Secondary battery and electrical apparatus

Abstract

The present application provides a secondary battery and an electrical apparatus. The secondary battery comprises an electrolyte and a separator, the separator comprising a base film and a coating located on at least one side of the base film. The secondary battery satisfies: 0.5≤G×H / (10×σ)≤13; G is the Gurley value of the base film, the unit being s; H is the thickness of the coating, the unit being μm; and σ is the conductivity of the electrolyte at 25℃, the unit being mS / cm. The secondary battery achieves both safety and fast charging performance.

Description

Secondary batteries and electrical devices

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202311510581.9, filed on November 14, 2023, entitled “Secondary Batteries and Electrical Devices,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the technical field of sodium batteries, and in particular to a secondary battery and an electrical device. Background Art

[0004] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0005] With the increasing popularity of secondary batteries, consumers are increasingly demanding higher safety and fast-charging performance. Improving secondary battery safety can affect its fast-charging performance. For example, the separator can prevent internal short circuits in the secondary battery by blocking contact between the positive and negative electrodes. Improving the tensile strength of the separator can improve the safety of the secondary battery. However, this reduces the ability of active ions such as lithium and sodium ions to pass through the separator, resulting in a decrease in the fast-charging performance of the secondary battery. This makes it impossible to strike a balance between safety and fast-charging performance, and therefore cannot meet the application needs of the next generation of electrochemical systems.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its object is to provide a secondary battery that can achieve both safety and fast charging performance.

[0008] A first aspect of the present application provides a secondary battery, comprising an electrolyte and a separator, wherein the separator comprises a base film and a coating applied to at least one side of the base film;

[0009] The secondary battery satisfies: 0.5≤G×H / (10×σ)≤13, where G is the Gurley value of the base film, in s; H is the thickness of the coating, in μm; σ is the conductivity of the electrolyte at 25°C, in mS / cm.

[0010] Increasing the Gurley value of the base film or increasing the thickness of the coating is beneficial to improving the tensile strength of the secondary battery, thereby improving the safety of the secondary battery. However, increasing the Gurley value of the base film or increasing the thickness of the coating will also affect the transport performance of active ions. Increasing the conductivity of the electrolyte can improve the ion transport performance of the secondary battery, but increasing the conductivity of the electrolyte will also bring safety hazards and affect safety. This application controls the Gurley value of the base film, the thickness H of the coating, and the conductivity σ of the electrolyte at 25°C to satisfy the above relationship, so that the secondary battery has good fast charging performance and reduces the safety hazards caused by excessive electrolyte conductivity, taking into account both the safety and fast charging performance of the secondary battery.

[0011] In any embodiment, the secondary battery satisfies: 0.9≤G×H / (10×σ)≤10, which not only takes into account the safety and fast charging performance of the secondary battery, but also helps to improve the cycle performance.

[0012] In any embodiment, the secondary battery further satisfies: 6≤G / σ≤43, optionally 11≤G / σ≤33.

[0013] By controlling the Gurley value of the base membrane and the conductivity σ of the electrolyte at 25°C to satisfy the above-mentioned relationship, the influence of the increase in the Gurley value of the base membrane on the ion transport performance of the secondary battery and the influence of the increase in the conductivity of the electrolyte at 25°C on the safety of the secondary battery can be simultaneously weakened, thereby further comprehensively improving the safety and fast charging performance of the secondary battery.

[0014] In any embodiment, the Gurley value G of the base film satisfies: 100s≤G≤300s, and can be optionally 110s≤G≤300s.

[0015] Controlling the Gurley value of the base membrane within an appropriate range can not only reduce the risk of the isolation membrane breaking during production or the risk of safety accidents during recycling due to the low tensile strength of the isolation membrane caused by the low Gurley value of the base membrane, but also reduce the impact of the excessive Gurley value of the base membrane on the ion transmission performance.

[0016] In any embodiment, the thickness H of the coating is: 0.5 μm≤H≤5.1 μm, optionally 0.8 μm≤H≤4.2 μm.

[0017] Controlling the thickness of the coating within an appropriate range is beneficial to improving the safety of the secondary battery and reducing the impact of excessive coating thickness on ion transmission performance.

[0018] In any embodiment, the conductivity σ of the electrolyte at 25° C. satisfies: 7 mS / cm≤σ≤15 mS / cm, and may be 8 mS / cm≤σ≤12.5 mS / cm.

[0019] Controlling the conductivity of the electrolyte at 25°C within an appropriate range is beneficial to improving the ion transport performance of the secondary battery and improving the fast charging performance of the secondary battery, while also reducing the impact of increased gas production caused by excessively high electrolyte conductivity on the safety of the secondary battery.

[0020] In any embodiment, the porosity of the separator is 30% to 50%, and can be optionally 35% to 50%. The porosity of the separator is within a suitable range to ensure a good transmission rate of active ions and an ideal mechanical strength of the separator, while taking into account the fast charging performance and safety of the secondary battery.

[0021] In any embodiment, the base film comprises one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, glass fiber, and non-woven fabric. The above substances (or materials) have good tensile properties and air permeability when prepared as a base film, and the Gurley value of the base film can be well controlled, thereby ensuring excellent safety of the secondary battery.

[0022] In any embodiment, the coating comprises at least one of an organic coating and a ceramic coating.

[0023] In any embodiment, the coating includes an organic coating and a ceramic coating; wherein the ceramic coating includes one or more of Al2O3, AlO(OH), SiO2, TiO2, MgO, CaO, ZnO2, ZrO2, and SnO2; and the organic coating includes one or more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyamide, polyacrylonitrile, polyacrylate, polyacrylate, and sodium hydroxymethyl cellulose.

