CN116544615A

CN116544615A - Separator, lithium secondary battery, and electricity-using device

Info

Publication number: CN116544615A
Application number: CN202310805724.2A
Authority: CN
Inventors: 李梅; 马云建; 姚萌; 李彦辉; 张加锡; 唐代春; 杨瑞
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-07-03
Filing date: 2023-07-03
Publication date: 2023-08-04

Abstract

Provided are a separator, a lithium secondary battery, and an electric device. The separator includes a base film and an overcharge preventing coating layer located on at least one side of the base film, the overcharge preventing coating layer including an overcharge preventing additive including a lithium-containing compound. The overcharge-preventing additive can be timely decomposed under overcharge voltage to respond to overcharge phenomenon, so that the safety and the electrical performance of the battery can be improved.

Description

Separator, lithium secondary battery, and electricity-using device

Technical Field

The application relates to the technical field of secondary batteries, in particular to a separation film, a lithium secondary battery and an electric device.

Background

In recent years, secondary batteries are widely used in energy storage power supply systems such as hydraulic power, thermal power, wind power and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace, and the like.

At present, secondary batteries have various problems in application, for example, the secondary batteries have an overcharging phenomenon, when the secondary batteries are overcharged beyond the normal working voltage, a great amount of heat is generated, even thermal runaway is caused, the safety of the secondary batteries is seriously affected, and the application requirements of a new generation of electrochemical systems cannot be met.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide a separator including an overcharge preventing coating layer containing an overcharge preventing additive which can be decomposed in time under overcharge conditions and respond to overcharge phenomena, and further to improve the safety and electrical properties of a battery.

A first aspect of the present application provides a separator comprising a base film and an anti-overcharge coating on at least one side of the base film, the anti-overcharge coating comprising an anti-overcharge additive comprising a lithium-containing compound.

When the battery works and charges in an overcharging voltage range higher than the normal working voltage range of the secondary battery, the overcharge-preventing additive can decompose to generate gas, the resistance of the secondary battery is increased, the voltage of the secondary battery is correspondingly and rapidly increased, the risk of thermal runaway caused by oxidative decomposition of electrolyte is further reduced, the risk of separating out active ions from the positive electrode active material is also reduced, the structure of the positive electrode active material is protected from being damaged, and the safety and the electrical property of the secondary battery are improved.

In any embodiment, the lithium-containing compound comprises Li ₂ C ₂ O ₄ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₃ O ₅ 、Li ₂ C ₄ O ₆ 、LiN ₃ Optionally including Li ₂ C ₂ O ₄ 、LiN ₃ One or more of the following.

The substances can be used as overcharge-preventing additives to decompose and generate gas in the overcharge voltage range higher than the working voltage range of the secondary battery, such as Li ₂ C ₂ O ₄ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₃ O ₅ Or Li (lithium) ₂ C ₄ O ₆ Can decompose and produce carbon monoxide or carbon dioxide, has increased resistance and voltage of its secondary battery, and then has reduced the risk that brings the thermal runaway because electrolyte oxidizes and decomposes, also reduces the risk that the positive electrode active material separates out the active ion, has protected the structure of positive electrode active material not destroyed to make the secondary battery still can normally work in the overcharging pressure range, and have excellent cycle performance, widened the working voltage window of battery, comprehensively promoted secondary battery security and electrical property.

In any embodiment, the anti-overcharge coating further comprises a binder comprising one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymers, polyacrylamides, polyurethanes, poly (acrylonitrile-acrylate), polyacrylates, poly (styrene-acrylate), optionally comprising polyvinylidene fluoride.

The adhesive in the overcharge-preventing coating can realize the lamination between the isolating film and the positive pole piece and/or the negative pole piece, and reduce the interface resistance between the isolating film and the positive pole piece and/or the negative pole piece.

In any embodiment, the anti-overcharge additive is 0.5% -15%, optionally 1% -10% by mass based on the total mass of the anti-overcharge coating.

The mass content of the overcharge-preventing additive in the overcharge-preventing coating is controlled within a proper range, so that the overcharge-preventing additive in the overcharge-preventing coating can be timely decomposed to release gas when the battery is overcharged, the resistance of the battery is increased, the voltage of the battery is further increased, and the structure of the positive electrode active material is protected from being damaged; but also can reduce the influence of excessive introduction of the overcharge-preventing additive on the transmission of active ions and reduce the influence on the performance of the battery.

In any embodiment, the ratio of the thickness of the overcharge-preventing coating layer to the thickness of the isolating film is (0.05 to 0.6): 1, optionally (0.1 to 0.5): 1.

The ratio of the thickness of the anti-overcharge coating to the thickness of the isolating film is controlled within a proper range, so that the anti-overcharge coating can provide enough bonding effect and anti-overcharge protection effect, and the influence of the excessive thickness of the anti-overcharge coating on active ion transmission can be reduced.

In any embodiment, the thickness of the overcharge-preventing coating is 0.35-18 mu m, and optionally 1-10 mu m.

In any embodiment, the thickness of the isolation film is 7-30 [ mu ] m, and optionally 9-20 [ mu ] m.

