Secondary battery and electric device

Abstract

The application provides a secondary battery and a power utilization device, and particularly relates to the technical field of batteries. 0.5 Mn 1.5 O4 or xLi2MnO3·(1-x)LiMO2, wherein 0 The electrolyte comprises a non-aqueous solvent, a lithium salt and an additive, the additive comprises a compound shown in the following formula, and the mass percentage of the compound is 0.1% to 3% based on the total mass of the electrolyte; in the formula, R1 and R2 are each independently selected from substituents with 0 to 3 carbon atoms, 0 to 4 unsaturations and 0 to 3 heteroatoms, the heteroatoms comprising nitrogen atoms and / or sulfur atoms. The application introduces an additive matched with high-voltage positive electrode materials LRM and LNMO in the electrolyte, so that the overcharge safety of the battery can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a secondary battery and a power utilization device. BACKGROUND

[0002] The bipolar battery refers to a plurality of batteries sharing the same current collector and being packaged together when stacked, and the internal connection of the battery is in the form of internal series, which can greatly increase the output voltage and output power of the battery, and reduce a large number of connecting wires, tabs and the like, thereby greatly improving the energy density of the battery. Therefore, the bipolar battery has a broad application prospect in the fields of electric vehicles and energy storage.

[0003] The liquid bipolar battery also has serious safety problems in use. Like the conventional lithium ion battery, the bipolar battery can cause thermal runaway under extreme conditions such as short circuit, puncture, impact, overheat and overcharge, and the thermal runaway caused by overcharge is particularly serious. Under the condition of overcharge, the structure of the positive active material is more unstable, lithium is more easily deposited on the surface of the negative electrode, and the side reaction between the electrode material and the electrolyte is also more intense, thereby causing serious capacity attenuation of the battery, affecting the cycle performance of the battery, and even causing fire, explosion and other safety accidents.

[0004] In order to prevent the safety problems caused by overcharge of the battery, the conventional method is to modify the battery material or use a circuit protection device, an explosion-proof safety device and a voltage-sensitive film in the battery, which cannot fundamentally solve the overcharge safety problem of the battery. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a secondary battery and a power utilization device, which improves the overcharge safety problem of the bipolar battery by adding a redox shuttle inhibitor matched with the high-voltage positive material LRM and LNMO in the electrolyte.

[0006] To achieve the above object and other related objects, the first aspect of the present application provides a secondary battery, which comprises a bipolar electrode sheet, a separator and an electrolyte in which the bipolar electrode sheet and the separator are soaked, the bipolar electrode sheet comprises a positive active material layer, the positive active material layer comprises LiNi 0.5 Mn 1.5 O4 or xLi2MnO3·(1-x)LiMO2, wherein 0

[0007]

[0008] R1 and R2 in the formula I are each independently selected from a substituent having 0-3 carbon atoms, 0-4 unsaturations, and 0-3 heteroatoms, which include nitrogen and / or sulfur atoms.

[0009] In an embodiment of the present application, the mass percentage of the compound represented by the formula I is 0.1%-1% based on the total mass of the electrolyte.

[0010] In an embodiment of the present application, R1 and R2 in the formula I are each independently selected from any one of an alkyl group, an alkenyl group, and an amino group.

[0011] In an embodiment of the present application, the bipolar electrode sheet further comprises a bipolar current collector and a negative active material layer, and the positive active material layer and the negative active material layer are respectively arranged on two side surfaces of the bipolar current collector.

[0012] In an embodiment of the present application, the electrolyte between adjacent bipolar current collectors is sealed by a packaging adhesive.

[0013] In an embodiment of the present application, the packaging adhesive comprises an epoxy adhesive and an epoxy curing adhesive, and the epoxy adhesive comprises a bisphenol A type epoxy adhesive.

[0014] In an embodiment of the present application, the secondary battery further comprises a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet and the negative electrode sheet are respectively arranged on two sides of the stack of bipolar electrode sheets, and the separator is arranged between adjacent bipolar electrode sheets, between the bipolar electrode sheet and the positive electrode sheet, and between the bipolar electrode sheet and the negative electrode sheet.

[0015] In an embodiment of the present application, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethyl)sulfonylimide, lithium acetate, lithium methylsulfonate, and lithium trifluoromethylsulfonate, and the mass percentage of the lithium salt is 12%-16% based on the total mass of the electrolyte.

[0016] In an embodiment of the present application, the non-aqueous solvent comprises one or more of a carbonate, a carboxylate, an ether, and a nitrile, the carbonate comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, fluoroethylene carbonate, and fluoroethyl methyl carbonate, the carboxylate comprises one or more of ethyl formate, ethyl acetate, propyl acetate, and ethyl propionate, the ether comprises dimethyl ether of ethylene glycol and / or diethyl ether of diethylene glycol, and the nitrile comprises one or more of acetonitrile, propionitrile, butyronitrile, and valeronitrile.

[0017] The present application also provides an electric device comprising the secondary battery as described above.

