Electrode assembly and method of manufacturing the same, battery, and electric device

Abstract

The application relates to the technical field of batteries, in particular to an electrode assembly, a preparation method thereof, a battery and a power utilization device; the electrode assembly comprises a positive electrode, a negative electrode and a diaphragm between the positive electrode and the negative electrode; the diaphragm comprises a base film and a functional layer, the functional layer is arranged on a side surface of the base film close to the negative electrode; the functional layer comprises composite fibers, the composite fibers comprise carbon nano-porous microspheres and a polymer; the carbon nano-porous microspheres comprise polar groups; the weight average molecular weight of the polymer is 200,000 Dalton to 1,000,000 Dalton. Compared with the prior art, the application introduces a high-performance diaphragm, obtains an electrode assembly with high safety characteristics, and further applies the electrode assembly in a battery to obtain a battery with excellent cycle life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, and more particularly to an electrode assembly, a preparation method thereof, a battery, and a power utilization device. BACKGROUND

[0002] Lithium battery separators are generally made of polyethylene or polypropylene (PE or PP). The main function of the battery separator is to physically separate the positive and negative electrodes and prevent the passage of electrons in the battery, while allowing the passage of ions, thereby completing the rapid transport of lithium ions embedded in the positive and negative electrodes during the electrochemical charging and discharging process. Due to the characteristics of the electrode material itself, lithium dendrites are easily generated on the surface of the electrode during the charging and discharging process. The growth of these dendrites will pierce the separator, causing the battery to short circuit and fail, and even explode and burn, etc. Therefore, the battery separator is the key to battery safety, and a separator with excellent performance can also directly affect the cycle performance and other characteristics of the battery. SUMMARY

[0003] Therefore, the present application provides an electrode assembly, a preparation method thereof, a battery, and a power utilization device. By introducing a high-performance separator, an electrode assembly with high safety characteristics is obtained, and further application in a battery can obtain a battery with excellent cycle life.

[0004] To solve the above technical problems, the present application is implemented as follows:

[0005] According to one aspect of the present application, an electrode assembly is provided, comprising a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode; the separator comprises a base film and a functional layer, and the functional layer is arranged on the side surface of the base film close to the negative electrode.

[0006] The functional layer comprises a composite fiber, and the composite fiber comprises carbon nano-porous microspheres and a polymer; the carbon nano-porous microspheres comprise a polar group; and the weight average molecular weight of the polymer is 200,000 to 1,000,000 Daltons.

[0007] In some embodiments, the polymer comprises at least one of polyvinylidene fluoride, polyvinyl alcohol, polyethylene terephthalate, polyvinylpyrrolidone, polyimide, and polyethylene oxide.

[0008] In some embodiments, the particle size of the carbon nano-porous microspheres is 100 nm to 2,000 nm.

[0009] In some embodiments, the polar group comprises at least one of a hydroxyl group, an amino group, and a carboxyl group.

[0010] In some embodiments, the average diameter of the composite fiber is 200 nm to 3000 nm.

[0011] In some embodiments, the functional layer has a coverage area greater than the area of the negative electrode, and the functional layer further has a width that exceeds the width of the negative electrode by 2 mm to 3 mm.

[0012] In some embodiments, the functional layer has a porosity greater than 40%.

[0013] In some embodiments, the separator has an elongation at break greater than 365%.

[0014] In some embodiments, the separator has a thickness of 10 μm to 20 μm.

[0015] In some embodiments, the base film has a thickness of 5 μm to 10 μm.

[0016] In some embodiments, the functional layer has a thickness of 5 μm to 10 μm.

[0017] According to another aspect of the present application, the present application provides a method for preparing the electrode assembly described in the above technical solution, comprising the following steps:

[0018] a) dissolving a polypeptide in a first solvent to perform a hydrothermal reaction to obtain carbon nano-porous microspheres;

[0019] b) dissolving a polymer in a second solvent, adding the carbon nano-porous microspheres obtained in step a) to perform dispersion to obtain an electrospinning solution;

[0020] c) electrospinning the electrospinning solution obtained in step b) on one side of the surface of a base film, drying to form a functional layer, and then performing hot pressing to obtain a separator;

[0021] d) assembling the separator obtained in step c) with a positive electrode and a negative electrode to obtain an electrode assembly.

[0022] In some embodiments, in step a), the polypeptide comprises at least one of a collagen peptide, a fish protein peptide, and a whey protein peptide.

[0023] In some embodiments, in step a), the first solvent comprises at least one of water, N,N-dimethylformamide, N-methylpyrrolidone, and hexafluoroisopropanol.

[0024] In some embodiments, in step a), the mass ratio of the polypeptide to the first solvent is (1-5): 100.

[0025] In some embodiments, in step a), the hydrothermal reaction is performed at a pressure of 5-10 MPa, a temperature of 160-220°C, and for a time period of 12-24 hours.

[0026] In some embodiments, in step a), after the hydrothermal reaction, the reaction mixture is cooled to room temperature, and then sequentially filtered, washed, and dried to obtain the carbon nanoporous microspheres.

[0027] In some embodiments, in step b), the polymer comprises at least one of polyvinylidene fluoride, polyvinyl alcohol, polyethylene terephthalate, polyvinylpyrrolidone, polyimide, and polyethylene oxide.

[0028] In some embodiments, in step b), the second solvent comprises at least one of N,N-dimethylformamide, N-methylpyrrolidone, and hexafluoroisopropanol.

[0029] In some embodiments, in step b), the mass ratio of the polymer to the second solvent is (10-15): 100.

[0030] In some embodiments, in step b), the dispersion process comprises vortex mixing for 0.5-1.5 minutes, ultrasonic dispersion for 30-60 minutes at 200-400 W, and vacuum defoaming at 20-40°C for 20-40 minutes to obtain the electrospinning solution.

[0031] In some embodiments, in step b), the concentration of the carbon nanoporous microspheres in the electrospinning solution is 1-5 wt%.

[0032] In some embodiments, in step b), the viscosity of the electrospinning solution is 1000-3000 mPa·s.

[0033] In some embodiments, in step c), the electrospinning process comprises: after cleaning and drying the base film, fixing the base film on a rotating roller, spraying the electrospinning solution through a spinneret, and moving the spinneret uniformly and reciprocally on one side of the surface of the base film to spin; further, the rotating speed of the rotating roller is 0-500 rpm; and / or, the inner diameter of the spinneret is 0.06-0.5 mm; and / or, the distance between the spinneret and the rotating roller is 10-20 cm; and / or, the positive voltage at the spinneret is 15-25 KV, and the negative voltage at the rotating roller is -1 KV to -5 KV; and / or, the flow rate of the electrospinning solution is 0.5-2 mL / h; and / or, the spinning time is 1-5 h; and / or, the thickness of the spinning is 10-30 μm.

[0034] In some embodiments, in step c), the drying process is performed in a fume hood, and the drying time is 20-30 h.

[0035] In some embodiments, in step c), the hot-pressing temperature is 50-90 °C, and the time is 5-15 min.

[0036] According to another aspect of the present application, the present application provides a battery comprising the electrode assembly according to the above technical solution or the electrode assembly prepared by the preparation method according to the above technical solution.

[0037] According to another aspect of the present application, the present application provides an electric device comprising the battery according to the above technical solution.

[0038] The technical solution of the present application has at least the following beneficial effects:

[0039] 1. The electrode assembly provided by the present application introduces a high-performance separator, which improves the puncture resistance and ion conductivity of the separator through good interaction between the carbon nano-porous microspheres and the polymer: on the one hand, the hydroxyl and / or amino groups on the surface of the carbon nano-porous microspheres can form strong interfacial bonding with the polymer through hydrogen bonding and electrostatic interaction, thereby improving the elongation at break of the composite fiber; at the same time, the carbon nano-porous microspheres as fillers are dispersed in the functional layer of the separator, which can form a "rigid skeleton", thereby significantly improving the puncture resistance of the separator, and reducing the risk of short circuit caused by electrode expansion or dendrite growth during charging and discharging; on the other hand, the carbon nano-porous microspheres have abundant pores, although the pores are not connected, but the high specific surface area can store a large amount of electrolyte through physical adsorption or capillary action, thereby realizing good adsorption of the electrolyte, improving the electrolyte retention of the separator, and improving the interfacial compatibility and wettability of the interface, thereby inhibiting the growth of lithium dendrites, and the retention of the electrolyte in the pores can reduce the loss of the electrolyte, and maintain the ion conductivity efficiency of the separator region.

[0040] 2、The application can further enhance the compatibility with electrolyte, reduce the interface impedance, and promote the rapid migration of lithium ions at the separator-electrolyte interface by performing lithiumophilic modification (introducing polar groups such as hydroxyl groups and carboxyl groups) on the surface of the carbon nanoporous microspheres.

[0041] 3、The preparation method provided by the application has simple process, mild and easy-to-control conditions, low raw material cost, is suitable for large-scale commercial use, and has wide application prospect.

[0042] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following description, or can be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0043] The drawings herein are incorporated into the specification and constitute a part of the specification, show embodiments consistent with the application, and together with the specification serve to explain the principles of the application.

[0044] Figure 1 A scanning electron microscope (SEM) image of the composite fiber obtained by electrospinning in Example 1 of the application.

