Cathode material, preparation method thereof, cathode sheet, battery and energy storage device

Abstract

The application provides a positive electrode material, a preparation method thereof, a positive electrode sheet, a battery and an energy storage device. The positive electrode material comprises first particles. The Dv50 of the first particles is D1, 1 microns <= D1 <= 8 microns. The surface region of the first particles has microcracks. The doping elements include at least one of titanium elements and vanadium elements. In the first particles, the molar ratio of iron elements to phosphorus elements at the microcracks is less than the molar ratio of iron elements to phosphorus elements in the internal region. The average concentration of the doping elements at the microcracks is C1, 4500 ppm <= C1 <= 8000 ppm.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a positive electrode material and its preparation method, a positive electrode sheet, a battery and an energy storage device. Background Technology

[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, and are widely used in various fields such as energy storage, portable electronic devices and electric vehicles.

[0003] Currently, high-voltage real-density cathode materials often require large-particle materials to be easily achieved, but large-particle materials can lead to poor cycle performance and affect safety performance. Summary of the Invention

[0004] To address the aforementioned technical problems, this application discloses a positive electrode material and its preparation method, a positive electrode sheet, a battery, and an energy storage device, in order to improve the cycle performance and overcharge safety performance of secondary batteries.

[0005] In the first aspect, this application provides a cathode material, wherein the cathode material includes a first particle, the first particle having a Dv50 of D1, 1μm≤D1≤8μm, and the surface region of the first particle having microcracks, the width of the microcracks being W, 5nm≤W≤200nm;

[0006] In the first particle, the molar ratio of iron to phosphorus at the microcrack is smaller than that in the internal region.

[0007] The average concentration of doping elements at the microcracks is C1, 4500ppm≤C1≤8000ppm, and the doping elements include at least one of titanium and vanadium.

[0008] In some embodiments of this application, the molar ratio of iron to phosphorus at the microcrack is K1, where 0.94 ≤ K1 ≤ 0.96;

[0009] The molar ratio of iron to phosphorus in the internal region is K2, where 0.96 < K2 ≤ 0.99.

[0010] In some embodiments of this application, the number of microcracks is 1 to 15.

[0011] In some embodiments of this application, the length of the microcrack is L, where 50nm≤L≤8μm.

[0012] In some embodiments of this application, the positive electrode material further includes a second particle, wherein the mass ratio of the first particle to the second particle is (20~40):(60~80).

[0013] And / or, the Dv50 of the second particle is D2, 0.2μm≤D2≤0.6μm.

[0014] Secondly, this application provides a method for preparing the cathode material described in the first aspect, comprising the following steps:

[0015] Iron phosphate, lithium source, dopant source and carbon source with an iron-to-phosphorus ratio of 0.955~0.975 are mixed, ball-milled and spray-dried, and then subjected to a first sintering treatment at a sintering temperature of 790℃~820℃ to obtain sintered products.

[0016] The sintered product is rolled by a roller press to obtain the first initial particles with microcracks on the surface;

[0017] Iron phosphate, lithium source, dopant source and carbon source with an iron-to-phosphorus ratio of 0.96~0.985 are mixed, ball-milled and spray-dried, and then subjected to a second sintering treatment at a sintering temperature of 680℃~780℃ to obtain the second initial particles.

[0018] The first initial particle, the second initial particle, the phosphorus source, the dopant element source and the carbon source are mixed to obtain a mixture. The mixture is then spray-dried and subjected to a third sintering treatment at a sintering temperature of 750℃~810℃ to obtain the cathode material.

[0019] In some embodiments of this application, the preparation method satisfies at least one of the following characteristics:

[0020] a) The sintering time for the first sintering treatment is 10~14h;

[0021] b) The sintering time for the second sintering treatment is 6-8 hours;

[0022] c) The sintering time for the third sintering treatment is 4~10h;

[0023] d) Roller pressure 20Mpa~30Mpa.

[0024] Thirdly, this application provides a positive electrode sheet, including a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector, the positive electrode material layer including the positive electrode material described in the first aspect.

[0025] Fourthly, this application provides a battery including the positive electrode sheet described in the third aspect.

[0026] Fifthly, this application provides an energy storage device, including a housing and at least one battery as described in the fourth aspect, the battery being housed within the housing.

[0027] In a sixth aspect, this application provides an electrical device including the energy storage device described in the fifth aspect, wherein the energy storage device supplies power to the electrical device.

[0028] Compared with the prior art, this application has at least the following beneficial effects:

[0029] This application provides a cathode material and its preparation method, a cathode electrode sheet, a battery, and an energy storage device. The cathode material includes a first particle with a Dv50 of D1, where 1 μm ≤ D1 ≤ 5 μm. The surface region of the first particle has microcracks with a width of W, where 5 nm ≤ W ≤ 200 nm. These microcracks reduce the stress on the first particle, making it less prone to larger cracks. In the first particle, the molar ratio of iron to phosphorus at the microcracks is lower than that in the internal region. Furthermore, the average concentration of doped elements at the microcracks is C1, where 4500 ppm ≤ C1 ≤ 8000 ppm. This reduces iron dissolution and migration at the cracks in the first particle, preventing iron deposition on the negative electrode and increasing side reactions. The higher iron-to-phosphorus ratio in the internal region improves lithium battery capacity and increases the lithium-ion-electron migration rate, thereby enhancing energy efficiency. This application improves the cycle performance, energy efficiency, and overcharge safety of lithium batteries while maintaining the high compaction density of the cathode material. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the structure of an energy storage system according to one embodiment of this application;

[0032] Figure 2 This is a schematic diagram of the energy storage system according to another embodiment of this application;

[0033] Figure 3 This is a schematic diagram of the energy storage system according to another embodiment of this application;

[0034] Figure 4 This is a scanning electron microscope (SEM) image of the cathode material prepared in Example 1 of this application.