[0018] The secondary battery of the present application adds a redox shuttle inhibitor compatible with high-voltage positive electrode material LRM and LNMO in the electrolyte. When the battery is overcharged, the additive will be oxidized near the positive electrode to form active radicals, then diffuse to the negative electrode to be reduced to form neutral molecules, and then diffuse to the positive electrode, and so on until the overload current in the battery is consumed, avoiding the continuous rise of the positive electrode voltage and the continuous violent reaction with the electrolyte during overcharging, thereby improving the safety of the battery overcharging.

[0019] In addition, the secondary battery of the present application is a bipolar battery. When packaged, a mixture of epoxy resin glue and epoxy resin fixing glue is used as the packaging glue, which can realize rapid curing at high temperature and curing time less than 30 min at room temperature, thereby realizing the packaging of the bipolar battery and greatly simplifying the packaging steps and reducing the packaging time. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other embodiments can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0021] Figure 1 Structure schematic diagram of the secondary battery of the present application in an embodiment;

[0022] Figure 2 Structure schematic diagram of the assembly step S1 of the secondary battery of the present application in an embodiment;

[0023] Figure 3 Structure schematic diagram of the assembly step S2 of the secondary battery of the present application in an embodiment;

[0024] Figure 4 Structure schematic diagram of the assembly step S3 of the secondary battery of the present application in an embodiment;

[0025] Figure 5 Structure schematic diagram of the assembly step S5 of the secondary battery of the present application in an embodiment.

[0026] Element number explanation:

[0027] 100, negative electrode sheet; 200, bipolar electrode sheet; 300, positive electrode sheet; 10, bipolar current collector; 20, negative electrode active material layer; 30a, first packaging glue; 30b, second packaging glue; 40, separator; 50, positive electrode active material layer. DETAILED DESCRIPTION

[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] In this document, when referring to numerical ranges, unless otherwise specified, the distribution of selectable values ​​within a numerical range is considered continuous, including the two endpoints of the range (i.e., the minimum and maximum values), and every value between these two endpoints. When multiple numerical ranges are provided to describe a feature or property, these numerical ranges can be combined.

[0031] Unless otherwise specified, "%" in this article refers to the percentage content by mass.

[0032] In this article, substituents refer to atoms or groups of atoms that replace those on the main chain or rings of organic compounds. They can replace a hydrogen atom or other atoms in a molecule, affecting its chemical and physical properties. The type and position of substituents have a significant impact on the reactivity, polarity, solubility, and other properties of a molecule.

[0033] Unsaturation, also known as the hydrogen deficiency index or cycloaddition double bond index, is a quantitative indicator of the degree of unsaturation in organic compound molecules. Its molecular formula is C2. n H m The hydrocarbon and its molecular formula is C n H m O x For hydrocarbon derivatives, if m < 2n + 2, then the hydrocarbon and its hydrocarbon group have a certain degree of unsaturation Ω. That is, compared with open-chain alkanes with the same number of carbon atoms, the degree of unsaturation of the organic compound increases by 1 for every 2 hydrogen atoms removed.

[0034] Number of heteroatoms: In organic chemistry, non-carbon atoms are collectively referred to as heteroatoms. The most common heteroatoms are nitrogen, sulfur and oxygen atoms.

[0035] Lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 Lithium-ion battery cathode materials such as LNMO (Li₄O₄) and LRM (xLi₂MnO₃·(1-x)LiMO₂, 0 < x < 1, M includes one or more of Ni, Co, and Mn) possess high energy density, excellent cycle life, and high discharge plateau voltage, making them a hot research topic in lithium-ion battery cathode materials. However, as energy storage battery capacity increases, the safety performance of LNMO and LRM system batteries (including short circuits, overcharging, and thermal runaway) also faces certain risks, with overcharging causing particularly serious safety issues. Overcharging refers to the storage of charge within the battery exceeding its design capacity, resulting in excessively high battery voltage. When a lithium-ion battery is overcharged, the battery voltage rises rapidly with increasing polarization, inevitably causing irreversible changes in the structure of the positive electrode active material and oxidative decomposition of the electrolyte. This generates a large amount of gas and releases a significant amount of heat, causing a sharp increase in internal pressure and temperature, posing safety hazards such as explosion and combustion. Simultaneously, the surface of the negative electrode in an overcharged state will also experience reduced safety due to the deposition of metallic lithium.

[0036] This application proposes an electrolyte to address the overcharge safety issue of LNMO and LRM system secondary batteries. By introducing a redox shuttle inhibitor that matches the LNMO and LRM cathode materials into the electrolyte, the redox reaction during battery overcharging is prevented from causing a continuous rise in cathode voltage and a continuous and violent reaction with the electrolyte, thereby improving the battery overcharge problem.

