Secondary battery monomer, preparation method of secondary battery monomer and power utilization device

Abstract

The invention provides a secondary battery monomer, which comprises a positive plate, a negative current collector, an electrolyte and a diaphragm, and is characterized in that the diaphragm comprises a flat layer, the flat layer provides the surface of at least one side of the diaphragm, the pore diameter of the flat layer is 50-200nm, the pore pitch is 10-30nm, a preparation method of the secondary battery monomer, and a corresponding electric device.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a secondary battery cell, a method for preparing the secondary battery cell, and an electrical device. Background Technology

[0002] With the development of battery technology, problems such as uneven ion distribution inside the battery and defects at the negative electrode interface have gradually emerged. This makes it easier for dendrites to propagate and grow after metal deposition on the negative electrode, exacerbating internal short circuits. When an internal short circuit occurs in a battery, it can easily lead to a reduction in battery cycle life and storage life.

[0003] To address this problem, existing technologies have taken two approaches: firstly, increasing the membrane thickness to slow down metal dendrite growth and penetration time; and secondly, improving the membrane material and performing surface nano-treatment to make it harder for dendrites to penetrate. However, neither of these methods can effectively improve the metal dendrite growth problem; they can only slow down the internal short-circuit time. Summary of the Invention

[0004] This application provides a secondary battery cell, a method for preparing the secondary battery cell, and an electrical device to improve the cycle life and storage life of the battery.

[0005] The first aspect of this application relates to a secondary battery cell, comprising a positive electrode, a negative current collector, an electrolyte, and a separator, characterized in that the separator comprises a planarization layer, the planarization layer providing a surface of at least one side of the separator, the planarization layer having a pore size of 50-200 nm and a pore spacing of 10-30 nm, a method for its preparation, and a corresponding electrical device.

[0006] The second aspect of this application relates to a method for preparing a secondary battery cell, the secondary battery cell comprising a positive electrode, a negative current collector, an electrolyte, and a separator. The preparation method includes a process for preparing the separator, wherein the process for preparing the separator includes a method for preparing a planarization layer. The method for preparing the planarization layer includes: mixing materials comprising a polymer and a pore-forming agent to form a planarization layer raw material; coating the planarization layer raw material onto a base film; and removing the pore-forming agent. The pore size of the planarization layer is 50-200 nm, and the pore spacing is 10-30 nm.

[0007] Another aspect of this application relates to an electrical device comprising the secondary battery cell described in the first aspect. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0009] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0010] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0011] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0012] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0013] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0014] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0015] The accompanying drawings are not drawn to scale.

[0016] Explanation of reference numerals in the attached figures:

[0017] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery cell; 51 Housing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0018] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0019] The following detailed description, with appropriate reference to the accompanying drawings, discloses the secondary battery cell, the method for preparing the secondary battery cell, and embodiments of the power supply device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0020] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0022] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0023] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0024] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0025] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0026] [Secondary battery cell]

[0027] In this embodiment of the application, the secondary battery cell can be a secondary battery, which refers to a secondary battery cell that can be recharged to activate the active material and continue to be used after the secondary battery cell has been discharged.

[0028] The secondary battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0029] A typical secondary battery cell includes an electrode assembly. This assembly comprises a positive electrode, a negative current collector, and a separator, with the separator positioned between the negative current collector and the positive electrode. During the charging and discharging process of a secondary battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative current collectors. The separator, located between the positive and negative current collectors, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0030] The first embodiment of this application provides a secondary battery cell, including a positive electrode, a negative current collector, an electrolyte, and a separator. The separator includes a planarization layer, which provides at least one surface of the separator. The planarization layer has a pore size of 50-200 nm and a pore spacing of 10-30 nm.

[0031] Aperture diameter and spacing test: Aperture diameter and spacing were measured using SEM images at magnification of 5000kx or 10000kx to obtain aperture diameter distribution data. Spacing was measured using the same method as aperture diameter, employing SEM images.

[0032] This application includes a planarization layer in the separator, which has a defined pore size and pore spacing, so that the flux of the obtained active ions during diffusion is uniform, thereby achieving smooth active metal deposition while inhibiting active metal dendrite growth and penetration, ultimately improving battery cycle life and storage life.

[0033] In some embodiments, the porosity of the planarization layer is 60-70%, and the thickness on one side is 1-5 μm. By giving the planarization layer a defined porosity and thickness, the ionic conductivity of the separator is improved. The separator thickness / porosity / permeability / separator ionic conductivity analysis preliminarily characterizes the ion transport rate; the electrical properties are reflected by ΔU and DCR.

