WO2021073465A1 - 用于锂离子电池的电解液、锂离子电池、电池模块、电池包及装置 - Google Patents

用于锂离子电池的电解液、锂离子电池、电池模块、电池包及装置 Download PDF

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WO2021073465A1
WO2021073465A1 PCT/CN2020/120307 CN2020120307W WO2021073465A1 WO 2021073465 A1 WO2021073465 A1 WO 2021073465A1 CN 2020120307 W CN2020120307 W CN 2020120307W WO 2021073465 A1 WO2021073465 A1 WO 2021073465A1
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electrolyte
additive
compound
lithium
ion battery
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PCT/CN2020/120307
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English (en)
French (fr)
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李永坤
吴凯
程博
鞠峰
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宁德时代新能源科技股份有限公司
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Priority to EP20876047.0A priority Critical patent/EP3979384A4/en
Publication of WO2021073465A1 publication Critical patent/WO2021073465A1/zh
Priority to US17/702,645 priority patent/US20220216517A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of batteries, and in particular to an electrolyte for lithium-ion batteries, lithium-ion batteries, battery modules, battery packs and devices.
  • lithium batteries Compared with lead-acid batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, lithium batteries have the advantages of high specific energy density, wide operating temperature range, and long cycle life, making them a mainstream position in the market for a long time. With the expansion of market demand for electronic products and the development of power and energy storage equipment, people have higher and higher expectations for the energy density of lithium-ion batteries, and it is imperative to develop lithium-ion batteries with high energy density.
  • lithium-ion batteries are one of the effective methods to increase the energy density of lithium-ion batteries, so lithium-ion batteries with a working voltage above 4.4V have become a research hotspot in many scientific research institutions and enterprises.
  • the oxidation activity of the positive electrode becomes higher, and the non-aqueous electrolyte is prone to electrochemical oxidation reaction on the surface of the positive electrode, thereby generating gas.
  • the transition metal in the positive electrode material dissolves and migrates to the negative electrode to consume active lithium. This leads to deterioration of the electrochemical performance of lithium ions and thus to failure.
  • the solution is to add a film-forming additive to the electrolyte, and improve the stability of the interface between the electrolyte and the positive electrode through the film-forming effect of the additive interface.
  • these additives can form a film on the positive electrode, they will increase the interfacial impedance and reduce the kinetic performance of lithium ion migration and diffusion in the battery, thereby degrading the storage performance and cycle performance of the lithium ion battery.
  • Some embodiments of this application provide an electrolyte, a lithium ion battery, a battery module, a battery pack, and a device for a lithium ion battery.
  • the lithium ion battery can have better cycle performance and storage performance under high voltage, and at the same time, the rate charging performance of the lithium ion battery is improved, which effectively solves the defects in the prior art.
  • the present application provides an electrolyte for a lithium ion battery, which includes an organic solvent, an electrolyte lithium salt dissolved in the organic solvent, and additives, wherein the additives include a first additive and a second additive.
  • the first additive includes an alkenyl dioxyborane compound represented by formula I or formula II:
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are each independently selected from H, a saturated alkyl group containing 1-10 carbon atoms, or R 1 and R 2 or R 7 and R 8 jointly form a 3- to 6-membered heterocyclic structure having at least one double bond and containing at least one heteroatom selected from O, S, and N.
  • the second additive includes a phosphoric acid cyclic anhydride represented by formula III, wherein R 11 , R 12 , and R 13 are each independently selected from H, saturated or unsaturated alkyl groups containing 1-20 carbon atoms, or Groups containing 6-18 carbon atoms and at least one benzene ring.
  • this application provides a lithium ion battery, including a positive electrode, a negative electrode, a separator, and the electrolyte described in the first aspect of the application.
  • the present application also provides a battery module, including the lithium ion battery described in the second aspect of the present application.
  • the present application also provides a battery pack, including the battery module described in the third aspect of the present application.
  • the present application also provides a device, including the lithium ion battery described in the second aspect of the application, and the lithium ion battery is used as a power source for the device.
  • the lithium-ion battery can have better high-temperature cycle performance, high-temperature storage performance, and lower DC impedance under high voltage, and the lithium-ion battery can have both better performance The high voltage characteristics.
  • the battery modules, battery packs, and devices including the lithium ion battery described in this application also have the same advantages as the lithium ion battery.
  • Fig. 1 is a perspective view of a lithium ion battery according to an embodiment of the present application.
  • Fig. 2 is an exploded view of the lithium ion battery shown in Fig. 1.
  • Fig. 3 is a perspective view of a battery module according to an embodiment of the present application.
  • Fig. 4 is a perspective view of a battery pack according to an embodiment of the present application.
  • Fig. 5 is an exploded view of the battery pack shown in Fig. 4.
  • Fig. 6 is a schematic diagram of a lithium ion battery used as a power supply device according to an embodiment of the present application.
  • electrolyte according to the present application and lithium ion batteries, battery modules, battery packs, and devices containing the electrolyte will be described in detail below.
  • any lower limit may be combined with any other upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and any upper limit may be combined with any other upper limit to form an unspecified range.
  • every point or single value between the end points of the range is included in the range. Therefore, each point or single numerical value can be used as its own lower limit or upper limit in combination with any other point or single numerical value, or in combination with other lower limit or upper limit to form an unspecified range. It should be understood that the enumeration of numerical values is merely an example and should not be interpreted as exhaustive.
  • the electrolyte for a lithium ion battery according to the first aspect of the present application includes an organic solvent, an electrolyte lithium salt dissolved in the organic solvent, and additives, wherein the additives include a first additive and a second additive.
  • the first additive includes an alkenyl dioxyborane compound represented by formula I or formula II:
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are each independently selected from H, saturated or unsaturated alkyl of 1-10 carbon atoms , Or R 1 and R 2 or R 7 and R 8 jointly form a 3- to 6-membered heterocyclic structure with at least one double bond and at least one heteroatom selected from O, S, and N.
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are each independently selected from H.
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are each independently selected from the saturation of 1 to 5 carbon atoms alkyl.
  • methyl methylene, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 1-methylbutyl Group, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, 1,1-dimethylpropyl, 1,3-dimethylpropyl, 2,2-dimethyl Propyl and so on.
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are each independently selected from the group consisting of 2 to 5 carbon atoms.
  • Saturated alkyl examples include, but are not limited to, vinyl or propenyl.
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are each independently selected from methyl, methylene or ethyl base.
  • R 1 and R 2 or R 7 and R 8 jointly form a 3- to 6-membered heterocyclic structure with at least one double bond and at least one heteroatom selected from O, S, and N.
  • a 3- to 6-membered heterocyclic structure with at least one double bond and at least one heteroatom selected from O, S, and N.