[0037] Please see Figure 1 This invention provides a secondary battery comprising a bipolar electrode 200, a separator 40, and an electrolyte therein to wet the bipolar electrode 200 and the separator 40. The bipolar electrode 200 includes a positive active material layer 50, which comprises a positive active material LiNi. 0.5 Mn 1.5 O4 or xLi2MnO3·(1-x)LiMO2, where 0 < x < 1, and M includes one or more of Ni, Co, and Mn. The electrolyte comprises a non-aqueous solvent, a lithium salt, and additives, wherein the additives include compounds represented by Formula I:

[0038]

[0039] In Formula I, R1 and R2 are each independently selected from substituents with 0-3 carbon atoms, 0-4 degrees of unsaturation, and 0-3 heteroatoms, including nitrogen and / or sulfur atoms. That is, the types of R1 and R2 in Formula I do not affect each other; they can be the same substituent or different substituents. The number of carbon atoms in the substituents can be any value from 0 to 3, such as 0, 1, 2, or 3, and the degree of unsaturation can be any value from 0 to 4, such as 0, 1, 3, or 4. Heteroatoms are non-carbon atoms, selected from nitrogen (N) atoms and / or sulfur (S) atoms, but not limited to these. The number of heteroatoms can be any value from 0 to 3, such as 0, 1, 2, or 3. When the number of heteroatoms is 1, the heteroatom can be either a nitrogen atom or a sulfur atom. When the number of heteroatoms is 2 or 3, the heteroatoms can all be nitrogen atoms, all be sulfur atoms, or simultaneously contain both nitrogen and sulfur atoms.

[0040] In one embodiment, R1 and R2 in Formula I are each independently selected from any one of alkyl, alkenyl, and amino groups. That is, R1 and R2 can both be selected from any one of alkyl, alkenyl, and amino groups, and can be the same or different. As an example, R1 and R2 can both be alkyl groups; or R1 can be alkyl groups and R2 can be alkenyl or amino groups, etc.

[0041] The compound shown in Formula I contains a naphthoquinone structure and an electron-withdrawing functional group, a cyano (-CN). One edge ring of the naphthoquinone structure is para-substituted with two sulfur atoms. The cyano group, as a strong electron-withdrawing group, increases the oxidation potential by reducing the electron density of the molecule. The para-substitution of the edge ring with two sulfur atoms further improves its voltage withstand capability, allowing it to be oxidized above 4.85V, for example, 4.9V, while remaining unoxidized below 4.85V. This is similar to the high-voltage cathode material LiNi. 0.5 Mn 1.5 O4 or xLi2MnO3·(1-x)LiMO2 are compatible. Therefore, under the normal operating voltage of LRM and LNMO battery systems, the compound shown in Formula I does not undergo electrochemical reactions. When the battery is overcharged, the compound shown in Formula I is oxidized near the positive electrode to form active free radicals, which then diffuse to the negative electrode, gain electrons, are reduced, form neutral molecules, and then diffuse back to the positive electrode. This cycle continues until the overload current in the battery is completely consumed, thus achieving the purpose of preventing overcharge. The additive shown in Formula I converts the excess electricity provided by overcharging into heat through reversible reactions on both sides of the electrode, avoiding side reactions between the electrode and the electrolyte, protecting the battery components from damage under high voltage, and thus improving the cycle performance of the battery.

[0042] The addition amount of the compound of Formula I has a great influence on the performance of the battery. When the addition amount of the compound of Formula I in the electrolyte is insufficient, the overcharge prevention effect of the battery is not obvious, and when the addition amount is too much, a relatively thick solid electrolyte interface film will be formed on the electrode surface, thereby increasing the internal resistance of the battery and affecting the cycle performance of the battery. In the present application, the content of the compound of Formula I in the electrolyte is 0.1% to 3%, further 0.1% to 1%, based on the total mass of the electrolyte, and can be specifically listed as 0.1%, 0.5%, 0.8 or 1%, etc.

[0043] The lithium salt in the electrolyte can be selected from any lithium salt suitable for use in lithium ion batteries in the art. In order to obtain a better electrolyte, the lithium salt should have the following characteristics: low dissociation energy and high solubility, low dissociation energy ensures that the electrolyte formed after the lithium salt is dissolved has high conductivity, thereby realizing high rate of the battery; high solubility ensures that there are enough lithium ions in the electrolyte for transmission; good stability, when the battery works at high voltage and high temperature, the lithium salt will not react with other components; good SEI film forming performance to ensure that the electrolyte is not continuously consumed in the subsequent cycle process.

[0044] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis(trifluoromethyl)sulfonylimide (LiTFSI), lithium acetate (CH3COOLi), lithium methylsulfate (CH3SO3Li), lithium trifluoromethylsulfate (CF3SO3Li). That is, the lithium salt can use a single lithium salt or a mixed lithium salt. The total mass percentage of the lithium salt in the electrolyte is 12% to 16%, based on the total mass of the electrolyte, and can be specifically listed as 12%, 14% or 16%, etc. Further, the lithium salt uses a mixed lithium salt mainly with lithium hexafluorophosphate (LiPF6) and supplemented with other lithium salts, which can improve the overall performance of the electrolyte. For example, a mixed lithium salt of lithium hexafluorophosphate and lithium bisfluorosulfonylimide is used, and the mass ratio of lithium hexafluorophosphate to lithium bisfluorosulfonylimide can be 14:1, 14:2 or 13:2, etc.