[0024] The ceramic coating in the coating is beneficial to improving the tensile strength and puncture resistance of the isolation membrane, preventing the isolation membrane from shrinking or short circuits caused by active metal dendrites piercing the isolation membrane, and improving the safety of the secondary battery; the organic coating has good thermal stability, which can improve the overall thermal stability of the isolation membrane and further improve the safety performance of the secondary battery.

[0025] In any embodiment, the coating comprises 15% to 100% of polyvinylidene fluoride (PVDF) or 55% to 100% of Al2O3. The coating has good mechanical strength and thermal stability, which is beneficial to the safety of long-term cycling of secondary batteries.

[0026] In any embodiment, the electrolyte includes a solvent, and the solvent includes one or more of a carbonate solvent, an ether solvent, and a linear carboxylate solvent; wherein,

[0027] Carbonate solvents include one or more of ethylene carbonate, dimethyl carbonate, propylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, and diethyl carbonate;

[0028] The ether solvent includes one or more of dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, 1,2-diethoxyethane, and 1,2-dibutoxyethane;

[0029] The linear carboxylate solvent includes one or more of methyl formate, ethyl formate, methyl propionate, ethyl propionate, propyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, and propyl acetate.

[0030] The solvent has low viscosity, which is beneficial to reducing the viscosity of the electrolyte and reducing the resistance to lithium ion transmission, thereby improving the conductivity of the electrolyte.

[0031] In any embodiment, the secondary battery includes at least one of a sodium secondary battery and a lithium secondary battery.

[0032] A second aspect of the present application provides an electrical device comprising the secondary battery of the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0034] FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;

[0035] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0036] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0037] FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;

[0038] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0039] Explanation of reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0040] Below, the embodiments of the secondary battery and the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0041] " scope " disclosed in the application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can include end value or do not include end value, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all 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.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0045] Unless otherwise specified, the terms "include" and "comprising" used in this application 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.

[0046] Unless otherwise specified, the term "or" is used in this application to be 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 if any of the following conditions are met: 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).

[0047] The separator in a secondary battery blocks contact between the positive and negative electrodes, preventing internal short circuits. Its micropores allow active ions to pass through, enabling the battery to function properly. Generally, the higher the separator's tensile strength, the safer the secondary battery. However, this makes it more difficult for active ions to pass through the separator, resulting in reduced ion transport and impacting the battery's fast-charging performance. Therefore, it is necessary to design a secondary battery that balances safety and fast-charging performance to meet the application needs of the next generation of electrochemical systems.

[0048] [Secondary battery]

[0049] During battery cycling, active ions (e.g., Na + , Li + ) escapes from the positive electrode side of the secondary battery, is transported through the electrolyte, passes through the isolation membrane and is embedded in the negative electrode side. Therefore, the transmission performance of active ions in the electrolyte and the isolation membrane jointly affects the fast charging performance of the secondary battery.

[0050] The secondary battery provided in the present application includes an electrolyte and an isolation membrane, the isolation membrane includes a base membrane and a coating coated on at least one side of the base membrane; the secondary battery satisfies: 0.5≤G×H / (10×σ)≤13, wherein G is the Gurley value of the base membrane, in s; H is the thickness of the coating, in μm; σ is the conductivity of the electrolyte at 25°C, in mS / cm.

[0051] In the separator, the base membrane provides a channel for active ions to pass through, so that the secondary battery can function normally. In this article, the term "Gurley value" is used to characterize the air permeability of the base membrane, which refers to the air permeability of 100mL of air passing through an area of ​​6.45cm at a pressure of 1.24kPa. 2The Gurley value of the base membrane affects the tensile strength of the separator and the ease with which active ions can pass through it. A higher Gurley value increases the tensile strength of the separator, but reduces the ability of active ions to pass through the base membrane, resulting in lower ion transport performance and impacting the fast-charging performance of the secondary battery.

[0052] The coating in the separator can increase the separator's tensile strength and improve its ability to be pierced by active metal dendrites. However, increasing the coating thickness also makes it more difficult for active ions to pass through the separator, affecting ion transport performance and the fast charging performance of the secondary battery.

[0053] When active ions pass through the isolation membrane, they pass through the coating applied to the base membrane and the base membrane in sequence. Therefore, the efficiency of active ions passing through the isolation membrane or the ion transmission performance is affected by both the Gurley value of the base membrane and the thickness of the coating.

[0054] The tensile strength of the isolation film can be enhanced by increasing the Gurley value of the base film and / or the thickness of the coating. In some embodiments, the tensile strength can be reflected by detecting the thermal shrinkage rate of the isolation film to show the change in tensile strength. Generally, the thermal shrinkage rate of the isolation film can be reduced after the tensile strength is improved. In this article, the term "thermal shrinkage rate" refers to the shrinkage rate of the isolation film area when heated to a set temperature. For example, the thermal shrinkage rate can be tested by the following method: spread an isolation film with an area of ​​S1 on a marble table, adjust the temperature of the heat gun to 200°C, and then irradiate the isolation film at a set distance for 0.5h. After cooling, measure the area S2 of the isolation film. The thermal shrinkage rate of the isolation film = S2 / S1×100%.

[0055] The thermal shrinkage of the separator can affect the thermal runaway temperature of the secondary battery, and thus affect the safety of the secondary battery. The "thermal runaway temperature" refers to the temperature at which the battery cell of the secondary battery thermally runs away, and the thermal runaway temperature can indicate the safety of the secondary battery.

