Positive pole piece, battery, energy storage device and electric equipment

Abstract

The invention provides a positive pole piece, a battery, an energy storage device and electric equipment, the positive pole piece comprises a positive current collector, the surface, deviating from a winding center, of the positive current collector is provided with a first positive material layer, and the surface, facing the winding center, of the positive current collector is provided with a second positive material layer; the average non-sphericity degree of particles of the positive electrode material with the particle size larger than or equal to 1 micron is k1, Dv50 is D1, k1 is larger than or equal to 10% and smaller than or equal to 19%, and D1 is larger than or equal to 0.8 micron and smaller than or equal to 1.2 microns; in the second positive electrode material layer, the average non-sphericity degree of positive electrode material particles with the particle size larger than or equal to 1 [mu] m is k2, Dv50 is D2, k2 is larger than or equal to 21% and smaller than or equal to 35%, and D2 is larger than or equal to 1.2 [mu] m and smaller than or equal to 1.7 [mu] m.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a positive electrode sheet, a battery, an energy storage device and an electrical equipment. Background Art

[0002] Secondary batteries (such as lithium-ion batteries) have the characteristics of high specific energy, high operating voltage, low self-discharge rate, small size and light weight. They are widely used in various fields such as energy storage, portable electronic devices and electric vehicles.

[0003] Lithium-ion batteries based on lithium iron phosphate positive electrode materials have the advantages of high safety and stability. With the increasing demand for battery capacity in energy storage scenarios, lithium iron phosphate materials with smaller particle sizes are often used. However, this leads to the problem that the elongation of the positive electrode sheet increases during the rolling process. In addition, if the capacity of the secondary battery is increased by simply increasing the amount of positive electrode material coating, lithium deposition is prone to occur at the negative electrode interface facing the inner side of the positive electrode sheet during the charging and discharging process, affecting the capacity of the secondary battery. How to reduce the risk of lithium deposition at the negative electrode interface facing the inner side of the positive electrode sheet while reducing the elongation of the positive electrode sheet has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the above technical problems, the present application discloses a positive electrode sheet, a battery, an energy storage device and an electrical equipment, which reduce the elongation rate of the positive electrode sheet while reducing the risk of lithium plating at the negative electrode interface facing the inner side of the positive electrode sheet.

[0005] In a first aspect, the present application provides a positive electrode sheet for use in a battery with a winding structure, wherein the positive electrode sheet includes a positive electrode current collector, a surface of the positive electrode current collector away from the winding center is provided with a first positive electrode material layer, and a surface of the positive electrode current collector toward the winding center is provided with a second positive electrode material layer, wherein in the first positive electrode material layer, the average non-sphericity of the particles of the positive electrode material with a particle size greater than or equal to 1 μm is k 1 , and Dv50 is D 1 , 10% ≤ k 1 ≤19%, 0.8μm≤D 1 ≤1.2μm; in the second positive electrode material layer, the average non-sphericity of the positive electrode material particles with a particle size greater than or equal to 1μm is k 2 , and Dv50 is D 2 , 21% ≤ k 2 ≤35%, 1.2μm≤D 2 ≤1.7μm.

[0006] In some embodiments of the present application, 12%≤k 1 ≤17%, 0.9μm≤D 1 ≤1.1μm.

[0007] In some embodiments of the present application, 26%≤k 2 ≤33%, 1.4μm≤D 2 ≤1.6μm.

[0008] In some embodiments of the present application, the compaction density of the first positive electrode material layer and / or the second positive electrode material layer is 2.4 g / cm 3 ~2.6g / cm 3 .

[0009] In some embodiments of the present application, the elongation of the positive electrode plate is 1.3% to 2.5%, and the 0.5C discharge specific capacity is 141 mAh / g to 147 mAh / g.

[0010] In some embodiments of the present application, the elongation of the positive electrode plate is 1.3% to 2.0%, and the 0.5C discharge specific capacity is 143 mAh / g to 147 mAh / g.

[0011] In some embodiments of the present application, the first positive electrode material layer has a first positive electrode material, the second positive electrode material layer has a second positive electrode material, and the first positive electrode material and / or the second positive electrode material have a chemical formula of LiFe x Ti y PO 4 / C, x+y=1, and y≤0.05.

[0012] In a second aspect, the present application provides a battery, comprising the positive electrode plate described in the first aspect.

[0013] In a third aspect, the present application provides an energy storage device, comprising a housing and at least one battery as described in the second aspect, wherein the battery is accommodated in the housing.

[0014] In a fourth aspect, the present application provides an electrical device, comprising the energy storage device described in the third aspect, wherein the energy storage device supplies power to the electrical device.

