Lithium ion secondary battery, cell, and electric device

Abstract

The invention provides a lithium ion secondary battery, a battery cell and an electric device. The lithium ion secondary battery comprises a positive pole piece, a negative pole piece and an electrolyte, the electrolyte comprises a first additive, the first additive comprises 1, 3-propene sultone, the mass concentration of the 1, 3-propene sultone in the electrolyte is 0.01%-3.5%, the positive pole piece comprises a positive active material, the negative pole piece comprises a negative active material, and the negative pole piece comprises a negative active material. The positive pole piece comprises a positive active material, the specific surface area of the positive active material is less than or equal to 15m < 2 > / g, the negative pole piece comprises a negative active material, and the specific surface area of the negative active material is less than or equal to 1.5 m < 2 > / g. The lithium ion secondary battery has a relatively good cycle capacity retention ratio and a relatively long cycle life.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a lithium-ion secondary battery, a battery cell, and an electrical device. Background Art

[0002] In recent years, the application scope of secondary batteries such as lithium-ion batteries has become increasingly wide, and they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles and other fields. As secondary batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and safety performance.

[0003] 1,3-Propene sultone (PST) is an electrolyte additive for lithium-ion batteries, which can improve the cycle life of the battery to a certain extent. However, 1,3-Propene sultone is easily hydrolyzed when it encounters water in the electrolyte, making it difficult to exert its own efficacy. At the same time, it is acidic after hydrolysis, which increases the acidity of the electrolyte and increases the corrosiveness to the material, making it difficult to effectively improve the cycle life of the battery. Summary of the invention

[0004] In order to achieve the above-mentioned purpose, the present application provides a lithium-ion secondary battery, a battery cell and an electrical device with a long cycle life.

[0005] The present application provides a lithium ion secondary battery, comprising a positive electrode plate, a negative electrode plate and an electrolyte, wherein the electrolyte comprises a first additive, wherein the first additive comprises 1,3-propylene sultone, wherein the mass concentration of the 1,3-propylene sultone in the electrolyte is 0.01% to 3.5%, and the positive electrode plate comprises a positive electrode active material, wherein the specific surface area of ​​the positive electrode active material is ≤15m 2 / g, the negative electrode sheet comprises a negative electrode active material, and the specific surface area of ​​the negative electrode active material is ≤1.5m 2 / g.

[0006] This study found that in a battery using 1,3-propylene sultone as an additive (the mass concentration of 1,3-propylene sultone in the electrolyte is 0.01%~3.5%), by controlling the specific surface area of ​​the positive electrode active material to ≤15m 2 / g, and the specific surface area of ​​the negative electrode active material is ≤1.5m 2 / g, which can effectively control the effect of moisture in the system on the hydrolysis of 1,3-propylene sultone, reduce acid production, lower the acidity of the electrolyte, and thus improve the cycle capacity retention rate of the battery, so that the battery has a better cycle life.

[0007] Furthermore, by controlling the specific surface areas of the positive electrode active material and the negative electrode active material within a suitable range, it is possible to effectively reduce the acid production caused by the hydrolysis of PST, improve the cycle capacity retention rate of the battery, and obtain a higher energy density.

[0008] In some embodiments, the specific surface area of ​​the positive electrode active material is 8 m 2 / g~15m 2 / g.

[0009] In some embodiments, the particle size Dv50 of the positive electrode active material is 0.5 μm to 2.5 μm.

[0010] In some embodiments, the specific surface area of ​​the negative electrode active material is 1 m 2 / g~1.5m 2 / g.

[0011] In some embodiments, the particle size Dv50 of the negative electrode active material is 8 μm-18 μm.

[0012] In some embodiments, the electrolyte further comprises a second additive, and the second additive comprises a silicon-containing acid-removing additive. The silicon-containing acid-removing additive is used as an additive to effectively capture the proton hydrogen generated by the hydrolysis of 1,3-propene sultone in the electrolyte, reduce the acidity of the electrolyte, and cooperate with the specific surface area of ​​the positive electrode active material and the negative electrode active material to improve the cycle capacity retention rate of the battery.

