Positive electrode sheet, preparation method of PCM / ceramic composite material and battery

Abstract

This application provides a positive electrode sheet, a method for preparing a PCM / ceramic composite material, and a battery. The positive electrode sheet includes a positive current collector, which includes a first region with a positive active material and a second region without a positive active material. The second region has an insulating layer, which includes a PCM / ceramic composite material. The PCM / ceramic composite material is composed of a phase change composite material and a ceramic material. The phase change composite material is composed of SnBi58 and TiO2. Based on the mass of the PCM / ceramic composite material, the mass percentage of the phase change composite material is 30% to 50%, and the mass percentage of the ceramic material is 50% to 70%.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a method for preparing a positive electrode, a PCM / ceramic composite material, and a battery. Background Technology

[0002] 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] The positive electrode in a lithium-ion battery typically includes a positive current collector, a positive active material layer, and an insulating layer. For energy storage applications, the requirements for thermal safety performance are even more stringent. However, existing insulating layers are mainly used to improve the burr problem during the manufacturing process of the positive electrode to reduce the risk of short circuits under normal operating conditions, without considering the safety performance of lithium-ion batteries in the event of thermal runaway. Therefore, it is difficult to guarantee the thermal safety performance of lithium-ion batteries in energy storage scenarios. Summary of the Invention

[0004] To address the aforementioned technical issues, this application discloses a method for preparing a positive electrode sheet, a PCM / ceramic composite material, and a battery, in order to improve the thermal safety performance of lithium-ion batteries in energy storage scenarios.

[0005] In a first aspect, this application provides a positive electrode sheet, including a positive current collector, the positive current collector including a first region disposed of a positive active material and a second region not disposed of the positive active material; the second region is provided with an insulating layer, the insulating layer including a PCM / ceramic composite material, the PCM / ceramic composite material being composed of a phase change composite material and a ceramic material, the phase change composite material being composed of SnBi58 and TiO2; based on the mass of the PCM / ceramic composite material, the mass percentage content of the phase change composite material is 30% to 50%, and the mass percentage content of the ceramic material is 50% to 70%.

[0006] In some embodiments of this application, the phase transition temperature range of the PCM / ceramic composite material is 130°C to 150°C.

[0007] In some embodiments of this application, the latent heat of the PCM / ceramic composite material is 30 J / g to 40 J / g.

[0008] In some embodiments of this application, the thickness of the insulating layer on one side is 5 μm to 25 μm.

[0009] In some embodiments of this application, the ceramic material includes at least one of boehmite and alumina.

[0010] Secondly, this application provides a method for preparing a PCM / ceramic composite material, comprising the following steps:

[0011] A mixture of phase change composite material and ceramic material is compacted to obtain a PCM / ceramic composite material precursor. Based on the mass of the PCM / ceramic composite material precursor, the mass percentage of the phase change composite material is 30% to 50%, and the mass percentage of the ceramic material is 50% to 70%.

[0012] The PCM / ceramic composite material precursor is heated to 80℃~120℃ and subjected to a first heat preservation treatment for 0.5h~1.5h.

[0013] The PCM / ceramic composite material precursor after the first heat preservation treatment is first heated to 390℃~410℃, then heated to 440℃~460℃, and subjected to a second heat preservation treatment for 0.5h~1.5h to obtain the PCM / ceramic composite material.

[0014] In some embodiments of this application, the compaction pressure is 3 MPa to 8 MPa.

[0015] In some embodiments of this application, the preparation process of the mixture of phase change composite material and ceramic material includes:

[0016] The phase change composite material and the ceramic material are mixed and then added to a polyvinyl alcohol solution with a mass concentration of 1.5% to 3%, and the mixture is obtained after mixing.

[0017] In some embodiments of this application, the ceramic material includes at least one of boehmite and alumina.

[0018] Thirdly, this application provides a battery including the positive electrode sheet described in the first aspect.

[0019] Fourthly, this application provides a battery including a positive electrode, said positive electrode comprising a PCM / ceramic composite material prepared by the preparation method described in the second aspect.

