Electrolyte, secondary battery, and electric device
By using six-membered cyclic olefins and nitrogen heterocyclic additives in lithium-ion batteries, a stable passivation film is formed, which solves the problems of excessive SEI film impedance and electrolyte oxidative decomposition, and improves the cycle stability and charge transfer rate of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUNWODA MOBILITY ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2023-05-30
- Publication Date
- 2026-06-16
Smart Images
Figure QLYQS_1 
Figure QLYQS_2 
Figure QLYQS_3
Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, specifically to an electrolyte, a secondary battery, and an electrical device. Background Technology
[0002] The rapid development of global industrialization has led to the depletion of traditional fossil fuels and severe environmental pollution, forcing humanity to seek a transformation towards new energy sources. Today, lithium-ion batteries, characterized by long cycle life, high energy density, short charging time, small size, light weight, and no memory effect, occupy an important position in energy storage and power battery fields. However, range anxiety remains, placing higher demands on the energy density of lithium-ion batteries.
[0003] During the first charge and discharge of a secondary battery, the electrode material and the electrolyte react at the solid-liquid interface to form a passivation layer, namely the SEI film, covering the electrode surface. If the impedance of the SEI film is too high, it will intensify the initial polarization of the battery. At this time, it is easy to cause metallic lithium to be deposited on the surface of the negative electrode, which consumes the active lithium in the battery and significantly reduces the reversible capacity of the battery. In addition, the deposited metallic lithium may also puncture the separator, thereby affecting the safety performance of the battery.
[0004] Furthermore, in ternary cathode materials, in order to obtain higher energy density and reduce costs, the Ni content is continuously increased. With the increase of Ni content, under high potential or high temperature conditions, lattice oxygen is easily released on the cathode surface. At the same time, the strong catalytic properties of tetravalent Ni ions cause the electrolyte to undergo oxidative decomposition and generate a large amount of gas. Accompanied by a large amount of high-resistivity decomposition products accumulating on the cathode surface, the impedance increases. This seriously damages the cycle stability of lithium-ion batteries and brings safety hazards.
[0005] Therefore, how to reduce impedance has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0006] The purpose of this application is to overcome the shortcomings of the existing technology and provide an electrolyte, a secondary battery and an electrical device. The electrolyte can form a stable passivation film on the surface of the positive and negative electrodes, inhibit electrolyte decomposition, help improve its ionic conductivity, suppress the increase of interfacial impedance, and effectively improve cycle stability.
[0007] To achieve the above objectives, in a first aspect of this application, an electrolyte is provided, comprising an additive, said additive comprising a first additive, the first additive comprising at least one of compounds with the structure shown in Formula I;
[0008]
[0009] R1 is selected from substituted or unsubstituted C1-C.10 Alkyl, substituted or unsubstituted C1-C 10 Alkoxy, substituted or unsubstituted C6-C 26 At least one of aryl, nitrile, cyanate, isocyanate, amide, and halogen;
[0010] The substituents are selected from at least one of C1-C5 alkyl, C1-C5 alkoxy, halogen, cyano, carboxyl, sulfonic acid, and sulfonyl groups.
[0011] As a preferred embodiment of this application, the C6-C 26 The aryl group is selected from one of phenyl, benzyl, biphenyl, p-tolyl, o-tolyl, and m-tolyl.
[0012] In a preferred embodiment of this application, the halogen is selected from at least one of F, Cl, and Br.
[0013] In a preferred embodiment of this application, R1 is selected from at least one of phenyl, halogen-substituted phenyl, C1-C5 alkyl-substituted phenyl, and C1-C5 alkoxy-substituted phenyl.
[0014] In a preferred embodiment of this application, the first additive comprises at least one of the following compounds:
[0015]
[0016] In a preferred embodiment of this application, the additive further includes a second additive, the second additive comprising at least one of the compounds with the structure shown in Formula II:
[0017]
[0018] R2 is selected from halogens;
[0019] The halogen includes at least one of F, Cl, and Br.