  • R 1 and R 2 or R 7 and R 8 form a heterocyclic structure as shown below:
  • the first additive is selected from at least one of the following compounds:
  • the first additive is an alkenyl dioxyborane compound represented by formula I, wherein R 1 , R 2 , R 3 , R 4 , and R 5 are each independently selected from H, 1 A saturated alkyl group of ⁇ 5 carbon atoms, or R 1 and R 2 jointly form a 3- to 6-membered heterocyclic structure having at least one double bond and containing at least one heteroatom selected from O, S, and N.
  • the alkenyl dioxyborane compound represented by formula I is selected from at least one of the following compounds:
  • the first additive can participate in the film formation at the interface between the positive and negative electrodes, and the interface film formed on the positive electrode (usually called the SEI film) can effectively inhibit the electrolyte from being oxidized and decomposed on the surface of the positive electrode. This way, on the one hand, it can prevent the electrolyte from oxidizing and decomposing.
  • the product deposits on the positive electrode interface to increase the interface impedance of the positive electrode. On the other hand, it can also prevent the electrolyte from oxidizing and decomposing at the positive electrode interface to produce gas and causing the interface electrical contact to deteriorate.
  • the second additive includes a phosphoric acid cyclic anhydride represented by formula III, wherein R 11 , R 12 , and R 13 are each independently selected from H, saturated or unsaturated alkyl groups containing 1-20 carbon atoms, or Groups containing 6-18 carbon atoms and at least one benzene ring.
  • R 11 , R 12 , and R 13 are each independently selected from H.
  • R 11 , R 12 , and R 13 are each independently selected from saturated alkyl groups containing 1 to 5 carbon atoms.
  • saturated alkyl groups containing 1 to 5 carbon atoms including but not limited to, methyl, methylene, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 1-methylbutyl Group, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, 1,1-dimethylpropyl, 1,3-dimethylpropyl, 2,2-dimethyl Propyl and so on.
  • R 11 , R 12 , and R 13 are each independently selected from an unsaturated alkyl group containing 1 to 5 carbon atoms.
  • unsaturated alkyl group containing 1 to 5 carbon atoms including but not limited to, vinyl, propenyl, cyclopropenyl, 1-butenyl, cis-2-butenyl, trans-2-butenyl, 1-pentenyl, 3-pentenyl Wait.
  • the second additive is selected from at least one of the following compounds: trimethylphosphoric acid cyclic anhydride (compound 2-1), triethylphosphoric acid cyclic anhydride (compound 2-2), tripropylene Phosphate cyclic anhydride (compound 2-3), or triphenyl phosphate cyclic anhydride (compound 2-4).
  • the second additive can undergo a complex exchange reaction with the main components in the SEI film formed at the negative electrode interface, which helps to form a more stable SEI film at the negative electrode interface, and significantly reduces the impedance of the negative electrode interface, so that the lithium ion battery Has good power performance.
  • the first additive can form a film on the interface between the positive and negative electrodes to prevent the electrolyte from being oxidized and decomposed, effectively inhibit the generation of gas inside the lithium ion battery, and can further prevent the second
  • the additives are oxidized and decomposed at high temperatures.
  • the second additive is preferentially reduced to form a film on the negative electrode, which can improve the disadvantage of high film formation resistance of the first additive at the negative electrode interface, effectively reduce the DCR growth during the use of the lithium ion battery, and improve the power performance of the lithium ion battery. Therefore, under the synergistic effect of the two, lithium-ion batteries can have good high-temperature cycle performance, high-temperature storage performance, and lower DC impedance, and enable lithium-ion batteries to have both good high-voltage characteristics.
  • the concentration of the first additive in the electrolyte may be 0.1% by weight, 0.2% by weight, 0.5% by weight, 1% by weight, 1.5% by weight, 2% by weight, 2.5% by weight, or 3% by weight. Any value and all ranges and subranges. For example, 0.5 wt% to 3 wt%, 0.5 wt% to 2 wt%, 1 wt% to 1.5 wt%, 1 wt% to 2 wt%, and so on.
  • the concentration of the second additive in the electrolyte may be 0.05wt%, 0.1wt%, 0.2wt%, 0.5wt%, 1wt%, 1.5wt% or 2wt%, etc., including any value therein and All ranges and sub-ranges.
  • the type of organic solvent used in the present application is not specifically limited, and can be appropriately selected according to actual needs, as long as the technical solution of the present application can be realized.
  • the organic solvent is selected from ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate. Ester, dipropyl carbonate, methyl propyl carbonate, ethylene propyl carbonate, 1,4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate One or more.
  • the organic solvent can also be selected from methyl acrylate, dimethyl sulfite, diethyl sulfite, acid anhydride, N-methylpyrrolidone, N-methylformamide, N -One or more of methylacetamide, acetonitrile, N,N-dimethylformamide, dimethylsulfoxide, methyl sulfide, and tetrahydrofuran.
  • the organic solvent is a mixed solvent of two or more kinds
  • their ratio is not particularly limited, and can be appropriately selected according to actual needs, as long as the technical solution of the present application can be realized.
  • the organic solvent when they contains two different organic solvents, they can be in a mass ratio of 1:1, 2:8, 3:7, 4:6, 8:2, 7: 3, 6:4 equal proportions to mix and use.
  • the content of the organic solvent in the electrolyte is not specifically limited, and can be appropriately selected according to actual needs, as long as the technical solution of the present application can be realized.
  • the content of the organic solvent in the electrolyte is 65 wt% to 85 wt%, optionally 70 wt% to 80 wt%.
  • the content of the organic solvent in the electrolyte may be 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, etc., including any value and all ranges and subranges therein.
  • the electrolyte lithium salt used in the present application is not specifically limited, and can be appropriately selected according to actual needs, as long as the technical solution of the present application can be realized.
  • the electrolyte lithium salt may be selected from complex lithium salts of Lewis acid and LiF.
  • LiPF 6 , LiBF 4 , LiAsF 6 , and more optional LiPF 6 , LiBF 4 are optional LiPF 6 , LiBF 4 , LiAsF 6 , and more optional LiPF 6 , LiBF 4 .
  • the electrolyte lithium salt may also be selected from imine or methylated lithium salt.
  • imine or methylated lithium salt selected from LiN(SO 2 F) 2 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , (CF 2 ) 2 (SO 2 ) 2 NLi (cyclic), (CF 2 ) 3 (SO 2 ) 2
  • LiN(SO 2 F) 2 LiN(SO 2 CF 3 ) 2
  • LiN(SO 2 C 2 F 5 ) 2 LiN(SO 2 F) 2
  • LiN(SO 2 CF 3 ) 2 LiN(SO 2 CF 3 ) 2
  • LiN(SO 2 C 2 F 5 ) 2 more preferably LiN(SO 2 F) 2 and/or LiN(SO 2 CF 3 ) 2 .
