Electrolyte, battery and electric device

Abstract

The invention discloses an electrolyte and a battery. The electrolyte comprises at least one of a first additive or a second additive and a third additive, the first additive comprises a compound shown in a formula I, the second additive comprises a compound shown in a formula II, and the third additive comprises ethylene carbonate (VC), fluoroethylene carbonate (FEC) and 1, 3-propylene glycol. The additive is at least one of 1, 3-propane sultone (PS), lithium difluoro (oxalato) borate (LiODFB), lithium difluorophosphate (LiPO2F2) and ethylene sulfate (DTD); # imgabs0 # R1 is selected from an alkyl group, a hydrocarbyl group, an alkynyl group, a nitrile group, an aryl group, a fluorine group or a fluoroalkyl group, and R2 is selected from an alkyl group, a hydrocarbyl group or a fluoroalkyl group; and R3 is selected from alkyl, alkenyl or fluoroalkyl.

Description

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] One of the challenges that batteries face in practical applications is their sensitivity to ambient temperature. At high temperatures, batteries are prone to bloating, which reduces safety; at low temperatures, the battery's discharge capacity usually decreases significantly, affecting its performance and application range. Therefore, it is crucial to develop a battery that can work stably in a wide temperature range. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one purpose of the present application is to provide an electrolyte and a battery, wherein the electrolyte of the present application can suppress the flatulence of the battery during high-temperature storage, reduce the internal resistance, and improve the low-temperature discharge performance of the battery.

[0004] Therefore, in the first aspect of the present application, the present application proposes an electrolyte. According to an embodiment of the present application, the electrolyte comprises: at least one of the first additive or the second additive, and a third additive, wherein:

[0005] The first additive includes a compound shown in formula I,

[0006]

[0007] R1 is selected from alkyl, hydrocarbon, alkynyl, nitrile, aryl, fluorine or fluoroalkyl, R2 is selected from alkyl, hydrocarbon or fluoroalkyl;

[0008] The second additive comprises a compound represented by formula II,

[0009]

[0010] R3 is selected from alkyl, alkenyl or fluoroalkyl;

[0011] The third additive includes at least one of ethylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), lithium difluorooxalatoborate (LiODFB), lithium difluorophosphate (LiPO2F2), and dithiodisulfate (DTD).

[0012] The electrolyte of the present application is intended to improve the cycle performance, low-temperature discharge performance and high-temperature storage performance of the battery by adding a specific combination of additives. Additives include three categories: a first additive, a second additive and a third additive. At least one of the first additive and the second additive is combined with the third additive and added to the lithium-ion battery to exert different effects. Among them, the first additive is a nitrogen-containing additive. On the one hand, during formation, the nitrogen element can form a stable solid electrolyte interface (SEI) film on the surface of the negative electrode of the battery. This film can protect the electrode and prevent further decomposition of the electrolyte, thereby extending the service life of the battery; on the other hand, the nitrogen element can combine with metal elements, which can effectively inhibit the dissolution of metal elements during the storage of the battery, prevent the accumulation of metal elements at the negative electrode, and reduce the damage of metal elements to the negative electrode SEI film, thereby inhibiting battery bloating. The second additive is a sulfur-containing additive, which has a low film-forming impedance and has a significant improvement effect on low-temperature discharge. In addition, the fluorine element it contains has high electronegativity in electrochemical properties and can form an SEI film containing inorganic substances such as LiF at the negative electrode. This SEI film has a low impedance to lithium ions, which helps to reduce the internal resistance of the battery and further improve the low-temperature discharge performance. As a conventional additive suitable for different battery systems, the third additive mainly forms a basic SEI film in the formation and aging stage to ensure the basic comprehensive performance of the battery. By combining the first and / or second additives, the cycle stability and safety of the battery can be further improved, and the performance of the battery under extreme temperature conditions can be enhanced, especially the discharge capacity in low temperature environments and the stability in high temperature environments.

[0013] According to an embodiment of the present application, the electrolyte may further include at least one of the following additional technical features:

[0014] According to an embodiment of the present application, based on the total mass of the electrolyte, the mass proportion of the first additive is 0.01%-3.5%.