[0045] Figure 2 A scanning electron microscope (SEM) image of the carbon nanoporous microspheres obtained in Example 1 of the application.

[0046] The specific embodiments of the application have been shown and described in the foregoing description, and will become apparent to those skilled in the art from the foregoing description, or can be learned by practice of the application. These drawings and written description are not intended to restrict the scope of the inventive concept in any way, but to illustrate specific embodiments thereof by reference to particular embodiments. DETAILED DESCRIPTION

[0047] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application.

[0048] The endpoints of the ranges and any values in the ranges disclosed herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that allow for significant error and variations. The endpoints of the ranges and values of the ranges should be considered approximate, and it is within the scope of the application to employ other approaches that fall within the broad concept of the ranges and values.

[0049] In the description of the application, “the same chemical composition” should be understood broadly, that is, the main components of both have consistent chemical composition, or the chemical composition of both is basically consistent, which can have errors within the range that can be understood by those skilled in the art and within the range that can be allowed in the art, or contain impurities within the allowable range.

[0050] In the description of the present application, "A and / or B" can include any one of the case of A alone, the case of B alone, the case of A and B, wherein A, B are only for example, which can be any technical feature connected by "and / or" in the present application.

[0051] If there is no special description, the "includes" and "contains" mentioned in the present application means open, which can also be closed. For example, the "includes" and "contains" can mean that it can also include or contain other components not listed, or only include or contain the listed components.

[0052] If there is no special description, all embodiments and optional embodiments of the present application can be combined to form new technical solutions.

[0053] If there is no special description, all technical features and optional technical features of the present application can be combined to form new technical solutions.

[0054] If there is no special description, all steps of the present application can be performed in sequence, or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can include steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can also include step (c), which means that step (c) can be added to the method in any order, for example, the method can include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0055] At present, with the rapid development of electrochemical energy storage devices, lithium ion batteries have been widely concerned due to their high energy density and high power density, but in the charging and discharging process of lithium ion batteries, due to the characteristics of the electrode material itself, lithium dendrites are easily generated on the surface of the electrode, the growth of these dendrites can easily pierce the separator, causing battery short circuit failure, therefore, the battery separator is the key to battery safety, in recent years, the coating technology of lithium battery separator has developed rapidly, and researchers have prepared different gel polymer materials by initiating polymerization reaction and applied them to the separator material. Among them, some researchers have prepared expensive gel polymer materials under complex process conditions such as high temperature, ultraviolet light and high concentration of lithium salt initiator, but due to process or cost reasons, they cannot be applied on a large scale. Therefore, there is an urgent need to find a simple method to modify the separator to manufacture lithium ion batteries with high performance and excellent cycle life.

[0056] Based on this, the inventors of the present application have made in-depth research, prepared carbon nano porous microspheres from natural non-toxic and environmentally friendly polypeptide materials through hydrothermal reaction, and then used electrospinning technology to stretch polymer solution or melt into nanofibers through a high-voltage electric field, the carbon nano porous microspheres can be dispersed in the spinning solution as a filler, and uniformly attached to the surface of the separator or embedded in the fiber after the fiber is solidified; the high mechanical strength and high conductivity of the carbon nano porous microspheres provided by the present application can improve the puncture resistance and ion conductivity of the separator, and the carbon nano porous microspheres can adsorb electrolyte, improve the interfacial compatibility and wettability of the interface, and inhibit the growth of lithium dendrites. Specifically, the present application adopts the following technical scheme:

[0057] According to one aspect of the present application, the present application provides an electrode assembly, comprising a positive electrode, a negative electrode and a separator located between the positive electrode and the negative electrode; the separator comprises a base film and a functional layer, the functional layer is arranged on the side surface of the base film close to the negative electrode;

[0058] The functional layer comprises a composite fiber, the composite fiber comprises carbon nano porous microspheres and a polymer; the carbon nano porous microspheres comprise a polar group; the weight average molecular weight of the polymer is 200,000-1,000,000 Dalton.

[0059] The present application introduces a functional layer on the separator, uses a composite fiber comprising carbon nano porous microspheres and a polymer in the functional layer, obtains a composite separator filled with carbon nano porous microspheres with excellent performance, modifies the puncture resistance and ion conductivity of the separator, and further applies in the electrode assembly according to a specific connection mode, realizes good overall interaction, can achieve good overall technical effect at the level of the electrode assembly and the battery, improves the interfacial compatibility and wettability of the interface, inhibits the growth of lithium dendrites, and finally realizes the beneficial effects of improving the cycle performance of the battery, reducing the internal resistance and improving the safety.

[0060] In the specific embodiment of the present application, the separator of the electrode assembly is arranged between the positive electrode and the negative electrode; the separator comprises a base film and a functional layer, the functional layer is arranged on the side surface of the base film close to the negative electrode; wherein the base film can adopt a separator base film well known to those skilled in the art, and the present application does not have special limitations on the type and source of the base film, such as a polyethylene (PE) base film, a polypropylene (PP) base film, etc., a ceramic layer can also be arranged on the above-mentioned base film, and the present application does not have special limitations thereon.

[0061] In the embodiment of the present application, the functional layer comprises composite fibers, and the composite fibers comprise carbon nano-porous microspheres and polymers; wherein the carbon nano-porous microspheres comprise polar groups, and on this basis, the present application can form strong interfacial bonding with the polymers through the polar groups, improve the elongation at break of the composite fibers, and at the same time, the carbon nano-porous microspheres can form a "rigid skeleton" as fillers dispersed in the functional layer of the separator, thereby significantly improving the puncture resistance of the separator, and reducing the risk of short circuit caused by electrode expansion or dendrite growth during charging and discharging. In the present application, the polar groups preferably comprise at least one of a hydroxyl group, an amino group and a carboxyl group, and more preferably a hydroxyl group and / or an amino group, which can form strong interfacial bonding with the polymers through hydrogen bonding and electrostatic interaction.

[0062] In the embodiment of the present application, the particle size of the carbon nano-porous microspheres is preferably 100 nm to 2000 nm, and more preferably 100 nm to 200 nm, and can be specifically 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1500 nm, 2000 nm, or any value between any two of them. When the particle size of the carbon nano-porous microspheres is too large, the large particle size destroys the uniformity of the solution, resulting in uneven fiber diameter or formation of beaded defects, and when the particle size of the carbon nano-porous microspheres is too small (e.g. < 20 nm), the microspheres may agglomerate due to the high surface energy of the microspheres, reducing the stability of the solution and affecting the continuity of the spinning. By selecting the above suitable particle size range, the present application can ensure that the carbon nano-porous microspheres can better maintain the uniformity and stability of the solution, and do not affect the continuity of the spinning.

[0063] In the embodiment of the present application, the weight average molecular weight of the polymer is 200,000 to 1,000,000, preferably 600,000 to 800,000, and can be specifically 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, or any value between any two of them. By specially limiting the weight average molecular weight of the polymer, the present application can improve the tensile strength, tear resistance and puncture resistance of the separator, and the reason is that when the molecular weight of the polymer is too low, the intermolecular force is weak, resulting in insufficient mechanical strength of the separator, which is easy to break during processing or use, and causes short circuit risk, and when the molecular weight of the polymer is too high, the molecular chains are excessively entangled, which may result in decreased flexibility and increased brittleness of the material, and the melt viscosity is extremely high during processing, which is difficult to be formed by casting, stretching and other processes, affecting the subsequent spinning process. Therefore, by controlling the weight average molecular weight of the polymer, the present application can not only improve the mechanical properties such as puncture resistance of the separator, but also facilitate better control of the preparation process of the separator, and further obtain a product with the desired performance.

[0064] In the detailed description of the present application, the polymer preferably comprises at least one of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyvinylpyrrolidone (PVP), polyimide (PI), polyethylene oxide (PEO), and more preferably polyvinylidene fluoride (PVDF). The above-mentioned specific types of polymers have good spinnability and film-forming property. In the preferred embodiment of the present application, the polymer is polyvinylidene fluoride (PVDF) because, on the one hand, it has good chemical stability: PVDF has strong resistance to acid, alkali, salt and organic solvents (such as carbonates in electrolyte), which can effectively avoid the failure of the separator due to electrolyte corrosion during long-term charging and discharging of the battery; on the other hand, it has good electrolyte affinity: the fluorine atoms of PVDF interact with lithium salts (such as LiPF6) in the electrolyte, which can promote lithium ion transmission and reduce the internal resistance of the battery. The present application does not have special restrictions on the source of the polymer, and commercially available or self-made products known to those skilled in the art can be used.

[0065] In the detailed description of the present application, the average diameter of the composite fiber is preferably 200 nm to 3000 nm, and can be specifically 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, or any value between any two of them. When the diameter of the composite fiber is too large, the porosity of the coating layer will decrease significantly, although the monofilament strength of the thick fiber is high, but the diameter that is too large will lead to a decrease in the entanglement between fibers, and the overall mechanical flexibility will decrease; when the diameter of the composite fiber is too small, the overall mechanical strength of the separator will be insufficient and the structural stability will be poor. Therefore, the present application uses the above-mentioned suitable composite fiber diameter, which can not only ensure the porosity of the coating layer, but also ensure the overall mechanical strength and structural stability of the separator, thereby improving the ion conduction capacity and stability of the battery.