  • LiPFMSP pentafluoro((methylsulfonyl)oxy) lithium phosphate
  • LiPO 2 F 2 , Li 2 PO 3 F and LiClO 4 , and LiPO 2 F 2 and/or Li 2 PO 3 F can be selected.
  • the electrolyte lithium salt can also be selected from lithium salts with an oxalate ligand as an anion.
  • lithium salts with an oxalate ligand as an anion.
  • LiBOB and/or LiPFO lithium tetrafluoro[oxalate-O,O']phosphate, LiBOB and/or LiPFO can be selected.
  • the electrolyte lithium salt can also be selected from LiPF 6 , LiPO 2 F 2 , Li 2 PO 3 F, LiBF 4 , LiSO 3 F, LiTFMSB, LiN(SO 2 F) 2 , LiN( One or more of SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiBOB, LiPFO and lithium tetrafluoro[oxalate-O,O']phosphate, LiPF 6 , LiBF 4 are optional One or more of LiSO 3 F, LiTFMSB, LiPO 2 F 2 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 F) 2 , LiBOB, and LiPFO, and LiPF 6 is more optional.
  • the concentration of the electrolyte lithium salt in the electrolyte is not specifically limited, and can be appropriately selected according to actual needs, as long as the technical solution of the present application can be realized.
  • the concentration of the electrolyte lithium salt in the electrolyte is 0.5M, 0.8M, 1.0M, 1.2M, 1.5M, or 2.0M, including any value and all ranges and subranges therein.
  • the lithium ion battery according to the second aspect of the present application includes a positive electrode, a negative electrode, a separator, and the electrolyte described in the first aspect of the present application.
  • FIG. 1 shows a perspective view of a lithium ion battery according to an embodiment of the present application
  • FIG. 2 is an exploded view of the lithium ion battery shown in FIG. 1.
  • the lithium ion battery 5 (hereinafter referred to as the battery cell 5) according to the present application includes a case 51, an electrode assembly 52, a top cover assembly 53, a positive electrode, a negative electrode, a separator, and an electrolyte (not shown ).
  • the electrode assembly 52 is housed in the casing 51, and the number of the electrode assembly 52 is not limited, and can be one or more.
  • the battery cell 5 shown in FIG. 1 is a can-type battery, but the present application is not limited to this.
  • the battery cell 5 may be a pouch-type battery, that is, the housing 51 is replaced by a metal plastic film and the top cover is eliminated. Component 53.
  • the positive electrode is not specifically limited, and can be appropriately selected according to actual needs, and can be those positive electrodes commonly used in lithium ion batteries, as long as the technical solution of the present application can be realized.
  • the positive electrode includes a positive electrode active material that can extract and accept lithium ions.
  • the positive active material is selected from lithium transition metal composite oxides, including, but not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt oxide.
  • Aluminum oxides, these lithium transition metal oxides are compounds obtained by adding other transition metals or non-transition metals, and a mixture of one or more of the above substances.
  • the negative electrode is not specifically limited, and can be appropriately selected according to actual needs, and can be those negative electrodes commonly used in lithium ion batteries, as long as the technical solution of the present application can be realized.
  • the negative electrode includes a negative electrode active material that can accept and extract lithium ions.
  • the negative active material is selected from soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon-oxygen compound, silicon-carbon composite, lithium titanate, metals that can form an alloy with lithium, and the like.
  • the material of the isolation membrane is not limited and can be selected according to actual needs.
  • the isolation film is a 12 ⁇ m polyethylene film (PE).
  • the positive electrode needs to be further processed into a positive pole piece for use.
  • the structure and preparation method of the positive pole piece are known in the art.
  • the positive electrode active material, conductive agent, binder, etc. are uniformly mixed in an organic solvent, and then coated on a metal (for example, Al foil), dried, and cold pressed to obtain a positive electrode pole piece.
  • the negative electrode needs to be further processed into a negative electrode piece for use.
  • the structure and preparation method of the negative electrode piece are known in the art.
  • the negative electrode active material, conductive agent, binder, thickener, etc. are mixed uniformly in a solvent, coated on a metal (such as Cu foil), dried, and cold pressed to obtain a negative electrode sheet .
  • the conductive agents, binders, thickeners, solvents, and organic solvents are all conventional reagents used in lithium ion batteries, and will not be repeated here.
  • the electrolyte of the present application After the electrolyte of the present application is applied to a lithium-ion battery, it can make the lithium-ion battery have better high-temperature cycle performance, high-temperature storage performance and lower DC impedance under high voltage, and enable the lithium-ion battery to have both better performance High voltage characteristics.
  • the dioxyborane group in the first additive will form a protective film on the surface of the positive electrode to stabilize the interface between the electrode and the electrolyte, thereby improving battery performance, and the alkenyl structure in the first additive
  • An electropolymerization reaction occurs on the surface of the positive electrode to form a passivation film with good conductivity, which inhibits the oxidation reaction of the electrolyte on the positive electrode and improves the rate charging performance of the lithium ion battery.
  • the second additive preferentially forms an SEI film on the surface of the negative electrode, and the oxygen atom of the second additive phosphoric acid cyclic anhydride has a strong electron withdrawing ability, so the alkenyl structure in the first additive is electrically
  • the hydrogen ions generated during the polymerization process can be electrostatically adsorbed on the oxygen atoms of the second additive phosphoric acid cyclic anhydride, thereby preventing the hydrogen ions from continuously reacting with the lithium salt and the SEI film formed on the surface of the negative electrode, and improving the storage performance and storage performance of the lithium ion battery. Cycle performance.
  • Fig. 3 shows a perspective view of a battery module according to an embodiment of the present application.
  • the battery module 4 according to the present application includes a plurality of battery cells 5 arranged in a longitudinal direction.
  • the battery module 4 can be used as a power source or an energy storage device.
  • the number of battery cells 5 in the battery module 4 can be adjusted according to the application and capacity of the battery module 4.
  • FIG. 4 shows a perspective view of a battery pack according to an embodiment of the present application
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4.
  • the battery pack 1 according to the present application includes an upper case 2, a lower case 3 and a battery module 4.
  • the upper case 2 and the lower case 3 are assembled together to form a space for accommodating the battery module 4.
  • the battery module 4 is placed in the space of the upper case 2 and the lower case 3 assembled together.
  • the output pole of the battery module 4 passes through one or between the upper case 2 and the lower case 3 to supply power to the outside or charge from the outside.
