Positive pole piece, battery and energy storage device

Abstract

The invention provides a positive pole piece, a battery and an energy storage device, the positive pole piece comprises a positive current collector, at least one surface of the positive current collector is provided with a positive material layer, and the positive material layer comprises a positive material; the positive electrode material comprises an inner core, wherein the inner core is of a hollow structure; a first coating layer and a second coating layer are sequentially arranged on the surface of the inner core, the material of the first coating layer is titanium element doped lithium manganese iron phosphate, and the material of the second coating layer is at least one of magnesium element and aluminum element doped lithium manganese iron phosphate; a plurality of cavities are formed between the first coating layer and the second coating layer, and in the cross section of the particles of the positive electrode material, the plurality of cavities surround the first coating layer.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a positive electrode, 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] Lithium manganese iron phosphate (LFP) materials offer relatively good safety and higher energy density compared to lithium iron phosphate (LFP). However, during cycling, manganese dissolves due to the Jan-Taylor effect, leading to decreased structural stability and side reactions with the electrolyte, thus affecting the cycle discharge capacity of the lithium battery. Furthermore, high-density cathode materials often require large particle sizes. During lithium battery cycling, these large particles undergo repeated expansion and contraction of the crystal structure due to lithium ion insertion and extraction, resulting in localized stress concentration and particle cracking, which also impacts the cycle discharge capacity. Summary of the Invention

[0004] To address the aforementioned technical problems, this application discloses a positive electrode sheet, a battery, and an energy storage device to suppress the breakage of lithium manganese iron phosphate material particles and the dissolution of manganese, thereby improving the cycle discharge capacity performance of lithium batteries based on lithium manganese iron phosphate material.

[0005] In a first aspect, this application provides a positive electrode sheet, including a positive current collector, wherein at least one side of the positive current collector has a positive electrode material layer, the positive electrode material layer comprising a positive electrode material; The cathode material includes a core, which has a hollow structure; The surface of the core is sequentially provided with a first coating layer and a second coating layer, wherein the material of the first coating layer is lithium manganese iron phosphate doped with titanium, and the material of the second coating layer is lithium manganese iron phosphate doped with at least one of magnesium or aluminum. There are multiple cavities between the first coating layer and the second coating layer, and in the cross-section of the positive electrode material particles, the multiple cavities surround the first coating layer.

[0006] In some embodiments of this application, the area of ​​the hollow structure in the cross-section of the positive electrode material particles accounts for A of the total cross-sectional area, where 10% ≤ A ≤ 40%.

[0007] In some embodiments of this application, the area of ​​the plurality of cavities in the cross-section of the positive electrode material particles accounts for B of the total area of ​​the cross-section, where 0.5% ≤ B ≤ 5%.

[0008] In some embodiments of this application, the Dv50 of the cathode material is D1, where 6μm≤D1≤8μm.

[0009] In some embodiments of this application, the material of the first coating layer has the chemical formula LiMn. x Fe 1-x- y Ti y PO4, 0.5≤x≤0.8, 0.01≤y≤0.05.

[0010] In some embodiments of this application, the material of the second coating layer has the chemical formula LiMn m Fe 1-m- n M n PO4, M is magnesium and / or aluminum, 0.5≤m≤0.8, 0.01≤n≤0.05.

[0011] In some embodiments of this application, the hollow structure is an ellipsoidal hollow structure or a near-ellipsoidal hollow structure.

[0012] In some embodiments of this application, the cathode material also has a carbon coating layer.

[0013] Secondly, this application provides a battery including the positive electrode sheet described in the first aspect.

[0014] Thirdly, this application provides an energy storage device, including a housing and at least one battery as described in the second aspect, the battery being housed within the housing.

[0015] Fourthly, this application provides an electrical device including the energy storage device described in the third aspect, wherein the energy storage device supplies power to the electrical device.