[0013] In some embodiments, the second additive has one or more of the following characteristics:

[0014] (1) In the electrolyte, the mass concentration of the second additive is 0.01% to 0.5%;

[0015] (2) The second additive includes one or more of tris(trimethylsilyl)phosphate, silazane, N-trimethylsilyl imidazole and tris(trimethylsilyl)borate.

[0016] In some embodiments, the electrolyte further comprises a third additive, and the third additive comprises a combination of a fluorine-containing negative electrode film-forming additive and a double-bond-containing negative electrode film-forming additive. The fluorine-containing negative electrode film-forming additive and the double-bond-containing negative electrode film-forming additive can cooperate with 1,3-propylene sulfone to form a stable composite SEI film on the surface of the negative electrode plate, reduce the occurrence of side reactions, improve the stability of the negative electrode plate, and thus improve the cycle capacity retention rate. In addition, it can also reduce the consumption of active lithium during the cycle and improve the initial capacity of the battery.

[0017] In some embodiments, the third additive has one or more of the following characteristics:

[0018] (1) The fluorine-containing negative electrode film-forming additive includes one or more of fluoroethylene carbonate and fluoroalkyl-substituted vinyl carbonate;

[0019] (2) In the electrolyte, the mass concentration of the fluorine-containing negative electrode film-forming additive is 0.01% to 3%;

[0020] (3) The negative electrode film-forming additive containing double bonds includes one or more of vinylene carbonate, alkyl-substituted vinylene carbonate and alkenyl-substituted vinylene carbonate;

[0021] (4) In the electrolyte, the mass concentration of the negative electrode film-forming additive containing double bonds is 0.01%~3%.

[0022] In some embodiments, the positive electrode active material includes lithium iron phosphate.

[0023] In some embodiments, the negative electrode active material includes one or both of natural graphite and artificial graphite.

[0024] In a second aspect of the present application, a battery cell is provided, comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the electrolyte comprises a first additive, wherein the first additive comprises 1,3-propylene sultone, wherein the mass concentration of the 1,3-propylene sultone in the electrolyte is 0.01% to 5%, and the positive electrode sheet comprises a positive electrode active material, wherein the specific surface area of ​​the positive electrode active material is ≤15m 2 / g, the negative electrode sheet comprises a negative electrode active material, and the specific surface area of ​​the negative electrode active material is ≤1.5m 2 / g.

[0025] In some embodiments, the electrolyte further comprises a second additive, wherein the second additive comprises a silicon-containing acid-scavenging additive.

[0026] In some embodiments, the second additive has one or more of the following characteristics:

[0027] (1) In the electrolyte, the mass concentration of the second additive is 0.01% to 1%;

[0028] (2) The second additive includes one or more of tris(trimethylsilyl)phosphate, silazane, N-trimethylsilyl imidazole and tris(trimethylsilyl)borate.

[0029] In some embodiments, the electrolyte further comprises a third additive, wherein the third additive comprises a combination of a fluorine-containing negative electrode film-forming additive and a double bond-containing negative electrode film-forming additive.

[0030] In some embodiments, the third additive has one or more of the following characteristics:

[0031] (1) The fluorine-containing negative electrode film-forming additive includes one or more of fluoroethylene carbonate and fluoroalkyl-substituted vinyl carbonate;

[0032] (2) In the electrolyte, the mass concentration of the fluorine-containing negative electrode film-forming additive is 0.01% to 5%;

[0033] (3) The negative electrode film-forming additive containing double bonds includes one or more of vinylene carbonate, alkyl-substituted vinylene carbonate and alkenyl-substituted vinylene carbonate;

[0034] (4) In the electrolyte, the mass concentration of the negative electrode film-forming additive containing double bonds is 0.01%~5%.

[0035] A third aspect of the present application provides an electrical device comprising the lithium-ion secondary battery described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to better describe and illustrate the embodiments or examples provided by the present application, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes of these applications currently understood. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0037] Figure 1 It is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0038] Figure 2 for Figure 1 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0039] Figure 3 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0040] Description of reference numerals:

[0041] 1. Secondary battery; 11. Casing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0044] The "range" disclosed in the present application can be limited in the form of a lower limit and an upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The range limited in this way can be including or excluding end values, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are also listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents the abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to listing the parameter as, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0045] In the present application, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments. The "implementation methods" mentioned herein have a similar understanding.