  • the battery pack 1 can be used as a power source or an energy storage device.
  • FIG. 6 shows a schematic diagram of a lithium ion battery as a power supply device according to an embodiment of the present application.
  • the device using the battery cell 5 is an electric vehicle.
  • the device using the battery cell 5 can be any electric vehicle except electric vehicles (for example, electric buses, electric trams, electric bicycles, electric motorcycles, electric scooters, electric golf carts, and electric trucks. ), electric ships, electric tools, electronic equipment and energy storage systems.
  • the electric vehicle may be an electric pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • the device provided in the fifth aspect of the present application may include the battery module 4 described in the third aspect of the present application.
  • the device provided in the fifth aspect of the present application may also include the fourth aspect of the present application.
  • the positive electrode active material LiNi 0.5 Mn 0.3 Co 0.2 O 2 , the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in the N-methylpyrrolidone solvent system at a weight ratio of 94:3:3. Afterwards, it is coated on the Al foil, dried and cold pressed to obtain a positive electrode piece.
  • SBR binder styrene-butadiene rubber
  • CMC thickener sodium carbon methyl cellulose
  • Lithium hexafluorophosphate is added to the organic solvent to obtain a lithium salt with a concentration of 1.0 mol/L, and then the first additive and the second additive are respectively added to the organic solvent, and after they are mixed uniformly, the electrolyte A and the electrolyte B are obtained. See Table 1 for the specific substances and respective usage amounts of the specific first additive and second additive.
  • a 12 ⁇ m polyethylene film (PE) is used as the separator.
  • PE polyethylene film
  • the electrolyte B prepared above is injected into the dried bare cell, packaged, allowed to stand, and then charged to 3.3V with a constant current of 0.02C, then charged to 3.6V with a constant current of 0.1C, and then shaped; After reshaping, inject electrolyte A into the cell, charge it to 4.4V with a constant current of 0.33C, then charge it with a constant voltage of 4.4V to a current of 0.05C, then discharge it to 2.8V with a constant current of 1C, and complete the lithium-ion battery.
  • the prepared soft-packed lithium-ion battery has a thickness of 4.0 mm, a width of 60 mm, and
  • the preparation method of the lithium ion battery of Comparative Examples 1-13 which is not in this application, is basically similar to that in Examples 1-14 of this application, except that only electrolyte B or A is added during the preparation of the lithium ion battery.
  • the volume expansion rate (%) of a lithium-ion battery stored at 85°C for 30 days (V1-V0)/V0 ⁇ 100%.
  • the capacity retention rate (%) of the lithium ion battery after being stored at 60°C for 90 days C1/C0 ⁇ 100%.
  • the DCR of a lithium ion battery at 25°C is equal to (U1-U2)/I, where I represents the current.
  • Table 1 shows the performance test results of the lithium ion batteries of Examples 1-14 of the present application and Comparative Examples 1-13 of the present application.