[0045] The non-aqueous solvent is used as a main part of the electrolyte for dispersing lithium salt and additives. In some embodiments, the non-aqueous solvent includes one or more of carbonates, carboxylic esters, ether solvents and nitrile solvents. Among them, the carbonates include one or more of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC) and fluoroethyl methyl carbonate (FEMC); the carboxylic esters include one or more of ethyl formate, ethyl acetate, propyl acetate and ethyl propionate; the ethers include one or both of ethylene glycol dimethyl ether and diethylene glycol diethyl ether; the nitrile solvents include one or more of acetonitrile, propionitrile, butyronitrile and valeronitrile. That is, the non-aqueous solvent can be selected from any one of the above-mentioned listed solvents, or a combination of any two or more thereof. For example, the non-aqueous solvent is a combination of ethylene carbonate, dimethyl carbonate and methyl formate, or a combination of ethyl formate and ethylene carbonate, and the like. A person skilled in the art can select a suitable solvent combination according to actual needs.

[0046] The mass percentage of the non-aqueous solvent in the electrolyte is 80% to 90%, for example, 80%, 85% or 90%, based on the total mass of the electrolyte.

[0047] In other embodiments, other types of additives can also be added to the electrolyte, such as vinylene carbonate (VC), vinyl sulfate (DTD), fluoroethylene carbonate (FEC), propylene-1,3-sulfonic acid lactone (PST), tetra-vinyl silane (TVSI) and the like. A person skilled in the art can select according to actual production needs.

[0048] The configuration method of the electrolyte of the present application is exemplified as follows: in an argon atmosphere glove box with a water content <10 ppm, the non-aqueous solvent is mixed uniformly according to the set proportion, and then the fully dried lithium salt and additives are added to the above-mentioned organic solvent and mixed uniformly to prepare the electrolyte.

[0049] Please refer to Figure 1 In an embodiment, the secondary battery includes at least one bipolar electrode sheet 200, and the at least one bipolar electrode sheet 200 and the separator 40 are alternately arranged to form a stacked electrode body. Specifically, the bipolar electrode sheet 200 includes a bipolar current collector 10, a negative electrode active material layer 20 and a positive electrode active material layer 50. Among them, the bipolar current collector 10 adopts a conventional current collector type in the art, for example, a copper-aluminum integrated current collector, which has a copper foil surface and an aluminum foil surface, the copper foil surface is used to form the negative electrode active material layer 20 thereon, and the aluminum foil surface is used to form the positive electrode active material layer 50 thereon.

[0050] The positive active material layer 50 is disposed on the aluminum foil side of the bipolar current collector 10. The positive active material layer 50 includes a positive active material, a positive conductive agent, and a positive binder. The positive active material can be LiNi 0.5 Mn 1.5 O4(LNMO), which has a spinel structure, and the diffusion path of lithium ions in the spinel crystal structure is three-dimensional, thus having excellent rate performance. In addition, LNMO has good cycle performance and high energy density and high operating voltage (about 4.7 V). The positive active material can also be xLi2MnO3·(1-x)LiMO2(LRM), where 0 < x < 1, for example, x is 0.1, 0.3, 0.5, or 0.8, and M includes one or more of Ni, Co, and Mn, for example, M is Ni, Mn, or a combination of Co and Mn. LRM has high specific capacity, excellent cycle performance, and high operating voltage (about 4.6 V). The positive conductive agent can be selected from one or a combination of two or more of carbon black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, or a mixture thereof in any proportion, for example, carbon black, or a combination of carbon black and graphene, or a combination of acetylene black, graphene, and carbon nanofibers, etc. The positive binder is, for example, selected from any one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyvinyl ether, polymethyl methacrylate (PMMA), ethylene-propylene-diene terpolymer (EPDM), polyhexafluoropropylene, or polymerized styrene butadiene rubber (SBR), etc., for example, polyvinylidene fluoride, or a combination of polyamide and polyacrylonitrile, etc. The proportions of the various substances in the positive active material layer 50 can be set according to actual production needs.

[0051] The negative active material layer 20 is disposed on the copper foil side of the bipolar current collector 10. The negative active material layer 20 includes a negative active material, a negative conductive agent, a negative binder, and a thickening agent. The negative active material includes, but is not limited to, a graphite-based negative material and / or a silicon-based negative material. The graphite-based negative material includes one or more of artificial graphite, natural graphite, soft carbon, and hard carbon. The silicon-based negative material includes silicon monomer, silicon oxide compounds (SiO xThe negative electrode conductive agent is selected from one or a combination of two or more of carbon black, acetylene black, graphene, carbon nanotube, carbon nanofiber, etc. in any proportion. The negative electrode conductive agent can be the same as or different from the positive electrode conductive agent. The negative electrode binder is selected from one or a combination of two or more of polyacrylic acid (PAA), lithium polyacrylate (PAALi), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), styrene butadiene rubber (SBR), etc. in any proportion, such as styrene butadiene rubber, a combination of styrene butadiene rubber and polyacrylic acid, etc. The thickening agent is selected from carboxymethyl cellulose (CMC), such as sodium carboxymethyl cellulose (CMC-Na) or lithium carboxymethyl cellulose (CMC-Li). The proportions of the respective substances in the negative electrode active material layer 20 can be set according to actual production requirements.