[0016] Compared with the prior art, this application has at least the following beneficial effects: This application provides a positive electrode sheet, a battery, an energy storage device, and an electrical device. The positive electrode sheet includes a positive current collector, at least one side of which has a positive electrode material layer, comprising a positive electrode material. The positive electrode material includes a core with a hollow structure, which can alleviate internal stress concentration caused by volume changes in the material's crystal structure and suppress particle breakage of the positive electrode material. A first coating layer and a second coating layer are sequentially disposed on the surface of the core. The first coating layer is made of titanium-doped lithium manganese iron phosphate, and the high-valence cation doping material crystal structure in the first coating layer improves the electronic conductivity and lithium-ion diffusion rate of lithium manganese iron phosphate. The second coating layer is made of magnesium or aluminum. At least one type of lithium manganese iron phosphate doped with this material can suppress the Jameer-Taylor effect, reduce manganese dissolution and side reactions caused by direct contact between manganese and the electrolyte, thereby improving the structural stability of the cathode material and reducing the degree of particle breakage. Multiple cavities exist between the first and second coating layers. In the cross-section of the cathode material particles, these cavities surround the first coating layer, forming a cavity connecting layer. The presence of these cavities promotes electrolyte wetting of the lithium manganese iron phosphate material in the first coating layer, increasing the lithium-ion diffusion rate. Furthermore, the cavities distributed around the first coating layer alleviate the internal stress concentration between the outer and middle layers of the cathode material particles, further suppressing particle breakage. In summary, through the synergistic effect of the hollow core, the first coating layer, the second coating layer, and the cavity connecting layer in suppressing particle breakage, this lithium manganese iron phosphate material can maintain high capacity performance while mitigating particle breakage, thereby improving the cycle discharge capacity performance of the battery. Attached Figure Description

[0017] 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.

[0018] Figure 1 This is a schematic diagram of the particle structure of the cathode material according to one embodiment of this application; Figure 2 This is a schematic diagram of the structure of an energy storage system according to one embodiment of this application; Figure 3 This is a schematic diagram of the energy storage system according to another embodiment of this application; Figure 4 This is a schematic diagram of the energy storage system according to another embodiment of this application; Figure 5 Here is a SEM image of the surface morphology of the cathode material in Example 1; Figure 6Here is a SEM image of the cross-sectional morphology of the cathode material in Example 1; Figure 7 The image shows the cross-sectional morphology of the cathode material in Comparative Example 1 using SEM. Figure 8 This is a SEM image of the cross-sectional morphology of the cathode material after the 180th cycle test in Comparative Example 1. Figure 9 The diagram shows the ring discharge capacity performance of Example 1 and Comparative Example 1.

[0019] Explanation of reference numerals in the attached drawings: 1-core, 2-first cladding layer, 3-cavity, 4-second cladding layer, 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

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] This application provides a positive electrode sheet, which includes a positive current collector, at least one side of which has a positive electrode material layer, the positive electrode material layer comprising a positive electrode material. (Reference) Figure 1 The cathode material includes a core 1, which has a hollow structure. A first coating layer 2 and a second coating layer 4 are sequentially disposed on the surface of the core 1. The material of the first coating layer 2 is lithium manganese iron phosphate doped with titanium, and the material of the second coating layer 4 is lithium manganese iron phosphate doped with magnesium and / or aluminum. There are multiple cavities 3 between the first coating layer 2 and the second coating layer 4. In the cross-section of the cathode material particles, the multiple cavities 3 surround the first coating layer 2.

[0027] The positive electrode sheet of this application includes the aforementioned positive electrode material, wherein the core has a hollow structure, which can alleviate the internal stress concentration caused by the volume change of the material's crystal structure and suppress the breakage of the positive electrode material particles; a first coating layer and a second coating layer are sequentially disposed on the surface of the core, wherein the material of the first coating layer is titanium (Ti) doped lithium manganese iron phosphate, and the high-valence cations (e.g., Ti) in the first coating layer... 4+The doped material crystal structure improves the electronic conductivity and lithium-ion diffusion rate of lithium manganese iron phosphate. The magnesium and / or aluminum elements in the second coating layer suppress the Jameer-Taylor effect, reducing manganese dissolution and side reactions from direct contact between manganese and the electrolyte, thereby improving the structural stability of the cathode material and reducing particle breakage. The cavities surrounding the first coating layer form a connecting layer for linking the first and second coating layers. These cavities, arranged in a ring, promote electrolyte wetting of the lithium manganese iron phosphate material in the first coating layer, increasing the lithium-ion diffusion rate. Furthermore, the cavities, distributed around the first coating layer, alleviate stress concentration between the outer and middle layers of the cathode material particles, further suppressing particle breakage. In summary, through the synergistic effect of the hollow core, the first coating layer, the second coating layer, and the cavity connecting layer in suppressing particle breakage, this lithium manganese iron phosphate material can maintain high capacity performance while mitigating particle breakage, thereby improving the cycle discharge capacity performance of lithium-ion batteries.

