Negative electrode reinforcing film for secondary battery, secondary battery, and electric device

Abstract

The utility model relates to a negative electrode reinforcing membrane for a secondary battery, which comprises at least one structural layer in contact with a negative electrode substrate layer, and the structural layer is at least partially embedded into the negative electrode substrate layer. According to the utility model, the structure layer forms the convex-concave structure on the surface of the negative electrode substrate layer, so that the specific surface area of the negative electrode plate can be effectively increased, the charge-discharge capacity of the electrode and the compatibility to side reactions are improved, and meanwhile, the rate capability and the capacity retention ratio of the battery are improved.

Description

Technical Field

[0001] The utility model relates to the field of secondary batteries, in particular to a negative electrode enhancement film for a secondary battery, a secondary battery and an electrical device. Background Art

[0002] With the rapid development of society, the energy crisis and environmental problems caused by the burning of fossil raw materials are becoming increasingly severe. It is urgent to develop efficient and reusable energy storage materials and improve the utilization rate of existing renewable energy. Alkali metal and alkaline earth metal secondary batteries such as lithium secondary batteries and sodium secondary batteries have the advantages of long cycle life, high energy density, low self-discharge rate, good thermal stability, and no memory effect. They have become a research hotspot in the field of new energy. Alkali metal and alkaline earth metal secondary battery negative electrode materials usually include carbon-based negative electrode materials, silicon-based negative electrode materials, tin-based negative electrode materials, metal negative electrode materials, etc. Different materials have different performance characteristics. Taking lithium secondary batteries as an example, the main negative electrode materials of lithium secondary batteries are modified graphite, mesophase carbon microbeads, etc. The gram capacity of these materials is low, and the theoretical specific capacity of graphite is only 372mAh / g, which limits the further improvement of the energy density of lithium secondary batteries. The theoretical specific capacity of silicon-based negative electrode materials is as high as 4200mAh / g (Li 22 Si5) has a moderate electrode potential. Silicon reserves are abundant and environmentally friendly. However, silicon undergoes a dramatic volume expansion effect (over 300%) during lithium insertion, causing the electrode active material to easily detach and pulverize during charge and discharge. This continuously forms an electrolyte interface (SEI) film within the electrolyte, reducing charge and discharge efficiency, continuously consuming the electrolyte, increasing the battery's internal resistance, and causing capacity decay. Silicon's poor conductivity has severely hindered its application as a negative electrode material for lithium secondary batteries.

[0003] Metal anode materials have high capacity and can significantly increase the energy density of battery systems, extending battery life. Alkali and alkaline earth metal anode materials have garnered the most attention. For example, current industry efforts to increase the specific surface area of ​​secondary battery anodes, such as sodium metal anodes, still face technical challenges. Utility Model Content

[0004] To address the problems existing in the prior art, the present invention provides a negative electrode reinforcement film for a secondary battery. This film effectively increases the specific surface area of ​​the metal negative electrode, reduces the current density of the negative electrode during charge and discharge, improves the electrode's charge and discharge capacity and compatibility with battery side reactions, reduces the thickness of the negative electrode protective film (SEI), prevents excessive SEI passivation of the negative electrode, and inhibits the formation of metal dendrites. Furthermore, the negative electrode reinforcement film reduces excessive SEI formation under high temperature conditions or high current density, thereby improving the capacity retention and electrochemical performance of the secondary battery.

[0005] According to a first aspect of the present invention, a negative electrode reinforcement membrane for a secondary battery is provided. The negative electrode reinforcement membrane includes at least one structural layer in contact with a negative electrode base layer, and the structural layer is at least partially embedded in the negative electrode base layer. The negative electrode base layer is an active layer. The active layer is composed of an active material. In this invention, the active material is a substance that undergoes a valence change during the charge and discharge process of the battery and participates in the charge transfer and current carrying process. For lithium batteries, this is lithium, and for sodium batteries, this is sodium.

[0006] In some embodiments of the present invention, the structural layer is a particle layer, the particle layer includes nanoparticles and / or microparticles, and at least a portion of the surface of at least a portion of the nanoparticles and / or microparticles is in contact with the negative electrode base layer.

[0007] In some embodiments of the present invention, the structural layer is a grid layer, which includes nanogrids and / or microgrids, and at least a portion of the surface of at least a portion of the nanogrids and / or microgrids is in contact with the negative electrode base layer.

[0008] In some embodiments of the present invention, the negative electrode base layer includes an alkali metal or its alloy, an alkaline earth metal or its alloy; preferably, the alkali metal or its alloy is sodium metal and / or its alloy, or the alkali metal or its alloy is lithium metal and / or its alloy.

[0009] In some embodiments of the present invention, the structural layer does not chemically react with the electrolyte. Preferably, the structural layer does not chemically react with the electrolyte or the active layer material.

[0010] In some embodiments of the present invention, the structural layer includes at least one component selected from non-metallic elements, oxides, fluorides, carbides, carbon materials, nitrides, and silicides.

[0011] In some embodiments of the present invention, the structural layer is provided in at least one of the following ways:

[0012] (1) The structural layer is arranged between the negative electrode base layer and the negative electrode current collector;

[0013] (2) The structural layer is provided between the negative electrode base layer and the separator;

[0014] (3) The structural layer is arranged on the side of the negative electrode base layer away from the negative electrode current collector;

[0015] (4) The structural layer is embedded in the negative electrode base layer in a discontinuous manner to form an integrated structure;

[0016] (5) The structural layer is disposed between the positive electrode sheet and the separator, and the structural layer abuts against the separator to be at least partially embedded in the negative electrode base layer;

[0017] (6) The structural layer is embedded in the isolation membrane in a discontinuous manner to form an integrated structure.

[0018] In some embodiments of the present invention, at least a portion of the nanoparticles and / or microparticles of the structural layer do not penetrate the negative electrode base layer, and a convex-concave structure is formed on the surface of the negative electrode base layer.

[0019] In some embodiments of the present invention, the structural layer further comprises the alkali metal compound.

