Positive electrode sheet, battery, energy storage device, and electric device

Abstract

The application provides a positive electrode sheet, a battery, an energy storage device and an electric equipment, wherein the positive electrode sheet comprises a positive electrode current collector, at least one side of the positive electrode current collector is provided with a positive electrode material layer, the positive electrode material layer comprises a first positive electrode material and a second positive electrode material; the Dv50 of the first positive electrode material is 800 nm to 1000 nm; the second positive electrode material comprises spherical particles and rod-shaped particles; the Dv50 of the spherical particles is 300 nm to 500 nm; the average length of the rod-shaped particles is 2 mu m to 6 mu m; and the second positive electrode material comprises vanadium elements.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a positive electrode, a battery, an energy storage device, and an electrical device. Background Technology

[0002] Lithium-ion batteries are characterized by 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-ion batteries based on lithium iron phosphate (LFP) cathode materials have the advantages of high safety and stability. With the increasing demands for battery capacity in energy storage applications, smaller particle size LFP materials are commonly used. However, this leads to increased elongation of the cathode sheet during rolling. Yet, simply increasing the particle size of the LFP material results in a decrease in battery capacity. Therefore, balancing battery capacity performance while reducing cathode sheet elongation has become a pressing technical problem. Summary of the Invention

[0004] To address the aforementioned technical problems, this application discloses a positive electrode sheet, a battery, an energy storage device, and an electrical appliance that balances the battery's capacity performance while reducing the elongation of the positive electrode sheet.

[0005] In a first aspect, this application provides a positive electrode sheet, including a positive current collector, at least one side of which has a positive electrode material layer, the positive electrode material layer including a first positive electrode material and a second positive electrode material; the first positive electrode material has a Dv50 of 800nm ​​to 1000nm, the second positive electrode material includes spherical particles and rod-shaped particles, the spherical particles have a Dv50 of 300nm to 500nm, the rod-shaped particles have an average length of 2μm to 6μm, and the second positive electrode material includes vanadium.

[0006] In some embodiments of this application, based on the mass of the cathode material layer, the mass percentage of the first cathode material is 90% to 93%, and the mass percentage of the second cathode material is 2% to 5%.

[0007] In some embodiments of this application, the first cathode material has the chemical formula LiFe x Ti y PO4 / C, where x+y=1 and 0 <y≤0.03。

[0008] In some embodiments of this application, the second cathode material has the chemical formula LiFe x Ti y V zPO4 / C, where x+y+Z=1 and 0 <y≤0.03,0<z≤0.03。

[0009] In some embodiments of this application, the elongation of the positive electrode sheet is 0.8% to 2.3%.

[0010] In some embodiments of this application, the coin cell containing the positive electrode has a 0.5C discharge capacity of 140mAh / g to 150mAh / g and a 1C discharge capacity of 128mAh / g to 137mAh / g.

[0011] In some embodiments of this application, the compaction density of the mixture of the first cathode material and the second cathode material is 2.3 g / cm³. 3 ~2.5g / cm 3 .

[0012] In some embodiments of this application, the positive electrode further includes a conductive agent and a binder, wherein the mass percentage of the conductive agent is 1% to 3% and the mass percentage of the binder is 1% to 3% based on the mass of the positive electrode material 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:

[0017] 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. The positive electrode material layer includes a first positive electrode material and a second positive electrode material. The first positive electrode material has a Dv50 of 800 nm to 1000 nm. The second positive electrode material includes spherical particles and rod-shaped particles. The spherical particles have a Dv50 of 300 nm to 500 nm, and the rod-shaped particles have an average length of 2 μm to 6 μm. The second positive electrode material includes vanadium. The positive electrode sheet of this application includes the aforementioned first and second positive electrode materials. The first positive electrode material is mainly used to provide capacity. In the second positive electrode material, the rod-shaped particles can hinder particle displacement deformation during rolling, thereby reducing the elongation of the positive electrode sheet. The spherical particles have a smaller particle size and are used to fill the gaps in the first positive electrode material to further improve capacity. Furthermore, the vanadium in the second positive electrode material can slow down the decrease in capacity. The combined effect of the first and second cathode materials can balance the battery's capacity performance while reducing the elongation of the cathode sheet. Attached Figure Description

[0018] 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.