[0028] In one optional embodiment, the area of ​​the hollow structure in the cross-section of the cathode material particles accounts for a proportion of A in the total cross-sectional area, where 10% ≤ A ≤ 40%, preferably 10% ≤ A ≤ 30%. For example, A can be 10%, 13%, 15%, 20%, 23%, 25%, 30%, or 40%. By adjusting the value of A within the above range, the hollow structure can alleviate the internal stress concentration caused by changes in the volume of the material's crystal structure, suppressing the breakage of the cathode material particles. Furthermore, it can prevent the structural stability of the cathode material particles from being affected by an excessively large proportion of the hollow structure's cross-sectional area, thus improving the cycle stability of the cathode material.

[0029] In one optional embodiment, the area of ​​the multiple cavities in the cross-section of the cathode material particles accounts for a percentage (B) of the total cross-sectional area, where 0.5% ≤ B ≤ 6.5%, preferably 0.5% ≤ B ≤ 5%. For example, A can be 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, or 6.5%. By adjusting the value of B within the above range, it is possible to promote the wetting of the electrolyte into the first coating layer of lithium manganese iron phosphate material and alleviate the internal stress concentration between the outer and middle layers of the cathode material particles. Furthermore, it is possible to avoid the structural stability of the cathode material particles being affected by an excessively large proportion of the cavity cross-sectional area, thus improving the cycle stability of the cathode material.

[0030] In one optional embodiment, the Dv50 of the cathode material is D1, where 6μm ≤ D1 ≤ 8μm. For example, D1 can be 6μm, 6.5μm, 7μm, 7.5μm, or 8μm. This allows the cathode material to have a higher compaction density and fully utilize its capacity performance, thereby contributing to the improvement of the capacity performance of lithium-ion batteries.

[0031] 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.

[0032] In one alternative embodiment, the material of the first coating layer has the chemical formula LiMn. x Fe 1-x-y Ti y PO4, 0.5 ≤ x ≤ 0.8, 0.01 ≤ y ≤ 0.05. For example, x can be 0.5, 0.6, 0.7, or 0.8, and y can be 0.01, 0.02, 0.03, 0.04, or 0.05. LiMn x Fe 1-x-y Ti y PO4 is a titanium-doped lithium manganese iron phosphate material, in which titanium can be in the valence state of +4.

[0033] In one alternative embodiment, the material of the second coating layer has the chemical formula LiMn. m Fe 1-m-n M n PO4, where M is magnesium and / or aluminum, 0.5 ≤ m ≤ 0.8, 0.01 ≤ n ≤ 0.05. For example, m can be 0.5, 0.6, 0.7, or 0.8, and n can be 0.01, 0.02, 0.03, 0.04, or 0.05. LiMn m Fe 1-m-n M n PO4 is a lithium iron phosphate material doped with magnesium and / or aluminum.

[0034] In one alternative embodiment, the hollow structure is an ellipsoidal hollow structure or a near-ellipsoidal hollow structure. This structure can more effectively alleviate the internal stress concentration caused by changes in the volume of the material's crystal structure, thereby more effectively suppressing the breakage of the cathode material particles.

[0035] In one alternative embodiment, the cathode material further has a carbon coating layer disposed on the outer surface of the second coating layer, which further improves the conductivity of the cathode material.

[0036] In this application, the length of a single cavity can be 3μm to 7μm. In this way, when multiple cavities form a connecting layer, the internal stress concentration between the outer and middle layers of the cathode material particles can be more effectively relieved, and the structural stability of the cathode material particles can be avoided from being affected by the excessive length of a single cavity.

[0037] In one optional embodiment, the method for preparing the cathode material includes the following steps: Step A: Calcine the carbon microsphere precursor to obtain the first porous hollow carbon microsphere; Step B, according to LiMn x Fe1-x-y Ti y To obtain the required stoichiometric ratio of PO4 (0.5≤x≤0.8, 0.01≤y≤0.05), iron source, manganese source, phosphorus source, lithium source and titanium source are weighed and mixed to obtain the first mixed metal salt. Then, a solvent is added to prepare the first mixed metal salt solution. Step C: Add the first porous hollow carbon microspheres to the first metal salt solution, then place the first metal salt solution, precipitant solution and complexing agent solution in a reaction vessel, maintain the pH value of the reaction liquid at 9±0.5, carry out precipitation and combination reaction, and obtain the first lithium manganese iron phosphate precursor after solid-liquid separation, washing and drying. Step D, according to LiMn m Fe 1-m-n M n To obtain the required stoichiometric ratio of PO4 (0.5≤m≤0.8, 0.01≤n≤0.05), weigh out and mix iron, manganese, phosphorus, lithium, magnesium and / or aluminum sources to obtain a second mixed metal salt, and then add solvent to prepare a second metal salt solution. Step E: Provide a second porous hollow carbon microsphere. Add the first lithium manganese iron phosphate precursor obtained in step C to a second metal salt solution. Then, place the second metal salt solution, the second porous hollow carbon microsphere, the precipitant solution, and the complexing agent solution in a reaction vessel to carry out a precipitation reaction. After solid-liquid separation, washing, and drying, the second lithium manganese iron phosphate precursor is obtained. Step F: Weigh the lithium manganese iron phosphate precursor and carbon source separately and mix them. Use deionized water as a dispersant, then spray dry to form powder. Then sinter the obtained powder and grind and crush it to obtain the cathode material.

