Electrolyte, secondary battery, battery module, battery pack and electric device

Abstract

This application discloses an electrolyte solution, a secondary battery, a battery module, a battery pack, and an electric device. The electrolyte solution contains an organic solvent including a first organic solvent represented by Formula 1 and an additive including a first additive, and the first additive is one or more selected from the compounds represented by Formula 2A and Formula 2B. In Formula 1, R1 and R2 are each independently one of a C1-C3 alkyl group and a C1-C3 haloalkyl group, and in Formula 2A, R 21 , R 22 , R 23 , R 24 are each independently one of a single bond and a methylene group, and in Formula 2B, R 31 , R 32 , R 33 , R 34 are each independently a single bond or a methylene group, and R4 is a single bond, -O-, a C1-C3 alkylene group, a C1-C3 haloalkylene group, or a C1-C3 oxaalkylene group. The secondary battery of the present invention has a long cycle life and storage life, and at the same time has good fast charging performance. [Formula 1] TIFF2023538722000084.tif110151

Description

[Technical field]

[0001] The present application relates to the field of secondary battery technology, and in particular to an electrolyte, a secondary battery, a battery module, a battery pack, and an electric device. [Background technology]

[0002] As the problems of global climate change and environmental pollution become more and more serious, electric vehicles based on battery drive are developed due to their environmentally friendly and pollution-free characteristics. However, compared with the fast and immediate refueling of traditional fuel vehicles, electric vehicles generally have a low charging ratio, which makes the charging time of electric vehicles longer. This problem of electric vehicles not only brings consumers anxiety about continuous driving, but also limits the rapid popularization of electric vehicles. Summary of the Invention [Problem to be solved by the invention]

[0003] The objective of the present application is to provide an electrolyte, a secondary battery, a battery module, a battery pack and an electrical device, which allows the battery to have good fast charging performance while having a long cycle life and storage life. [Means for solving the problem]

[0004] A first aspect of the present application provides an electrolyte solution comprising an organic solvent and an additive. The organic solvent comprises a first organic solvent represented by formula 1, in which R1 and R2 are each independently one of a C1-C3 alkyl group and a C1-C3 haloalkyl group. The additive comprises a first additive, which is one or more selected from the compounds represented by formula 2A and formula 2B, in which R 21 , R 22 , R 23 , R 24 are each independently one of a single bond and a methylene group; 31 , R 32 , R 33 , R 34are each independently one of a single bond and a methylene group, and R4 is one of a single bond, -O-, a C1-C3 alkylene group, a C1-C3 haloalkylene group, and a C1-C3 oxaalkylene group. [ka] [ka] [ka]

[0005] The combination of the first additive and the first organic solvent can ensure that the first organic solvent greatly improves the conductivity of the electrolyte, while at the same time ensuring that the battery has good cycle performance and storage performance.

[0006] In any embodiment of the present application, in formula 1, R1 and R2 are each independently one of methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl.By selecting a suitable first organic solvent, the viscosity of the electrolyte can be maintained within a suitable range, so that the electrolyte has a higher conductivity and the battery has a better fast charging performance.

[0007] In any embodiment of the present application, the first organic solvent is one or more selected from the following compounds: [ka] [ka] [ka] [ka] [ka] [ka]

[0008] By selecting the above compound as the first organic solvent, the viscosity of the electrolyte can be made appropriate, resulting in higher electrical conductivity.

[0009] In any embodiment of the present application, the first organic solvent is one or two selected from the following compounds: [ka] [ka]

[0010] Compounds 1-1 and 1-2 have lower viscosities and have a more significant effect of improving the conductivity of the electrolyte.

[0011] In any embodiment of the present application, in formula 2A, R 21 , R 22 , R 23 , R 24 each independently represents a single bond or a methylene group.

[0012] Selectable, R 21 , R 22 , R 23 , R 24 is not a single bond at the same time.

[0013] More specifically, R 21 , R 22 one or two of R 23 , R 24 One or two of the groups are methylene groups.

[0014] In any embodiment of the present application, in formula 2B, R 31 , R 32 , R 33 , R 34 are each independently one of a single bond and a methylene group, and R 31 , R 32 , R33 , R 34 is not a single bond at the same time.

[0015] In any embodiment of the present application, in formula 2B, R4 is one of a single bond, -O-, a methylene group, an ethylene group, a propylene group, a fluoromethylene group, a fluoroethylene group, a fluoropropylene group, a methyleneoxy group, an ethyleneoxy group, and a propyleneoxy group.

[0016] Optionally, R4 is one of a single bond, a methylene group, an ethylene group, and a propylene group.

[0017] The first additive having a substituent within the above range can form a dense and stable interfacial film on the surface of the negative electrode active material and can block direct contact between the first organic solvent and the negative electrode active material, thereby further enhancing the reversibility of desorption / occlusion of active ions between the positive electrode sheet and the negative electrode sheet, and improving the discharge capacity and cycle performance of the battery.

[0018] In any embodiment of the present application, when R4 is a single bond, R 31 , R 32 One or two of the groups are methylene groups, and the rest are single bonds.

[0019] In any embodiment of the present application, when R4 is a single bond, R 33 , R 34 One or two of the groups are methylene groups, and the rest are single bonds.

[0020] In any embodiment of the present application, when R4 is a single bond, R 31 , R 32 One of the groups is a methylene group, and R 33 , R 34 One of the is a methylene group and the rest are single bonds.

[0021] In any embodiment of the present application, when R4 is a single bond, R 31 , R 32 are all methylene groups, and R 33, R 34 One of the is a methylene group and the rest are single bonds.

[0022] In any embodiment of the present application, when R4 is a single bond, R 33 , R 34 are all methylene groups, and R 31 , R 32 One of the is a methylene group and the rest are single bonds.

[0023] In any embodiment of the present application, when R4 is a single bond, R 31 , R 32 , R 33 , R 34 are all methylene groups.

[0024] In any embodiment of the present application, the first additive is one or more selected from the following compounds: [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0025] The first additive can form a stable and durable interfacial film on the surface of the negative electrode active material, thereby further improving the cycle performance and storage performance of the battery.

[0026] In any embodiment of the present application, optionally, the first additive is one or more selected from the following compounds: [ka] [ka] [ka] [ka]

[0027] In any embodiment of the present application, based on the total mass of the organic solvent, the mass percentage of the first organic solvent is w1, and the range of w1 is 20% to 80%. Optionally, the range of w1 is 30% to 70%. By controlling the mass percentage of the first organic solvent within a suitable range, the fast charging performance of the battery can be improved, and at the same time, the battery can have good cycle performance and storage performance.

[0028] In any embodiment of the present application, based on the total mass of the electrolyte, the mass percentage of the first additive is w2, and the range of w2 is 0.1%-10%. Optionally, the range of w2 is 0.5%-5%. By controlling the mass percentage of the first additive within a suitable range, the battery can have good fast charging performance, cycle performance and storage performance at the same time.

[0029] In any embodiment of the present application, the additive further comprises a second additive, and the second additive comprises one or more of the following: unsaturated cyclic carbonate compounds, halogen-substituted cyclic carbonate compounds, sulfate compounds, sulfite compounds, sultone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds, isocyanate compounds, phosphazene compounds, cyclic acid anhydride compounds, phosphite compounds, phosphate compounds, borate compounds, and carboxylate compounds. These second additives can form a denser and more stable interfacial film on the surface of the positive electrode active material and / or the negative electrode active material, which helps to further improve the cycle performance and storage performance of the battery.

[0030] In any embodiment of the present application, the second additive comprises one or two of the following compounds: [ka] [ka]

[0031] When the electrolyte contains one or both of the above two compounds, the cycle performance and storage performance of the battery can be further improved.

[0032] In any embodiment of the present application, based on the total mass of the electrolyte, the mass percentage of the second additive is w3, and the range of w3 is ≦10%. Optionally, the range of w3 is ≦5%. By controlling the mass percentage of the second additive within a suitable range, the cycle performance of the battery can be further improved.

[0033] In any embodiment of the present application, the organic solvent further comprises a second organic solvent, and the second organic solvent comprises one or more of a cyclic carbonate compound and a chain carbonate compound. Optionally, the second organic solvent comprises a cyclic carbonate compound, or a combination of a cyclic carbonate compound and a chain carbonate compound. By further comprising the second organic solvent in the organic solvent, a battery including the electrolyte can have good fast charging performance.

[0034] In any embodiment of the present application, the second organic solvent comprises one or more of ethylene carbonate, propylene carbonate, 1,2-butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate. By including the second organic solvent of the above compound in the electrolyte, the battery including the electrolyte can have better rapid charging performance.

