Electrolyte, battery and electric device

Abstract

The invention provides an electrolyte, a battery and an electric device. The electrolyte includes a first additive represented by formula (I); wherein R is selected from one or more of halogen and MO I; m is selected from alkali metal. The electrolyte provided by the invention can inhibit the corrosion of HF to a cathode and an anode SEI membrane, reduce the redox reaction between the electrolyte and the anode or the cathode, reduce the consumption of active lithium, inhibit the solvent decomposition in the electrolyte, reduce the gas production rate of solvent decomposition, improve the cycle and storage performance of a secondary battery, and reduce the volume expansion and impedance of a battery cell. # imgabs0 #

Description

Electrolyte, battery and electrical device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrolyte, a battery, and an electrical device. Background Art

[0002] In recent years, the application of secondary batteries has become increasingly widespread. They are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As secondary batteries have achieved great development, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0003] The fluorine-containing electrolyte salts in the electrolyte used in the battery hydrolyze at high temperatures to produce HF. HF can easily cause the SEI film of the electrode plate to be corroded, resulting in increased consumption of active lithium, increased impedance and volume expansion of the battery cell, and decreased cycle performance and storage performance of the battery. Therefore, there is an urgent need to solve the above problems.

[0004] Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte, a battery and an electrical device; the use of the electrolyte of the present application can reduce the corrosion of HF generated by the hydrolysis of fluorine-containing electrolyte salts on the SEI film of the electrode pole piece, reduce the consumption of active lithium, improve the cycle performance and storage performance of the secondary battery, and reduce the impedance and volume expansion of the battery cell.

[0006] In order to achieve the above-mentioned object, the present application provides an electrolyte in a first aspect, comprising a first additive represented by formula (I);

[0007]

[0008] in,

[0009] R is selected from one or more of halogen and MO-; M is selected from alkali metal.

[0010] The first additive in the electrolyte of the present application can inhibit the corrosion of the cathode SEI film and the anode SEI film by HF generated by the hydrolysis of the fluorine-containing electrolyte salt, reduce the redox reaction between the electrolyte and the anode or cathode, thereby reducing the consumption of active lithium and improving the cycle performance of the secondary battery; the first additive can also reduce the HF-induced solvent decomposition in the electrolyte and reduce the amount of gas generated by the solvent decomposition, thereby reducing the volume expansion and impedance of the battery cell and improving the storage performance of the secondary battery.

[0011] In any embodiment, R is selected from one or more of F and MO-; and / or, M is selected from one or more of lithium, sodium, potassium, rubidium and cesium;

[0012] Optionally, M is selected from one or more of lithium, sodium and potassium;

[0013] More optionally, M is lithium.

[0014] In any embodiment, the first additive is selected from one or more of lithium sulfamate, sulfamate fluoride, sodium sulfamate, and potassium sulfamate;

[0015] Optionally, the first additive is selected from one or more of lithium sulfamate and aminosulfonyl fluoride.

[0016] Therefore, the first additive can further inhibit the corrosion of HF on the anode SEI film or the cathode SEI film, reduce the consumption of active lithium, further improve the cycle performance of the secondary battery, further reduce the volume expansion and impedance of the battery cell, and further improve the storage performance of the secondary battery.

[0017] In any embodiment, the mass content of the first additive in the electrolyte is less than or equal to 3.5%, optionally 10 ppm to 3.5%, more optionally 10 ppm to 3%, further optionally 500 ppm to 1%, further optionally 0.1% to 1%.

[0018] The first additive within the above content range can further improve the cycle performance and storage performance of the secondary battery and further reduce the impedance of the battery cell.

[0019] In any embodiment, the electrolyte further comprises a second additive represented by formula (II) or formula (III),

[0020]

[0021]

[0022] in,

[0023] E in formula (II) and formula (III) is independently selected from one or more of phosphorus and boron;

[0024] G in formula (II) and formula (III) is each independently selected from halogen;

[0025] and,

[0026] When E is phosphorus, x is 2 and y is 2;

[0027] When E in formula (II) is boron, x is 4 and y is 0, or x is 2 and y is 1;

[0028] When E in formula (III) is boron, x is 4 and y is 0.