[0034] Porosity refers to the proportion of pore volume to the total volume in a material, calculated as porosity = (V2 - V1) / V2 * 100%. V1 represents the true volume of the sample (cm³). 3 The true volume is tested using the following method: a closed testing system is used, helium gas is introduced according to a procedure, and the pressure of the gas in the sample chamber and expansion chamber is measured. The true volume is then calculated according to Bohr's Law (PV = nRT). V² represents the apparent volume, which is calculated using the formula V² = S * H ​​* A, where S represents the area (cm²). 2 H represents thickness (cm), and A represents the number of samples (EA). Thickness test: Thickness H is measured using an ion-polished cross-section.

[0035] In some embodiments, the contact angle of the electrolyte on the leveling layer is 30° to 35°. In some embodiments, the leveling layer and the electrolyte have the aforementioned defined contact angle, resulting in good wettability of the electrolyte on the diaphragm and thus better electrolyte retention.

[0036] In some embodiments, the permeability of the leveling layer is 70-80 seconds / 100 mL. The leveling layer's defined permeability further improves the flux of alkali metal ion diffusion.

[0037] Air permeability test method: the time it takes for 100cc of air to pass through a unit area sample under unit pressure.

[0038] In some embodiments, the planarization layer comprises a polymer, which includes polar functional groups. The aforementioned polar functional groups are particularly beneficial for interaction with electrolyte solvent molecules. The polar functional groups in the polymer can be introduced by blending; optionally, polymers with polar functional groups (acrylic acid, acrylonitrile) can be blended into polyethersulfone to form a polymer with polar functional groups such as carboxyl groups.

[0039] In some embodiments, the polar functional group includes one or more of carbonyl, ester, carboxyl, nitrile, hydroxyl, fluorool, amino, carbonyl, epoxy, and imino groups.

[0040] In some embodiments, the planarization layer comprises a polar polymer. The electrolyte solvent is a polar solvent; polar functional groups are affinity for polar solvents, weakening the solvation effect between solvent molecules and cations in the electrolyte. The polar polymer can interact with electrolyte solvent molecules (ether solvents, such as ethylene glycol dimethyl ether, 1,3-dioxolane (DOL), etc.), weakening the binding energy between solvent molecules and cations (0.4 eV → 0.25 eV), allowing more anions to participate in solvation, forming a weakly solvated structure, and constructing an inorganic SEI film at the negative electrode (XPS can characterize the group binding on the SEI surface, showing more anionic structural peaks, such as PF6). - ClO4 -(And organic structures such as RCOONa have a smaller peak area ratio). Weakening the interaction between cations and solvents allows more anions to enter the solvation sheath, forming more contact ion pairs and ion aggregates. The weak solvation structure dominated by anions reduces the interaction between solvent and ions, reducing solvent decomposition on the negative electrode surface, which means reducing the organic SEI film component and increasing the formation of inorganic SEI.

[0041] In some embodiments, the polar polymer includes one or more of polyethersulfone, polybenzimidazole, poly(vinylidene fluoride-copoly-hexafluoropropylene, PVDF-HFP), cellulose esters, polyimides, acrylate polymers, styrene-acrylonitrile copolymers, ethylene-vinyl alcohol polymers, polyamides, polyesters, polycarbonates, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymers, polyvinylidene chloride, polyphosphates, and polyurethanes.

[0042] In some embodiments, the planarization layer comprises polyethersulfone. Polyethersulfone, PVDF-HFP, acrylate polymers, cellulose esters, polyimides, polyurethanes, styrene-acrylonitrile copolymers, and polycarbonates are preferred polar polymers for implementing the technical solutions of this invention.

[0043] In some embodiments, the diaphragm further includes a base membrane, a ceramic coating, and a polymer adhesive coating, wherein the ceramic coating is between the base membrane and the polymer adhesive coating, and the polymer adhesive coating is between the ceramic coating and the leveling layer.

[0044] In some embodiments, the base membrane material can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base membrane can be a commonly used base membrane in the art, particularly produced using a dry bistretching process, with the addition of 0.5%-5% organophosphate as a nucleating agent to promote β-crystal formation. During stretching, a crystal transformation occurs, forming micropores on the base membrane, achieving a porosity of 43%-50%.

[0045] In some embodiments, the structure and composition of the ceramic coating and the polymer adhesive layer can be referred to the prior art, and will not be repeated here.