[0035] In any embodiment of the present application, based on the total mass of the organic solvent, the mass percentage of the cyclic carbonate compound is w4, and the range of w4 is 20% to 80%. Optionally, the range of w4 is 20% to 50%. The high dielectric constant of the cyclic carbonate compound is helpful for dissociation of the lithium salt. By controlling the mass percentage of the cyclic carbonate compound within a suitable range, the battery containing the electrolyte can have better fast charging performance.

[0036] In any embodiment of the present application, the electrolyte further comprises a lithium salt, the lithium salt being LiN(C x F 2x+1 SO2)(C y F 2y+1The electrolyte may include one or more of the following: Li(FSO2), LiPF6, LiBF4, LiBOB, LiDFOB, LiPO2F2, LiDFOP, LiTFOP, LiAsF6, Li(FSO2)2N, LiCF3SO3, and LiClO4, where x and y are positive integers. The inclusion of the lithium salt in the electrolyte can help form a uniform, dense, and low-impedance interfacial film on the surface of the negative electrode active material of the battery, and can effectively improve the fast charging performance and cycle performance of the battery.

[0037] In any embodiment of the present application, the conductivity of the electrolyte is ≧12 mS / cm. Optionally, the conductivity of the electrolyte is ≧13 mS / cm. By controlling the conductivity of the electrolyte within an appropriate range, the battery can have good fast charging performance, cycle performance, storage performance and safety performance.

[0038] In any embodiment of the present application, the conductivity of the electrolyte is between 12 mS / cm and 24 mS / cm. Optionally, the conductivity of the electrolyte is between 13 mS / cm and 20 mS / cm.

[0039] A second aspect of the present application provides a secondary battery comprising the electrolyte solution of the first aspect of the present application.

[0040] The secondary battery of the present application contains the electrolyte solution of the first aspect of the present application, and the secondary battery has good rapid charging performance, and at the same time, excellent cycle performance and storage performance.

[0041] In any embodiment of the present application, the secondary battery includes a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. H / Dv50, which is the ratio of the thickness H of the single-sided negative electrode film layer to the volume average particle diameter Dv50 of the negative electrode active material, satisfies ≧3. Optionally, H / Dv50 satisfies ≧3.5. More specifically, the range of H / Dv50 satisfies 4≦H / Dv50≦9. ​​By setting the value of H / Dv50 within an appropriate range, it can be ensured that the secondary battery has a high volume energy density and further improves the rapid charging performance of the secondary battery.

[0042] In any embodiment of the present application, the thickness H of the single-sided negative electrode film layer satisfies ≧60 μm. Optionally, the thickness H of the single-sided negative electrode film layer satisfies ≧65 μm. By setting the thickness H of the single-sided negative electrode film layer within an appropriate range, the energy density of the battery can be further improved.

[0043] In any embodiment of the present application, the volume average particle diameter Dv50 of the negative electrode active material satisfies ≦18 μm. Optionally, the volume average particle diameter Dv50 of the negative electrode active material satisfies 14 μm≦Dv50≦18 μm. By making the volume average particle diameter Dv50 of the negative electrode active material within a suitable range, it is possible to not only increase the diffusion coefficient of the active ions, but also reduce the contact area between the negative electrode membrane layer and the electrolyte, so that the battery can have good fast charging performance, cycle performance and storage performance at the same time.

[0044] In any embodiment of the present application, the compressed density of the negative electrode film layer is 1.4 g / cm 3 ~1.85g / cm 3 Optionally, the compressed density of the negative electrode film layer is 1.6 g / cm 3 ~1.8g / cm 3 By setting the compression density of the negative electrode film layer within an appropriate range, the battery can have both high energy density and good fast charging performance.

[0045] In any embodiment of the present application, the secondary battery includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes one or more of a lithium transition metal oxide, a lithium-containing phosphate having an olivine structure, and their respective modified compounds.

[0046] In any embodiment of the present application, the lithium-containing phosphate having an olivine structure includes one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and modified compounds thereof. The use of these positive electrode active materials in the positive electrode film layer can improve the cycle performance and storage performance of the battery, while at the same time improving the multiplication performance and energy density of the battery.

[0047] A third aspect of the present application provides a battery module including the secondary battery of the second aspect of the present application.

[0048] A fourth aspect of the present application provides a battery pack including one of the secondary battery of the second aspect of the present application and the battery module of the third aspect.

[0049] A fifth aspect of the present application provides an electric device including at least one of the secondary battery according to the second aspect, the battery module according to the third aspect, and the battery pack according to the fourth aspect of the present application. Effect of the Invention

[0050] The battery module, battery pack and electric device of the present application include the secondary battery provided by the present application, and therefore have at least the same advantages as the above-mentioned secondary battery.

[0051] In order to more clearly describe the technical solutions in the embodiments of the present application, the drawings used in the embodiments of the present application are briefly described below. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the attached drawings without creative efforts. [Brief description of the drawings]

[0052] [Figure 1] 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Diagram 2] FIG. 1 is an exploded schematic view of an embodiment of a secondary battery of the present application. [Diagram 3]FIG. 1 is a schematic diagram of an embodiment of a battery module of the present application. [Figure 4] FIG. 1 is a schematic diagram of an embodiment of a battery pack of the present application. [Diagram 5] FIG. 5 is an exploded view of FIG. [Figure 6] FIG. 1 is a schematic diagram of an embodiment of an electrical device that uses a secondary battery of the present application as a power source. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] In order to make the objectives, technical solutions and beneficial technical effects of the present application clearer, the present application will be described in more detail below with reference to the following examples. It should be understood that the examples described herein are only for interpreting the present application, and are not intended to limit the present application.

[0054] For the sake of brevity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly described, and any lower limit can be combined with any other lower limit to form a range not explicitly described, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly described. Also, although not explicitly described, each point or single value between the endpoints of the range is included within this range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit, or can be combined with any other lower limit or upper limit to form a range not explicitly described.

[0055] In the description of this specification, unless otherwise specified, "more than or equal to" and "less than or equal to" include the numbers, and "multiple types" in "one or more types" means two or more types.

[0056] In the present description, unless otherwise specified, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0057] It should be understood that relational terms such as "first," "second," and the like are used only to distinguish one entity or operation from another, and do not necessarily require or imply an actual relationship or order between those entities or operations.

[0058] The above content of the present application is not intended to describe each embodiment or every implementation manner of the disclosure in this application. The following description will more specifically describe exemplary embodiments by way of examples. In various places throughout this application, guidance is provided through a series of examples, which can be used in various combinations. In each example, the listing is a representative combination and should not be construed as exhaustive.

[0059] [Secondary battery]

[0060] A secondary battery, also called a rechargeable battery or battery, refers to a battery that can be continuously used after it has been discharged by activating the active material through charging.

[0061] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charge and discharge process of the battery, active ions (e.g., lithium ions) are absorbed and released back and forth between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and mainly serves to prevent short circuit between the positive electrode and the negative electrode, while allowing the active ions to pass through. The electrolyte is disposed between the positive electrode sheet and the negative electrode sheet, and mainly serves to conduct the active ions.

[0062] [Electrolyte]

[0063] The secondary battery contains an electrolyte, which acts as a bridge through which active ions pass in the secondary battery and transports active ions between the positive and negative electrodes of the battery, and plays an important role in the fast charging performance, specific capacity, cycle efficiency, safety performance, etc. of the battery.

[0064] The inventors have discovered that one important factor affecting the rapid charging performance of a battery is the conductivity of the electrolyte. Adding a carboxylic acid ester to the electrolyte can improve the conductivity of the electrolyte and the rapid charging performance of the battery. The reason is that carboxylic acid esters have the advantages of low viscosity and high dielectric constant, and using them in the electrolyte can improve the ionic conductivity of the electrolyte. However, carboxylic acid esters are not compatible with the negative electrode, and the α-H of the carboxylic acid esters easily reacts with the active lithium obtained by reduction at the negative electrode, causing the loss of active lithium and affecting the cycle performance and storage performance of the battery. In particular, the deterioration of cycle performance and storage performance is more significant under high temperature environments. In addition, the oxidation resistance of carboxylic acid esters is low, and they are easily oxidized and decomposed when stored in a highly charged state, which further affects the storage performance of the battery. In order to reduce the adverse effects of carboxylic acid esters on the cycle performance and storage performance of the battery, a conventional technique has been reported to add cyclic sulfate esters to the electrolyte. The cyclic sulfate ester can form an interfacial film on the surface of both the positive and negative active materials, blocking the direct contact between the positive and negative active materials and the electrolyte, and inhibiting the continuous reaction of the carboxylic acid ester in the negative electrode and the electrolyte. However, the conventional cyclic sulfate ester generates gas during the process of forming the interfacial film, and these continuously generated gases are concentrated at the interfaces between the positive and negative electrode sheets and the separator to form macroscopic bubbles, which block the transport of active ions, thus affecting the cycle performance and storage performance of the battery.