[0015] Compared with the prior art, this application has at least the following beneficial effects:

[0016] The present application provides a positive electrode sheet, a battery, an energy storage device and an electric device. The positive electrode sheet is applied to a battery with a winding structure. The positive electrode sheet includes a positive electrode collector. A first positive electrode material layer is arranged on the surface of the positive electrode collector away from the winding center. A second positive electrode material layer is arranged on the surface of the positive electrode collector toward the winding center. In the first positive electrode material layer, the average non-sphericity of the particles of the positive electrode material with a particle size greater than or equal to 1 μm is k 1 , and Dv50 is D 1 , 10% ≤ k 1≤19%, 0.8μm≤D 1 ≤1.2μm; in the second positive electrode material layer, the average non-sphericity of the positive electrode material particles with a particle size greater than or equal to 1μm is k 2 , and Dv50 is D 2 , 21% ≤ k 2 ≤35%, 1.2μm≤D 2 ≤1.7μm. This application is achieved by regulating k 1 , D 1 , k 2 , D 2 Within the above range, the second positive electrode material in the second positive electrode material layer toward the winding center has a larger particle size and non-sphericity. When the positive electrode sheet is rolled, the second positive electrode material can be used to hinder the displacement and deformation of the positive electrode material particles, thereby reducing the risk of wrinkles and tearing of the positive electrode current collector. At the same time, the second positive electrode material has a relatively moderate Li + Migration path, capacity performance is not easy to be over-exerted, which is conducive to slowing down the lithium deposition phenomenon at the negative electrode interface facing the inner side of the positive electrode sheet; and the first positive electrode material in the first positive electrode material layer away from the winding center has a smaller particle size and non-sphericity, which is conducive to the performance of the positive electrode sheet capacity. In summary, the present application can reduce the risk of lithium deposition at the negative electrode interface facing the inner side of the positive electrode sheet while reducing the elongation rate of the positive electrode sheet, thereby improving the capacity performance of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram of the structure of a positive electrode sheet according to an embodiment of the present application;

[0019] Figure 2 A schematic diagram of the structure of a lithium-ion battery according to an embodiment of the present application;

[0020] Figure 3 In one embodiment of the present application Figure 2 An enlarged schematic diagram of the structure of part A shown;

[0021] Figure 4 A schematic diagram of the structure of a household energy storage system according to an implementation scheme of the present application;

[0022] Figure 5 A schematic diagram of the structure of an energy storage system according to an implementation scheme of the present application;

[0023] Figure 6 Schematic diagram of calculating particle non-sphericity for this application;

[0024] Figure 7 A schematic diagram of the elongation test of the positive electrode sheet of this application;

[0025] Figure 8 This is a photograph of the first negative electrode material layer of the negative electrode plate disassembled after the battery of Comparative Example 1 is fully charged;

[0026] Fig. 9 This is a photo of the first negative electrode material layer of the negative electrode plate disassembled after the battery of Example 1 is fully charged;

[0027] Fig.10 This is a scanning electron microscope (SEM) image of the first positive electrode material prepared in Example 1 of the present application;

[0028] Fig.11 This is a SEM image of the second positive electrode material prepared in Example 1 of the present application.

[0029] Explanation of the accompanying drawings: 1-energy storage device, 2-electric energy conversion device, 3-first user load, 4-second user load, 10-positive electrode plate, 11-positive electrode current collector, 12-first positive electrode material layer, 13-second positive electrode material layer, 20-diaphragm, 30-negative electrode plate, 31-negative electrode current collector, 32-first negative electrode material layer, 33-second negative electrode material layer, 40-roller, 400-energy storage system, 410-high voltage cable, 420-first electric energy conversion device, 430-second electric energy conversion device. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0032] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0033] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0035] It should be noted that, in the present application, a lithium-ion battery is used as an example of a secondary battery to explain the present application, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0036] At present, one of the methods to improve the capacity of lithium-ion batteries based on lithium iron phosphate materials is to reduce the particle size range of the particles, make the surface morphology smooth and spherical, so as to shorten the Li + Migration paths, reduce interface side reactions, and improve material kinetics to achieve high capacity of positive electrode materials. However, this characteristic easily causes particle deformation and displacement, resulting in excessive elongation of the positive electrode sheet, causing problems such as wrinkles and edge cracking of the positive electrode sheet. In order to further improve the capacity performance of lithium-ion batteries, the positive electrode sheet also needs to be coated with more lithium iron phosphate material, but during the battery charging and discharging process, lithium precipitation is prone to occur at the negative electrode interface facing the inner side of the positive electrode sheet, which is not conducive to the performance of the capacity performance of lithium-ion batteries.

[0037] In view of this, the present application provides a positive electrode sheet, which is applied to a lithium-ion battery with a winding structure. Figure 1 The positive electrode sheet 10 includes a positive electrode current collector 11, a first positive electrode material layer 12 is disposed on the surface of the positive electrode current collector 11 away from the winding center, and a second positive electrode material layer 13 is disposed on the surface of the positive electrode current collector 11 toward the winding center, wherein the average non-sphericity of the particles of the positive electrode material with a particle size greater than or equal to 1 μm in the first positive electrode material layer 12 is k 1 , and Dv50 is D1 , 10% ≤ k 1 ≤19%, 0.8μm≤D 1 ≤1.2μm, preferably, 12%≤k 1 ≤17%, 0.9μm≤D 1 ≤1.1μm, for example, k 1 = 10%, 12%, 15%, 17% or 19%, D 1 =0.8μm, 0.9μm, 1.1μm or 1.2μm; in the second positive electrode material layer 13, the average non-sphericity of the positive electrode material particles with a particle size greater than or equal to 1μm is k 2 , and Dv50 is D 2 , 21% ≤ k 2 ≤35%, 1.2μm≤D 2 ≤1.7μm, preferably, 26%≤k 2 ≤33%, 1.4μm≤D 2 ≤1.6μm, for example, k 2 =21%, 25%, 30%, 32% or 35%, D 2 =1.2μm, 1.4μm, 1.5μm or 1.7μm. In the present application, k of the first positive electrode material layer is adjusted 1 , D 1 and k of the second positive electrode material layer 2 , D 2 Within the above range, the second positive electrode material in the second positive electrode material layer toward the winding center has a larger particle size and non-sphericity. When the positive electrode sheet is rolled, the second positive electrode material can be used to hinder the displacement and deformation of the positive electrode material particles, thereby reducing the risk of wrinkles and tearing of the positive electrode current collector. At the same time, the second positive electrode material has a relatively moderate Li + Migration path, capacity performance is not easy to be over-exerted, which is conducive to slowing down the lithium deposition phenomenon at the negative electrode interface facing the inner side of the positive electrode sheet; and the first positive electrode material in the first positive electrode material layer away from the winding center has a smaller particle size and non-sphericity, which is conducive to the performance of the positive electrode sheet capacity. Under the joint action of the first positive electrode material layer and the second positive electrode material layer, the present application can reduce the risk of lithium deposition at the negative electrode interface facing the inner side of the positive electrode sheet while reducing the elongation rate of the positive electrode sheet, thereby improving the capacity performance of the lithium-ion battery.