[0066] In the specific embodiments of the present application, the functional layer preferably has a coverage area greater than that of the negative electrode; further, the functional layer preferably has a width of 2-3 mm beyond the negative electrode. The advantages of such an arrangement include: (1) when the coverage area of the functional layer is greater than that of the negative electrode, the risk of the negative electrode edge separating from the separator to form a gap due to the expansion of the graphite negative electrode can be avoided; (2) the edge of the conventional separator is prone to form a "dry area" due to the evaporation of the electrolyte, which can cause the SEI film to break, and the superhydrophilic property of the functional layer described above can maintain the edge electrolyte wetting; (3) the functional layer will shrink at temperatures above 120°C, for example, the shrinkage rate of a PAN fiber coating is 5-8% at 150°C, and if the functional layer has the same size as the negative electrode, the exposed area of the edge after shrinkage can reach 10-15%, and the 2-3 mm allowance can compensate for the shrinkage, so that the effective coverage area of the functional layer remains above 95%. At the same time, the coverage area of the functional layer is not the larger the better, and the inventors of the present application have found that when the width of the functional layer beyond the negative electrode exceeds 3 mm, the excess edge material will increase the internal resistance; in addition, it can also cause uneven distribution of the electrolyte, and the excess functional layer can adsorb too much electrolyte (about 20 μL / cm 2 of electrolyte), which can lead to insufficient electrolyte in the central region, and thus reduce the ion conduction rate; therefore, selecting an appropriate coverage area of the functional layer can significantly reduce the risk of lithium precipitation, reduce the internal resistance, and improve the ion conduction rate.

[0067] In the specific embodiments of the present application, the porosity of the functional layer is preferably greater than 40%. If the porosity of the functional layer is too small, it can lead to insufficient electrolyte wetting, increased interfacial resistance, and reduced ion transmission efficiency, and it can also cause the material to have too high hardness and insufficient toughness, increased brittleness, and easy breakage under stress.

[0068] In the specific embodiments of the present application, the elongation at break of the separator is preferably greater than 365%. It should be further noted that the elongation at break is an important indicator of the flexibility and tensile strength of a material, and the elongation at break of a conventional separator is 250-300%, and if the elongation at break of the separator is too small, the separator can easily break or be damaged due to mechanical stress during battery assembly (such as winding) or use; and insufficient flexibility of the separator can cause more stress concentration and crack propagation during battery cycling, thereby accelerating the performance degradation of the battery.

[0069] In the embodiment of the present application, the thickness of the separator is preferably 10-20 μm; wherein the thickness of the base film is preferably 5-10 μm, and the thickness of the functional layer is preferably 5-10 μm. When the total thickness of the separator is too large, the ion transmission efficiency is reduced, the lithium ion migration path is lengthened, and thus the battery internal resistance is increased, and the charge-discharge rate and cycle stability are decreased; when the total thickness of the separator is too small, the retention capacity of the electrolyte is decreased, and at the same time, the thin separator can not effectively absorb and retain the electrolyte, resulting in blocked ion conduction, which also leads to increased battery internal resistance.

[0070] By adopting suitable functional layer porosity, separator elongation at break and separator thickness, the present application realizes overall good interaction, which can further improve the ion conduction capacity of the electrode assembly, reduce the battery internal resistance and improve the battery performance.

[0071] The present application does not have special restrictions on the positive electrode and the negative electrode, and the conventional technical solutions of the positive electrode sheet and the negative electrode sheet known to those skilled in the art can be used.

[0072] In the embodiment of the present application, the positive electrode is specifically a positive electrode sheet, which comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side surface of the positive electrode current collector in the thickness direction; wherein the positive electrode current collector can adopt a metal foil, a foam metal or a composite current collector. For example, as the metal foil, silver surface treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrode, carbon or titanium, etc. can be used; the foam metal can be foam nickel, foam copper, foam aluminum, foam alloy, etc.; the composite current collector can comprise a polymer material base layer and a metal layer, and the composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0073] In the detailed description of the present application, the positive electrode active material layer comprises a positive electrode active material, and the present application does not have special limitations on the specific type of the positive electrode active material. The active material that can be used for the positive electrode of a battery cell known in the art can be selected by those skilled in the art according to actual needs. Specifically, the positive electrode active material can include, but is not limited to, at least one of lithium transition metal oxides, olivine structure lithium-containing phosphates, and their respective modified compounds; examples of lithium transition metal oxides can include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds; examples of olivine structure lithium-containing phosphates can include, but are not limited to, at least one of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and their modified compounds. These materials can be obtained through commercial channels.

[0074] In the detailed description of the present application, the positive electrode active material layer can also generally include a positive electrode binder, a positive electrode conductive agent, and other optional additives. As an example, the positive electrode binder can include at least one of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB); the positive electrode conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers. These materials can be obtained through commercial channels.

[0075] In the detailed description of the present application, the preparation method of the positive electrode sheet adopts a method well known to those skilled in the art, in which the raw materials are first mixed in a certain ratio in a solvent to prepare a positive electrode slurry, and then the positive electrode slurry is coated on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode sheet can be obtained.

[0076] In the detailed description of the present application, the negative electrode is specifically a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side surface of the negative electrode current collector in the thickness direction; wherein the negative electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be adopted; the composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material, and the composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0077] In the detailed description of the present application, the negative electrode active material layer comprises a negative electrode active material, and the present application does not have special limitations on the specific type of the negative electrode active material, and any active material known in the art that can be used for the negative electrode of a battery cell can be adopted, and a person skilled in the art can select according to actual needs. Specifically: the negative electrode active material can comprise at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material and lithium titanate, etc.; wherein the silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite and silicon alloy; and the tin-based material can be selected from at least one of elemental tin, tin oxide compound and tin alloy. These materials can all be obtained through commercial channels.

[0078] In the detailed description of the present application, the negative electrode active material layer usually further comprises a negative electrode binder, a negative electrode conductive agent and other optional additives. As an example, the negative electrode binder can comprise at least one of carboxymethyl cellulose (CMC), polyacrylonitrile (PAN), styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS); the negative electrode conductive agent can comprise at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene and carbon nanofibers; and other optional additives such as thickening agents, etc. These materials can all be obtained through commercial channels.

[0079] In the detailed description of the present application, the preparation method of the negative electrode sheet adopts a method well known to a person skilled in the art, that is, first mixing the raw materials in a certain ratio in a solvent to prepare a negative electrode slurry, then coating the negative electrode slurry on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0080] In the embodiment of the present application, the electrode assembly comprises a roll-type electrode assembly or a stack-type electrode assembly, and preferably the roll-type electrode assembly for easy processing. Specifically, the positive electrode sheet, the separator and the negative electrode sheet are sequentially arranged with the separator between the positive electrode sheet and the negative electrode sheet, and then wound to form a roll structure.

[0081] In the embodiment of the present application, the electrode assembly is provided with tabs, and the tabs can guide the current out of the electrode assembly; the tabs include positive tabs and negative tabs.

[0082] According to another aspect of the present application, the present application provides a preparation method of the electrode assembly described in the above technical solution, comprising the following steps:

[0083] a) dissolving the polypeptide in a first solvent for hydrothermal reaction to obtain carbon nano-porous microspheres;

[0084] b) dissolving the polymer in a second solvent, adding the carbon nano-porous microspheres obtained in step a) for dispersion to obtain an electrospinning solution;

[0085] c) electrospinning the electrospinning solution obtained in step b) on one side of the base film, drying to form a functional layer, and then hot-pressing to obtain the separator;

[0086] d) assembling the separator obtained in step c) with the positive electrode and the negative electrode to obtain the electrode assembly.

[0087] The polypeptide is first dissolved in a first solvent for hydrothermal reaction to obtain carbon nano-porous microspheres. In the present application, the polypeptide preferably comprises at least one of collagen peptide, fish protein peptide and whey protein peptide, more preferably collagen peptide or whey protein peptide, and more preferably collagen peptide. In the preferred embodiment of the present application, the polypeptide is collagen peptide, and the proportion of proline (Pro) and hydroxyproline (Hyp) in the collagen peptide can reach 20% to 30%, and the cyclic pyrrolidine structure has a dual role in the hydrothermal reaction; the primary structure of the collagen peptide is a repeated sequence of "-Gly-Pro-Hyp-", and the smallest side chain (only H atom) of glycine (Gly) makes the molecular chain more easily self-assembled into an ordered helical structure under hydrothermal conditions, and is converted into a regular layered porous carbon after carbonization. The present application does not have special restrictions on the source of the polypeptide, and commercially available products known to those skilled in the art can be used.

[0088] In the embodiment of the present application, the first solvent preferably comprises at least one of water, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and hexafluoroisopropanol (HFIP), and more preferably water. The present application does not have special restrictions on the source of the first solvent, and commercially available products known to those skilled in the art can be used. In the present application, the water preferably uses deionized water known to those skilled in the art.

[0089] In the embodiment of the present application, the mass ratio of the polypeptide to the first solvent is preferably (1-5):100, and can be 1:100, 2:100, 3:100, 4:100, 5:100, or any value between any two of them. The present inventors have found through experiments that when the mass ratio of the polypeptide to the first solvent is too high, agglomeration is likely to occur, and when the mass ratio of the polypeptide to the first solvent is too low, the yield of carbon nanohole microspheres will be affected. On this basis, the present application limits the above specific mass ratio range to ensure that the subsequent hydrothermal reaction proceeds smoothly.