[0038] In step A, the carbon microsphere precursor can be obtained by spray drying a sucrose solution, wherein the concentration of the sucrose solution is 1 mol / L to 2 mol / L, the spray drying temperature is 165℃ to 170℃, the calcination temperature is 420℃ to 450℃, and the calcination time is 2h to 4h, so that the sucrose shrinks after heating to form the first porous hollow carbon microspheres. The average particle size of the first porous hollow carbon microspheres is 1.5μm to 6μm, preferably 2μm to 5μm.

[0039] In step B, the iron source can be selected from ferrous oxalate, ferric sulfate, or ferric chloride; the manganese source can be selected from manganese dioxide or manganese sulfate; the phosphorus source can be selected from phosphoric acid or ammonium dihydrogen phosphate; the lithium source can be selected from lithium carbonate or lithium hydroxide; the titanium source can be selected from titanium tetrachloride or titanium oxalate; and the solvent can be water.

[0040] In step C, the amount of the first porous hollow carbon microspheres added is 1% to 2% of the mass of the first mixed metal salt; the precipitant solution can be a sodium hydroxide solution with a concentration of 0.8 mol / L to 1.2 mol / L; the complexing agent solution can be an ammonia solution with a concentration of 0.8 mol / L to 1.2 mol / L; the reaction temperature of the precipitation reaction is 175℃ to 185℃, and the reaction time is 8h to 10h.

[0041] In step D, the iron source can be selected from ferrous oxalate, ferric sulfate, or ferric chloride; the manganese source can be selected from manganese dioxide or manganese sulfate; the phosphorus source can be selected from phosphoric acid or ammonium dihydrogen phosphate; the lithium source can be selected from lithium carbonate or lithium hydroxide; the magnesium source is magnesium oxide; the aluminum source is aluminum hydroxide; and the solvent can be water.

[0042] In step E, the precipitant solution can be a sodium hydroxide solution with a concentration of 0.8 mol / L to 1.2 mol / L; the complexing agent solution can be an ammonia solution with a concentration of 0.8 mol / L to 1.2 mol / L; the reaction temperature of the precipitation reaction is 175℃ to 185℃, and the reaction time is 8 h to 10 h; the second porous hollow carbon microspheres can be obtained commercially, for example, using porous hollow carbon microspheres of model JK-20-001 from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with an average particle size of 250 nm. The mass ratio of the first lithium manganese iron phosphate precursor to the second metal salt in the second metal salt solution can be 3:7; based on the mass of the second metal salt in the second metal salt solution, the mass percentage content of the second porous hollow carbon microspheres is 0.1% to 0.5%.

[0043] In step F, the purpose of adding a carbon source is to form a carbon coating layer, which further improves the conductivity of the cathode material; the carbon source can be glucose; after spray drying, a powder with a certain particle size is formed; the sintering temperature is 650℃~700℃, the sintering time is 5h~10h, and the protective atmosphere is nitrogen.

[0044] This application does not impose any particular limitation on the method for controlling the proportion of the hollow structure area in the total cross-sectional area (i.e., the A value), as long as it achieves the purpose of this application. For example, the A value typically increases with the increase of the average particle size of the first porous hollow carbon microspheres. Based on this, the A value can be controlled by adjusting the average particle size of the first porous hollow carbon microspheres during the preparation of the cathode material. Furthermore, the average particle size of the first porous hollow carbon microspheres typically increases with the increase of the calcination temperature of the carbon microsphere precursor. Based on this, this application can control the average particle size of the first porous hollow carbon microspheres by adjusting the calcination temperature of the carbon microsphere precursor.

[0045] This application does not impose any particular limitation on the method for controlling the proportion of the cavity area in the total cross-sectional area (i.e., the B value), as long as the purpose of this application can be achieved. For example, the B value typically increases with the increase of the amount of the second porous hollow carbon microspheres added. Based on this, the B value can be controlled by adjusting the amount of the second porous hollow carbon microspheres added during the preparation of the cathode material.