[0020] Fifthly, this application provides an energy storage device, including a housing and at least one battery as described in the third or fourth aspect, the battery being housed within the housing.

[0021] In a sixth aspect, this application provides an electrical device including the energy storage device described in the fifth aspect, wherein the energy storage device supplies power to the electrical device.

[0022] Compared with the prior art, this application has at least the following beneficial effects:

[0023] This application provides a positive electrode sheet, a method for preparing a PCM (Phase Change Material) / ceramic composite material, a battery, and an energy storage device. The positive electrode sheet includes a positive current collector, which comprises a first region with a positive active material and a second region without a positive active material. The second region has an insulating layer comprising a PCM / ceramic composite material, which includes a phase change composite material and a ceramic material. Based on the mass of the PCM / ceramic composite material, the mass percentage of the phase change composite material is 30%–50%, and the mass percentage of the ceramic material is 50%–70%. The insulating layer of the positive electrode sheet in this application contains the aforementioned PCM / ceramic composite material, enabling phase change endothermic reaction to occur in the early to mid-stages of battery thermal runaway. The ceramic material reinforces the structure of the phase change composite material, increasing the critical temperature for triggering thermal runaway while improving the structural stability of the positive electrode sheet, thereby enhancing the battery's thermal stability and improving the thermal safety performance of lithium-ion batteries in energy storage scenarios. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a schematic diagram of the structure of the positive electrode sheet in one embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the structure of the positive electrode sheet in another embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the positive electrode sheet in the third embodiment of this application;

[0028] Figure 4 This is a schematic diagram of the positive electrode sheet in the fourth embodiment of this application;

[0029] Figure 5 This is a schematic diagram of the positive electrode sheet in the fifth embodiment of this application;

[0030] Figure 6 This is a schematic diagram of the positive electrode sheet in the sixth embodiment of this application;

[0031] Figure 7 This is a schematic diagram of the structure of a residential energy storage system according to one embodiment of this application;

[0032] Figure 8This is a schematic diagram of the structure of an energy storage system according to one embodiment of this application;

[0033] Figure 9 This is a differential scanning calorimeter (DSC) test image of the PCM / ceramic composite material of Example 1 of this application;

[0034] Figure 10 The graph shows the test results of the positive electrode during the thermal runaway test.

[0035] Figure 11 This is a graph showing the test results of the negative electrode during the thermal runaway test.

[0036] Explanation of reference numerals in the attached drawings: 1-Energy storage device, 2-Energy conversion device, 3-First user load, 4-Second user load, 10-First region, 11-Positive electrode active material layer, 20-Second region, 21-Insulation layer, 400-Energy storage system, 410-High voltage cable, 420-First energy conversion device, 430-Second energy conversion device. Detailed Implementation

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] This application provides a positive electrode sheet, which includes a positive current collector. The positive current collector includes a first region with a positive active material and a second region without a positive active material. The second region has an insulating layer, which includes a PCM (Phase Change Material) / ceramic composite material. The PCM / ceramic composite material is composed of a phase change composite material and a ceramic material. The phase change composite material is composed of SnBi58 and TiO2. Based on the mass of the PCM / ceramic composite material, the mass percentage of the phase change composite material is 30% to 50%, and the mass percentage of the ceramic material is 50% to 70%. For example, the mass percentage of the phase change composite material is 30%, 40%, or 50%, and the mass percentage of the ceramic material is 50%, 60%, or 70%. When the content of the phase change composite material is too low (e.g., below 30%), it is difficult to effectively perform phase change heat absorption on the positive electrode sheet; when the content of the phase change composite material is too high (e.g., above 70%), the content of ceramic material is too low, which is not conducive to improving the insulation performance of the PCM / ceramic composite material, and at the same time, it is difficult to reinforce the structure of the phase change composite material. The insulating layer of the positive electrode sheet of this application contains the above-mentioned PCM / ceramic composite material, and by controlling the mass ratio of the phase change composite material to the ceramic material within the above-mentioned range, the ceramic material can improve the insulation performance and reinforce the structure of the phase change composite material. This increases the critical temperature for triggering thermal runaway of the battery while improving the structural stability of the positive electrode sheet, thereby improving the thermal stability of the battery and thus improving the thermal safety performance of the energy storage device containing the battery.