[0090] The present application dissolves the polypeptide in the first solvent to obtain a first solution, and then transfers it to the inner liner of a high-pressure reaction kettle known to those skilled in the art for hydrothermal reaction, and further performs hydrothermal reaction.

[0091] In the embodiment of the present application, the pressure of the hydrothermal reaction is preferably 5-10 MPa, and more preferably 6-8 MPa, and can be 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, or any value between any two of them; within this pressure range, the stability of the system can be better maintained, and the interaction between molecules can be promoted.

[0092] In the embodiment of the present application, the temperature of the hydrothermal reaction is preferably 160-220℃, and can be 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, or any value between any two of them. The present inventors have found through experiments that when the temperature of the hydrothermal reaction is lower than 160℃, carbon spheres cannot be formed, and only oligosaccharides or aromatic compounds are produced; when the temperature of the hydrothermal reaction is higher than 220℃, the polar functional groups on the polypeptide will be inactivated. Therefore, by using a suitable range of hydrothermal reaction temperature in the present application, the carbonization efficiency and the retention of polar groups of the reaction product can be well balanced.

[0093] In the embodiment of the present application, the hydrothermal reaction time is preferably 12-24 h, more preferably 16-20 h, and specifically can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h, or any value between any two of them. The present inventors have found that when the hydrothermal reaction time is less than 12 h, the growth of the carbon nanometer porous microspheres is not conducive, but when the hydrothermal reaction time is greater than 24 h, the pore structure collapses, which is also not conducive to the generation of the carbon nanometer porous microspheres.

[0094] In the embodiment of the present application, after the hydrothermal reaction, the reaction mixture is preferably cooled to room temperature, and then sequentially filtered, washed, and dried to obtain the carbon nanometer porous microspheres. The present application does not have special restrictions on the filtration and drying processes, and the technical means for post-treatment of the hydrothermal reaction product known to those skilled in the art can be used. In the present application, the washing process preferably includes alternating washing with water and ethanol until the filtrate is colorless. The main purpose of this step is to remove unreacted organic matter in the hydrothermal reaction; the drying temperature is preferably 60-80°C, more preferably 70°C, and the drying time is preferably 2-6 h, more preferably 4 h.

[0095] The core mechanism of the present application for preparing the carbon nanometer porous microspheres by hydrothermal reaction is as follows:

[0096] (1) Precursor formation stage (100-150°C): This stage occurs during the process of heating to the hydrothermal reaction temperature; it mainly involves the dissociation of the helical structure and the molecular rearrangement. Under the conditions of high temperature and high pressure, water molecules are inserted into the gap between the triple helix, which destroys the hydrogen bond and van der Waals force, resulting in the dissociation of the helical structure into single-chain polypeptides. The dissociated polypeptide chains self-assemble into nanoscale aggregates through hydrophobic interaction, with the hydrophobic region (containing Pro / Hyp) aggregating inward and the hydrophilic group (such as -COOH, -NH2) exposed outward, forming a preliminary spherical precursor. Then a preliminary dehydration and condensation reaction is carried out, and the hydroxyl group (-OH) of hydroxyproline and the carboxyl group (-COOH) of glycine undergo intramolecular / intermolecular dehydration condensation to form ester bonds or amide bonds. Through the above reaction, the hydrophilic group in the precursor can be reduced, thereby promoting the preliminary construction of the hydrophobic carbon network.

[0097] (ii) Carbonization and carbon skeleton construction stage (150℃~220℃): This stage mainly occurs at the hydrothermal reaction temperature; it mainly involves the decomposition and carbonization of amino acid residues, and in this process, proline / hydroxyproline plays a key role, which is specifically manifested as follows: the cyclic structure is decomposed at about 200℃, releasing CO2 and NH3, and at the same time forming a stable five-membered carbon ring intermediate as a node of the carbon skeleton; at the same time, the gas generated in the reaction process can form initial pores in the carbon network. Finally, the cross-linking and graphitization of the carbon chain, which is specifically manifested as follows: the carbon chain in the polypeptide chain is cross-linked to form a three-dimensional network through C-C bonds, the alkyl side chain of the hydrophobic amino acid residue (such as alanine) is dehydrogenated to form an aromatic ring structure, and a graphite-like microcrystal is gradually formed, and finally the carbon nano porous microspheres are obtained.

[0098] After obtaining the carbon nano porous microspheres, the polymer is dissolved in a second solvent, and the obtained carbon nano porous microspheres are added for dispersion to obtain an electrospinning solution. In the present application, the polymer preferably includes at least one of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyvinylpyrrolidone (PVP), polyimide (PI), and polyethylene oxide (PEO), and more preferably polyvinylidene fluoride (PVDF); the above specific types of polymers have good spinnability and film-forming property. In the preferred embodiment of the present application, the polymer is polyvinylidene fluoride (PVDF), because on the one hand, it has good chemical stability: PVDF has strong resistance to acids, bases, salts and organic solvents (such as carbonate in electrolyte), which can effectively avoid the failure of the separator due to electrolyte corrosion during long-term charging and discharging of the battery; on the other hand, it has good affinity for electrolyte: the fluorine atoms of PVDF interact with lithium salts (such as LiPF6) in the electrolyte, which can promote lithium ion transmission and reduce the internal resistance of the battery. The present application does not have special restrictions on the source of the polymer, and commercially available or self-made products known to those skilled in the art can be used.

[0099] In the specific embodiment of the present application, the second solvent preferably includes at least one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and hexafluoroisopropanol (HFIP), and more preferably N,N-dimethylformamide (DMF). The present application does not have special restrictions on the source of the second solvent, and commercially available products known to those skilled in the art can be used.

[0100] In the embodiment of the present application, the mass ratio of the polymer to the second solvent is preferably (10-15):100, and can be 10:100, 11:100, 12:100, 13:100, 14:100, 15:100, or any value between any two of them. The present inventors have found through experiments that when the mass ratio of the polymer to the second solvent is too high, on the one hand, the jet stability is destroyed: high viscosity makes the solution flowability poor, and in the subsequent spinning process, the jet is difficult to be stretched by the electric field, forming "droplet ejection" instead of a fine stream, resulting in uneven fiber diameter, on the other hand, the dispersibility of the carbon nano-porous microspheres deteriorates: high concentration of polymer chains intensifies entanglement, and the carbon nano-porous microspheres are easily wrapped to form agglomerates; when the mass ratio of the polymer to the second solvent is too low, the degree of polymer chain entanglement is low at low concentration, and the jet is easily broken during stretching, forming a large amount of "flying flock" short fibers, and only discontinuous fiber fragments can be obtained on the collection plate; therefore, the present application selects a suitable ratio to ensure that the subsequent reaction proceeds smoothly and the expected product is obtained.

[0101] In the present application, the polymer is dissolved in the second solvent, preferably by using the technical means of magnetic stirring at room temperature for 4-6 h to completely dissolve, which is well known to those skilled in the art, to ensure uniform mixing, and finally form a transparent and uniform polymer solution.

[0102] In the embodiment of the present application, the dispersion process preferably includes: first vortex mixing for 0.5-1.5 min, then dispersing under ultrasonic conditions of 200-400 W for 30-60 min, and finally vacuum degassing at 20-40℃ for 20-40 min to obtain an electrospinning solution. The present application does not have special restrictions on the vortex and vacuum degassing process, and the experimental operation steps well known to those skilled in the art can be used. In the preferred embodiment of the present application, vortex mixing is performed for 1 min, vacuum degassing is performed at 25℃ for 30 min, and the dispersion is performed under ultrasonic conditions of 200-400 W for 30-60 min, which can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any value between any two of them, to avoid long-time ultrasonic dispersion which can destroy the structure of the carbon nano-porous microspheres; and an electrospinning solution is obtained after dispersion.

[0103] In the embodiment of the present application, the concentration of the carbon nanometer porous microspheres in the electrospinning solution is preferably 1wt%-5wt%, and can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, or any value between any two of them. The present inventors have found through experiments that when the concentration of the carbon nanometer porous microspheres is <1wt%, the distribution of the carbon nanometer porous microspheres in the composite fiber is sparse, and it is difficult to form an effective conductive network or functional site, and the modification effect of the separator is limited; when the concentration of the carbon nanometer porous microspheres is >5wt%, the carbon nanometer porous microspheres will agglomerate, resulting in a sudden increase in the viscosity of the solution, instability of the jet in the spinning process, and nodules or fractures in the composite fiber, and obvious agglomerates can be seen under the SEM image. The present application adopts a suitable concentration of carbon nanometer porous microspheres, which can be uniformly dispersed in the composite fiber, so that the mechanical strength of the composite fiber is maintained well, and the porous structure of the carbon nanometer porous microspheres can improve the electrolyte adsorption capacity of the separator.