[0029] The second additive is used together with the first additive to further reduce the impedance of the battery cell, further reduce the expansion rate of the battery cell, and further improve the cycle performance and storage performance of the secondary battery.

[0030] In any embodiment, G in formula (II) and formula (III) is each independently F.

[0031] In any embodiment, the second additive is selected from one or more of lithium difluorophosphate, lithium difluorobisoxalatophosphate, lithium tetrafluoroborate, and lithium difluorooxalatoborate;

[0032] Optionally, the second additive is selected from one or more of lithium difluorophosphate, lithium tetrafluoroborate and lithium difluorooxalatoborate.

[0033] The above-mentioned second additive is used in combination with the first additive to further reduce the impedance and volume expansion of the battery cell and improve the cycle performance and storage performance of the secondary battery.

[0034] In any embodiment, the mass content of the second additive in the electrolyte is less than or equal to 2.3%, optionally 100 ppm to 2.3%, more optionally 100 ppm to 2%, further optionally 0.1% to 1%.

[0035] The content of the second additive within the above range is beneficial to further improve the cycle performance and storage performance of the secondary battery.

[0036] In any embodiment, the ratio of the mass content of the second additive in the electrolyte to the mass content of the first additive in the electrolyte is 0.1 to 500, optionally 0.5 to 12, and more optionally 0.5 to 10. Thus, a battery with good overall performance can be obtained.

[0037] In any embodiment, it also contains an electrolyte salt, which is one or more selected from LiPF6, lithium bis(fluorosulfonyl)imide, lithium fluorosulfonate, lithium fluorosulfonyl(trifluoromethylsulfonyl)imide, and lithium bis(pentafluoroethylsulfonyl)imide, and can be optionally one or more selected from LiPF6 and lithium bis(fluorosulfonyl)imide.

[0038] The first additive and the optional second additive have a more obvious improvement effect on the electrolyte system containing the above electrolyte salt, can further improve the cycle performance and storage performance of the secondary battery, and further reduce the volume expansion and impedance of the battery cell.

[0039] The second aspect of the present application further provides a battery comprising the electrolyte of the first aspect of the present application.

[0040] Therefore, the first additive in the electrolyte of the present application can inhibit the corrosion of the cathode SEI film and the anode SEI film by HF generated by the hydrolysis of fluorine-containing electrolyte salts, reduce the redox reaction between the electrolyte and the anode or cathode, thereby reducing the consumption of active lithium and improving the cycle performance of the secondary battery; the first additive can also reduce the solvent decomposition in the electrolyte induced by HF, reduce the amount of gas generated by the solvent decomposition, thereby reducing the volume expansion and impedance of the battery cell, and improving the storage performance of the secondary battery.

[0041] A third aspect of the present application provides an electrical device comprising the battery according to the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0043] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

[0044] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0045] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0046] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0047] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0048] Description of reference numerals:

[0049] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0050] Below, embodiments of the electrolyte, battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actual identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0051] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0053] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0054] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0055] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may indicate that other components not listed may also be included or that only the listed components are included.

[0056] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0057] Unless otherwise specified, in this application, the term "halogen" is a general term for elements in Group VIIA of the periodic table, including fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), etc.

[0058] Unless otherwise specified, in this application, the term "alkali metal" refers to metal elements in Group IA of the periodic table except hydrogen, including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), etc.

[0059] [Secondary battery]

[0060] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged to activate the active materials after discharge and continue to be used.

[0061] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery's charge and discharge process, active ions (such as lithium ions) are embedded and released back and forth between the positive and negative electrode sheets. The separator is set between the positive and negative electrode sheets, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte between the positive and negative electrode sheets mainly plays the role of conducting active ions.