[0015] According to an embodiment of the present application, based on the total mass of the electrolyte, the mass proportion of the first additive is 0.1%-3.5%.

[0016] According to an embodiment of the present application, based on the total mass of the electrolyte, the mass proportion of the second additive is 0.01%-3.5%.

[0017] According to an embodiment of the present application, based on the total mass of the electrolyte, the mass proportion of the second additive is 0.1%-3.5%.

[0018] According to an embodiment of the present application, based on the total mass of the electrolyte, the mass proportion of the third additive is 0.5%-5%.

[0019] According to an embodiment of the present application, the first additive includes at least one of the compounds represented by Formula I-1 and Formula I-2:

[0020]

[0021] According to an embodiment of the present application, the second additive includes at least one of the compounds represented by Formula II-1 and Formula II-2:

[0022]

[0023] According to an embodiment of the present application, the electrolyte includes the first additive and the third additive.

[0024] According to an embodiment of the present application, the electrolyte includes the second additive and the third additive.

[0025] According to an embodiment of the present application, the electrolyte includes the first additive, the second additive, and the third additive.

[0026] In the second aspect of the present application, the present application proposes a battery. According to an embodiment of the present application, the battery includes the electrolyte described in the first aspect. As mentioned above, the electrolyte of the present application can suppress the flatulence of the battery and improve the high-temperature storage performance of the battery, while reducing the internal resistance of the battery and improving the low-temperature discharge performance of the battery. Therefore, adding the electrolyte of the present application to the battery can improve the cycle performance, low-temperature discharge performance and high-temperature storage performance of the battery. Those skilled in the art can understand that the battery has all the characteristics and advantages of the electrolyte described above, and will not be elaborated here.

[0027] In the third aspect of the present application, the present application proposes an electrical device. According to an embodiment of the present application, the electrical device includes the battery described in the second aspect. Those skilled in the art can understand that the electrical device has all the features and advantages of the electrolyte described above, and no further details will be given here.

[0028] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. DETAILED DESCRIPTION

[0029] The embodiments of the present application are described in detail below, which are intended to be used to explain the present application but should not be construed as limiting the present application.

[0030] 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 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.

[0031] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the description and claims of this application and any variations thereof are intended to cover non-exclusive inclusions.

[0033] In this document, the terms "include" or "comprising" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0034] The term "alkyl" refers to a saturated straight or branched monovalent hydrocarbon group, wherein the alkyl group may be optionally substituted with one or more substituents described herein. Unless otherwise specified, the alkyl group contains 1-20 carbon atoms. In one embodiment, the alkyl group contains 1-12 carbon atoms; in another embodiment, the alkyl group contains 3-12 carbon atoms; in another embodiment, the alkyl group contains 1-6 carbon atoms; in yet another embodiment, the alkyl group contains 1-4 carbon atoms.

[0035] Examples of alkyl groups include, but are not limited to, methyl (Me, -CH3), ethyl (Et, -CH2CH3), n-propyl (n-Pr, -CH2CH2CH3), isopropyl (i-Pr, -CH(CH3)2), n-butyl (n-Bu, -CH2CH2CH2CH3), isobutyl (i-Bu, -CH2CH(CH3)2), sec-butyl (s-Bu, -CH(CH3)CH2CH3), tert-butyl (t-Bu, -CH(CH3)CH2CH3), u, -C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (-CH2CH2CH(CH3)2), 2-methyl-1 -butyl (-CH2CH(CH3)CH2CH3), n-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH(CH3)CH2CH3 ), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3), n-heptyl, n-octyl, and the like.

[0036] The term "fluoroalkyl" refers to an organic compound in which a hydrogen atom in an alkyl group is replaced by a fluorine atom.

[0037] The term "alkenyl" refers to a straight or branched chain monovalent hydrocarbon radical having at least one carbon-carbon sp 2 Double bonds, including "cis" and "trans" orientations, or "E" and "Z" orientations. Wherein, the alkenyl group may be optionally substituted with one or more substituents described herein. In one embodiment, the alkenyl group contains 2-12 carbon atoms; in another embodiment, the alkenyl group contains 3-12 carbon atoms; in another embodiment, the alkenyl group contains 2-6 carbon atoms; in yet another embodiment, the alkenyl group contains 2-4 carbon atoms. Examples of alkenyl groups include, but are not limited to, vinyl (-CH=CH2), allyl (-CH2CH=CH2), and the like.

