has a poor wrapping effect on the lithium-rich manganese-based recycled material, and that the lithium-rich manganese-based recycled material with poor electrical performance participates in the electrochemical reaction, thereby causing the overall electrical performance of the composite active material to decrease, and avoids that the particle size is too large, causing the positive plate to be too thick, increasing the lithium ion diffusion path, and not conducive to the full play of the characteristics of the composite active material, thereby causing the electrical performance of the material to decrease.

[0038] In a preferred embodiment, the average particle size of the first lithium-rich manganese-based material is 0.4-1.2 um; preferably, the average particle size of the first lithium-rich manganese-based material is 0.8-1.0 um. The average particle size of the first lithium-rich manganese-based material, i.e., the lithium-rich manganese-based recycled material, can be 0.4 um, 0.5 um, 0.6 um, 0.7 um, 0.8 um, 0.9 um, 1.0 um, 1.1 um or 1.2 um. The average particle size of the lithium-rich manganese-based recycled material in the present application is advantageous to ensure that the composite active material has good battery performance, while ensuring that the newly prepared lithium-rich manganese-based material reliably coats the lithium-rich manganese-based recycled material, and reduces the cost of the composite active material. When the average particle size of the first lithium-rich manganese-based material is less than 0.4 um, the newly prepared lithium-rich manganese-based material cannot be reliably prepared, resulting in a decrease in the battery performance of the composite material, and when the average particle size of the first lithium-rich manganese-based material is greater than 1.2 um, the coating effect of the outer layer of the newly prepared lithium-rich manganese-based material is poor, and the large particle size of the first lithium-rich manganese-based material also affects the full play of the performance of the composite active material, thereby causing the battery performance to decrease.

[0039] As a realizable way, the chemical formula of the composite active material is xLi2MnO3(1-x)LiMO2, where M=Ni or Mn, and 0

[0040] In summary, the composite active material of the present application has a lithium-rich manganese-based recycled material as the core and a newly prepared lithium-rich manganese-based material as the shell, realizes waste recycling, and because the core and the shell are the same type of material, they have good compatibility, are easy to prepare, ensure that the battery has high capacity performance, reduce the cost of the positive electrode material, and have high economic value.

[0041] In a second aspect, the present application provides a method for preparing the positive plate of the first aspect, comprising the following steps:

[0042] S1, the scrapped lithium-rich manganese-based positive plate is separated and treated to obtain active material containing lithium-rich manganese-based;

[0043] It can be understood that the scrapped lithium-rich manganese-based positive plate is separated and treated, which can be in the form of liquid immersion, such as immersion in water or immersion in ethanol; of course, a mechanical separation method can also be used, such as directly scraping the active material containing lithium-rich manganese-based from the positive plate, and the embodiments of the present application do not make specific limitations.

[0044] S2, the active material containing lithium-rich manganese-based is ball milled and dried to obtain a first lithium-rich manganese-based material powder;

[0045] The ball milling is in the form of wet ball milling, and ethanol, water or a mixture of ethanol and water can be added; in the actual preparation process, the ball milling ratio is (3-5):2, the rotation speed is 1600r / min-2000r / min, and the time is 15h-20h; the active material containing lithium-rich manganese-based material can be crushed and dispersed by ball milling, and the crushed size is crushed to a suitable particle size, which is convenient for preparing a composite active material;

[0046] The ball-milled material is dried, which can evaporate the solvent or other volatile components therein, further purify the ball-milled material, and facilitate subsequent use. The drying method can be vacuum drying, air drying or spray drying.

[0047] S3, a mixed metal salt solution containing manganese salt and M metal salt, and a precipitant solution and a complexing agent solution are configured;

[0048] The manganese salt and the M metal salt can be at least one of sulfate, nitrate and chloride. For example: manganese sulfate, manganese nitrate, manganese chloride, nickel sulfate, nickel nitrate, nickel chloride, cobalt sulfate, cobalt nitrate and cobalt chloride; the concentration of the mixed metal salt solution can be 1.5mol / L-3mol / L; in the actual configuration process, the amount of the mixed metal salt solution can be calculated according to the stoichiometric ratio required in xLi2MnO3(1-x)LiMO2(0