[0020] In a preferred embodiment of this application, the second additive comprises a compound with the structure shown in Formula III:
[0021]
[0022] As a preferred embodiment of this application, the mass ratio of the first additive to the second additive is (3-10):(2-7).
[0023] As a preferred embodiment of this application, based on the total mass of the electrolyte, the sum of the contents of the first additive and the second additive accounts for 0.1% to 5% of the total mass of the electrolyte.
[0024] In a second aspect, this application provides a secondary battery, including a positive electrode, a negative electrode, a separator, and the electrolyte described above.
[0025] In a third aspect, this application provides an electrical device including the aforementioned secondary battery.
[0026] The beneficial effects of this application are as follows: The first additive with the structure shown in Formula I in the electrolyte additive of this application contains a six-membered cyclic olefin, multiple unsaturated double bonds, and a nitrogen heterocycle containing sulfur in its molecular structure. The six-membered cyclic olefin structure has a certain steric hindrance effect, which can improve its dispersion in the electrolyte, making it uniformly dispersed in the electrolyte and avoiding agglomeration. The unsaturated double bonds (C=S and C=N) are beneficial for its adsorption on the electrode surface. At the same time, the presence of unsaturated double bonds is beneficial for the regulation of SEI film composition during the formation stage, which can improve ion mobility. It can reduce the oxidative decomposition of electrolyte, significantly reduce and lower the gas production and heat of the battery. Among them, the decomposition of nitrogen heterocycles containing sulfur on the electrode surface can effectively regulate the SEI film composition, increase the content of inorganic salts in the SEI film, and reduce the thickness of the SEI film. The entry of nitrogen and sulfur atoms into the interface film helps to improve its ion conductivity, and also helps to form stable passivation films containing nitrogen heteroatoms on the positive and negative electrode surfaces, respectively, inhibiting electrolyte decomposition, inhibiting the increase of interface impedance, and improving the lithium ion permeability in the passivation film. In addition, the increase of inorganic layer can also reduce the risk of electrode leakage, thereby improving cycle stability. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0028] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.
[0029] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.
[0030] In this application, there are no particular restrictions on the specific dispersion and mixing methods.
[0031] Unless otherwise specified, all reagents or instruments used in this application are commercially available products.
[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0033] To address the problems in existing technologies, such as the oxidation and decomposition of the electrolyte producing a large amount of gas, which increases surface impedance and affects battery cycle stability, as well as the lithium plating problem at the negative electrode.
[0034] This application provides an electrolyte including an additive, the additive including a first additive, the first additive including at least one of the compounds with the structure shown in Formula I;
[0035]
[0036] R1 is selected from substituted or unsubstituted C1-C. 10 Alkyl, substituted or unsubstituted C1-C 10 Alkoxy, substituted or unsubstituted C6-C 26 At least one of aryl, nitrile, cyanate, isocyanate, amide, and halogen;
[0037] The substituent is selected from at least one of C1-C5 alkyl, C2-C5 unsaturated alkyl, C1-C5 alkoxy, halogen, cyano, carboxyl, sulfonic acid, and sulfonyl groups.
[0038] The first additive of Formula I of this application contains a six-membered cyclic olefin, multiple unsaturated double bonds, and a nitrogen heterocycle containing sulfur in its molecular structure. The six-membered cyclic olefin structure has a certain steric hindrance effect, which can improve its dispersion in the electrolyte, ensuring uniform dispersion and preventing aggregation. The unsaturated double bonds (C=S and C=N) facilitate its adsorption on the electrode surface. Furthermore, the presence of unsaturated double bonds allows for the regulation of the SEI film composition during the formation stage, improving ion mobility and reducing electrolyte oxidation. The decomposition phenomenon significantly reduces and lowers the gas production and heat generation of the battery. Among them, the decomposition of nitrogen heterocycles containing sulfur on the electrode surface can effectively regulate the composition of the SEI film, increase the content of inorganic salts in the SEI film, and reduce the thickness of the SEI film. The entry of nitrogen and sulfur atoms into the interface film helps to improve its ion conductivity, and also helps to form stable passivation films containing nitrogen heteroatoms on the positive and negative electrode surfaces, respectively, inhibiting electrolyte decomposition, inhibiting the increase of interface impedance, and improving the lithium ion permeability in the passivation film. In addition, the increase of inorganic layer can also reduce the risk of electrode leakage, thereby improving cycle stability.