[0056] When a secondary battery is heated to a certain temperature, the separator shrinks. Excessive thermal shrinkage prevents the separator from effectively separating the positive and negative electrodes, leading to an internal short circuit. Heat is released at the short point, causing the electrodes to burn and the battery cell to ignite and explode. Lowering the separator's thermal shrinkage helps raise the short-circuit trigger temperature, or thermal runaway temperature, for secondary batteries, thereby improving battery safety.

[0057] In this article, the thermal runaway temperature T can be tested using any known means. As an example, the following test method can be used: at 25°C, charge the prepared battery at 1C to 4.25V, then charge at a constant voltage of 4.25V until the current drops to 0.05C. The battery is then placed in a heating furnace and heated at 5°C / min to 100°C and held for 30 minutes. Thereafter, the temperature is increased by 10°C for 30 minutes until the battery cell experiences thermal runaway. The temperature T at the time of thermal runaway is recorded.

[0058] In this article, the term "conductivity" refers to the ability of active ions to conduct electricity in the liquid phase. Active ions move and transport in the electrolyte. The higher the conductivity, the higher the conductivity of the active ions in the electrolyte, which is more conducive to improving the fast-charging performance of the secondary battery. However, as the conductivity increases, the gas generated in the electrolyte due to solvent side reactions (such as oxidation reactions) also increases accordingly, causing the secondary battery to bloat, which indirectly leads to the local precipitation of active metals in the secondary battery. Active metal dendrites gradually grow and may puncture the separator, creating the safety risk of battery short circuit.

[0059] In addition, the detection temperature "25° C." in the "electrical conductivity of the electrolyte at 25° C." herein may fluctuate to a degree acceptable to those skilled in the art, for example, within a fluctuation range of ±0.1° C.

[0060] It's understandable that increasing the base film Gurley value and coating thickness has the opposite effect on active ion transport performance than increasing electrolyte conductivity. Therefore, the ratio G×H / (10×σ) can reflect the active ion transport performance of a secondary battery. A suitable ratio helps secondary batteries achieve both ion transport performance and safety.

[0061] In some embodiments, G×H / (10×σ) can be selected as 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or a value in a range consisting of any two of the above points.

[0062] In this document, the Gurley value G of the base film can be measured using any known method. For example, the test is performed with reference to the standard GB / T 36363-2018. For example, a Gurley 4320N air permeability tester can be used.

[0063] In some embodiments, the Gurley value of the basement membrane can be measured using the following method:

[0064] Cut the base film into 6.45cm2 areas at intervals of 150mm along the longitudinal direction (maximum dimension direction) 2The test sample is placed in a permeability meter and the time it takes for 100 mL of air to pass through the base membrane at a pressure of 1.24 kPa is measured, which is the Gurley value.

[0065] The average value of the test results of multiple (for example, 3) parallel samples can be taken as the Gurley value of the isolation film.

[0066] Herein, the thickness H of the coating can be measured by any known means.

[0067] As an example, a Marr film thickness gauge is used to test the thickness H1 of the base film.

[0068] Then measure the thickness H2 of the isolation film, and the thickness of the coating H=H2-H1.

[0069] The average value of the coating thickness test results at any multiple (eg, 10) detection points on the isolation film sample can be used as the coating thickness.

[0070] In this document, the conductivity σ of the electrolyte at 25°C can be tested using any known means. As an example, the electrolyte testing method may include: maintaining the test sample and standard liquid at a constant temperature of 25°C (±0.1°C), calibrating the test instrument (Leci DDSJ-308F) using two standard liquids at an ambient temperature of 25°C (±0.5°C), and after calibration and cleaning the electrodes, placing the test sample electrode vertically into the test liquid to begin testing. The test result is recorded after the data stabilizes for more than 10 seconds.

[0071] It is understood that by controlling the Gurley value of the base film, the coating thickness H, and the electrolyte conductivity σ at 25°C to satisfy the above relationship, the present application provides the separator with good tensile strength and suitable active ion permeability, reducing the safety risks brought by high conductivity. At the same time, good electrolyte conductivity improves the transport performance of active ions and improves the fast-charging performance of the secondary battery. The interaction and influence of these three factors enables the secondary battery to achieve both safety and fast-charging performance.

[0072] Further controlling the Gurley value of the base film, the thickness H of the coating, and the conductivity σ of the electrolyte at 25°C to satisfy 0.9≤G×H / (10×σ)≤10 can not only take into account the safety and fast charging performance of the secondary battery, but also help improve the cycle performance.

[0073] In some embodiments, the secondary battery further satisfies: 6≤G / σ≤43. A suitable ratio of the Gurley value of the base membrane to the electrolyte conductivity helps control the active ions to have good transport performance and reduces the impact of high conductivity on battery safety.

[0074] In some embodiments, G / σ can be selected as 6, 6.7, 7, 8, 8.3, 10, 12, 14, 15, 16, 18, 20, 22, 24, 25, 26, 28, 30, 32, 33, 34, 35, 36, 37.5, 38, 40, 42, or a value in a range consisting of any two of the above points.

[0075] In some embodiments, the ratio of the Gurley value of the base membrane and the conductivity of the electrolyte satisfies 11≤G / σ≤33. Controlling the ratio of the Gurley value of the base membrane and the conductivity σ of the electrolyte at 25°C within the said range can simultaneously reduce the effect of the increase in the Gurley value of the base membrane on the ion transport performance of the secondary battery and the effect of the increase in the conductivity of the electrolyte at 25°C on the safety of the secondary battery, thereby further improving the safety and fast charging performance of the secondary battery.