[0049] The precipitant includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, and the concentration of the precipitant can be 0.7-1.5 mol / L; the complexing agent can be at least one of ammonia, acid solution (hydrofluoric acid, ethylenediaminetetraacetic acid, acetic acid, lactic acid, salicylic acid, tartaric acid, succinic acid or sulfosalicylic acid), salt solution (sodium hydrofluoride, potassium hydrofluoride, ammonium hydrofluoride, disodium ethylenediaminetetraacetate, potassium ethylenediaminetetraacetate or ammonium ethylenediaminetetraacetate), ethylenediamine and 2-methyl-8-hydroxyquinoline, and the concentration of the complexing agent can be 0.1-0.5 mol / L. The embodiments of the present application do not make specific limitations on the above,

[0050] S4, the first lithium-rich manganese-based material powder, the mixed metal salt solution, the precipitant solution and the complexing agent solution are mixed to obtain a mixed solution, the mixed solution is placed in a reaction kettle to carry out a precipitation reaction, and then the composite active material precursor is obtained through solid-liquid separation, washing and drying;

[0051] In the precipitation reaction of the mixed solution of the first lithium-rich manganese-based material powder, the mixed metal salt solution, the precipitant solution and the complexing agent solution, the mixed metal salt solution, the complexing agent and the precipitant are respectively injected into the reaction kettle containing the first lithium-rich manganese-based material powder in a parallel flow manner at a certain flow rate, and stirring is carried out in the reaction kettle, which can help to form a lithium-rich manganese precursor with a regular morphology, so as to improve the electrochemical performance of the lithium-rich manganese-based material. It should be noted that the mixed metal salt solution, the complexing agent and the precipitant can be pumped into the reaction kettle by a pump; the stirring rate can be 1500-3000 r / min.

[0052] The reaction product is subjected to solid-liquid separation, the solid is washed and dried to obtain the composite active material precursor.

[0053] S5, the composite active material precursor is mixed with a carbon source and a lithium source to carry out heat treatment to obtain a composite active material;

[0054] The carbon source can be glucose, sucrose or starch; the lithium source can be at least one of lithium carbonate and lithium hydroxide monohydrate, and the amount of the lithium source can be calculated according to the stoichiometric ratio required in xLi2MnO3(1-x)LiMO2(0x<1); in specific embodiments, the mass ratio of the lithium source to the composite active material precursor can be 0.5-1.5:1; the embodiments of the present application do not make specific limitations on this.

[0055] After sintering is completed, the lithium-rich manganese-based material obtained after sintering can be crushed and sieved to be more convenient for use as a positive electrode material. It should be noted that the average particle size of the sieved lithium-rich manganese-based material is 5 um.

[0056] S6, the composite active material, the positive electrode conductive agent, and the binder are stirred and slurried according to a mass ratio of (85%-95%):(1%-5%):(1%-5%) with the solvent NMP to obtain a positive electrode slurry, which is then coated, dried, rolled, and cut on an aluminum foil to obtain a positive electrode sheet.

[0057] The positive electrode conductive agent can be conductive carbon black, and can also be a carbon nanotube or graphene, etc. The aluminum foil has a thickness of 10-20 um, for example, 10 um, 12 um, 15 um, 17 um, or 20 um, etc.

[0058] In the preparation method, the scrap positive electrode sheet is separated and ball milled to obtain an active material containing a lithium-rich manganese-based material. Compared with the existing sintering purification or strong acid and strong base dissolution recovery method, the operation is simple, the recovery cost is low, and the environment is not polluted. The recovered lithium-rich manganese-based material, the mixed metal salt solution, the precipitant, and the complexing agent are reacted, and then heat treated, which is conducive to the growth of the newly prepared lithium-rich manganese-based material on the surface of the lithium-rich manganese-based material. The operation is simple and reliable, and the electrochemical performance of the material can be ensured.

[0059] As an implementable manner, the process of separating the scrap lithium-rich manganese-based positive electrode sheet to obtain an active material containing a lithium-rich manganese-based material includes:

[0060] The scrap lithium-rich manganese-based positive electrode sheet is soaked in deionized water until the aluminum foil is separated from the active material containing the lithium-rich manganese-based material, and the active material containing the lithium-rich manganese-based material is obtained.

[0061] The operation is simple and harmless.

[0062] As an implementable manner, the process of ball milling the active material containing the lithium-rich manganese-based material and drying to obtain a first lithium-rich manganese-based material powder includes that the drying method is a spray drying method.