[0044] This application does not impose any particular restrictions on the distribution of the second region in the positive electrode sheet.

[0045] In one alternative implementation, the second region is located at at least one end of the positive electrode along its length. For example, refer to... Figure 1 The second region 20 can be located at one end of the positive electrode along its length; for example, referring to... Figure 2 The second region 20 can be located at both ends of the positive electrode plate along its length. From Figure 1 or Figure 2 It can also be seen that the first region 10 is provided with a positive electrode active material layer 11, and the second region is provided with an insulating layer 21.

[0046] In another alternative implementation, the second region is located on at least one side of the positive electrode sheet along its width direction. For example, refer to... Figure 3 The second region 20 can be located on one side of the positive electrode sheet along its width direction; for example, refer to Figure 4 The second region 20 can be located on both sides of the positive electrode sheet along the width direction.

[0047] In another alternative embodiment, the second region is located at at least one end of the positive electrode sheet along its length direction, and simultaneously located on at least one side of the positive electrode sheet along its width direction. For example, refer to... Figure 5 The second region 20 can be located at one end of the positive electrode along the length direction and one side along the width direction; for example, referring to Figure 6 The second region 20 can be located at both ends of the positive electrode sheet along the width direction and on both sides along the length direction, forming a structure surrounding the positive electrode active material layer.

[0048] In some embodiments of this application, the phase transition temperature range of the PCM / ceramic composite material is 130°C to 150°C. For example, the phase transition temperature range of the PCM / ceramic composite material is 130°C, 135°C, 140°C, 145°C, or 150°C. This facilitates phase transition endothermy during the early to mid-stages of thermal runaway in lithium-ion batteries, thus cooling the top region of the lithium-ion battery (including parts of the positive electrode), thereby improving the overall thermal safety performance of the lithium-ion battery. In this application, the early to mid-stages of thermal runaway refer to the temperature range within the lithium-ion battery between the separator pore-closing temperature and the melting and rupture temperature, which is approximately 130°C to 180°C.

[0049] In some embodiments of this application, the latent heat of the PCM / ceramic composite material is 30 J / g to 40 J / g. For example, the latent heat of the PCM / ceramic composite material is 30 J / g, 32 J / g, 35 J / g, 37 J / g, or 40 J / g. This facilitates phase transition endothermy during the early to mid-stages of thermal runaway in lithium-ion batteries, thus helping to cool the top region of the lithium-ion battery (including parts of the positive electrode), thereby improving the overall thermal safety performance of the lithium-ion battery.

[0050] In some embodiments of this application, the thickness of the insulating layer on one side is 5 μm to 25 μm. For example, the thickness of the insulating layer on one side is 5 μm, 10 μm, 15 μm, 20 μm, or 25 μm. The insulating layer of this application can be disposed on at least one surface of the positive electrode sheet, for example, the insulating layer is disposed on one surface of the positive electrode sheet, or the insulating layer is disposed on both surfaces of the positive electrode sheet. By controlling the thickness of the insulating layer on one side within the above range, it is beneficial to obtain an insulating layer with excellent phase change heat absorption capacity and mechanical strength.

[0051] In some embodiments of this application, the ceramic material includes at least one of boehmite and alumina. After the ceramic material is combined with the phase change composite material to form a PCM / ceramic composite material, it can strengthen the structure of the phase change composite material and improve the structural stability of the positive electrode sheet.

[0052] The phase change composite material of this application can be a core-shell structured phase change composite material composed of SnBi58 and TiO2. SnBi58 forms the core of the core-shell structure, and TiO2 forms the shell, with a hollow structure between the core and shell. This phase change composite material can be represented as SnBi58 / void / TiO2. This phase change composite material is an existing type of phase change composite material, for example, it can be the phase change composite material provided by Zhu, S. et al., "Synthesis and characterization of a novel highdurability alloy microcapsule for thermal energy storage". Energy Materials and Solar Cells 230, 111262 (2021).