[0038] The term "alkynyl" refers to a straight or branched monovalent hydrocarbon radical containing 2-12 carbon atoms, wherein at least one carbon-carbon sp triple bond is present, wherein the alkynyl group may be optionally substituted with one or more substituents described herein. In one embodiment, the alkynyl group contains 3-12 carbon atoms; in another embodiment, the alkynyl group contains 2-6 carbon atoms; in yet another embodiment, the alkynyl group contains 2-4 carbon atoms. Examples of alkynyl groups include, but are not limited to, ethynyl (-C≡CH), propargyl (-CH2C≡CH), 1-propynyl (-C≡C-CH3), and the like.

[0039] The term "aryl" refers to a monocyclic, bicyclic or tricyclic carbon ring system containing 6-14 ring atoms, or 6-12 ring atoms, or 6-10 ring atoms, wherein at least one ring is aromatic and has one or more attachment points to the rest of the molecule. The term "aryl" can be used interchangeably with the term "aromatic ring". In one embodiment, an aryl group is a carbon ring system consisting of 6-10 ring atoms and containing at least one aromatic ring. Examples of aryl groups can include phenyl, naphthyl and anthracenyl. Wherein, the aryl group can be independently optionally substituted with one or more substituents described herein.

[0040] The term "nitrile" or "-CN" refers to a nitrile structure. This group can be connected to other groups.

[0041] Lithium-ion batteries are widely used in power, energy storage, aerospace, digital and other fields due to their advantages such as high voltage, large capacity, no memory effect and long life. In recent years, lithium-ion batteries have achieved great success in the field of high-energy batteries, but consumers still expect batteries with higher comprehensive performance. High-comprehensive performance batteries depend on the research and development of new electrode materials and electrolyte systems. However, factors such as the dissolution of positive electrode metal ions, the occurrence of electrolyte side reactions, and the degradation of the electrode-electrolyte interface under high temperature conditions lead to serious gas production in lithium-ion batteries, and it is difficult to improve the comprehensive performance of lithium batteries. In order to solve the problem of high-temperature gas production in lithium batteries, film-forming additives are usually used to regulate the formation of a stable SEI film at the electrode-electrolyte interface, but the SEI films regulated by such additives are thicker or have poor ion conductivity, resulting in a large impedance of the lithium battery, which makes the battery cycle performance and low-temperature performance poor. Therefore, it is of great significance to find an electrolyte with stable performance and significant improvement in battery performance.

[0042] In view of this, the applicant has developed an electrolyte comprising at least one of a first additive and a second additive, and a third additive. Among them, the first additive can inhibit the dissolution of metal ions under high temperature conditions and inhibit flatulence, thereby improving the cycle performance of the battery. The second additive can form an SEI film containing inorganic substances such as LiF at the negative electrode, which can reduce the internal resistance of the battery, thereby improving the low-temperature discharge performance of the battery. The first additive and the second additive can form a synergistic effect with the third additive separately or simultaneously to further improve the comprehensive performance of the battery. The electrolyte, battery and electrical device will be introduced in detail below.

[0043] Electrolyte

[0044] The present application proposes an electrolyte. According to an embodiment of the present application, the electrolyte includes: at least one of a first additive or a second additive, and a third additive, wherein:

[0045] The first additive includes a compound shown in formula I,

[0046]

[0047] R1 is selected from alkyl, hydrocarbon, alkynyl, nitrile, aryl, fluorine or fluoroalkyl, R2 is selected from alkyl, hydrocarbon or fluoroalkyl;

[0048] The second additive comprises a compound represented by formula II,

[0049]

[0050] R3 is selected from alkyl, alkenyl or fluoroalkyl;

[0051] The third additive includes at least one of ethylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propane sultone (1,3-PS), lithium difluorooxalatoborate (LiODFB), lithium difluorophosphate (LiPO2F2), and dithiodisulfate (DTD).