[0062] [Electrolytes]

[0063] One embodiment of the present application provides an electrolyte comprising a first additive represented by formula (I);

[0064]

[0065] in,

[0066] R is selected from one or more of halogen and MO-; M is selected from alkali metal.

[0067] HF generated by hydrolysis of fluorine-containing electrolyte salts in the electrolyte will corrode the anode SEI film and the cathode SEI film. After the SEI film is corroded, the exposed anode material or cathode material is prone to redox reaction with the electrolyte, resulting in excessive consumption of active lithium and deteriorating the cycle performance and storage performance of the secondary battery. In addition, HF will also induce the decomposition of the solvent in the electrolyte to produce gas, resulting in volume expansion and increased impedance of the battery cell, and a decrease in the high-temperature storage performance of the secondary battery.

[0068] The amino group in the first additive in the electrolyte of the present application can combine with HF produced by hydrolysis, and the sulfonic acid group can also participate in film formation, thereby inhibiting the corrosion of HF on the anode SEI film or the cathode SEI film, inhibiting the redox reaction between the electrolyte and the anode material or the cathode material, reducing the consumption of active lithium, and improving the cycle performance and storage performance of the secondary battery; moreover, the combination of the amino group in the first additive and HF can inhibit the decomposition and gas production of the solvent, reduce the volume expansion and impedance of the battery cell, and further improve the high-temperature storage performance of the secondary battery.

[0069] In some embodiments, R is selected from one or more of F and MO-; and / or, M is selected from one or more of lithium, sodium, potassium, rubidium and cesium;

[0070] Optionally, M is selected from one or more of lithium, sodium and potassium;

[0071] More optionally, M is lithium.

[0072] In some embodiments, the first additive is selected from one or more of lithium sulfamate, sulfamate fluoride, sodium sulfamate, and potassium sulfamate;

[0073] Optionally, the first additive is selected from one or more of lithium sulfamate and aminosulfonyl fluoride.

[0074] The first additive can further inhibit HF from corroding the anode SEI film or cathode SEI film, reduce the consumption of active lithium, further improve the cycle performance of the secondary battery, further reduce the volume expansion and impedance of the battery cell, and further improve the storage performance of the secondary battery.

[0075] In the present application, lithium sulfamate, sulfamate fluoride, sodium sulfamate and potassium sulfamate are respectively represented by the following structures:

[0076]

[0077] In some embodiments, the mass content of the first additive in the electrolyte is less than or equal to 3.5%, and can be optionally 10 ppm to 3.5%, more optionally 10 ppm to 3%, further optionally 500 ppm to 1%, and further optionally 0.1% to 1%, for example, a range consisting of 10 ppm, 500 ppm, 0.1%, 0.5%, 1%, 3%, 3.5% and any of the above values.

[0078] Therefore, the first additive within the above content range can further improve the cycle performance and storage performance of the secondary battery and further reduce the impedance of the battery cell.

[0079] In some embodiments, the electrolyte further comprises a second additive represented by formula (II) or formula (III),

[0080]

[0081] in,

[0082] E in formula (II) and formula (III) is independently selected from one or more of phosphorus and boron;

[0083] G in formula (II) and formula (III) is each independently selected from halogen;

[0084] and,

[0085] When E is phosphorus, x is 2 and y is 2;

[0086] When E in formula (II) is boron, x is 4 and y is 0, or x is 2 and y is 1;

[0087] When E in formula (III) is boron, x is 4 and y is 0.

[0088] Because the first additive readily deposits byproducts on the anode surface during film formation, increasing the impedance of the anode interface and the cell impedance, the second additive preferentially forms a film at the anode interface compared to the first additive, thereby reducing the impact of the first additive's byproducts on the anode interface impedance, further reducing the cell impedance and cell expansion rate, and improving the secondary battery's cycling and storage performance.

[0089] In any embodiment, G in formula (II) and formula (III) is each independently F.