[0052] The separator 40 between adjacent bipolar electrodes 200 is made of a porous material that is insulating and allows lithium ions to pass through, such as a polyethylene film (PE), a polypropylene film (PP), a glass fiber film, a polyethylene film, or a composite film, etc.

[0053] Please refer to Figure 1 In some embodiments, the secondary battery further includes a negative electrode tab 100 and a positive electrode tab 300, which are arranged on the two sides of the laminated electrode body along the stacking direction of the bipolar electrodes 200, and the negative electrode tab 100 is arranged on the side of the laminated electrode body that exposes the negative electrode active material layer 20, and the positive electrode tab 300 is arranged on the side of the laminated electrode body that exposes the positive electrode active material layer 50. The negative electrode tab 100 and the bipolar electrode 200, and the positive electrode tab 300 and the bipolar electrode 200 are both insulated by the separator 40. The negative electrode tab 100 includes a negative electrode current collector and a negative electrode active material layer 20 arranged on one side of the negative electrode current collector. The negative electrode current collector can be a copper foil or the bipolar current collector 10 described above. In this embodiment, the bipolar current collector 10 is used, and the negative electrode active material layer 20 is arranged only on the copper foil surface of the bipolar current collector 10. The positive electrode tab 300 includes a positive electrode current collector and a positive electrode active material layer 50 arranged on one side of the positive electrode current collector. The positive electrode current collector can be an aluminum foil or the bipolar current collector 10 described above. In this embodiment, the bipolar current collector 10 is used, and the positive electrode active material layer 50 is arranged only on the aluminum foil surface of the bipolar current collector 10.

[0054] In order to avoid the liquid short circuit of the bipolar battery from causing the battery to fail, an insulating sealing piece needs to be arranged at the edge of the two adjacent bipolar current collectors 10 after the electrolyte is injected, so as to be packaged. However, the current packaging method is to use light curing or heat pressing curing to irradiate or heat each unit, and the preparation process is very complicated and time-consuming. Therefore, the present application provides a simple curing packaging glue which can be quickly cured at different speeds to form a sealing layer at different temperatures, thereby simplifying the packaging steps of the bipolar battery. The packaging glue comprises a first packaging glue 30a and a second packaging glue 30b, the first packaging glue 30a comprises an epoxy resin glue, and the second packaging glue 30b comprises an epoxy resin curing glue. The epoxy resin glue and the epoxy resin curing glue have common epoxy glue components, and after being mixed, they can be cured at different temperatures for different times, for example, 30s at 80 DEG C or 30min at room temperature.

[0055] In some embodiments, the epoxy resin glue can be a bisphenol A type epoxy resin glue, and the epoxy resin curing glue can be a fatty amine curing agent, including but not limited to ethylenediamine, hexanediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. The epoxy resin curing glue can be selected from one of them, or any two or more of them. The ratio of the epoxy resin glue to the epoxy resin curing glue is not limited, and they can be mixed at any ratio. For example, the mass ratio of the epoxy resin glue to the epoxy resin curing glue is 10:1. The packaging glue of the present embodiment can realize slightly high temperature super rapid curing and room temperature rapid curing, thereby realizing the packaging of the secondary battery and greatly simplifying the packaging steps and reducing the packaging time.

[0056] The above negative electrode sheet 100, bipolar electrode sheet 200 and positive electrode sheet 300 can be prepared according to conventional processes in the art, for example as follows:

[0057] Negative electrode sheet preparation: the above negative electrode active material, negative electrode conductive agent, negative electrode binder and thickening agent are dispersed in deionized water according to a set ratio to form a uniform 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 100 is obtained.

[0058] Positive electrode sheet preparation: the above positive electrode active material, positive electrode conductive agent and positive electrode binder are dispersed in a solvent (such as N-methyl pyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet 300 is obtained.

[0059] Bipolar electrode sheet preparation: the above negative electrode slurry is coated on the copper foil surface of the bipolar current collector, and after air drying at room temperature, it is transferred to an oven for drying; then the above prepared positive electrode slurry is coated on the aluminum foil surface of the bipolar current collector which has been coated with negative electrode active material on one side, and after air drying at room temperature, it is transferred to an oven for drying, and after cold pressing and other processes, the bipolar electrode sheet 200 is obtained.

[0060] After the above prepared negative electrode sheet 100, bipolar electrode sheet 200 and positive electrode sheet 300 are assembled into a bipolar battery, the assembly step is described in Figures 1 to 5 , the specific process is as follows:

[0061] S1, the separator 40 is assembled on the surface of the negative electrode sheet 100, wherein the bipolar current collector 10 of the negative electrode sheet 100 is coated with a negative active material layer 20 on one side, and the separator 40 is assembled on the side of the negative electrode sheet 100 coated with the negative active material layer 20 (see Figure 2 );

[0062] S2, the bipolar electrode sheet 200 is arranged on the separator 40 of step S1, and the side of the bipolar electrode sheet 200 provided with the positive active material layer 50 faces the separator 40 (see Figure 3 );