[0039] In Formula I above, the substituents are as follows:
[0040] C1-C 10 Alkyl (alkyl with 1 to 10 carbon atoms) refers to a free radical of a saturated or unsaturated aliphatic group, including straight-chain alkyl, straight-chain alkenyl, straight-chain alkynyl, branched-chain alkyl, branched-chain alkenyl, branched-chain alkynyl, cycloalkyl, cycloalkenyl, and cycloalkynyl.
[0041] For example, C1-C 10 Alkyl groups include C1-C 10 Saturated alkyl, C2-C 10 alkenyl and C2-C 10 The alkynyl group, more preferably, is a straight-chain alkyl group with 1 to 6 carbon atoms, a branched alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 3 to 6 carbon atoms, a straight-chain alkenyl group with 2 to 6 carbon atoms, a branched alkenyl group with 1 to 6 carbon atoms, or a cyclic alkenyl group with 3 to 6 carbon atoms. Examples of alkyl groups include: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, and cyclohexyl; examples of alkenyl groups include: vinyl, allyl, isopropenyl, pentenyl, cyclohexenyl, cycloheptenyl, and cyclooctenyl; and examples of alkynyl groups include: ethynyl, propynyl, isopropynyl, pentyynyl, and cyclohexynyl.
[0042] The term "substituted or unsubstituted C1-C" 10 "alkyl" includes substituted C1-C 10 Alkyl and unsubstituted C1-C10 Alkyl; wherein the substituted C1-C 10 Alkyl refers to an alkyl group in which one or more substituents replace hydrogen on one or more carbons of an alkyl chain. Such substituents are selected from at least one of C1-C5 alkyl, C1-C5 alkoxy, halogen, cyano, carboxyl, sulfonic acid, and sulfonyl groups.
[0043] When the aforementioned alkyl group with 1 to 10 carbon atoms contains an oxygen atom, it can be an alkoxy group, such as an alkoxy group with 1 to 10 carbon atoms. More preferably, an alkoxy group with 1 to 6 carbon atoms is selected as an example of an alkoxy group, specifically including: methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, cyclopentoxy, and cyclohexoxy.
[0044] The term "substituted or unsubstituted C1-C" 10 "Alkoxy" includes substituted C1-C 10 Alkoxy and unsubstituted C1-C 10 Alkoxy groups; wherein the substituted C1-C 10 An alkoxy group is a group in which one or more substituents replace hydrogen on one or more carbons in an alkoxy chain. Such substituents are selected from at least one of C1-C5 alkyl, C1-C5 alkoxy, halogen, cyano, carboxyl, sulfonic acid, and sulfonyl groups.
[0045] The term "substituted or unsubstituted C6-C" 26 "Aryl" includes substituted C6-C 26 aryl and unsubstituted C6-C 26 Aryl; wherein the substituted C6-C 26 Aryl refers to an aryl group in which one or more substituents replace one or more hydrogen atoms on the carbon atom of the aryl group. Such substituents are selected from at least one of C1-C5 alkyl, C1-C5 alkoxy, halogen, cyano, carboxyl, sulfonic acid, and sulfonyl groups.
[0046] In C1-C5 alkyl groups (alkyl groups with 1 to 5 carbon atoms), alkyl refers to the free radical of a saturated or unsaturated aliphatic group, including straight-chain alkyl, straight-chain alkenyl, straight-chain alkynyl, branched-chain alkyl, branched-chain alkenyl, branched-chain alkynyl, cycloalkyl, cycloalkenyl, and cycloalkynyl.