[0104] In the embodiment of the present application, the viscosity of the electrospinning solution is preferably 1000mPa·s-3000mPa·s, and can be 1000Pa·s, 1500Pa·s, 2000Pa·s, 2500Pa·s, 3000Pa·s, or any value between any two of them. The present inventors have found through experiments that when the viscosity of the electrospinning solution is too low (<1000Pa·s), the jet of the electrospinning solution is easy to split into droplets, forming a large number of bead-shaped structures, and the continuity of the composite fiber is poor, and when the viscosity of the electrospinning solution is too high (>3000Pa·s), the diameter of the composite fiber becomes thick, and it is difficult to extrude during the spinning process, resulting in unstable flow rate of the spinning.

[0105] After obtaining the electrospinning solution, the present application electrospins the obtained electrospinning solution on one side of the surface of the base film, dries it to form a functional layer, and then hot-presses to obtain a separator. The separator prepared by the present application is a composite separator, and the principle of preparation is to stretch the polymer solution or melt into nanometer fibers by a high-voltage electric field, and the carbon nanometer porous microspheres can be dispersed in the electrospinning solution as fillers, and uniformly attached to the surface of the separator or embedded in the fiber after the fiber solidifies.

[0106] In the embodiment of the present application, the electrospinning process preferably includes: cleaning and drying the base film, fixing it on a rotating roller, and spraying the electrospinning solution out of a spinneret, which moves uniformly and reciprocally on one side of the surface of the base film for spinning.

[0107] This invention does not impose any special limitations on the electrospinning equipment; conventional equipment known to those skilled in the art for electrospinning can be used. In a preferred embodiment of this invention, the electrospinning equipment includes a high-voltage power supply with a pressure range of 10kV to 20kV, a syringe, and a rotating collector (aluminum foil or metal roller, the surface of which can be pre-treated to enhance adhesion).

[0108] The present invention does not impose any special restrictions on the process of cleaning and drying the base film. The technique of ultrasonic cleaning with ethanol for 5 min to 15 min followed by drying, which is well known to those skilled in the art, can be used to ensure that there is no oil or impurities on the surface of the base film.

[0109] In a specific embodiment of the present invention, the rotational speed of the rotating roller is preferably 0~500 rpm, specifically 0 rpm, 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or any value between two of these. By controlling the rotational speed of the rotating roller within the above range, the present invention enables the prepared composite fiber to meet the performance requirements of the present invention.

[0110] In a specific embodiment of the present invention, the inner diameter of the spinneret is preferably 0.06 mm to 0.5 mm, specifically 0.06 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or any value between two of these. The inventors of this application have found through experiments that when the inner diameter of the spinneret is too small, the solution flow resistance is high, and insufficient liquid supply can easily lead to unstable jetting, or even "flow interruption." If the liquid supply pressure is forcibly increased, excessive shear force may disrupt the homogeneity of the solution. When the inner diameter of the spinneret is too large, the spinning solution is easily extruded at a high speed, and excessive droplets are easily accumulated at the tip of the spinneret, resulting in "multi-jet" or drastic fluctuations in fiber diameter during jetting.

[0111] In a specific embodiment of the present invention, the distance between the spinneret and the rotating roller is preferably 10cm to 20cm, specifically 10cm, 15cm, 20cm, or any value between two of these. The inventors of this application have experimentally discovered that when the distance between the spinneret and the rotating roller is too close, the diameter of the composite fiber increases; conversely, when the distance is too far, the diameter of the composite fiber is too thin, which can easily lead to breakage and is detrimental to the production of composite fibers. In a preferred embodiment of the present invention, the distance between the spinneret and the rotating roller is 15cm.

[0112] In the embodiment of the present application, the positive voltage at the spinneret is preferably 15KV-25KV, and the negative voltage at the rotating roller is preferably -1KV--5KV; by controlling the above-mentioned voltages, the uniformity and diameter of the composite fiber can be ensured to meet the requirements of the present application; the present inventor has found that the higher the positive voltage at the spinneret, the thinner the fiber, but too high voltage will lead to unstable jet, thereby affecting the distribution of the carbon nano-porous microspheres in the electrospinning solution, and thus affecting the solution conductivity.

[0113] In the embodiment of the present application, the flow rate of the electrospinning solution sprayed is preferably 0.5mL / h-2mL / h, and can be specifically 0.5mL / h, 0.8mL / h, 1mL / h, 1.5mL / h, 2mL / h, or a value between any two of them. The present inventor has found that when the flow rate of the electrospinning solution sprayed is too fast, the electrospinning is prone to form a beaded structure, and the continuity of the composite fiber is poor, and when the flow rate of the electrospinning solution sprayed is too slow, the yield of the composite fiber will be obviously affected; on this basis, the electrospinning solution sprayed at the flow rate in the above-mentioned suitable range can better achieve the purpose of the present application.

[0114] In the embodiment of the present application, the spinning time is preferably 1h-5h, and can be specifically 1h, 2h, 3h, 4h, 5h, or a value between any two of them. If the spinning time is too long, the thickness of the composite fiber will be too large, and the uniformity will be a problem.

[0115] In the embodiment of the present application, the thickness of the spinning is preferably 10μm-30μm, and can be specifically 10μm, 15μm, 20μm, 25μm, 30μm, or a value between any two of them. If the thickness of the spinning is too large, the pores of the separator will be blocked, affecting the electrolyte infiltration, and if it is too small, it will be difficult to form an effective conductive network or functional site, and the modification effect on the separator will be limited.

[0116] In the embodiment of the present application, the drying process is preferably carried out in a fume hood, and the drying time is preferably 20h-30h; the purpose is to form a functional layer after removing the residual solvent, and the present application has no other special limitation.

[0117] In the specific embodiments of the present application, the temperature of the hot pressing is preferably 50-90℃, and can be specifically 50℃, 60℃, 70℃, 80℃, 90℃, or a value between any two of them. It needs to be further explained that when the temperature of the hot pressing is too low, it can be difficult for the plastic deformation to occur between the base film and the composite fibers, and the composite fibers or the film layers cannot be tightly combined, the density of the diaphragm after hot pressing is insufficient, the structure is loose, the lap strength between fibers is low, and the tensile strength and puncture resistance are not obviously improved; when the temperature of the hot pressing is too high, the fiber structure can be damaged (such as fiber fusion, adhesion into a sheet), so that the porosity decreases sharply, and even the pores are completely closed, losing the gas permeability or ion conduction function.

[0118] In the specific embodiments of the present application, the hot pressing time is preferably 5-15min, and can be specifically 5min, 10min, 15min, or a value between any two of them. It needs to be further explained that the hot pressing time and the hot pressing temperature need to be further matched and coordinated, when the hot pressing time is too short, the fibers cannot be effectively combined, the diaphragm density is insufficient, the structure is loose, and the mechanical property improvement is limited; when the hot pressing time is too long, long-time hot pressing can cause the fibers to continuously adhere, the pores are further compressed, and the gas permeability or ion conductivity decreases.

[0119] Therefore, by selecting appropriate hot pressing temperature and time, the present application can ensure that the fibers and the diaphragm are tightly combined and have a certain porosity, thereby improving the structural stability and ion conduction capacity of the electrode assembly.

[0120] After obtaining the diaphragm, the obtained diaphragm is assembled with a positive electrode and a negative electrode to obtain an electrode assembly. In the present application, the positive electrode and the negative electrode are the same as described in the above technical solution, and will not be described here. As described in the above technical solution, the diaphragm of the provided electrode assembly is arranged between the positive electrode and the negative electrode; the diaphragm comprises a base film and a functional layer, and the functional layer is arranged on the side surface of the base film close to the negative electrode.

[0121] In the specific embodiments of the present application, the assembly method is preferably winding or lamination, and more preferably winding; the conventional operation means for preparing the electrode assembly known to those skilled in the art can be used, and the present application has no special limitation thereon.

[0122] The preparation method provided by the present application has simple process, mild and easy-to-control conditions, low raw material cost, is suitable for large-scale commercial use, and has broad application prospect.

[0123] According to another aspect of the present application, the present application provides a battery comprising the electrode assembly according to the above technical solution or the electrode assembly prepared by the preparation method according to the above technical solution. Therefore, the battery has all the features and advantages of the electrode assembly according to the above technical solution, which will not be repeated here. Specifically, the electrode assembly can be prepared by a winding process or a stacking process.

[0124] In the detailed description of the present application, the battery includes but is not limited to a button cell, a soft pack battery, and a cylindrical battery; the battery can include an outer package, which can be used to package the electrode assembly and the electrolyte.

[0125] For the electrolyte, it plays a role of ion conduction between the positive electrode and the negative electrode. The present application does not have specific limitations on the type of electrolyte, which can be selected according to the needs. For example, the electrolyte can be liquid, gel or all-solid-state.

[0126] In the detailed description of the present application, the electrolyte adopts an electrolyte solution; the electrolyte solution comprises an electrolyte salt and a solvent; wherein the electrolyte salt preferably comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoroboric oxalate, lithium boric oxalate, lithium difluorophosphoric oxalate, lithium tetrafluorophosphoric oxalate, and more preferably lithium hexafluorophosphate; the solvent preferably comprises one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC), and more preferably a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC). The present application does not have special limitations on the source of the solvent, and commercially available products of the above-mentioned cyclic carbonates and chain carbonates known to those skilled in the art can be used.