[0063] S3, then the separator 40 is arranged on the bipolar electrode sheet 200 (see Figure 4 );

[0064] S4, repeat steps S2 to S3 several times (determined according to actual production conditions), to achieve the required number of battery units;

[0065] S5, the positive electrode sheet 300 is assembled on the separator 40 of the previous step, wherein the bipolar current collector 10 of the positive electrode sheet 300 is coated with a positive active material layer 50 on one side, and the positive active material layer 50 faces the separator 40 (see Figure 5 )。

[0066] S6, the sealing glue composed of the mixture of the first sealing glue 30a (epoxy resin glue) and the second sealing glue 30b (epoxy resin curing glue) is coated on three of the four positions between the adjacent bipolar current collectors 10, and heated at 80℃ for 30s;

[0067] S7, after liquid injection, the sealing glue composed of the mixture of the epoxy resin glue and the epoxy resin curing glue is coated on the last position, and placed at room temperature for half an hour to complete the curing (see Figure 1 )。

[0068] S8, the assembled battery is subjected to processes such as standing, formation, aging, fixture, and capacity distribution, to obtain Figure 1 the bipolar battery shown in the figure.

[0069] The secondary battery of the present application adopts a bipolar stacking structure, a plurality of electrode sheets are arranged in a stacked manner to form a connection structure in which a plurality of battery cells are substantially connected in series, a plurality of bipolar current collectors 10 of the bipolar battery are arranged in a stacked manner, and a positive active material layer 50, a separator 40 and a negative active material layer 20 are arranged in sequence between adjacent bipolar current collectors 10 to form a battery cell with the bipolar current collectors 10 on both sides. The positive active material layer 50, the separator 40 and the negative active material layer 20 in each battery cell are stacked in a predetermined order. The plurality of battery cells formed in the secondary battery are connected in series and stacked to form a bipolar stacking structure, and are quickly sealed by encapsulation glue. Moreover, during encapsulation, after all the electrode sheet assemblies are assembled except for the part where the liquid is injected, three-face sealing is performed first, which is time-saving and more convenient; after the liquid is injected, the last face is encapsulated, the epoxy resin glue and the epoxy resin curing glue are mixed, and curing can be completed within half an hour by placing at room temperature, thereby realizing encapsulation of the battery.

[0070] The second aspect of the present application provides a power-using device, which comprises the secondary battery of the above-mentioned application. The secondary battery can provide power for the power-using device.

[0071] The power-using device includes but is not limited to mobile phones, tablets, notebook computers, electric toys, electric vehicles, new energy vehicles, ships, spacecraft, etc. Among them, the electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric plane toys, etc. Spacecraft can include airplanes, rockets, space shuttles and spacecraft, etc. New energy vehicles can be pure electric vehicles, hybrid electric vehicles or extended range vehicles, etc.

[0072] The technical solutions of the present application will be described in detail below through several specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art, and the instruments used in the examples are commercially available.

[0073] Example 1

[0074] Please refer to Figures 1 to 5The embodiment provides a secondary battery, which comprises a negative electrode sheet 100, a bipolar electrode sheet 200, a positive electrode sheet 300, a separator 40, an electrolyte and a packaging adhesive 30, the bipolar electrode sheet 200 comprises a bipolar current collector 10, a negative electrode active material layer 20 arranged on the copper foil surface of the bipolar current collector 10 and a positive electrode active material layer 50 arranged on the aluminum foil surface of the bipolar current collector 10; the negative electrode sheet 100 comprises the bipolar current collector 10 and the negative electrode active material layer 20 arranged on the copper foil surface of the bipolar current collector 10; the positive electrode sheet 300 comprises the bipolar current collector 10 and the positive electrode active material layer 50 arranged on the aluminum foil surface of the bipolar current collector 10. The negative electrode sheet 100, the separator 40, the bipolar electrode sheet 200, the separator 40, the bipolar electrode sheet 200, the separator 40 (repeated 9 times), the positive electrode sheet 300 are assembled into a laminated electrode body. The electrolyte comprises a non-aqueous solvent in which battery-grade fluorinated ethyl methyl carbonate (FEMC) and fluorinated ethylene carbonate (FEC) are mixed at a mass ratio of 7:3, a lithium salt LiPF6 and an additive The mass percentage of the additive is 1% and the mass percentage of the lithium salt is 13% based on the total mass of the electrolyte.

[0075] The specific preparation process is as follows:

[0076] (1) Preparation of the positive electrode sheet: a positive electrode active material LiNi 0.5 Mn 1.5 O4, a binder polyvinylidene fluoride and a conductive agent Super P are mixed at a weight ratio of 98:1:1, N-methyl pyrrolidone (NMP) is added, and uniform stirring is carried out under the action of a vacuum stirrer to obtain a positive electrode slurry; the positive electrode slurry is uniformly coated on the aluminum foil surface of the bipolar current collector, and after air drying at room temperature, the positive electrode sheet is transferred to an oven for drying.