The thickness of the anti-overcharge coating and the thickness of the isolating film are controlled within a proper range, so that the effect of isolating the positive pole piece and the negative pole piece by the isolating film, the bonding effect of the anti-overcharge coating and the anti-overcharge protection effect can be realized, and the influence of the excessive thickness of the isolating film on the transmission of active ions can be reduced.

In any embodiment, the barrier film further comprises a ceramic coating between the base film and the anti-overcharge coating.

The introduction of the ceramic coating is beneficial to improving the mechanical strength of the isolating membrane.

In any embodiment, the ceramic coating comprises alumina (Al ₂ O ₃ ) One or more of water and alumina (boehmite-gamma-AlOOH).

The ceramic coating layers comprising the above substances have excellent mechanical strength, thereby improving the mechanical properties of the barrier film.

In any embodiment, the base film comprises one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, fiberglass, nonwoven, optionally polyethylene.

The anti-overcharging coating in any embodiment of the application can be widely applied to various base films and can be matched with the base films to prepare the isolating film.

In any embodiment, the barrier film comprises a base film and a coating layer positioned on two sides of the base film, wherein the coating layer on one side of the base film comprises the anti-overcharge coating layer, and the coating layer on the other side of the base film does not comprise the anti-overcharge coating layer.

The overcharge-preventing coating including the overcharge-preventing additive may be located at one side of the separator, i.e., an effect of improving the safety of the battery without impairing the electrochemical performance may be achieved.

A second aspect of the present application provides a lithium secondary battery comprising a positive electrode tab, a negative electrode tab, and a separator as described in the first aspect of the present application.

In any embodiment, the overcharge-preventing coating is located between the positive electrode sheet and the base film.

When the battery is in an overcharged state, the overcharge-preventing coating on the side of the positive electrode plate can be rapidly decomposed to generate gas, so that the interface resistance between the positive electrode plate and the isolating film is increased, the voltage of the battery is further increased, the risk of structural collapse of the positive electrode active material is reduced, and the structure of the positive electrode active material is protected.

In any embodiment, the positive electrode sheet comprises a positive electrode active material comprising Li _d [Ni _x Co _y X1 _z M1 _1-x-y-z ]O ₂ 、LiMn ₂ O ₄ 、Li ₂ MnO ₃ ·(1-a)LiAO ₂ 、LiM2X2O ₄ One or more of the following;

wherein d is more than or equal to 0.1 and less than or equal to 1, and X1 comprises Mn and/or Al; m1 comprises one or more of Co, ni, mn, mg, cu, zn, al, sn, B, ga, cr, sr, V, ti, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and x+y+z is more than or equal to 1; a comprises one or more of Ni, co and Mn, and a is more than 0 and less than 1; m2 includes one or more of Fe, mn, ni, co; X2O ₄ ^h- X2 of (a) comprises one or more of S, P, as, V, mo, W, h=2 or 3.

The isolating film in any embodiment of the application can be widely applied to various positive electrode active materials, and can realize the protection of the shape of the positive electrode plate when being matched with the positive electrode active materials.

A third aspect of the present application provides an electric device comprising the lithium secondary battery of the second aspect of the present application.

Drawings

Fig. 1 is a schematic view of a battery cell assembly of a lithium secondary battery according to an embodiment of the present application;

fig. 2 is a schematic view of a lithium secondary battery according to an embodiment of the present application;

fig. 3 is an exploded view of the lithium secondary battery of an embodiment of the present application shown in fig. 2;

fig. 4 is a schematic view of a battery module according to an embodiment of the present application;

FIG. 5 is a schematic view of a battery pack according to an embodiment of the present application;

FIG. 6 is an exploded view of the battery pack of one embodiment of the present application shown in FIG. 5;

fig. 7 is a schematic view of an electric device in which the lithium secondary battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; a 5 lithium secondary battery; 51 a housing; 52 electrode assembly; 53 cover plates; 521 positive pole piece; 522 negative pole piece; 5231 an overcharge protection coating; 5232 ceramic coating; 5233 base film; 5234 tie coat.

Detailed Description

Hereinafter, embodiments of the separator, the lithium secondary battery, and the electric device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., 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 particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, 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 are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.

All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

Currently, the "overcharge phenomenon" of a secondary battery seriously affects the safety and electrical properties thereof. For example, in a lithium secondary battery, when the lithium secondary battery is overcharged beyond a normal operating voltage, the positive electrode active material releases excessive lithium ions to cause collapse of the structure of the positive electrode active material, the electrolyte also generates oxidative decomposition, releases a large amount of heat, and seriously causes thermal melting of a diaphragm, so that the risk of internal short circuit between a positive electrode plate and a negative electrode plate is increased, thermal runaway is caused, even explosion occurs, and the electrical performance and safety of the battery are seriously affected. Therefore, there is a need to design a novel overcharge-preventing secondary battery system to meet the demands of the new generation secondary batteries.

[ isolation Membrane ]

Based on this, the application proposes a barrier film comprising a base film and an anti-overcharge coating layer located on at least one side of the base film, the anti-overcharge coating layer comprising an anti-overcharge additive comprising a lithium-containing compound.