[0035] Explanation of reference numerals in the attached drawings: 400-Energy storage system, 410-First power conversion device, 420-First user load, 430-Second user load, 440-Energy storage device, 450-High voltage cable, 460-Second power conversion device, 470-Vehicle, 480-Photovoltaic-energy storage-charging station. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0038] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0039] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0040] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0041] It should be noted that this application uses lithium-ion batteries as an example of secondary batteries to explain the application, but the secondary batteries in this application are not limited to lithium-ion batteries.

[0042] Because of the long particle size of the ions in the large positive electrode material, it is prone to large cracks due to stress during charge and discharge cycles. These large cracks can cause iron in the large positive electrode material to dissolve and deposit on the negative electrode, resulting in a decrease in battery cycle performance. Furthermore, during overcharging, iron elements at the large cracks will migrate to the negative electrode, leading to a large number of side reactions on the negative electrode and affecting battery safety performance.

[0043] In view of this, this application provides a cathode material comprising a first particle, wherein the first particle has a Dv50 of D1, where 1 μm ≤ D1 ≤ 8 μm, for example, D1 is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or 8 μm. The surface region of the first particle has microcracks, the width of which is W, where 5 nm ≤ W ≤ 200 nm, for example, W is 5 nm, 10 nm, 20 nm, 50 nm, 100 nm, 150 nm, or 200 nm. These microcracks can be formed by pre-pressing the first particle under appropriate pressure. In the first particle, the molar ratio of iron to phosphorus at the microcracks is less than that in the internal region; the average concentration of doped elements at the microcracks is C1, where 4500 ppm ≤ C1 ≤ 8000 ppm, for example, C1 is 4500 ppm, 5000 ppm, 6000 ppm, 6500 ppm, 7000 ppm, or 8000 ppm. The doping elements in this application include, but are not limited to, at least one of titanium and vanadium.

[0044] In this application, the surface region refers to the region in the cross-section of the first particle that is more than 60% away from the center of the first particle; the internal region refers to the region in the cross-section of the first particle that is less than 60% away from the center of the first particle.

[0045] The cathode material provided in this application has microcracks on the surface of the first particle. These microcracks reduce the stress on the first particle, making it less likely for larger cracks to form. Furthermore, the degree of iron dissolution is lower in the microcracks compared to larger cracks. In the first particle, the molar ratio of iron to phosphorus at the microcracks is lower than that in the internal region (hereinafter referred to as the iron-phosphorus ratio). Additionally, the average concentration of doped elements at the microcracks is C1, with a concentration of 4500ppm≤C1≤8000ppm. This reduces iron dissolution and migration at the cracks in the first particle, thus preventing iron deposition on the negative electrode and increased side reactions. The higher iron-phosphorus ratio in the internal region increases battery capacity and lithium-ion-electron migration rate, improving energy efficiency. While maintaining the high compaction density of the cathode material, this improves the cycle performance, energy efficiency, and overcharge safety of the lithium battery.

[0046] In one optional embodiment, the molar ratio of iron to phosphorus at the microcrack is K1, where 0.94 ≤ K1 ≤ 0.96, for example, K1 is 0.94, 0.95, or 0.96; the molar ratio of iron to phosphorus in the internal region is K2, where 0.96 < K2 ≤ 0.99, for example, K2 is 0.965, 0.97, 0.975, 0.98, or 0.99. When K1 and K2 are within the above ranges, the dissolution and migration of iron at the crack of the first particle serving as the cathode material can be reduced, and the internal region has a higher iron-phosphorus ratio, which can also increase battery capacity and the lithium-ion-electron migration rate, thereby improving energy efficiency.

[0047] In one alternative embodiment, the number of microcracks is 1 to 15. For example, the number of microcracks may be 1, 5, 10, or 15. With the number of microcracks within this range, the stress generated during battery cycling can be reduced, thus decreasing the stress on the first particle and making it less likely for the first particle to develop larger cracks.

[0048] In one optional embodiment, the length of the microcrack is L, 50 nm ≤ L ≤ 8 μm, for example, L is 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 500 nm, 1 μm, 5 μm, or 8 μm. When L is within the above range, the microcracks can reduce the stress generated during battery cycling, thereby reducing the stress on the first particle and making it less likely for the first particle to develop larger cracks. Furthermore, the number and width of the microcracks within the scope of this application are conducive to sufficient stress release, making the cathode material particles less prone to cracking.

[0049] In one optional embodiment, the cathode material further includes a second particle, and the mass ratio of the first particle to the second particle is (20~40):(60~80). For example, the mass ratio of the first particle to the second particle is 20:80, 30:70 or 40:60. In this way, the energy density and energy efficiency of the lithium-ion battery can be improved while ensuring the high compaction density.

[0050] In one alternative embodiment, the Dv50 of the second particle is D2, where 0.2 μm ≤ D2 ≤ 0.6 μm. For example, D2 is 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, or 0.6 μm. The second particle has a smaller average particle size than the first particle, thereby forming a particle size distribution with the first particle, which can increase the compaction density of the cathode material and thus improve the energy density of the lithium-ion battery.