[0052] The electrolyte of the present application is intended to improve the cycle performance, low-temperature discharge performance and high-temperature storage performance of the battery by adding a specific combination of additives. Additives include three categories: a first additive, a second additive and a third additive. At least one of the first additive and the second additive is combined with the third additive and added to the lithium-ion battery to exert different effects. Among them, the first additive is a nitrogen-containing additive. On the one hand, during formation, the nitrogen element can form a stable solid electrolyte interface (SEI) film on the surface of the negative electrode of the battery. This film can protect the electrode and prevent further decomposition of the electrolyte, thereby extending the service life of the battery; on the other hand, the nitrogen element can combine with metal elements, which can effectively inhibit the dissolution of metal elements during the storage of the battery, prevent the accumulation of metal elements at the negative electrode, and reduce the damage of metal elements to the negative electrode SEI film, thereby inhibiting battery bloating. The second additive is a sulfur-containing additive, which has a low film-forming impedance and has a significant improvement effect on low-temperature discharge. In addition, the fluorine element it contains has high electronegativity in electrochemical properties and can form an SEI film containing inorganic substances such as LiF at the negative electrode. This SEI film has a low impedance to lithium ions, which helps to reduce the internal resistance of the battery and further improve the low-temperature discharge performance. As a conventional additive suitable for different battery systems, the third additive mainly forms a basic SEI film in the formation and aging stage to ensure the basic comprehensive performance of the battery. By combining the first and / or second additives, the cycle stability and safety of the battery can be further improved, and the performance of the battery under extreme temperature conditions can be enhanced, especially the discharge capacity in low temperature environments and the stability in high temperature environments.

[0053] In some embodiments of the present application, the first additive includes at least one of the compounds represented by Formula I-1 and Formula I-2:

[0054]

[0055] Therefore, the above-mentioned type of first additive not only helps to form a stable SEI film at the negative electrode of the battery, prevents the electrolyte from decomposing the electrode, and prolongs the service life of the battery; it can also form complexes with metal elements in the battery (such as manganese, cobalt, etc.), reduce the dissolution of these metal elements in the electrolyte, thereby reducing metal deposition and dendrite formation, and improving the safety and cycle stability of the battery.

[0056] In some embodiments of the present application, the second additive includes at least one of the compounds represented by Formula II-1 and Formula II-2:

[0057]

[0058] Therefore, the above-mentioned type of second additive can reduce the internal resistance of the battery and improve the discharge performance of the battery at low temperatures; in addition, the fluorine element in the second additive has a high electronegativity and can form a SEI film containing inorganic substances such as LiF at the negative electrode, thereby reducing the impedance to lithium ions and further improving the low-temperature discharge performance of the battery.

[0059] In some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the first additive is 0.01%-3.5%. For example, it can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 3.5%, etc., or it can be a range composed of any of the above numerical values. Therefore, by making the mass proportion of the first additive within the above range, the first additive can play a better role, forming a stable SEI film on the negative electrode surface of the battery to protect the electrode, while inhibiting the dissolution of metal elements, reducing metal deposition and the formation of dendrites, inhibiting the flatulence of the battery, and improving the thermal stability and safety of the battery. According to an embodiment of the present application, the mass proportion of the first additive is 0.1%-3.5%, 0.5%-3.5%.

[0060] In some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the second additive is 0.01%-3.5%. For example, it can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 3.5%, etc., or it can be a range composed of any of the above numerical values. Therefore, by making the mass proportion of the second additive within the above range, the second additive can play a better role, reduce the viscosity of the electrolyte at low temperatures, increase the migration rate of ions, and form an SEI film containing inorganic substances such as LiF at the negative electrode, reduce the internal resistance of the battery, and improve the low-temperature discharge performance of the battery. According to an embodiment of the present application, the mass proportion of the second additive is 0.1%-3.5%, 0.5%-3.5%.

[0061] In some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the third additive is 0.5%-5%. For example, it can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, etc., or it can be a range composed of any of the above values. Thus, by making the mass proportion of the third additive within the above range, a protective film can be formed on the positive and negative electrodes, inhibiting the decomposition of the electrolyte at the positive and negative electrodes, and ensuring the basic electrical performance of the battery. According to an embodiment of the present application, the mass proportion of the third additive is 2%-5%.