[0019] Figure 1 This is a schematic diagram of the structure of a residential energy storage system according to one embodiment of this application;

[0020] Figure 2 This is a schematic diagram of the structure of an energy storage system according to one embodiment of this application;

[0021] Figure 3 This is a schematic diagram of the positive electrode sheet elongation test;

[0022] Figure 4 This is a scanning electron microscope (SEM) image of the first cathode material prepared in Example 1;

[0023] Figure 5 Here is a SEM image of the second cathode material prepared in Example 1;

[0024] Figure 6 This is a cross-sectional SEM image of the positive electrode sheet of Example 1.

[0025] Explanation of reference numerals in the attached drawings: 1-Energy storage device, 2-Electric power conversion device, 3-First user load, 4-Second user load, 10-Positive current collector, 20-Positive electrode material layer, 30-Roller, 400-Energy storage system, 410-High voltage cable, 420-First electric power conversion device, 430-Second electric power conversion device. Detailed Implementation

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (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, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0031] It should be noted that this application uses lithium-ion batteries as an example to explain the application, but the batteries in this application are not limited to lithium-ion batteries.

[0032] This application provides a positive electrode sheet, including a positive current collector. At least one side of the positive current collector has a positive electrode material layer, which includes a first positive electrode material and a second positive electrode material. The first positive electrode material has a Dv50 of 800 nm to 1000 nm, and the second positive electrode material includes spherical particles and rod-shaped particles. The spherical particles have a Dv50 of 300 nm to 500 nm, and the rod-shaped particles have an average length of 2 μm to 6 μm. The second positive electrode material includes vanadium. For example, the first positive electrode material has a Dv50 of 800 nm, 850 nm, 900 nm, or 1000 nm, the spherical particles have a Dv50 of 300 nm, 320 nm, 350 nm, or 500 nm, and the rod-shaped particles have an average length of 2 μm, 3 μm, 5 μm, or 6 μm.

[0033] 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.

[0034] The positive electrode sheet of this application includes the aforementioned first positive electrode material and second positive electrode material. The first positive electrode material primarily provides capacity. The rod-shaped particles in the second positive electrode material impede particle displacement and deformation during rolling, thereby reducing the elongation of the positive electrode sheet. The spherical particles in the second positive electrode material have a smaller particle size, filling the gaps in the first positive electrode material to further improve capacity. Furthermore, the vanadium element in the second positive electrode material slows down the capacity decrease. Through the combined action of the first and second positive electrode materials, the capacity performance of the lithium-ion battery can be balanced while reducing the elongation of the positive electrode sheet.

[0035] In one optional embodiment, based on the mass of the cathode material layer, the mass percentage of the first cathode material is 90% to 93%, and the mass percentage of the second cathode material is 2% to 5%. For example, the mass percentage of the first cathode material is 90%, 91%, 92%, or 93%, and the mass percentage of the second cathode material is 2%, 3%, 4%, or 5%. By adjusting the contents of the first and second cathode materials within the above ranges, the first cathode material is mainly used to provide capacity, which is beneficial to balancing the capacity performance of the lithium-ion battery while reducing the elongation of the cathode sheet, and the second cathode material is used to reduce the elongation of the cathode sheet. In this way, the capacity performance of the lithium-ion battery can be balanced while reducing the elongation of the cathode sheet.

[0036] In one alternative embodiment, the first cathode material has the chemical formula LiFe. x Ti yPO4 / C, where x + y = 1, and 0 < y ≤ 0.03. For example, y = 0.01, 0.02 or 0.03. The first positive electrode material with the above chemical formula can provide capacity, which is beneficial to improving the capacity performance of the lithium-ion battery.