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Abstract

一种用于锂离子电池(5)的电解液、锂离子电池(5)、电池模块(4)、电池包(1)及装置。所述电解液包括有机溶剂、溶解在该有机溶剂中的电解质锂盐以及添加剂，其中所述添加剂包括第一添加剂和第二添加剂。所述第一添加剂包括如式（I）或式（II）所示的烯基二氧硼烷化合物，所述第二添加剂包括如式（III）所示的磷酸环酐。将电解液应用于锂离子电池(5)后，能够使锂离子电池(5)在高电压下具有较好的高温循环性能、高温存储性能以及较低的直流阻抗，并使锂离子电池(5)能兼具较好的高电压特性。

Description

用于锂离子电池的电解液、锂离子电池、电池模块、电池包及装置
相关申请的交叉引用
本申请要求享有于2019年10月18日提交中国专利局、申请号为201910994359.8、申请名称为“用于锂离子电池的电解液、锂离子电池、电池模块、电池包及装置”的中国专利申请的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及电池领域，尤其涉及一种用于锂离子电池的电解液、锂离子电池、电池模块、电池包及装置。
背景技术
锂电池相比铅酸电池、镍氢电池、镍镉电池具有高比能量密度、宽工作温度范围以及长循环寿命等优点，使其在市场上长期占据着主流地位。随着电子产品市场需求的扩大及动力、储能设备的发展，人们对锂离子电池能量密度提升的期望越来越高，开发具有高能量密度的锂离子电池已势在必行。
已知高电压锂离子电池是提高锂离子电池的能量密度的有效方法之一，因此工作电压在4.4V以上的锂离子电池已成为目前众多科研单位和企业研究的热点。然而在高电压下，正极氧化活性变高，非水电解液容易在正极表面发生电化学氧化反应，进而产生气体，同时，在高电压下正极材质中的过渡金属溶出迁移到负极消耗活性锂，导致锂离子的电化学性能恶化进而导致失效。
解决方法是向电解液中加入成膜添加剂，通过添加剂界面成膜作用来改善电解液和正极间的界面稳定。这些添加剂虽然能够在正极成膜，但会造成界面阻抗增加，导致电池中锂离子迁移扩散动力学性能降低，进而使得锂离子电池的存储性能和循环性能衰减。
发明内容
本申请部分实施例提供一种用于锂离子电池的电解液、锂离子电池、电池模块、电池包及装置。根据本申请，可使锂离子电池在高电压下具有较好的循环性能和存储性能，同时还提高了锂离子电池的倍率充电性能，有效解决了现有技术中存在的缺陷。
一方面，本申请提供一种用于锂离子电池的电解液，包括有机溶剂、溶解在该有机溶剂中的电解质锂盐以及添加剂，其中所述添加剂包括第一添加剂和第二添加剂。
所述第一添加剂包括如式I或式II所示的烯基二氧硼烷化合物：
Figure PCTCN2020120307-appb-000001
其中R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自H、含1～10个碳原子的饱和烷基，或者R 1与R 2或R 7与R 8联合形成具有至少一个双键且包含选自O、S、N中的至少一个杂原子的3～6元杂环结构。
所述第二添加剂包括如式III所示的磷酸环酐，其中R 11、R 12、R 13各自独立地选自H、含1～20个碳原子的饱和烷基或不饱和烷基，或者含6～18个碳原子以及至少一个苯环的基团。
第二方面，本申请提供一种锂离子电池，包括正极、负极、隔离膜，以及本申请第一方面所述的电解液。
第三方面，本申请还提供一种电池模块，包括本申请第二方面所述的锂离子电池。
第四方面，本申请还提供一种电池包，包括本申请第三方面所述的电池模块。
第五方面，本申请还提供一种装置，包括本申请第二方面所述的锂离子电池，所述锂离子电池用作所述装置的电源。
将本申请的电解液应用于锂离子电池后，能够使锂离子电池在高电压下 具有较好的高温循环性能、高温存储性能以及较低的直流阻抗，并使锂离子电池能兼具较好的高电压特性。包括本申请所述的锂离子电池的电池模块、电池包和装置也同样具有与所述锂离子电池相同的优势。
附图说明
图1是根据本申请一实施例的锂离子电池的立体图。
图2是图1所示锂离子电池的分解图。
图3是根据本申请一实施例的电池模块的立体图。
图4是根据本申请一实施例的电池包的立体图。
图5是图4所示电池包的分解图。
图6是根据本申请一实施例的锂离子电池作为电源装置的示意图。
其中，附图标记说明如下：
1电池包
2上箱体
3下箱体
4电池模块
5电池单体
51壳体
52电极组件
53顶盖组件
具体实施方式
下面将详细说明根据本申请的电解液及包含该电解液的锂离子电池、电池模块、电池包及装置。
为了简便，本文仅示例性地公开了一些数值范围。然而，任意下限可以与任何其它上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因此，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合、或与其它下限或上限组合形成未明确记载的范围。应理解，数值的列举仅作为示例，不应解释为穷尽。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”、“≤”、“≥”均包含本数，“至少一种”是指包括一种或多种，“一种或多种”中的“多种”含义是指两种或两种以上。
电解液
下文将详细描述根据本申请第一方面的用于锂离子电池的电解液。
根据本申请第一方面的用于锂离子电池的电解液，包括有机溶剂、溶解在该有机溶剂中的电解质锂盐以及添加剂，其中所述添加剂包括第一添加剂和第二添加剂。
所述第一添加剂包括如式I或式II所示的烯基二氧硼烷化合物：
Figure PCTCN2020120307-appb-000002
其中R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自H、1～10个碳原子的饱和或不饱和烷基，或者R 1与R 2或R 7与R 8联合形成具有至少一个双键且含有选自O、S、N中的至少一个杂原子的3～6元杂环结构。
在本申请一实施例中，R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自H。
在本申请一实施例中，R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自1～5个碳原子的饱和烷基。例如，包括但不限于，甲基、亚甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基、叔丁基、正戊基、1-甲基丁基、2-甲基丁基、3-甲基丁基、2-乙基丙基、1,1-二甲基丙基、1,3-二甲基丙基、2,2-二甲基丙基等。
在本申请一实施例中，R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自2～5个碳原子的不饱和烷基。例如，包括但不限于，乙烯基或丙烯基。
在本申请一实施例中，R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自 独立地选自甲基、亚甲基或乙基。
在本申请一实施例中，R 1与R 2或R 7与R 8联合形成具有至少一个双键且含有选自O、S、N中的至少一个杂原子的3～6元杂环结构。例如，包括但不限于如下所示的杂环结构：
Figure PCTCN2020120307-appb-000003