As used herein, the term "overcharge-preventing additive" refers to an additive that can decompose to generate a gas when the secondary battery is overcharged above a normal operating voltage, and may be a lithium-containing compound containing carbon and/or nitrogen, including but not limited to Li ₂ C ₂ O ₄ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₃ O ₅ 、Li ₂ C ₄ O ₆ Or LiN ₃ 。

Herein, the term "normal operating voltage" refers to the withstand voltage of normal operation of a conventional secondary battery (excluding the overcharge-preventing additive), one of the main influencing factors of the normal operating voltage of which is a positive electrode active material. For example, for a positive electrode sheet containing a ternary positive electrode active material, the normal operating voltage of the secondary battery is 3.0v to 4.4v; for a positive electrode sheet containing a lithium iron phosphate positive electrode active material, the normal working voltage of a secondary battery is 2.0V-3.6V.

In this context, the term "anti-overcharge coating" refers to a coating comprising an anti-overcharge additive. The anti-overcharge coating can also comprise a binder with a bonding effect so that the anti-overcharge coating plays a role in bonding; the anti-overcharge coating may also include a reinforcing component having enhanced mechanical properties such that the anti-overcharge coating serves to increase mechanical strength.

In some embodiments, the barrier film includes a base film and an anti-overcharge coating on one side of the base film.

In some embodiments, the barrier film includes a base film and an anti-overcharge coating on opposite sides of the base film.

It can be understood that when the battery is operated and charged in an overcharge voltage range higher than the normal operation voltage range of the secondary battery, the overcharge preventing additive is decomposed to generate gas, the resistance of the secondary battery is increased, the voltage of the secondary battery is correspondingly and rapidly increased, the risk of thermal runaway caused by oxidative decomposition of the electrolyte is further reduced, the risk of precipitation of active substances of the positive electrode active material is also reduced, the structure of the positive electrode active material is protected from being damaged, so that the secondary battery can still normally operate in the overcharge voltage range, the excellent cycle performance is provided, the operation voltage window of the battery is widened, and the safety and the electrical performance of the secondary battery are comprehensively improved.

In addition, the conventional introduction of the overcharge-preventing additive into the positive electrode active material layer of the positive electrode sheet not only results in a decrease in the amount of the positive electrode active material used, but also reduces the battery capacity and energy density of the secondary battery, and the introduction of the overcharge-preventing additive slows down the diffusion of active ions (such as lithium ions) inside and outside the positive electrode active material layer, increases the resistance of the secondary battery, and deteriorates the cycle performance of the battery. In some embodiments of the application, the overcharge-preventing additive is introduced on the overcharge-preventing coating layer in the isolating film, so that the influence on the dosage of the positive electrode active material can be reduced, the secondary battery has excellent battery capacity and energy density, and the diffusion of active ions inside and outside the positive electrode active material layer caused by the introduction of the overcharge-preventing additive can be reduced, so that the secondary battery has lower impedance and excellent cycle performance. In addition, the spray process of the overcharge-preventing coating layer is simpler than the coating process of the positive electrode active material layer.

In this context, the term "overcharge voltage" means that the voltage at the time of charging exceeds the allowable charge voltage of the battery, i.e., the voltage at the time of charging exceeds the normal operating voltage of the battery. The charging may be in a full charge state or in an insufficient charge state.

In some embodiments, the lithium-containing compound includes Li ₂ C ₂ O ₄ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₃ O ₅ 、Li ₂ C ₄ O ₆ 、LiN ₃ Optionally including Li ₂ C ₂ O ₄ 、LiN ₃ One or more of the following.

In some embodiments, the overcharge-preventing additive comprises Li ₂ C ₂ O ₄ . In some embodiments, the overcharge-preventing additive comprises Li ₂ C ₄ O ₄ . In some embodiments, the overcharge-preventing additive comprises Li ₂ C ₃ O ₅ . In some embodiments, the anti-overcharge additive comprises LiN ₃ . In some embodiments, the overcharge-preventing additive comprises Li ₂ C ₂ O ₄ And Li (lithium) ₂ C ₃ O ₅ . In some embodiments, the overcharge-preventing additive comprises Li ₂ C ₄ O ₆ And LiN ₃ 。

The substances can be used as overcharge-preventing additives to decompose and generate gas in the overcharge voltage range higher than the working voltage range of the secondary battery, such as Li ₂ C ₂ O ₄ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₃ O ₅ Or Li (lithium) ₂ C ₄ O ₆ Can decompose to produce carbon monoxide or carbon dioxide, thereby increasing the resistance and voltage of the secondary battery, reducing the risk of thermal runaway caused by the oxidative decomposition of electrolyte, reducing the risk of separating out active substances from the positive electrode active material, protecting the structure of the positive electrode active material from being damaged, and improving the safety and electrical property of the secondary battery.

In some embodiments, the anti-overcharge coating further comprises a binder comprising one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymers, polyacrylamides, polyurethanes, poly (acrylonitrile-acrylate), polyacrylates, poly (styrene-acrylate), optionally comprising polyvinylidene fluoride.