[0051] In this application, Dv50 represents the particle size that, in the volumetric particle size distribution, reaches 50% of the total volumetric size, starting from the smallest particle size.

[0052] In one alternative embodiment, the first particle also has a carbon coating layer, so that the carbon surface repair can further inhibit the dissolution of iron in the first particle and prevent the electrolyte from corroding the first particle.

[0053] This application also provides a method for preparing the cathode material according to any of the above embodiments, comprising the following steps:

[0054] Step A: Mix iron phosphate, lithium source, dopant source and carbon source with an iron-to-phosphorus ratio of 0.955~0.975, then ball mill and spray dry, and then sinter at a temperature of 790℃~820℃ for 10h~14h to obtain sintered products. Then roll the sintered products through a roller press at a pressure of 20Mpa~30Mpa to create microcracks on the surface of the sintered products to obtain the first initial particles.

[0055] Step B: Iron phosphate, lithium source, doping element source and carbon source with an iron-to-phosphorus ratio of 0.96~0.985 are mixed according to the lithium iron phosphate ratio, and then ball-milled, spray-dried and sintered at a temperature of 680℃~780℃ for 6h~8h to obtain the second initial particles.

[0056] Step C: Mix the first initial particle, the second initial particle, the phosphorus source, the dopant element source and the carbon source to obtain a mixture, spray dry it, and then sinter it at a temperature of 750℃~810℃ for 4h~10h. After crushing, a cathode material containing the first particle and the second particle is obtained.

[0057] In steps A and B, the iron phosphate and lithium source can be mixed according to the stoichiometric ratio of lithium iron phosphate. The amount of dopant source added can be adjusted by technicians according to the designed doping content. The amount of carbon source added can be adjusted by technicians according to the designed carbon content. The lithium source includes, but is not limited to, lithium carbonate. The dopant source includes, but is not limited to, at least one of tetrabutyl titanate and amine metavanadate. The carbon source is composed of glucose and polyethylene glycol (PEG) in a mass ratio of 0~100:100~0, that is, the carbon source can be entirely glucose, entirely PEG, or a mixture of glucose and PEG. By controlling the sintering temperatures of steps A and B within the above ranges, the Dv50 of the first and second particles can be controlled. Doping with metal elements can enhance the MO bond energy (M is the doping metal element) in the first and / or second particles, stabilize the crystal structure of the first and / or second particles, and especially suppress the dissolution of iron in the first particle.

[0058] In step C, the phosphorus source includes, but is not limited to, phosphoric acid, and the amount added is 0.05% to 0.5% of the total mass of the mixture; the dopant source includes, but is not limited to, at least one of tetrabutyl titanate and amine metavanadate; the carbon source is a mixture of glucose and polyethylene glycol (PEG) in a mass ratio of 0 to 100: 100 to 0, that is, the carbon source can be all glucose, or all PEG, or a mixture of glucose and PEG.

[0059] In step C, a secondary sintering process is used to form a carbon coating layer on the surface of the first and second particles, which further inhibits the dissolution of iron in the cathode material and prevents the electrolyte from corroding the first particle.

[0060] In this application, the values ​​of K1 and K2 typically vary with the amount of phosphoric acid added during the preparation of the cathode material. For example, the values ​​of K1 and K2 typically decrease with the increase of phosphoric acid addition. Based on this, the values ​​of K1 and K2 can be adjusted by adjusting the amount of phosphoric acid added. The average number of microcracks in the first particle typically increases with the increase of rolling pressure. Based on this, the average number of microcracks in the first particle can be adjusted by adjusting the rolling pressure. The Dv50 of the first particle and the Dv50 of the second particle typically increase with the increase of sintering temperature. Based on this, the Dv50 of the first particle and the Dv50 of the second particle can be adjusted by adjusting the sintering temperature.

[0061] This application also provides a positive electrode sheet, which includes a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector, wherein the positive electrode material layer includes the positive electrode material described in any of the above embodiments.

[0062] In one optional embodiment, the areal density of the positive electrode material layer is 0.3 g / 1540.25 mm. 2 ~0.6g / 1540.25mm 2 ; and / or, the compaction density of the positive electrode material layer is 2.4 g / cm³. 3 ~2.7g / cm 3 This is beneficial for increasing the capacity of lithium-ion batteries. For example, the areal density of the positive electrode material layer is 0.3 g / 1540.25 mm². 2 0.4g / 1540.25mm 2 0.5g / 1540.25mm 2 Or 0.6g / 1540.25mm 2 The compaction density of the positive electrode material layer is 2.4 g / cm³. 3 2.5g / cm 3 2.6g / cm 3 Or 2.7g / cm 3 .

[0063] This application also provides a battery including the positive electrode sheet described in any of the above embodiments.

[0064] In this application, the positive electrode material layer can be disposed on one surface or on two surfaces along the thickness direction of the positive electrode current collector. Specifically, the positive electrode material layer can be disposed on a portion or the entire surface of the positive electrode current collector. The positive electrode current collector is not particularly limited in this application, as long as it achieves the purpose of this application; for example, it can be, but is not limited to, aluminum foil, aluminum alloy foil, or composite current collectors. The thickness of the positive electrode current collector is not particularly limited in this application, as long as it achieves the purpose of this application; for example, a thickness of 4 μm to 15 μm is acceptable. The single-sided thickness of the positive electrode material layer in this application can be 60 μm to 140 μm.