[0065] The inventors have further researched and ingeniously added the first additive represented by formula 2A and / or formula 2B to the electrolyte containing carboxylic acid ester, thus solving the above bottleneck. The electrolyte of the present application has carboxylic acid ester, which can greatly improve the conductivity of the electrolyte and the fast charging performance of the battery, while ensuring that the battery has good cycle performance and storage performance, especially that the battery still has good cycle performance and storage performance under high temperature environment.

[0066] Specifically, the electrolyte of the present application includes an organic solvent including a first organic solvent represented by formula 1 and an additive including a first additive, and the first additive is one or more selected from the compounds represented by formula 2A and formula 2B. Specifically, in some embodiments, the first additive is one or more selected from the compounds represented by formula 2A, in some embodiments, the first additive is one or more selected from the compounds represented by formula 2B, and in some embodiments, the first additive simultaneously includes the compound represented by formula 2A and the compound represented by formula 2B. [ka]

[0067] In formula 1, R1 and R2 are each independently one of a C1-C3 alkyl group and a C1-C3 haloalkyl group, and R1 and R2 may be the same or different. The alkyl group and the haloalkyl group may have a straight chain structure or a branched chain structure. The number of halogen atoms in the haloalkyl group may be one or more. When the haloalkyl group has multiple halogen atoms, these halogen atoms may be the same or different. [ka] [ka]

[0068] In Formula 2A, R 21 , R 22 , R23 , R 24 are each independently one of a single bond and a methylene group (-CH2-). 21 , R 22 , R 23 , R 24 may be the same or different.

[0069] In Formula 2B, R 31 , R 32 , R 33 , R 34 are each independently one of a single bond and a methylene group, and R4 is one of a single bond, -O-, a C1-C3 alkylene group, a C1-C3 haloalkylene group, and a C1-C3 oxaalkylene group. The alkylene group, the haloalkylene group, and the oxaalkylene group may have a straight chain structure or a branched chain structure. The number of halogen atoms in the haloalkylene group may be one or more. When multiple halogen atoms are present in the haloalkylene group, these halogen atoms may be the same or different. The number of oxygen atoms in the oxaalkylene group may be one or more.

[0070] R 31 , R 32 , R 33 , R 34 is a single bond, R4 is R 31 , R 32 , R 33 , R 34 R is directly bonded to the adjacent -O- via a single bond. 31 , R 32 , R 33 , R 34 may be the same or different.

[0071] By adding the first additive to the electrolyte of the present application, it has a high reduction potential, and receives electrons from the negative electrode during charging and is reduced by itself, forming a dense and stable sulfur-containing organic interfacial film on the surface of the negative electrode active material prior to the first organic solvent, and can suppress the reaction between the first organic solvent and the active lithium obtained by reduction at the negative electrode. The first additive has high thermal stability, does not generate gas in the process of forming the sulfur-containing organic interfacial film, and does not affect the cycle performance and storage performance of the battery, especially the cycle performance and storage performance in a high temperature environment. In addition, the first additive forms an interfacial film on the surface of the positive electrode active material prior to the first organic solvent, and can suppress the oxidative decomposition of the first organic solvent at the positive electrode. In addition, the first additive coordinates with the transition metal on the surface of the positive electrode active material to form a complex compound, so that the interfacial film formed on the surface of the positive electrode active material is denser and more stable, and can effectively prevent direct contact between the organic solvent (especially the first organic solvent) and the positive electrode active material.

[0072] The first additive is combined with the first organic solvent, which can greatly improve the conductivity of the electrolyte while ensuring that the battery has good cycle performance and storage performance. Therefore, the electrolyte of the present application can provide the battery with excellent fast charging performance and good cycle performance and storage performance at the same time.

[0073] Without being limited to any theory, the inventors discovered for the first time during the course of their research that the first additive added to the electrolyte suppresses the reaction between the first organic solvent and the negative electrode, and thus acts to ensure good cycle performance and storage performance of the battery, far better than the conventional cyclic sulfate esters (e.g., vinyl sulfate DTD) used in the prior art.

[0074] In some embodiments, in formula 1, R1 and R2 may each independently be one of a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, and a fluoropropyl group. R1 and R2 may be the same or different. The number of fluorine atoms may be one or more. When R1 and R2 are selected from the above groups, the viscosity of the electrolyte can be maintained within a suitable range, so that the electrolyte has a higher conductivity and the battery has a better fast charging performance.

[0075] In some embodiments, the first organic solvent may be one or more selected from the following compounds: [ka] [ka] [ka] [ka] [ka] [ka]

[0076] The inventors have discovered that when the electrolyte contains one or more of the above compounds, the electrolyte has a suitable viscosity and a higher conductivity, so that the fast charging performance of the battery can be significantly improved.

[0077] In some embodiments, the first organic solvent may be one or two selected from the following compounds: [ka] [ka]

[0078] Through careful research, the inventors have found that compound 1-1 and compound 1-2 have lower viscosity, and therefore have a more significant effect of improving the conductivity of the electrolyte, and the battery can have better fast charging performance.

[0079] In some embodiments, based on the total mass of the organic solvent, the mass percentage of the first organic solvent is w1, and the range of w1 may be 20% to 80%. For example, the range of w1 may be 25% to 80%, 25% to 75%, 30% to 70%, 30% to 60%, 35% to 65%, 35% to 60%, 40% to 60%, or 50% to 60%. Taking into full consideration the effect of the first organic solvent in improving the conductivity of the electrolyte and the adverse effects on the cycle performance and storage performance of the battery, the inventors control the mass percentage of the first organic solvent within an appropriate range to improve the rapid charging performance of the battery and at the same time, the battery can have good cycle performance and storage performance.

[0080] In some embodiments, in Formula 2A, R 21 , R 22 , R 23 , R 24 is not a single bond at the same time. Optionally, R 21 , R 22 one or two of R 23 , R 24 One or two of the groups are methylene groups.

[0081] In some embodiments, R 21 , R 23 is a methylene group, and R 22 , R 24 is a single bond.

[0082] In some embodiments, R 21 , R 23 is a methylene group, and R 22 , R 24 One of the is a methylene group and the rest are single bonds.

[0083] In some embodiments, R 21 , R 22 , R 23 , R 24 are all methylene groups.

[0084] In some embodiments, in Formula 2B, R 31 , R 32 , R 33 , R 34 may each independently be one of a single bond and a methylene group, and R 31 , R 32 , R 33 , R 34 is not a single bond at the same time.

[0085] In some embodiments, in Formula 2B, R 31 , R 32 , R 33 , R 34 At least two of the are methylene groups.

[0086] In some embodiments, in formula 2B, R4 may be one of a single bond, O-, a methylene group, an ethylene group, a propylene group, a fluoromethylene group, a fluoroethylene group, a fluoropropylene group, a methyleneoxy group, an ethyleneoxy group, and a propyleneoxy group. Optionally, R4 is one of a single bond, a methylene group, an ethylene group, and a propylene group. These substituents may have a linear or branched structure. The number of fluorine atoms may be one or more.

[0087] When these substituents are within the above ranges, the first additive functions to form a dense and stable interfacial film on the surfaces of the positive and negative active materials, blocking direct contact between the first organic solvent and the positive and negative active materials, and reducing the loss of active lithium, thereby further enhancing the reversibility of the desorption and absorption of active ions between the positive and negative electrode sheets, and improving the discharge capacity and cycle performance of the battery.

[0088] In some embodiments, when R is a single bond, R31 , R 32 One or two of the groups are methylene groups, and the rest are single bonds.

[0089] In some embodiments, when R is a single bond, R 33 , R 34 One or two of the groups are methylene groups, and the rest are single bonds.

[0090] In some embodiments, when R is a single bond, R 31 , R 32 One of the groups is a methylene group, and R 33 , R 34 One of the is a methylene group and the rest are single bonds.

[0091] In some embodiments, when R is a single bond, R 31 , R 32 are all methylene groups, and R 33 , R 34 One of the is a methylene group and the rest are single bonds.

[0092] In some embodiments, when R is a single bond, R 33 , R 34 are all methylene groups, and R 31 , R 32 One of the is a methylene group and the rest are single bonds.