In some embodiments, the anti-overcharge coating includes an anti-overcharge additive including Li and a binder ₂ C ₂ O ₄ The binder comprises polyvinylidene fluoride. In some embodiments, the anti-overcharge coating includes an anti-overcharge additive including Li and a binder ₂ C ₄ O ₄ The binder comprises polyvinylidene fluoride. In some embodiments, the anti-overcharge coating includes an anti-overcharge additive and a binder, the anti-overcharge additive including LiN ₃ The binder comprises polyvinylidene fluoride. In some embodiments, the anti-overcharge coating includes an anti-overcharge additive including Li and a binder ₂ C ₄ O ₆ And LiN ₃ The binder comprises polyvinylidene fluoride. In some embodiments, the anti-overcharge coating includes an anti-overcharge additive including Li and a binder ₂ C ₄ O ₆ And LiN ₃ The binder comprises polyacrylamide.

In some embodiments, the anti-overcharge coating further includes additives that can improve certain properties of the separator, such as additives that improve the active ion transport properties of the separator, additives that improve the interfacial resistance between the base film and the anti-overcharge coating, additives that improve the interfacial resistance of the separator and the positive and/or negative electrode sheets.

In some embodiments, the anti-overcharge additive is present in an amount of 0.5% to 15%, alternatively 1% to 10%, by mass based on the total mass of the anti-overcharge coating. In some embodiments, the mass content of the anti-overcharge additive can be selected to be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a value in the range consisting of any two points above, based on the total mass of the anti-overcharge coating.

The mass content of the overcharge-preventing additive in the overcharge-preventing coating is controlled within a proper range, so that the overcharge-preventing additive in the overcharge-preventing coating can be timely decomposed to release gas when the battery is overcharged, the resistance of the battery is increased, the voltage of the battery is further increased, and the structure of the positive electrode active material is protected from being damaged during overcharging; but also can reduce the influence of excessive introduction of the overcharge-preventing additive on the transmission of active ions and reduce the influence on the performance of the battery.

In some embodiments, the ratio of the thickness of the anti-overcharge coating to the thickness of the release film is (0.05 to 0.6): 1, optionally (0.1 to 0.5): 1. In some embodiments, the ratio of the thickness of the anti-overcharge coating to the thickness of the release film can be selected to be 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, or a ratio in the range consisting of any two ratios described above.

In some embodiments, the thickness of the anti-overcharge coating is 0.35-18 [ mu ] m, optionally 1-10 [ mu ] m. In some embodiments, the thickness of the anti-overcharge coating may be selected to be 0.35 [ mu ] m, 0.5 [ mu ] m, 1 [ mu ] m, 2 [ mu ] m, 4 [ mu ] m, 5 [ mu ] m, 6 [ mu ] m, 8 [ mu ] m, 10 [ mu ] m, 12 [ mu ] m, 14 [ mu ] m, 15 [ mu ] m, 16 [ mu ] m, 18 [ mu ] m, or a value in a range formed by any two points described above.

In some embodiments, the thickness of the isolation film is 7-30 [ mu ] m, and optionally 9-20 [ mu ] m. In some embodiments, the thickness of the isolation membrane may be selected to be 7 [ mu ] m, 9 [ mu ] m, 10 [ mu ] m, 12 [ mu ] m, 15 [ mu ] m, 18 [ mu ] m, 20 [ mu ] m, 22 [ mu ] m, 25 [ mu ] m, 26 [ mu ] m, 28 [ mu ] m, 30 [ mu ] m, or a value in a range formed by any two points.

In some embodiments, the barrier film further comprises a ceramic coating between the base film and the anti-overcharge coating.

In some embodiments, the ceramic coating comprises aluminum oxide (Al ₂ O ₃ ) One or more of water and alumina (boehmite-gamma-AlOOH).

The ceramic coating has excellent mechanical strength, thereby improving the mechanical properties of the barrier film.

In some embodiments, the base film comprises one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, fiberglass, nonwoven, optionally polyethylene. In some embodiments, the base film comprises one or more of a polyethylene/polypropylene composite, a polypropylene/polyethylene/polypropylene composite.

In some embodiments, the barrier film comprises a base film and a coating on both sides of the base film, the coating on one side of the base film comprising an anti-overcharge coating, the coating on the other side of the base film not comprising an anti-overcharge coating.

In some embodiments, the barrier film includes a base film and a coating on both sides of the base film, the coating including an anti-overcharge coating and a ceramic coating between the anti-overcharge coating and the base film.

In some embodiments, the release film comprises a base film and a coating on both sides of the base film, the coating on one side of the base film comprising an anti-overcharge coating, the coating on the other side of the base film comprising a tie coat, the difference between the tie coat and the anti-overcharge coating being that the tie coat does not contain an anti-overcharge additive.

As shown in fig. 1, in some embodiments, the release film includes an overcharge-preventing coating 5231, a ceramic coating 5232, a base film 5233, a ceramic coating 5232, and an adhesive coating 5234, which are stacked in this order.

[ Positive electrode sheet ]

The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode active material layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, 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.).