[0053] This application also provides a method for preparing PCM / ceramic composite materials, comprising the following steps:

[0054] Step A: Compact the mixture of phase change composite material and ceramic material to obtain PCM / ceramic composite material precursor. Based on the mass of the PCM / ceramic composite material precursor, the mass percentage of phase change composite material is 30% to 50%, and the mass percentage of ceramic material is 50% to 70%.

[0055] Step B: Heat the PCM / ceramic composite precursor to 80℃ to 120℃ at a heating rate of 3℃ / min to 8℃ / min, and perform a first heat preservation treatment for 0.5h to 1.5h.

[0056] Step C: The PCM / ceramic composite material precursor after the first heat preservation treatment is first heated to 390℃~410℃, then heated to 440℃~460℃, and subjected to a second heat preservation treatment for 0.5h~1.5h to obtain the PCM / ceramic composite material.

[0057] In step A, by adjusting the content of phase change composite material and ceramic material in the PCM / ceramic composite material precursor within the above range, the ceramic material in the obtained PCM / ceramic composite material can structurally reinforce the phase change composite material, thereby increasing the critical temperature for battery thermal runaway while improving the structural stability of the positive electrode sheet.

[0058] In step B, the heating rate can be 3℃ / min, 5℃ / min, or 8℃ / min, the temperature can be 80℃, 100℃, or 120℃, and the duration of the first holding treatment can be 0.5h, 1h, or 1.5h. By controlling the heating rate, heating temperature, and first holding treatment time of the PCM / ceramic composite precursor within the above ranges, it is beneficial to ensure that the moisture in the PCM / ceramic composite precursor is fully removed, preventing deformation of the PCM / ceramic composite precursor during subsequent sintering and thus affecting the performance of the PCM / ceramic composite.

[0059] In step C, the temperature can be raised to 390℃ to 410℃ at a heating rate of 3℃ / min to 8℃ / min, and then raised to 440℃ to 460℃ at a heating rate of 1℃ / min to 3℃ / min. This is because: the sintering rate affects the densification and microstructure of the ceramic. Rapid heating (e.g., heating rate of 3℃ / min to 8℃ / min) can reduce the concentration of point defects, reduce the generation of by-products, and is conducive to grain growth and increase density. Subsequent slow heating (e.g., heating rate of 1℃ / min to 3℃ / min) can stabilize the system, prevent the PCM / ceramic composite material from cracking, and enhance the structural strength of the PCM / ceramic composite material.

[0060] In some embodiments of this application, the compaction pressure is 3 MPa to 8 MPa, and the pressure holding time is 1 min to 2 min. For example, a pressure of 3 MPa, 5 MPa, or 8 MPa and a pressure holding time of 1 min, 1.5 min, or 2 min are beneficial for obtaining a compacted PCM / ceramic composite precursor. The compacted PCM / ceramic composite precursor can be cylindrical or cubic.

[0061] In some embodiments of this application, the preparation process of the mixture of phase change composite material and ceramic material includes:

[0062] The phase change composite material and ceramic material are mixed and then added to a polyvinyl alcohol solution with a mass concentration of 1.5% to 3% to obtain a mixture.

[0063] In some embodiments of this application, the ceramic material includes at least one of boehmite and alumina.

[0064] The preparation method of the PCM / ceramic composite material of this application is based on the sintering process to obtain the PCM / ceramic composite material of this application. The PCM / ceramic composite material is applied to the insulating layer of the positive electrode sheet of a lithium-ion battery. It can improve the structural stability of the positive electrode sheet while increasing the critical temperature for triggering thermal runaway of the battery, thereby improving the thermal stability of the battery and thus improving the thermal safety performance of lithium-ion batteries in storage scenarios.

[0065] This application also provides a battery including the positive electrode sheet described in any of the above embodiments.

[0066] This application also provides a battery including a positive electrode, said positive electrode comprising a PCM / ceramic composite material prepared by the preparation method described in any of the above embodiments.