[0093] In some embodiments, when R is a single bond, R 31 , R 32 , R 33 , R 34 are all methylene groups.

[0094] In some embodiments, the first additive may be one or more selected from the following compounds: [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0095] The inventors have discovered that by using one or more of the above compounds as the first additive, a more stable and durable interfacial film can be formed on the surfaces of the positive and negative active materials, and further, the interfacial film can still effectively prevent direct contact between the organic solvent (especially the first organic solvent) and the positive and negative active materials after long-term charging and discharging, thereby further improving the cycle performance and storage performance of the battery.

[0096] In some embodiments, the first additive is one or more selected from the following compounds: [ka] [ka] [ka] [ka]

[0097] In some embodiments, the first additive is one or two selected from the following compounds: [ka] [ka]

[0098] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the first additive is w2, and w2 may be ≦10%. For example, the range of w2 may be 0.05%-10%, 0.1%-10%, 0.5%-10%, 0.5%-8%, 0.5%-5%, 1%-5%, or 2%-5%. By setting the mass percentage of the first additive within a suitable range, the synergistic effect between the first additive and the first organic solvent can be fully achieved. If the mass percentage of the first additive is large and the thickness of the film formed on the surface of the negative electrode active material is large, it may affect the transport speed of the active ions at the negative electrode interface, and the fast charging performance of the battery may not be significantly improved. If the mass percentage of the first additive is small, the continuous reaction between the first organic solvent and the negative electrode may not be effectively inhibited, and the cycle performance and storage performance of the battery may not be significantly improved. The inventors, through creative efforts, select the range of the mass percentage of the first additive, so that the battery has good fast charging performance, cycle performance and storage performance.

[0099] In some embodiments, the additive may further include a second additive. The second additive may include one or more of a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate ester compound, a sulfite ester compound, a sultone compound, a disulfonic acid compound, a nitrile compound, an aromatic compound, an isocyanate compound, a phosphazene compound, a cyclic acid anhydride compound, a phosphite ester compound, a phosphate ester compound, a borate ester compound, and a carboxylate ester compound. These second additives can form a denser and more stable interfacial film on the surface of the positive electrode active material and / or the negative electrode active material, which helps to further improve the cycle performance and storage performance of the battery.

[0100] In some embodiments, the second additive may include one or two of the following compounds: [ka] [ka]

[0101] When the second additive contains one or two of the above two kinds of compounds, the cycle performance and storage performance of the battery can be further improved.

[0102] In some embodiments, the weight percent of the second additive is w3 based on the total weight of the electrolyte, and the range of w3 may be ≦10%. For example, the range of w3 may be ≦9%, ≦8%, ≦7%, ≦6%, ≦5%, ≦4%, ≦3%, ≦2%, or ≦1%.

[0103] In some embodiments, based on the total mass of the electrolyte, the mass percentage w3 of the second additive may be 1% to 10%, 1% to 8%, 1% to 7%, 1% to 5%, 1% to 4%, 1% to 3%, or 1% to 2%.

[0104] By setting the mass percentage of the second additive within an appropriate range, the cycle performance and storage performance of the battery can be further improved.

[0105] In some embodiments, the organic solvent may further include a second organic solvent, and the second organic solvent may include one or more of a cyclic carbonate compound, a chain carbonate compound, etc. Optionally, the second organic solvent may include a cyclic carbonate compound, or a combination of a cyclic carbonate compound and a chain carbonate compound.

[0106] The present application does not specifically limit the type of the chain carbonate compound or the cyclic carbonate compound, and may be selected according to actual needs. In some embodiments, the second organic solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC). When the organic solvent of the present application further includes these second organic solvents, the battery may have good fast charging performance.

[0107] In some embodiments, the weight percent of the second organic solvent may be in the range of 20% to 80% based on the total weight of the organic solvent. Optionally, the weight percent of the second organic solvent is in the range of 20% to 75%, 25% to 75%, 30% to 70%, 40% to 70%, 35% to 65%, 40% to 65%, 40% to 60%, or 40% to 50%.

[0108] In some embodiments, the weight percent of the cyclic carbonate compound is w4, based on the total weight of the organic solvent, and w4 may range from 20% to 80%. For example, w4 may range from 20% to 50%, 25% to 50%, 25% to 45%, 25% to 40%, 25% to 35%, 30% to 50%, 30% to 45%, or 30% to 40%.

[0109] The cyclic carbonate compound has a high dielectric constant, which is helpful for dissociation of the lithium salt. When the mass percentage of the cyclic carbonate compound is controlled within an appropriate range, the battery containing the electrolyte can have better fast charging performance.

[0110] In some embodiments, the mass percentage of the chain carbonate compound may be in the range of 0% to 50%, 0% to 40%, 0% to 30%, 0% to 25%, 0% to 20%, 10% to 50%, 10% to 40%, 10% to 30%, or 10% to 20%, based on the total mass of the organic solvent.

[0111] In some embodiments, the electrolyte further comprises a lithium salt. The present application does not limit the type of lithium salt, and it can be selected according to actual needs. For example, the lithium salt is LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), LiPF6, LiBF4, LiBOB, LiDFOB, LiPO2F2, LiDFOP, LiTFOP, LiAsF6, Li(FSO2)2N, LiCF3SO3 and LiClO4, where x and y are positive integers. When the electrolyte contains the lithium salt, it is helpful to form a uniform, dense and low impedance interfacial film on the surface of the negative electrode active material, which can effectively improve the fast charging performance and cycle performance of the battery.

[0112] In some embodiments, the conductivity of the electrolyte may be ≧12 mS / cm. For example, the conductivity of the electrolyte may be ≧12 mS / cm, ≧13 mS / cm, ≧14 mS / cm, ≧15 mS / cm, ≧16 mS / cm, ≧17 mS / cm, ≧18 mS / cm, ≧19 mS / cm, or ≧20 mS / cm.

[0113] When the conductivity of the electrolyte is within a suitable range, the battery can have good fast charging performance, cycle performance, storage performance and safety performance.

[0114] In some embodiments, the conductivity of the electrolyte may be 12 mS / cm to 24 mS / cm. For example, the conductivity of the electrolyte may be 12 mS / cm to 23 mS / cm, 12 mS / cm to 22 mS / cm, 12 mS / cm to 21 mS / cm, 12 mS / cm to 20 mS / cm, or 13 mS / cm to 20 mS / cm.

[0115] [Negative electrode sheet]

[0116] The secondary battery includes a negative electrode sheet, which typically includes a negative electrode current collector and a negative electrode membrane layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material.

[0117] The ratio H / Dv50 of the thickness H of the single-sided negative electrode film layer to the volume average particle diameter Dv50 of the negative electrode active material may be used to characterize the number of particles in the longitudinal direction of a unit negative electrode film layer.

[0118] The inventors have found that the more the number of particles in the vertical direction of the unit negative electrode membrane layer containing the negative electrode active material, the higher the diffusion coefficient of the active ions, and the better the fast charging performance of the battery, but the more the number of particles in the vertical direction of the unit negative electrode membrane layer containing the negative electrode active material, the greater the contact area between the negative electrode membrane layer and the electrolyte, and the more the side reaction of the electrolyte on the surface of the negative electrode active material particles will be, which will affect the cycle performance and storage performance of the battery to a certain extent. Conversely, the less the number of particles in the vertical direction of the unit negative electrode membrane layer containing the negative electrode active material, the lower the fast charging performance of the battery will be, and the better the cycle performance and storage performance of the battery will be.

[0119] The inventors have selected an appropriate range of H / Dv50 through extensive research. Specifically, the negative electrode sheet of the secondary battery of the present application has a ratio H / Dv50 between the thickness H of the one-sided negative electrode film layer and the volume average particle diameter Dv50 of the negative electrode active material that satisfies ≧3. For example, H / Dv50 satisfies ≧4, ≧5, ≧6, ≧7, ≧8, or ≧9. By setting the value of H / Dv50 within an appropriate range, it is possible to ensure that the secondary battery has a high volumetric energy density and further improve the rapid charging performance of the secondary battery.

[0120] In some embodiments, the ratio H / Dv50 of the thickness H of the single-sided negative electrode film layer to the volume average particle diameter Dv50 of the negative electrode active material may satisfy 4≦H / Dv50≦9. ​​By limiting the ratio H / Dv50 of the thickness H of the single-sided negative electrode film layer to the volume average particle diameter Dv50 of the negative electrode active material within an appropriate range and combining it with the electrolyte of the present application, a secondary battery having excellent fast charging performance, long service life and high energy density at the same time can be obtained.