[0020] In some embodiments of the present invention, the negative electrode reinforcement film includes two structural layers, and the two structural layers are both arranged on the same side of the negative electrode base layer or respectively arranged on both sides of the negative electrode base layer.

[0021] In some embodiments of the present invention, the two structural layers independently include any one or more combinations of nanoparticles, micron particles, nanogrids, and microgrids.

[0022] In some embodiments of the present invention, the thickness of the negative electrode enhancement film is 0.01 μm-100 μm.

[0023] In some embodiments of the present invention, the surface density of the negative electrode enhancement film is 0.01 mg / cm 2 -30mg / cm 2 .

[0024] In some embodiments of the present invention, the structural layer includes a median particle size D 50 Particles between 5 nm and 50 μm, preferably 20 nm and 50 μm.

[0025] According to a second aspect of the present invention, a lithium or sodium secondary battery is provided, comprising a positive electrode sheet, an electrolyte, a negative electrode sheet having a negative electrode base layer, and the negative electrode reinforcement film.

[0026] In some embodiments of the present invention, the negative electrode base layer is an active layer, and the selected material includes sodium metal or sodium alloy (in sodium batteries), or lithium metal or lithium alloy (in lithium batteries).

[0027] In some embodiments of the present invention, the structural layer further comprises a sodium or lithium compound.

[0028] In some embodiments of the present invention, the electrolyte contains at least one anion selected from fluorine-containing anions; preferably, at least one selected from bis(fluorosulfonyl)imide, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, difluorooxalatoborate, tetrafluoroborate, hexafluoroarsenate and difluorophosphate.

[0029] In some embodiments of the present invention, the electrolyte contains sodium ions or lithium ions as active materials.

[0030] According to a third aspect of the present invention, there is provided an electrical device comprising the lithium or sodium secondary battery.

[0031] Compared with the prior art, the negative electrode enhancement film layer of the present invention can increase the specific surface area of ​​the metal negative electrode plate, reduce the current density of the negative electrode during the battery charging and discharging process, and improve the ability of the negative electrode plate to tolerate side reactions, so as to be compatible with the effects of impurities, side reactions, and positive and negative electrode interactions that may exist in the secondary battery. In addition, the negative electrode enhancement film layer can improve the charge and discharge capacity of the electrode, and the average current density per unit area is greatly reduced, which is conducive to increasing the overcurrent range of the protective film (SEI), and is compatible with SEI with thicker or lower ionic conductivity; it reduces the polarization of the battery and improves the battery's rate performance; it is conducive to the formation of the alloy layer and promotes the alloying reaction of the negative electrode. At the same time, the nano- or micro-structured layer on the surface of the metal negative electrode plate reduces the probability of short circuit between the positive and negative electrodes, making the battery safer. In addition, the structural layer in the negative electrode enhancement film does not experience thermal shrinkage, which reduces the probability of thermal runaway of the battery. The negative electrode enhancement film can inhibit the excessive formation of SEI at high temperatures and further optimize the battery's capacity retention rate, kinetic characteristics, and service life. In the present invention, the structural layer improves the surface roughness of the negative electrode base layer, which can effectively increase the specific surface area of ​​the negative electrode plate, improve the electrode charging and discharging capacity and compatibility with side reactions (not only with side reactions occurring during the use of the battery, but also increase its compatibility with side reactions (such as polluting reactions) during battery manufacturing and static processing), and at the same time improve the battery's rate performance.

[0032] These and other features and advantages will become apparent from reading the following detailed description and referring to the associated drawings.It is to be understood that both the foregoing general description and the following detailed description are illustrative only and are not restrictive of the aspects claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of disposing the enhanced film on the current collector in a specific embodiment of the present invention.

[0034] Figure 2 It is a schematic diagram of arranging the enhancement film below the negative electrode plate in a specific embodiment of the present invention.

[0035] Figure 3 It is a schematic diagram of arranging the enhancement film above the negative electrode plate in a specific embodiment of the present invention.

[0036] Figure 4It is a schematic diagram of arranging the reinforcement film below the isolation film in a specific embodiment of the present invention.

[0037] Figure 5 It is a schematic diagram of setting the enhancement film in the negative electrode plate in a specific embodiment of the present invention.

[0038] Figure 6 It is a schematic diagram of disposing the reinforcement film in the isolation film layer in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be described in detail below with reference to the accompanying drawings, and the features of the present invention will be further apparent in the following specific description.

[0040] "Range" disclosed herein is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a particular parameter, it is understood that a range of 60-110 and 80-120 is also contemplated. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution. In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0042] In this utility model, unless otherwise specified, the terms "include" and "comprising" mentioned herein may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0043] In the description herein, unless otherwise indicated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by any of the following conditions: 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).

[0044] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0045] It should be noted that, in the description of this utility model, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0046] In the description of the present invention, the term "contact" includes direct or indirect contact or abutment. For example, the structural layer can directly contact the negative electrode sheet, or the two can contact / abut each other through a separator. The term "embedded" similarly includes direct or indirect embedding. For example, the structural layer can be directly embedded in the negative electrode sheet, or the structural layer can be embedded in the negative electrode sheet through a separator.

[0047] In the present invention, the negative electrode reinforcement film for a secondary battery includes at least one structural layer in contact with the negative electrode base layer in the negative electrode sheet of the secondary battery, and the structural layer is at least partially embedded in the negative electrode base layer. In some embodiments, the structural layer includes nanoparticles and / or microparticles, and at least a portion of the surface of at least a portion of the nanoparticles and / or microparticles is in contact with the negative electrode base layer. In some embodiments, the median particle size D of the nanoparticles and / or microparticles is 50 It is 5nm-50μm, 5nm-45μm, 10nm-40μm, 20nm-30μm or any numerical range consisting of the end values ​​of the above ranges. It should be emphasized that although the above numerical values ​​are listed in parallel, it does not mean that the numerical range consisting of any two of the above numerical values ​​as endpoints can obtain equivalent or similar performance. The same applies to the numerical ranges mentioned below. Regarding the preferred embodiment of the present invention, the selection is made only based on the specific discussion below and specific experimental data. In the optional embodiment of the present invention, it is preferred that 10nm≤D 50 ≤50μm. In this utility model, the median particle size D 50 When controlled within the above range, the particles can form a concave-convex morphology with sufficient depth or height on the surface of the negative electrode base layer, fully improving its specific surface area, reducing the current density of the negative electrode, improving tolerance to side reactions, inhibiting excessive formation of SEI under high temperature conditions, and the battery having ideal kinetic characteristics; at the same time, it can ensure that at least a portion of the particles will not completely penetrate the negative electrode base layer.