[0076] In some embodiments, the Gurley value G of the base film satisfies: 100s≤G≤300s. In some embodiments, the Gurley value G of the base film satisfies: 110s≤G≤300s. In some embodiments, the Gurley value G of the base film can be 100s, 110s, 120s, 140s, 150s, 160s, 180s, 200s, 210s, 220s, 240s, 250s, 260s, 280s, 300s, or a value in a range consisting of any two of the above.

[0077] Controlling the Gurley value of the base membrane within an appropriate range can not only reduce the risk of the isolation membrane breaking during production or the risk of safety accidents during recycling due to the low tensile strength of the isolation membrane caused by the low Gurley value of the base membrane, but also reduce the impact of the excessive Gurley value of the base membrane on the ion transmission performance.

[0078] In some embodiments, the thickness H of the coating is: 0.5 μm ≤ H ≤ 5.1 μm. In some embodiments, the thickness H of the coating is: 0.8 μm ≤ H ≤ 4.2 μm. In some embodiments, the thickness H of the coating can be selected from 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a value in a range consisting of any two of the foregoing values.

[0079] Controlling the thickness of the coating within an appropriate range is beneficial to improving the safety of the secondary battery and reducing the impact of excessive coating thickness on ion transmission performance.

[0080] In some embodiments, the conductivity σ of the electrolyte at 25° C. satisfies: 7 mS / cm≤σ≤15 mS / cm. In some embodiments, the conductivity σ of the electrolyte at 25° C. satisfies: 8 mS / cm≤σ≤12.5 mS / cm.

[0081] In some embodiments, the conductivity σ of the electrolyte at 25° C. may be 7 mS / cm, 8 mS / cm, 9 mS / cm, 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, or a value in a range consisting of any two of the above points.

[0082] Controlling the conductivity of the electrolyte at 25°C within an appropriate range is beneficial to improving the ion transport performance of the secondary battery, that is, improving the fast charging performance of the secondary battery, and reducing the impact of increased gas production due to excessively high electrolyte conductivity on the safety of the secondary battery.

[0083] The separator in a secondary battery has micropores that allow active ions to pass through, separating the positive and negative electrodes to prevent internal short circuits and maintain normal operation of the secondary battery. In some embodiments, the separator has a porosity of 35% to 50%. A porosity within this range helps improve the transport of active ions and maintain the separator's excellent mechanical properties.

[0084] In some embodiments, the porosity of the isolation membrane can be selected to be 30%, 32%, 34%, 35%, 36%, 38%, 40%, 42%, 44%, 45%, 46%, 48%, 50%, or a value in the range consisting of any two of the above points.

[0085] The porosity of the isolation membrane is in the range of 30% to 50%, which allows active ions to pass through the isolation membrane quickly, giving the secondary battery ideal rate performance; at the same time, the isolation membrane also has good mechanical strength, reducing the risk of breakage during production or recycling.

[0086] In some embodiments, the base film includes one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, glass fiber, and non-woven fabric, and optionally includes one or more of polyethylene and polypropylene.

[0087] In some embodiments, the base film comprises polyethylene. In some embodiments, the base film comprises polypropylene. In some embodiments, the base film comprises polyethylene and polypropylene.

[0088] The above substances (or materials) all have relatively suitable Gurley values ​​as base films, are widely available, and have controllable costs, which helps to reduce the production cost of secondary batteries.

[0089] In some embodiments, the coating comprises an organic coating and / or a ceramic coating.

[0090] In some embodiments, the ceramic coating comprises one or more of Al2O3, AlO(OH), SiO2, TiO2, MgO, CaO, ZnO2, ZrO2, SnO2. In some embodiments, the ceramic coating comprises Al2O3.

[0091] The ceramic coating is beneficial for improving the tensile strength and puncture resistance of the separator, preventing the separator from shrinking or short circuit caused by active metal dendrites piercing the separator, and improving the safety of the secondary battery.

[0092] In some embodiments, the organic coating comprises one or more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyamide, polyacrylonitrile, polyacrylate, polyacrylate, sodium hydroxymethyl cellulose. In some embodiments, the organic coating comprises polyvinylidene fluoride.

[0093] The organic coating has high thermal stability, can isolate the overall thermal stability of the membrane, and further improve the safety performance of the battery.

[0094] In some embodiments, the coating comprises an organic coating and / or a ceramic coating. In some embodiments, the coating is an organic coating. In some embodiments, the coating is a ceramic coating.

[0095] The coating comprises PVDF accounting for 15% to 100% of the total mass of the coating, or Al2O3 accounting for 55% to 100% of the total mass of the coating.

[0096] In some embodiments, the coating comprises PVDF accounting for 15% to 45% of the total mass of the coating, and / or Al2O3 accounting for 55% to 85% of the total mass of the coating.

[0097] The coating including the organic coating and the ceramic coating has good tensile strength and thermal stability, and has both mechanical strength and thermal stability, which is beneficial to the long-term cycle safety of the secondary battery.

[0098] The mass contents of PVDF and Al2O3 in the coating can be determined using any method known or commonly used in the art. For example, the PVDF content can be determined by scraping the separator coating and weighing it to obtain a mass m1. Surface elemental analysis (EDS) is used to determine the fluorine content W1% in the separator containing the coating. The mass of fluorine in the separator coating = m1 × W1%, the mass of PVDF in the coating = m1 × W1% / (fluorine atomic weight / PVDF molecular weight), and the PVDF content = W1% / (fluorine atomic weight / PVDF molecular weight). The Al2O3 content can be determined using the same method.

[0099] [Positive electrode]

[0100] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0101] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0102] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0103] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art.