[0037] In an optional embodiment, the second positive electrode material has the chemical formula LiFe x Ti y V z PO4 / C, where x + y + Z = 1, and 0 < y ≤ 0.03, 0 < z ≤ 0.03. For example, y = 0.01, 0.02 or 0.03, z = 0.01, 0.02 or 0.03. The second positive electrode material with the above chemical formula can form rod-shaped particles and spherical particles. The rod-shaped particles can hinder the displacement and deformation of the particles during rolling, thereby reducing the elongation rate of the positive electrode sheet. The spherical particles can fill the gaps of the first positive electrode material to further improve the capacity. The vanadium element can slow down the decline of the capacity.

[0038] In an optional embodiment, the elongation rate of the positive electrode sheet is 0.8% - 2.3%. For example, the elongation rate is 0.8%, 1%, 1.5%, 2% or 2.3%. Having a smaller elongation rate is beneficial to reducing the risk of edge cracking of the positive electrode sheet.

[0039] In an optional embodiment, the 0.5C discharge capacity of the button cell containing the positive electrode sheet is 140 mAh / g - 150 mAh / g, and the 1C discharge capacity is 128 mAh / g - 137 mAh / g. For example, the 0.5C discharge capacity is 140 mAh / g, 143 mAh / g, 145 mAh / g or 150 mAh / g, and the 1C discharge capacity is 128 mAh / g, 132 mAh / g, 135 mAh / g or 137 mAh / g. Having a higher discharge capacity is beneficial to improving the capacity performance of the lithium-ion battery.

[0040] In an optional embodiment, the tap density of the mixture of the first positive electrode material and the second positive electrode material is 2.3 g / cm 3 ~2.5 g / cm 3 , for example, the tap density is 2.3 g / cm 3 , 2.4 g / cm 3 or 2.5 g / cm 3 . By regulating the tap density of the positive electrode material layer within the above range, it is beneficial to improving the capacity performance of the lithium-ion battery.

[0041] In one optional embodiment, the positive electrode further includes a conductive agent and a binder. Based on the mass of the positive electrode material layer, the conductive agent has a mass percentage content of 1% to 3%, and the binder has a mass percentage content of 1% to 3%. For example, the conductive agent may have a mass percentage content of 1%, 2%, 2.5%, or 3%, and the binder may have a mass percentage content of 1%, 2%, 2.5%, or 3%. This application does not impose any particular limitation on the types of conductive agents and binders. For example, conductive agents include, but are not limited to, conductive carbon black, carbon nanotubes, graphene, etc., and binders include, but are not limited to, at least one of polyvinylidene fluoride (PVDF), fluorinated resins, polypropylene resins, fiber-type binders, rubber-type binders, and polyimide-type binders.

[0042] In one optional embodiment, the method for preparing the first cathode material includes the following steps:

[0043] Step A, according to LiFe x Ti y To obtain the required stoichiometric ratio for PO4 / C (x+y=1, y≤0.03), weigh out the iron source, phosphorus source, lithium source, carbon source and titanium source, mix them uniformly in a ball mill, add pure water as a dispersant, and then perform high-energy ball milling.

[0044] Step B: Spray dry the material after high-energy ball milling to form powder;

[0045] Step C: The powder formed after spray drying is placed in a vacuum atmosphere sintering furnace for high-temperature calcination, and then ball-milled to obtain the first cathode material.

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

[0047] In step B, the spray drying pump speed is 8 mL / min to 12 mL / min, the drying temperature is 180℃ to 220℃, and the resulting powder is granular.

[0048] In step C, the protective atmosphere is nitrogen, the sintering temperature is 650℃~750℃, and the sintering time is 5h~10h.