在本申请一实施例中，R 1与R 2或R 7与R 8形成如下所示的杂环结构：
Figure PCTCN2020120307-appb-000004
在本申请一实施例中，所述第一添加剂选自至少一种下述化合物：
2-异丙烯基-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼烷(化合物1-1)、
5,5-二甲基-2-(异丙烯-1-基)-1,3,2-二氧杂环己硼烷(化合物1-2)、
2-(2,5-二氢呋喃-3-基)-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼烷(化合物1-3)、
反式-2-丁烯-2-硼酸频哪醇酯(化合物1-4)、
2-(3,6-二氢-2H-噻喃-4-基)-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼烷(化合物1-5)，和
2-(1-苯乙烯基)-4,4,5,5-四甲基-(1,3,2)二氧杂戊硼烷(化合物1-6)。
Figure PCTCN2020120307-appb-000005
在本申请一实施例中，所述第一添加剂为式I所示的烯基二氧硼烷化合物，其中R 1、R 2、R 3、R 4、R 5各自独立地选自H、1～5个碳原子的饱和烷基，或者R 1与R 2联合形成具有至少一个双键且含有选自O、S、N中的至少一个杂原子的3～6元杂环结构。
在本申请一实施例中，式I所示的烯基二氧硼烷化合物选自至少一种下述化合物：
2-异丙烯基-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼烷(化合物1-1)、
5,5-二甲基-2-(异丙烯-1-基)-1,3,2-二氧杂环己硼烷(化合物1-2)，和
反式-2-丁烯-2-硼酸频哪醇酯(化合物1-4)。
所述第一添加剂可以在正负极界面参与成膜，其在正极形成的界面膜(通常称作SEI膜)可以有效抑制电解液在正极表面被氧化分解，这样一方面可以防止电解液氧化分解的产物沉积于正极界面而增大正极的界面阻抗，另一方面还可以防止电解液在正极界面氧化分解产气而导致界面电接触变差。
所述第二添加剂包括如式III所示的磷酸环酐，其中R 11、R 12、R 13各自独立地选自H、含1～20个碳原子的饱和烷基或不饱和烷基，或者含6～18个碳原子以及至少一个苯环的基团。
Figure PCTCN2020120307-appb-000006
在本申请一实施例中，R 11、R 12、R 13各自独立地选自H。
在本申请一实施例中，R 11、R 12、R 13各自独立地选自含1～5个碳原子的饱和烷基。例如，包括但不限于，甲基、亚甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基、叔丁基、正戊基、1-甲基丁基、2-甲基丁基、3-甲基丁基、2-乙基丙基、1,1-二甲基丙基、1,3-二甲基丙基、2,2-二甲基丙基等。
在本申请一实施例中，R 11、R 12、R 13各自独立地选自含1～5个碳原子的不饱和烷基。例如，包括但不限于，乙烯基、丙烯基、环丙烯基、1-丁烯基、顺-2-丁烯基、反-2-丁烯基、1-戊烯基、3-戊烯基等。
在本申请一实施例中，所述第二添加剂选自至少一种下述化合物：三甲基磷酸环酐(化合物2-1)、三乙基磷酸环酐(化合物2-2)、三丙基磷酸环酐(化合物2-3)，或三苯基磷酸环酐(化合物2-4)。
Figure PCTCN2020120307-appb-000007
其中-Ph表示苯基。
所述第二添加剂可与在负极界面形成的SEI膜中的主要成分发生复杂的交换反应，有助于在负极界面形成更稳定的SEI膜，并显著地降低负极界面的阻抗，使锂离子电池具有良好的功率性能。
将所述第一添加剂和第二添加剂联合使用后，第一添加剂可以在正负极界面成膜，防止电解液被氧化分解，有效抑制锂离子电池内部气体的产生，同时还可以进一步阻止第二添加剂在高温下被氧化分解。第二添加剂优先在负极还原成膜，可以改善第一添加剂在负极界面成膜阻抗较高的缺点，有效降低锂离子电池使用过程中的DCR增长，改善锂离子电池的功率性能。因此在两者的协同作用下，锂离子电池可具有良好的高温循环性能、高温存储性能以及较低的直流阻抗，并使锂离子电池能兼具较好的高电压特性。
进一步地，发明人发现，当所述第一添加剂在所述电解液中的含量为0.1wt％～3wt％时，由于所述第一添加剂的含量适中，形成的阴极钝化膜能够阻止电解液进一步反应，同时锂离子迁移阻力较低，对电池性能的改善效果显著，尤其有利于锂离子电池的倍率充电性能。因此，在本申请一实施例中，所述第一添加剂在所述电解液中的浓度为0.1wt％～3wt％，可选1wt％～1.5wt％。例如，所述第一添加剂在所述电解液中的浓度可以是0.1wt％、0.2wt％、0.5wt％、1wt％、1.5wt％、2wt％、2.5wt％或3wt％等，包括其中的任何数值及所有范围和子范围。例如0.5wt％～3wt％、0.5wt％～2wt％、1wt％～1.5wt％、1wt％～2wt％等。
进一步地，发明人发现，当所述第二添加剂在所述电解液中的含量在0.05wt％～2wt％范围内时时，有足够的所述第二添加剂吸附所述第一添加剂产生的氢离子，抑制氢离子的产生量；同时可以在负极表面形成良好的SEI膜，控制负极界面阻抗，优化锂离子电池的性能。因此，在本申请一实施例中，所述第二添加剂在所述电解液中的浓度为0.05wt％～2wt％，可选0.5wt％～1.5wt％。例如，所述第二添加剂在所述电解液中的浓度可以是0.05wt％、0.1wt％、0.2wt％、0.5wt％、1wt％、1.5wt％或2wt％等，包括其中的任何数值及所有范围和子范围。例如0.05wt％～2wt％、0.5wt％～1.5wt％、0.5wt％～2wt％、1wt％～1.5wt％、1wt％～2wt％等。
用于本申请的有机溶剂的种类没有具体限制，可根据实际需求适当选择，只要能够实现本申请的技术方案即可。作为例举，在本申请一实施例中，所述有机溶剂选自碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、氟代碳酸乙烯酯、碳酸甲乙酯、碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、1,4-丁内酯、丙酸甲酯、丁酸甲酯、乙酸乙酯、丙酸乙酯、丁酸乙酯中的一种或多种。
在本申请另一实施例中，所述有机溶剂还可选自丙烯酸甲酯、亚硫酸二甲酯、二乙基亚硫酸酯、酸酐、N-甲基吡咯烷酮、N-甲基甲酰胺、N-甲基乙酰胺、乙腈、N,N-二甲基甲酰胺、二甲亚砜、甲硫醚、四氢呋喃中的一种或几种。
当所述有机溶剂为两种或更多种的混合溶剂时，它们的比例没有特别限制，可根据实际需求适当选择，只要能够实现本申请的技术方案即可。例如，在本申请一实施例中，当所述有机溶剂包含两种不同有机溶剂时，它们可以按照质量比1:1、2:8、3:7、4:6、8:2、7:3、6:4等比例来混合使用。
所述有机溶剂在电解液中的含量没有具体限制，可根据实际需求适当选择，只要能够实现本申请的技术方案即可。作为例举，在本申请一实施例中，所述有机溶剂在所述电解液中的含量为65wt％～85wt％，可选70wt％～80wt％。例如所述有机溶剂在所述电解液中的含量可以是65wt％、70wt％、75wt％、80wt％、85wt％等，包括其中的任何数值及所有范围和子范围。