[0046] [Preparation method of the leveling layer]

[0047] The following exemplarily illustrates a method for preparing a planarization layer, the method comprising:

[0048] Materials including polymers and pore-forming agents are mixed to form a smoothing layer raw material;

[0049] The smoothing layer material is coated onto the base film;

[0050] Remove the pore-forming agent; the pore size of the leveling layer is 50-200 nm, and the pore spacing is 10-30 nm.

[0051] In some embodiments, the pore-forming agent includes one or more of hydroxyapatite, dimethyl carbonate, polyethylene glycol, citric acid, and tartaric acid.

[0052] In some embodiments, the pore-forming agent contains 0.3%-1% by mass in the leveling layer material. The pore-forming agent decomposes and volatilizes during sintering, forming a uniformly distributed pore structure.

[0053] In some embodiments, the leveling layer material is coated onto the base film using a gravure roller coating process, with a gravure roller speed / base film speed ratio of 1.0 to 1.3 and a doctor blade pressure of 1 to 4 kgf.

[0054] The polymer used in the preparation method can be any of the polymers included in the planarization layer described above. These polymers can be commercially available or synthesized. For example, 4,4'-dichlorodiphenyl sulfone (DCS) and bisphenol S (SDP) can be used as raw materials and reacted at 210°C-220°C for 7-8 hours to obtain a polyethersulfone resin with a high degree of polymerization.

[0055] Electrolyte

[0056] The electrolyte acts as a conductor of ions between the positive electrode and the negative current collector. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements.

[0057] In some embodiments, the electrolyte comprises an ether solvent, wherein the ether solvent includes one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, diisopropyl ether, dibutyl ether, diethylene glycol dibutyl ether, 1,4-dimethoxybutane, 1,4-diethoxybutane, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, 15-crown ether-5, 12-crown ether-4, 18-crown ether-6, and diphenyl ether.

[0058] In some embodiments, when the secondary battery cell is a sodium-ion battery, the electrolyte salt may be selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium difluorosulfonamide, sodium ditrifluoromethanesulfonamide, sodium trifluoromethanesulfonate, sodium difluorophosphate, sodium difluorooxalate borate, sodium dioxalate borate, sodium difluorodioxalate phosphate, and sodium tetrafluorooxalate phosphate.

[0059] In some embodiments, the electrolyte may optionally include additives. As examples, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0060] [Negative electrode current collector]

[0061] In some embodiments, the side of the diaphragm with the smooth layer faces the negative electrode current collector. The negative electrode current collector is used as the negative electrode current collector.

[0062] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0063] In other embodiments, the negative electrode current collector typically includes a current collector body and a conductive coating. The conductive coating may be disposed on at least one side of the current collector body. The conductive coating basically does not contain negative electrode active material, but may include a small amount of carbon material. However, the carbon material forms a thin coating and cannot play the role of negative electrode active material. In this embodiment, the negative electrode current collector can be an electrode without a negative electrode active material layer.

[0064] In some embodiments, the negative current collector includes a copper foil and a conductive coating disposed on the copper foil.

[0065] In some embodiments of this application, no negative electrode active material is provided in the negative electrode. During charging, active ions are deposited on the surface of the negative electrode current collector and used as the negative electrode material. The conductive coating provided above helps to improve the uniformity of active ion deposition on the surface of the negative electrode current collector.

[0066] Negative electrode current collector secondary battery cell [positive electrode plate]

[0067] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0068] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0069] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0070] In some embodiments, the secondary battery cell is a sodium-ion battery, and the positive electrode active material can be a positive electrode active material known in the art for sodium-ion batteries. As an example, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds, Prussian blue compounds, etc., and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries can also be used. For example, as an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, 0 <x≤1。