[0127] In the detailed description of the present application, the electrolyte solution preferably further comprises a film-forming additive, such as a negative electrode film-forming additive and a positive electrode film-forming additive, and can further comprise an additive capable of improving certain properties of the battery, such as an additive for improving the overcharge performance of the battery, an additive for improving the high-temperature or low-temperature performance of the battery, etc.

[0128] The present application does not have special limitations on the preparation method of the electrolyte solution, and a conventional preparation method of the electrolyte solution known to those skilled in the art can be used. In the preferred embodiment of the present application, the respective components in the electrolyte solution are mixed uniformly to obtain the corresponding electrolyte solution.

[0129] In the specific embodiments of the present application, the outer package of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc., or a soft package, such as a bag-type soft package; the material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed. The present application does not have a particular limitation on the shape of the battery, which can be cylindrical, square or any other shape, and the person skilled in the art can select according to the specific actual needs. In the preferred embodiments of the present application, the preparation method of the battery specifically comprises: after the positive electrode, the separator and the negative electrode are prepared into a roll core, they are wrapped with an aluminum plastic film, then electrolyte is injected thereinto, and finally the battery is prepared through processes such as standing, formation and capacity distribution.

[0130] According to still another aspect of the present application, the present application provides a power utilization device comprising the battery according to the above technical solution. Thus, the power utilization device has all the features and advantages of the battery according to the above technical solution, which will not be repeated here. Specifically, the battery can serve as the power supply of the power utilization device or as the energy storage unit of the power utilization device. The power utilization device can include but is not limited to mobile devices (such as mobile phones, notebook computers), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, and energy storage systems.

[0131] The present application will be described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present application are not limited thereto, and the following examples are only part of the examples of the present application, not a limitation of the present application. If the specific technology or condition is not specified in the examples, it is performed according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained from the market.

[0132] Example 1

[0133] (1) Preparation of carbon nano porous microspheres:

[0134] The collagen peptide was taken into a beaker, deionized water was added, and a magnetic stirrer was used to stir at room temperature for 1 h until the collagen peptide was completely dissolved, to obtain a collagen peptide aqueous solution with a concentration of 3 wt%. Then the solution was transferred to the inner liner of a high-pressure reaction kettle (the pressure was 6 MPa), sealed and placed in an oven at a temperature of 200℃, and reacted for 18 h. After the reaction was completed, it was cooled to room temperature, the reaction kettle was opened, and a black-brown solution was drawn out, which was washed with deionized water and ethanol alternately until the filtrate was colorless, and the unreacted organic matter was removed. The washed solution was placed in a forced air oven and dried at 70℃ for 4 h, and the product, carbon nano porous microspheres, was collected; as tested, the SEM image is shown in FIG. 1, and the particle size of the product is about 1000 nm. Figure 2 The collagen peptide was taken into a beaker, deionized water was added, and a magnetic stirrer was used to stir at room temperature for 1 h until the collagen peptide was completely dissolved, to obtain a collagen peptide aqueous solution with a concentration of 3 wt%. Then the solution was transferred to the inner liner of a high-pressure reaction kettle (the pressure was 6 MPa), sealed and placed in an oven at a temperature of 200℃, and reacted for 18 h. After the reaction was completed, it was cooled to room temperature, the reaction kettle was opened, and a black-brown solution was drawn out, which was washed with deionized water and ethanol alternately until the filtrate was colorless, and the unreacted organic matter was removed. The washed solution was placed in a forced air oven and dried at 70℃ for 4 h, and the product, carbon nano porous microspheres, was collected; as tested, the SEM image is shown in FIG. 1, and the particle size of the product is about 1000 nm.

[0135] (2) Preparation of electrospinning solution:

[0136] Take 12.5 g of polyvinylidene fluoride (weight average molecular weight 600,000 daltons) into a beaker, slowly add N,N-dimethylformamide (DMF) to 100 g, use a magnetic stirrer to stir at room temperature for 6 h to completely dissolve, form a transparent and uniform solution. Then take an appropriate amount of product carbon nanometer porous microspheres of step (1) into the above solution, configure a spinning solution with a carbon nanometer porous microsphere concentration of 3 wt%, first vortex mix for 1 min, then ultrasonic dispersion for 45 min, and then put into a vacuum oven at 30℃ for vacuum degassing (vacuum degree < -0.09 MPa) for 30 min, to obtain an electrospinning solution.

[0137] (3) Preparation of the separator:

[0138] In an environment with a temperature of 25℃ and a humidity of < 40%, the prepared electrospinning solution (2000 mPa·s) is sucked into the tube with a 10 ml syringe, and a precision steel needle is used as a spinneret. The inner diameter of the spinneret is 0.2 mm, the distance between the spinneret and the rotating drum is controlled to be 15 cm, the spinning flow rate is 0.8 mL / h, the positive high voltage at the needle of the electrospinning instrument is 25 KV, the negative high voltage at the rotating drum is -3 KV, the base film PE (thickness of 10 μm) is placed on the rotating drum, the needle is uniformly translated left and right, the spinning time is 3 h, and the spinning layer thickness is controlled to be 10 μm. The SEM image of the composite fiber obtained by electrospinning is shown in FIG. 1. The obtained separator is placed in a fume hood for 24 h, and after completely removing the residual solvent, a functional layer is formed. Then, the separator is hot-pressed at 80℃ for 10 min to obtain the required separator of the application, wherein the porosity of the functional layer is 50%. Figure 1

[0139] (4) Preparation method of the positive electrode sheet:

[0140] The positive electrode main material lithium iron phosphate, the conductive agent Super P, and the positive electrode binder PVDF are mixed in a mass ratio of 97:2:1, then N-methyl pyrrolidone (NMP) solvent is added for uniform mixing to prepare a positive electrode slurry; and the positive electrode slurry is uniformly coated on the positive and negative surfaces of the aluminum foil coated with the conductive carbon layer at a surface density of 20 mg / cm 2 , air-dried at 80℃, then cold-pressed, die-cut and cut to obtain the positive electrode sheet.

[0141] (5) Preparation method of the negative electrode sheet:

[0142] The negative electrode main material graphite, the conductive agent Super P, and the negative electrode binder CMC are mixed in a mass ratio of 96:2:2 with deionized water to prepare a negative electrode slurry; and the negative electrode slurry is uniformly coated on the aluminum foil coated with the conductive carbon layer at a surface density of 20 mg / cm 2 ​The copper foil is coated on both sides with the uniform coating, and is subjected to air blowing drying at 80°C, followed by cold pressing, die cutting and cutting to obtain the negative electrode sheet.

[0143] (6) The battery preparation method:

[0144] The above positive electrode sheet, the separator, and the negative electrode sheet are prepared into a roll core, wherein the separator needs to completely wrap the positive electrode sheet and the negative electrode sheet, and the functional layer in the separator is opposite to the negative electrode side, the functional layer covers an area greater than that of the negative electrode, and the width of the functional layer beyond the negative electrode sheet on one side is 2 mm; the obtained roll core is wrapped with an aluminum plastic film, and electrolyte is injected thereinto. Finally, the lithium iron phosphate battery is prepared through processes such as standing, formation, and capacity distribution.

[0145] The electrolyte is composed of lithium salt LiPF6 with a mass concentration of 1 mol / L, 5% additive fluoroethylene carbonate (FEC) in mass concentration, and a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1.

[0146] Example 2

[0147] The preparation method provided in Example 1 is adopted, and the only difference is that in step (1), the raw material for preparing the carbon nano porous microspheres is replaced from collagen peptide to whey protein peptide.

[0148] Example 3

[0149] (1) Preparation of carbon nano porous microspheres:

[0150] The same as Example 1.

[0151] (2) Preparation of electrospinning solution:

[0152] 10 g of polyvinylidene fluoride (weight average molecular weight 600,000 daltons) is placed in a beaker, and N,N-dimethylformamide (DMF) is slowly added to 100 g, and a magnetic stirrer is used to stir at room temperature for 6 h until completely dissolved to form a transparent and uniform solution. Then, an appropriate amount of product carbon nano porous microspheres in step (1) is added to the above solution to prepare a spinning solution with a carbon nano porous microsphere concentration of 1 wt%, which is first vortex mixed for 1 min, then ultrasonically dispersed for 45 min, and then placed in a vacuum oven at 30°C for vacuum degassing (vacuum degree < -0.09 MPa) for 30 min to obtain the electrospinning solution.

[0153] (3) Preparation of the separator:

[0154] The prepared electrospinning solution (2200 mPa·s) was sucked into the tube with a 10 ml syringe under the environment of temperature 25℃ and humidity <40%, and a precision steel needle was used as a spinneret with an inner diameter of 0.2 mm, the distance between the spinneret and the rotating drum was controlled to be 15 cm, the spinning flow rate was 0.8 mL / h, the positive high voltage at the needle of the electrospinning instrument was 25 KV, the negative high voltage at the drum was -3 KV, the base film PE (with a thickness of 10 μm) was placed on the rotating drum, the needle was uniformly translated left and right, the spinning time was 3 h, and the spinning layer thickness was controlled to be 10 μm. The obtained separator was placed in a fume hood for 24 h, and after the residual solvent was completely removed, a functional layer was formed, then the functional layer was hot-pressed at 80℃ for 10 min, and the required separator of the application was obtained, wherein the porosity of the functional layer was 45%.

[0155] The remaining steps were performed according to the preparation method of Example 1 above, and finally the corresponding battery was prepared.