同样地，用于本申请的电解质锂盐没有具体限制，可根据实际需求适当选择，只要能够实现本申请的技术方案即可。在本申请一实施例中，所述电解质锂盐可选自路易斯酸与LiF的络合锂盐。例如，选自LiPF 6、LiBF 4、LiAsF 6、LiSbF 6、LiPF 4(CF 3) 2、LiPF 3(C 2F 5) 3、LiPF 3(CF 3) 3、LiPF 3(异-C 3F 7) 3和LiPF 5(异-C 3F 9)的一种或多种，可选LiPF 6、LiBF 4、LiAsF 6，更可选LiPF 6、LiBF 4。
在本申请一实施例中，所述电解质锂盐还可选自亚胺或甲基化的锂盐。例如，选自LiN(SO 2F) 2、LiN(SO 2CF 3) 2、LiN(SO 2C 2F 5) 2、(CF 2) 2(SO 2) 2NLi(环状)、(CF 2) 3(SO 2) 2NLi(环状)和LiC(SO 2CF 3) 3中的一种或多种，可选LiN(SO 2F) 2、LiN(SO 2CF 3) 2和/或LiN(SO 2C 2F 5) 2，更可选LiN(SO 2F) 2和/或LiN(SO 2CF 3) 2。
在本申请一实施例中，所述电解质锂盐还可选自含有S(＝O) 2O结构的锂盐。例如，选自LiSO 3F、LiCF 3SO 3、CH 3SO 4Li、C 2H 5SO 4Li、C 3H 7SO 4Li、三氟((甲磺酰)氧基)硼酸锂(LiTFMSB)、和五氟((甲磺酰)氧基)磷酸锂(LiPFMSP)中的一种或多种，可选LiSO 3F、CH 3SO 4Li、C 2H 5SO 4Li和/或LiTFMSB。
在本申请一实施例中，所述电解质锂盐还可选自含有P＝O或Cl＝O结构的锂盐。例如，选自LiPO 2F 2、Li 2PO 3F和LiClO 4中的一种或多种，可选LiPO 2F 2和/或Li 2PO 3F。
在本申请一实施例中，所述电解质锂盐还可选自以草酸盐配位体为阴离子的锂盐。例如，双[草酸根-O,O’]硼酸锂(LiBOB)、二氟[草酸根-O,O’] 硼酸锂、二氟双[草酸根-O,O’]磷酸锂(LiPFO)和四氟[草酸根-O,O’]磷酸锂中的一种或多种，可选LiBOB和/或LiPFO。
在本申请一实施例中，所述电解质锂盐还可选自LiPF 6、LiPO 2F 2、Li 2PO 3F、LiBF 4、LiSO 3F、LiTFMSB、LiN(SO 2F) 2、LiN(SO 2CF 3) 2、LiN(SO 2C 2F 5) 2、LiBOB、LiPFO和四氟[草酸根-O,O’]磷酸锂中的一种或多种，可选LiPF 6、LiBF 4、LiSO 3F、LiTFMSB、LiPO 2F 2、LiN(SO 2CF 3) 2、LiN(SO 2F) 2、LiBOB和LiPFO中的一种或多种，更可选LiPF 6。
所述电解质锂盐在电解液中的浓度没有具体限制，可根据实际需求适当选择，只要能够实现本申请的技术方案即可。在本申请一实施例中，所述电解质锂盐在电解液中的浓度为0.5M～2M(M＝mol·L -1)，可选0.8M～1.2M。例如，所述电解质锂盐在电解液中的浓度为0.5M、0.8M、1.0M、1.2M、1.5M或2.0M，包括其中的任何数值及所有范围和子范围。例如0.5M～2M、0.5M～1.5M、0.8M～1.2M、1.0M～2.0M、1.0M～1.5M等。
锂离子电池
接下来将详细描述根据本申请第二方面的锂离子电池。
根据本申请第二方面的锂离子电池，包括正极、负极、隔离膜，以及本申请第一方面所述的电解液。
图1示出了根据本申请一实施例的锂离子电池的立体图，图2是图1所示锂离子电池的分解图。参看图1和图2，根据本申请的锂离子电池5(以下简称电池单体5)包括壳体51、电极组件52、顶盖组件53、正极、负极、隔离膜以及电解液(未示出)。其中电极组件52收容于壳体51内，电极组件52的数量不受限制，可以为一个或多个。
需要说明的是，图1所示的电池单体5为罐型电池，但本申请并不限于此，电池单体5可以是袋型电池，即壳体51由金属塑膜替代且取消顶盖组件53。
所述正极没有具体限制，可根据实际需求适当选择，可以是通常用于锂离子电池的那些正极，只要能够实现本申请的技术方案即可。作为示例，在本申请一实施例中，所述正极包含能脱出、接受锂离子的正极活性物质。所述正极活性物质选自锂过渡金属复合氧化物，包括但不限于，锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化 物，这些锂过渡金属氧化物添加其他过渡金属或非过渡金属得到的化合物，以及上述物质的一种或几种的混合物等。
所述负极没有具体限制，可根据实际需求适当选择，可以是通常用于锂离子电池的那些负极，只要能够实现本申请的技术方案即可。作为示例，在本申请一实施例中，所述负极包含能接受、脱出锂离子的负极活性物质。所述负极活性物质选自软碳、硬碳、人造石墨、天然石墨、硅、硅氧化合物、硅碳复合物、钛酸锂，能与锂形成合金的金属等。
所述隔离膜的材质不受限制，可以根据实际需求进行选择。在本申请一实施例中，所述隔离膜为12μm的聚乙烯薄膜(PE)。
通常在具体应用中，需要将所述正极进一步加工成正极极片使用，所述正极极片的构造和制备方法是本领域已知的。例如，将所述正极活性物质、导电剂、粘结剂等在有机溶剂中混合均匀，凃敷于金属(例如Al箔)上经烘干、冷压，即可制得正极极片。
同样地，在具体应用中，需要将所述负极进一步加工成负极极片使用，所述负极极片的构造和制备方法是本领域已知的。例如，将所述负极活性物质、导电剂、粘结剂、增稠剂等在溶剂中混合均匀，凃敷于金属(例如Cu箔)上经烘干、冷压，即可制得负极极片。
所述导电剂、粘结剂、增稠剂、溶剂、有机溶剂均为用于锂离子电池的常规试剂，在此不再赘述。
本申请的电解液应用于锂离子电池后，能够使锂离子电池在高电压下具有较好的高温循环性能、高温存储性能以及较低的直流阻抗，并使锂离子电池能兼具较好的高电压特性。其原因是，一方面第一添加剂中的二氧硼烷基会在正极表面形成保护膜，来稳定电极与电解液之间的界面，从而提高电池性能，同时第一添加剂中的烯基结构在正极表面发生电聚合反应形成导电性良好的钝化膜，抑制电解液在正极上的氧化反应，改善锂离子电池的倍率充电性能。另一方面，通过电解液二次注液，第二添加剂优先在负极表面形成SEI膜，且第二添加剂磷酸环酐的氧原子的吸电子能力较强，因此第一添加剂中的烯基结构电聚合过程中产生的氢离子可以通过静电作用吸附在第二添加剂磷酸环酐的氧原子上，从而防止氢离子跟锂盐以及负极表面生成的SEI膜的持续反应，改善锂离子电池的存储性能和循环性能。
电池模块
接下来将简单描述根据本申请第三方面的电池模块。
图3示出了根据本申请一实施例的电池模块的立体图。参看图3，根据本申请的电池模块4包括多个电池单体5，所述多个电池单体5沿纵向排列。
电池模块4可以作为电源或储能装置。电池模块4中的电池单体5的数量可以根据电池模块4的应用和容量进行调节。
电池包
接下来将简单描述根据本申请第四方面的电池包。
图4示出了根据本申请一实施例的电池包的立体图，图5是图4所示电池包的分解图。参看图4和图5，根据本申请的电池包1包括上箱体2、下箱体3以及电池模块4。其中，上箱体2和下箱体3组装在一起并形成收容电池模块4的空间。电池模块4置于组装在一起的上箱体2和下箱体3的空间内。
电池模块4的输出极从上箱体2和下箱体3的其中之一或二者之间穿出，以向外部供电或从外部充电。
需要说明的是，电池包1采用的电池模块4的数量和排列可以依据实际需要来确定。电池包1可以作为电源或储能装置。
装置
接下来将简单描述根据本申请第五方面的装置。
图6示出了根据本申请一实施例的锂离子电池作为电源装置的示意图。仅作为例举，在图6中，使用电池单体5的装置为电动汽车。当然不限于此，使用电池单体5的装置可以为除电动汽车外的任何电动车辆(例如电动大巴、电动有轨电车、电动自行车、电动摩托车、电动踏板车、电动高尔夫球车、电动卡车)、电动船舶、电动工具、电子设备及储能系统。