In some embodiments, the positive electrode active material may employ a positive electrode active material for a battery, which is well known in the art.

In some embodiments, the positive electrode active material includes Li _d [Ni _x Co _y X1 _z M1 _1-x-y-z ]O ₂ 、LiMn ₂ O ₄ 、Li ₂ MnO ₃ ·(1-a)LiAO ₂ 、LiM2X2O ₄ One or more of the following;

The positive electrode active material in some embodiments of the present application is not limited to the substances included in the above general formula, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. The above general formula includes but is not limited to LiCoO ₂ 、LiNiO ₂ 、LiMnO ₂ 、LiMn ₂ O ₄ 、LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM) ₃₃₃ ）、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM) ₅₂₃ ）、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ ）、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ ）、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ）、LiNi _0.85 Co _0.15 Al _0.05 O ₂ Such as LiFePO ₄ (also abbreviated as LFP), liMnPO ₄ Composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate or composite material of lithium iron manganese phosphate and carbonAnd (5) material.

In some embodiments, the positive electrode active material 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.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

[ negative electrode sheet ]

The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector and containing at least a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, 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.).

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. The negative electrode active material may be used alone or in combination of two or more.

In some embodiments, the negative active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon carbon composite, lithium titanate, silicon oxygen composite.

In some embodiments, the anode active material layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

In some embodiments, the anode active material layer may further optionally include a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the anode active material layer may also optionally include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

[ electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

[ lithium Secondary Battery ]

In some embodiments, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator in some example embodiments.

In some embodiments, the overcharge protection coating is located between the positive electrode sheet and the base film.

As shown in fig. 1, in some embodiments, the secondary battery includes a positive electrode tab 521, a negative electrode tab 522, and a separator including an overcharge-preventing coating 5231, a ceramic coating 5232, a base film 5233, a ceramic coating 5232, and an adhesive coating 5234, which are sequentially stacked. And the overcharge-preventing coating 5231 is disposed facing the positive electrode sheet 521, and the adhesive coating 5234 is disposed facing the negative electrode sheet 522.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the operating voltage of the lithium secondary battery may be as high as 4.25 v-6 v.

It can be understood that when the battery is operated and charged in an overcharge voltage range higher than the normal operation voltage range of the secondary battery, the overcharge preventing additive is decomposed to generate gas, the resistance of the secondary battery is increased, the voltage is correspondingly and rapidly increased, the risk of thermal runaway is reduced, and the normal operation of the lithium secondary battery is ensured. Accordingly, the operating voltage of the lithium secondary battery in some embodiments of the present application is increased as compared to the conventional secondary battery.

In some embodiments, the lithium secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte as described above.

In some embodiments, the outer package of the lithium secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the lithium secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 2 is a lithium secondary battery 5 of a square structure as one example. The lithium secondary battery may be a sodium ion battery, a magnesium ion battery, or a potassium ion battery.

In some embodiments, referring to fig. 3, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.

[ Battery Module ]

In some embodiments, the lithium secondary batteries may be assembled into a battery module, and the number of lithium secondary batteries contained in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

Fig. 4 is a battery module 4 as an example. Referring to fig. 4, in the battery module 4, a plurality of lithium secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of lithium secondary batteries 5 are accommodated.

[ Battery pack ]

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 5 and 6 are battery packs 1 as an example. Referring to fig. 5 and 6, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[ electric device ]

In one embodiment of the present application, an electrical device is provided that includes at least one of some embodiments of a lithium secondary battery, some embodiments of a battery module, or some embodiments of a battery pack.

The electrical device includes at least one of a lithium secondary battery, a battery module, or a battery pack provided herein. The lithium secondary battery, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The power utilization device may include, but is not limited to, mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric only 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, and the like.

As the electricity consumption device, a lithium secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 7 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the lithium secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be thin and lightweight, and a lithium secondary battery can be used as a power source.

Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

1. Preparation method

Example 1

1) Preparation of a separator film

Weighing a certain amount of ceramic material Al ₂ O ₃ Dissolving in N-methyl-2-pyrrolidone to obtain ceramic material slurry. And coating ceramic material slurry on two opposite surfaces of the base film polyethylene through a gravure plate to prepare a ceramic coating, and drying and cutting after coating is finished to obtain a precursor of the isolating film.

Weighing a certain amount of binder polyvinylidene fluoride, dissolving in solvent N-methyl-2-pyrrolidone to obtain polyvinylidene fluoride solution, dividing the polyvinylidene fluoride solution into two parts, adding additive Li into one part of polyvinylidene fluoride solution ₂ C ₂ O ₄ Uniformly mixed (additive Li) ₂ C ₂ O ₄ The mass ratio of the coating slurry to the polyvinylidene fluoride is 0.5:9.5), and the coating slurry is obtained. Preparation of a coating slurry containing an overcharge-preventing additive Li by spraying on one side surface of a ceramic coating ₂ C ₂ O ₄ Another part of polyvinylidene fluoride solution is sprayed on the other side surface of the ceramic coating to prepare the anti-overcharge coating without additive Li ₂ C ₂ O ₄ And (3) drying and cutting after spraying to obtain the isolating film.