[0048] In some embodiments, the structural layer may be a structure of at least two adjacent or separate layers. In some embodiments, the at least two layers may be simultaneously disposed on the same side of the negative electrode base layer (for example, both disposed below or above the negative electrode base layer), or respectively disposed on both sides of the negative electrode base layer (for example, disposed above and below the negative electrode base layer). Moreover, the at least two layers each independently include nanoparticles and / or micron particles. For example, the particles of the at least two layers are nanoparticles or micron structural layers, or the particles of at least one layer are nanoparticles and the particles of at least one other layer are micron particles. In some embodiments, the structural layer does not chemically react with the electrolyte used in the secondary battery. In a preferred embodiment, the structural layer does not chemically react with the electrolyte, active material, and metal layer and alloy layer used in the negative electrode base layer used in the secondary battery. In a specific embodiment, the nanoparticles or micron particles of the structural layer are selected from non-metallic particles that do not react with the electrolyte. Preferably, the structural layer includes a component selected from at least one of non-metallic elements, oxides, fluorides, carbides, carbon materials, nitrides, and silicides. In a specific embodiment, the structural layer includes particles selected from at least one of sodium fluoride, lithium fluoride, aluminum oxide, and boron nitride, which can maintain the structural stability of the negative electrode reinforcement film layer, thereby continuously maintaining the high specific surface area of ​​the negative electrode, reducing the current density of the negative electrode, and improving the service life of the battery.

[0049] In some embodiments, the negative electrode base layer is an active layer. The material of the negative electrode base layer includes an alkali metal, an alkaline earth metal, or an alloy thereof. The electrolyte in the secondary battery contains corresponding alkali metal or alkaline earth metal cations as active materials. In some preferred embodiments, the negative electrode base layer (i.e., the metal negative electrode) is lithium metal, sodium metal, or an alloy thereof, and the corresponding cations in the electrolyte are lithium ions or sodium ions. Therefore, in the present invention, the alkali metal, alkaline earth metal, or alloy thereof (e.g., sodium metal or sodium alloy) contained in the negative electrode base layer is an active layer.

[0050] In some embodiments of the present invention, the secondary battery uses cations of a single metal as carriers, which is beneficial for reducing the manufacturing, use and management costs of the secondary battery.

[0051] In the present invention, the structural layer is tightly compacted with the negative electrode base layer by cold pressing or hot pressing, forming a convex or concave structure on the surface of the negative electrode base layer, thereby increasing the specific surface area of ​​the negative electrode base layer. In a specific embodiment, the structural layer is arranged between the negative electrode base layer and the negative electrode current collector. For example, the structural layer (for example, layered particles) is arranged on the current collector, and then the negative electrode base layer is pressed onto the structural layer arranged on the current collector. Alternatively, the structural layer is arranged above or below the negative electrode base layer, and the structural layer is directly pressed onto the negative electrode base layer through the current collector.

[0052] In a specific embodiment, the structural layer is disposed on a side of the negative electrode base layer away from the negative electrode current collector. For example, the structural layer is disposed on a side of the negative electrode base layer away from the negative electrode current collector and is directly pressed onto the negative electrode base layer, or is directly pressed onto the negative electrode base layer via a separator.

[0053] In a specific embodiment, the structural layer is discontinuously embedded in the negative electrode base layer to form an integrated structure. For example, when preparing the negative electrode base layer, nanoparticles or microparticles of the structural layer are incorporated to form an integrated structure of the structural layer and the negative electrode base layer, and then the integrated structure is laminated onto the current collector.

[0054] In a specific embodiment, the structural layer is disposed between the negative electrode base layer and the separator. For example, the structural layer (e.g., layered particles) is disposed on the separator, and the negative electrode base layer is then pressed onto the structural layer disposed on the separator. Alternatively, the structural layer is disposed above or below the negative electrode base layer and directly pressed onto the negative electrode base layer through the separator.

[0055] In a specific embodiment, the structural layer is provided between the positive electrode sheet and the separator, and the structural layer abuts the separator to at least partially embed in the negative electrode base layer. For example, the structural layer (e.g., layered particles) is provided on the side surface of the separator facing the positive electrode sheet, and then the negative electrode base layer is pressed onto the separator, so that the separator abuts the positive electrode sheet, whereby the structural layer abuts the separator to at least partially embed in the negative electrode base layer. Alternatively, the structural layer (e.g., layered particles) is provided on the side surface of the separator facing the positive electrode sheet, and then the structural layer is pressed onto the separator, so that the separator abuts the negative electrode base layer, whereby the structural layer abuts the separator to at least partially embed in the negative electrode base layer.

[0056] In a specific embodiment, the structural layer is discontinuously embedded in the separator to form an integrated structure. For example, when preparing the separator layer, nanoparticles or microparticles of the structural layer are incorporated to form an integrated structure of the structural layer and the separator, and this integrated structure is then laminated onto the negative electrode base layer (optionally supported by a current collector).

[0057] In some embodiments, after the negative electrode base layer is pressed onto the structural layer, particles located below the negative electrode base layer can penetrate the negative electrode base layer, forming an island structure protruding from the negative electrode base layer, thereby increasing the specific surface area of ​​the negative electrode base layer. Preferably, the particles do not react with the electrolyte.