[0047] For example, C1-C5 alkyl groups include C1-C5 saturated alkyl groups, C2-C5 alkenyl groups, and C2-C5 alkynyl groups. Examples of alkyl groups include: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, and cyclopentyl; examples of alkenyl groups include: vinyl, allyl, isopropenyl, and pentenyl.
[0048] For example, when the aforementioned alkyl group with 1 to 5 carbon atoms contains an oxygen atom, it can be an alkoxy group, such as an alkoxy group with 1 to 5 carbon atoms, specifically including: methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, and cyclopentoxy.
[0049] In one embodiment, C6-C 26 The aryl group is selected from one of phenyl, benzyl, biphenyl, p-tolyl, o-tolyl, and m-tolyl.
[0050] In one embodiment, the halogen is selected from at least one of F, Cl, and Br.
[0051] In one embodiment, R1 is selected from at least one of phenyl, halogen-substituted phenyl, C1-C5 alkyl-substituted phenyl, and C1-C5 alkoxy-substituted phenyl.
[0052] When R1 is selected from at least one of phenyl, halogen-substituted phenyl, C1-C5 alkyl-substituted phenyl, and C1-C5 alkoxy-substituted phenyl, its molecular structure contains a benzene ring, which can effectively improve the strength of the SEI film, more effectively block the reaction between the electrode sheet and the electrolyte during cycling, further improve the charge transfer rate, reduce the transfer resistance, and thus improve the rate performance and cycle performance of the battery electrode material and other electrochemical properties.
[0053] In one embodiment, the first additive (hereinafter referred to as additive A1, additive A2, additive A3, additive A4, additive A5) comprises at least one of the following compounds:
[0054]
[0055] In one embodiment, the additive mentioned above further includes a second additive, which comprises at least one of the compounds with the structure shown in Formula II:
[0056]
[0057] R2 is selected from halogens;
[0058] Halogens include at least one of F, Cl, and Br.
[0059] The second additive can form a film on the positive electrode side to inhibit the dissolution of metals, thereby improving the high-voltage resistance of the electrolyte. In addition, it can also capture H2O and PF5 through Si-O bonds to achieve the effect of water suppression and acid removal, thereby effectively reducing the interfacial film impedance and improving the cycle performance and high-voltage resistance of the battery.
[0060] The inventors of this application have discovered through extensive research that the combined use of the first additive and the second additive has a significant synergistic effect. When used together during the formation of the interfacial film, the two additives minimize the interfacial film impedance, thereby exerting a synergistic effect and effectively improving cycle stability.
[0061] In one embodiment, the second additive comprises a compound with the structure shown in Formula III:
[0062]
[0063] An exemplary method for preparing a compound with the structure shown in Formula III (hereinafter referred to as additive B1) includes the following steps:
[0064] In the presence of butyllithium, 4-fluoroaniline and trimethylchlorosilane are reacted, excess aniline is added for neutralization, and the mixture is filtered to obtain a compound with the structure shown in Formula III.
[0065] For example, solvents include dichloromethane and THF, and there are no particular restrictions on the amount of solvent added.
[0066] For example, the molar ratio of 4-fluoroaniline to trimethylchlorosilane is 1:2.5 to 1:4.
[0067] For example, the reaction temperature is -78℃, the time is 2.8 to 3.5 hours, and the chemical equation for the reaction is as follows:
[0068]
[0069] In one embodiment, the mass ratio of the first additive to the second additive is (3-10):(2-7), for example, it can be 3:2, 3:5, 3:7, 4:2, 4:5, 4:7, 5:4, 6:4, 7:4, 8:4, 9:4, 10:4, but is not limited to the listed values, other unlisted values within this range are also applicable.
[0070] The inventors further investigated the effect of the mass ratio of the two additives on performance and found that when the mass ratio of the first additive to the second additive is (3-10):(2-7), the two additives can effectively reduce the interfacial film impedance, exert a synergistic effect, and improve the performance of the battery.