2) Preparation of positive electrode plate

1wt% of polyvinylidene fluoride binder is fully dissolved in N-methyl pyrrolidone, and then 1wt% of carbon black conductive agent and 98wt% of ternary positive electrode active material LiNi are added _1/3 Co _1/3 Mn _1/3 O ₂ Stirring and mixing uniformly to obtain the positive electrode slurry. The slurry is uniformly coated on the surface of a current collector aluminum foil to prepare a positive electrode film layer, and then transferred to a vacuum drying oven for complete drying. And rolling and punching the dried pole piece to obtain the positive pole piece.

3) Preparation of negative electrode plate

Mixing and dissolving negative active material artificial graphite, conductive agent carbon black, thickener carboxymethyl cellulose (CMC) and adhesive Styrene Butadiene Rubber (SBR) in a weight ratio of 96:2:1:1 into deionized water to prepare negative slurry, obtaining the negative slurry under the action of a vacuum stirrer, and coating the slurry on the surface of copper foil. And finally, transferring the electrode plate into a vacuum drying oven for complete drying, and rolling and punching the dried electrode plate to obtain the negative electrode plate.

4) Electrolyte solution

In an argon atmosphere glove box (H ₂ O<0.1ppm，O ₂ <0.1 ppm), 30% of ethylene carbonate and 60% of dimethyl carbonate were uniformly mixed to obtain a mixed solvent. Then 10% lithium hexafluorophosphate is added to dissolve in the mixed solvent, and the mixture is stirred uniformly and mixed to prepare the electrolyte.

5) Preparation of a Battery

Sequentially stacking a positive pole piece, a separation film and a negative pole piece, wherein the separation film is positioned at the positive side,The negative plates are isolated and contain an overcharge-preventing additive Li ₂ C ₂ O ₄ The overcharge-preventing coating is positioned at the side of the positive electrode plate, the electrode lug is welded on the bare cell, the bare cell is arranged in an aluminum shell, the aluminum shell is baked at 80 ℃ to remove water, the electrolyte is injected immediately, and the battery is sealed, so that the uncharged battery is obtained. The uncharged battery was subjected to the processes of standing, hot and cold pressing, formation, shaping, capacity test and the like in order, to obtain the lithium secondary battery product of example 1.

Examples 2 to 8

The battery preparation methods in examples 2 to 8 were basically similar to example 1, but the content of the overcharge-preventing additive in the overcharge-preventing coating layer and the kind of the overcharge-preventing additive were adjusted, and specific parameters are shown in table 1.

Example 9

The battery preparation method in example 9 was substantially similar to example 1, but the preparation method of the secondary battery was adjusted, and the specific preparation method was as follows:

Sequentially stacking a positive electrode plate, a separation film and a negative electrode plate, wherein the separation film is positioned between the positive electrode plate and the negative electrode plate to play a role in separation and contains an overcharge-preventing additive Li ₂ C ₂ O ₄ The overcharge-preventing coating is positioned at the side of the negative electrode plate, the electrode lug is welded on the bare cell, the bare cell is arranged in an aluminum shell, the aluminum shell is baked at 80 ℃ to remove water, and then the electrolyte is injected and sealed, so that the uncharged battery is obtained. The uncharged battery was subjected to the processes of standing, hot and cold pressing, formation, shaping, capacity test and the like in order, to obtain the lithium secondary battery product of example 1.

Example 10

The battery preparation method in example 10 was substantially similar to example 1, but the preparation methods of the separator and the secondary battery were adjusted, and specific preparation methods were as follows:

1) Preparation of a separator film

Weighing a certain amount of ceramic material Al ₂ O ₃ Dissolving in N-methyl-2-pyrrolidone to obtain ceramic material slurry. Coating ceramic material slurry on two opposite surfaces of base film polyethylene by gravure to prepare ceramic coating, drying and cutting after coating is completed,a release film precursor is obtained.

Weighing a certain amount of binder polyvinylidene fluoride, dissolving in solvent N-methyl-2-pyrrolidone to obtain polyvinylidene fluoride solution, and adding anti-overcharge additive Li ₂ C ₂ O ₄ Uniformly mixed (anti-overcharging additive Li) ₂ C ₂ O ₄ The mass ratio of the coating slurry to the polyvinylidene fluoride is 0.5:9.5), and the coating slurry is obtained. Preparation of an anti-overcharge additive Li by spraying a bonding slurry onto both surfaces of a ceramic coating ₂ C ₂ O ₄ And (3) the anti-overcharging coating is dried and cut after the spraying is finished, so that the isolating film is obtained. The bond coat thickness on both sides of the base film is equal.

5) Preparation of a Battery

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, wherein the isolating film plays a role in isolating between the positive electrode plate and the negative electrode plate, welding the electrode lugs for the bare cell, loading the bare cell into an aluminum shell, baking at 80 ℃ for dewatering, injecting the electrolyte, and sealing to obtain the uncharged battery. The uncharged battery was subjected to the processes of standing, hot and cold pressing, formation, shaping, capacity test and the like in order, to obtain the lithium secondary battery product of example 1.