[0038] In the present application, Dv50 means a particle size at which the volume accumulation is 50% from the smaller particle size side in a volume-based particle size distribution of particles.

[0039] In an optional embodiment, the compaction density of the first positive electrode material layer and / or the second positive electrode material layer is 2.4 g / cm 3 ~2.6g / cm 3For example, the compaction density of the first positive electrode material layer and / or the second positive electrode material layer is 2.4 g / cm 3 , 2.5g / cm 3 or 2.6 g / cm 3 By adjusting the compaction density of the first positive electrode material layer and / or the second positive electrode material layer within the above range, it is beneficial to reduce the risk of cracking of the positive electrode sheet after rolling and to increase the capacity of the lithium-ion battery.

[0040] In an optional embodiment, the elongation of the positive electrode sheet is 1.3% to 2.5%, preferably 1.3% to 2.0%, and the 0.5C discharge specific capacity is 141mAh / g to 147mAh / g, preferably 143mAh / g to 147mAh / g. For example, the elongation of the positive electrode sheet is 1.3%, 1.5%, 1.7% or 2.5%; the 0.5C discharge specific capacity is 141mAh / g, 143mAh / g, 145mAh / g or 147mAh / g. The positive electrode sheet with the above elongation and discharge specific capacity makes the positive current collector less prone to wrinkles and the capacity of the positive electrode sheet is better.

[0041] In an optional embodiment, the first positive electrode material layer has a first positive electrode material, the second positive electrode material layer has a second positive electrode material, and the first positive electrode material and / or the second positive electrode material has a chemical formula of LiFe x Ti y PO 4 / C, x+y=1, and y≤0.05. For example, y=0.01, 0.02, 0.03, 0.04 or 0.05, wherein the titanium element is beneficial to the performance of the positive electrode material layer capacity, and is beneficial to the improvement of the capacity performance of the lithium ion battery.

[0042] The present application has no particular restrictions on the preparation methods of the first positive electrode material and the second positive electrode material, as long as the purpose of the present application can be achieved. Exemplarily, the preparation method of the first positive electrode material includes the following steps:

[0043] Step a: According to LiFe x Ti y PO 4 Weigh the iron source, phosphorus source, carbon source, lithium source and titanium source in the required stoichiometric ratio of / C (x+y=1, and y≤0.05), mix them evenly on a ball mill, add pure water as a dispersant, and then perform high-energy ball milling;

[0044] Step b, spray drying the material after high-energy ball milling to form a first powder;

[0045] Step c: placing the first powder into a vacuum atmosphere sintering furnace for a first sintering treatment, and then crushing the first powder to obtain a first positive electrode material.

[0046] In step a, the iron source can be selected from ferrous oxalate, ferric phosphate or ferric oxide, the phosphorus source can be selected from lithium dihydrogen phosphate or ammonium dihydrogen phosphate, the lithium source can be selected from lithium carbonate or lithium hydroxide, the carbon source can be selected from glucose, sucrose or citric acid, and the titanium source can be selected from titanium dioxide. The ball-to-material ratio of high-energy ball milling is 3 to 5:1, the rotation speed is 1000 r / min to 1500 r / min, and the ball milling time is 15 h to 20 h.

[0047] In step b, the pump speed of spray drying is 8 mL / min to 12 mL / min, the drying temperature is 180° C. to 220° C., and the formed powder is granular.

[0048] In step c, the atmosphere of the first sintering treatment is nitrogen, the sintering temperature is 600° C. to 750° C., preferably 680° C. to 700° C., and the sintering time is 5 h to 10 h.

[0049] The present invention regulates the average non-sphericity k of the first positive electrode material particles. 1 There is no particular limitation on the method, for example, the average non-sphericity k of the first positive electrode material particles is 1 Generally, k increases with the increase of sintering temperature during the sintering process. Based on this, the present application can adjust k by adjusting the temperature of the first sintering process. 1 .