[0071] As an optional technical approach in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The valence state. Polyanionic compounds can also have sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl, and Br. Polyanionic compounds can also have sodium ions, tetrahedral (YO4) valence states. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n-Valence state: Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl, and Br. Examples of polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' is one or more of V, Fe, Mn, and Ni), and Na3(VO4)2(PO4)3. y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0072] As an optional technical approach in this application, the polyanionic compound can be Na... x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q d Wherein, element A represents an alkali metal element that substitutes for element Na, element M represents a metal element that substitutes for element V, element D represents a dopant element that substitutes for element P, and element Q represents a dopant element that substitutes for element F. Element D includes at least one of Si and S, and element Q includes at least one of Cl and O; 3.5 ≤ x ≤ 4.5, 0 ≤ a ≤ 0.15x, 0.8 ≤ y ≤ 1.1, 0 ≤ b ≤ 0.3y, 0 ≤ c ≤ 0.15, 0.8 ≤ z ≤ 1.1, 0 ≤ d ≤ 0.2z. Optionally, element A includes at least one of K and Li; element M includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0073] As an optional technical approach in this application, the polyanionic compound can be Na... x R y (PO4)2P2O7, wherein x = 3.5-4.5, y = 2.75-3.25, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0074] As an optional technical approach in this application, the polyanionic compound can be Na... 4+x R 3-y P 4-m O 15 / C; wherein, 0 < x < 0.5, 0 < y ≤ 0.5, 0 < m ≤ 0.2, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0075] Prussian blue compounds can be a class of compounds having sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the Prussian blue compound is Na a Me b Me’ c (CN)6, where Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a ≤ 2, 0 < b < 1, and 0 < c < 1.

[0076] In some embodiments, the positive electrode active material includes at least one of a sodium-containing layered oxide, a polyanionic sodium compound, and a Prussian blue sodium compound.

[0077] In some embodiments, the sodium-containing layered oxide is an iron-manganese-based layered oxide, specifically including at least one of a nickel-iron-manganese-based layered oxide and a copper-iron-manganese-based layered oxide.

[0078] During the charge and discharge process of the battery, the intercalation and deintercalation and consumption of active ions (Na+) will occur, and the molar content of Na is different when the battery is discharged to different states. In the listing of the positive electrode active material in this application, the molar content of Na is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Na will change after charge and discharge cycles.

[0079] In the listing of the positive electrode active material in this application, the molar content of oxygen is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of oxygen will fluctuate.

[0080] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0081] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0083] When the secondary battery is a sodium-ion secondary battery, as an example, the positive electrode active material of the sodium-ion secondary battery may include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0084] In some embodiments, the positive electrode, negative electrode current collector, and separator can be fabricated into an electrode assembly through a winding process or a stacking process.

[0085] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative current collector are wound into a wound structure.

[0086] In some implementations, the electrode assembly is a stacked structure.

[0087] As an example, multiple positive electrode plates and multiple negative current collectors can be set, and multiple positive electrode plates and multiple negative current collectors can be stacked alternately.

[0088] As an example, multiple positive electrode sheets can be provided, and the negative current collector is folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0089] As an example, both the positive electrode sheet and the negative electrode current collector are folded to form multiple stacked folded segments.

[0090] As an example, multiple separators can be provided, each positioned between any adjacent positive electrode or negative current collector.

[0091] As an example, the separator can be continuously installed between any adjacent positive electrode or negative current collector by folding or rolling.

[0092] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0093] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0094] In some embodiments, the secondary battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0095] As an example, the secondary battery cell can be a cylindrical secondary battery cell, a prismatic secondary battery cell, a pouch secondary battery cell, or a secondary battery cell of other shapes. Prismatic secondary battery cells include square-shell secondary battery cells, blade-shaped secondary battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0096] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0097] Figure 1 The example shown is a square-structured secondary battery cell 5.

[0098] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and an end cap 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the end cap 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode current collector, and separator can be formed into an electrode assembly 52 via a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single secondary battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0099] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0100] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the secondary battery cell.

[0101] As an example, the internal pressure or temperature of a secondary battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the secondary battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is destroyed, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative current collector, electrolyte, and separator in the secondary battery cell.

[0102] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0103] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0104] The term "actuation" as used in this application refers to the pressure relief mechanism being activated or undergoing a certain state, thereby releasing the internal pressure and temperature of the secondary battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is actuated, the high-temperature, high-pressure substances inside the secondary battery cell are discharged as waste from the actuated portion. This method allows for pressure and temperature relief of the secondary battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0105] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for discharging gas from inside the secondary battery cell.

[0106] The emissions from secondary battery cells mentioned in this application include, but are not limited to: electrolytes, dissolved or broken positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0107] In some implementations, the secondary battery cells can be assembled into a battery module. The number of secondary battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0108] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary battery cells 5 can be fixed in place using fasteners.

[0109] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple secondary battery cells 5 are received.

[0110] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0111] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0112] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0113] As the electrical device, a single secondary battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0114] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0115] Secondary battery cell, secondary battery cell, secondary battery cell, secondary battery cell, negative electrode current collector, secondary battery cell, secondary battery cell, secondary battery cell, secondary battery cell, secondary battery cell, secondary battery cell.