[0121] In some embodiments, the thickness H of the single-sided negative electrode film layer may satisfy ≧60 μm. Optionally, the thickness H of the single-sided negative electrode film layer may satisfy ≧65 μm. More specifically, the thickness H of the single-sided negative electrode film layer may satisfy ≧70 μm. By controlling the thickness H of the single-sided negative electrode film layer within an appropriate range, the energy density of the battery can be further improved.

[0122] In some embodiments, the volume average particle diameter Dv50 of the negative electrode active material may satisfy ≦18 μm. Optionally, the volume average particle diameter Dv50 of the negative electrode active material may satisfy 14 μm≦Dv50≦18 μm. When the thickness H of the single-sided negative electrode film layer is constant, the smaller the volume average particle diameter Dv50 of the negative electrode active material, the higher the diffusion coefficient of the active ions, but the volume average particle diameter Dv50 of the negative electrode active material should not be too small, which will increase the contact area between the negative electrode film layer and the electrolyte, and further affect the cycle performance and storage performance of the battery. By setting the volume average particle diameter Dv50 of the negative electrode active material within an appropriate range, it is possible to not only increase the diffusion coefficient of the active ions, but also reduce the contact area between the negative electrode film layer and the electrolyte, so that the battery can have good fast charging performance, cycle performance and storage performance at the same time.

[0123] In some embodiments, the negative electrode film layer has a compressed density of 1.4 g / cm 3 ~1.85g / cm 3 Optionally, the compressed density of the negative electrode film layer is 1.6 g / cm 3 ~1.8g / cm 3 By controlling the compression density of the negative electrode film layer within an appropriate range, the negative electrode active material particles in the negative electrode film layer can be intimately contacted, and the content of the negative electrode active material in a unit volume can be improved, thereby increasing the energy density of the battery.

[0124] In the secondary battery of the present application, the type of negative electrode active material is not specifically limited, and negative electrode active materials used in secondary batteries known in the art may be used. For example, the negative electrode active material may include one or more of graphite, soft carbon, hard carbon, mesocarbon microspheres, carbon fibers, carbon nanotubes, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include one or more of silicon alone, silicon oxide, silicon carbon composites, silicon nitrogen composites, and silicon alloy materials. The tin-based material may include one or more of tin alone, tin oxide, and tin alloy materials. The present application is not limited to these materials, and other conventional known materials used as negative electrode active materials in secondary batteries may be used. These negative electrode active materials may be used alone or in combination of two or more.

[0125] In the secondary battery of the present application, the negative electrode film layer typically includes a negative electrode active material, an optional adhesive, an optional conductive agent, and other optional auxiliary agents. The negative electrode film layer is typically formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold rolling. The negative electrode slurry is typically formed by dispersing the negative electrode active material, the optional conductive agent, the optional adhesive, and other optional auxiliary agents in a solvent, and uniformly stirring the mixture. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. Therein, the type and content of the conductive agent and adhesive are not specifically limited and may be selected according to actual needs. For example, the conductive agent may include one or more of superconducting carbon, carbon black (e.g., acetylene black, ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. By way of example, the adhesive may include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). Other optional auxiliary agents may include thickeners (e.g., sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, and the like.

[0126] In the secondary battery of the present application, the negative electrode film layer may be disposed on one side of the negative electrode current collector, or may be disposed on both sides of the negative electrode current collector at the same time. For example, the negative electrode current collector has opposite sides in its thickness direction, and the negative electrode film layer is disposed on any one or both sides of the opposite sides of the negative electrode current collector.

[0127] In the secondary battery of the present invention, the type of the negative electrode current collector is not specifically limited and can be selected according to actual needs.

[0128] In the secondary battery of the present application, the negative electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, the negative electrode current collector may be a copper foil. The composite current collector may include a polymer base layer and a metal material layer formed on at least one surface of the polymer base layer. As an example, the metal material may be one or more selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer base layer may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0129] It should be noted that all negative electrode film layer parameters (e.g., thickness, pressed density, etc.) shown in this application refer to the parameters of the negative electrode film layer on one side of the negative electrode current collector. When the negative electrode film layers are installed on both sides of the negative electrode current collector, the parameters of the negative electrode film layer on any one side are considered to be within the scope of protection of this application if they satisfy the present application. In addition, all ranges of thickness, pressed density, etc. of the negative electrode film layer described in this application refer to the parameters of the negative electrode film layer used in the assembly of the battery after cold rolling and pressing.

[0130] In addition, in the secondary battery of the present application, the negative electrode sheet does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet described in the present application may further include a conductive primer layer (e.g., made of a conductive agent and an adhesive) disposed between the negative electrode current collector and the negative electrode film layer. In some embodiments, the negative electrode sheet described in the present application further includes a protective layer that covers the surface of the negative electrode film layer.

[0131] In this application, the volume average particle size Dv50 of the negative active material is the particle size when the cumulative volume distribution percentage of the negative active material reaches 50%, and can be measured by laser diffraction particle size analysis, for example, refer to standard GB / T 19077.1-2016, and use a laser particle size analyzer (e.g., Malvern Master Size 3000) to measure.

[0132] In this application, the thickness of the negative electrode film layer has a meaning known in the art and can be tested by methods known in the art, for example, using a micrometer (e.g., Mitutoyo 293-100 type, accuracy 0.1 μm).

[0133] In this application, the compression density of the negative electrode film layer has a meaning known in the art and can be tested by a method known in the art. Compression density of the negative electrode film layer = areal density of the negative electrode film layer / thickness of the negative electrode film layer. Here, the areal density of the negative electrode film layer has a meaning known in the art and can be tested by a method known in the art. For example, take a negative electrode sheet after one side coating and cold rolling (in the case of a negative electrode sheet coated on both sides, the negative electrode film layer on one side can be wiped off), punch out a small circle with an area of ​​S1, weigh it and record it as M1, then wipe off the negative electrode film layer of the above negative electrode sheet after weighing, weigh the negative electrode current collector and record it as M0, and the areal density of the negative electrode film layer = (weight of the negative electrode sheet M1 - weight of the negative electrode current collector M0) / S1.

[0134] It should be noted that the above-mentioned various parameter tests on the negative electrode film layer or the negative electrode active material may be performed by sampling and testing during the battery manufacturing process, or may be performed by sampling and testing the manufactured secondary battery.

[0135] When sampling the above test sample from the manufactured secondary battery, for example, sampling can be performed according to the following steps (1) to (3).

[0136] (1) Discharge the secondary battery (for safety reasons, the battery is usually in a fully discharged state), disassemble the battery, take out the negative electrode sheet, immerse the negative electrode sheet in dimethyl carbonate (DMC) for a predetermined time (e.g., 2 to 10 hours), then take out the negative electrode sheet, and perform a drying process at a predetermined temperature and time (e.g., 60°C, 4h), and take out the negative electrode sheet after drying. At this point, the negative electrode sheet after drying can be sampled to test each parameter related to the negative electrode film layer described in this application. (2) The negative electrode sheet dried in step (1) is baked at a predetermined temperature and time (e.g., 400°C, 2h), and an arbitrary area is selected from the negative electrode sheet after baking and sampled for the negative electrode active material (blade scraping powder sampling can be selected). (3) The negative electrode active material collected in step (2) is sieved (e.g., sieved through a 200 mesh sieve), and finally, a sample is obtained for testing each negative electrode active material parameter described in this application.

[0137] [Positive electrode sheet]

[0138] In the secondary battery of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and containing a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on any one or both sides of the two opposing surfaces of the positive electrode current collector.

[0139] In some embodiments, the positive electrode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds. In the secondary battery of the present application, the modified compound of each of the above positive electrode active materials may be a doping modification, a surface coating modification, or a simultaneous modification of doping and surface coating on the positive electrode active material.

[0140] For example, the lithium transition metal oxide may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. For example, the lithium-containing phosphate having an olivine structure may include one or more of lithium iron phosphate, lithium iron phosphate and carbon composite, lithium manganese phosphate, lithium manganese phosphate and carbon composite, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composite, and modified compounds thereof. These positive electrode active materials may be used alone or in combination of two or more.

[0141] In some embodiments, the positive electrode active material may include one or more of lithium-containing phosphates with an olivine structure and modified compounds thereof. In other embodiments, the positive electrode active material may be one or more of lithium-containing phosphates with an olivine structure and modified compounds thereof. The use of these positive electrode active materials in the positive electrode film layer can improve the cycle performance and storage performance of the battery while improving the multiplication performance of the battery. The operating voltage of the battery using these positive electrode active materials is not high, generally ≦4.3V, and the effect of using the first organic solvent and the first additive in combination within this voltage range is better, so that the cycle performance and storage performance of the battery can be further improved.