Example 11

The battery preparation method in example 11 was substantially similar to example 1, but the preparation method of the separator was adjusted, and the specific preparation method was as follows:

Weighing a certain amount of binder polyvinylidene fluoride, dissolving in solvent N-methyl-2-pyrrolidone to obtain polyvinylidene fluoride solution, and adding anti-overcharge additive Li ₂ C ₂ O ₄ Uniformly mixed (anti-overcharging additive Li) ₂ C ₂ O ₄ The mass ratio of the coating slurry to the polyvinylidene fluoride is 0.5:9.5), and the coating slurry is obtained. Passing the coating slurry throughPreparation of anti-overcharging additive Li by spraying on one side surface of ceramic coating ₂ C ₂ O ₄ And (3) the anti-overcharging coating is dried and cut after the spraying is finished, so that the isolating film is obtained.

Comparative example 1

The battery preparation method in comparative example 1 was substantially similar to example 1, but the preparation method of the separator was adjusted as follows:

and weighing a certain amount of binder polyvinylidene fluoride, dissolving the binder polyvinylidene fluoride in a solvent N-methyl-2-pyrrolidone to obtain a polyvinylidene fluoride solution, spraying the polyvinylidene fluoride solution on two opposite surfaces of the base film polyethylene to prepare a bonding coating, and drying and cutting after spraying to obtain the isolating film.

Comparative example 2

The battery preparation method in comparative example 2 was substantially similar to example 2, but the preparation method of the separator was adjusted as follows:

Weighing a certain amount of binder polyvinylidene fluoride, dissolving the binder polyvinylidene fluoride in solvent N-methyl-2-pyrrolidone to obtain polyvinylidene fluoride solution, spraying the polyvinylidene fluoride solution on two opposite surfaces of a ceramic coating to prepare a bonding coating, and drying and cutting after spraying to obtain the isolating film.

Comparative example 3

The battery preparation method in comparative example 3 was substantially similar to comparative example 2, but the positive electrode sheet preparation method was adjusted as follows:

fully dissolving 10wt% of polyvinylidene fluoride binder in N-methyl pyrrolidone, and adding 40wt% of carbon black conductive agent and 50wt% of anti-overcharge additive Li ₂ C ₂ O ₄ Stirring and mixing uniformly to obtain a first positive electrode slurry (an overcharge-preventing additive Li in the first positive electrode slurry ₂ C ₂ O ₄ The amount of (3)The overcharge-preventing additive Li in the separator of example 1 ₂ C ₂ O ₄ The same amount of the used amount), uniformly coating the first positive electrode slurry on the surface of the aluminum foil of the current collector to prepare a first positive electrode film layer; then, 1wt% of polyvinylidene fluoride binder is fully dissolved in N-methyl pyrrolidone, and then 1wt% of carbon black conductive agent and 98wt% of ternary positive electrode active material LiNi are added _1/3 Co _1/3 Mn _1/3 O ₂ Uniformly stirring and mixing to obtain second positive electrode slurry, uniformly coating the second positive electrode slurry on the surface of the aluminum foil of the current collector to prepare a second positive electrode film layer, wherein the thickness of the first positive electrode film layer and the second positive electrode film layer is controlled at 1:200, and then transferred to a vacuum drying oven for complete drying. And rolling and punching the dried pole piece to obtain the positive pole piece.

2. Performance testing

1. Battery performance test

1) Pass rate test

The lithium secondary batteries prepared using examples and comparative examples were subjected to stability test in which the lithium secondary batteries were charged at 0.1C small rate for two hours at 100% soc (full charge) state. In this case, the lithium secondary battery was evaluated as "passing (V)" when the voltage of the lithium secondary battery reached 8V without heat generation, gas generation or explosion, and as "failed (x)" when the secondary battery did not reach the above voltage with heat generation, gas generation, smoke generation or explosion. The test procedure for the comparative example and the other examples is the same as above.

2) Direct current impedance (DCR) test

The prepared battery was charged to 5.0V at a constant current of 1/3C at 25C, and then charged to 0.05C at a constant voltage of 5.0V, and after resting for 5min, the voltage V1 was recorded. Then discharging for 30s at 1/3C, and recording the voltage V2, so that the internal resistance DCR1= (V2-V1)/(1/3C) of the battery after the first cycle. Repeating the steps for the same battery, and recording the internal resistance DCRn of the battery after 50 times of overcharge cycles. The test procedure for the comparative example and the other examples is the same as above.

3) Cycle capacity retention rate

The prepared battery was charged to 4.4V (ternary active material)/3.6V (lithium iron phosphate) at a constant current of 1/3C at 25 ℃, then charged to 0.05C at a constant voltage of 4.4V (ternary active material)/3.6V (lithium iron phosphate), left to stand for 5min, and then discharged to 2.5V at 1/3C, and the resulting capacity was recorded as an initial capacity C0. Then, the charge upper line voltage was adjusted to 5V, the discharge lower limit voltage was 2.5V, and the above steps were repeated for the same battery, and the discharge capacity Cn of the battery after the 50 th cycle was recorded at the same time, so that the battery capacity retention rate after the cycle was pn=cn/c0×100%. The test procedure for the comparative example and the other examples is the same as above.