[0156] Example 4

[0157] (1) Preparation of carbon nano porous microspheres:

[0158] The same as Example 1.

[0159] (2) Preparation of electrospinning solution:

[0160] 15 g of polyvinylidene fluoride (weight average molecular weight 600,000 daltons) was taken in a beaker, N,N-dimethylformamide (DMF) was slowly added to 100 g, and a magnetic stirrer was used to stir at room temperature for 6 h until completely dissolved to form a transparent and uniform solution. Then, an appropriate amount of product of step (1) carbon nano porous microspheres was added to the above solution to prepare a spinning solution with a carbon nano porous microsphere concentration of 5 wt%, which was first vortex mixed for 1 min, then ultrasonically dispersed for 45 min, and then placed in a vacuum oven for vacuum degassing (vacuum degree < -0.09 MPa) at 30℃ for 30 min to obtain an electrospinning solution.

[0161] (3) Preparation of the separator:

[0162] The prepared electrospinning solution (3600 mPa·s) was sucked into the tube with a 10 ml syringe under the environment of temperature 25℃ and humidity <40%, and a precision steel needle was used as a spinneret with an inner diameter of 0.2 mm, the distance between the spinneret and the rotating drum was controlled to be 15 cm, the spinning flow rate was 0.8 mL / h, the positive high voltage at the needle of the electrospinning instrument was 25 KV, the negative high voltage at the drum was -3 KV, the base film PE (with a thickness of 10 μm) was placed on the rotating drum, the needle was uniformly translated left and right, the spinning time was 3 h, and the spinning layer thickness was controlled to be 10 μm. The obtained separator was placed in a fume hood for 24 h, and after the residual solvent was completely removed, a functional layer was formed, then the functional layer was hot-pressed at 80℃ for 10 min, and the required separator of the application was obtained, wherein the porosity of the functional layer was 48%.

[0163] The remaining steps are performed according to the preparation method of Example 1 above, and the corresponding battery is finally prepared.

[0164] Example 5

[0165] The preparation method provided in Example 1 is adopted, and the difference is that:

[0166] (3) Preparation of the separator:

[0167] In an environment with a temperature of 25°C and a humidity of <40%, the prepared electrospinning solution (2000 mPa·s) is sucked into the tube with a 10 ml syringe, and a precision steel needle is used as a spinneret with an inner diameter of 0.2 mm. The distance between the spinneret and the rotating drum is controlled to be 15 cm, the spinning flow rate is 0.8 mL / h, the positive high voltage at the needle of the electrospinning instrument is 25 KV, the negative high voltage at the drum is -3 KV, the base film PE (thickness of 10 μm) is placed on the rotating drum, the edges of the base film PE on the drum are blocked with a shield, the purpose is to make the coating area of the subsequent functional layer less than the area of the negative electrode and the single edge of the functional layer exceeds the edge of the negative electrode sheet by 3 mm, the needle is uniformly translated left and right, the spinning time is 3 h, and the spinning layer thickness is controlled to be 10 μm. The obtained separator is placed in a fume hood for 24 h, and after completely removing the residual solvent, the functional layer is formed, and then hot pressing is performed at 80°C for 10 min to obtain the required separator of the application, wherein the porosity of the functional layer is 50%.

[0168] Example 6

[0169] The preparation method provided in Example 1 is adopted, and the difference is only that the coating area of the functional layer is greater than the area of the negative electrode and the single edge of the functional layer exceeds the width of the negative electrode sheet by 5 mm.

[0170] Example 7

[0171] The preparation method provided in Example 1 is adopted, and the difference is only that in step (3), the spinning layer thickness is controlled to be 5 μm.

[0172] Example 8

[0173] The preparation method provided in Example 1 is adopted, and the difference is only that in step (3), the spinning layer thickness is controlled to be 15 μm.

[0174] Example 9

[0175] The preparation method provided in Example 1 is adopted, and the difference is only that in step (1), the concentration of the collagen peptide aqueous solution is adjusted to 0.5 wt%, and the particle size of the carbon nano porous microspheres is further prepared to be 100 nm±10 nm.

[0176] Example 10

[0177] The preparation method provided in Example 1 is adopted, and the difference is only that in step (1), the concentration of the collagen peptide aqueous solution is adjusted to 8wt%, and the carbon nano porous microspheres with a particle size of 2000nm±10nm are further prepared.

[0178] Example 11

[0179] The preparation method provided in Example 1 is adopted, and the difference is that:

[0180] (2) Preparation of electrospinning solution:

[0181] Take 10g of polyvinyl alcohol (weight average molecular weight 200,000 Dalton) and slowly add 80mL of deionized water into a beaker, and place it in a 85℃ constant temperature water bath, and stir with a magnetic stirrer for 2.5h until the solution is completely transparent and free of particles (cover the beaker with aluminum foil to reduce water evaporation). Then take an appropriate amount of product carbon nano porous microspheres in step (1) and add it to the above solution to prepare a spinning solution with a carbon nano porous microsphere concentration of 3wt%, maintain a 60℃ water bath, and continue stirring for 1 hour to ensure uniform dispersion of the microspheres. Then transfer the solution to a vacuum drying oven, and degas at a temperature of 60℃ and a vacuum degree of <-0.09MPa for 30min to obtain an electrospinning solution.

[0182] The remaining steps are carried out according to the preparation method of Example 1 above, and the corresponding battery is finally prepared.

[0183] Example 12

[0184] The preparation method provided in Example 1 is adopted, and the difference is only that in step (2), the amount of polyvinylidene fluoride added is adjusted to 18g; and the porosity of the functional layer formed subsequently is 36%.

[0185] Comparative Example 1

[0186] The preparation method provided in Example 1 is adopted, and the difference is only that a conventional PE separator is used without a functional layer.

[0187] Comparative Example 2

[0188] (1) Preparation of carbon nano porous microspheres:

[0189] Take the collagen peptide into a beaker, add deionized water, use a magnetic stirrer to stir at room temperature for 1 h until the collagen peptide is completely dissolved, and obtain a collagen peptide aqueous solution with a concentration of 5 wt%. Then, transfer the solution into the inner liner of a high-pressure reaction kettle (pressure is 6 MPa), seal it and place it in an oven, react at a temperature of 200°C for 18 h. After the reaction is completed, cool to room temperature, open the reaction kettle and extract the black-brown solution, and wash it with deionized water and ethanol alternately until the filtrate is colorless, and remove the unreacted organic matter. After the washed solution is placed in a forced air oven and dried at 70°C for 4 h, the product, carbon nanometer porous microspheres, is collected.

[0190] (2) Take 12.5 g of polyvinylidene fluoride (weight average molecular weight 600,000 daltons) into a beaker, slowly add N,N-dimethylformamide (DMF) to 100 g, use a magnetic stirrer to stir at room temperature for 6 h until completely dissolved, and form a transparent and uniform solution. Then, take an appropriate amount of the product carbon nanometer porous microspheres of step (1) and add them to the above solution to configure a mixed solution with a carbon nanometer porous microsphere concentration of 2.5 wt%. After direct coating on the base film PE, it is found that an effective separator coating layer cannot be formed.

[0191] Comparative Example 3

[0192] (1) Preparation of electrospinning solution:

[0193] Take 12.5 g of polyvinylidene fluoride (weight average molecular weight 600,000 daltons) into a beaker, slowly add N,N-dimethylformamide (DMF) to 100 g, use a magnetic stirrer to stir at room temperature for 6 h until completely dissolved, and form a transparent and uniform solution, which is used as the electrospinning solution.

[0194] (2) Preparation of separator

[0195] In an environment with a temperature of 25°C and a humidity of <40%, the prepared electrospinning solution is sucked into the tube with a 10 ml syringe, a precision steel needle is used as the spinneret, the inner diameter of the spinneret is 0.2 mm, the distance between the spinneret and the rotating drum is controlled to be 15 cm, the spinning flow rate is 0.8 mL / h, the positive high voltage at the needle of the electrospinning instrument is 25 KV, the negative high voltage at the drum is -3 KV, the base film PE (thickness is 10 μm) is placed on the rotating drum, the needle is uniformly translated left and right, the spinning time is 3 h, and the spinning layer thickness is controlled to be 10 μm. The obtained separator is placed in a fume hood for 24 h to completely remove the residual solvent to form a coating, and then hot-pressed at 80°C for 10 min to obtain the separator, wherein the porosity of the coating is 48%.

[0196] The remaining steps are carried out according to the preparation method of Example 1 above, and finally the corresponding battery is prepared.

[0197] Comparative Example 4

[0198] The preparation method provided in Example 1 was adopted, with the difference being that the functional layer in the separator was opposite to the positive electrode side.

[0199] Performance test:

[0200] 1. Performance test of the separator: The separator was cut into a sample with a width of 20 mm for standby.

[0201] (1) Tensile strength test: The separator of each example and the comparative example was symmetrically clamped in the upper and lower clamps, and the distance from the clamping position to the lap end was usually (50±1) mm. It was ensured that the clamps could stably fix the sample to avoid sliding or falling off during the test. The tester was started, and an external force was applied to the sample at a stable speed of (5±1) mm / min until the sample was broken, and the tensile strength was recorded.