[0049] In one optional embodiment, the method for preparing the second cathode material includes the following steps:

[0050] Step a, according to LiFe x Ti y Vz Weigh the iron source, phosphorus source, carbon source, titanium source and vanadium source according to the stoichiometric ratio required in PO4 / C(x + y + Z = 1, and 0 < y ≤ 0.03, 0 < z ≤ 0.03), and mix them to obtain a mixed metal salt solution; then prepare a strong base solution as the precipitant solution and ammonia water as the complexing agent solution.

[0051] Step b: Place the above-prepared mixed metal salt solution, complexing agent solution and precipitant solution in a reaction kettle, stir continuously, keep the pH value of the reaction liquid at 9 ± 0.5, the reaction temperature at 190 °C - 200 °C, and the reaction duration at 8 h - 10 h, and synthesize by precipitation reaction. After solid-liquid separation, washing and drying, the first precursor material is obtained.

[0052] Step b': Place the above-prepared mixed metal salt solution, complexing agent solution and precipitant in a reaction kettle, stir continuously, keep the pH value of the reaction liquid at 9 ± 0.5, the reaction temperature at 150 °C - 160 °C, and the reaction duration at 5 h - 7 h, and synthesize by precipitation reaction. After solid-liquid separation, washing and drying, the second precursor material is obtained.

[0053] Step c: Mix the prepared first precursor material and second precursor material according to a mass ratio of 8 - 10:1 to obtain a mixed precursor material.

[0054] Step d: According to the stoichiometric ratio required in LiFe x Ti y V z PO4 / C(x + y + Z = 1, and 0 < y ≤ 0.03, 0 < z ≤ 0.03), weigh the lithium source, mix the lithium source with the mixed precursor material evenly, put it into a vacuum atmosphere sintering furnace for calcination, and obtain the second cathode material after crushing treatment.

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

[0056] In step b or b', a complexing agent can be added to the mixed metal salt solution first to adjust the pH to 9±0.5, and then a precipitant solution can be added. As the precipitate forms, the complexing agent is added again to adjust the pH to maintain at 9±0.5. This process is a precipitation reaction process.

[0057] In step d, the lithium source can be selected from lithium carbonate or lithium hydroxide; the protective atmosphere is nitrogen, the sintering temperature is 500℃~600℃, and the sintering time is 5h~10h.

[0058] This application also provides a battery including the positive electrode sheet described in any of the above embodiments.

[0059] 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. The positive electrode material layer is disposed on the surface of the positive electrode current collector, meaning it can be disposed on a portion or the entire surface of one surface. 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 12 μm is acceptable. The single-sided thickness of the positive electrode material layer in this application can be 8 μm to 15 μm.

[0060] 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, the thickness can be 4μm to 12μm. The single-sided thickness of the negative electrode material layer in this application can be 70μm to 200μm.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] The battery of this application also includes an electrolyte. This application does not impose any particular limitation 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), 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, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, lithium dioxalatoborate (LiBOB), or lithium difluoroborate. 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The electrical equipment covered by this application may include, but is not limited to: containers, household energy storage systems, 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.

[0070] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a residential energy storage system according to one embodiment of this application, and this application... Figure 1 The implementation plan is illustrated using the residential energy storage scenario in user-side energy storage as an example. The energy storage device in this application is not limited to the residential energy storage scenario.

[0071] This application provides a residential energy storage system, which includes a power conversion device 2 (photovoltaic panel), a first user load 3 (streetlight), a second user load 4 (e.g., household appliances such as air conditioners), and an energy storage device 1. The energy storage device 1 is a small energy storage box that can be wall-mounted to an outdoor wall. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 1 is used to store this electrical energy and supply it to streetlights and household appliances during periods of high electricity prices, or to provide power during power outages / power failures.

[0072] Please see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 400 according to one embodiment of this application, and this application Figure 2 The implementation plan is illustrated using the shared energy storage scenario on the power generation / distribution side as an example. The energy storage device 1 in this application is not limited to the power generation / distribution side energy storage scenario.