[0058] In other embodiments, after the negative electrode base layer is pressed onto the structural layer, the particles below the negative electrode base layer do not penetrate the negative electrode base layer, but can form a convex structure on the upper layer of the negative electrode base layer, thereby increasing the specific surface area of ​​the negative electrode base layer.

[0059] In other embodiments, after the negative electrode base layer is pressed onto the structural layer, the particles located above the negative electrode base layer can be pressed into the negative electrode base layer and can form a recessed structure on the upper layer of the negative electrode base layer, thereby increasing the specific surface area of ​​the negative electrode base layer.

[0060] In some embodiments, the thickness of the negative electrode reinforcement film is 0.01 μm-100 μm, 0.1 μm-50 μm, 1 μm-10 μm, or any numerical range consisting of the end values ​​of the above ranges. In an optional embodiment of the present invention, the thickness of the negative electrode reinforcement film is 0.1 μm-10 μm. When the thickness of the negative electrode reinforcement film is within the above numerical range, the specific surface area of ​​the negative electrode is significantly improved, the energy density of the battery is high, the dynamic characteristics of the battery are ideal, the growth of dendrites is suppressed, the probability of short circuit between the positive and negative electrodes is small, and the manufacturing cost of the battery is low.

[0061] In some embodiments, the surface density of the negative electrode enhancement film is 0.01 mg / cm 2 -30mg / cm 2 , 0.1mg / cm 2 -20mg / cm 2 , 1mg / cm 2 -10mg / cm 2 , 5mg / cm 2 -10mg / cm 2 , or any numerical range consisting of the end values ​​of the above range. In an optional embodiment of the present invention, the surface density of the negative electrode reinforcement film is 0.1 mg / cm 2 -10mg / cm 2When the surface density of the negative electrode enhancement film is within the above numerical range, the battery has a higher energy density, the growth of dendrites is suppressed, the specific surface area of ​​the negative electrode is significantly increased, the manufacturing cost of the battery is low, the probability of short circuit between the positive and negative electrodes is small, and the dynamic characteristics of the battery are ideal.

[0062] In some embodiments, the secondary battery of the present invention includes a positive electrode sheet, a negative electrode sheet having a negative electrode base layer, a separator arranged between the positive electrode sheet and the negative electrode sheet, an electrolyte, and a negative electrode reinforcement film.

[0063] In some embodiments, the at least one metal element in the negative electrode base layer is sodium, and the metal element serving as the active material is sodium. An "active material" is a substance that undergoes a valence change during the charge and discharge process of a battery and participates in the charge transport and current carrying process, such as sodium for a sodium battery and lithium for a lithium battery.

[0064] In some embodiments, the structural layer further comprises a sodium compound, which can serve as a supplementary source of sodium ions in the secondary battery, thereby increasing the service life of the secondary battery.

[0065] In some embodiments, the positive electrode active material is a polyanion salt type, a metal oxide type, or a compound type.

[0066] In some embodiments, the electrolyte contains a metal element as an active material, such as lithium or sodium ions. In some embodiments, the electrolyte contains at least one anion selected from fluorine-containing anions; preferably, at least one selected from bis(fluorosulfonyl)imide, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, difluorooxalatoborate, tetrafluoroborate, hexafluoroarsenate and difluorophosphate. In some embodiments, the solvent of the electrolyte is selected from at least one of ether compounds, acetal compounds and ketal compounds. When the solvent and anion of the electrolyte are selected from the above ranges, the reaction activity of the electrolyte with the negative electrode base layer is low, the consumption rate of the active material is low, the electrolyte can form a negative electrode protective film (SEI) with strong ion conductivity on the surface of the negative electrode base layer, the negative electrode base layer participates in the formation and / or regeneration of the negative electrode protective film, the structural stability of the negative electrode is strong, the kinetic characteristics of the battery are ideal, and the cycle life of the battery is high.

[0067] In some embodiments, the solvent of the electrolyte used has low reactivity with metallic sodium or sodium alloy. In a preferred embodiment, the solvent is an ether solvent. More preferably, the solvent is ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol methyl ether ethyl ether, ethylene glycol diethyl ether, diethylene glycol methyl ether ethyl ether, diethylene glycol diethyl ether, triethylene glycol methyl ether ethyl ether, triethylene glycol diethyl ether, tetraethylene glycol methyl ether ethyl ether, tetraethylene glycol diethyl ether, ethylene glycol methyl ether propyl ether, ethylene glycol ethyl ether propyl ether, ethylene glycol dipropyl ether, diethylene glycol methyl ether propyl ether, diethylene glycol ethyl ether propyl ether, diethylene glycol dipropyl ether, triethylene glycol methyl ether propyl ether, triethylene glycol ethyl ether At least one of propyl ether, triethylene glycol dipropyl ether, tetraethylene glycol methyl ether propyl ether, tetraethylene glycol ethyl ether propyl ether, tetraethylene glycol dipropyl ether, ethylene glycol methyl ether butyl ether, ethylene glycol ethyl ether butyl ether, ethylene glycol propyl ether butyl ether, ethylene glycol dibutyl ether, diethylene glycol methyl ether butyl ether, diethylene glycol ethyl ether butyl ether, diethylene glycol propyl ether butyl ether, diethylene glycol dibutyl ether, triethylene glycol methyl ether butyl ether, triethylene glycol ethyl ether butyl ether, triethylene glycol propyl ether butyl ether, triethylene glycol dibutyl ether, tetraethylene glycol methyl ether butyl ether, tetraethylene glycol ethyl ether butyl ether, tetraethylene glycol propyl ether butyl ether, and tetraethylene glycol dibutyl ether. When the electrolyte solvent is selected from the above range, the reactivity of the electrolyte solvent and the negative electrode base layer is low, which is conducive to maintaining the stability of the negative electrode base layer structure, improving the ion conduction ability and stability of the negative electrode protective film (SEI), optimizing the kinetic characteristics of the battery, reducing the probability of dendrite formation, and improving the service life and rate performance of the battery.