[0048] Those skilled in the art will appreciate that, in the methods of each embodiment or example, the order in which each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0049] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0050] In this application, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0051] In one embodiment of the present application, a lithium ion secondary battery is provided, comprising a positive electrode plate, a negative electrode plate and an electrolyte, wherein the electrolyte comprises a first additive, wherein the first additive comprises 1,3-propylene sultone, wherein the mass concentration of the 1,3-propylene sultone in the electrolyte is 0.01% to 3.5%, and the positive electrode plate comprises a positive electrode active material, wherein the specific surface area of ​​the positive electrode active material is ≤15m 2 / g, the negative electrode sheet comprises a negative electrode active material, and the specific surface area of ​​the negative electrode active material is ≤1.5m 2 / g.

[0052] 1,3-Propylene sultone is prone to hydrolysis and acid production when the water content is high, which deteriorates the cycle life of the battery. Materials with too large a specific surface area will absorb more water, which in turn leads to a higher water content in the system. This study found that in batteries using 1,3-propene sultone as an additive (the mass concentration of 1,3-propene sultone in the electrolyte is 0.01%~3.5%), by controlling the specific surface area of ​​the positive electrode active material to ≤15m 2 / g, and the specific surface area of ​​the negative electrode active material is ≤1.5m 2 / g, which can effectively control the effect of moisture in the system on the hydrolysis of 1,3-propylene sultone, reduce acid production, lower the acidity of the electrolyte, and thus improve the cycle capacity retention rate of the battery, so that the battery has a better cycle life.

[0053] Without limitation, the mass concentration of 1,3-propene sultone in the electrolyte can be detected by organic gas chromatography; the specific surface areas of the positive electrode active material and the negative electrode active material can be detected by BET.

[0054] It can be understood that the specific surface areas of the positive electrode active material and the negative electrode active material are both greater than zero.

[0055] It should be noted that during the formation or recycling process of the battery, the additives in the electrolyte may change. For ease of understanding, this application refers to the battery after formation or recycling as a "lithium-ion secondary battery", and the battery before formation and recycling as a "battery cell". The mass percentage or concentration of the components below will be explained from these two aspects.

[0056] Corresponding to the “mass concentration of 1,3-propene sultone in the electrolyte is 0.01% to 3.5%” in the above-mentioned lithium ion secondary battery, the “mass concentration of 1,3-propene sultone in the electrolyte is 0.01% to 5%” in the battery cell.

[0057] Specifically, the mass concentration of the 1,3-propylene sultone in the electrolyte includes but is not limited to: 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or a range between any two of the foregoing. Further, the mass concentration of the 1,3-propylene sultone in the electrolyte is 0.1% to 2%. Correspondingly, in the battery cell, "the mass concentration of the 1,3-propylene sultone in the electrolyte is 0.1% to 3%".

[0058] Furthermore, when the specific surface area of ​​the positive electrode active material and the negative electrode active material is too small, the dynamic performance of the battery will be reduced, the polarization will increase, and the cut-off voltage will be reached faster when charging under constant current or constant power conditions, the capacity provided will be reduced, and the energy density of the battery will be reduced. Therefore, it is necessary to control the specific surface area of ​​the positive electrode active material and the negative electrode active material within a suitable range to effectively reduce the hydrolysis and acid production of PST, improve the cycle capacity retention rate of the battery, and obtain a higher energy density.

[0059] In some embodiments, the specific surface area of ​​the positive electrode active material is 8 m 2 / g~15m 2 / g. Specifically, the specific surface area of ​​the positive electrode active material includes but is not limited to: 8m 2 / g, 8.5m 2 / g, 9m 2 / g, 9.7m 2 / g, 10m 2 / g, 10.2m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14m 2 / g, 14.8m 2 / g, 15m 2 / g or a range between any two of the foregoing. Further, the specific surface area of ​​the positive electrode active material is 10m 2 / g~12m 2 / g.

[0060] In some embodiments, the specific surface area of ​​the negative electrode active material is 1 m 2 / g~1.5m 2 / g. Specifically, the specific surface area of ​​the negative electrode active material includes but is not limited to: 1m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g or a range between any two of the foregoing. Further, the specific surface area of ​​the negative electrode active material is 1.2m 2 / g~1.4m 2 / g.