[0090] In some embodiments, the second additive is selected from one or more of lithium difluorophosphate, lithium difluorobisoxalatophosphate, lithium tetrafluoroborate, and lithium difluorooxalatoborate;

[0091] Optionally, the second additive is selected from one or more of lithium difluorophosphate, lithium tetrafluoroborate and lithium difluorooxalatoborate.

[0092] The second additive is used together with the first additive to further reduce the impedance of the battery cell, further reduce the expansion rate of the battery cell, and further improve the cycle performance and storage performance of the secondary battery.

[0093] In the present application, lithium difluorophosphate, lithium difluorobisoxalatophosphate, lithium tetrafluoroborate and lithium difluorooxalatoborate are respectively represented by the following structures:

[0094] Li + [BF4] - ,

[0095] In some embodiments, the mass content of the second additive in the electrolyte is less than or equal to 2.3%, and can be optionally 100 ppm to 2.3%, more optionally 100 ppm to 2%, and further optionally 0.1% to 1%, for example, a range consisting of 100 ppm, 0.1%, 0.3%, 0.5%, 1%, 1.2%, 2%, 2.3% and any of the above values.

[0096] The content of the second additive within the above range is beneficial to further improve the cycle performance and storage performance of the secondary battery.

[0097] In some embodiments, the ratio of the mass content of the second additive in the electrolyte to the mass content of the first additive in the electrolyte is 0.1 to 500, optionally 0.5 to 12, and more preferably 0.5 to 10, such as 0.1, 0.2, 0.5, 1, 3, 4, 4.6, 5, 10, 12, 500, and any range thereof. Thus, a battery with good overall performance can be obtained.

[0098] The electrolyte conducts ions between the positive and negative electrodes. For example, the electrolyte can be liquid, gel, or solid.

[0099] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0100] In some embodiments, the electrolyte salt is one or more selected from LiPF6, lithium bis(fluorosulfonyl)imide, lithium fluorosulfonate, lithium fluorosulfonyl(trifluoromethylsulfonyl)imide, and lithium bis(pentafluoroethylsulfonyl)imide, and can be selected from one or two of LiPF6 and lithium bis(fluorosulfonyl)imide, and more preferably LiPF6.

[0101] The first additive and the optional second additive have a more obvious improvement effect on the electrolyte system containing the above electrolyte salt, can further improve the cycle performance and storage performance of the secondary battery, and further reduce the volume expansion and impedance of the battery cell.

[0102] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0103] In some embodiments, the electrolyte may optionally include other additives, such as additives that can improve the overcharge performance of the secondary battery, additives that can improve the high or low temperature performance of the secondary battery, and the like.

[0104] In some embodiments, the mass content of water in the electrolyte does not exceed 50 ppm, and optionally does not exceed 20 ppm.

[0105] In some embodiments, the conductivity of the electrolyte is selected from the range of 7 mS / cm to 15 mS / cm.

[0106] In some embodiments, the low-temperature freezing point of the electrolyte at one standard atmospheric pressure is selected from the range of -80°C to -20°C.

[0107] [Positive electrode]

[0108] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0109] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0110] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0111] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0112] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0113] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0114] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0115] [Negative electrode]

[0116] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0117] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0118] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0119] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0120] In some embodiments, the negative electrode film layer may further include a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0121] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0122] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0123] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0124] [Isolation film]

[0125] 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 and mechanical stability can be selected.

[0126] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0127] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0128] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0129] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0130] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0131] In some embodiments, referring to FIG2 , the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0132] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0133] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0134] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0135] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0136] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0137] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0138] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0139] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0140] [Example]

[0141] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0142] Example 1

[0143] (1) Preparation of electrolyte: In an argon-filled glove box (water content <10 ppm, oxygen content <1 ppm), appropriate amounts of the first additive, lithium sulfamate, and the second additive, lithium difluorophosphate, were added to a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC:EMC=3:7 W% / W%). After mixing evenly, LiPF6 was slowly added. After the lithium salt was completely dissolved, an electrolyte was obtained, wherein the mass content of lithium sulfamate was 10 ppm, the mass content of lithium difluorophosphate was 0.5%, the molar concentration of LiPF6 was 1 M, and the mass content of water in the electrolyte was ≤20 ppm.