3. Analysis of test results for examples and comparative examples

Batteries of each example and comparative example were prepared according to the above-described methods, and each performance parameter was measured, and the results are shown in tables 1 and 2 below.

TABLE 1

TABLE 2

From the above results, it is understood that the separator in examples 1 to 11 includes a base film and an anti-overcharge coating layer located on at least one side of the base film, and the anti-overcharge coating layer includes an anti-overcharge additive.

As can be seen from the comparison of examples 1-5, 7-10 and comparative example 2, the barrier film in the present example includes an overcharge preventing additive comprising Li, as compared to the barrier film not including an overcharge preventing additive ₂ C ₂ O ₄ 、Li ₂ C ₃ O ₅ Or Li (lithium) ₂ C ₃ O ₅ The method can pass the overcharge test, and the cycle capacity retention rate is greatly improved.

As can be seen from the comparison of examples 1, 9 to 10 and comparative example 3, compared with the introduction of the overcharge-preventing additive Li in the positive electrode sheet ₂ C ₂ O ₄ In the embodiment of the application, the anti-overcharge additive Li is introduced into the isolating film ₂ C ₂ O ₄ Is favorable toReducing the direct current impedance of the battery.

As can be seen from the comparison of examples 1 to 10 and comparative example 1, in the examples of the present application, the overcharge-preventing additive Li was simultaneously introduced into the separator ₂ C ₂ O ₄ And a ceramic coating, which facilitates the improvement of the cycle capacity retention under overcharge conditions.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

1. A separator comprising a base film and an anti-overcharge coating on at least one side of the base film, the anti-overcharge coating comprising an anti-overcharge additive comprising a lithium-containing compound.

2. The separator of claim 1, wherein the lithium-containing compound comprises Li ₂ C ₂ O ₄ 、Li ₂ C ₄ O ₄ 、Li ₂ C ₃ O ₅ 、Li ₂ C ₄ O ₆ 、LiN ₃ One or more of the following.

3. The separator of claim 1, wherein the lithium-containing compound comprises Li ₂ C ₂ O ₄ 、LiN ₃ One or more of the following.

4. The release film of claim 1, wherein the anti-overcharge coating further comprises a binder comprising one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymers, polyacrylamides, polyurethanes, poly (acrylonitrile-acrylate), polyacrylates, poly (styrene-acrylate).

5. The separator of claim 4 wherein said binder comprises polyvinylidene fluoride.

6. The barrier film according to claim 1, wherein the mass content of the overcharge preventing additive is 0.5% -15% based on the total mass of the overcharge preventing coating.

7. The barrier film according to claim 1, wherein the mass content of the overcharge preventing additive is 1 to 10% based on the total mass of the overcharge preventing coating.

8. The separator of claim 1, wherein the ratio of the thickness of the anti-overcharge coating to the thickness of the separator is (0.05-0.6): 1.

9. The separator of claim 1, wherein the ratio of the thickness of the anti-overcharge coating to the thickness of the separator is (0.1-0.5): 1.

10. The barrier film of claim 1, wherein the overcharge-preventing coating has a thickness of 0.35-18 μm.

11. The barrier film of claim 1, wherein the anti-overcharge coating has a thickness of 1 μm to 10 μm.

12. The isolating membrane according to claim 1, characterized in that the thickness of the isolating membrane is 7-30 μm.

13. The isolating membrane according to claim 12, characterized in that the thickness of the isolating membrane is 9-20 μm.

14. The barrier film of any one of claims 1 to 13, further comprising a ceramic coating between the base film and the anti-overcharge coating.

15. The separator of claim 14, wherein the ceramic coating comprises one or more of alumina, hydrated alumina.

16. The separator of any one of claims 1 to 13, wherein the base film comprises one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, fiberglass, nonwoven.

17. The separator film according to any one of claims 1 to 13, wherein the base film comprises one or more of polyethylene, polypropylene.

18. The separator of any one of claims 1 to 13, wherein the separator comprises a base film and a coating on both sides of the base film, the coating on one side of the base film comprising the anti-overcharge coating, the coating on the other side of the base film not comprising the anti-overcharge coating.

19. A lithium secondary battery comprising a positive electrode tab, a negative electrode tab, and the separator of any one of claims 1 to 18.

20. The lithium secondary battery of claim 19, wherein the overcharge-preventing coating is located between the positive electrode sheet and the base film.

21. The lithium secondary battery according to claim 19 or 20, wherein the positive electrode sheet comprises a positive electrode active material, the positive electrode active materialThe material comprises Li _d [Ni _x Co _y X1 _z M1 _1-x-y-z ]O ₂ 、LiMn ₂ O ₄ 、Li ₂ MnO ₃ ·(1-a)LiAO ₂ 、LiM2X2O ₄ One or more of the following;

22. An electric device comprising the lithium secondary battery according to any one of claims 19 to 21.