[0073] This application provides an energy storage system 400, which includes a high-voltage cable 410, a first power conversion device 420, a second power conversion device 430, and the energy storage device 1 provided in this application. During power generation, the first power conversion device 420 and the second power conversion device 430 convert other forms of energy into electrical energy, which is then connected to the high-voltage cable 410 and supplied to the power consumption side of the distribution network. When the power load is low and the first power conversion device 420 and the second power conversion device 430 generate excess power, the excess power is stored in the energy storage device 1, reducing wind and solar curtailment rates and improving the absorption of new energy power generation. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 1, along with the high-voltage cable 410, in a grid-connected mode to supply power to the power consumption side. This provides various services such as peak shaving, frequency regulation, and backup for the power grid operation, fully leveraging the peak shaving function of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure on the power grid.

[0074] Optionally, the first power conversion device 420 and the second power conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electrical energy.

[0075] The number of energy storage devices 1 can be multiple, and these devices can be connected in series or in parallel. The multiple energy storage devices 1 are supported and electrically connected by an isolation plate (not shown). In this embodiment, "multiple" refers to two or more. An energy storage box can also be provided outside the energy storage device 1 to house it.

[0076] Optionally, the energy storage device 1 may include, but is not limited to, battery modules, battery packs, and battery systems. Specifically, a battery module may be formed by connecting multiple batteries of this application in series or parallel; a battery pack may include multiple batteries of this application; and a battery system may be a charging and discharging system including the batteries or battery pack of this application.

[0077] The actual application form of the energy storage device 1 provided in this application embodiment can be, but is not limited to, the listed products, and can also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 1. This application embodiment only uses a multi-cell battery as an example for illustration. When the energy storage device 1 is a single cell battery, the energy storage device 1 can be at least one of cylindrical batteries, prismatic batteries, etc.

[0078] Example

[0079] 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.

[0080] Example 1

[0081] <Preparation of the positive electrode>

[0082] <Preparation of the First Cathode Material>

[0083] According to LiFe 0.99 Ti 0.01 To achieve the required stoichiometric ratio for PO4 / C, ferrous oxalate (iron source), lithium dihydrogen phosphate (phosphorus source), lithium carbonate (lithium source), glucose (carbon source), and titanium tetrachloride (titanium source) were weighed out and uniformly mixed in a ball mill. Pure water was then added as a dispersant, followed by high-energy ball milling. The ball-to-material ratio for high-energy ball milling was 4:1, the rotation speed was 1300 r / min, and the milling time was 20 h. The milled material was then spray-dried at a pump speed of 10 mL / min and a drying temperature of 200 °C to form powder. The spray-dried powder was then placed in a vacuum atmosphere sintering furnace for high-temperature calcination at 700 °C under a nitrogen atmosphere for 8 h. After crushing, the first cathode material was obtained. The Dv50 of the first cathode material is shown in Table 1.

[0084] <Preparation of the Second Cathode Material>

[0085] <Solution Preparation>

[0086] According to LiFe 0.98 Ti 0.01 V 0.01To obtain a mixed metal salt solution, the required stoichiometric ratio for PO4 / C is achieved by weighing and mixing ferrous oxalate (iron source), phosphoric acid (phosphorus source), glucose (carbon source), titanium tetrachloride (titanium source), and vanadium pentoxide (vanadium source). A strong alkaline solution is then prepared as a precipitant, and ammonia is prepared as a complexing agent. The molar concentration of titanium or vanadium in the mixed metal salt solution is 4 mol / L, the strong alkaline solution is a 0.5 mol / L sodium hydroxide solution, and the ammonia solution has a molar concentration of 1 mol / L.

[0087] <Preparation of the First Precursor Material>

[0088] The mixed metal salt solution, complexing agent solution and precipitant solution prepared above were placed in a reaction vessel and stirred continuously. The pH value of the reaction liquid was kept at 9, the reaction temperature was 200℃, and the reaction time was 10h. The first precursor material was obtained by using precipitation combination reaction to synthesize the material. After solid-liquid separation, washing and drying, the material was obtained.