[0144] (2) Preparation of positive electrode sheet: LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP). The solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.5 Co 0.2 Mn 0.3 The mass ratio of O2, Super P, and PVDF is 8:1:1. The positive electrode slurry is coated on the current collector aluminum foil and dried at 85°C before cold pressing. After trimming, cutting, and slitting, it is dried under vacuum conditions at 85°C for 4 hours to obtain the positive electrode sheet.

[0145] (3) Preparation of negative electrode sheet: Graphite, the negative electrode active material, is mixed evenly with the conductive agent Super P, the thickener CMC, and the binder styrene butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. The solid content in the negative electrode slurry is 30wt%, and the mass ratio of graphite, Super P, CMC, and the binder styrene butadiene rubber (SBR) in the solid components is 80:15:3:2. The negative electrode slurry is coated on the current collector copper foil and dried at 85°C. It is then cold pressed, trimmed, cut into pieces, and slit, and then dried under vacuum conditions at 120°C for 12 hours to obtain the negative electrode sheet.

[0146] (4) Isolation film: 16 μm polyethylene film (PE) is used.

[0147] (5) Preparation of secondary batteries: The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to isolate the positive and negative electrodes, and then wound to obtain a bare cell. The tabs are welded and the bare cell is placed in an outer package. The above-prepared electrolyte is injected into the dried cell, and the cell is packaged, allowed to stand, formed, shaped, and capacity tested to complete the preparation of the secondary battery (the thickness of the soft-pack lithium-ion battery is 4.0 mm, the width is 60 mm, and the length is 140 mm).

[0148] The secondary battery preparation methods of Examples 2-19 and Comparative Examples 1-2 are similar to those of Example 1. The different parameters are detailed in Table 1. The rest are the same as those of Example 1.

[0149] Table 1: Parameters of Examples 1-19 and Comparative Examples 1-2

[0150]

[0151]

[0152] Battery Test

[0153] (1) Cycle performance test of secondary batteries

[0154] The ambient temperature was adjusted to 25°C. The secondary battery was charged at a constant current of 1C to 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05C, left to stand for 10 minutes, and then discharged at 1C to 2.8V. The discharge capacity C0 at this time was recorded. 300 cycles were performed according to the above charge and discharge process. The discharge capacity at the 300th cycle was C1. The cycle capacity retention rate of the secondary battery was calculated according to the following formula;

[0155] Cycle capacity retention rate of secondary battery = 100% × C0 / C1

[0156] (2) High-temperature storage gas generation test of secondary batteries

[0157] At 25°C, the secondary battery is charged at a constant current of 1C to 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05C. The volume of the battery cell is then measured using the water displacement method and recorded as V1. The moisture on the surface of the battery cell is wiped dry, and the secondary battery is placed in a 70°C constant temperature box for 10 days (during which the battery is not in use). After removal, the temperature is lowered to 25°C, and the volume of the battery cell is measured again using the water displacement method and recorded as V2. The volume expansion rate of the battery cell is calculated according to the following formula;

[0158] Cell volume expansion rate = 100% × (V2-V1) / V1

[0159] (3) High temperature storage life test of secondary batteries

[0160] At 25°C, the secondary battery is charged to 4.25V at a constant current of 1C, then charged to a current of 0.05C at a constant voltage of 4.25V, allowed to stand for 10min, and then discharged to 2.8V at 1C. The discharge capacity D0 at this time is recorded. The secondary battery is placed in a 60°C constant temperature box for 60 days (the battery does not work during this period). After being taken out, the temperature is lowered to 25°C. The secondary battery is discharged to 2.8V at a constant current of 1C, then charged to 4.25V at a constant current of 1C, then charged to 0.05C at a constant voltage of 4.25V, allowed to stand for 10min, and then discharged to 2.8V at a constant current of 1C. The discharge capacity D1 is recorded. The high temperature storage capacity retention rate of the secondary battery is calculated according to the following formula;