[0116] [Example]

[0117] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0118] The tests used in this invention are as follows:

[0119] Diaphragm coating composition confirmation: Infrared spectroscopy, according to GB / T6040-2002.

[0120] Solvated structure determination: XPS test, performed according to GB / T 33502.

[0121] Diaphragm mechanical strength: Mechanical strength is tested using a tensile testing machine according to GB / T 228-2002.

[0122] Negative electrode metal deposition method: Scanning electron microscopy (SEM) test, according to JY / T010-1996.

[0123] The test method for 25℃ cycling performance is as follows:

[0124] Capacity calibration

[0125] 1) Rest for 30 minutes

[0126] 2) 0.33C DC 1.5V

[0127] 3) Rest for 30 minutes

[0128] 4) 0.33C CC 3.65V CV 0.05C

[0129] 5) Rest for 30 minutes

[0130] 6) 0.33C DC 1.5V C0 (Record the second capacitance value as C0)

[0131] 7) Rest for 30 minutes

[0132] 8) Repeat steps 4-7 twice in total.

[0133] Cyclic capability confirmed:

[0134] 1) Rest 30min 25 30

[0135] 2) 0.33Cn DC 1.5V 25 30

[0136] 3) Rest 30min 25 30

[0137] 4)0.33Cn CC 3.65V CV 0.05Cn 25 30

[0138] 5) Rest 30min 25 30

[0139] 6) 0.33Cn DC 1.5V 25 30

[0140] 7) Rest 30min 25 30

[0141] 8)0.33Cn CC 3.65V CV 0.05Cn 25 30

[0142] 9) Rest 30min 25 30

[0143] 10) 0.04Cn DC 1.5V 25 30

[0144] 11) Rest 30min 25 30

[0145] 12) 1Cn CC 3.65V CV 0.05Cn 25 30 Cycle segment

[0146] 13) Rest 30min 25 30

[0147] 14) 1Cn DC 1.5V 25 30F (This step is used to calculate Fading)

[0148] 15) Rest for 30 minutes at 25-30V (This step is to confirm an internal short circuit)

[0149] 16) Repeat steps 12-15, repeating 98 times.

[0150] 17) Repeat steps 3-16 until the cutoff condition ≤80% SOH is met.

[0151] Example

[0152] The smoothing layer was prepared using the polymer and pore-forming agent described above, and its relevant parameters were measured, as shown in the table below.

[0153] Furthermore, the preparation of each component of the battery of the present invention is as follows.

[0154] Positive electrode sheet: 93.8 wt% of positive electrode active material, 3.0 wt% of conductive agent (conductive carbon black), 2.5 wt% of binder (polyvinylidene fluoride), 0.3 wt% of dispersant, and 0.4 wt% of residual alkali remover (optionally salicylic acid, maleic anhydride, or oxalic acid) are mixed, then N-methylpyrrolidone is added and stirred to disperse, forming a positive electrode slurry. The raw materials are mixed together to prepare the slurry, which needs to be adjusted to a certain viscosity before coating. After stirring the prepared oil-based slurry, NMP solvent is added to adjust the slurry viscosity to 8000-15000 mPa·s. The prepared slurry does not separate into layers. Then, the slurry coating weight is controlled at 200 mg / 1540.25 cm² using a double-sided, double-cavity coating device. 2 The coating is applied to Al foil, and after double-sided coating, it is dried, cold-pressed, slit, and prepared to obtain the positive electrode sheet.

[0155] Negative electrode current collector: This application adopts a negative electrode-free structure, and a carbon nanotube (CNT) coating is coated on both sides of Cu foil as an alkali metal deposition current collector, with a single-sided coating thickness of about 2-4 μm.

[0156] Separator: A base membrane for the separator is prepared using polyethylene (PE), and it also includes a leveling layer prepared as described above. The leveling layer is prepared using the polymer and pore-forming agent described above, and its relevant parameters are measured, as shown in the table below.

[0157] Electrolyte: The solvent used is ethylene glycol dimethyl ether, and the salt used is 1M NaPF6.

[0158] Composition: The positive electrode, separator, and negative current collector are stacked in sequence, with the separator positioned between the anode and cathode for isolation, and then wound to obtain a bare cell. The bare cell is placed in an outer package, injected with prepared electrolyte, and then sealed, filled, formed, and vented to obtain a negative electrode-free alkali metal battery.