[0050] Exemplarily, the preparation method of the second positive electrode material comprises the following steps:

[0051] Step A: According to LiFe x Ti y PO 4 / C (x+y=1, and y≤0.05) in the required stoichiometric ratio, weighing an iron source, a phosphorus source, a first carbon source, a lithium source and a titanium source and mixing them to obtain a mixed metal salt solution; then preparing a strong alkaline solution as a precipitant solution, and preparing ammonia water as a complexing agent solution;

[0052] Step B, placing the mixed metal salt solution, complexing agent solution and precipitant solution prepared above in a reaction kettle, stirring continuously, maintaining the pH value of the reaction liquid at 9±0.5, the reaction temperature at 190°C to 200°C, the reaction time at 8h to 10h, synthesizing by precipitation reaction, and obtaining a first precursor material after solid-liquid separation, washing and drying;

[0053] Step C, mixing the prepared first precursor material with the second carbon source, adding deionized water as a dispersant, performing ball milling, and then spray drying to form a second powder;

[0054] Step D: performing a second sintering treatment on the second powder at a sintering temperature of 600° C. to 750° C., preferably 680° C. to 700° C., for a sintering time of 5 h to 10 h, and then performing a crushing treatment to obtain a second positive electrode material.

[0055] In step A, the iron source can be selected from ferrous oxalate, ferrous sulfate or ferric chloride, the phosphorus source can be selected from phosphoric acid or diammonium phosphate, the first carbon source can be selected from glucose, sucrose or citric acid, the lithium source can be selected from lithium carbonate or lithium hydroxide, and the titanium source is selected from titanium dioxide; the above raw materials can be first prepared into corresponding solutions, and then the solutions containing the above raw materials are mixed to obtain a mixed metal salt solution, wherein the molar concentration of titanium in the mixed metal salt solution is 3mol / L to 5mol / L; the strong alkaline solution can be a sodium hydroxide solution with a molar concentration of 0.5mol / L to 1mol / L, and the molar concentration of ammonia water is 0.5mol / L to 1.5mol / L. The solvent in the mixed metal salt solution in the present application can include water and / or phosphoric acid.

[0056] In step B, a complexing agent may be first added to the mixed metal salt solution to adjust the pH value to 9±0.5, and then a precipitant solution may be added. As the precipitate is generated, the complexing agent may be continuously added to adjust the pH value to maintain at 9±0.5. This process is a precipitation reaction process.

[0057] In step C, the first precursor material and the second carbon source can be mixed in a mass ratio of (92-97):(93-8); the second carbon source can be selected from glucose; the ball-to-material ratio of high-energy ball milling is 3-5:1, the rotation speed is 1000r / min-1500r / min, and the ball milling time is 10h-15h; the pump speed of spray drying is 8mL / min-12mL / min, the drying temperature is 180℃-220℃, and the powder formed is granular.

[0058] The present invention regulates the average non-sphericity k of the second positive electrode material particles. 2 There is no particular limitation on the method, for example, the average non-sphericity k of the second positive electrode material particles is 2 Generally, k increases with the increase of sintering temperature during the sintering process. Based on this, the present application can adjust k by adjusting the temperature of the second sintering treatment. 2 .

[0059] The present application also provides a battery, comprising the positive electrode sheet described in any of the above embodiments, such as Figure 2 As shown, the battery is a lithium-ion battery with a winding structure, and the battery includes a positive electrode sheet 10, a separator 20 and a negative electrode sheet 30, wherein point O is the winding center; Figure 3 In one embodiment Figure 2 The enlarged schematic diagram of the structure of part A shown in FIG. Figure 3A first positive electrode material layer 12 is provided on the surface of the positive electrode collector 11 facing away from the winding center point O, and a second positive electrode material layer 13 is provided on the surface of the positive electrode collector 11 facing the winding center point O; the negative electrode sheet 30 includes a negative electrode collector 31, a first negative electrode material layer 32 and a second negative electrode material layer 33, wherein the first negative electrode material layer 32 is the negative electrode interface facing the inner side of the positive electrode sheet.

[0060] In the present application, the positive electrode material layer is arranged on the surface of the positive electrode current collector, that is, the positive electrode material layer can be arranged in a partial area of ​​one surface of the positive electrode current collector, or in the entire area of ​​one surface of the positive electrode current collector. In the present application, there is no special restriction on the positive electrode current collector, as long as the purpose of the present application can be achieved, for example, it can include but is not limited to aluminum foil, aluminum alloy foil or composite current collector, etc. In the present application, there is no special restriction on the thickness of the positive electrode current collector, as long as the purpose of the present application can be achieved, for example, the thickness is 4μm to 12μm. The single-sided thickness of the positive electrode material layer of the present application can be 8μm to 15μm.

[0061] The lithium-ion battery of the present application also includes a negative electrode plate. The present application has no special restrictions on the negative electrode plate, as long as the purpose of the present application can be achieved. For example, the negative electrode plate generally includes a negative electrode current collector and a negative electrode material layer. In the present application, the negative electrode material layer is arranged on the surface of the negative electrode current collector, that is, the negative electrode material layer can be arranged in a partial area of ​​one surface of the negative electrode current collector, or in the entire area of ​​one surface of the negative electrode current collector. The present application has no special restrictions on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it can include but is not limited to copper foil, copper alloy foil, nickel foil or composite current collector. In the present application, there is no special restriction on the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved, for example, the thickness is 4μm to 12μm. The single-sided thickness of the negative electrode material layer of the present application can be 70μm to 200μm.