[0063] In the embodiment, the spray drying method is conducive to ensuring that the lithium-rich manganese-based material obtained in the drying process does not agglomerate, ensuring good dispersibility of the lithium-rich manganese-based material in the drying process, and forming a nearly spherical particle after drying, which is conducive to subsequent coating of the composite active material.

[0064] Further, in some embodiments, in the process of mixing the first lithium-rich manganese-based material powder, the mixed metal salt solution, the precipitant solution, and the complexing agent solution to obtain a mixed solution, and placing the mixed solution in a reaction kettle to perform a precipitation combination reaction, the pH value of the mixed solution is maintained at 10-12, the temperature of the precipitation combination reaction is 100-120℃, and the time is 5-10h.

[0065] The PH value, reaction temperature and time in the embodiment can make the prepared composite active material precursor form a precursor with regular morphology, thereby facilitating the composite positive electrode material to have better electrochemical performance.

[0066] As an implementable manner, in the process of mixing the composite active material precursor with a carbon source and a lithium source and then performing heat treatment to obtain the composite active material, the temperature of the heat treatment is 700-750°C, and the time is 3-5 h. The temperature and time in the embodiment are advantageous to form the composite positive electrode material with a core-shell structure, so that the newly prepared lithium-rich manganese-based material can be completely coated on the surface of the lithium-rich manganese-based recycled material, thereby ensuring that the composite positive electrode material has good electrochemical performance.

[0067] For example, in specific embodiments, the preparation method of the lithium ion battery is as follows:

[0068] Preparation of the positive electrode sheet:

[0069] S1. A corresponding amount of lithium-rich manganese-based composite positive electrode material, conductive carbon black and polyvinylidene fluoride was weighed according to a mass ratio of 95:2:3 in a stirring tank, and then an appropriate amount of N-methyl pyrrolidone (NMP) was added and stirred for 6 h to obtain a uniform slurry with suitable viscosity;

[0070] S2. The slurry was uniformly coated on an aluminum foil by extrusion coating to form a coating layer, and then the positive electrode sheet was prepared after being fully dried in an oven. The positive electrode sheet was placed in a press for pressing, and then a puncher was used to cut a positive electrode round sheet with a diameter of 15 mm;

[0071] Preparation of the negative electrode sheet:

[0072] S3. A corresponding amount of artificial graphite, conductive carbon black and sodium carboxymethyl cellulose was weighed according to a mass ratio of 95:2.5:2.5 in a stirring tank, and then an appropriate amount of deionized water was added and stirred for 6 h to obtain a uniform slurry with suitable viscosity. The slurry was coated on a copper foil with a thickness of 10 μm, and then the negative electrode sheet was obtained after being dried in a vacuum oven at 150°C for 20 h. The negative electrode sheet was placed in a press for pressing, and then a puncher was used to cut a negative electrode round sheet with a diameter of 18 mm;

[0073] Preparation of the battery

[0074] The positive and negative electrode round sheets were placed in a glove box filled with argon protective atmosphere for battery assembly, in which a solution obtained by dissolving 1 mol / L lithium hexafluorophosphate in a mixed solvent of ethylene carbonate and diethyl carbonate with a molar ratio of 1:1 was used as an electrolyte. The positive electrode round sheet, the negative electrode round sheet, a polyethylene separator and other components were assembled together, and then the electrolyte was injected, and finally the lithium ion battery was prepared.

[0075] Thirdly, embodiments of the present invention provide an electrode assembly including the positive electrode sheet of the first aspect. Thus, this electrode assembly possesses all the features and advantages of the aforementioned positive electrode sheet, which will not be repeated here.

[0076] Fourthly, embodiments of this application provide an energy storage device, including a positive electrode sheet as described in the first aspect or an electrode assembly as described in the third aspect. Therefore, this energy storage device possesses all the features and advantages of the aforementioned positive electrode sheet, which will not be repeated here. In summary, this energy storage device has high capacity performance and safety performance.

[0077] For example, the energy storage device can be a lithium-ion battery, and the negative electrode material of the lithium-ion battery can be any kind of negative electrode material, such as silicon-based negative electrode, lithium metal negative electrode, carbon negative electrode, etc. The embodiments of this application do not limit this.

[0078] Fifthly, embodiments of this application provide an electrical device that includes the energy storage device described in the fourth aspect, the energy storage device supplying power to the electrical device. For example, the aforementioned electrical device may include multiple battery packs composed of the lithium-ion batteries described above. This electrical device may be a lighting fixture, etc. Therefore, it is clear that this electrical device possesses all the features and advantages of the aforementioned positive electrode plate, which will not be repeated here.