[0065] The lithium-ion battery of this application also includes a negative electrode sheet. This application does not impose any particular limitation on the negative electrode sheet, as long as it achieves the purpose of this application. For example, the negative electrode sheet typically includes a negative current collector and a negative electrode material layer. The negative electrode material layer can be disposed on one or both surfaces along the thickness direction of the negative current collector. In this application, the negative electrode material layer is disposed on the surface of the negative current collector; that is, the negative electrode material layer can be disposed on a portion of one surface of the negative current collector, or it can be disposed on the entire surface of one surface of the negative current collector. This application does not impose any particular limitation on the negative current collector, as long as it achieves the purpose of this application. For example, it can include, but is not limited to, copper foil, copper alloy foil, nickel foil, or composite current collectors. In this application, there is no particular limitation on the thickness of the negative current collector, as long as it achieves the purpose of this application, for example, a thickness of 4μm to 12μm. The single-sided thickness of the negative electrode material layer in this application can be 70μm to 200μm.

[0066] In this application, the negative electrode material layer includes a negative electrode material. The negative electrode material is not particularly limited, as long as it can achieve the purpose of this application. For example, it may include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon, and silicon-carbon.

[0067] In this application, the negative electrode material layer may also include a negative electrode binder. This application does not impose any particular limitation on the negative electrode binder, as long as it can achieve the purpose of this application. For example, it may include, but is not limited to, at least one of acrylate, polyamide, polyimide, polyamide-imide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, and potassium carboxymethyl cellulose.

[0068] The lithium-ion battery of this application also includes a separator. This application does not impose any particular limitation on the separator; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane 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 membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.

[0069] The battery of this application also includes an electrolyte. This application does not impose any particular limitations on the electrolyte; those skilled in the art can choose according to actual needs, as long as it achieves the purpose of this application. 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), ethylene ethylene carbonate (VEC), or fluoroethylene carbonate (FEC) can be mixed in a certain mass or volume ratio to obtain a non-aqueous organic solvent, and then a lithium salt can be added to dissolve and mix evenly. This application does not limit the type of lithium salt, as long as it achieves the purpose of this application. For example, lithium salts may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, lithium bis(fluorosulfonyl)imide (LIFSI), lithium dioxalatoborate (LiBOB), or lithium difluoroborate.

[0070] This application does not impose any particular limitation on the concentration of lithium salt in the electrolyte, as long as the purpose of this application can be achieved. For example, the concentration of lithium salt can be 1.0 mol / L to 2.0 mol / L.

[0071] The battery of this application also includes a casing. This application does not impose any particular restrictions on the casing, and those skilled in the art can choose one according to actual needs, as long as it can achieve the purpose of this application. For example, the casing may include an aluminum-plastic film.

[0072] This application does not impose any particular limitation on the battery preparation method; any preparation method known in the art can be used, as long as it can achieve the purpose of this application. For example, the battery preparation method includes, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a bare cell with a wound structure; placing the bare cell in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the battery.

[0073] This application also provides an energy storage device, including a housing and at least one battery as described in any of the above embodiments, the battery being housed within the housing. The energy storage device with this battery exhibits excellent performance, which is beneficial for its use. Housing the battery within the housing increases its stability and protection, thereby extending the lifespan of the energy storage device. It is understood that the energy storage device may contain one or more batteries, and when the energy storage device contains multiple batteries, the multiple batteries can be connected in at least one manner, such as parallel or series connection.

[0074] This application also provides an electrical device including the energy storage device described in the above embodiments, which is beneficial for improving the product competitiveness and performance of the electrical device. In an optional embodiment, 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 embodiment, the electrical device body includes a positive terminal and a negative terminal, the positive electrode of the battery in the energy storage device is used to electrically connect to the positive terminal of the electrical device body, and the negative electrode of the battery in the energy storage device is used to electrically connect to the negative terminal of the electrical device body, so as to supply power to the electrical device.

[0075] The electrical equipment in this application may include, but is not limited to: containers, electric vehicles, electric cars, ships, spacecraft, electric toys, and power tools, etc. Among them, spacecraft include, for example, airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include, for example, stationary or mobile electric toys, specifically, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include, for example, metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, specifically, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0076] Because the energy we need is highly time- and space-dependent, in order to utilize energy rationally and improve energy efficiency, it is necessary to store one form of energy in the same way or by converting it into another, and then release it in a specific energy form for future applications. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0077] Currently, the generation of green electricity generally relies on solar, wind, and hydropower. However, wind and solar power are generally characterized by strong intermittency and large fluctuations, which can cause grid instability, insufficient power during peak demand periods, and excessive power during off-peak periods. Unstable voltage can also damage the power grid. Therefore, insufficient electricity demand or insufficient grid capacity may lead to the problem of "wind and solar curtailment." Solving these problems requires energy storage. This involves converting electrical energy into other forms of energy through physical or chemical means and storing it. When needed, this energy can be converted back into electrical energy and released. Simply put, energy storage is like a large "power bank," storing electrical energy when solar and wind power are abundant and releasing the stored electricity when needed.