[0061] Furthermore, the particle size Dv50 of the positive electrode active material and the negative electrode active material is related to the specific surface area. The larger the particle size Dv50, the smaller the specific surface area, the increased polarization, and at the same time, the compaction of the positive electrode active layer will also decrease, causing the energy density to decrease; the smaller the particle size Dv50, the larger the specific surface area, the easier it is for PST to hydrolyze and produce acid, reducing the battery's cycle capacity retention rate.

[0062] In some embodiments, the particle size Dv50 of the positive electrode active material is 0.5μm~2.5μm. Specifically, the particle size Dv50 of the positive electrode active material includes but is not limited to: 0.5μm, 0.8μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.5μm or a range between any two of the foregoing. Further, the particle size Dv50 of the positive electrode active material is 0.5μm~1.5μm. Further, the particle size Dv50 of the positive electrode active material is 1μm~1.3μm.

[0063] In some embodiments, the particle size Dv50 of the negative electrode active material is 8μm~18μm. Specifically, the particle size Dv50 of the negative electrode active material includes but is not limited to: 8μm, 8.9μm, 9.5μm, 10.1μm, 11μm, 12.2μm, 12.5μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm or a range between any two of the foregoing. Further, the particle size Dv50 of the negative electrode active material is 8μm~12.5μm. Further, the particle size Dv50 of the negative electrode active material is 9.5μm~11μm.

[0064] Without limitation, the particle size Dv50 of the positive electrode active material and the negative electrode active material can be detected by laser particle size distribution.

[0065] In some embodiments, the electrolyte further comprises a second additive, and the second additive comprises a silicon-containing acid-removing additive. The silicon-containing acid-removing additive is used as an additive to effectively capture the proton hydrogen generated by the hydrolysis of 1,3-propene sultone in the electrolyte, reduce the acidity of the electrolyte, and cooperate with the specific surface area of ​​the positive electrode active material and the negative electrode active material to improve the cycle capacity retention rate of the battery.

[0066] In some embodiments, in the electrolyte, the mass concentration of the second additive is 0.01% to 0.5%. Correspondingly, in the battery cell, "the mass concentration of the second additive in the electrolyte is 0.01% to 1%". Reasonable control of the mass concentration of the second additive in the electrolyte can effectively capture the proton hydrogen in the electrolyte while obtaining a lower impedance and comprehensively improving the cycle capacity retention rate. Specifically, the mass concentration of the second additive in the electrolyte includes but is not limited to: 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5% or a range between any two of the foregoing. Further, the mass concentration of the second additive in the electrolyte is 0.01% to 0.3%. Correspondingly, in the battery cell, "the mass concentration of the second additive in the electrolyte is 0.05% to 0.5%".

[0067] In some embodiments, the second additive includes one or more of tris(trimethylsilyl)phosphate (TMSP), silazane, N-trimethylsilyl imidazole, and tris(trimethylsilyl)borate.

[0068] Without limitation, the mass concentration of the second additive in the electrolyte can be detected by organic gas chromatography.

[0069] In some embodiments, the electrolyte further comprises a third additive, and the third additive comprises one or more of a fluorine-containing negative electrode film-forming additive and a double-bond-containing negative electrode film-forming additive. Furthermore, the third additive comprises a combination of a fluorine-containing negative electrode film-forming additive and a double-bond-containing negative electrode film-forming additive. The fluorine-containing negative electrode film-forming additive and the double-bond-containing negative electrode film-forming additive can cooperate with 1,3-propylene sulfone to form a stable composite SEI film on the surface of the negative electrode plate, reduce the occurrence of side reactions, improve the stability of the negative electrode plate, and thereby improve the cycle capacity retention rate. In addition, it can also reduce the consumption of active lithium during the cycle and improve the initial capacity of the battery.

[0070] Without limitation, the fluorine-containing negative electrode film-forming additive includes one or more of fluoroethylene carbonate and its analogs (e.g., fluoroalkyl-substituted ethylene carbonate). The alkyl group may be a C1 to C5 alkyl group. For example, (FEC), and One or more of .