[0067] In this application, the positive electrode active 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 active material layer is disposed on the surface of the positive electrode current collector; that is, 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. The single-sided thickness of the positive electrode active material layer in this application can be 8 μm to 15 μm.

[0068] In this application, the positive electrode active material layer includes a positive electrode active material. This application does not have any particular restrictions on the positive electrode active material, as long as it can achieve the purpose of this application. For example, it may include at least one of lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, and lithium manganese iron phosphate.

[0069] In this application, the positive electrode active material layer may also include a positive electrode binder. This application does not have any particular limitation on the positive 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 fluorinated resin, polypropylene resin, fiber-type binder, rubber-type binder or polyimide-type binder.

[0070] 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 active material layer. The negative active material layer can be disposed on one or both surfaces along the thickness direction of the negative current collector. In this application, the negative active material layer is disposed on the surface of the negative current collector; that is, the negative active 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 4 μm to 12 μm. The single-sided thickness of the negative active material layer in this application can be 70 μm to 200 μm.

[0071] In this application, the negative electrode active material layer includes a negative electrode active material. The negative electrode active 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.

[0072] In this application, the negative electrode active 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] Please see Figure 7 , Figure 7 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 7 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.

[0081] 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.

[0082] Please see Figure 8 , Figure 8 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 8 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] Example

[0089] 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.

[0090] Preparation Example 1

[0091] <Preparation of PCM / Ceramic Composite Precursor>

[0092] Weigh the phase change composite material SnBi58 / void / TiO2 and the ceramic material boehmite (AlOOH) according to a mass ratio of 33:67, mix them evenly to form the first mixed powder. Add the first mixed powder into a 2.0 wt% polyvinyl alcohol solution, and then grind it in an agate mortar to make the polyvinyl alcohol solution evenly distributed in the first mixed powder, obtaining the second mixed powder. Then, add the second mixed powder into a circular mold with a diameter of 30 mm, put it into a tablet press and slowly press it to 5 MPa, and keep the pressure for 1 min. After gradually releasing the pressure, prepare a 30 mm×4 mm cylindrical PCM / ceramic composite precursor.

[0093] <Preparation of PCM / Ceramic Composite>

[0094] Put the prepared PCM / ceramic composite precursor into a box-type atmosphere furnace, heat it to 100 °C at a heating rate of 5 °C / min in a nitrogen atmosphere for the first heat preservation treatment with a heat preservation time of 1 h to remove the moisture in the material. Then, heat it to 400 °C at a heating rate of 5 °C / min, and then heat it to 450 °C at a rate of 1 °C / min for the second heat preservation treatment with a heat preservation time of 1 h. Cool the sample to room temperature in the furnace to obtain the PCM / ceramic composite.

[0095] Preparation Example 2

[0096] Except that in the <Preparation of PCM / Ceramic Composite Precursor>, adjust the mass ratio of the phase change composite material and the ceramic material to 40:60, the rest is the same as in Example 1.

[0097] Preparation Example 3

[0098] Except that in the <Preparation of PCM / Ceramic Composite Precursor>, adjust the mass ratio of the phase change composite material and the ceramic material to 50:50, the rest is the same as in Example 1.

[0099] Preparation Example 4

[0100] Except that in the <Preparation of PCM / Ceramic Composite Precursor>, adjust the mass ratio of the phase change composite material and the ceramic material to 10:90, the rest is the same as in Example 1.

[0101] Preparation Example 5

[0102] Except that in the <Preparation of PCM / Ceramic Composite Precursor>, adjust the mass ratio of the phase change composite material and the ceramic material to 90:10, the rest is the same as in Example 1.