[0068] In some embodiments, the concentration of the electrolyte is 0.5mol / L-7mol / L, 1mol / L-5mol / L, 2mol / L-4mol / L or any numerical range consisting of the end values ​​of the above ranges. In some embodiments of the present invention, the electrolyte further includes additives, and the additives include, but are not limited to: 1,3-dioxolane, 1,4-dioxane, trioxane, lithium nitrate, lithium fluorosulfonate, sulfur dioxide, fluoroethylene carbonate, 12-crown ether-4, 15-crown ether-5 and 18-crown ether-6. In some embodiments, the mass content of the additive in the electrolyte is 0.1% to 20%, 1% to 15% or 5% to 10%. When the concentration of the electrolyte is within the above range, the electrolyte has strong ion conductivity, good film-forming performance, good kinetic characteristics, and can form a negative electrode protective film (SEI) with good ion conductivity on the negative electrode, effectively inhibiting the formation of metal dendrites and reducing the consumption of active substances and electrolytes; the electrolyte has good operability and high wettability for the electrode.

[0069] like Figure 1As shown, the structural layer of the reinforcement film is placed above the current collector, and then the negative electrode base layer (negative electrode sheet) is placed on the reinforcement film by cold pressing or hot pressing. The particles located below the negative electrode base layer can press through the negative electrode base layer, forming an island structure protruding from the negative electrode base layer. Alternatively, the particles located below the negative electrode base layer do not penetrate the negative electrode base layer, but instead form a protrusion structure on the upper layer of the negative electrode base layer.

[0070] like Figure 2 As shown, the structural layer of the reinforcement film is placed below the negative electrode base layer, and then the negative electrode base layer with the structural layer is placed on the current collector by cold pressing or hot pressing. Similarly, the particles located below the negative electrode base layer can press through the negative electrode base layer, forming an island structure protruding from the negative electrode base layer. Alternatively, the particles located below the negative electrode base layer do not penetrate the negative electrode base layer, but instead form a protrusion structure on the upper layer of the negative electrode base layer.

[0071] like Figure 3 As shown, the structural layer of the reinforcement membrane is arranged above the negative electrode base layer, and then the isolation membrane (optionally together with the positive electrode plate) is pressed onto the negative electrode base layer provided with the structural layer by cold pressing or hot pressing, so that the particles above the negative electrode base layer are at least partially pressed / embedded into the negative electrode base layer, and a recessed structure is formed in the upper layer of the negative electrode base layer.

[0072] like Figure 4 As shown, the structural layer of the reinforcement membrane is arranged below the isolation membrane, and then the isolation membrane provided with the structural layer (optionally together with the positive electrode sheet) is pressed onto the negative electrode base layer by cold pressing or hot pressing, so that the particles below the isolation membrane are at least partially pressed / embedded into the negative electrode base layer, and a recessed structure is formed in the upper layer of the negative electrode base layer.

[0073] like Figure 5 As shown, the reinforcement membrane particles are incorporated into the negative electrode base layer raw material and pressed in a molten state to form a negative electrode base layer with an integrated structure of particles. The reinforcement membrane particles form an island structure in the negative electrode base layer. The negative electrode base layer is then laminated onto the current collector.

[0074] like Figure 6 As shown, the particles of the reinforcement film are incorporated into the separator raw material to form a separator with an integrated structure. The particles of the reinforcement film form protrusions on the separator surface. The separator is then laminated to the negative electrode base layer, and a recessed structure is formed on the upper layer of the negative electrode base layer.

[0075] In the present invention, the negative electrode enhancement film increases the specific surface area of ​​the negative electrode base layer. In some embodiments of the present invention, the negative electrode enhancement film is a material that does not chemically react with the electrolyte. Preferably, the negative electrode enhancement film can further be a material that does not chemically react with the electrolyte, active material, metal layer and / or alloy layer. The negative electrode enhancement film includes a material selected from non-metallic elements, oxides (e.g., aluminum oxide, Li7La3Zr2O 12 ), fluoride (e.g., lithium fluoride, sodium fluoride), carbide (e.g., tungsten carbide), carbon material (e.g., carbon nanotubes), nitride (e.g., silicon nitride) and silicide (e.g., titanium silicide), and is at least partially embedded in the metal or alloy active layer. Preferably, the component of the negative electrode reinforcement film is sodium fluoride, lithium fluoride, aluminum oxide, boron nitride, carbon nanotubes, carbon black or a combination thereof. When the structural layer is selected from the above range, the consumption rate of the active material in the battery is low, the structure of the negative electrode reinforcement film is stable, which is conducive to continuously maintaining the high specific surface area of ​​the negative electrode base layer, reducing the current density of the negative electrode, reducing the probability of short circuit between the positive and negative electrodes of the battery, and improving the service life of the battery.

[0076] secondary batteries

[0077] The secondary battery of this utility model comprises a positive electrode (pole), a negative electrode (pole), a separator, and an electrolyte / liquid. During the battery's charge and discharge processes, active metal cations are intercalated and released back and forth between the positive and negative electrodes. The electrolyte acts as an ion conductor between the positive and negative electrodes.

[0078] [Positive electrode]

[0079] In the secondary battery of the present invention, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer (or positive electrode active material layer) provided on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector. In the secondary battery of the present invention, the positive electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can be an aluminum foil, and the composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. 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 substrate (such as a substrate of polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers, etc.).

[0080] In the secondary battery of the present invention, the positive electrode active material (substance) can be a positive electrode active material for a secondary battery known in the art. For example, the positive electrode active material may include one or more of the following: olivine-structured phosphates, transition metal oxides, and their respective modified compounds. However, the present invention is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for secondary batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more, including but not limited to layered oxides, polyanionic materials, or Prussian blue materials containing the same metal element ions as at least one metal element in the negative electrode base layer.

[0081] In some embodiments, the positive electrode film layer may also optionally include a binder. Non-limiting examples of binders that can be used for the positive electrode film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin. In an embodiment of the present utility model, each of the first positive active material layer and / or the second positive active material layer independently contains a binder selected from polyvinylidene fluoride, polyacrylic acid, polytetrafluoroethylene, polyimide and a combination thereof.