[0078] Taking electrochemical energy storage as an example, this solution provides an energy storage device 440, which is applied to an energy storage system 400. The energy storage device 440 is equipped with a set of chemical batteries, which mainly use the chemical elements in the batteries as energy storage medium. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage medium. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electrical energy is released for use, or transferred to places with a shortage of electricity for use.

[0079] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding types of energy storage devices include:

[0080] (1) Large-scale energy storage power stations (composed of multiple prefabricated energy storage modules) applied to wind power and photovoltaic power stations can help renewable energy power generation meet grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, the energy storage power station realizes the load matching of power in time and space, enhances the renewable energy absorption capacity, reduces instantaneous power changes, reduces the impact on the power grid, improves the problem of new energy power generation absorption, and is of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation.

[0081] (2) The energy storage prefabricated cabin applied on the grid side mainly functions as peak shaving, frequency regulation and relief of grid congestion. In terms of peak shaving, it can realize peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak period of electricity load, thereby achieving a balance between power production and consumption.

[0082] (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system when the electricity price is low and discharging the energy storage system when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use energy storage systems to store energy during off-peak hours and discharge during peak loads, thereby reducing peak power and the maximum demand declared, achieving the goal of reducing capacity costs. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0083] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application. Figure 1 This application Figure 1 The embodiments are illustrated using a home energy storage scenario in user-side energy storage as an example. The energy storage device 440 of this application is not limited to the home energy storage scenario.

[0084] This application provides an energy storage system 400, which includes a first power conversion device 410 (photovoltaic panel), a first user load 420 (household lighting fixture), a second user load 430 (e.g., household appliances such as air conditioners), and an energy storage device 440. The energy storage device 440 is a small energy storage box that can be wall-mounted on an outdoor wall. However, the energy storage device 440 is not limited to wall mounting and can also be placed in a user's residence in other ways. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 440 stores this electrical energy and supplies it to lighting fixtures and household appliances during peak electricity prices, or provides power during power outages / power interruptions.

[0085] In some embodiments, see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application. Figure 1 And this application Figure 2 The embodiments are illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 440 of this application is not limited to the energy storage scenario on the generation / distribution side.

[0086] This application provides an energy storage system 400, which includes: a high-voltage cable 450, a first power conversion device 410, a second power conversion device 460, and an energy storage device 440 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 460 can be a wind power conversion device. Since the electricity generated by wind power conversion is volatile, random, and intermittent, the unstable electricity output by the wind power conversion device can be stored in the energy storage device 440 through grid connection. The energy storage device 440 is connected to the high-voltage cable and outputs smooth electricity to the power consumption side of the distribution network, realizing peak shaving and frequency regulation, and stable grid operation; or, wind power... The conversion device is always connected to the high-voltage cable. Under normal power generation conditions, the power output of the wind power conversion device is supplied to the power consumption side of the distribution network through the high-voltage cable. When the current power load is low and the wind power conversion device generates excess power, the excess power is first stored in the energy storage device 440 to reduce wind and solar curtailment rates and improve the problem of new energy power generation consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 440 together with the high-voltage cable 450 in grid-connected mode to supply power to the power consumption side. This provides the power grid with various services such as peak shaving, frequency regulation, and backup, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure of the power grid.

[0087] In some embodiments on the distribution network side, the first power conversion device 410 can be a photovoltaic panel, and the energy storage device 440 is connected to the high-voltage cable 450 and installed downstream of the high-voltage cable 450 and between the user load. The electrical energy output by the photovoltaic power conversion device is stored in the energy storage device 440, which can respond in a timely manner to act as a backup power source when the power grid / distribution network fails; or, it can provide power supply support to alleviate line congestion when the high-voltage cable 450 transmission line is blocked, and to delay the economic pressure caused by the expansion of the power grid / distribution capacity when the power grid is planned to be expanded.

[0088] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application. Figure 3 And this application Figure 3 The embodiments are illustrated using an industrial and commercial energy storage scenario as an example. The energy storage device 440 of this application is not limited to industrial and commercial energy storage scenarios.

[0089] This application provides an energy storage system 400, which includes: an energy storage device 440, a high-voltage cable 450, a factory equipped with a first power conversion device 410, a photovoltaic-energy storage-charging station 480, and a vehicle 470. In some embodiments of industrial and commercial scenarios, the first power conversion device 410 can be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage device 440 in the factory. In the event of a power grid failure, the energy storage device 440 provides power to ensure the safe and stable operation of the factory without interruption. Alternatively, when the factory's power load is high, the power grid issues an instruction to transmit the electricity stored in the energy storage device 440 in conjunction with the high-voltage cable 450 in a grid-connected mode to supply the factory with electricity, providing various services such as peak shaving / frequency regulation and backup for the power grid operation. In addition, the first power conversion device 410 can also convert solar energy into electrical energy and store it in the energy storage device 440 of the photovoltaic-energy storage-charging station 480, which can then directly charge the vehicle 470, making it fast and convenient.

[0090] Optionally, the first power conversion device 410 may include, but is not limited to, a photovoltaic panel, and the second power conversion device 460 may include, but is not limited to, a wind power conversion device. The first power conversion device 410 and the second power conversion device 460 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0091] Optionally, the energy storage device 440 may include, but is not limited to, energy storage applications such as energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and may also be applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0092] Optionally, the energy storage device 440 may include, but is not limited to, individual batteries, or battery modules, battery packs, battery clusters, power banks, energy storage cabinets / prefabricated energy storage compartments, and other battery integrated systems composed of individual batteries. The actual application form of the energy storage device 440 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 440.