[0077] (2) Preparation of the negative electrode sheet: a negative electrode active material artificial graphite, a conductive agent Super P, a thickening agent carboxymethyl cellulose sodium (CMC-Na) and a binder styrene butadiene rubber (SBR) are mixed at a mass ratio of 96:1:1:2, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum stirrer; the negative electrode slurry is uniformly coated on the copper foil surface of the bipolar current collector; after air drying at room temperature, the negative electrode sheet is transferred to an oven for drying.

[0078] (3) Preparation of the bipolar electrode sheet: the positive electrode slurry is uniformly coated on the aluminum foil surface of the bipolar current collector, and after air drying at room temperature, the positive electrode sheet is transferred to an oven for drying; then the negative electrode slurry is uniformly coated on the copper foil surface of the bipolar current collector, and after air drying at room temperature, the negative electrode sheet is transferred to an oven for drying, thereby obtaining the bipolar electrode sheet.

[0079] (4) Electrolyte preparation: In an argon atmosphere glove box with water content <10 ppm, battery grade fluoroethyl methyl carbonate (FEMC) and fluoroethylene carbonate (FEC) were mixed according to a mass ratio of 7:3 to form an organic solvent. Then, the additives and lithium salt LiPF6 were added according to Table 1. The content of each component in the electrolyte, except for the solvent, was the weight percentage calculated based on the total weight of the electrolyte, and the content of each component in the solvent was the percentage content of the total solvent.

[0080] (5) Separator: A polypropylene film was used as the separator.

[0081] (6) Battery assembly: The separator was first assembled on the negative active material layer 20 of the negative electrode sheet 100, then the bipolar electrode sheet 200 was arranged on the above-mentioned separator 40, and the positive active material layer 50 of the bipolar electrode sheet 200 faced the separator 40; then the separator 40 was arranged on the bipolar electrode sheet 200, the bipolar electrode sheet was arranged on the separator 40, and the process was repeated 9 times; then the positive electrode sheet 300 was arranged on the separator 40 of the previous step, and the positive active material layer 50 faced the separator 40, forming a stacked electrode body; the packaging glue 30a and 30b (a mixture of epoxy resin glue and epoxy resin curing glue according to a mixing ratio of 10:1) was coated on three sides of the surrounding position between adjacent bipolar current collectors 10 in the stacked electrode body, and cured at 80°C for 30s; then the electrolyte was injected from the side not coated with the packaging glue, and the packaging glue was coated, and cured at room temperature for half an hour; the assembled battery was subjected to the processes of standing, formation, aging, clamping, and capacity distribution, to obtain a secondary battery (bipolar battery).

[0082] Example 2

[0083] The difference between this embodiment and Example 1 is that the amount of additive added is 0.1%.

[0084] Example 3

[0085] The difference between this embodiment and Example 1 is that the amount of additive added is 0.5%.

[0086] Example 4

[0087] The difference between this embodiment and Example 1 is that the amount of additive added is 3%.

[0088] Example 5

[0089] The difference between this embodiment and Example 1 is that R1 and R2 of the additive are vinyl groups, and the additive has the following structure:

[0090]

[0091] Example 6

[0092] The difference between this example and Example 1 is that the R1 of the additive is methyl and the R2 is amino, and the additive has the following structure:

[0093]

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 1 is that the amount of additive added is 0.05%.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that the amount of additive added is 5%.

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 1 is that the bipolar battery is not sealed with encapsulation glue.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 1 is that the R1 and R2 of the additive are n-butyl, and the additive has the following structure:

[0102]

[0103] To verify the performance of the secondary battery of the present application, the applicant respectively tested the secondary batteries prepared in Examples 1-6 and Comparative Examples 1-4 for performance, and the test results are shown in Table 1, and the test methods are as follows:

[0104] (1) High-temperature cycle number test:

[0105] The secondary batteries in Examples 1-6 and Comparative Examples 1-4 were subjected to long-term cycle charging and discharging at 45°C, and the test was stopped when the battery capacity was cycled to 80% of the first cycle discharge capacity, and this number was the cycle number of the battery at 45°C (80% SOH state test ended), wherein the voltage interval was 3.4V-4.85V, and the charging and discharging rate was 0.5C / 1C.

[0106] (2) Battery direct current resistance (DCR) test

[0107] At 25°C, the secondary batteries in Examples 1-6 and Comparative Examples 1-4 were discharged at 1C current to 50% SOC (state of charge, reflecting the remaining capacity of the battery), the current was increased to 4C and maintained for 30s, the difference between the updated stable voltage and the original platform voltage was detected, and the ratio of the value to the 4C current value was the direct current resistance DCR of the corresponding secondary battery. The DCR test result of the corresponding secondary battery after the first full charge is the initial DCR of the battery.