[0046] This application also provides a battery including the positive electrode sheet described in any of the above embodiments.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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. 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.

[0060] 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 battery 200 as the 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 battery. 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.

[0061] 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: (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. (2) The energy storage prefabricated cabin applied on the grid side mainly functions as peak regulation, frequency regulation and grid congestion relief. In terms of peak regulation, 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 electricity load period, thereby achieving a balance between power production and consumption. (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.

[0062] 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 2 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.

[0063] 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.

[0064] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 400 according to another embodiment of this application, and this application Figure 3 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.

[0065] 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.

[0066] 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.

[0067] In some embodiments, see Figure 4 , Figure 4 This is a schematic diagram of the structure of an energy storage system 400 according to another embodiment of this application, and this application Figure 4 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] Optionally, the individual cell can be, but is not limited to, at least one of cylindrical, prismatic, prismatic, or other shaped cells.

[0073] 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.

[0074] Example 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.

[0075] Example 1 <Preparation of the positive electrode> <Preparation of cathode materials> A 1.5 mol / L sucrose solution was prepared, and carbon microsphere precursors were obtained by spray drying at 170℃. The carbon microsphere precursors were then calcined at 430℃ for 3 hours to obtain the first porous hollow carbon microspheres. The calcination temperature was 430℃ and the calcination time was 3 hours. The sucrose was heated and shrunk to form the first porous hollow carbon microspheres. The average particle size of the first porous hollow carbon microspheres was 2 μm. According to LiMn 0.5 Fe 0.49 Ti 0.01 To prepare the first mixed metal salt, the required stoichiometric ratio of PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source). Deionized water is then added to prepare the first mixed metal salt solution, wherein the molar concentration of titanium is 2 mol / L. First porous hollow carbon microspheres were added to a first metal salt solution. Then, the first metal salt solution, precipitant solution, and complexing agent solution were placed in a reaction vessel, maintaining the pH of the reaction liquid at 9, to carry out a precipitation reaction. After solid-liquid separation, washing, and drying, the first lithium manganese iron phosphate precursor was obtained. Specifically, the amount of the first porous hollow carbon microspheres added was 1.5% of the mass of the first mixed metal salt; the precipitant solution was a 1 mol / L sodium hydroxide solution; the complexing agent solution was a 1 mol / L ammonia solution; the reaction temperature of the precipitation reaction was 180℃, and the reaction time was 10 h. According to LiMn 0.5 Fe 0.49 Mg 0.01 To obtain the second mixed metal salt, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and magnesium oxide (magnesium source) to prepare a second metal salt solution. A certain amount of the first lithium manganese iron phosphate precursor was weighed and added to the second metal salt solution. Then, the second metal salt solution, the second porous hollow carbon microspheres (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., model JK-20-001, average particle size 250nm), the precipitant solution, and the complexing agent solution were placed in a reaction vessel to carry out a precipitation reaction. After solid-liquid separation, washing, and drying, the second lithium manganese iron phosphate precursor was obtained. The mass ratio of the first lithium manganese iron phosphate precursor to the second metal salt in the second metal salt solution was 3:7; based on the mass of the second metal salt in the second metal salt solution, the mass percentage of the second porous hollow carbon microspheres was 0.1%; the precipitant solution was a 1 mol / L sodium hydroxide solution; the complexing agent solution was a 1 mol / L ammonia solution; the reaction temperature of the precipitation reaction was 180℃, and the reaction time was 10 h. The lithium manganese iron phosphate precursor and glucose were weighed and mixed at a mass ratio of 85:15, with deionized water as a dispersant. The mixture was then spray-dried to form a powder, which was subsequently sintered and ground to obtain the cathode material. The sintering temperature was 680℃, the sintering time was 8 hours, and the protective atmosphere was nitrogen.

[0076] <Preparation of the cathode material layer> The positive electrode material, conductive agent conductive carbon black (Super-P), and binder PVDF are mixed at a mass ratio of 95:2:3. Then, N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode slurry with a solid content of 50wt%. The slurry is stirred evenly and then uniformly coated on one surface of a positive electrode current collector with a thickness of 10μm. The slurry is dried at 85℃. The above steps are repeated on the other surface of the positive electrode sheet. After rolling, a positive electrode sheet with a positive electrode material layer coated on both sides is obtained, with a single-sided thickness of 100μm.