[0093] Optionally, the individual cell can be, but is not limited to, at least one of cylindrical, prismatic, prismatic, or other shaped cells.

[0094] Optionally, the single cell can be a rechargeable battery, which refers to a single cell that can be recharged after discharge to activate the active materials and continue to be used. The single cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application does not specifically limit it.

[0095] Example

[0096] The following examples, embodiments, and comparative examples illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below.

[0097] Example 1

[0098] <Preparation of the first initial particles>

[0099] Iron phosphate (with an iron-to-phosphorus ratio of 0.962), lithium source, dopant source, and carbon source were mixed in stoichiometric proportions, followed by ball milling, spray drying, and sintering at 800℃ for 12 hours to obtain the sintered product. The sintered product was then rolled using a roller press at a pressure of 25 MPa to induce microcracks on the surface, yielding the first initial particles. The lithium source was lithium carbonate, the dopant source was TiO2, and the carbon source consisted of glucose and PEG in a mass ratio of 70:30. The molar ratio of lithium carbonate to iron phosphate was 1.04. The dopant compound accounted for 0.5% of the total mass of the mixture, and the carbon source accounted for 6%.

[0100] <Preparation of the Second Initial Particle>

[0101] Iron phosphate (with an iron-to-phosphorus ratio of 0.971), a lithium source, a dopant source, and a carbon source were mixed in stoichiometric proportions, followed by ball milling, spray drying, and sintering at 730℃ for 6 hours to obtain the second initial particles. The lithium source was lithium carbonate, the dopant source was TiO2, and the carbon source consisted of glucose and PEG in a mass ratio of 70:30. The molar ratio of lithium carbonate to iron phosphate was 1.03. The dopant compound accounted for 0.67% of the total mass of the mixture, and the carbon source accounted for 6%.

[0102] <Preparation of cathode materials>

[0103] A mixture of first initial particles, second initial particles, a phosphorus source, a dopant source, and a carbon source was obtained. This mixture was then spray-dried and sintered at 780℃ for 6 hours. After crushing, a cathode material containing the first and second initial particles was obtained. The mass ratio of the first to the second initial particles was 30:70. The phosphorus source was phosphoric acid, added at 0.2% of the total mass of the mixture. The dopant source was TiO2, added at 1.5% of the total mass of the mixture. The carbon source consisted of glucose and PEG in a mass ratio of 5:95, added at 3% of the total mass of the mixture. The Dv50 of the first particle was 1.6 μm, and the Dv50 of the second particle was 0.5 μm.

[0104] <Preparation of the positive electrode>

[0105] The prepared positive electrode material, conductive carbon black (Super-P), and binder PVDF were mixed at a mass ratio of 94:3:3. N-methylpyrrolidone (NMP) was then added as a solvent to prepare a positive electrode slurry with a solid content of 65 wt%. The mixture was stirred until homogeneous. The positive electrode slurry was then uniformly coated onto one surface of a 15 μm thick aluminum foil current collector. After drying, cold pressing, slitting, and cutting, the positive electrode sheet was obtained. The single-sided thickness of the positive electrode material layer was 100 μm, and the single-sided areal density was 0.385 g / 1540.25 mm. 2 The compacted density is 2.5 g / cm³. 3 .

[0106] <Preparation of Negative Electrode Sheets>

[0107] Artificial graphite (anode material), sodium carboxymethyl cellulose (CMC) thickener, Super-P conductive carbon black, and styrene-butadiene rubber latex (SBR) binder were mixed in a mass ratio of 96:2:1:1. Deionized water was added to prepare a negative electrode slurry with a solid content of 50 wt%, and the mixture was stirred evenly. The negative electrode slurry was uniformly coated onto one surface of a 6 μm thick copper foil current collector. After drying, cold pressing, slitting, and cutting, the negative electrode sheet was obtained. The single-sided thickness of the negative electrode material layer was 85 μm.

[0108] <Preparation of Electrolyte>

[0109] In an argon-atmosphere glove box with a moisture content ≤1ppm, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 1:1:1. The dried solute was then dissolved in the solvent and stirred until completely dissolved and homogeneous to obtain the electrolyte. The solute in the electrolyte was lithium hexafluorophosphate, with a molar concentration of 1.2 mol / L.

[0110] <Preparation of the diaphragm>

[0111] A porous polyethylene (PE) membrane with a thickness of 16 μm was used as the separator.

[0112] <Lithium-ion battery assembly>

[0113] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrode. Then, they are wound into a bare cell. After welding the tabs, the bare battery is placed in an outer packaging shell, dried, and then injected with the electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0114] Examples 2-3

[0115] Except for adjusting the amount of phosphoric acid added according to Table 1 in the <Preparation of Cathode Material>, and changing K1 and K2 accordingly, the rest is the same as in Example 1.

[0116] Example 4

[0117] Except for adjusting the roller pressure to 35 MPa in the <Preparation of the First Initial Particle>, and the change in the average number of microcracks in the first particle as shown in Table 1, the rest is the same as in Example 1.

[0118] Example 5

[0119] Except for adjusting the roller pressure to 42 MPa in the <Preparation of the First Initial Particle>, and the change in the average number of microcracks in the first particle as shown in Table 1, the rest is the same as in Example 1.