[0161] High-temperature storage capacity retention rate of secondary battery = 100% × D1 / D0

[0162] (4) Impedance test

[0163] At 25°C, the secondary battery was allowed to rest for 10 minutes, charged to 4.25V at 1C, then charged to 0.05C at a constant voltage of 4.25V, allowed to rest for 30 minutes, discharged at 1C for 30 minutes, allowed to rest for 60 minutes, and the voltage V1 at the end of the rest period was recorded. Subsequently, the battery was discharged at 4C for 30 seconds, and the voltage V2 at the end of the discharge period was recorded. The impedance of the battery at 50% SOC was calculated according to the following formula: I = 4C;

[0164] R=(V1-V2) / I

[0165] (5) Determination of electrolyte conductivity

[0166] The conductivity test of the electrolyte at room temperature (25°C) was carried out in accordance with HG-T 4067-2015.

[0167] Measurement results: The electrical conductivities of the electrolytes of Examples 1-19 are in the range of 7 mS / cm to 15 mS / cm.

[0168] (6) Determination of low-temperature freezing point of electrolyte

[0169] After the battery cell is filled with liquid, it is sealed and clamped with an expansion force test sensor. It is then placed in a high and low temperature chamber and gradually cooled. The changes in the battery cell's expansion force are simultaneously monitored. When the electrolyte solidifies, the battery cell's expansion force will increase sharply. The temperature corresponding to the inflection point of the expansion force growth is recorded. This temperature is the solidification point of the electrolyte.

[0170] Measurement results: The low-temperature freezing point of the electrolyte of Example 1-19 at a standard atmospheric pressure is in the range of -80°C to -20°C.

[0171] The results of items (1) to (4) above are shown in Table 2.

[0172] Table 2: Secondary battery performance test results of Examples 1-19 and Comparative Examples 1-2

[0173] Cycle capacity retention rate Cell volume expansion rate High temperature storage capacity retention rate Impedance (mohm) Example 1 92.30% 18% 90.10% 160 Example 2 97.10% 7.80% 95.30% 53 Example 3 98.80% 3.60% 96.60% 57 Example 4 97.50% 3.00% 95.60% 62 Example 5 95.80% 1.20% 94.30% 136 Example 6 95.00% 9.20% 93.70% 140 Example 7 97.00% 8.40% 95.70% 86 Example 8 97.50% 5.30% 96.40% 71 Example 9 97.80% 5.00% 96.50% 42 Example 10 93.10% 15.00% 91.20 %200 Example 11 97.30% 5.50% 96.30% 73 Example 12 98.50% 4.00% 96.20% 64 Example 13 96.40% 3.70% 95.00% 78 Example 14 99.10% 3.00% 98.30% 53 Example 15 88.30% 1.00% 86.30% 220 Example 16 90.30% 4.00% 88.70% 18 Example 17 96.60% 8.30% 94.50% 51 Example 18 97.20% 7.30% 96.00% 80 Example 19 96.00% 9% 94.20% 56 Comparative Example 1 8 0.30% 25% 80.00% 180 Comparative Example 2 8 4.20% 23% 82.20% 190

[0174] From Table 1-2 we can see that:

[0175] Compared with Comparative Examples 1-2, the batteries made with the electrolytes of Examples 1-19 of the present application have a higher cycle capacity retention rate, a lower cell volume expansion rate, and a higher high-temperature storage capacity retention rate;

[0176] Compared with Example 15, the mass content of the first additive in the electrolyte in Examples 1-5, 8, 11, 14, and 17 of the present application is 10ppm-3%, and the batteries prepared therefrom have a higher cycle capacity retention rate, a higher high-temperature storage capacity retention rate, and a lower cell impedance;

[0177] Compared with Example 10, Examples 2, 6-9, 11, and 18-19 of the present application simultaneously use the first additive and the second additive, and the resulting battery cells have lower impedance, lower battery cell volume expansion rate, and higher battery cycle capacity retention rate and high-temperature storage capacity retention rate;