[0071] Without limitation, the negative electrode film-forming additive containing double bonds includes one or more of vinylene carbonate and its analogs (e.g., alkyl-substituted vinylene carbonate, alkenyl-substituted vinylene carbonate). The alkyl group may be a C1-C5 alkyl group; the alkenyl group may be a C2-C5 alkenyl group. For example, (VC), , and One or more of .

[0072] In some embodiments, in the electrolyte, the mass concentration of the fluorine-containing negative electrode film-forming additive is 0.01%~3%. Correspondingly, in the battery cell, "the mass concentration of the fluorine-containing negative electrode film-forming additive in the electrolyte is 0.01%~5%". Specifically, the mass concentration of the fluorine-containing negative electrode film-forming additive in the electrolyte includes but is not limited to: 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% or a range between any two of the foregoing. Further, in the electrolyte, the mass concentration of the fluorine-containing negative electrode film-forming additive is 0.5%~2%. Correspondingly, in the battery cell, "the mass concentration of the fluorine-containing negative electrode film-forming additive in the electrolyte is 1%~3.5%".

[0073] In some embodiments, in the electrolyte, the mass concentration of the negative electrode film-forming additive containing double bonds is 0.01%~3%. Correspondingly, in the battery cell, "the mass concentration of the negative electrode film-forming additive containing double bonds in the electrolyte is 0.01%~5%". Specifically, the mass concentration of the negative electrode film-forming additive containing double bonds in the electrolyte includes but is not limited to: 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% or the range between any two of the foregoing. Further, in the electrolyte, the mass concentration of the negative electrode film-forming additive containing double bonds is 0.5%~2%. Correspondingly, in the battery cell, "the mass concentration of the negative electrode film-forming additive containing double bonds in the electrolyte is 1%~3.5%".

[0074] Without limitation, the negative electrode film-forming additive containing double bonds in the electrolyte and the mass concentration of the negative electrode film-forming additive containing double bonds can be detected by organic gas chromatography.

[0075] In some embodiments, the positive electrode active material includes lithium iron phosphate.

[0076] In some embodiments, the negative electrode active material includes one or both of natural graphite and artificial graphite.

[0077] In some other embodiments of the present application, an electrical device is provided, comprising the lithium-ion secondary battery as described above.

[0078] The secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0079] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0080] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0081] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0082] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0083] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder 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.

[0084] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As non-limiting examples, 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.

[0085] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any one of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode collector coated with the positive electrode slurry can be on a single surface of the positive electrode collector or on both surfaces of the positive electrode collector. The surface of the positive electrode collector coated with the positive electrode slurry can be on a single surface of the positive electrode collector or on both surfaces of the positive electrode collector. The solid content of the positive electrode slurry can be 40wt%~80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000mPa·s~25000mPa·s. When applying the positive electrode slurry, the coating unit surface density based on dry weight (excluding solvent) can be 15 mg / cm 2 ~35mg / cm 2 The compaction density of the positive electrode can be 3.0g / cm 3 ~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0086] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0087] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0088] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0089] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0090] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0091] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0092] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the surface of the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode collector coated with the negative electrode slurry can be on a single surface of the negative electrode collector or on both surfaces of the negative electrode collector. The solid content of the negative electrode slurry can be 40wt%~60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s~10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75g / m 2 ~220g / m 2 The compaction density of the negative electrode sheet can be 1.0g / cm 3 ~ 1.8g / cm 3 .

[0093] The electrolyte has the function of conducting ions between the positive electrode and the negative electrode.

[0094] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0095] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0096] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, )、ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate ( ), fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0097] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0098] In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0099] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may be 12 μm to 20 μm.

[0100] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0101] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0102] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0103] The secondary battery includes at least one battery cell. The secondary battery may include one or more battery cells.

[0104] In this application, unless otherwise specified, "battery cell" refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy, and further, generally speaking, at least includes a positive electrode sheet, a negative electrode sheet and an electrolyte. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0105] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 1 The secondary battery 1 is a square structure as an example.

[0106] In some of these embodiments, reference Figure 2 , the outer packaging may include a shell 11 and a cover plate 13. Among them, the shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the secondary battery 1 can be one or more, and those skilled in the art can select according to actual needs.

[0107] The secondary battery may be a battery module or a battery pack.