[0077] <Preparation of Negative Electrode Sheets> Artificial graphite, conductive carbon black Super-P, and sodium carboxymethyl cellulose (CMC-Na) were mixed in a mass ratio of 95:2.5:2.5, and deionized water was added to prepare a negative electrode slurry with a solid content of 60 wt%, which was then stirred evenly. The negative electrode slurry was uniformly coated on one surface of a 10 μm thick copper foil current collector and dried at 150 °C. The above steps were then repeated on the other surface of the negative electrode sheet. After rolling, a negative electrode sheet with a negative electrode material layer coated on both sides was obtained, with a single-sided thickness of 70 μm for the negative electrode material layer.

[0078] <Preparation of Electrolyte> Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1, dissolved, and thoroughly stirred. The mixture was then placed at 5°C or lower for 12 hours. Lithium salt LiPF6 was then added, and the mixture was thoroughly mixed to obtain the electrolyte. The molar concentration of LiPF6 in the electrolyte was 1 mol / L.

[0079] <Preparation of the diaphragm> A porous polyethylene (PE) film with a thickness of 16 μm was used as the separator.

[0080] <Lithium-ion battery assembly> The prepared positive and negative electrode sheets are pressed in a press, and then circular positive electrode sheets with a diameter of 15 mm and circular negative electrode sheets with a diameter of 18 mm are cut out using a punch. The circular positive electrode sheets, separator and circular negative electrode sheets are then stacked in sequence, with the separator positioned between the circular positive and circular negative electrode sheets to act as a separator. The prepared electrolyte is then injected to assemble a lithium-ion battery.

[0081] Example 2 Except for the fact that in the "Preparation of Cathode Material", the average particle size of the first porous hollow carbon microspheres is 3 μm by adjusting the calcination temperature and the A value is varied according to Table 1, the rest is the same as in Example 1.

[0082] Example 3 Except for the fact that in the "Preparation of Cathode Material", the average particle size of the first porous hollow carbon microspheres is 4 μm by adjusting the calcination temperature and the A value is varied according to Table 1, the rest is the same as in Example 1.

[0083] Example 4 Except for the fact that in the "Preparation of Cathode Material", the average particle size of the first porous hollow carbon microspheres is 5 μm by adjusting the calcination temperature and the A value changes accordingly as shown in Table 1, the rest is the same as in Example 1.

[0084] Example 5 Except for the fact that in the "Preparation of Cathode Material", the average particle size of the first porous hollow carbon microspheres is 6 μm by adjusting the calcination temperature and the A value changes accordingly as shown in Table 1, the rest is the same as in Example 1.

[0085] Example 6 Except for the fact that in the "Preparation of Cathode Material", the mass percentage of the second porous hollow carbon microspheres is adjusted to 0.2% based on the mass of the second metal salt in the second metal salt solution, and the B value changes accordingly as shown in Table 1, the rest is the same as in Example 1.

[0086] Example 7 Except for the fact that in the "Preparation of Cathode Material", the mass percentage of the second porous hollow carbon microspheres is adjusted to 0.3% based on the mass of the second metal salt in the second metal salt solution, and the B value changes accordingly as shown in Table 1, the rest is the same as in Example 1.

[0087] Example 8 Except for the fact that in the "Preparation of Cathode Material", the mass percentage of the second porous hollow carbon microspheres is adjusted to 0.4% based on the mass of the second metal salt in the second metal salt solution, and the B value changes accordingly as shown in Table 1, the rest is the same as in Example 1.

[0088] Example 9 Except for the fact that in the "Preparation of Cathode Material", the mass percentage of the second porous hollow carbon microspheres is adjusted to 0.5% based on the mass of the second metal salt in the second metal salt solution, and the B value changes accordingly as shown in Table 1, the rest is the same as in Example 1.

[0089] Example 10 Except for the preparation of the cathode material, in which the mass percentage of the second porous hollow carbon microspheres is adjusted to 0.6% based on the mass of the second metal salt in the second metal salt solution, and the B value changes accordingly as shown in Table 1, the rest is the same as in Example 1.

[0090] Example 11 In addition to the preparation of cathode materials, according to LiMn 0.6 Fe 0.39 Ti 0.01 To obtain the first mixed metal salt, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphate (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source), and then, according to LiMn... 0.6 Fe 0.39 Mg 0.01 The required stoichiometric ratio for PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and magnesium oxide (magnesium source) to obtain the second mixed metal salt. Otherwise, it is the same as in Example 1.

[0091] Example 12 In addition to the preparation of cathode materials, according to LiMn 0.7 Fe 0.29 Ti 0.01 To obtain the first mixed metal salt, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphate (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source), and then, according to LiMn... 0.7 Fe 0.29 Mg 0.01The required stoichiometric ratio for PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and magnesium oxide (magnesium source) to obtain the second mixed metal salt. Otherwise, it is the same as in Example 1.