[0082] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. Examples of conductive agents for the positive electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In an embodiment of the present invention, the first positive electrode active material layer and / or the second positive electrode active material layer each independently contain a conductive agent selected from graphite, carbon black, acetylene black, graphene, carbon nanotubes, and combinations thereof.

[0083] In one embodiment of the present invention, the positive electrode can be prepared in the following manner: the components for preparing the positive electrode, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0084] [Negative electrode]

[0085] In the secondary battery of the present invention, the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode base layer. For example, in certain embodiments, the negative electrode plate of the present invention may further include a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode base layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate of the present invention may further include a covering protective layer covering the surface of the second negative electrode film layer.

[0086] In the secondary battery of the present invention, the negative electrode current collector may be a metal foil or a composite current collector. For example, the metal foil may be copper foil, silver foil, iron foil, or alloys thereof. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. 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 base layer (e.g., a base layer made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene PE, and copolymers thereof).

[0087] [Electrolytes]

[0088] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The electrolyte can be selected from at least one of a solid electrolyte, a semi-solid electrolyte, and a liquid electrolyte. In some embodiments, the electrolyte is a liquid electrolyte. In one embodiment of the present invention, the electrolyte may optionally contain additives. For example, the additives may include one or more of the following: negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature performance, etc.

[0089] [Isolation film]

[0090] In one embodiment of the present invention, the secondary battery further comprises a separator, which separates the anode side of the secondary battery from the cathode side, and provides selective permeation or blocking for substances of different types, sizes and charges in the system. For example, the separator can insulate electrons, physically isolate the positive and negative electrodes of the secondary battery, prevent internal short circuits and form an electric field in a certain direction, and at the same time allow ions in the battery to pass through the separator and move between the positive and negative electrodes. In one embodiment of the present invention, the material used to prepare the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different. In an embodiment of the present invention, the separator is selected from polyolefin separators, polyester separators, polyimide separators, polyamide separators and cellulose separators.

[0091] In one embodiment of the present invention, the positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly / bare cell by a winding process or a lamination process.

[0092] In one embodiment of the present invention, the secondary battery may include an outer packaging that can be used to encapsulate the above-mentioned electrode assembly and electrolyte. In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. In other embodiments, the outer packaging of the secondary battery can be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0093] The shape of the secondary battery of the present invention can be cylindrical, square or any other shape. The outer packaging may include a shell and a cover plate. The shell may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell has an opening connected to the receiving cavity, and the cover plate can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly through a winding process or a lamination process. The electrode assembly is encapsulated in the receiving cavity, and the electrolyte is impregnated in the electrode assembly. The number of electrode assemblies contained in the secondary battery can be one or more.

[0094] In one embodiment of the present invention, several secondary batteries may be assembled together to form a battery module. The battery module includes two or more secondary batteries, and the specific number depends on the application of the battery module and the parameters of a single battery module.

[0095] In a battery module, multiple secondary batteries may be arranged sequentially along the length of the battery module. Of course, they may also be arranged in any other manner. Furthermore, the multiple secondary batteries may be secured using fasteners. Optionally, the battery module may further include a housing having a storage space, wherein the multiple secondary batteries are housed in the storage space.

[0096] In one embodiment of the present invention, two or more of the aforementioned battery modules can be assembled into a battery pack. The number of battery modules contained in the battery pack depends on the application of the battery pack and the parameters of the individual battery modules. The battery pack can include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper box body and a lower box body. The upper box body can cover the lower box body and fit well therewith to form an enclosed space for accommodating the battery modules. The two or more battery modules can be arranged in the battery box in any desired manner.

[0097] In one embodiment of the present invention, a battery pack may include a battery case and a plurality of battery modules disposed within the battery case. The battery case includes an upper case and a lower case, with the upper case covering the lower case and forming an enclosed space for accommodating the battery modules. The plurality of battery modules may be arranged in any manner within the battery case.

[0098] Electrical devices

[0099] In one embodiment of the present invention, an electrical device includes at least one of the secondary battery, battery module, or battery pack of the present invention. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device includes, but is not limited to, mobile digital 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, satellites, energy storage systems, etc.

[0100] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0101] In the following, the influence of the secondary battery manufactured according to the embodiment of the present invention on the performance of the electrochemical device is characterized based on specific examples. However, it should be pointed out that the scope of protection of the present invention is defined by the claims and is not limited to the above specific embodiments.

[0102] Example

[0103] Unless otherwise specified, all raw materials used in this invention were analytically pure and all water used was deionized water.

[0104] 1. Preparation of positive electrode sheet

[0105] 10 wt% of polyvinylidene fluoride was dissolved in N-methylpyrrolidone as a binder, and 80 wt% of a polyanion salt-type positive electrode active material containing active material elements (see Table 1-4 for details) and 10 wt% of conductive carbon black were added to prepare a uniformly dispersed positive electrode slurry. The positive electrode slurry was evenly coated on the surface of the aluminum foil current collector and transferred to a vacuum oven for thorough drying. The obtained positive electrode sheet was rolled and punched to obtain the target positive electrode disc.

[0106] 2. Preparation of negative electrode sheet

[0107] In an Ar atmosphere, as shown in Table 1-6 below, the metal constituting the negative electrode base material, or the metal constituting the negative electrode base material and other alloy component powders are placed in a stainless steel crucible and heated until completely melted and fully stirred, and then cooled to obtain the negative electrode base layer material.

[0108] The negative electrode base layer material is compounded on the surface of the copper foil by cold pressing or hot pressing to obtain a negative electrode base layer with a layered structure. Alternatively, the negative electrode base layer material is compounded on the surface of the copper foil by atomization spraying or sputtering to obtain a negative electrode base layer with a granular structure. Alternatively, the negative electrode base layer material is compounded on the surface of the copper foil by extrusion to obtain a negative electrode base layer with a strip structure. Alternatively, the negative electrode base layer material is compounded on the surface of the copper foil by atomization spraying or sputtering to obtain a negative electrode base layer with a three-dimensional structure.