[0062] In the present application, the negative electrode material layer includes a negative electrode material, wherein the negative electrode material is not particularly limited as long as the purpose of the present application can be achieved. For example, it may include at least one of artificial graphite, natural graphite, mesophase carbon microbeads, soft carbon, hard carbon, silicon, and silicon carbon.

[0063] In the present application, the negative electrode material layer may further include a negative electrode binder. The present application has no particular restrictions on the negative electrode binder, as long as it can achieve the purpose of the present application, for example, it may include but is not limited to at least one of acrylate, polyamide, polyimide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, and potassium carboxymethyl cellulose.

[0064] The lithium-ion battery of the present application also includes a diaphragm. The present application has no particular restrictions on the diaphragm, and those skilled in the art can select it according to actual needs, as long as the purpose of the present application can be achieved. For example, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0065] The battery of the present application also includes an electrolyte. The present application has no particular restrictions on the electrolyte, and those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. For example, at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), propyl propionate (PP), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC) or fluoroethylene carbonate (FEC) is mixed in a certain mass ratio or volume ratio to obtain a non-aqueous organic solvent, and then a lithium salt is added to dissolve and mix evenly. The present application has no restrictions on the type of lithium salt, as long as the purpose of the present application can be achieved. For example, the lithium salt may include LiPF 6 , LiBF 4 、LiAsF 6 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 、LiSiF 6 At least one of lithium bis(oxalato)borate (LiBOB) or lithium difluoroborate. The present application has no particular limitation on the concentration of the lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. For example, the concentration of the lithium salt is 1.0 mol / L to 2.0 mol / L.

[0066] The battery of the present application also includes a shell, and the present application has no particular limitation on the shell, and those skilled in the art can select it according to actual needs, as long as the purpose of the present application can be achieved. For example, the shell may include an aluminum-plastic film.

[0067] The present application does not particularly limit the preparation method of the battery, and a preparation method known in the art can be selected as long as the purpose of the present application can be achieved. For example, the preparation method of the battery includes but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain a bare cell with a wound structure, placing the bare cell in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a battery.

[0068] The present application also provides an energy storage device, including a housing and at least one battery in any of the above embodiments, wherein the battery is contained in the housing. The energy storage device having the battery has excellent performance, which is beneficial to the use of the energy storage device. By containing the battery in the housing, the fixation and protection of the battery can be increased, thereby improving the service life of the energy storage device. It is understandable that the energy storage device may have one or more batteries, and when the energy storage device contains multiple batteries, the multiple batteries may be connected in at least one of parallel and series connection.

[0069] The present application also provides an electrical device, including the energy storage device in the above-mentioned implementation scheme, which is conducive to improving the product competitiveness and performance of the electrical device. In an optional implementation scheme, the electrical device includes an electrical device body, and the energy storage device is used to supply power to the electrical device body. In an optional implementation scheme, the electrical device body includes a positive electrode of the device and a negative electrode of the device, the positive electrode plate of the battery in the energy storage device is used to electrically connect to the positive electrode of the device body of the electrical device, and the negative electrode plate of the battery in the energy storage device is used to electrically connect to the negative electrode of the device body of the electrical device, so as to supply power to the electrical device.

[0070] The electrical equipment of the present application may include but is not limited to: containers, household energy storage systems, battery vehicles, electric vehicles, ships, spacecraft, electric toys and electric tools, etc., wherein spacecrafts include airplanes, rockets, space shuttles and spacecrafts, etc., electric toys include fixed or mobile electric toys, such as electric car toys, electric ship toys and electric airplane toys, etc., and electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.

[0071] See also Figure 4 , Figure 4 This is a schematic diagram of the structure of a household energy storage system according to an implementation scheme of the present application, and the present application Figure 4 The implementation plan is described using a household energy storage scenario in user-side energy storage as an example, but the energy storage device of the present application is not limited to the household energy storage scenario.

[0072] The present application provides a household energy storage system, which includes an energy conversion device 2 (photovoltaic panel), a first user load 3 (street lamp), a second user load 4 (such as air conditioner and other household appliances), and an energy storage device 1. The energy storage device 1 is a small energy storage box that can be mounted on an outdoor wall by wall hanging. Specifically, the photovoltaic panel can convert solar energy into electrical energy during the period of low electricity prices. The energy storage device 1 is used to store the electrical energy and supply it to street lamps and household appliances for use during the peak electricity prices, or to supply power when the power grid is out of power / power outage.

[0073] See also Figure 5 , Figure 5 This is a schematic diagram of the structure of an energy storage system 400 according to an implementation scheme of the present application, and the present application Figure 5 The implementation plan is described using the shared energy storage scenario on the generation / distribution side as an example, and the energy storage device 1 of the present application is not limited to the energy storage scenario on the generation / distribution side.

[0074] The present application provides an energy storage system 400, which includes: a high-voltage cable 410, a first electric energy conversion device 420, a second electric energy conversion device 430 and an energy storage device 1 provided in the present application. In the case of power generation, the first electric energy conversion device 420 and the second electric energy conversion device 430 are used to convert other forms of energy into electric energy, which are connected to the high-voltage cable 410 and supplied to the power distribution network for use. When the power load is low and the first electric energy conversion device 420 and the second electric energy conversion device 430 generate excess power, the excess power is stored in the energy storage device 1, thereby reducing the wind and solar power abandonment rates and improving the problem of new energy power generation and consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 1 in conjunction with the high-voltage cable 410 in a grid-connected mode to the power consumption side, thereby providing peak shaving, frequency regulation, standby and other services for the power grid operation, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling of the power grid, and alleviating the power supply pressure of the power grid.