[0142] In the secondary battery of the present application, the positive electrode membrane layer typically includes a positive electrode active material, an optional adhesive, and an optional conductive agent. The positive electrode membrane layer is typically formed by applying a positive electrode slurry to a positive electrode current collector, drying, and cold rolling. The positive electrode slurry is typically formed by dispersing the positive electrode active material, the optional conductive agent, the optional adhesive, and any other components in a solvent, and uniformly stirring the mixture. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). The type and content of the conductive agent and adhesive are not specifically limited and may be selected according to actual needs. For example, the adhesive may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. By way of example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0143] In the secondary battery of the present application, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, the positive electrode current collector may be an aluminum foil. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may be one or more selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may be selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.

[0144] [Separator]

[0145] The secondary battery of the present application further includes a separator. The separator is disposed between the positive electrode sheet and the negative electrode sheet and serves the function of isolation. The type of the separator is not specifically limited, and any known separator with a porous structure having good chemical stability and mechanical stability may be selected. In some embodiments, the material of the separator may be one or more selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited thereto. The separator may be a single layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer are the same or different. In some embodiments, the separator may be provided with a ceramic coating or a metal oxide coating.

[0146] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be manufactured into an electrode assembly by a winding process or a stacking process.

[0147] In some embodiments, the secondary battery may include an exterior packaging that can be used to package the electrode assembly and the electrolyte.

[0148] In some embodiments, the exterior of the secondary battery may be a hard case such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a soft package such as a pouch-type soft package, etc. The material of the soft package may be one or more of plastics such as polypropylene, polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0149] The present application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. Figure 1 shows an example of a secondary battery 5 having a rectangular structure.

[0150] In some embodiments, referring to FIG. 2, the exterior may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround and form a receiving chamber. The case 51 has an opening communicating with the receiving chamber, and the cover plate 53 is used to cover the opening so as to seal the receiving chamber. The positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed in the receiving chamber. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be adjusted as required.

[0151] In some embodiments, the secondary battery can be assembled into a battery module. The number of secondary batteries included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0152] Fig. 3 is an example of a battery module 4. Referring to Fig. 3, in the battery module 4, the secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may be arranged according to any other method. Furthermore, the secondary batteries 5 may be fixed by a fastening member.

[0153] Optionally, the battery module 4 may include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0154] In some embodiments, the battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0155] 4 and 5 show an example of a battery pack 1. Referring to FIG. 4 and FIG. 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is used to cover the lower housing 3 and form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box according to any method.

[0156] Electrical equipment

[0157] A second aspect of the present application provides an electric device including at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electric device, or may be used as an energy storage unit for the electric device. The electric device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy system, etc.

[0158] The above electric devices can select secondary batteries, battery modules or battery packs according to their usage needs.

[0159] 6 is an example of an electric device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be used to meet the high power and high energy density requirements of the electric device.

[0160] Another example of the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. Such an electric device is usually required to be lightweight and may use a secondary battery as a power source.

[0161] Working Example

[0162] The following examples more specifically describe the disclosure of the present application, and various modifications and variations within the scope of the disclosure of the present application will be apparent to those skilled in the art, so these examples are used for illustrative purposes only. Unless otherwise specified, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment. In addition, all instruments used in the examples are commercially available.

[0163] In the following examples and comparative examples, the artificial graphite, conductive agent acetylene black, adhesive styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) used in the negative electrode sheet are all commercially available. The positive electrode active material lithium iron phosphate, adhesive polyvinylidene fluoride (PVDF), conductive agent acetylene black, and solvent N-methylpyrrolidone (NMP) used in the positive electrode sheet are all commercially available. The electrolyte LiPF6, first organic solvent, second organic solvent, first additive, second additive, and vinyl sulfate (DTD) are all commercially available. The polypropylene membrane used in the separator is commercially available.

[0164] Example 1

[0165] Manufacture of negative electrode sheets

[0166] The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the adhesive, styrene butadiene rubber (SBR), and the thickener, sodium carboxymethyl cellulose (CMC-Na), were dissolved in deionized water as a solvent in a mass ratio of 95:2:2:1, and thoroughly mixed to produce a negative electrode slurry. The negative electrode slurry was evenly applied to the copper foil of the negative electrode current collector, and then dried, cold-rolled, and cut to obtain a negative electrode sheet.

[0167] Manufacture of positive electrode sheets

[0168] The positive electrode active material, lithium iron phosphate, the adhesive, polyvinylidene fluoride (PVDF), and the conductive agent, acetylene black, were dissolved in the solvent, N-methylpyrrolidone (NMP), in a mass ratio of 97:2:1, and thoroughly mixed to produce a positive electrode slurry. The positive electrode slurry was uniformly applied to the aluminum foil of the positive electrode current collector, and then dried, cold-rolled, and cut to obtain a positive electrode sheet.

[0169] Preparation of electrolyte

[0170] In a glove box (H2O content <0.1ppm, O2 content <0.1ppm) with an argon gas atmosphere, compound 1-2, ethylene carbonate (EC), and ethyl methyl carbonate (EMC) were mixed uniformly in a mass ratio of 30:30:40 to prepare an organic solvent. A certain amount of LiPF6 and a certain amount of compound 2-4 were dissolved in the above organic solvent and stirred uniformly to obtain an electrolyte. The mass percentage of compound 2-4 in the electrolyte was 2%, and the conductivity of the electrolyte was 13.5mS / cm.

[0171] Separator

[0172] A polypropylene membrane was used as the separator.

[0173] Secondary battery manufacturing

[0174] The positive electrode sheet, separator, and negative electrode sheet were stacked in order, and the separator was placed between the positive electrode sheet and the negative electrode sheet to serve as isolation, and then wound to obtain an electrode assembly. The electrode assembly was placed in an outer casing, and after drying, an electrolyte was injected. Then, a secondary battery was obtained through processes such as chemical formation and standing. The length of the secondary battery was 194 mm, the width was 70 mm, and the height was 112 mm.

[0175] Examples 2 to 26 and Comparative Examples 1 to 3

[0176] The manufacturing methods of Examples 2 to 26 and Comparative Examples 1 to 3 are similar to that of Example 1, except that the relevant parameters of the electrolyte are adjusted, and the specific electrolyte parameters are shown in Table 1. Among them, the first additive used in the electrolyte of Comparative Example 3 was compound 2-9. [ka]

[0177] Testing part

[0178] (1) Battery quick charging performance test

[0179] The batteries of the above examples and comparative examples were first charged and discharged at a current of 0.33 C (where 1 C indicates that the current value corresponding to the theoretical capacity of the battery is completely discharged within 1 h) at 25° C. Specifically, the steps included the steps of charging the battery at a constant current of 0.33 C until the voltage reached 3.65 V, then charging at a constant voltage of 3.65 V until the current was ≦0.05 C, leaving the battery stationary for 5 min, discharging at a constant current of 0.33 C until the voltage reached 2.5 V, and recording the actual discharge capacity C0 of the battery.

[0180] The batteries were charged at various charge rates of 0.5C0, 0.8C0, 1.2C0, 1.5C0, 2.0C0, 2.5C0, 3.0C0, 4.0C0, and 5.0C0, respectively, until the battery's charge cutoff voltage reached 3.65 V or the negative electrode potential reached 0 V (whichever came first), and after each charge was completed, the batteries were discharged at 0.33C0 until the battery's discharge cutoff voltage reached 2.5 V. The corresponding negative electrode potentials were recorded when the batteries were charged to 10% SOC, 20% SOC, 30% SOC, 40% SOC, 50% SOC, 60% SOC, 70% SOC, and 80% SOC (SOC represents the state of charge of the battery).

[0181] The charge ratio-negative electrode potential curves at various charge states were plotted and linearly fitted to obtain the corresponding charge ratios at the negative electrode potential of 0 V at various charge states, which were the charge windows at the various charge states. The charge windows at various states were C 10%SOC , C 20%SOC , C 30%SOC , C 40%SOC , C 50%SOC , C 60%SOC , C 70%SOC , C 80%SOC It was written as follows: 20%SOC +60 / C 30%SOC +60 / C 40%SOC +60 / C 50%SOC +60 / C 60%SOC +60 / C 70%SOC +60 / C 80%SOC ) × 10%, the charging time T of the battery when charging from 10% SOC to 80% SOC was obtained. The shorter the charging time T, the better the rapid charging performance of the battery.