[0109] The negative electrode enhancement film material is compounded on the surface of the negative electrode base layer by cold pressing or hot pressing to obtain the negative electrode plate.

[0110] 3. Preparation of Isolation Membrane

[0111] A polypropylene porous polymer film is used as the separator.

[0112] 4. Preparation of liquid electrolyte (electrolyte)

[0113] Under an Ar atmosphere, a fully dried fluorine-containing salt (hexafluorophosphate, hexafluoroarsenate or tetrafluoroborate) is dissolved in an organic solvent of ethylene glycol dipropyl ether and stirred thoroughly to prepare an electrolyte (the corresponding fluorine-containing sodium salt is used for sodium batteries, and the corresponding fluorine-containing lithium salt is used for lithium batteries).

[0114] 5. Preparation of Button Cells

[0115] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to play an isolating role, and the electrolyte is added to assemble into a button battery.

[0116] According to the above preparation method, the negative electrode sheets used in Examples 1-27 and Comparative Examples 1-8 were prepared. The specific parameters of the negative electrode sheet formulations are shown in Tables 1-4. To maintain consistency in comparison, the negative electrode substrate layer in each Example and Comparative Example has a layered structure with an area density of 5 mg / cm 2 , the fluoride-containing salt in the electrolyte is hexafluorophosphate, and the positive electrode polyanion salt is iron phosphate.

[0117] In Table 1, the structural layer in Examples 1-6 and Comparative Example 5 is a particle layer. Except for the material, all other conditions are the same. The nano-enhanced membranes in Examples 1-7 and Comparative Example 5 are all partially embedded in the negative electrode base layer to the same extent (approximately 1 / 4 of the thickness of the negative electrode base layer). In Comparative Examples 3 and 4, a planar sodium fluoride negative electrode reinforcement membrane and a lithium fluoride negative electrode reinforcement membrane are deposited on the negative electrode base layer by spraying, with the same surface density as in Example 1 and Example 6, respectively.

[0118] According to the comparison of Examples 1-5, 7 and Comparative Example 1 in Table 1, as well as Example 6 and Comparative Example 2, the negative electrode provided by the present invention has higher cycle performance than the general sodium metal secondary battery and lithium metal secondary battery negative electrode, and the negative electrode enhancement film partially embedded in the base layer can increase the specific surface area of ​​the negative electrode, reduce the current density of the negative electrode and the thickness of the SEI, and improve the cycle performance of the battery. However, by analyzing Comparative Examples 3 and 4, it can be seen that the improvement in cycle performance is affected by the relationship between the negative electrode enhancement film and the negative electrode base structure. When only a sodium fluoride film layer or a lithium fluoride film layer is deposited on the negative electrode base layer, the sodium fluoride film or the lithium fluoride film cannot be embedded in the base layer and cannot effectively increase the specific surface area of ​​the base layer. Therefore, it only plays a simple SEI protection effect and increases the impedance of the battery, affecting the improvement in battery cycle performance, such as the cycle performance is less than 500 times. At the same time, analysis of Comparative Example 5 shows that when the components of the negative electrode reinforcement film are substances that do not react with the active material and / or the electrolyte and / or the negative electrode base layer, the consumption rate of the active material in the battery is low, and the negative electrode reinforcement film has a stable structure, thereby increasing the specific surface area of ​​the negative electrode base layer, stabilizing the surface state of the negative electrode base layer, reducing the actual current density of the negative electrode, and improving the battery's cycle performance. When the components of the negative electrode reinforcement film can react with the active material and / or the electrolyte and / or the negative electrode base layer, the consumption rate of the active material in the battery is high, the structure of the negative electrode reinforcement film is unstable, and thus the structure of the negative electrode base layer is unstable, which deteriorates the battery's cycle performance.

[0119]

[0120] Table 1

[0121] The test results of Examples 8 to 13 and Comparative Example 6 in Table 2 show that when the thickness of the negative electrode reinforcement film is in the range of 0.01 μm to 100 μm, the battery has a higher energy density. The negative electrode reinforcement film can effectively increase the specific surface area of ​​the negative electrode, reduce the current density of the negative electrode, prevent excessive SEI formation, and further optimize the battery's cycling performance. The test results of Comparative Example 6 show that when the thickness of the negative electrode reinforcement film is too high, the battery's energy density is low, the battery impedance is high, the kinetic characteristics of ion transport on the negative electrode surface are poor, metal dendrites are easily formed, and the battery's cycling performance is reduced.

[0122]

[0123]

[0124] Table 2

[0125] According to the test results of Examples 14 to 20 and Comparative Example 7 in Table 3, when the surface density of the negative electrode reinforcement film (which can be measured by weighing, assuming uniform thickness, weight divided by area) is 0.01 to 30 mg / cm 2 When the battery has a higher energy density, the negative electrode enhancement film can effectively increase the specific surface area of ​​the negative electrode, reduce the current density of the negative electrode, prevent the excessive formation of SEI, and further optimize the cycle performance of the battery. 2 The test results of Comparative Example 7 show that when the surface density of the negative electrode enhancement film is too high, the battery energy density is low, the battery impedance is large, the kinetic characteristics of ion transport on the negative electrode surface are poor, metal dendrites are easily formed, and the battery cycle performance is reduced.

[0126]

[0127] Table 3

[0128] The test results of Examples 21 to 27 and Comparative Example 8 in Table 4 show that when the particle size of the negative electrode reinforcement film is ≤50 μm, the negative electrode reinforcement film can effectively increase the specific surface area of ​​the negative electrode, reduce the current density of the negative electrode during battery charge and discharge, reduce the thickness of the SEI, and inhibit excessive SEI passivation of the negative electrode, thereby improving the battery's cycle life. The test results of Comparative Example 8 show that when the particle size of the negative electrode reinforcement film is too large, the negative electrode reinforcement film is unable to effectively increase the specific surface area of ​​the negative electrode, and the electrochemical performance of the battery is difficult to improve. Moreover, larger negative electrode reinforcement film particles can easily cause separator puncture and battery short circuit, reducing the battery's cycle performance and increasing the risk of battery use.