[0075] Optionally, the first electric energy conversion device 420 and the second electric energy conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electric energy.

[0076] The number of energy storage devices 1 can be multiple, and multiple energy storage devices 1 are connected in series or in parallel. Multiple energy storage devices 1 are supported and electrically connected by isolation plates (not shown). In this embodiment, "multiple" refers to two or more. An energy storage box can also be provided outside the energy storage device 1 to accommodate the energy storage device 1.

[0077] Optionally, the energy storage device 1 may include but is not limited to a battery module, a battery pack, a battery system, etc. Among them, the battery module may be a battery module formed by connecting multiple batteries of the present application in series / parallel, the battery pack may include multiple batteries of the present application, and the battery system may be a charging and discharging system including the battery or battery pack of the present application.

[0078] The actual application form of the energy storage device 1 provided in the embodiment of the present application may be, but is not limited to, the listed products, and may also be other application forms. The embodiment of the present application does not strictly limit the application form of the energy storage device 1. The embodiment of the present application only takes the energy storage device 1 as a multi-core battery as an example for explanation. When the energy storage device 1 is a single battery, the energy storage device 1 may be at least one of a cylindrical battery, a square battery, and the like.

[0079] Example

[0080] Hereinafter, the embodiments of the present application will be described in more detail with reference to preparation examples, examples and comparative examples. Various tests and evaluations were performed according to the following methods.

[0081] Example 1

[0082] <Preparation of positive electrode sheet>

[0083] <Preparation of the First Positive Electrode Material>

[0084] According to LiFe 0.99 Ti 0.01 PO 4 The iron source ferrous oxalate, the phosphorus source lithium dihydrogen phosphate, the carbon source glucose, the lithium source lithium carbonate and the titanium source titanium dioxide are weighed in the required stoichiometric ratio in / C, and are uniformly mixed on a ball mill, and then pure water is added as a dispersant, and then high-energy ball milling is performed; the ball-to-material ratio of the high-energy ball milling is 5:1, the rotation speed is 1200r / min, and the ball milling time is 15h; the material after high-energy ball milling is spray-dried, the pump speed of the spray drying is 10mL / min, and the drying temperature is 200℃ to form a first powder; the first powder is placed in a vacuum atmosphere sintering furnace for a first sintering treatment, the protective atmosphere is nitrogen, the sintering temperature and the sintering time are shown in Table 1, and the first powder is set aside after ball milling and crushing.

[0085] <Preparation of the Second Positive Electrode Material>

[0086] According to LiFe 0.99 Ti 0.01 PO 4The method comprises the following steps: weighing ferrous oxalate as an iron source, lithium dihydrogen phosphate as a phosphorus source, sucrose as a first carbon source, lithium carbonate as a lithium source and titanium dioxide as a titanium source in a stoichiometric ratio required in / C, and mixing them to obtain a mixed metal salt solution; preparing a strong alkali solution as a precipitant solution, and preparing ammonia water as a complexing agent solution; wherein the molar concentration of titanium in the mixed metal salt solution is 5 mol / L, the strong alkali solution is a sodium hydroxide solution with a molar concentration of 0.8 mol / L, and the molar concentration of ammonia water is 1 mol / L; placing the mixed metal salt solution, complexing agent solution and precipitant solution prepared above in a reaction kettle, stirring them continuously, maintaining the pH value of the reaction liquid at 9, and the reaction temperature at 20 0℃, reaction time is 10h, synthesis is carried out by precipitation reaction, and after solid-liquid separation, washing and drying, a first precursor material is obtained; the prepared first precursor material is mixed with the second carbon source mixed glucose in a mass ratio of 95:5, and then deionized water is added as a dispersant for ball milling, and then spray dried to form a second powder, wherein the ball-to-material ratio of the ball milling treatment is 4:1, the rotation speed is 1000r / min, the ball milling time is 10h, the pump speed of the spray drying is 10mL / min, and the drying temperature is 200℃; the second powder is subjected to a second sintering treatment, the sintering temperature and sintering time are shown in Table 1, and it is set aside after crushing treatment.

[0087] <Preparation of the First Positive Electrode Material Layer and the Second Positive Electrode Material Layer>

[0088] The first positive electrode material, conductive carbon black (Super-P), and binder PVDF are mixed in a mass ratio of 95:2:3, and then N-methylpyrrolidone (NMP) is added as a solvent to prepare a first slurry with a solid content of 50wt%, and stirred evenly, and then the first slurry is evenly coated on one surface of an aluminum foil with a thickness of 10μm, and dried at 85°C; the second positive electrode material, conductive carbon black (Super-P), and binder PVDF are mixed in a mass ratio of 95:2:3, and then NMP is added as a solvent to prepare a second slurry with a solid content of 50wt%, and stirred evenly, and then the second slurry is evenly coated on the surface of the first positive electrode material layer, and dried at 85°C; and then the positive electrode sheet is obtained after rolling, cutting, and other processes. Among them, the thickness of the first positive electrode material is 15μm, and the thickness of the second positive electrode material is 15μm.