[0182] (2) Battery cycle performance test at 60℃

[0183] At 60°C, the batteries of the above examples and comparative examples were charged at a constant current of 1C until the voltage reached 3.65V, then charged at a constant voltage of 3.65V until the current was ≦0.05C, and then discharged at a constant current of 1C until the voltage reached 2.5V, which was one charge / discharge process. The discharge capacity at this time was recorded as the discharge capacity of the first cycle of the battery. The charge / discharge cycle was repeated in this manner, and the capacity retention rate of the battery after 500 cycles was calculated.

[0184] Capacity retention of battery after 500 cycles at 60°C (%) = (discharge capacity of battery at 500th cycle / discharge capacity of battery at first cycle) × 100%.

[0185] (3) Gas generation test for batteries stored at 60℃

[0186] At 25°C, the batteries of the above examples and comparative examples were charged at a constant current of 0.33C until the voltage reached 3.65V, then charged at a constant voltage of 3.65V until the current was ≦0.05C, and then discharged at a constant current of 0.33C until the voltage reached 2.5V, and the actual discharge capacity of the battery was recorded as C0. At 25°C, the batteries were continuously charged at a constant current of 0.33C0 until the voltage reached 3.65V, and then charged at a constant voltage of 3.65V until the current was ≦0.05C0, at which point the battery was fully charged, and the volume of the battery was measured and recorded as the volume before storage. The fully charged batteries were stored in a thermostatic box at 60°C, and after storage for 30 days, the batteries were removed from the thermostatic box and the volume was measured.

[0187] Amount of gas generated by a battery stored at 60°C for 30 days (ml / Ah) = (volume of battery after 30 days of storage - volume of battery before storage) / rated battery capacity.

[0188] (4) Capacity retention test for batteries stored at 60℃

[0189] At 25°C, the batteries of the above examples and comparative examples were charged at a constant current of 0.33C until the voltage reached 3.65V, then charged at a constant voltage of 3.65V until the current was ≦0.05C, and the batteries were discharged at a constant current of 0.33C until the voltage reached 2.5V, and the actual discharge capacity of the batteries was recorded as C0. At 25°C, the batteries were continuously charged at a constant current of 0.33C0 until the voltage reached 3.65V, and then charged at a constant voltage of 3.65V until the current was ≦0.05C0, at which point the batteries were fully charged. The fully charged batteries were placed in a thermostatic box at 60°C for 60 days, and the batteries were removed for capacity testing.

[0190] Battery capacity retention after 60 days of storage at 60°C = (battery discharge capacity after 60 days of storage / actual battery discharge capacity C0) x 100%.

[0191] See Table 1 for electrolyte parameters of Examples 1 to 26 and Comparative Examples 1 to 3, and see Table 2 for test results. [Table 1-1] [Table 1-2] [Table 2]

[0192] As can be seen from the test results in Table 2, the use of the first organic solvent in the electrolyte can improve the fast charging performance of the battery, but the poor compatibility between the first organic solvent and the negative electrode leads to deterioration of the cycle performance and storage performance of the battery, especially in high temperature environments. As can be seen from the test results of Comparative Example 2 and Comparative Example 1, even if an appropriate amount of DTD is added to the electrolyte, the effect of improving the cycle performance and storage performance of the battery is not ideal. The main reason is that DTD forms a stable interfacial film on both the surfaces of the positive electrode active material and the negative electrode active material, suppressing the continuous reaction between the negative electrode and the first organic solvent, but DTD generates gas during the formation process of the interfacial film, and the continuously generated gas is concentrated at the interfaces between the positive electrode sheet, the negative electrode sheet and the separator to form macroscopic bubbles, and these bubbles block the transport of lithium ions.

[0193] As can be seen from the test results in Table 2, the batteries of Examples 1 to 26 can significantly improve the cycle performance and storage performance of the batteries by using the first additive instead of DTD, especially the high temperature cycle performance and high temperature storage performance of the batteries can be significantly improved. At the same time, the batteries of Examples 1 to 26 still maintained good fast charging performance.

[0194] As can be seen from the comparison of the test results of Comparative Example 3 and Examples 1 to 26, the batteries of Examples 1 to 26 had better cycle performance and storage performance.

[0195] As can be seen from the comparison of the test results of Examples 1 and 2, when the type of the second organic solvent was changed, the fast charging performance, cycle performance and storage performance of the battery also changed, but the changes were within a reasonable range and were not excessive. Therefore, the present application does not particularly limit the type of the second organic solvent.

[0196] It can be seen from the comparison of the test results of Example 1 and Examples 3 to 8 that, when the content of the first organic solvent is increased, the charging time T of the battery is decreased, the amount of gas generation during high-temperature storage is increased, and the capacity retention rate during high-temperature storage and the cycle capacity retention rate at high temperature are both decreased. This is mainly because, after the content of the first organic solvent is increased, the number of α-H increases, and the loss of active lithium inside the battery increases, so the capacity retention rate of the battery after high-temperature storage is decreased, and the oxidation resistance of the first organic solvent is low and it is easily oxidized and decomposed when stored in a highly charged state, so the amount of gas generation during high-temperature storage of the battery is also increased.

[0197] As can be seen from the comparison of the test results of Example 1 and Examples 9 to 15, when the type of the first additive was changed, the fast charging performance, cycle performance and storage performance of the battery also changed, but within a reasonable range and there was no excessive change.

[0198] As can be seen from the comparison of the test results of Example 1 and Examples 16 to 18, when the type of the first organic solvent was changed, the fast charging performance, cycle performance and storage performance of the battery also changed, but within a reasonable range and the amount of change was not excessive.

[0199] As can be seen from the comparison of the test results of Examples 19 to 26, when the content of the first additive increases, the amount of gas generation during high-temperature storage of the battery decreases, and the charging time of the battery decreases and then increases, and the capacity retention rate of the battery during high-temperature storage and the cycle capacity retention rate at high temperature increase and then decrease. The possible reason is that the first additive has a high reduction potential, and forms a dense and stable sulfur-containing organic interfacial film on the surface of the negative electrode active material before the first organic solvent, which can suppress the continuous reaction between the first organic solvent and the negative electrode, so that the amount of gas generation during high-temperature storage of the battery decreases. However, the first additive has a cyclic structure, and after the content increases, the thickness of the film formed on the surface of the negative electrode active material increases, and the film impedance also increases substantially, which affects the transport speed of lithium ions at the negative electrode interface, so the charging time of the battery also increases to a certain extent, and the capacity retention rate of the battery during high-temperature storage and the cycle capacity retention rate at high temperature decrease to a certain extent.

[0200] Example 27

[0201] Manufacture of negative electrode sheets

[0202] The negative electrode active material, artificial graphite (volume average particle size Dv50 is 17 μm), the conductive agent, acetylene black, the adhesive, styrene butadiene rubber (SBR), and the thickener, sodium carboxymethylcellulose (CMC-Na), were dissolved in deionized water as a solvent in a mass ratio of 95:2:2:1, and thoroughly mixed to produce a negative electrode slurry. The negative electrode slurry was evenly applied to the two surfaces of the copper foil of the negative electrode current collector, and then dried, cold-rolled, and cut to obtain a negative electrode sheet. The negative electrode slurry was dried to form a negative electrode film layer, with the thickness of one side of the negative electrode film layer being 60 μm and the compressed density of the negative electrode film layer being 1.65 g / cm. 3 It was.

[0203] Manufacture of positive electrode sheets

[0204] The positive electrode active material, lithium iron phosphate, the adhesive, polyvinylidene fluoride (PVDF), and the conductive agent, acetylene black, were dissolved in the solvent, N-methylpyrrolidone (NMP), in a mass ratio of 97:2:1, and thoroughly mixed to produce a positive electrode slurry. The positive electrode slurry was uniformly applied to the aluminum foil of the positive electrode current collector, and then dried, cold-rolled, and cut to obtain a positive electrode sheet.

[0205] Preparation of electrolyte

[0206] In a glove box (H2O content <0.1ppm, O2 content <0.1ppm) with an argon gas atmosphere, compound 1-2, ethylene carbonate (EC), and ethyl methyl carbonate (EMC) were mixed uniformly in a mass ratio of 30:30:40 to prepare an organic solvent. A certain amount of LiPF6 and a certain amount of the first additive compound 2-4 were dissolved in the above organic solvent and stirred uniformly to obtain an electrolyte. The mass percentage of compound 2-4 in the electrolyte was 2%, and the conductivity of the electrolyte was 13.5mS / cm.

[0207] Separator

[0208] A polypropylene membrane was used as the separator.