[0108] The battery module includes at least one battery cell. The number of battery cells contained in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0109] In the battery module, the plurality of battery cells may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells may be fixed by fasteners.

[0110] Optionally, the battery module may further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0111] In some of the embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select a suitable number according to the application and capacity of the battery pack.

[0112] The battery pack may include a battery box and a plurality of battery modules disposed in the battery box. The battery box includes an upper box body and a lower box body, and the upper box body can be covered on the lower box body to form a closed space for accommodating the battery modules. The plurality of battery modules can be arranged in the battery box in any manner.

[0113] In addition, the present application also provides an electrical device, which includes a secondary battery provided by the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, 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., but are not limited thereto.

[0114] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0115] Figure 3 The power consumption device 2 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module can be used.

[0116] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0117] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0118] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0119] The performance test method of the battery in each embodiment and comparative example is as follows:

[0120] (1) HF content:

[0121] The hydrofluoric acid content was analyzed by acid-base titration (SYA); the reference standard HG / T4067-2015 Determination of free acid content of lithium hexafluorophosphate electrolyte 5.10; in a dry environment, the free acid in the electrolyte was titrated with triethylamine standard solution to calculate the HF content:

[0122] HF(ppm)=(V2-V1) / 1000*C*20 / m*1000000=(V2-V1)*C / m*20000;

[0123] Where: C——concentration of SYA standard solution, 0.02mol / L;

[0124] V1——the volume reading of the burette before starting the titration, mL;

[0125] V2——The volume reading of the burette after adding the electrolyte sample and titrating to the endpoint, mL;

[0126] 20——molar molecular weight of HF, g / mol;

[0127] m——the amount of electrolyte weighed, g;

[0128] 20000——The coefficient for conversion to μg / g.

[0129] (2) Cycle capacity retention rate:

[0130] At 45°C, charge the battery cell at 1C constant current to 3.65V, then charge at 3.65V constant voltage to a cut-off current of 0.05C, and then discharge at 1C constant current to 2.5V. This is a charge and discharge cycle. The discharge capacity this time is recorded as the discharge capacity C1 of the first cycle of the lithium-ion battery cell. Repeat this cycle step for the same battery cell. After 600 cycles, record the discharge capacity C2 of the 600th cycle. The cycle capacity retention rate of the 600th cycle = C2 / C1*100%.

[0131] (3) Energy density:

[0132] At 25°C, the lithium ion batteries prepared in the examples and comparative examples were charged to 3.65V at a constant current of 0.5C, charged to a cut-off current of 0.05C at a constant voltage of 3.65V, and then fully discharged to 2.5V at a constant current of 0.5C. After three times of charge and discharge, the actual discharge energy E0 (Wh) at this time was recorded; under the same temperature condition, the lithium ion battery was weighed using an electronic balance, and the length, width and height of the lithium ion battery were measured using a micrometer to obtain the volume V (L) of the battery; the ratio of the actual discharge energy E0 of the lithium ion battery to the volume V of the lithium ion battery is the actual volume energy density of the lithium ion battery.

[0133] Example 1

[0134] 1) Preparation of positive electrode

[0135] The positive electrode active material (lithium iron phosphate, specific surface area 10.2m 2 / g, particle size Dv50 is 1.2μm), conductive carbon black SP and binder PVDF are dispersed in solvent NMP according to a weight ratio of 98%:1%:1% and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on both sides of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained, wherein the coating amount per unit area on both sides is 0.27g / 1540.25mm 2 .

[0136] 2) Preparation of negative electrode

[0137] The negative electrode active material (artificial graphite, specific surface area 1.3m 2 / g, particle size Dv50 is 10.1μm ), thickener sodium carboxymethyl cellulose, adhesive styrene butadiene rubber, conductive agent acetylene black, according to the mass ratio of 97%:1%:1%:1%, deionized water is added, and negative electrode slurry is obtained under the action of a vacuum mixer; the negative electrode slurry is evenly coated on both sides of the copper foil; the copper foil is dried at room temperature and then transferred to a 120℃ oven for drying for 1h, and then cold pressed and cut to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides is 0.17g / 1540.25mm 2 .

[0138] 3) Isolation film

[0139] A 12μm thick polypropylene isolation film was selected.