[0089] <Preparation of Electrolyte>

[0090] Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1, dissolved and stirred thoroughly, and then placed in an environment of 5°C or less for 12 hours, and then lithium salt LiPF was added. 6 , and mix well to obtain an electrolyte. Among them, LiPF 6 The molar concentration in the electrolyte is 1 mol / L.

[0091] <Preparation of Separator>

[0092] A polyethylene (PE) porous polymer film with a thickness of 16 μm was used as the separator.

[0093] <Assembly of lithium-ion batteries>

[0094] The prepared positive electrode sheet and negative electrode sheet are respectively placed in a press for pressing, and then a puncher is used to cut out a circular positive electrode sheet with a diameter of 15 mm and a circular negative electrode sheet with a diameter of 18 mm respectively; then the circular positive electrode sheet, the diaphragm and the circular negative electrode sheet are stacked in order, so that the diaphragm is placed between the circular positive electrode sheet and the circular negative electrode sheet to play an isolating role, and then the prepared electrolyte is injected to assemble into a lithium-ion battery.

[0095] Embodiment 2 to Embodiment 5

[0096] In addition to adjusting the first sintering temperature according to Table 1 in <Preparation of the First Positive Electrode Material>, the average non-sphericity (i.e., k 1 ) and Dv50 (i.e. D 1 ), the rest is the same as Example 1.

[0097] Embodiment 6 to Embodiment 10

[0098] In addition to adjusting the temperature of the second sintering according to Table 1 in <Preparation of the Second Positive Electrode Material>, the average non-sphericity (i.e., k 2 ) and Dv50 (i.e. D 2 ), the rest is the same as Example 1.

[0099] Example 11 to Example 13

[0100] Except that the types of the first positive electrode material and the second positive electrode material are regulated according to Table 2 in <Preparation of the First Positive Electrode Material> and <Preparation of the Second Positive Electrode Material>, the rest is the same as Example 1.

[0101] Comparative Example 1

[0102] The above procedures are the same as those in Example 1, except that both the first positive electrode material layer and the second positive electrode material layer use the first positive electrode material.

[0103] Table 1 Preparation parameters of Examples 1 to 10 and Comparative Example 1

[0104]

[0105] In Table 1, “ / ” indicates that there is no relevant preparation parameter.

[0106] Table 2 Preparation parameters of Example 1, Example 11 to Example 13

[0107] Type of first cathode material Type of the second positive electrode material Example 1 <![CDATA[LiFe 0.99 You 0.01 PER 4 / C]]> <![CDATA[LiFe 0.99 You 0.01 PER 4 / C]]> Embodiment 11 <![CDATA[LiFe 0.98 You 0.02 PER 4 / C]]> <![CDATA[LiFe 0.98 You 0.02 PER 4 / C]]> Example 12 <![CDATA[LiFe 0.97 You 0.03 PER 4 / C]]> <![CDATA[LiFe 0.97 You 0.03 PER 4 / C]]> Embodiment 13 <![CDATA[LiFe 0.96 You 0.04 PER 4 / C]]> <![CDATA[LiFe 0.96 You 0.04 PER 4 / C]]>

[0108] Test methods and equipment:

[0109] Material particle size distribution test:

[0110] The particle size distribution of the first positive electrode material and the second positive electrode material was measured using a laser diffraction particle size distribution measuring instrument (Malvern Mastersizer 3000) according to the particle size distribution laser diffraction method (GB / T19077-2016), thereby measuring the Dv50 of the first positive electrode material and the second positive electrode material.

[0111] Calculation of the average non-sphericity of particles:

[0112] like Figure 6 As shown, first measure the actual area S and the longest diameter D of a positive electrode material particle, and then use the formula S = πd 2 / 4Convert the area S into an equivalent circle to obtain the diameter d of the equivalent circle, and the non-sphericity k is calculated by the following formula: k = (Dd) / D. The positive electrode material powder is selected as the measurement range under a scanning electron microscope at a magnification of 3k. The non-sphericity results of particles with a particle size ≥ 1μm are statistically analyzed by SEM at a magnification of 3k, that is, the average non-sphericity. In this application, the particle size of the positive electrode material is defined as the longest diameter D of the positive electrode material particles.

[0113] Positive electrode elongation test:

[0114] like Figure 7 As shown, the positive electrode sheet includes a positive electrode current collector 11, a first positive electrode material layer 12 and a second positive electrode material layer 13. Before rolling, two points A and B are marked on the surface of the first positive electrode material layer 12 or the surface of the second positive electrode material layer 13. 1 is the distance between points A and B before the positive electrode sheet is rolled; after being rolled by the roller 40, the positive electrode sheet will extend along its length direction, and the distance between points A and B will be lengthened, that is, the distance from A' to B', recorded as L 2 . Calculate the pole piece extension rate as S = (L 2 -L 1 ) / L 1 ×100%.

[0115] Compaction density test:

[0116] The powder compaction tester (model LD43.305) of Shanghai Lishi Company was used to measure the compaction density of the first positive electrode material and the second positive electrode material under a pressure of 3 kN according to the standard method GBT 24533-2019.

[0117] Rate performance test:

[0118] At 25° C., the lithium ion batteries prepared in the examples and comparative examples were charged to 3.75 V at a rate of 0.5 (C), and then discharged to 2.5 V at a rate of 0.5 C. The discharge capacity at this time was recorded as 0.5 C in units of mAh / g.