[0104] In some embodiments, the positive electrode active material includes Li d [Ni x Co y X1 z M1 1-x-y- z ]O2, LiMn2O4, Li2MnO3·(1-a)LiAO2, LiM2X2O4 or one or more;

[0105] Wherein, 0.1≤d≤1, X1 includes Mn and / or Al; M1 includes one or more of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Ti, 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1; A includes one or more of Ni, Co, Mn, 0<a<1; M2 includes one or more of Fe, Mn, Ni, Co; X2O4 h- X2 includes one or more of S, P, As, V, Mo, and W, and h=2 or 3.

[0106] In some embodiments of the present application, the positive electrode active material is not limited to the substances included in the above general formula, and other traditional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. The above general formula includes but is not limited to LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), LiNi 0.85 Co 0.15 Al 0.05 O2, such as LiFePO4 (also referred to as LFP), LiMnPO4, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate or a composite material of lithium iron manganese phosphate and carbon.

[0107] In some embodiments, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material for batteries well-known in the art. As an example, the positive electrode active material may include at least one of the following materials: layered transition metal oxides, polyanion compounds, or Prussian blue compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, the Prussian blue compound includes Na x P[R(CN)6] δ ·zH2O, where P and R are each independently selected from at least one of transition metal elements, 0 < x ≤ 2, 0 < δ ≤ 1 and 0 ≤ z ≤ 10; the polyanion compound includes Na b Me c (PO4) d O2X, where Me includes one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, X includes one or more of F, Cl, and Br, 0 < b ≤ 4, 0 < c ≤ 2, 1 ≤ d ≤ 3; the general formula of the layered transition metal oxide is Na x Mn<00,00041>Fe b Ni c M d N e O 2-δ Q f , where M includes at least one of Ti, Li, V, Cr, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, Mg, and Al, N includes at least one of Si, P, B, and S, Q includes at least one of F, Cl, and N, 0.66 ≤ x ≤ 1, 0 < a ≤ 0.7, 0 < b ≤ 0.7, 0 ≤ c ≤ 0.23, 0 ≤ d < 0.3, 0 ≤ e ≤ 0.3, 0 ≤ f ≤ 0.3, 0 ≤ δ ≤ 0.3, a + b + c + d + e = 1, 0 < e + f ≤ 0.3, 0 < (e + f) / a ≤ 0.3, 0.2 ≤ d + e + f ≤ 0.3, (b + c) / a ≤ 1.5.

[0108] In some embodiments, the positive electrode active material layer may also 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.

[0109] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, 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 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.

[0110] [Negative electrode]

[0111] The negative electrode sheet 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.

[0112] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0113] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0114] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art. The negative electrode active material may be used alone or in combination of two or more.

[0115] In some embodiments, the negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-carbon composite, lithium titanate, and silicon-oxygen composite.

[0116] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of 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).

[0117] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0119] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0120] [Electrolytes]

[0121] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0122] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0123] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0124] In some embodiments, the electrolyte includes a sodium salt, and the sodium salt includes one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium dioxalatoborate, and sodium difluorooxalatoborate.

[0125] In some embodiments, the electrolyte includes a solvent, and the solvent includes one or more of carbonate solvents, ether solvents, and carboxylate solvents, and optionally includes one or more of carbonate solvents and linear carboxylate solvents.

[0126] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, propylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, and diethyl carbonate.

[0127] In some embodiments, the ether solvent includes one or more of dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, 1,2-diethoxyethane, and 1,2-dibutoxyethane.

[0128] In some embodiments, the linear carboxylate solvent includes one or more of methyl formate, ethyl formate, methyl propionate, ethyl propionate, propyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, and propyl acetate.

[0129] The solvent has a relatively low viscosity and can reduce the viscosity of the electrolyte after being added to the electrolyte, thereby reducing the lithium ion transmission resistance and improving the conductivity of the electrolyte.

[0130] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0131] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0132] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0133] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0134] The present application has no particular restrictions on the shape of the secondary battery, which can be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 5 having a square structure as an example. The secondary battery can also be a sodium secondary battery or a lithium secondary battery.

[0135] In some embodiments, referring to FIG2 , the outer package may include a shell 51 and a cover plate 53. The shell 51 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 51 has an opening connected to the receiving cavity, and the cover plate 53 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 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0136] [Battery Module]

[0137] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0138] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0139] In some embodiments, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 may be received in the receiving space.

[0140] [Battery Pack]

[0141] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0142] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0143] [Electrical devices]

[0144] In one embodiment of the present application, an electric device is provided, comprising at least one of the secondary battery of some embodiments, the battery module of some embodiments, or the battery pack of some embodiments.

[0145] The electrical device includes at least one of the secondary battery, battery module, or battery pack provided in this application. 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 may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0146] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0147] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0148] 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.

[0149] Example

[0150] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0151] 1. Preparation method

[0152] Example 1

[0153] 1) Isolation film

[0154] A polyethylene film with a Gurley value of 160s (SU07, Hebei Jinli New Energy Technology Co., Ltd.) was used as the base film. 15 g of Al2O3 was weighed and dissolved in 85 g of N-methyl-2-pyrrolidone (NMP) to prepare a ceramic coating slurry. The ceramic coating slurry was gravure coated onto two opposing surfaces of the polyethylene base film to prepare a ceramic coating. The coating weight (based on the weight of Al2O3) was 2 g / m 2 After coating, the film is dried and cut to obtain the isolation film precursor.