[0103] Example 1

[0104] <Preparation of Insulating Layer Paste>

[0105] 1) Add N-methylpyrrolidone (NMP) and binder PVDF to a mixer at a mass ratio of 22:1, stirring at 10 rpm and 50°C; 2) Start the mixer, stirring at 20 rpm and dispersing at 1000 rpm for 30 minutes at 50°C; 3) Start the mixer, stirring at 25 rpm and dispersing at 1150 rpm for 200 minutes at 50°C and a vacuum of -85 kPa. After the time is up, open the container and scrape the slurry from the sides; 4) Add the prepared sample to the mixer. 1) The PCM / ceramic composite material was prepared, with a stirring speed of 10 rpm and a temperature of 50℃; 5) Start stirring, with a stirring speed of 15 rpm and a dispersion speed of 1000 rpm, stirring for 5 min at a temperature of 50℃, and after the time was up, the tank was opened and the slurry was scraped off the wall; 6) Start stirring, with a stirring speed of 25 rpm and a dispersion speed of 1150 rpm, stirring for 80 min at a temperature of 50℃ and a vacuum degree of -85 kPa, to obtain the insulating layer slurry, which has a solid content of 27.5% and a viscosity of 3000 mPa·s.

[0106] <Preparation of the positive electrode>

[0107] Lithium iron phosphate (LiFePO4), conductive carbon black (Super-P), and PVDF binder were mixed in a mass ratio of 94:3:3. N-methylpyrrolidone (NMP) was then added as a solvent to prepare a positive electrode slurry with a solid content of 50 wt%. The mixture was stirred until homogeneous. This slurry was then uniformly coated onto one surface of a 10 μm thick positive electrode current collector. After drying at 85°C and rolling, a positive electrode sheet was obtained. The above steps were repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet with a double-sided coating of active material layers, each layer having a thickness of 100 μm. An insulating layer slurry was then coated onto the uncoated area of ​​the positive electrode current collector surface (the second area), resulting in an insulating layer with a thickness of 15 μm on one side. The structure of the positive electrode sheet is as follows: Figure 1 As shown.

[0108] <Preparation of Negative Electrode Sheets>

[0109] Artificial graphite (anode active material), sodium carboxymethyl cellulose (CMC-Na) thickener, Super-P conductive carbon black, and styrene-butadiene rubber (SBR) binder were mixed in a mass ratio of 96:2:1:1. Deionized water was added to prepare a negative electrode slurry with a solid content of 60 wt%, and the mixture was stirred evenly. The negative electrode slurry was uniformly coated onto one surface of a 6 μm thick copper foil current collector, dried at 85°C, and rolled to obtain a negative electrode sheet. The above steps were repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coating of negative electrode active material layers. The thickness of the negative electrode active material layer on one side was 70 μm.

[0110] <Preparation of Electrolyte>

[0111] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:4:3, 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.

[0112] <Preparation of the diaphragm>

[0113] A porous polyethylene (PE) film with a thickness of 16 μm was used as the separator.

[0114] <Preparation of Lithium-ion Batteries>

[0115] The positive electrode, separator, and negative electrode prepared above are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. This is then wound to obtain a bare battery cell. The bare battery cell is placed in an aluminum-plastic film packaging bag, vacuum dried, and then injected with electrolyte. After vacuum sealing, settling, and formation processes, a lithium-ion battery is obtained. The battery specification is 71173, and the capacity is 280Ah.

[0116] Example 2

[0117] Except for replacing the PCM / ceramic composite material in the insulating layer slurry with the PCM / ceramic composite material obtained in Preparation Example 2 in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1.

[0118] Example 3

[0119] Except for replacing the PCM / ceramic composite material in the insulating layer slurry with the PCM / ceramic composite material obtained in Preparation Example 3 in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1.

[0120] Example 4

[0121] Except for adjusting the single-sided thickness of the insulating layer to 5 μm in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1.

[0122] Example 5

[0123] Except for adjusting the single-sided thickness of the insulating layer to 20 μm in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1.

[0124] Example 6

[0125] Except for adjusting the single-sided thickness of the insulating layer to 25 μm in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1.

[0126] Comparative Example 1

[0127] Except for replacing the PCM / ceramic composite material in the insulating slurry with boehmite in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1.

[0128] Comparative Example 2

[0129] Except for replacing the PCM / ceramic composite material in the insulating layer slurry with the PCM / ceramic composite material obtained in Preparation Example 4 in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1.

[0130] Comparative Example 3

[0131] Except for replacing the PCM / ceramic composite material in the insulating layer slurry with the PCM / ceramic composite material obtained in Preparation Example 5 in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1.