[0120] Examples 6-7

[0121] Except for adjusting the mass ratio of the first initial particle to the second initial particle in the <Preparation of Cathode Material> section, where the mass ratio of the first particle to the second particle is varied according to Table 1, the rest is the same as in Example 1.

[0122] Examples 8-9

[0123] Except for the adjustment of the amount of dopant source added according to Table 1 in the <Preparation of Cathode Material>, which resulted in a change in the average concentration of dopant at the surface crack, the rest is the same as in Example 1.

[0124] Examples 10-11

[0125] Except for adjusting the amount of carbon source according to Table 1 in the <Preparation of Cathode Material> section, the rest is the same as in Example 1.

[0126] Example 12

[0127] Except for adjusting the sintering temperature to 790°C in the <Preparation of the First Initial Particle> section to adjust the Dv50 of the subsequently prepared first particle to 1 μm, the rest is the same as in Example 1.

[0128] Example 13

[0129] Except for adjusting the sintering temperature to 820°C in the <Preparation of the First Initial Particle> section to adjust the Dv50 of the subsequently prepared first particle to 8 μm, the rest is the same as in Example 1.

[0130] Example 14

[0131] Except for the use of amine metavanadate as the dopant source in <Preparation of the first initial particle>, <Preparation of the second initial particle>, and <Preparation of the cathode material>, the rest are the same as in Example 1.

[0132] Comparative Example 1

[0133] Except that rolling is not performed in the <Preparation of the First Initial Particles>, the rest is the same as in Example 1.

[0134] Comparative Example 2

[0135] Except for the fact that no dopant source is added in the <Preparation of Cathode Material>, the rest is the same as in Example 1.

[0136] Table 1: Preparation parameters of Examples 1-11 and Comparative Examples 1-2

[0137]

[0138] In Table 1, " / " indicates that no relevant preparation parameters exist.

[0139] Test methods and equipment:

[0140] Tests of iron-phosphorus ratio at the first particle crack and the iron-phosphorus ratio and doping element content in the internal region:

[0141] The iron-phosphorus ratio (FP-P) of the first particle profile surface and interior was tested using EDS. Specifically, in the spot scan mode of EDS, five points were uniformly selected in the interior region of the first particle profile. The instrument automatically analyzed the FP-P ratio and dopant content at each point, and the average value was taken to obtain the FP-P ratio and dopant content inside the particle. Similarly, on the surface region of the first particle profile, five points were selected within 50 nm of the crack. The instrument automatically analyzed the FP-P ratio and dopant content at each point, and the average value was taken to obtain the FP-P ratio and dopant content at the particle crack. The method for obtaining the cross-section of the first particle is as follows: The positive electrode sheet is placed on the sample stage, the heater is turned on, and the positive electrode sheet is cut into a rectangular sample of 1.1cm × 0.8cm. The sample is then glued to the sample stage using an adhesive stick. The sample stage is then removed from the heater using tweezers, the heater is turned off, and while the adhesive is still warm and firmly bonded, the sample stage is moved using tweezers so that one end of the sample protrudes 1mm~2mm from the sample stage. The cross-section of the positive electrode material layer of the protruding sample is then polished using argon sputtering from an ion cutter to obtain a cross-sectional sample. The largest particle cross-section in this cross-section is selected as the first particle cross-section. The internal region of the first particle refers to the area within 60% of the particle's center, and the surface region of the first particle refers to the area beyond 60% of the particle's center. Confirmation of the center of the first particle: The point with the smallest sum of squared distances from the edge points in the cross-section of the first particle; Confirmation of 60% area: In the cross-section of the first particle, with the center as the reference, connect the edge points to obtain the straight line length, take the point on the straight line length that is 60% of the distance from the center point as the target point, connect all the target points to form a surface, the area inside the surface is the internal area, and the area outside the surface is the external area.

[0142] Determining the number, length, and width of microcracks in the first particle:

[0143] Place the positive electrode sheet on the sample stage, turn on the heater, and cut the positive electrode sheet into a rectangular sample of 1.1cm × 0.8cm. Attach the sample to the sample stage using an adhesive stick. Then, use tweezers to remove the sample stage from the heater, turn off the heater, and while the adhesive is still warm and firmly bonded, move the sample stage with the tweezers so that one end of the electrode sample protrudes 1mm~2mm from the sample stage. Use argon sputtering with an ion cutter to grind the cross-section of the positive electrode material layer of the protruding electrode sample, obtaining a cross-sectional sample. Then, place the cross-sectional sample in the SEM chamber, locate the first particle with microcracks on the surface, and photograph it. Import the photograph into ImageJ software, locate the microcracks by color difference, count the number of microcracks, and measure the length and maximum width of the microcracks using a scale. Take 5 samples, and average the length and maximum width test results to obtain the length and width of the microcracks.

[0144] First and second particle Dv50 tests:

[0145] The Dv50 of the first and second particles was tested using a laser particle size analyzer.

[0146] Cathode material compaction density test:

[0147] The compaction density of the cathode material powder after decompression at 3T was tested using an electronic pressure testing machine (Lishi, model: LD43.305).