[0071] In one embodiment, based on the total mass of the electrolyte, the sum of the contents of the first additive and the second additive accounts for 0.1% to 5% of the total mass of the electrolyte. For example, it can be a range of 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any combination thereof, but is not limited to the listed values; other unlisted values within this range are also applicable.
[0072] More specifically, the first additive accounts for 0.1 to 3% of the total mass of the electrolyte, and the second additive accounts for 0.01 to 2% of the total mass of the electrolyte.
[0073] The inventors of this application further investigated the effect of the mass content of additives in the electrolyte on the performance and found that the performance was better when the total content of the first additive and the second additive was controlled within the range of 0.1% to 5% of the total mass of the electrolyte. If the additives were too few (i.e., less than 0.1%), an effective passivation film could not be formed on the positive and negative electrode surfaces, and the effect of improving the stability of the interfacial film could not be achieved. Excessive first additives and second additives may lead to excessive electrolyte viscosity, increase battery polarization, and reduce the ion transport energy of the electrolyte.
[0074] In addition, it should be noted that the electrolyte described above may be supplemented with commonly used auxiliary materials in electrolytes, such as lithium salts and organic solvents, as needed.
[0075] For example, suitable lithium salts include, but are not limited to, at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium difluorodi(oxalate)phosphate, lithium tetrafluorooxalate phosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium perchlorate, lithium difluorophosphate, lithium pentafluoroethyl trifluoroborate, and lithium 4,5-dicyano-2-trifluoromethyl-imidazolium.
[0076] For example, in this application, the lithium salt accounts for 5% to 20% of the total mass of the electrolyte, such as 5%, 8%, 10%, 12%, 14%, 16%, 18%, or 20%, but is not limited to the listed values. Other unlisted values within this range are also applicable.
[0077] For example, suitable organic solvents include at least two of ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, acetonitrile, and sulfolane.
[0078] For example, in this application, the organic solvent accounts for 70% to 90% of the total mass of the electrolyte, such as 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, or 90%, but is not limited to the listed values. Other unlisted values within this range are also applicable.
[0079] It should be noted that this application does not impose any particular limitation on the preparation method of the electrolyte. Those skilled in the art can prepare the electrolyte using conventional technical means, such as mixing organic solvents, lithium salts, and additives evenly.
[0080] One embodiment of this application provides a secondary battery, including a positive electrode, a negative electrode, a separator, and an electrolyte.
[0081] For example, a secondary battery includes one of a lithium-ion battery and a sodium-ion battery.
[0082] For example, when the battery is a lithium-ion battery, the positive electrode contains a positive electrode active material that can extract and insert lithium ions, and the negative electrode contains a negative electrode active material that can insert and extract lithium ions.
[0083] Specifically, when the battery is a lithium-ion battery, the positive electrode active material can be selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or compounds obtained by adding other transition metals or non-transition metals to the aforementioned oxides. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more.
[0084] Specifically, when the battery is a lithium-ion battery, the negative electrode active material can be selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.
[0085] For example, when the battery is a sodium-ion battery, the positive electrode contains a positive electrode active material that can extract and insert sodium ions, and the negative electrode contains a negative electrode active material that can insert and extract sodium ions.
[0086] Specifically, the positive electrode active material can be selected from sodium-iron composite oxides, sodium-cobalt composite oxides, sodium-manganese composite oxides, sodium-nickel composite oxides, sodium-nickel-titanium composite oxides, sodium-nickel-manganese composite oxides, sodium-iron-manganese composite oxides, sodium-nickel-cobalt-manganese composite oxides, sodium-iron phosphate compounds, sodium-manganese phosphate compounds, sodium-cobalt phosphate compounds, etc. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials in batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more.