[0092] Example 13 In addition to the preparation of cathode materials, according to LiMn 0.8 Fe 0.19 Ti 0.01 To obtain the first mixed metal salt, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphate (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source), and then, according to LiMn... 0.8 Fe 0.19 Mg 0.01 The required stoichiometric ratio for PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and magnesium oxide (magnesium source) to obtain the second mixed metal salt. Otherwise, it is the same as in Example 1.

[0093] Example 14 In addition to the preparation of cathode materials, according to LiMn 0.5 Fe 0.48 Ti 0.02 To obtain the first mixed metal salt, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphate (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source), and then, according to LiMn... 0.5 Fe 0.48 Mg 0.02 The required stoichiometric ratio for PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and magnesium oxide (magnesium source) to obtain the second mixed metal salt. Otherwise, it is the same as in Example 1.

[0094] Example 15 In addition to the preparation of cathode materials, according to LiMn 0.5 Fe 0.47 Ti 0.03 To obtain the first mixed metal salt, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphate (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source), and then, according to LiMn... 0.5 Fe 0.47 Mg 0.03 The required stoichiometric ratio for PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and magnesium oxide (magnesium source) to obtain the second mixed metal salt. Otherwise, it is the same as in Example 1.

[0095] Example 16 In addition to the preparation of cathode materials, according to LiMn0.5 Fe 0.46 Ti 0.04 To obtain the first mixed metal salt, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphate (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source), and then, according to LiMn... 0.5 Fe 0.47 Mg 0.03 The required stoichiometric ratio for PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and magnesium oxide (magnesium source) to obtain the second mixed metal salt. Otherwise, it is the same as in Example 1.

[0096] Example 17 In addition to the preparation of cathode materials, according to LiMn 0.5 Fe 0.45 Ti 0.05 To obtain the first mixed metal salt, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphate (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source), and then, according to LiMn... 0.5 Fe 0.47 Mg 0.03 The required stoichiometric ratio for PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and magnesium oxide (magnesium source) to obtain the second mixed metal salt. Otherwise, it is the same as in Example 1.

[0097] Example 18 In addition to the preparation of cathode materials, according to LiMn 0.5 Fe 0.49 Al 0.01 The required stoichiometric ratio for PO4 is obtained by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and aluminum hydroxide (aluminum source) to obtain the second mixed metal salt. Otherwise, the process is the same as in Example 1.

[0098] Comparative Example 1 Except for the preparation of the cathode material, which differs from Example 1, everything else is the same as in Example 1.

[0099] The preparation steps of the cathode material are as follows: According to LiMn 0.5 Fe 0.49 Ti 0.01 To prepare a mixed metal salt solution, the required stoichiometric ratio of PO4 is determined by weighing and mixing ferrous oxalate (iron source), manganese dioxide (manganese source), phosphoric acid (phosphorus source), lithium carbonate (lithium source), and titanium tetrachloride (titanium source). Deionized water is then added to prepare the mixed metal salt solution, in which the molar concentration of titanium is 2 mol / L. A metal salt solution, a precipitant solution, and a complexing agent solution were placed in a reaction vessel, and the pH of the reaction liquid was maintained at 9 to carry out a precipitation reaction. After solid-liquid separation, washing, and drying, lithium manganese iron phosphate material was obtained. The amount of porous hollow carbon microspheres added was 1.5% of the mass of the mixed metal salt; the precipitant solution was a 1 mol / L sodium hydroxide solution; the complexing agent solution was a 1 mol / L ammonia solution; the reaction temperature of the precipitation reaction was 180℃, and the reaction time was 10 h. Lithium manganese iron phosphate material and glucose were weighed and mixed at a mass ratio of 85:15, using deionized water as a dispersant, and then spray-dried to form a powder. The resulting powder was then sintered, ground, and crushed to obtain the cathode material. The sintering temperature was 680℃, the sintering time was 8 h, and the protective atmosphere was nitrogen.

[0100] Test methods and equipment: Test of the cross-sectional area ratio of cathode material particles: Positive electrode samples were selected, and the positive electrode sheets were cut using focused ion beam microscopy. The cross-section of the positive electrode sheets was then observed using a scanning electron microscope, and images were taken at 2000x magnification. ImageJ software was used to statistically analyze the cross-sectional areas S1 of the hollow structures of 50 positive electrode material particles, S2 of the hollow cavities in the connecting layers, and S of the entire particle. 总 Then the area ratio A of the hollow structure is [(S1 / S 总 The area ratio B of the cavity is [(S2 / S)] / 100]×100%, which is [(S2 / S)]. 总 ) / 100]×100%, then take the average value.