[0202] (2) Elongation at break test: The separator of each example and the comparative example was symmetrically clamped in the upper and lower clamps, and the distance from the clamping position to the lap end was usually (50±1) mm. It was ensured that the clamps could stably fix the sample to avoid sliding or falling off during the test. The tester was started, and an external force was applied to the sample at a stable speed of (5±1) mm / min until the sample was broken, and the elongation at break was recorded.

[0203] (3) Contact angle test: The cut separator of each example and the comparative example was placed on a glass slide to ensure that the glass slide and the separator were horizontal. A contact angle tester was used to inject an appropriate amount of electrolyte onto the separator, and the contact angle tester acquisition system automatically recorded the droplet profile and the contact of the separator. The recorded data was then processed.

[0204] 2. Battery cycle test:

[0205] At 25±2℃, the battery was charged at 1C constant current and constant voltage to 2.5V, and the cutoff current was 0.05C; it was rested for 30 min, and then discharged at 1C to 1.0V, and the above process was continued until the capacity retention rate of the battery was 80%, and the cycle number of the battery was recorded (when the cycle number was less than the number, the capacity retention rate was not less than 80%), wherein the capacity retention rate = the discharge capacity of the Nth cycle / the discharge capacity of the first cycle, and the cycle number was recorded.

[0206] The test results are shown in Table 1 below.

[0207] Table 1

[0208]

[0209] As can be seen from Table 1, the carbon nanometer microspheres and the electrostatic spinning preparation composite diaphragm have high tensile strength and elongation at break, high mechanical strength, the composite diaphragm has high specific surface area and porous structure, can be used as ion transmission channel, reduces the transmission resistance of electrolyte in the diaphragm, and simultaneously the good liquid affinity improves the electrolyte wettability, and further prolongs the cycle life.

[0210] In summary, the present application has the following advantages:

[0211] (1) The electrode assembly provided by the present application introduces a high-performance diaphragm, which improves the puncture resistance and ion conductivity of the diaphragm through the good interaction of carbon nanometer porous microspheres and polymers: on the one hand, the hydroxyl and / or amino groups on the surface of the carbon nanometer porous microspheres prepared from polypeptides can form strong interfacial bonding with polymers (such as PVDF, PVA, etc.) through hydrogen bonding and electrostatic interaction, thereby improving the elongation at break of the composite fiber, and the carbon nanometer porous microspheres as fillers are dispersed in the functional layer of the diaphragm, which can form a "rigid skeleton" to significantly improve the puncture resistance of the diaphragm, thereby reducing the risk of short circuit caused by electrode expansion or dendrite growth during charging and discharging; on the other hand, the carbon nanometer porous microspheres have abundant pores, although the pores are not connected, but the high specific surface area can store a large amount of electrolyte through physical adsorption or capillary action, realize good adsorption of electrolyte, improve the electrolyte retention of the diaphragm, thereby improve the interfacial compatibility and wettability of the interface, inhibit the growth of lithium dendrites, and the retention of electrolyte in the pores can reduce the loss of electrolyte, maintain the ion conduction efficiency of the diaphragm area (especially in the low humidity or electrolyte consumption scenario after cycling), and improve the ion conductivity.

[0212] (2) The present application can further enhance the compatibility with electrolyte, reduce the interfacial impedance, and promote the rapid migration of lithium ions at the diaphragm-electrolyte interface by modifying the surface of the carbon nanometer porous microspheres with lithium affinity (introducing polar groups such as hydroxyl and carboxyl groups).

[0213] (3) The preparation method provided by the present application is simple, mild and easy to control, the raw material cost is low, it is suitable for large-scale commercial use, and has wide application prospect.

[0214] The part not described in detail in the present application is the technology known to those skilled in the art.

[0215] The basic principles of the present application are described above in conjunction with specific embodiments, but it should be pointed out that the advantages, advantages, effects, etc. mentioned in the present application are only examples and not limitations, and these advantages, advantages, effects, etc. cannot be considered as the must-have of each embodiment of the present application. In addition, the above specific details are only for the purpose of example and for the purpose of understanding, and are not limited to the present application, and the above specific details are not limited to the present application.

[0216] In the above description of the specification, the description referring to the terms "one embodiment", "another embodiment", and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment are included in at least one embodiment of the present application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples, without contradiction. In addition, it should be noted that in the specification, the terms "first", "second" are for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0217] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrode assembly, characterized by, The application relates to a separator for a lithium ion battery, which comprises a positive electrode, a negative electrode and a separator between the positive electrode and the negative electrode; the separator comprises a base film and a functional layer arranged on one side surface of the base film close to the negative electrode; the functional layer comprises composite fibers formed by electrospinning of an electrospinning solution comprising carbon nanometer porous microspheres and a polymer on one side surface of the base film and drying; the carbon nanometer porous microspheres comprise a polar group obtained by hydrothermal reaction of a solution comprising a polypeptide, and the polar group comprises at least one of a hydroxyl group, an amino group and a carboxyl group; the polymer comprises at least one of polyvinylidene fluoride, polyvinyl alcohol, polyethylene terephthalate, polyvinylpyrrolidone, polyimide and polyethylene oxide; the concentration of the carbon nanometer porous microspheres in the electrospinning solution is 1wt%-5wt%; and the weight average molecular weight of the polymer is 200,000-1,000,000. The particle size of the carbon nanometer porous microspheres is 100nm-2000nm.

2. The electrode assembly of claim 1, wherein, The average diameter of the composite fibers is 200nm-3000nm.

3. The electrode assembly of claim 1, wherein, The coverage area of the functional layer is greater than the area of the negative electrode; and the width of the functional layer beyond the negative electrode on one side is 2mm-3mm. The porosity of the functional layer is greater than 40%. The elongation at break of the separator is greater than 365%.

4. The electrode assembly of claim 1, wherein, The thickness of the separator is 10-20mu m. The thickness of the base film is 5-10mu m. The thickness of the functional layer is 5-10mu m. The application further relates to a preparation method of the separator.

5. A method of producing an electrode assembly as claimed in any one of claims 1 to 4, characterized by a) dissolving a polypeptide in a first solvent to perform hydrothermal reaction to obtain carbon nanometer porous microspheres; the first solvent comprises at least one of water, N, N-dimethylformamide, N-methylpyrrolidone and hexafluoroisopropanol; the mass ratio of the polypeptide to the first solvent is (1-5):100; b) dissolving a polymer in a second solvent, adding the carbon nanometer porous microspheres obtained in step a) to perform dispersion to obtain an electrospinning solution; the second solvent comprises at least one of N, N-dimethylformamide, N-methylpyrrolidone and hexafluoroisopropanol; the mass ratio of the polymer to the second solvent is (10-15):100; and the concentration of the carbon nanometer porous microspheres in the electrospinning solution is 1wt%-5wt%; c) electrospinning the electrospinning solution obtained in step b) on one side surface of a base film, drying to form a functional layer, and then performing hot pressing to obtain a separator; d) assembling the separator obtained in step c) with a positive electrode and a negative electrode to obtain an electrode assembly. In step a):

6. The production method according to claim 5, wherein The polypeptide comprises at least one of collagen peptide, fish protein peptide and whey protein peptide; The pressure of the hydrothermal reaction is 5-10MPa, the temperature is 160-220 DEG C, and the time is 12-24h; After the hydrothermal reaction, the reaction mixture is cooled to room temperature, and then filtration, washing and drying are sequentially performed to obtain the carbon nanometer porous microspheres. In step b):

7. The preparation method according to claim 5, characterized in that, ​ The polymer comprises at least one of polyvinylidene fluoride, polyvinyl alcohol, polyethylene terephthalate, polyvinylpyrrolidone, polyimide, and polyethylene oxide; And / or, the dispersion process comprises vortex mixing for 0.5 min to 1.5 min, then dispersing under ultrasonic conditions at 200 W to 400 W for 30 min to 60 min, and finally vacuum defoaming at 20°C to 40°C for 20 min to 40 min to obtain the electrospinning solution. And / or, the viscosity of the electrospinning solution is 1000 mPa·s to 3000 mPa·s.

8. The preparation method according to claim 5, characterized in that, In step c): The electrospinning process comprises the following steps: cleaning and drying the base film, fixing it on a rotating roller, spraying the electrospinning solution through a spinneret, and moving the spinneret uniformly and reciprocally on one side of the surface of the base film for spinning; the rotating speed of the rotating roller is 0 rpm to 500 rpm; and / or, the inner diameter of the spinneret is 0.06 mm to 0.5 mm; and / or, the distance between the spinneret and the rotating roller is 10 cm to 20 cm; and / or, the positive voltage at the spinneret is 15 KV to 25 KV, and the negative voltage at the rotating roller is -1 KV to -5 KV; and / or, the flow rate of the electrospinning solution is 0.5 mL / h to 2 mL / h; and / or, the spinning time is 1 h to 5 h; and / or, the thickness of the spinning is 10 μm to 30 μm; And / or, the drying process is carried out in a fume hood, and the drying time is 20 h to 30 h; And / or, the temperature of the hot pressing is 50°C to 90°C, and the time is 5 min to 15 min.

9. A battery, characterized by The electrode assembly prepared by the preparation method of any one of claims 5 to 8.

10. An electrical device, characterized by The battery of claim 9. The battery of claim 9.

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