[0155] 10g of polyvinylidene fluoride (PVDF, weight average molecular weight 500,000-800,000 g / mol) was weighed and dissolved in 90g of N-methyl-2-pyrrolidone to prepare an organic coating slurry. The organic coating slurry was sprayed on the two opposite surfaces of the isolation membrane precursor to prepare an organic coating. The coating weight (based on the weight of PVDF) was 0.5g / m 2 After spraying, the film is dried and cut to obtain a separator. In the separator coating, PVDF accounts for 20% of the coating mass and Al2O3 accounts for 80% of the coating mass.

[0156] 2) Electrolyte

[0157] In a glove box filled with argon (water content <10 ppm, oxygen content <1 ppm),

[0158] After mixing ethylene carbonate and ethyl methyl carbonate (3:7) in a weight ratio, slowly add LiPF6. Once the lithium salt is completely dissolved, an electrolyte solution with a LiPF6 concentration of 1 mol / L is obtained. The electrolyte conductivity is 9.1 mS / cm.

[0159] 3) Preparation of positive electrode sheet

[0160] The positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive agent Super P, and binder polyvinylidene fluoride were mixed in a mass ratio of 8:1:1. N-methylpyrrolidone was added as a solvent and mixed thoroughly to obtain a positive electrode slurry with a solid content of 50wt%. The positive electrode slurry was coated on the current collector aluminum foil, dried at 85°C, and then cold pressed. After trimming, cutting, and slitting, it was further dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet.

[0161] 4) Preparation of negative electrode sheet

[0162] Anode active material graphite, conductive agent Super P, thickener CMC-Na, and binder styrene-butadiene rubber (SBR) were mixed in a mass ratio of 80:15:3:2 and dissolved in deionized water to create anode slurry. A vacuum mixer was used to obtain the resulting anode slurry, with a solids content of 30 wt%. The anode slurry was then coated onto a current collector copper foil and dried at 85°C. The resulting anode sheet was then cold-pressed, trimmed, cut, and slit, and then dried at 120°C under vacuum for 12 hours.

[0163] 5) Battery Preparation

[0164] The prepared positive electrode sheet, isolation film, and negative electrode sheet are stacked in order, so that the isolation film is placed between the positive and negative electrode sheets to isolate the positive and negative electrodes, and the bare battery cell is wound, the tabs are welded, and the bare battery cell is placed in an outer package. The above-prepared electrolyte is injected into the dried battery cell, and the battery cell is packaged, allowed to stand, formed, shaped, and capacity tested to obtain the lithium secondary battery in Example 1.

[0165] Examples 2 to 20

[0166] Examples 2 to 5 were prepared using polyethylene with a Gurley value of 100s as the base film (Hengchuan, 09LD), polyethylene with a Gurley value of 110s as the base film (Hebei Jinli New Energy Technology Co., Ltd., SU08), polyethylene with a Gurley value of 200s as the base film (Hebei Jinli New Energy Technology Co., Ltd., 10LD), and polyethylene with a Gurley value of 300s as the base film (Taizhou Hengchuan New Energy Materials Technology Co., Ltd., LP0700), respectively. The remaining steps were similar to those in Example 1.

[0167] The preparation parameters of Examples 6 to 9 are similar to those of Example 1, but the coating weight of the coating is adjusted as follows:

[0168] In Example 6, the coating weight of the ceramic coating (calculated as Al2O3 weight) was adjusted to 2.4 g / m 2 The coating weight of the organic coating (based on PVDF weight) is 0.6 g / m 2 ; In the isolation membrane coating, PVDF accounts for 40% of the coating mass and Al2O3 accounts for 60% of the coating mass.

[0169] In Example 7, the coating weight of the ceramic coating (calculated as Al2O3 weight) was adjusted to 2.2 g / m 2 The coating weight of the organic coating (based on PVDF weight) is 0.5g / m 2 ; In the isolation membrane coating, PVDF accounts for 18.5% of the coating mass and Al2O3 accounts for 81.5% of the coating mass.

[0170] In Example 8, the coating weight of the ceramic coating (calculated as Al2O3 weight) was adjusted to 1 g / m 2 The coating weight of the organic coating (based on PVDF weight) is 0.4 g / m 2 ; In the isolation membrane coating, PVDF accounts for 28.6% of the coating mass and Al2O3 accounts for 71.4% of the coating mass.

[0171] In Example 9, the coating weight of the ceramic coating (calculated as Al2O3 weight) was adjusted to 0.5 g / m 2 The coating weight of the organic coating (based on PVDF weight) is 0.4 g / m 2 ; In the isolation membrane coating, PVDF accounts for 44.4% of the coating mass and Al2O3 accounts for 55.6% of the coating mass.

[0172] In Examples 10-13, the conductivity of the electrolyte was adjusted by adjusting the ratio of ethylene carbonate to carboxylic acid ester. The weight ratios of ethylene carbonate to ethyl formate were (25:75), (30:70), (40:60), and (45:55), respectively. The remaining preparation steps were similar to those in Example 1.

[0173] Example 14 uses polyethylene with a Gurley value of 100s as the base film (Hengchuan, 09LD), the volume ratio of ethylene carbonate and ethyl formate in the electrolyte is (43:57), and the remaining steps are similar to Example 9.

[0174] Example 15 uses polyethylene with a Gurley value of 210s as the base film (Hengchuan LP0821), the volume ratio of ethylene carbonate and ethyl formate in the electrolyte is (40:60), and the remaining steps are similar to Example 6.

[0175] The preparation method of Example 16 is similar to that of Example 10, but polyethylene with a Gurley value of 100s is used as the base film (Hengchuan 09LD).

[0176] The preparation method of Example 17 is similar to that of Example 13, but polyethylene with a Gurley value of 300s is used as the base film (Taizhou Hengchuan New Energy Material Technology Co., Ltd., LP0700).