[0079] The present invention will be described below through specific embodiments. It should be noted that the specific embodiments below are for illustrative purposes only and do not limit the scope of the present invention in any way. In addition, unless otherwise specified, methods that do not specifically describe the conditions or steps are conventional methods, and the reagents and materials used can be obtained commercially.

[0080] Example 1:

[0081] (1) Preparation of the positive electrode:

[0082] The discarded lithium-rich manganese-based positive electrode sheet is immersed in deionized water to separate the active material containing lithium-rich manganese from the aluminum foil, thus obtaining the active material containing lithium-rich manganese.

[0083] The active material containing lithium-rich manganese was ball-milled and then spray-dried to obtain a first lithium-rich manganese-based material powder, such as... Figure 1 As shown, the Dv50 of the first lithium-rich manganese-based material powder is 0.4 μm; the ball-to-material ratio is 5:2, the rotation speed is 1600 r / min, and the time is 20 h. The lower the ball-to-material ratio, the higher the rotation speed, and the longer the time, the smaller the particle size obtained by ball milling; the pump speed of spray drying is 15 mL / min, and the set temperature is 200 °C.

[0084] A mixed metal salt solution containing manganese salt and M metal salt is prepared according to the stoichiometric ratio required in xLi2MnO3(1-x)LiMO2(0 < x < 1), a 0.7 mol / L sodium hydroxide solution is prepared, and a 0.1 mol / L ammonia water solution is prepared; wherein the concentration of the mixed metal salt solution is 1.5 mol / L;

[0085] The first lithium-rich manganese-based material powder, the mixed metal salt solution, the precipitant solution and the complexing agent solution are mixed to obtain a mixed solution, the mixed solution is placed in a reaction kettle for stirring to perform a precipitation reaction, and then solid-liquid separation, washing and drying are performed to obtain a composite active material precursor; wherein the stirring rate is 1500 r / min, the pH value of the mixed solution is 10-12, the reaction temperature is 100°C, and the reaction time is 5h;

[0086] The composite active material precursor is mixed with glucose and lithium carbonate according to a mass ratio of 80:15:5 to perform heat treatment to obtain a composite active material; wherein the heat treatment temperature is 700°C, and the time is 3h.

[0087] The obtained composite active material is ground and then subjected to particle size distribution test, and the results are shown in Figure 1 , the particle size Dv50 is about 5um-8um; the electron microscope photo is shown in Figure 2 , the composite positive electrode material has a core-shell structure; Figure 3 The XRD results are shown, and the composite positive electrode material mainly has the main crystal phase of the lithium-rich manganese-based material, and the intensity ratio of the main crystal faces I003 / I104 is about 1.530-1.535.

[0088] It should be noted that:

[0089] Dv50 test: a laser diffraction particle size distribution measuring instrument (Malvern Mastersizer3000) is used, and the particle size distribution is measured according to the particle size distribution laser diffraction method GB / T19077-2016 to obtain Dv50;

[0090] XRD measurement: an X-ray diffractometer (D500Siemens) is used for testing using a copper target (λ = 0.154 nm), the scanning speed is 3° / min, the scanning angle is 10-90°, and the radiation source is a CuKα radiation source;

[0091] The composite active material, conductive carbon black and polyvinylidene fluoride are stirred and slurried with a solvent NMP according to a mass ratio of 95%:2%:3% to obtain a positive electrode slurry, and then the positive electrode slurry is coated on a 15um thick aluminum foil, and dried in a vacuum oven at 150°C, rolled, cut and made into a positive electrode sheet;

[0092] (2) Preparation of a negative electrode sheet:

[0093] The artificial graphite, conductive carbon black and sodium carboxymethyl cellulose are stirred according to a mass ratio of 95%:2.5%:2.5% to obtain a negative electrode slurry, and then the slurry is coated on a 10um thick copper foil and dried, rolled, cut, and a negative electrode sheet is prepared;

[0094] (3) Preparation of lithium ion battery:

[0095] The positive electrode sheet and the negative electrode sheet are placed in a glove box filled with argon protective atmosphere for battery assembly, wherein a solution obtained by dissolving 1 mol / L lithium hexafluorophosphate in a mixed solvent of ethylene carbonate and diethyl carbonate in a molar ratio of 1:1 is used as an electrolyte; the positive electrode sheet, the negative electrode sheet, the polyethylene separator and other components are assembled together, then the electrolyte is injected, and finally a button lithium ion battery is prepared.