[0101] Material particle size distribution test: The particle size distribution of the cathode material was measured using a laser diffraction particle size distribution measuring instrument (model: Malvern Mastersizer 3000) according to the particle size distribution laser diffraction method (GB / T19077-2016), thereby measuring the Dv50 of the cathode material.

[0102] Cyclic discharge capacity test: At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were charged to 4.3V at a rate of 0.5C and then discharged to 2.5V at a rate of 0.1C. The cycle discharge capacity of the first cycle and the 180th cycle were recorded, and the difference between the two was calculated. The difference was divided by the discharge capacity of the first cycle to obtain the cycle capacity decay rate.

[0103] Table 1: Relevant performance data of each embodiment and comparative example

[0104] As can be seen from Examples 1 to 18 and Comparative Example 1, the first-cycle discharge capacity and the discharge capacity of Comparative Example 1 are both low, and its cycle capacity decay rate is high. This is because the lithium manganese iron phosphate cathode material of Comparative Example 1 does not have the morphological structure of the lithium manganese iron phosphate cathode material of this application, resulting in poor cycle discharge capacity performance. In contrast, the first-cycle discharge capacity and the discharge capacity of 180 cycles of this application are both high, and the cycle capacity decay rate is lower than or equal to that of Comparative Example 1, indicating better cycle discharge capacity performance.

[0105] Figure 5 Here is a SEM image of the surface morphology of the cathode material in Example 1. Figure 5 It can be seen that the cathode material particles in this application are spherical in shape; Figure 6 This is a SEM image of the cross-sectional morphology of the cathode material in Example 1. Figure 6 It can be seen that the core of the cathode material is a hollow structure, and there are multiple cavities between the first coating layer and the second coating layer, which surround the first coating layer.

[0106] Figure 7 Here is a SEM image of the cross-sectional morphology of the cathode material in Comparative Example 1, from... Figure 7 It can be seen that the cathode material particles in Comparative Example 1 have a solid structure; Figure 8 The SEM image of the cross-sectional morphology of the cathode material after the 180th cycle test in Comparative Example 1 clearly shows particle cracks, which will lead to accelerated degradation of the cycle discharge capacity performance of the lithium battery.

[0107] Figure 9 The diagram shows the ring discharge capacity performance of Example 1 and Comparative Example 1. Figure 9 It can be seen that the lithium-ion battery of this application has better ring discharge capacity performance.

[0108] The above provides a detailed description of a positive electrode, 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 plate, characterized in that, include: A positive current collector, wherein at least one side of the positive current collector has a positive electrode material layer, the positive electrode material layer comprising a positive electrode material; The cathode material includes a core, which has a hollow structure; The surface of the core is sequentially provided with a first coating layer and a second coating layer, wherein the material of the first coating layer is lithium manganese iron phosphate doped with titanium, and the material of the second coating layer is lithium manganese iron phosphate doped with at least one of magnesium or aluminum. There are multiple cavities between the first coating layer and the second coating layer, and in the cross-section of the positive electrode material particles, the multiple cavities surround the first coating layer.

2. The positive electrode sheet according to claim 1, characterized in that, In the cross-section of the positive electrode material particles, the area of ​​the hollow structure accounts for A% of the total cross-sectional area, where 10% ≤ A ≤ 40%.

3. The positive electrode sheet according to claim 1, characterized in that, In the cross-section of the positive electrode material particles, the area of ​​the plurality of cavities accounts for B of the total area of ​​the cross-section, where 0.5% ≤ B ≤ 5%.

4. The positive electrode sheet according to claim 1, characterized in that, The Dv50 of the cathode material is D1, where 6μm≤D1≤8μm.

5. The positive electrode sheet according to claim 1, characterized in that, The material of the first coating layer has the chemical formula LiMn x Fe 1-x-y Ti y PO4, 0.5≤x≤0.8, 0.01≤y≤0.

05.

6. The positive electrode sheet according to claim 1, characterized in that, The material of the second coating layer has the chemical formula LiMn m Fe 1-m-n M n PO4, M is magnesium and / or aluminum, 0.5≤m≤0.8, 0.01≤n≤0.

05.

7. The positive electrode sheet according to claim 1, characterized in that, The hollow structure is an ellipsoidal hollow structure or a near-ellipsoidal hollow structure.

8. The positive electrode sheet according to claim 1, characterized in that, The cathode material also has a carbon coating layer.

9. A battery, characterized in that, Includes the positive electrode sheet as described in any one of claims 1 to 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