[0140] 4) Preparation of electrolyte

[0141] The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20%:20%:60%. In an argon atmosphere glove box with a water content of <10ppm, PST, TMSP, FEC, VC and fully dried lithium salt LiPF6 are dissolved in the organic solvent and mixed evenly to obtain an electrolyte. Among them, the concentration of the lithium salt is 1 mol / L, the mass concentration of PST is 5%, the mass concentration of TMSP is 0.2%, the mass concentration of FEC is 2.0%, and the mass concentration of VC is 3.5%.

[0142] 5) Preparation of batteries

[0143] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrodes to play an isolating role, and then wound into a square bare cell, loaded with aluminum plastic film, and then baked at 80°C to remove water, 10g of the corresponding non-aqueous electrolyte is injected, and the cell is sealed to prepare the cell. After the cell is placed, hot and cold pressed, formed, clamped, and divided into capacities, the finished battery is obtained. The formation process is: 45°C, 0.02C constant current charging for 600min. After formation, the concentration of lithium salt in the electrolyte is 1mol / L, the mass concentration of PST is 3.5%, the mass concentration of TMSP is 0.1%, the mass concentration of FEC is 0.3%, and the mass concentration of VC is 1.5%.

[0144] The battery preparation methods of Examples 2 to 4 are the same as those of Example 1, with the main difference being that different specific surface areas and particle sizes Dv50 of positive and negative electrode active materials are used. As shown in Table 1 below:

[0145] Table 1

[0146]

[0147] The battery preparation method of Example 5 is the same as that of Example 1, except that TMSP is not added to the electrolyte. As shown in Table 2 below:

[0148] Table 2

[0149]

[0150] The battery preparation method of Example 6 is the same as that of Example 1, with the main difference that VC is not added to the electrolyte, and the mass concentration of FEC is adjusted to 5.5% (1.5% after formation). As shown in Table 3 below:

[0151] Table 3

[0152]

[0153] The battery preparation method of Comparative Example 1 is the same as that of Example 1, with the main difference being that positive electrode active materials with different specific surface areas and particle sizes Dv50 are used. As shown in Table 4 below:

[0154] Table 4

[0155]

[0156] The battery preparation method of Comparative Example 2 is the same as that of Example 1, with the main difference being that negative electrode active materials with different specific surface areas and particle sizes Dv50 are used. As shown in Table 5 below:

[0157] Table 5

[0158]

[0159] By comparing Examples 1 to 6 with Comparative Examples 1 and 2, it can be seen that by controlling the specific surface area of ​​the positive electrode active material to ≤15 m 2 / g, and the specific surface area of ​​the negative electrode active material is ≤1.5m 2 / g, improving the battery's cycle capacity retention rate and giving the battery a better cycle life.

[0160] From the comparison between Examples 1 to 6, it can be seen that by reasonably controlling the range of specific surface areas of the positive and negative electrode active materials, a higher energy density can be obtained while the battery has a better cycle life.

[0161] By comparing Example 1 with Example 5, it can be seen that further adding TMSP as an additive can improve the cycle capacity retention rate of the battery.

[0162] By comparing Example 1 with Example 6, it can be seen that the synergistic use of a combination of a fluorine-containing negative electrode film-forming additive and a double bond-containing negative electrode film-forming additive as an additive can improve the cycle capacity retention rate of the battery.

[0163] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0164] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A lithium ion secondary battery, characterized in that: It contains positive electrode sheet, negative electrode sheet and electrolyte. The electrolyte includes a first additive, wherein the first additive includes 1,3-propylene sultone, and the mass concentration of the 1,3-propylene sultone in the electrolyte is 0.01% to 3.5%. The positive electrode sheet contains a positive electrode active material, and the specific surface area of ​​the positive electrode active material is less than or equal to 15 m 2 / g, The negative electrode plate comprises a negative electrode active material, and the specific surface area of ​​the negative electrode active material is ≤1.5m 2 / g.

2. The lithium ion secondary battery according to claim 1, characterized in that: The specific surface area of ​​the positive electrode active material is 8 m 2 / g~15m 2 / g.

3. The lithium ion secondary battery according to claim 1, characterized in that: The particle size Dv50 of the positive electrode active material is 0.5 μm to 2.5 μm.