[0119] Table 3 Performance data of each embodiment and comparative example

[0120]

[0121]

[0122] Combining Table 1 and Table 3, it can be seen from Examples 1 to 10 and Comparative Example 1 that the elongation rate of Comparative Example 1 is high and the 0.5C discharge capacity is low. This may be because the positive electrode material layers on both sides of the positive electrode sheet of Comparative Example 1 are composed of the same positive electrode material, which makes it difficult to use the second positive electrode material to hinder the displacement and deformation of the positive electrode material particles when the positive electrode sheet is rolled, and lithium deposition occurs at the negative electrode interface of Comparative Example 1, resulting in a large capacity loss of the lithium-ion battery. The present application adjusts the k of the first positive electrode material layer to obtain a large capacity loss of the lithium-ion battery. 1 , D 1 and k of the second positive electrode material layer 2 , D 2 Within the above range, under the joint action of the first positive electrode material layer and the second positive electrode material layer, the risk of lithium plating at the negative electrode interface facing the inner side of the positive electrode sheet can be reduced while reducing the elongation of the positive electrode sheet, thereby improving the capacity performance of the lithium-ion battery.

[0123] The type of the first positive electrode material, the type of the second positive electrode material, etc. usually also have an impact on the performance of the positive electrode sheet. Combining Table 2 and Table 3, it can be seen from Examples 1 and 11 to 13 that, on the basis of the positive electrode sheet having the first positive electrode material layer and the second positive electrode material layer of the present application, by regulating the type of the first positive electrode material and the type of the second positive electrode material within the scope of the present application, it is beneficial to obtain a lithium-ion battery with low elongation and high capacity performance.

[0124] Figure 8 This is a photograph of the first negative electrode material layer of the negative electrode plate of the battery of Comparative Example 1 that was disassembled after being fully charged. It can be seen from the figure that the color at the negative electrode interface is darker and the surface haze becomes larger, indicating that obvious lithium precipitation occurs.

[0125] Fig. 9This is a photograph of the first negative electrode material layer of the negative electrode plate of Example 1 that was disassembled after the battery was fully charged. It can be seen from the figure that the color of the negative electrode interface is lighter and the reflective effect is obvious, indicating that lithium plating has not occurred. It can be seen that the positive electrode plate of the present application can reduce the risk of lithium plating at the negative electrode interface facing the inner side of the positive electrode plate.

[0126] Fig.10 This is a SEM image of the first positive electrode material prepared in Example 1 of the present application. Fig.10 It can be seen that the particles in the first positive electrode material are generally rounded, have a small degree of non-sphericity, and have a small particle size; Fig.11 This is a SEM image of the second positive electrode material prepared in Example 1 of the present application. Fig.11 It can be seen that there are more irregularly shaped particles in the second positive electrode material, the non-sphericity thereof is relatively large, and the particle size of the particles is relatively large.

[0127] The above is a detailed introduction to a positive electrode plate, a battery, an energy storage device and an electrical equipment disclosed in the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core inventions of the embodiments of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A positive electrode sheet, characterized in that: Applicable to a battery with a winding structure, the positive electrode sheet includes a positive electrode collector, a surface of the positive electrode collector away from the winding center is provided with a first positive electrode material layer, and a surface of the positive electrode collector facing the winding center is provided with a second positive electrode material layer, wherein: In the first positive electrode material layer, the average non-sphericity of the positive electrode material particles with a particle size greater than or equal to 1 μm is k1, and Dv50 is D1, 10%≤k1≤19%, 0.8 μm≤D1≤1.2 μm; In the second positive electrode material layer, the average non-sphericity of the positive electrode material particles with a particle size greater than or equal to 1 μm is k2, and Dv50 is D2, 21%≤k2≤35%, 1.2 μm≤D2≤1.7 μm.

2. The positive electrode sheet according to claim 1, characterized in that: 12%≤k1≤17%, 0.9μm≤D1≤1.1μm.

3. The positive electrode sheet according to claim 1 or 2, characterized in that: 26%≤k2≤33%, 1.4μm≤D2≤1.6μm.

4. The positive electrode sheet according to claim 1, characterized in that: The compaction density of the first positive electrode material layer and / or the second positive electrode material layer is 2.4 g / cm 3 ~2.6g / cm 3 .

5. The positive electrode sheet according to claim 1, characterized in that: The elongation of the positive electrode plate is 1.3% to 2.5%, and the 0.5C discharge specific capacity is 141 mAh / g to 147 mAh / g.

6. The positive electrode sheet according to claim 5, characterized in that: The elongation of the positive electrode plate is 1.3% to 2.0%, and the 0.5C discharge specific capacity is 143 mAh / g to 147 mAh / g.

7. The positive electrode sheet according to claim 1, characterized in that: The first positive electrode material layer comprises a first positive electrode material, the second positive electrode material layer comprises a second positive electrode material, and the first positive electrode material and / or the second positive electrode material have a chemical formula of LiFe x Ti y PO4 / C, x+y=1, and y≤0.

05.

8. A battery, characterized in that: The invention comprises the positive electrode sheet as described in any one of claims 1 to 7.

9. An energy storage device, characterized in that: The invention comprises a casing and at least one battery according to claim 8, wherein the battery is accommodated in the casing.

10. An electrical device, characterized in that: It includes the energy storage device as described in claim 9, and the energy storage device supplies power to the electrical equipment.

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