[0178] Compared with Example 16, the mass content of the second additive in the electrolyte in Example 12 of the present application is 100ppm-2%, and the cycle capacity retention rate and high-temperature storage capacity retention rate of the battery prepared therefrom are higher;

[0179] Compared with Examples 1, 5, 6, and 15, the ratio b / a of the mass content of the second additive to the mass content of the first additive in Examples 2-4, 7-9, 11, 13, 14, and 17-18 of the present application is in the range of 0.5 to 10, and the batteries prepared therefrom have a higher cycle capacity retention rate, a higher high-temperature storage capacity retention rate, and a lower cell impedance.

[0180] The above description shows that the battery made of the electrolyte of the present application has a higher cycle capacity retention rate, a lower cell volume expansion rate, a higher high-temperature storage capacity retention rate, and a lower cell impedance.

[0181] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte comprising a first additive represented by formula (I); in, The R is selected from one or more of halogen and MO-; the M is selected from alkali metals.

2. The electrolyte according to claim 1, wherein The R is selected from one or more of F and MO-; and / or, the M is selected from one or more of lithium, sodium, potassium, rubidium and cesium; Optionally, the M is selected from one or more of lithium, sodium and potassium; More optionally, said M is lithium.

3. The electrolyte according to claim 1 or 2, wherein The first additive is selected from one or more of lithium sulfamate, sulfamoyl fluoride, sodium sulfamate and potassium sulfamate; Optionally, the first additive is selected from one or more of lithium sulfamate and aminosulfonyl fluoride.

4. The electrolyte according to any one of claims 1 to 3, wherein The mass content of the first additive in the electrolyte is less than or equal to 3.5%, and may be 10 ppm to 3.5%, and may be 10 ppm to 3%, and may be 500 ppm to 1%, and may be 0.1% to 1%.

5. The electrolyte according to any one of claims 1 to 4, further comprising a second additive represented by formula (II) or formula (III), in, The E in formula (II) and formula (III) is independently selected from one or more of phosphorus and boron; The G in formula (II) and formula (III) are each independently selected from halogen; and, When E is phosphorus, x is 2 and y is 2; When E in formula (II) is boron, x is 4 and y is 0, or x is 2 and y is 1; When the E in formula (III) is boron, the x is 4 and the y is 0.

6. The electrolyte according to claim 5, wherein The G in formula (II) and formula (III) is each independently F.

7. The electrolyte according to claim 5 or 6, wherein The second additive is selected from one or more of lithium difluorophosphate, lithium difluorobisoxalatephosphate, lithium tetrafluoroborate and lithium difluorooxalateborate; Optionally, the second additive is selected from one or more of lithium difluorophosphate, lithium tetrafluoroborate and lithium difluorooxalatoborate.

8. The electrolyte according to any one of claims 5 to 7, wherein The mass content of the second additive in the electrolyte is less than or equal to 2.3%, and may be 100 ppm to 2.3%, and may be 100 ppm to 2%, and may be 0.1% to 1%.

9. The electrolyte according to any one of claims 5 to 8, wherein The ratio of the mass content of the second additive in the electrolyte to the mass content of the first additive in the electrolyte is 0.1 to 500, optionally 0.5 to 12, and more optionally 0.5 to 10.

10. The electrolyte according to any one of claims 1 to 9, further comprising an electrolyte salt, wherein the electrolyte salt is one or more selected from LiPF6, lithium bis(fluorosulfonyl)imide, lithium fluorosulfonate, lithium fluorosulfonyl (trifluoromethylsulfonyl)imide, and lithium bis(pentafluoroethylsulfonyl)imide, and may be one or more selected from LiPF6 and lithium bis(fluorosulfonyl)imide.

11. A battery comprising the electrolyte according to any one of claims 1 to 10.

12. An electrical device comprising the battery according to claim 11.

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