[0148] Charge-discharge cycle test:

[0149] The batteries obtained in the above embodiments and comparative examples were subjected to constant power charge-discharge cycle tests on a charge-discharge tester (model Xinwei CT-4064T-5V12A). The test temperature was 25℃, the charge-discharge power was 0.5P (charge-discharge power = battery voltage plateau × battery rated capacity), and the charge-discharge voltage window was 2.5V~3.65V (i.e., the battery charging cut-off voltage was 3.65V, and the battery discharging cut-off voltage was 2.5V; it is generally considered that when the charging cut-off voltage is ≥3.65V, the battery charging cut-off voltage is relatively high). The capacity retention rate after 500 cycles was calculated using the formula: Capacity retention rate after the nth cycle = (Discharge capacity after the nth cycle / Discharge capacity of the first cycle) × 100%. One complete charge-discharge cycle is usually referred to as one charge-discharge cycle, which means the battery is first charged from 2.5V to 3.65V, and then discharged from 3.65V to 2.5V, thus forming one charge-discharge cycle. N cycles are the same as repeating the above process N times.

[0150] Overcharge performance test:

[0151] The lithium-ion battery was charged to 3.65V at a constant current and constant voltage of 0.5C at 25℃, with a cutoff current of 0.05C. Then, the lithium-ion battery was placed in a safety test cabinet and charged to 5.475V at a constant current of 0.5C. It was then left to stand for 1 hour, and the time it took for the voltage to reach 5.475V was observed. A shorter cutoff time indicates less heat accumulation in the lithium-ion battery, and better overcharge safety performance.

[0152] Table 2: Performance data of each embodiment and comparative example

[0153]

[0154] As can be seen from Examples 1 to 14 and Comparative Examples 1 to 2, Comparative Example 1 has a low cycle capacity retention rate and a long overcharge cutoff time; although the cycle capacity retention rate of Comparative Example 2 has been improved to a certain extent, its overcharge cutoff time is still long; while the lithium-ion battery of this application exhibits good cycle performance and overcharge safety performance. It can be seen that by pre-cracking large particles and then coating and doping the pre-cracked areas with an appropriate amount, this application can improve the cycle capacity retention rate and overcharge safety performance of lithium-ion batteries.

[0155] Figure 4 This is a SEM image of the cathode material prepared in Example 1 of this application. Figure 4 It can be seen that the cathode material contains a first particle with a larger particle size and a second particle with a smaller particle size, and there are several microcracks in the first particle.

[0156] The above provides a detailed description of a positive electrode material and its preparation method, positive electrode sheet, battery, and energy storage device disclosed in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A positive electrode material, characterized in that, The cathode material includes a first particle and a second particle. The first particle has a Dv50 of D1, where 1μm≤D1≤8μm, and the second particle has a Dv50 of D2, where 0.2μm≤D2≤0.6μm. The surface region of the first particle has microcracks. In the first particle, the molar ratio of iron to phosphorus at the microcrack is smaller than that in the internal region. The average concentration of doping elements at the microcracks is C1, 4500ppm≤C1≤8000ppm, and the doping elements include at least one of titanium and vanadium. The width of the microcrack is W, where 5nm ≤ W ≤ 200nm; The surface region refers to the area outside 60% of the center of the first particle in its cross-section; the internal region refers to the area within 60% of the center of the first particle in its cross-section.

2. The cathode material according to claim 1, characterized in that, The molar ratio of iron to phosphorus at the microcrack is K1, where 0.94 ≤ K1 ≤ 0.96; The molar ratio of iron to phosphorus in the internal region is K2, where 0.96 < K2 ≤ 0.

99.

3. The cathode material according to claim 1, characterized in that, The number of microcracks is 1 to 15.

4. The cathode material according to claim 1, characterized in that, The length of the microcrack is L, and 50nm≤L≤8μm.

5. The positive electrode material according to claim 1, characterized in that, The mass ratio of the first particle to the second particle is (20~40): (60~80).

6. A method for preparing the cathode material according to any one of claims 1 to 5, characterized in that, Includes the following steps: Iron phosphate, lithium source, dopant source and carbon source with an iron-to-phosphorus ratio of 0.955~0.975 are mixed, ball-milled and spray-dried, and then subjected to a first sintering treatment at a sintering temperature of 790℃~820℃ to obtain sintered products. The sintered product is rolled by a roller press to obtain the first initial particles with microcracks on the surface; Iron phosphate, lithium source, dopant source and carbon source with an iron-to-phosphorus ratio of 0.96~0.985 are mixed, ball-milled and spray-dried, and then subjected to a second sintering treatment at a sintering temperature of 680℃~780℃ to obtain the second initial particles. The first initial particle, the second initial particle, the phosphorus source, the dopant element source and the carbon source are mixed to obtain a mixture. The mixture is then spray-dried and subjected to a third sintering treatment at a sintering temperature of 750℃~810℃ to obtain the cathode material.

7. The preparation method according to claim 6, characterized in that, The preparation method satisfies at least one of the following characteristics: a) The sintering time for the first sintering treatment is 10~14h; b) The sintering time for the second sintering treatment is 6-8 hours; c) The sintering time for the third sintering treatment is 4~10h; d) Roller pressure 20Mpa~30Mpa.

8. A positive electrode sheet, characterized in that, It includes a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector, wherein the positive electrode material layer includes the positive electrode material according to any one of claims 1 to 5.

9. A battery, characterized in that, Includes the positive electrode sheet as described in claim 8.

10. An energy storage device, characterized in that, It includes a housing and at least one battery as described in claim 9, the battery being housed within the housing.

11. An electrical appliance, characterized in that, The device includes the energy storage device of claim 10, which supplies power to the electrical equipment.

Images