[0132] Table 1. Preparation parameters for each embodiment and comparative example.

[0133]

[0134] Test methods and equipment:

[0135] Phase transition temperature and latent heat testing of samples:

[0136] The thermal properties of the PCM / ceramic composites prepared in each example were analyzed using a Netzsch DSC 200F3 differential scanning calorimeter equipped with a thermal analysis data station. The experiments were conducted under a nitrogen atmosphere, with a temperature range of 80℃ to 160℃ and a scanning rate of 10℃ / min for both heating and cooling. The melting point, freezing point, latent heat, and other data of the samples were analyzed, and the phase transition temperature of the samples was calculated.

[0137] Thermal runaway performance test:

[0138] The lithium-ion batteries prepared in each embodiment and comparative example were subjected to the initial thermal runaway performance test of a single cell according to the national standard GB / T 36276-2023. The test procedure was as follows: the lithium-ion battery that had completed initial charging was placed in the thermal runaway test device, and an 800W heating element was placed at the center of the side with the largest surface area of ​​the lithium-ion battery; constant current charging at 140A was started, heating was initiated, and the voltage, positive electrode temperature and negative electrode temperature of the lithium-ion battery were recorded. After the lithium-ion battery was triggered to thermal runaway, charging and heating were stopped, and the battery was observed for 1 hour.

[0139] Table 2 Performance data for each embodiment and comparative example

[0140] Thermal runaway time (min) Positive electrode temperature (°C) Negative electrode temperature (°C) Example 1 17.48 83.8 84.2 Example 2 18.16 86.6 86.2 Example 3 18.32 92.6 90.9 Example 4 17.23 84.1 83.5 Example 5 17.91 86.3 87.7 Example 6 18.29 90.5 89.4 Comparative Example 1 16.93 81.0 92.6 Comparative Example 2 17.02 82.7 82.3 Comparative Example 3 20.21 98.6 100.2

[0141] Figure 9 The image shows the DSC test pattern of the PCM / ceramic composite material prepared in Example 1. The upper and lower curves of the DSC test pattern illustrate the melting and freezing processes of the PCM / ceramic composite material, respectively. Figure 9 It can be seen that the melting onset temperature of the PCM / ceramic composite material is 137.6℃ and the freezing onset temperature is 132.1℃. The latent heats during melting and freezing are 46.61kJ / kg and 37.57kJ / kg, respectively, indicating that the PCM / ceramic composite material can undergo phase change endothermic reaction in the early to mid-stages of thermal runaway (around 140℃).

[0142] Combination Figure 10 and Figure 11 As can be seen from Examples 1-3 and Comparative Example 1, compared to Comparative Example 1, the insulating layer of the lithium-ion battery in this application contains PCM / ceramic composite material, which prolongs the thermal runaway time of the lithium-ion battery, increases the critical temperature for triggering thermal runaway, and enhances the thermal stability of the system. Furthermore, during the resting phase after thermal runaway, the temperature rise rate of the negative electrode column slows down, and the severity of thermal runaway is reduced. In summary, the lithium-ion battery of this application exhibits excellent thermal stability, which is beneficial to improving the thermal safety performance of energy storage devices.

[0143] The thickness of the insulating layer also affects the thermal safety performance of lithium-ion batteries. As can be seen from Examples 4 to 6, by adjusting the thickness of the insulating layer within the range of this application, it is beneficial to obtain lithium-ion batteries with excellent thermal stability and to improve the thermal safety performance of energy storage devices, based on the lithium-ion battery having the insulating layer of this application.