[0089] <Preparation of Second Precursor Materials>

[0090] The mixed metal salt solution, complexing agent solution and precipitant solution prepared above were placed in a reaction vessel and stirred continuously. The pH value of the reaction liquid was kept at 9, the reaction temperature was 160℃, and the reaction time was 7h. The second precursor material was obtained by using precipitation combination reaction to synthesize the material. After solid-liquid separation, washing and drying, the material was obtained.

[0091] The first precursor material and the second precursor material were mixed at a mass ratio of 9:1 to obtain a mixed precursor material; according to LiFe 0.98 Ti 0.01 V 0.01 The required stoichiometric ratio of lithium carbonate source in PO4 / C was determined by weighing lithium source and mixing it with the mixed precursor material. The mixture was then placed in a vacuum atmosphere sintering furnace for calcination. The protective atmosphere was nitrogen, the sintering temperature was 550℃, and the sintering time was 10h. After crushing, the second cathode material was obtained. The Dv50 of the spherical particles and the average length of the rod-shaped particles in the second cathode material are shown in Table 1.

[0092] <Preparation of the cathode material layer>

[0093] The first positive electrode material, the second positive electrode material, conductive carbon black (Super-P) and binder PVDF were mixed in a mass ratio of 93:2:2:3. Then, N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode slurry with a solid content of 50wt%, and stirred evenly. The positive electrode slurry was then uniformly coated on one surface of a positive electrode current collector with a thickness of 10μm and dried at 85℃. The above steps were 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 was obtained, with a single-sided thickness of 100μm.

[0094] <Preparation of Negative Electrode Sheets>

[0095] 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 85 °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.

[0096] <Preparation of Electrolyte>

[0097] 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.

[0098] <Preparation of the diaphragm>

[0099] A porous polyethylene (PE) membrane with a thickness of 16 μm was used as the separator.

[0100] <Lithium-ion battery assembly>

[0101] 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.

[0102] Example 2

[0103] In addition to the preparation of the first cathode material, according to LiFe 0.98Ti 0.02 Except for the weighing of each raw material, the required stoichiometric ratio for PO4 / C is the same as in Example 1.

[0104] Example 3

[0105] In addition to the preparation of the first cathode material, according to LiFe 0.97 Ti 0.03 Except for the weighing of each raw material, the required stoichiometric ratio for PO4 / C is the same as in Example 1.

[0106] Example 4

[0107] In addition to the preparation of the second cathode material, according to LiFe 0.97 Ti 0.01 V 0.02 Except for the weighing of each raw material, the required stoichiometric ratio for PO4 / C is the same as in Example 1.

[0108] Example 5

[0109] In addition to the preparation of the second cathode material, according to LiFe 0.96 Ti 0.01 V 0.03 Except for the weighing of each raw material, the required stoichiometric ratio for PO4 / C is the same as in Example 1.

[0110] Example 6

[0111] In addition to the preparation of the second cathode material, according to LiFe 0.97 Ti 0.02 V 0.01 Except for the weighing of each raw material, the required stoichiometric ratio for PO4 / C is the same as in Example 1.

[0112] Example 7

[0113] In addition to the preparation of the second cathode material, according to LiFe 0.96 Ti 0.03 V 0.01 Except for the weighing of each raw material, the required stoichiometric ratio for PO4 / C is the same as in Example 1.

[0114] Examples 8 to 11

[0115] Except for adjusting the reaction temperature and reaction time according to Table 1 in the <Preparation of Second Cathode Material>, the rest is the same as in Example 1.

[0116] Examples 12 to 14

[0117] Except for adjusting the content of the first and second cathode materials in the cathode material layer according to Table 2 in the <Preparation of Cathode Material Layer>, the rest is the same as in Example 1.

[0118] Comparative Example 1

[0119] Except for the fact that in the <Preparation of the Positive Electrode Material Layer>, the positive electrode material layer contains only the first positive electrode material and not the second positive electrode material, the rest is the same as in Example 1.