[0177] Example 18 uses polypropylene with a Gurley value of 160s as the base film (Jinli SU07), and Example 19 uses glass fiber with a Gurley value of 160s as the base film (Jinli PU08). The remaining steps are similar to Example 1.

[0178] The battery preparation method of Example 20 is similar to that of Example 1, except that:

[0179] 2) Electrolyte

[0180] The electrolyte salt is NaPF6.

[0181] 3) Preparation of positive electrode sheet

[0182] The positive electrode active material is Na 0.67 Ni 0.33 Mn 0.67 O2.

[0183] 4) Preparation of negative electrode sheet

[0184] The negative electrode active material, hard carbon, was mixed with a conductive agent, Super P, a thickener, CMC, and a binder, styrene-butadiene rubber (SBR), in a mass ratio of 80:15:3:2, and dissolved in deionized water. The resulting negative electrode slurry was prepared using a vacuum mixer, with a solids content of 30 wt%. The negative electrode slurry was coated onto a current collector copper foil and dried at 85°C. The negative electrode sheet was then cold-pressed, trimmed, cut, and slit, and then dried at 120°C under vacuum for 12 hours.

[0185] Comparative Examples 1 to 4

[0186] Comparative Example 1: A secondary battery was prepared using polyethylene with a Gurley value of 280s as a base film (Hengchuan SA31). The ratio of ethylene carbonate to ethyl formate in the electrolyte was (43:57). The remaining steps were similar to those in Example 6.

[0187] Comparative Example 2: A secondary battery was prepared using polyethylene with a Gurley value of 100s as the base film (Hengchuan 09LD). The ratio of ethylene carbonate to ethyl formate in the electrolyte was (25:75). The remaining steps were similar to those in Example 14.

[0188] Comparative Examples 3 to 4 are similar to the preparation methods of Comparative Examples 1 to 2, but the positive electrode active material is adjusted to Na 0.67 Ni 0.33 Mn 0.67 O2.

[0189] The specific preparation parameters of Examples 1 to 20 and Comparative Examples 1 to 4 are shown in Table 1 below:

[0190] Table 1

[0191] 2. Performance Testing

[0192] 1. Isolation film

[0193] 1) Test of Gurley value of basement membrane

[0194] The test was conducted using a Gurley 4320N air permeability tester with reference to the GB / T 458-2008 standard. The base film was cut into 6.45 cm2 sheets at intervals of 150 mm in the longitudinal direction (maximum dimension). 2 Place the test sample in a permeameter and measure the time it takes for 100 mL of air to pass through the base film at a pressure of 1.21 kPa. This is the Gurley value. The average of the test results of three parallel samples is used as the Gurley value of the isolation membrane.

[0195] 2) Coating thickness test

[0196] Using a MAHR C1200 film thickness gauge (Germany), the base film thickness (H1) was measured first, followed by the isolation film thickness (H2). The coating thickness (H) = H2 - H1. The average of the coating thickness test results at 10 random locations on the isolation film sample was used as the coating thickness.

[0197] 3) Test of the porosity of the isolation membrane

[0198] The test was conducted with reference to the standard GB / T 24586-2009.

[0199] The isolation film is balled up and inserted into a sample cup. The sample cup containing the sample is then placed in a true density tester (AccuPyc II 1340). The test system is sealed, and helium is introduced according to the program. By measuring the pressure of the gas in the sample chamber and expansion chamber, the true volume of the sample is calculated according to Bohr's law (PV = nRT). P represents pressure, V represents true volume, n represents the amount of substance, T represents absolute temperature, and R represents the gas constant.

[0200] Porosity P = (V2 - V1) / V2 × 100%, where

[0201] V1 represents the actual volume of the sample obtained from the above test (cm 3 );

[0202] V2 represents the apparent volume of the sample (cm 3 ), V2=S×H×A, where:

[0203] S represents the area of ​​the isolation membrane (cm 2 );

[0204] H represents the thickness of the isolation membrane (cm);

[0205] A represents the number of samples.

[0206] 2. Electrolyte

[0207] 1) Test of electrolyte conductivity

[0208] Keep the test sample and standard liquid at a constant temperature of 25℃ (±0.1℃). Use two standard liquids to calibrate the test instrument (Leci DDSJ-308F) at an ambient temperature of 25℃ (±0.5℃). After calibration is completed and the electrodes are cleaned, place the test sample electrode vertically into the test liquid and start testing. Wait for the data to stabilize for more than 10 seconds and record the test results.

[0209] 3. Battery

[0210] 1) Battery cycle performance test

[0211] The cycling performance test process is as follows: At 25°C, the prepared battery was charged to 4.25V at a constant current of 1C. Then, it was charged at a constant voltage of 4.25V until the current dropped to 0.05C. After standing for 5 minutes, it was discharged to 2.8V at a constant current of 1C. This was the first charge / discharge cycle of the battery. The discharge capacity at this time was recorded as the discharge capacity of the battery in the first cycle (C0). The above charge and discharge process was repeated for 300 cycles. The discharge capacity at the 300th cycle was recorded as C1. The cycle capacity retention rate of the battery = C0 / C1 × 100%. The testing process for the comparative example and other examples was the same as above.

[0212] 2) Battery fast charging performance test

[0213] The fast-charge performance test process is as follows: At 25°C, the prepared battery was charged to 4.25V at 1C, then charged at a constant voltage of 4.25V until the current dropped to 0.05C. After that, it was allowed to rest for 5 minutes, and then discharged at a constant current of 1C to 2.8V. The discharge capacity D0 was recorded. The prepared battery was then charged to 4.25V at 3C, then charged at a constant voltage of 4.25V until the current dropped to 0.05C. After that, it was allowed to rest for 5 minutes, and then discharged at a constant current of 1C to 2.8V. The discharge capacity D1 was recorded. The battery fast-charge capacity retention rate = D1 / D0.