[0144] As can be seen from Examples 1-3 and Comparative Examples 2-3, when the content of the phase change composite material is too low (e.g., Comparative Example 2), the thermal runaway time, positive electrode temperature, and negative electrode temperature are very close to those of Comparative Example 1, indicating that the cooling effect of the phase change composite material in Comparative Example 2 is slight and cannot effectively improve the thermal safety performance of the lithium-ion battery. When the content of the phase change composite material is too high (e.g., Comparative Example 3), the thermal runaway time is significantly delayed compared to Comparative Example 1, but the positive electrode temperature and negative electrode temperature rise significantly, indicating that after a large amount of the phase change composite material in Comparative Example 3 melts, the reaction contact area of ​​the top electrode increases, which leads to a decrease in the thermal stability of the structure. This application, by controlling the mass ratio of the phase change composite material to the ceramic material within the above range, is beneficial to obtaining a lithium-ion battery with excellent thermal stability and to improving the thermal safety performance of the energy storage device.

[0145] The above provides a detailed description of the preparation method of the positive electrode sheet, PCM / ceramic composite material, and battery disclosed in this application. Specific examples are used to illustrate the principles and implementation methods of this application. The description of the above embodiments is 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, The present invention includes a positive electrode current collector, wherein the positive electrode current collector comprises a first region having a positive electrode active material disposed thereon and a second region not having the positive electrode active material disposed thereon; The second region is provided with an insulating layer, which includes a PCM / ceramic composite material. The PCM / ceramic composite material is composed of a phase change composite material and a ceramic material. The phase change composite material is a core-shell structure composed of SnBi58 and TiO2. SnBi58 is the core of the core-shell structure, and TiO2 is the shell of the core-shell structure. There is a hollow structure between the core and the shell. Based on the mass of the PCM / ceramic composite material, the mass percentage of the phase change composite material is 30%~50%, and the mass percentage of the ceramic material is 50%~70%.

2. The positive electrode sheet according to claim 1, characterized in that, The phase transition temperature range of the PCM / ceramic composite material is 130℃~150℃.

3. The positive electrode sheet according to claim 1, characterized in that, The latent heat of the PCM / ceramic composite material is 30 J / g ~ 40 J / g.

4. The positive electrode sheet according to claim 1, characterized in that, The thickness of the insulating layer on one side is 5μm to 25μm.

5. The positive electrode sheet according to claim 1, characterized in that, The ceramic material includes at least one of boehmite and alumina.

6. A method for preparing a PCM / ceramic composite material, characterized in that, Includes the following steps: A mixture of phase change composite material and ceramic material is compacted to obtain a PCM / ceramic composite material precursor. Based on the mass of the PCM / ceramic composite material precursor, the mass percentage of the phase change composite material is 30%~50%, and the mass percentage of the ceramic material is 50%~70%. The phase change composite material is a core-shell structure composed of SnBi58 and TiO2, where SnBi58 is the core and TiO2 is the shell, with a hollow structure existing between the core and the shell. The PCM / ceramic composite material precursor is heated to 80℃~120℃ and subjected to a first heat preservation treatment for 0.5h~1.5h. The PCM / ceramic composite material precursor after the first heat preservation treatment is first heated to 390℃~410℃, then heated to 440℃~460℃, and subjected to a second heat preservation treatment for 0.5h~1.5h to obtain the PCM / ceramic composite material.

7. The method for preparing the PCM / ceramic composite material according to claim 6, characterized in that, The compaction pressure is 3MPa~8MPa.

8. The method for preparing the PCM / ceramic composite material according to claim 7, characterized in that, The preparation process of the mixture of phase change composite material and ceramic material includes: The phase change composite material and the ceramic material are mixed and then added to a polyvinyl alcohol solution with a mass concentration of 1.5% to 3%, and the mixture is obtained after mixing.

9. The method for preparing the PCM / ceramic composite material according to claim 7, characterized in that, The ceramic material includes at least one of boehmite and alumina.

10. A battery, characterized in that, Includes the positive electrode sheet as described in any one of claims 1 to 5.

11. A battery, characterized in that, It includes a positive electrode sheet, wherein the positive electrode sheet comprises a PCM / ceramic composite material prepared by the preparation method according to any one of claims 6 to 9.

12. An energy storage device, characterized in that, It includes a housing and at least one battery as described in claim 10 or 11, the battery being housed within the housing.

13. An electrical appliance, characterized in that, The device includes the energy storage device of claim 12, wherein the energy storage device supplies power to the electrical equipment.

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