[0087] Specifically, the negative electrode active material includes at least one of hard carbon, natural graphite, artificial graphite, soft carbon, carbon black, acetylene black, carbon nanotubes, graphene, and carbon nanofibers. Other examples of negative electrode active materials include elemental forms of elements that alloy with sodium, such as Si, Ge, Pb, In, Zn, H, Ca, Sr, Ba, Ru, and Rh, as well as oxides and carbides containing these elements. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.
[0088] In the secondary battery mentioned in this application, the specific type of separator is not limited. It can be any separator material used in existing batteries, such as polyethylene, polypropylene, polyvinylidene fluoride and their multilayer composite films, but is not limited to these.
[0089] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the aforementioned electrode assembly and electrolyte.
[0090] 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. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.
[0091] This application does not impose any particular restrictions on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape.
[0092] For example, in the secondary battery of this application, the charging cut-off voltage of the battery may be not less than 4.2V, that is, the battery can be used in a high voltage state of not less than 4.2V. Preferably, the battery can operate in the range of 4.2V to 4.9V, and more preferably, the battery can operate in the range of 4.3V to 4.8V.
[0093] For example, in the secondary battery of this application, the battery's operating temperature can be greater than 45°C, meaning the battery can be used at a high temperature of not less than 45°C. Preferably, the battery can operate within the range of 45 to 70°C.
[0094] One embodiment of this application provides an electrical device including the secondary battery described above.
[0095] For example, the aforementioned electrical devices 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 are not limited thereto.
[0096] The present invention is further illustrated below with specific embodiments:
[0097] Example 1
[0098] Preparation of lithium-ion pouch batteries:
[0099] (1) Preparation of electrolyte
[0100] At room temperature, in a glove box filled with argon (H2O < 1 ppm, O2 < 1 ppm), EC, EMC, and DEC were mixed thoroughly at a mass ratio of 3:5:2. Molecular sieves are used to remove water, yielding a mixed solvent.
[0101] Lithium salt LiPF6 was added to the mixed solvent and mixed evenly. Then additive A1 was added and mixed evenly to obtain the electrolyte.
[0102] The electrolyte comprises the following components by mass percentage: 0.15% additive A1, 12.5% LiPF6 and 87.35% mixed solvent.
[0103] (2) Preparation of positive electrode sheet
[0104] The positive electrode active material Li(Ni) 0.8 Mn 0.1 Co 0.1 O2 (NMC811), conductive agent acetylene black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of NMC811:Super P:PVDF = 94:3:3, and then uniformly dispersed in 1-methyl-2-pyrrolidone (NMP) to form a uniform black slurry. The mixed slurry is coated on both sides of aluminum foil, and after baking, rolling, and cutting, the positive electrode sheet is obtained.
[0105] (3) Preparation of negative electrode sheet
[0106] The negative electrode active material graphite, conductive agent acetylene black (Super P) and binder SBR are mixed evenly in a mass ratio of graphite:SuperP:SBR = 94:3:3, and then evenly dispersed in deionized water to form a uniform black slurry. The mixed slurry is coated on both sides of copper foil, and then baked, rolled, and cut into sheets to obtain the negative electrode sheet.
[0107] (4) Manufacturing of pouch batteries
[0108] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes. After winding, hot pressing and shaping, and electrode tab welding, a bare cell is obtained. The bare cell is placed in an outer packaging aluminum-plastic film and baked in an oven at 85±10℃ for 24 hours. The electrolyte prepared above is injected into the dried battery, and the battery is allowed to stand, form, and be capacity tested to complete the preparation of the lithium-ion soft-pack battery.
[0109] The remaining embodiments and comparative examples are the same as in Embodiment 1, with differences shown in Table 1.
[0110] Test case
[0111] Battery performance test
[0112] Room temperature DCR test: At 25°C, the soft pack batteries obtained in the examples and comparative examples were charged to 4.5V at 1C, then discharged at 1C capacity for 30 minutes. After adjusting to 50% SOC, they were pulsed discharged at 5C for 10 seconds and then charged for 10 seconds. The DCR was calculated as (voltage before pulse discharge - voltage after pulse discharge) / discharge current * 100%.