4. The lithium-ion secondary battery according to claim 1, characterized in that: The specific surface area of ​​the negative electrode active material is 1 m 2 / g~1.5m 2 / g.

5. The lithium ion secondary battery according to claim 1, characterized in that: The particle size Dv50 of the negative electrode active material is 8 μm to 18 μm.

6. The lithium ion secondary battery according to any one of claims 1 to 5, characterized in that: The electrolyte further comprises a second additive, wherein the second additive comprises a silicon-containing acid-scavenging additive.

7. The lithium ion secondary battery according to claim 6, characterized in that: The second additive has one or more of the following characteristics: (1) In the electrolyte, the mass concentration of the second additive is 0.01% to 0.5%; (2) The second additive includes one or more of tris(trimethylsilyl)phosphate, silazane, N-trimethylsilyl imidazole and tris(trimethylsilyl)borate.

8. The lithium ion secondary battery according to any one of claims 1 to 5, characterized in that: The electrolyte further includes a third additive, wherein the third additive includes a combination of a fluorine-containing negative electrode film-forming additive and a double bond-containing negative electrode film-forming additive.

9. The lithium ion secondary battery according to claim 8, characterized in that: The third additive has one or more of the following characteristics: (1) The fluorine-containing negative electrode film-forming additive includes one or more of fluoroethylene carbonate and fluoroalkyl-substituted vinyl carbonate; (2) In the electrolyte, the mass concentration of the fluorine-containing negative electrode film-forming additive is 0.01% to 3%; (3) The negative electrode film-forming additive containing double bonds includes one or more of vinylene carbonate, alkyl-substituted vinylene carbonate and alkenyl-substituted vinylene carbonate; (4) In the electrolyte, the mass concentration of the negative electrode film-forming additive containing double bonds is 0.01%~3%.

10. The lithium ion secondary battery according to any one of claims 1 to 5, characterized in that: The positive electrode active material includes lithium iron phosphate.

11. The lithium ion secondary battery according to any one of claims 1 to 5, characterized in that: The negative electrode active material includes one or both of natural graphite and artificial graphite.

12. A battery cell, characterized in that: It contains positive electrode sheet, negative electrode sheet and electrolyte. The electrolyte includes a first additive, wherein the first additive includes 1,3-propylene sultone, and the mass concentration of the 1,3-propylene sultone in the electrolyte is 0.01% to 5%. The positive electrode sheet contains a positive electrode active material, and the specific surface area of ​​the positive electrode active material is less than or equal to 15 m 2 / g, The negative electrode plate comprises a negative electrode active material, and the specific surface area of ​​the negative electrode active material is ≤1.5m 2 / g.

13. The battery cell according to claim 12, characterized in that: The electrolyte further comprises a second additive, wherein the second additive comprises a silicon-containing acid-scavenging additive.

14. The battery cell according to claim 13, characterized in that: The second additive has one or more of the following characteristics: (1) In the electrolyte, the mass concentration of the second additive is 0.01% to 1%; (2) The second additive includes one or more of tris(trimethylsilyl)phosphate, silazane, N-trimethylsilyl imidazole and tris(trimethylsilyl)borate.

15. The battery cell according to any one of claims 12 to 14, characterized in that: The electrolyte further includes a third additive, wherein the third additive includes a combination of a fluorine-containing negative electrode film-forming additive and a double bond-containing negative electrode film-forming additive.

16. The battery cell according to claim 15, characterized in that: The third additive has one or more of the following characteristics: (1) The fluorine-containing negative electrode film-forming additive includes one or more of fluoroethylene carbonate and fluoroalkyl-substituted vinyl carbonate; (2) In the electrolyte, the mass concentration of the fluorine-containing negative electrode film-forming additive is 0.01% to 5%; (3) The negative electrode film-forming additive containing double bonds includes one or more of vinylene carbonate, alkyl-substituted vinylene carbonate and alkenyl-substituted vinylene carbonate; (4) In the electrolyte, the mass concentration of the negative electrode film-forming additive containing double bonds is 0.01%~5%.

17. An electrical device, characterized in that: A lithium ion secondary battery comprising any one of claims 1 to 11.

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