[0096] Example 2

[0097] Different from the above-mentioned example 1, the ball-to-material ratio is 5:2, the rotating speed is 1700r / min, and the time is 20h, and the Dv50 of the first lithium-rich manganese-based material powder in this example is 0.6um;

[0098] Example 3

[0099] Different from the above-mentioned example 1, the ball-to-material ratio is 5:2, the rotating speed is 1800r / min, and the time is 20h, and the Dv50 of the first lithium-rich manganese-based material powder in this example is 0.8um;

[0100] Example 4

[0101] Different from the above-mentioned example 1, the ball-to-material ratio is 5:2, the rotating speed is 1900r / min, and the time is 20h, and the Dv50 of the first lithium-rich manganese-based material powder in this example is 1.0um;

[0102] Example 5

[0103] Different from the above-mentioned example 1, the ball-to-material ratio is 5:2, the rotating speed is 2000r / min, and the time is 20h, and the Dv50 of the first lithium-rich manganese-based material powder in this example is 1.2um;

[0104] Example 6

[0105] Different from the above-mentioned example 1, the heat treatment temperature is 500℃, and the time is 3h, and the Dv50 of the composite positive electrode active material in this example is 1um;

[0106] Example 7

[0107] Different from the above-mentioned example 1, the heat treatment temperature is 900℃, and the time is 3h, and the Dv50 of the composite positive electrode active material in this example is 15um;

[0108] Comparative Example 1

[0109] Different from Example 1, in the present comparative example, the first lithium-rich manganese-based material is directly used as the positive active material, and the Dv50 of the first lithium-rich manganese-based material powder is 5-8 um;

[0110] The performance test process of the lithium ion battery and the test results are described as follows:

[0111] (1) Rate discharge capacity

[0112] At 25°C, the lithium battery prepared in the example and the comparative example is charged to 4.5V at a rate of 0.5C, and then discharged to 3V at a rate of 0.5C. The capacity at this time is recorded as the 0.5C discharge capacity. Then, the lithium battery is charged to 4.5V at a rate of 1C, and then discharged to 3V at a rate of 1C. The capacity at this time is recorded as the 1C discharge capacity.

[0113] (2) Cycle performance test

[0114] At 25°C, the lithium battery prepared in the example and the comparative example is charged to 4.5V at a rate of 1C, and then discharged to 3V at a rate of 1C. The capacity of the first cycle is taken as the initial capacity, and the capacity of the 200th cycle is divided by the initial capacity to obtain the retention rate value.

[0115] The results of the lithium ion batteries of Examples 1-7 and Comparative Example 1 tested according to the above process and method are shown in Table 1:

[0116] Table 1 Test results of Examples 1-7 and Comparative Example 1

[0117]

[0118]

[0119] According to the results shown in Table 2:

[0120] Compared with Comparative Example 1, the rate performance and cycle performance of the lithium ion batteries of Examples 1-7 are obviously superior to those of the lithium ion battery of Comparative Example 1. This indicates that the composite positive electrode material of the present application, which is prepared by coating the lithium-rich manganese-based recycled material with the newly prepared lithium-rich manganese-based material, can effectively improve the rate performance and cycle performance of the lithium ion battery.

[0121] According to the test results of the lithium ion batteries of embodiments 1-5, it can be seen that the composite cathode material takes the lithium-rich manganese-based recycled material as the core, and when the particle size of the lithium-rich manganese-based recycled material powder gradually increases, the performance of the lithium ion battery first increases and then decreases, which indicates that the particle size range of the lithium-rich manganese-based recycled material disclosed in the application is beneficial to ensuring that the battery has excellent rate performance and cycle performance. When the particle size of the lithium-rich manganese-based recycled material is too large, the coating effect of the outer normal lithium-rich manganese-based material is poor, and the particle size that is too large will also affect the full play of the material properties.

[0122] According to the test results of the lithium ion batteries of embodiments 1, 6 and 7, it can be seen that the rate performance and cycle performance of embodiments 6 and 7 are lower than that of embodiment 1, which indicates that the particle size of the composite cathode material is too large or too small, which will cause the rate performance and cycle performance of the lithium ion battery to decrease. The particle size range of the composite cathode material of the application is beneficial to improving the rate performance and cycle performance of the battery.