[0209] Secondary battery manufacturing

[0210] The positive electrode sheet, separator, and negative electrode sheet were stacked in order, and the separator was placed between the positive electrode sheet and the negative electrode sheet to serve as isolation, and then wound to obtain an electrode assembly. The electrode assembly was placed in an outer casing, and after drying, an electrolyte was injected. Then, a secondary battery was obtained through processes such as chemical formation and standing. The length of the secondary battery was 194 mm, the width was 70 mm, and the height was 112 mm.

[0211] Examples 28 to 37

[0212] The manufacturing methods of Examples 28 to 37 are similar to those of Example 27, except that the relevant parameters of the negative electrode sheet are adjusted. See Table 3 for the specific parameters.

[0213] Testing part

[0214] (1) Battery volumetric energy density test

[0215] At 25°C, the batteries of the above examples and comparative examples were charged at a constant current of 0.33 C until the voltage reached 3.65 V, and then charged at a constant voltage of 3.65 V until the current was ≦0.05 C. The batteries were discharged at a constant current of 0.33 C until the voltage reached 2.5 V to obtain the discharge energy Q. The length, width, and height of the battery housing were measured using calipers, and the volume V of the battery was calculated.

[0216] Volumetric energy density of battery = discharge energy Q / battery volume V, the unit of volumetric energy density was Wh / L.

[0217] See Table 3 for the negative electrode sheet parameters and battery performance test results of Examples 27 to 37. [Table 3]

[0218] As can be seen from the test results in Table 3, with the increase in the thickness H of the single-sided negative electrode film layer, the volumetric energy density of the battery also increases, but the charging time T is extended. When the thickness H of the single-sided negative electrode film layer is constant, with the decrease in the volume average particle diameter Dv50 of the negative electrode active material, the diffusion path of the active ions is shortened and the charging time T is reduced, but the volume average particle diameter Dv50 of the negative electrode active material should not be too small, which will increase the contact area between the negative electrode film layer and the electrolyte and increase the side reaction of the electrolyte on the surface of the negative electrode active material particles, which will further affect the cycle performance and storage performance of the battery. Therefore, by limiting the ratio H / Dv50 of the thickness of the single-sided negative electrode film layer to the volume average particle diameter Dv50 of the negative electrode active material within an appropriate range and combining it with the electrolyte of the present application, the battery can have good fast charging performance, long service life and high energy density at the same time.

[0219] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and any embodiment that has substantially the same configuration as the technical idea within the scope of the technical solution of the present application and has the same action or effect is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art can conceive of in the embodiments without departing from the gist of the present application, and other forms combining some of the components of the embodiments are also included in the scope of the present application.

Claims

1. The present invention includes an organic solvent including a first organic solvent and an additive including a first additive, and the first organic solvent is one or more kinds selected from the following compounds: 【Chemistry 1】 【Chemistry 2】 【Chemistry 3】 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 The first additive is one or more selected from the compounds represented by formula 2A and formula 2B, 【Chemistry 7】 【Chemistry 8】 In Formula 2A, R ２１ , R ２２ , R ２３ , R ２４ each independently represents one of a single bond and a methylene group, In Formula 2B, R ３１ , R ３２ , R ３３ , R ３４ each independently represents one of a single bond and a methylene group, R ４ is one of a single bond, —O—, a C1-C3 alkylene group, a C1-C3 haloalkylene group, and a C1-C3 oxaalkylene group, The additive further includes a second additive, and the second additive includes one or more of a cyclic carbonate compound containing an unsaturated bond and a halogen-substituted cyclic carbonate compound; Electrolyte.

2. R ２１ , R ２２ , R ２３ , R ２４ is not a single bond, and / or R ３１ , R ３２ , R ３３ , R ３４ are each independently one of a single bond and a methylene group, and R ３１ , R ３２ , R ３３ , R ３４ is not a single bond, and / or R ４ is one of a single bond, -O-, a methylene group, an ethylene group, a propylene group, a fluoromethylene group, a fluoroethylene group, a fluoropropylene group, a methyleneoxy group, an ethyleneoxy group, and a propyleneoxy group; The electrolyte solution according to claim 1.

3. R ３１ , R ３２ , R ３３ , R ３４ , R ４ further satisfies one of the following (1) to (6): (1) R ４ is a single bond, R ３１ , R ３２ one or two of the groups are methylene groups, and the rest are single bonds; (2) R ４ is a single bond, R ３３ , R ３４ one or two of the groups are methylene groups, and the rest are single bonds; (3) R ４ is a single bond, R ３１ , R ３２ One of R is a methylene group; ３３ , R ３４ one of which is a methylene group and the rest are single bonds; (4) R ４ is a single bond, R ３１ , R ３２ are all methylene groups, and R ３３ , R ３４ one of which is a methylene group and the rest are single bonds; (5) R ４ is a single bond, R ３３ , R ３４ are all methylene groups, and R ３１ , R ３２ one of which is a methylene group and the rest are single bonds; (6) R ４ is a single bond, R ３１ , R ３２ , R ３３ , R ３４ are all methylene groups. The electrolyte solution according to any one of claims 1 to 2.

4. The first organic solvent is one or two selected from the following compounds: 【Chemistry 9】 【Chemistry 10】 The electrolyte solution according to any one of claims 1 to 3.

5. The first additive is one or more compounds selected from the following compounds: 【Chemistry 11】 【Chemistry 12】 【Chemistry 13】 【Chemistry 14】 【Chemistry 15】 【Chemistry 16】 【Chemistry 17】 【Chemistry 18】 The electrolyte solution according to any one of claims 1 to 4.

6. Based on the total weight of the organic solvent, the weight percent of the first organic solvent is w1, and the range of w1 is 20% to 80%; The electrolyte solution according to any one of claims 1 to 5.

7. Based on the total weight of the electrolyte, the weight percent of the first additive is w2, and the range of w2 is 0.1% to 10%; The electrolyte solution according to any one of claims 1 to 6.

8. Based on the total weight of the electrolyte, the weight percentage of the second additive is w3, and the range of w3 is ≦10%; The electrolyte solution according to any one of claims 1 to 7.

9. The organic solvent further includes a second organic solvent, and the second organic solvent includes one or more of a cyclic carbonate compound and a chain carbonate compound. The electrolyte solution according to any one of claims 1 to 8.

10. The organic solvent further comprises a second organic solvent, the second organic solvent comprising one or more of ethylene carbonate, propylene carbonate, 1,2-butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; The electrolyte solution according to any one of claims 1 to 9.

11. Based on the total weight of the organic solvent, the weight percent of the cyclic carbonate compound is w4, and the range of w4 is 20% to 80%; The electrolyte solution according to any one of claims 1 to 10.

12. The electrolyte further includes a lithium salt, and the lithium salt is LiN(C ｘ F ２ｘ＋１ SO ２ ) (C ｙ F ２ｙ＋１ SO ２ ), LiPF ６ , LiBF ４ , LiBOB, LiDFOB, LiPO ２ F ２ , LiDFOP, LiTFOP, LiAsF ６ , Li(FSO ２ ) ２ N, LiCF ３ SO ３ and LiClO ４ wherein x and y are positive integers; The electrolyte solution according to any one of claims 1 to 11.

13. The conductivity of the electrolyte is ≧12 mS / cm; The electrolyte solution according to any one of claims 1 to 12.

14. A secondary battery comprising the electrolyte solution according to any one of claims 1 to 13.

15. The secondary battery includes a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material, and H / Dv50, which is a ratio of a thickness H of the single-sided negative electrode film layer to a volume average particle diameter Dv50 of the negative electrode active material, satisfies ≧3; The secondary battery according to claim 14.

16. The thickness H of the single-sided negative electrode film layer satisfies ≧60 μm, and / or The volume average particle diameter Dv50 of the negative electrode active material satisfies ≦18 μm; The secondary battery according to any one of claims 14 to 15.

17. The compressed density of the negative electrode film layer is 1.4 g / cm ３ ~1.85g / cm ３ That is, The secondary battery according to any one of claims 14 to 16.

18. The secondary battery includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes one or more of a lithium transition metal oxide, a lithium-containing phosphate having an olivine structure, and a modified compound thereof; The secondary battery according to any one of claims 14 to 17.

19. A battery module comprising the secondary battery according to any one of claims 14 to 18.

20. A battery pack comprising the secondary battery according to any one of claims 14 to 18 and the battery module according to claim 19.

21. An electric device comprising at least one of the secondary battery according to any one of claims 14 to 18, the battery module according to claim 19, and the battery pack according to claim 20.

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