[0113] Room temperature high-voltage cycle performance test: At 25±2℃, the pouch batteries obtained in the examples and comparative examples were subjected to charge-discharge cycle tests within the range of 3.5~4.8V at a charge-discharge rate of 1C / 1C. The discharge specific capacity of the battery in the first cycle and the discharge specific capacity after 500 cycles were recorded. The capacity retention rate after 500 cycles = discharge specific capacity after 500 cycles / discharge specific capacity in the first cycle * 100%. The recorded data are shown in Table 1. The high-temperature cycle test method is the same as above, except that the cycle temperature is 60℃.
[0114] Table 1: Test results of additive content and battery performance in the examples and comparative examples (Test conditions: temperature 25℃, pressure 3.5~4.8V)
[0115]
[0116]
[0117] analyze:
[0118] As can be seen from the comparison between Examples 1-19 and Comparative Example 4, when the electrolyte contains a compound with the structure shown in Formula I of this application, it helps to form a stable passivation film containing nitrogen heteroatoms on the surfaces of the positive and negative electrodes, respectively, suppressing electrolyte decomposition, suppressing the increase of interfacial impedance, and improving the lithium ion permeability in the passivation film. In addition, the increase of the inorganic layer can also reduce the risk of electrode leakage, thereby improving cycle stability. Therefore, the internal resistance of the batteries in Examples 1-19 is lower than that of the comparative example, and the cycle performance is higher than that of the comparative example 4.
[0119] As can be seen from the comparison between Examples 5 and Examples 9-10, when the electrolyte contains compounds with the structure shown in Formula I and compounds with the structure shown in Formula II, there is a significant synergistic effect. The two compounds work together during the formation of the interfacial film to minimize the interfacial film impedance, thereby exerting a synergistic effect and effectively improving cycle stability.
[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.
Claims
1. An electrolyte, characterized in that, Includes additives, said additives including a first additive, the first additive including at least one of compounds with the structure shown in Formula I; R1 is selected from substituted or unsubstituted C1-C. 10 Alkyl, substituted or unsubstituted C1-C 10 Alkoxy, substituted or unsubstituted C6-C 26 At least one of aryl, nitrile, cyanate, isocyanate, amide, and halogen; The substituent is selected from at least one of C1-C5 alkyl, C1-C5 alkoxy, halogen, cyano, carboxyl, sulfonic acid, and sulfonyl groups; The first additive accounts for 0.1-3% of the total mass of the electrolyte.
2. The electrolyte according to claim 1, characterized in that, The C6-C 26 The aryl group is selected from one of phenyl, benzyl, biphenyl, p-tolyl, o-tolyl, and m-tolyl; and / or The halogen is selected from at least one of F, Cl, and Br.
3. The electrolyte according to claim 1, characterized in that, R1 is selected from at least one of phenyl, halogen-substituted phenyl, C1-C5 alkyl-substituted phenyl, and C1-C5 alkoxy-substituted phenyl.
4. The electrolyte according to claim 1, characterized in that, The first additive includes at least one of the following compounds: 。 5. The electrolyte according to claim 1, characterized in that, The additive further includes a second additive, the second additive comprising at least one of the compounds with the structure shown in Formula II: R2 is selected from halogens; The halogen includes at least one of F, Cl, and Br.
6. The electrolyte according to claim 5, characterized in that, The second additive includes compounds with the structure shown in Formula III: 。 7. The electrolyte according to claim 5, characterized in that, The mass ratio of the first additive to the second additive is (3-10):(2-7).
8. The electrolyte according to claim 7, characterized in that, Based on the total mass of the electrolyte, the sum of the contents of the first additive and the second additive accounts for 0.1% to 5% of the total mass of the electrolyte.
9. A secondary battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and the electrolyte as described in any one of claims 1 to 8.
10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.