[0123] The above description is only the preferred embodiments of the application and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the application involved in the application is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or equivalent features without departing from the inventive concept. For example, the above features can be replaced with the technical features disclosed in the application (but not limited to) having similar functions to form technical solutions.

Claims

1. A positive electrode sheet characterized by comprising: The composite active material comprises a current collector and a composite active material coated on the surface of the current collector, the composite active material comprises an inner core and a shell layer coated on the surface of the inner core, the inner core comprises a first lithium-rich manganese-based material, and the shell layer comprises a second lithium-rich manganese-based material, the first lithium-rich manganese-based material is mainly used to support the outer layer of the second lithium-rich manganese-based material; wherein the first lithium-rich manganese-based material is a lithium-rich manganese-based recycled material obtained through a recycling process, and the second lithium-rich manganese-based material is a newly prepared lithium-rich manganese-based material; the average particle size of the inner core is 0.08-0.5 times the average particle size of the composite active material. The average particle size of the composite active material is 5-8 um. The average particle size of the first lithium-rich manganese-based material is 0.4-1.2 um.

2. The positive electrode sheet according to claim 1, characterized by The average particle size of the first lithium-rich manganese-based material is 0.8-1.0 um.

3. The positive electrode sheet according to claim 1, characterized by The chemical formula of the active material is xLi2MnO3(1-x)LiMO2, wherein M=Ni or Mn, and 0 4. A method for producing the positive electrode sheet according to any one of claims 1 to 3, characterized by, The method comprises the following steps: The scrap lithium-rich manganese-based positive electrode sheet is subjected to separation treatment to obtain an active material containing a lithium-rich manganese-based material; The active material containing the lithium-rich manganese-based material is subjected to ball milling treatment and drying to obtain the first lithium-rich manganese-based material powder; A mixed metal salt solution containing a manganese salt and an M metal salt, a precipitant solution, and a complexing agent solution are prepared; The first lithium-rich manganese-based material powder, the mixed metal salt solution, the precipitant solution, and the complexing agent solution are mixed to obtain a mixed solution, the mixed solution is placed in a reaction kettle to perform a precipitation combination reaction, and then solid-liquid separation, washing, and drying are performed to obtain a composite active material precursor; The composite active material precursor is mixed with a carbon source and a lithium source to perform heat treatment to obtain the composite active material; The composite active material, a positive electrode conductive agent, and a binder are stirred and slurried with a solvent NMP at a mass ratio of (85%-95%):(1%-5%):(1%-5%) to obtain a positive electrode slurry, which is then coated, dried, rolled, and cut on an aluminum foil to obtain the positive electrode sheet.

5. The method of claim 4, wherein, The process of separating the scrap lithium-rich manganese-based positive electrode sheet to obtain the active material containing the lithium-rich manganese-based material comprises: The scrap lithium-rich manganese-based positive electrode sheet is soaked in deionized water until the aluminum foil is separated from the active material containing the lithium-rich manganese-based material to obtain the active material containing the lithium-rich manganese-based material.

6. The method of claim 4, wherein, In the process of ball milling and drying the active material containing the lithium-rich manganese-based material to obtain the first lithium-rich manganese-based material powder, a spray drying method is used for drying.

7. The method of claim 4, wherein, In the process of mixing the first lithium-rich manganese-based material powder, the mixed metal salt solution, the precipitant solution, and the complexing agent solution to obtain a mixed solution, and placing the mixed solution in a reaction kettle to perform a precipitation combination reaction, the pH value of the mixed solution is maintained at 10-12, and the precipitation combination reaction is performed at a temperature of 100-120°C for 5-10 hours.

8. The method of claim 4, wherein, In the process of mixing the composite active material precursor with a carbon source and a lithium source and heat treating to obtain the composite active material, the temperature of the heat treatment is 700-750 DEG C, and the time is 3-5 hours.

9. An electrode assembly characterized by, The positive electrode plate according to any one of claims 1-3.

10. An energy storage device, characterized by, The electrode assembly according to claim 9, comprising the positive electrode plate according to any one of claims 1-3.

11. An electrical device, characterized by The electric device comprises the energy storage device according to claim 10, and the energy storage device supplies power to the electric device.

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