[0214] 3) Battery safety performance test

[0215] The safety performance test process is as follows: at 25°C, the prepared battery is charged to 4.25V at 1C, and then charged at a constant voltage of 4.25V until the current drops to 0.05C. The battery is then placed in a heating furnace, and the furnace is heated at 5°C / min to 100°C and maintained for 30 minutes. Thereafter, it is heated at 10°C for 30 minutes each until the battery cell thermal runaway occurs, and the temperature T at the time of thermal runaway of the battery cell is recorded.

[0216] 3. Analysis of test results of various embodiments and comparative examples

[0217] Batteries of various examples and comparative examples were prepared according to the above methods, and various performance parameters were measured. The results are shown in Table 2 below.

[0218] Table 2

[0219] As can be seen from Examples 1 to 20 and Comparative Examples 1 to 4, the secondary battery satisfies 0.5 ≤ G × H / (10 × σ) ≤ 13, which is beneficial for improving the fast charging performance, cycle performance, and thermal runaway temperature of the secondary battery. The secondary battery prepared by the method can be applied to lithium-ion batteries and sodium-ion batteries.

[0220] It can be seen from Examples 1 to 5 that by controlling the Gurley value G of the base film to meet 100s to 300s, the secondary battery has excellent fast charging performance, cycle performance and thermal runaway temperature.

[0221] It can be seen from Examples 6 to 9 that when the thickness H of the coating is controlled to meet the range of 0.5 μm to 5.1 μm, the secondary battery has excellent fast charging performance and cycle performance as well as a good thermal runaway temperature.

[0222] It can be seen from Examples 10 to 13 that the conductivity σ of the electrolyte at 25° C. satisfies: 7 mS / cm≤σ≤15 mS / cm, and the secondary battery has excellent fast charging performance and cycle performance as well as a good thermal runaway temperature.

[0223] It can be seen from Examples 14 to 17 that when the ratio of G / σ is in the range of 6.9 to 41.7, the secondary battery has excellent fast charging performance and cycle performance and a good thermal runaway temperature.

[0224] It can be seen from Examples 1 and 18 to 19 that the secondary battery prepared in the present application using polyethylene, polypropylene or glass fiber as the base film has excellent fast charging performance and cycle performance as well as thermal runaway temperature.

[0225] It can be seen from Examples 1 and 20 that for lithium secondary batteries or sodium secondary batteries, controlling the Gurley value G of the base film, the thickness H of the coating and the conductivity σ of the electrolyte at 25°C to satisfy 0.5≤G×H / (10×σ)≤13 can enable the secondary battery to have excellent fast charging performance and cycle performance as well as thermal runaway temperature.

[0226] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery, wherein: The invention comprises an electrolyte and a separator, wherein the separator comprises a base film and a coating layer coated on at least one side of the base film; The secondary battery satisfies: 0.5≤G×H / (10×σ)≤13, wherein G is the Gurley value of the base film, in s; H is the thickness of the coating, in μm; and σ is the conductivity of the electrolyte at 25°C, in mS / cm.

2. The secondary battery according to claim 1, wherein The secondary battery satisfies: 0.9≤G×H / (10×σ)≤10.

3. The secondary battery according to claim 1, wherein The secondary battery further satisfies: 6≤G / σ≤43.

4. The secondary battery according to claim 1, wherein The Gurley value G of the base film satisfies: 100s≤G≤300s.

5. The secondary battery according to claim 1, wherein The thickness H of the coating satisfies: 0.5 μm≤H≤5.1 μm.

6. The secondary battery according to claim 1, wherein The conductivity σ of the electrolyte at 25° C. satisfies: 7 mS / cm≤σ≤15 mS / cm.

7. The secondary battery according to any one of claims 1 to 6, wherein The porosity of the isolation film is 30% to 50%.

8. The secondary battery according to any one of claims 1 to 6, wherein The coating includes at least one of an organic coating and a ceramic coating.

9. The secondary battery according to any one of claims 1 to 6, wherein The base film includes one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, glass fiber, and non-woven fabric.

10. The secondary battery according to claim 8, wherein The coating includes an organic coating and a ceramic coating; The ceramic coating comprises one or more of Al2O3, AlO(OH), SiO2, TiO2, MgO, CaO, ZnO2, ZrO2 and SnO2; The organic coating comprises polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyamide, polyacrylonitrile, polyacrylate, polyacrylate and sodium hydroxymethyl cellulose. One or more.

11. The secondary battery according to claim 10, wherein The coating comprises polyvinylidene fluoride accounting for 15% to 100% of the total mass of the coating or Al2O3 accounting for 55% to 100% of the total mass of the coating.

12. The secondary battery according to any one of claims 1 to 6, wherein The electrolyte includes a solvent, and the solvent includes one or more of a carbonate solvent, an ether solvent, and a linear carboxylate solvent; wherein, The carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, propylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, and diethyl carbonate; The ether solvent includes one or more of dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, 1,2-diethoxyethane, and 1,2-dibutoxyethane; The linear carboxylic acid ester solvent includes one or more of methyl formate, ethyl formate, methyl propionate, ethyl propionate, propyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, and propyl acetate.

13. The secondary battery according to any one of claims 1 to 6, wherein The secondary battery includes at least one of a sodium secondary battery and a lithium secondary battery.

14. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 13.

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