[0062] In some embodiments of the present application, the electrolyte includes the first additive and the third additive. During the formation and aging stages, the first additive can cooperate with the third additive to form a protective film at the positive and negative electrodes. The addition of the first additive can inhibit the dissolution of the positive electrode metal elements and improve the high temperature performance of the battery. The amount of the first additive added needs to be appropriate. If the amount is too much, excessive film formation will occur, resulting in increased internal resistance. If the amount is too little, the protection is insufficient and its performance cannot be exerted.

[0063] In some embodiments of the present application, the electrolyte includes the second additive and the third additive. During the formation and aging stages, the second additive can cooperate with the third additive to form a protective film on the positive and negative electrodes. The addition of the second additive can further reduce the internal resistance and improve the low-temperature discharge capability on the basis of the third additive. The amount of the second additive added needs to be appropriate. If the amount is too much, excessive film formation will occur, resulting in increased internal resistance. If the amount is too little, the protection is insufficient and its performance cannot be exerted.

[0064] In some embodiments of the present application, the electrolyte includes the first additive, the second additive and the third additive, and while ensuring that the third additive functions normally, the first additive can inhibit the dissolution of metal elements, inhibit flatulence, improve the high-temperature storage performance of the battery, form an SEI film containing inorganic substances such as LiF at the negative electrode, reduce the internal resistance of the battery, and improve the low-temperature discharge performance of the battery. Therefore, the cycle performance, low-temperature discharge performance and high-temperature storage performance of the lithium battery can be improved.

[0065] In some embodiments of the present application, the electrolyte further includes: an organic solvent and an electrolyte salt, thereby enabling active ions (such as lithium ions) to move freely inside the battery.

[0066] In some embodiments of the present application, the mass proportion of the organic solvent is 70% to 90% based on the total mass of the electrolyte, for example, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, etc., or a range consisting of any of the above values.

[0067] In some embodiments of the present application, the mass proportion of the electrolyte salt is 8% to 20% based on the total mass of the electrolyte, for example, 8%, 10%, 12%, 15%, 18%, 20%, etc., or a range consisting of any of the above values.

[0068] In some embodiments of the present application, the organic solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate (EA), propyl acetate, methyl propionate, ethyl propionate (EP), propyl propionate (PP), methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone, and diethyl sulfone.

[0069] In some embodiments of the present application, the electrolyte may further include an electrolyte salt, and the electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorobis(oxalatophosphate), and lithium tetrafluorooxalatophosphate.

[0070] Batteries and electrical devices

[0071] The present application proposes a battery, which includes the above-mentioned electrolyte. As mentioned above, the electrolyte of the present application can suppress the flatulence of the battery, improve the high-temperature storage performance of the battery, and at the same time can reduce the internal resistance of the battery and improve the low-temperature discharge performance of the battery. Therefore, adding the electrolyte of the present application to the battery can improve the cycle performance, low-temperature discharge performance and high-temperature storage performance of the battery. Those skilled in the art can understand that the battery has all the characteristics and advantages of the electrolyte described above, and will not be elaborated here.

[0072] In some embodiments of the present application, the 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 removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged 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.

[0073] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0074] Exemplarily, when the positive electrode sheet is used in a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, 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. Among them, 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 Co 1 / 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 0.8 Co 0.15 Al 0.05 O2) or at least one of its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure 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, or a composite material of lithium iron manganese phosphate and carbon.

[0075] In some embodiments of the present application, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material base and a metal layer formed on at least one side of the polymer material base. For example, the composite positive electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and other substrates).

[0076] In some embodiments of the present application, the positive electrode active material layer may further include a conductive agent. As an 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.

[0077] In some embodiments of the present application, the positive electrode active material layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0078] In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0079] In some embodiments of the present application, the negative electrode current collector may be a metal foil or a composite negative electrode current collector. For example, as the metal foil, a copper foil may be used. The composite negative electrode 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 negative electrode current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0080] In some embodiments of the present application, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys.