[0159] The following shows key information about the embodiments.

[0160] The following provides further information about the embodiments.

[0161] By comparing the data from the above embodiments and comparative examples, it can be seen that the battery using the planarization layer in the technical solution of this invention exhibits significantly superior cycle performance. Specifically, the technical solution of this invention utilizes various polymers such as polyethersulfone, acrylic polymers, cellulose esters, PVDF-HFP, polyimides, polyurethanes, styrene-acrylonitrile copolymers, and polycarbonates, achieving excellent cycle performance while controlling the pore size and spacing of the planarization layer within specified ranges. In contrast, the technical solution using polyethersulfone shows significantly deteriorated cycle performance when the pore size and spacing are within the range defined by this invention. Furthermore, the technical solution of this invention achieves the required pore size and spacing by controlling the amount of pore-forming agent used.

[0162] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery cell, comprising a positive electrode, a negative current collector, an electrolyte, and a separator, characterized in that, The diaphragm includes a planarization layer that provides a surface on at least one side of the diaphragm. The planarization layer has a pore size of 50-200 nm and a pore spacing of 10-30 nm.

2. The secondary battery cell according to claim 1, characterized in that, The porosity of the leveling layer is 60-70%, and the thickness on one side is 1-5 μm.

3. The secondary battery cell according to claim 1 or 2, characterized in that, The contact angle of the electrolyte on the flattening layer is 30°-35°.

4. The secondary battery cell according to any one of claims 1 to 3, characterized in that, The air permeability of the leveling layer is 70-80 seconds / 100mL.

5. The secondary battery cell according to any one of claims 1 to 4, characterized in that, The planarization layer comprises a polymer, and the polymer includes polar functional groups.

6. The secondary battery cell according to claim 5, characterized in that, The polar functional groups include one or more of the following: carbonyl, ester, carboxyl, nitrile, hydroxyl, fluorool, amino, carbonyl, epoxy, and imino.

7. The secondary battery cell according to any one of claims 1 to 6, characterized in that, The leveling layer comprises a polar polymer.

8. The secondary battery cell according to claim 7, characterized in that, The polar polymers include one or more of the following: polyethersulfone, polyetherketone, polybenzimidazole, poly(vinylidene fluoride-copoly-hexafluoropropylene), cellulose esters, polyimides, acrylate polymers, styrene-acrylonitrile copolymers, ethylene-vinyl alcohol polymers, polyamides, polyesters, polycarbonates, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymers, polyvinylidene chloride, polyphosphates, and polyurethanes.

9. The secondary battery cell according to any one of claims 1 to 8, characterized in that, The diaphragm further includes a base membrane, a ceramic coating, and a polymer adhesive coating, wherein the ceramic coating is between the base membrane and the polymer adhesive coating, and the polymer adhesive coating is between the ceramic coating and the leveling layer.

10. The secondary battery cell according to any one of claims 1 to 9, characterized in that, The electrolyte comprises an ether solvent, wherein the ether solvent includes one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, diisopropyl ether, dibutyl ether, diethylene glycol dibutyl ether, 1,4-dimethoxybutane, 1,4-diethoxybutane, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, 15-crown ether-5, 12-crown ether-4, 18-crown ether-6, and diphenyl ether.

11. The secondary battery cell according to any one of claims 1 to 10, characterized in that, The side of the diaphragm with the flat layer faces the negative electrode current collector.

12. The secondary battery cell according to any one of claims 1 to 11, characterized in that, The negative current collector includes a copper foil and a conductive coating disposed on the copper foil.

13. The secondary battery cell according to any one of claims 1 to 11, characterized in that, The positive electrode sheet includes a positive electrode active material, namely sodium transition metal oxide, polyanionic compound, and Prussian blue compound.

14. A method for preparing a secondary battery cell, the secondary battery cell comprising a positive electrode, a negative current collector, an electrolyte, and a separator, the preparation method comprising a process for preparing the separator, wherein, The process of preparing the diaphragm includes a method for preparing a planarization layer, the method of preparing the planarization layer including: Materials including polymers and pore-forming agents are mixed to form a smoothing layer raw material; The smoothing layer material is coated onto the base film; Remove the pore-forming agent; the pore size of the leveling layer is 50-200 nm, and the pore spacing is 10-30 nm.

15. An electrical appliance, characterized in that, Includes any one of the secondary battery cells according to claims 1-14.

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