[0129]

[0130]

[0131] Table 4

[0132] Test Method

[0133] 1. Specific surface area S 负

[0134] According to the national standard "GB / T 19587-2004 Method for Determining the Specific Surface Area of ​​Solids by the BET Principle of Gas Adsorption", the test is performed using an adsorption characterization analyzer. The powder sample to be tested is placed in a U-shaped sample tube, and a mixed gas containing a certain proportion of adsorbate flows through the sample. The adsorption amount of the adsorbate molecules (N2) by the sample to be tested is determined based on the change in gas concentration before and after adsorption, thereby obtaining the specific surface area S. 负 .

[0135] 2. Median particle size D 50负

[0136] Median particle size D 50负 The median particle size of the particles, in μm. 50负 The particle size corresponding to the cumulative volume percentage of particles reaches 50%. According to the national standard "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method", the sample is dispersed under pressure and the particle size of the material is characterized by a laser particle size analyzer. The test results are expressed as median particle size D 50负 Indicates the average particle size.

[0137] 3. Surface density of negative electrode base layer

[0138] The square negative electrode substrate layer with a size of 10 cm*10 cm was weighed to obtain its mass, which was then divided by its area to obtain the surface density 1.

[0139] 4. Thickness of the negative electrode base layer

[0140] A 10cm*10cm square negative electrode sheet was placed, with its corners aligned, between two 10cm*10cm stainless steel sheets of uniform thickness and a defined thickness H1. The total thickness H2 of the two stainless steel sheets plus the negative electrode sheet was measured, and the thickness H3 of the negative electrode sheet was calculated using the formula H3 = H2 - 2H1. When the negative electrode sheet is double-sided coated, the approximate thickness H5 of the negative electrode base layer was calculated using the formula H5 = (H3 - H4) / 2, where H4 is the thickness of the current collector. When the negative electrode sheet is single-sided coated, the approximate thickness H5 of the negative electrode base layer was calculated using the formula H5 = H3 - H4, where H4 is the thickness of the current collector.

[0141] 5. Cyclic performance test

[0142] At 25°C, the secondary batteries prepared in the Examples and Comparative Examples were subjected to full charge and discharge cycle testing at a 0.5C rate. The number of cycles at which the battery capacity reached 80% or less of its initial capacity was recorded (recorded as the nth cycle). A higher n indicates better cycling performance. A cycle greater than 530 cycles indicates excellent cycling performance, a cycle between 500 and 530 cycles indicates fair cycling performance, and a cycle less than 500 cycles indicates poor cycling performance.

Claims

1. A negative electrode reinforcement membrane for a secondary battery, comprising at least one structural layer in contact with a negative electrode base layer, wherein the structural layer is at least partially embedded in the negative electrode base layer, and the negative electrode base layer is an active layer.

2. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that The structural layer is a particle layer, which includes nanoparticles and / or microparticles, and at least a portion of the surface of at least a portion of the nanoparticles and / or microparticles is in contact with the negative electrode base layer.

3. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that The structural layer is a grid layer, which includes nanogrids and / or microgrids, and at least a portion of the surface of at least a portion of the nanogrids and / or microgrids is in contact with the negative electrode base layer.

4. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that The negative electrode base layer is made of a material selected from alkali metals or their alloys, and alkaline earth metals or their alloys.

5. The negative electrode reinforcement film for secondary batteries according to claim 4, characterized in that: The alkali metal or its alloy is sodium metal and / or its alloy, or lithium metal and / or its alloy.

6. The negative electrode reinforcement film for secondary batteries according to claim 3, characterized in that The structural layer does not chemically react with the electrolyte.

7. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that The structural layer does not chemically react with the electrolyte and does not chemically react with the active layer material.

8. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that The structural layer is configured in at least one of the following ways: (1) The structural layer is arranged between the negative electrode base layer and the negative electrode current collector; (2) The structural layer is provided between the negative electrode base layer and the separator; (3) The structural layer is arranged on the side of the negative electrode base layer away from the negative electrode current collector; (4) The structural layer is embedded in the negative electrode base layer in a discontinuous manner to form an integrated structure; (5) The structural layer is disposed between the positive electrode sheet and the separator, and the structural layer abuts against the separator to be at least partially embedded in the negative electrode base layer; (6) The structural layer is embedded in the isolation membrane in a discontinuous manner to form an integrated structure.

9. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that At least a portion of the structural layer does not penetrate the negative electrode base layer, and a convex-concave structure is formed on the surface of the negative electrode base layer.

10. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that The negative electrode reinforcement film includes two structural layers, and the two structural layers are both arranged on the same side of the negative electrode base layer or respectively arranged on both sides of the negative electrode base layer.

11. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that: The thickness of the negative electrode enhancement film is 0.01 μm-100 μm.

12. The negative electrode reinforcement film for secondary batteries according to claim 1, characterized in that: The surface density of the negative electrode enhancement film is 0.01 mg / cm 2 -30mg / cm 2 .

13. The negative electrode reinforcement film for secondary batteries according to claim 2, characterized in that: The granular layer includes a median particle size D 50 Particles between 5nm-50μm.

14. The negative electrode reinforcement film for secondary batteries according to claim 2, characterized in that: Median particle size D 50 20nm-50μm. 15 . A lithium or sodium secondary battery comprising a positive electrode sheet, an electrolyte, a negative electrode sheet having a negative electrode base layer, and the negative electrode reinforcement film according to claim 1 .

16. The lithium or sodium secondary battery according to claim 15, characterized in that The electrolyte contains sodium ions or lithium ions as an active material.

17. An electrical device comprising the lithium or sodium secondary battery according to any one of claims 15 to 16.

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