[0108] Table 1: Secondary battery performance parameters of Examples 1-6 and Comparative Examples 1-4

[0109]

[0110]

[0111] As can be seen from Table 1, Comparative Examples 1-4 and Comparative Example 1-2, when the mass percentage of the additive is in the range of 0.1%-3% based on the total mass of the electrolyte, the high-temperature cycle performance of the battery is better than that when the additive amount is not in this range, because when the additive is in the above range, it can effectively play its redox shuttle inhibition ability, consume the overload current in the battery, avoid side reactions between the electrode and the electrolyte, protect the battery components from damage under high pressure, thereby improving the cycle performance and overcharge safety of the battery, and when the additive amount is 1%, it reaches the optimum. When the additive amount is less than 0.1% (such as 0.05% in Comparative Example 1), the redox shuttle ability is insufficient to effectively improve the cycle performance and overcharge safety of the battery; when the additive amount is higher than 3% (such as 5% in Comparative Example 2), a thicker solid electrolyte interface film will be formed on the surface of the electrode, increasing the direct current resistance of the battery, thereby increasing the irreversible loss and reducing the cycle performance.

[0112] As can be seen from Comparative Example 1 and Comparative Example 3, when no sealing glue is used for sealing, the secondary battery cannot be cycled because of the liquid connection short circuit in the secondary battery, which cannot be cycled.

[0113] As can be seen from Comparative Example 1, Examples 5-6 and Comparative Example 4, when the number of carbon atoms of the substituents R1and R2of the additive in the electrolyte exceeds 3, it will affect the overcharge safety performance of the battery to some extent, because when the number of carbon atoms of R1and R2is too large, it will affect the redox shuttle inhibition ability of the additive, which cannot completely consume the overload current in the battery, avoid side reactions between the electrode and the electrolyte, thereby affecting the cycle performance and overcharge safety performance of the battery.

[0114] The secondary battery of the present application adds an additive compatible with high-voltage positive electrode material LRM and LNMO in the electrolyte. When the battery is overcharged, the additive is oxidized near the positive electrode to form active radicals, then diffuses to the negative electrode to be reduced to form neutral molecules, and then diffuses to the positive electrode, and so on. The internal cyclic oxidation-reduction reaction avoids the continuous rise of the positive electrode voltage and the continuous violent reaction with the electrolyte during overcharging, thereby improving the safety of the battery overcharging. Moreover, the secondary battery adopts a bipolar battery structure design, introduces a packaging layer that solidifies at different speeds at different temperatures, simplifies the packaging steps, solves the problem of liquid connection short circuit in liquid batteries and the complicated sealing process, and improves the overall energy density of the battery. Therefore, the present application effectively overcomes some practical problems in the prior art and has high utilization value and use significance.

[0115] The above examples only illustrate the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A secondary battery, characterized in that, include: Bipolar electrode, diaphragm, and electrolyte therein for wetting the bipolar electrode and diaphragm; The bipolar electrode includes a positive active material layer, which includes LiNi. 0.5 Mn 1.5 O4 or xLi2MnO3·(1-x)LiMO2, where 0 < x < 1, and M includes one or more of Ni, Co, and Mn; The electrolyte includes a non-aqueous solvent, a lithium salt, and an additive, wherein the additive includes a compound represented by Formula I, and the mass percentage of the compound represented by Formula I is 0.1% to 3% based on the total mass of the electrolyte. In Formula I, R1 and R2 are each independently selected from substituents having 0 to 3 carbon atoms, 0 to 4 degrees of unsaturation, and 0 to 3 heteroatoms, wherein the heteroatoms include nitrogen atoms and / or sulfur atoms.

2. The secondary battery according to claim 1, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the compound represented by Formula I is 0.1% to 1%.

3. The secondary battery according to claim 1, characterized in that, In Formula I, R1 and R2 are each independently selected from any one of alkyl, alkenyl, and amino groups.

4. The secondary battery according to claim 1, characterized in that, The bipolar electrode also includes a bipolar current collector and a negative electrode active material layer, wherein the positive electrode active material layer and the negative electrode active material layer are respectively disposed on the two sides of the bipolar current collector.

5. The secondary battery according to claim 4, characterized in that, The electrolyte between adjacent bipolar current collectors is sealed with encapsulating adhesive.

6. The secondary battery according to claim 5, characterized in that, The encapsulating adhesive includes epoxy resin adhesive and epoxy resin curing adhesive, and the epoxy resin adhesive includes bisphenol A type epoxy resin adhesive.

7. The secondary battery according to claim 1, characterized in that, The secondary battery further includes a positive electrode and a negative electrode, the positive electrode and the negative electrode are respectively disposed on both sides of the stacked electrode body of the bipolar electrode, and the separator is disposed between adjacent bipolar electrodes, between the bipolar electrode and the positive electrode, and between the bipolar electrode and the negative electrode.

8. The secondary battery according to claim 1, characterized in that, The lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium acetate, lithium methanesulfonate, and lithium trifluoromethylsulfonate; the mass percentage of the lithium salt is 12% to 16% based on the total mass of the electrolyte.

9. The secondary battery according to claim 1, characterized in that, The non-aqueous solvent includes one or more of carbonates, carboxylic esters, ethers, and nitriles; the carbonate includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, fluoroethylene carbonate, and ethyl fluorocarbonate; the carboxylic ester includes one or more of ethyl formate, ethyl acetate, propyl acetate, and ethyl propionate; the ether includes ethylene glycol dimethyl ether and / or diethanol diethyl ether; and the nitriles include one or more of acetonitrile, propionitrile, butyronitrile, and valerate.

10. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 9.

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