[0120] Comparative Example 2

[0121] In addition to the preparation of the second cathode material, according to LiFe 0.98 Ti 0.01 The required stoichiometric ratio of each raw material in PO4 / C is weighed out, except that the second cathode material does not contain vanadium, otherwise it is the same as in Example 1.

[0122] Table 1. Relevant preparation parameters for Examples 1-11 and Comparative Examples 1-2

[0123]

[0124]

[0125] In Table 1, " / " indicates that no relevant preparation parameters exist.

[0126] Table 2. Relevant preparation parameters of the cathode material layer in Examples 1, 12-14, and Comparative Examples 1-2.

[0127]

[0128] Test methods and equipment:

[0129] Material particle size distribution test:

[0130] Using a laser diffraction particle size distribution measuring instrument (Malvern Mastersizer 3000), and in accordance with the particle size distribution laser diffraction method (GB / T19077-2016), the particle size distribution of spherical and rod-shaped particles in the first and second cathode materials was measured, thereby measuring the Dv50 of the first cathode material, the Dv50 of the spherical particles, and the average length of the rod-shaped particles.

[0131] Average length test of rod-shaped particles in the second cathode material:

[0132] One hundred rod-shaped particles were randomly selected from the SEM image of the cathode material layer. The length of each rod-shaped particle was measured, and the average length of the 100 rod-shaped particles was calculated as the average length of the rod-shaped particles in the second cathode material.

[0133] Positive electrode sheet elongation test:

[0134] like Figure 3 As shown, the positive electrode sheet includes a positive current collector 10 and a double-coated positive electrode material layer 20. Taking the positive electrode sheets prepared in each embodiment and comparative example, points A and B are marked on the surface of the positive electrode material layer 20 before rolling. L1 is the distance between points A and B before rolling. After rolling by the roller 30, the positive electrode sheet extends along its length, thus lengthening the distance between points A and B, i.e., the distance from A' to B', denoted as L2. The electrode sheet elongation rate is calculated as S = (L2 - L1) / L1 × 100%.

[0135] Compacted density test:

[0136] Using a powder compaction tester (model LD43.305) from Shanghai Lisheng Company, the first cathode material and the second cathode material were mixed to obtain a sample according to the standard method GBT 24533-2019, and then the compaction density of the sample under a pressure of 3kN was measured.

[0137] Ratio performance test:

[0138] At 25°C, the lithium-ion batteries prepared in each example and comparative example were charged to 3.75V at a rate of 0.5C, and then discharged to 2.5V at a rate of 0.5C. The discharge capacity at this time was recorded. Then, the batteries were charged to 3.75V at 1C, and then discharged to 2.5V at a rate of 1C. The discharge capacity at this time was recorded. The units are mAh / g.

[0139] Table 3 Performance data of Examples 1-14 and Comparative Examples 1-2

[0140]

[0141]

[0142] As can be seen from Examples 1 and Comparative Examples 1-2, Comparative Example 1 has a larger elongation of its positive electrode sheet because it does not contain a second positive electrode material. The positive electrode sheet of Example 1 has a smaller elongation, which may be because the rod-shaped particles in the second positive electrode material can hinder particle displacement deformation during rolling, thus exhibiting a smaller elongation. Since the second positive electrode material of Comparative Example 2 does not contain the dopant element vanadium, its elongation is the same as that of Example 1, but its capacity performance is reduced. Compared with Comparative Example 1, Example 1 only shows a 1.2% decrease in 0.5C discharge capacity and a 2.2% decrease in 1C discharge capacity, with no significant impact on capacity performance. Example 1 and Comparative Example 2 show further improved capacity performance while maintaining the same elongation. It is evident that the combined effect of the first and second positive electrode materials can balance the capacity performance of lithium-ion batteries while reducing the elongation of the positive electrode sheet.