[0081] In some embodiments of the present application, the negative electrode active material layer may further include a binder. The binder may include 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).

[0082] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] In some embodiments of the present application, the negative electrode active material layer may further optionally include other auxiliary agents, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0084] The present invention has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected. According to an embodiment of the present application, the isolation membrane may be made of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene or polyvinylidene fluoride.

[0085] In some embodiments of the present application, the battery may include an outer package for packaging the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0086] In some embodiments of the present application, the outer packaging may include a shell and a cover plate. The shell 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 has an opening connected to the receiving cavity, and the cover plate can be covered on the opening to close the receiving cavity.

[0087] In some embodiments of the present application, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0088] The outer packaging of the battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0089] The battery of the present application may include a battery cell form, a battery module form and a battery pack form. In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0090] The present application proposes an electric device. According to an embodiment of the present application, the electric device comprises the aforementioned battery. Therefore, the electric device of the present application has high-efficiency energy output and excellent service life and safety performance.

[0091] Battery cells, battery modules, and battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0092] As an electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0093] As an embodiment, the electric device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device for high power and high energy density of the battery, a battery pack or a battery module may be used.

[0094] As another embodiment, 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.

[0095] The scheme of the present application will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the literature in this area or the product specification are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0096] Example 1

[0097] 1. Preparation of positive electrode sheet

[0098] The positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive carbon black, conductive carbon nanotubes and binder polyvinylidene fluoride are dispersed in a solvent N-methylpyrrolidone in a mass ratio of 95.5:2.5:0.5:1.5 to obtain a positive electrode active material layer slurry; the positive electrode active material layer slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained after drying, rolling, baking, slitting and spot welding of the pole ears.

[0099] 2. Preparation of negative electrode sheet

[0100] The negative electrode active material graphite (purchased from Jiangxi Zichen), the conductive agent carbon black, the binder styrene-butadiene rubber and sodium carboxymethyl cellulose were dispersed in deionized water in a mass ratio of 95:1.5:2:1.5, and stirred evenly to obtain the negative electrode active material layer slurry; the negative electrode active material layer slurry was evenly coated on the surface of the negative electrode current collector copper foil, and the negative electrode sheet was obtained after drying, rolling, baking, slitting and spot welding of the pole ears.

[0101] 3. Preparation of electrolyte

[0102] EC, EMC and DEC are mixed in a mass ratio of 3:5:2, and after mixing, lithium salt, the first additive and the third additive are added according to the molar concentration and mass fraction of each component, and the mixture is uniformly mixed to obtain an electrolyte. Among them, the lithium salt includes LiPF6, and the mass proportion of the lithium salt in the electrolyte is 13.5%; the first additive includes compound I-1 accounting for 0.5% of the total mass of the electrolyte; the third additive includes 1% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (1,3-PS) and 0.8% of lithium difluorophosphate (LiPO2F2) accounting for the total mass of the electrolyte.

[0103] 4. Isolation film

[0104] A polyethylene film is used as the isolation film.

[0105] 5. Lithium-ion battery preparation

[0106] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is in the middle of the positive and negative electrode sheets to isolate the positive and negative electrodes, and the bare battery cell is wound, and the pole ears are welded. The bare battery cell is placed in an outer package, and the prepared electrolyte is injected into the dried battery cell. The lithium-ion battery cell is packaged, allowed to stand, formed, and shaped to complete the preparation of the lithium-ion battery.

[0107] The preparation methods of the lithium ion batteries of Examples 2-12 and Comparative Examples 1-4 are the same as that of Example 1, except that the composition of the additives in the electrolyte is different, as shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] Among them, “ / ” in the table means none.

[0112] Performance Testing

[0113] 1. Cycle performance experiment: The batteries obtained in each embodiment and comparative example were tested for cycle performance at 3.0-4.4V and 1C rate charge and discharge at room temperature and 45°C, and the capacity retention rate after 1000 cycles was recorded.