[0143] The content of each raw material in the first cathode material and the Dv50 of the first cathode material also typically affect the performance of the cathode electrode. As can be seen from Examples 1 to 3, by adjusting the above-mentioned preparation parameters within the range of this application, it is beneficial to obtain a lithium-ion battery with low elongation and high capacity performance, based on the cathode electrode having the first cathode material and the second cathode material of this application.

[0144] The content of each raw material in the second cathode material, the reaction temperature, the reaction time, the average length of the rod-shaped particles, and the Dv50 of the spherical particles also typically affect the performance of the cathode sheet. As can be seen from Examples 4 to 11, by adjusting the above-mentioned preparation parameters within the scope of this application, based on the cathode sheet having the first and second cathode materials of this application, it is beneficial to obtain a lithium-ion battery with low elongation and high capacity performance.

[0145] The content of the first and second positive electrode materials in the positive electrode material layer also typically affects the performance of the positive electrode sheet. As can be seen from Examples 1, 12 to 14, by adjusting the preparation parameters within the range of this application, it is beneficial to obtain a lithium-ion battery with low elongation and high capacity performance, based on the presence of the first and second positive electrode materials in the positive electrode sheet.

[0146] Figure 4 The image shows a SEM image of the first cathode material prepared in Example 1. Figure 4 It can be seen that the first cathode material has relatively large particles, a relatively uniform particle size distribution, and a smooth and spherical surface morphology. Figure 5 The image shows a SEM image of the second cathode material prepared in Example 1. Figure 5 It can be seen that it contains spherical particles and rod-shaped particles, among which the spherical particles are smaller in size; Figure 6This is a cross-sectional SEM image of the positive electrode material layer in Example 1. Figure 6 It can be seen that the cathode material layer contains rod-shaped particles.

[0147] The above provides a detailed description of a positive electrode sheet, battery, energy storage device, and electrical equipment 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, It includes a positive current collector, at least one side of which has a positive electrode material layer, the positive electrode material layer including a first positive electrode material and a second positive electrode material; The first cathode material has a Dv50 of 800nm~1000nm, the second cathode material includes spherical particles and rod-shaped particles, the spherical particles have a Dv50 of 300nm~500nm, the rod-shaped particles have an average length of 2μm~6μm, the second cathode material includes vanadium, and both the first cathode material and the second cathode material are lithium iron phosphate materials.

2. The positive electrode sheet according to claim 1, characterized in that, Based on the mass of the cathode material layer, the mass percentage of the first cathode material is 90% to 93%, and the mass percentage of the second cathode material is 2% to 5%.

3. The positive electrode sheet according to claim 1, characterized in that, The first cathode material has the chemical formula LiFe x Ti y PO4 / C, where x+y=1 and 0 <y≤0.03。 4. The positive electrode sheet according to claim 1, characterized in that, The second cathode material has the chemical formula LiFe x Ti y V z PO4 / C, where x+y+Z=1 and 0 <y≤0.03,0<z≤0.03。 5. The positive electrode sheet according to claim 1, characterized in that, The elongation of the positive electrode sheet is 0.8% to 2.3%.

6. The positive electrode sheet according to claim 1, characterized in that, The coin cell containing the positive electrode has a 0.5C discharge capacity of 140 mAh / g to 150 mAh / g and a 1C discharge capacity of 128 mAh / g to 137 mAh / g.

7. The positive electrode sheet according to claim 1, characterized in that, The compaction density of the mixture of the first cathode material and the second cathode material is 2.3 g / cm³. 3 ~2.5 g / cm 3 .

8. The positive electrode sheet according to claim 1, characterized in that, The positive electrode sheet also includes a conductive agent and a binder. Based on the mass of the positive electrode material layer, the mass percentage of the conductive agent is 1% to 3%, and the mass percentage of the binder is 1% to 3%.

9. A battery, characterized in that, Includes the positive electrode sheet as described in any one of claims 1 to 7.

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.

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