[0114] 2. High temperature storage experiment: The batteries obtained from each embodiment and comparative example were subjected to 5 charge and discharge cycle tests at room temperature at a charge and discharge rate of 1C, and then charged to a fully charged state at a rate of 1C. Record the 1C capacity Q and battery thickness T respectively. Store the fully charged battery at 60°C for 7 days, record the battery thickness T0 and 1C discharge capacity Q1, then charge and discharge the battery at room temperature at a rate of 1C for 5 weeks, record the 1C discharge capacity Q2 and battery thickness T1, and calculate the experimental data such as the battery high temperature storage capacity retention rate, capacity recovery rate and thickness expansion rate. The results are recorded as shown in Table 2, and the calculation formula used is as follows:

[0115] Capacity retention rate (%) = Q1 (mAh) ÷ Q (mAh) × 100%

[0116] Capacity recovery rate (%) = Q2 (mAh) ÷ Q (mAh) × 100%

[0117] Thickness expansion rate (%) = (T1-T0)÷T0×100%.

[0118] 3. Low temperature discharge experiment: The batteries obtained in each embodiment and comparative example were cycled 3 times at room temperature at a charge rate of 0.5C and a discharge rate of 0.5C, and then charged to a fully charged state at a rate of 0.5C, and the last discharge capacity Q3 was recorded. The fully charged battery was placed in a comprehensive test temperature cabinet at -20°C for 4 hours, and then discharged to 3V at a rate of 0.2C, and the discharge capacity Q4 was recorded.

[0119] Low temperature discharge capacity retention rate (%) = Q4 / Q3×100%

[0120] The test results are shown in Table 2.

[0121] By comparing Example 1, Example 4, Example 5, Examples 8-12 and Comparative Examples 1-4, it is found that the first additive and the second additive can improve the comprehensive performance of the battery. When the first, second and third additives are used together, the effect is better than when they are used alone, indicating that there is a synergistic effect between the three additives. At the same addition amount, the I-2 additive containing a double bond (Example 5) has a better effect on high temperature improvement than I-1 (Example 1), mainly because the additive containing a double bond is easier to oxidize and reduce to form a film, and its film is generally thicker, which has a better improvement on the high temperature performance of the battery.

[0122] By comparing Examples 1-3 with Examples 5-7, it can be seen that the comprehensive performance of the battery can be effectively improved only when the addition amounts of the first additive and the second additive are respectively within a certain range. When too little is added, the improvement on various performances is not obvious. When too much is added, it will cause excessive reaction of the additives and consume excessive active lithium, which will cause the capacity retention rate of the battery to decrease, and is also not conducive to the low-temperature discharge performance of the battery.

[0123] Table 2

[0124]

[0125]

[0126] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An electrolyte, characterized in that: include: At least one of the first additive or the second additive, and a third additive, wherein The first additive includes a compound shown in formula I, R1 is selected from alkyl, hydrocarbon, alkynyl, nitrile, aryl, fluorine or fluoroalkyl, R2 is selected from alkyl, hydrocarbon or fluoroalkyl; The second additive comprises a compound represented by formula II, R3 is selected from alkyl, alkenyl or fluoroalkyl; The third additive includes at least one of ethylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, lithium difluorooxalatoborate, lithium difluorophosphate, and vinyl sulfate.

2. The electrolyte according to claim 1, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the first additive is 0.01%-3.5%.

3. The electrolyte according to claim 1, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the first additive is 0.1%-3.5%.

4. The electrolyte according to claim 1, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the second additive is 0.01%-3.5%.

5. The electrolyte according to claim 1, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the second additive is 0.1%-3.5%.

6. The electrolyte according to claim 1, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the third additive is 0.5%-5%.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The first additive includes at least one of the compounds represented by Formula I-1 and Formula I-2:

8. The electrolyte according to any one of claims 1 to 6, characterized in that: The second additive includes at least one of the compounds represented by formula II-1 and formula II-2:

9. The electrolyte according to claim 1, characterized in that The electrolyte includes the first additive and the third additive; Or, the electrolyte includes the second additive and the third additive; Alternatively, the electrolyte includes the first additive, the second additive and the third additive.

10. A battery, characterized in that: The electrolyte comprising the electrolyte according to any one of claims 1 to 9.

11. An electrical device, characterized in that: Comprising the battery as claimed in claim 10.

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