所述电动汽车可以为电动纯电动车、混合动力电动车、插电式混合动力电动车。当然，依据实际使用形式，本申请第五方面提供的装置可包括本申请的第三方面所述的电池模块4，当然，本申请第五方面提供的装置也可包括本申请第四方面所述的电池包1。
实施例
下面结合具体实施例，进一步阐述本申请。应理解，下文的示例性实施例仅用于举例说明，并非对本申请进行限定。除非另有声明，实施例中使用的所有试剂都可商购或按照常规方法进行合成获得，并且可直接使用而无需进一步处理。实施例中未注明的实验条件采用常规条件、或采用材料供应商或设备供应商推荐的条件。
实施例1-14
按照下述方法制备本申请的实施例1-14。
(1)正极极片和负极极片的制备
将正极活性物质LiNi 0.5Mn 0.3Co 0.2O 2、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比94:3:3在N-甲基吡咯烷酮溶剂体系中充分搅拌混合均匀后，涂覆于Al箔上烘干、冷压，得到正极极片。
将负极活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂碳甲基纤维素钠(CMC)按照重量比95:2:2:1在去离子水溶剂体系中充分搅拌混合均匀后，涂覆于Cu箔上烘干、冷压，得到负极极片。
(2)电解液的制备
在充满氩气的手套箱中，将碳酸乙烯酯(EC)和碳酸二乙酯(DEC)以质量比EC:DEC＝20:80混合，作为有机溶剂。向该有机溶剂中加入六氟磷酸锂，得到浓度为1.0mol/L的锂盐，然后向其中分别加入第一添加剂和第二添加剂，各自混合均匀后，即为所述电解液A和电解液B。具体第一添加剂和第二添加剂的具体物质及各自使用量参见表1。
(3)锂离子电池的制备
以12μm的聚乙烯薄膜(PE)作为隔离膜。将制得的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极片中间，卷绕得到裸电芯，并焊接极耳，然后将裸电芯置于外包装中，将上述制备的电解液B注入到干燥后的裸电芯中，封装、静置，然后用0.02C恒流充电到3.3V，再以0.1C恒流充电到3.6V，整形；再向整形完后的电芯中注入电解液A，0.33C恒流充电至4.4V，之后4.4V恒压充电至电流为0.05C，然后用1C恒流放电至2.8V，容量测试，完成锂离子电池的制备。制得的软包锂离子电池的厚度4.0mm、宽度60mm、长度140mm。
对比例1-13
非本申请的对比例1-13的锂离子电池的制备方法与本申请的实施例1-14基本类似，除了锂离子电池的制备过程中仅添加电解液B或A之外。
性能测试
(1)锂离子电池的循环性能测试
在45℃下，将锂离子电池以1C恒流充电至4.4V后，之后4.4V恒压充电至电流为0.05C，然后用1C恒流放电至2.8V，上述为一个充放电循环。然后按照上述条件进行500次循环充电/放电测试。
锂离子电池循环500次后的容量保持率(％)＝(第500次循环的放电容量/首次循环的放电容量)×100％。
(2)锂离子电池的高温存储体积膨胀测试
在25℃下，将锂离子电池静置30分钟，之后以1C恒流充电至电压为4.4V，然后以4.4V恒压充电至电流为0.05C，此时测试锂离子电池的体积并记为V0；然后将满充的锂离子电池放入85℃恒温箱中，存储30天，采用排水法测试体积并记为V1。
锂离子电池85℃存储30天后的体积膨胀率(％)＝(V1-V0)/V0×100％。
(3)锂离子电池的高温存储性能测试
在25℃下，将锂离子电池以1C恒流充电至电压为4.4V，之后以4.4V恒压充电至电流为0.05C，然后以1C恒流放电至电压为2.8V，测试此时锂离子电池的放电容量，记为C0；之后将锂离子电池以1C恒流充电至电压为4.4V，之后以4.4V恒压充电至电流为0.05C，将锂离子电池放入60℃的恒温箱，保温90天，取出锂离子电池，以1C恒流放电至电压为2.8V，测试此时锂离子电池的放电容量，记为C1。
锂离子电池60℃存储90天后的容量保持率(％)＝C1/C0×100％。
(4)锂离子电池的常温直流阻抗(DCR)测试
在25℃下调整锂离子电池的荷电状态(SOC)至满充容量的50％，静置2小时，测试此时锂离子电池的电压并记为U1，然后以0.3C的倍率放电10s，测试锂离子电池放电后的电压并记为U2。
锂离子电池25℃的DCR＝(U1-U2)/I，I表示电流。
表1示出了本申请的实施例1-14和非本申请的对比例1-13的锂离子电池 的性能测试结果。
表1
Figure PCTCN2020120307-appb-000008
Figure PCTCN2020120307-appb-000009
从对比例2-7及对比例12的测试结果可以看出，在电解液中仅加入第一添加剂，锂离子电池的高温循环容量保持率、高温存储体积膨胀率、高温存储容量以及功率性能较差，原因是第一添加剂在电聚合过程中产生氢离子，氢离子跟LiFP 6和负极表面生成的SEI膜的持续反应，从而影响电性能。
从对比例1和对比例8-11、对比例13的测试结果可以看出，在电解液中仅加入第二添加剂，锂离子电池的高温循环容量保持率、高温存储体积膨胀率、高温存储容量以及功率性能也仍然较差，原因是没有正极成膜添加剂对正极的保护作用，导致非水电解液较易与正极反应，从而引起锂离子电池的性能变差。
从实施例1-14的测试结果可以看出，在电解液中同时加入第一添加剂和第二添加剂，可使锂离子电池同时具有较高的高温循环容量保持率、高温存储容量保持率以及较低的高温存储体积膨胀率，同时锂离子电池还具有较低的常温直流阻抗，即当将第一添加剂和第二添加剂协同联用时，既可以发挥第一添加剂烯基二氧硼烷化合物对锂离子电池高温性能的改善，同时可以阻止烯基二氧硼烷化合物对SEI膜的破坏。
从实施例1-3和对比例1可知，随着第一添加剂含量的增加，高温性能持续改善，但低温阻抗是先降低后增加，这可能是由于第一添加剂含量过大，导致其在正极络合后钝化层太厚，从而影响在锂离子在正极表面的传输，因此表现出较差的常温直流阻抗。
从实施例4-6、对比例1和对比例2可知，随着第二添加剂含量的增加，低温直流阻抗逐渐降低，但含量较高时，高温循环容量保持率和高温存储容量保持率会恶化。
根据上述说明书的揭示和教导，本领域技术人员还可以对上述实施方式进行变更和修改。因此，本申请并不局限于上面揭示和描述的具体实施方式，对本申请的一些修改和变更也应当落入本申请的权利要求的保护范围内。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明， 并不对本申请构成任何限制。

Claims (25)

  1. 一种用于锂离子电池的电解液，包括：
    有机溶剂，
    溶解在所述有机溶剂中的电解质锂盐，以及
    添加剂；
    其中，所述添加剂包括第一添加剂和第二添加剂；
    其中所述第一添加剂包括如式I或式II所示的烯基二氧硼烷化合物：
    Figure PCTCN2020120307-appb-100001
    其中R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自H，含1～10个碳原子的饱和烷基，或者R 1与R 2或R 7与R 8联合形成具有至少一个双键且含有选自O、S、N中的至少一个杂原子的3～6元杂环结构；
    所述第二添加剂包括如式III所示的磷酸环酐：
    其中R 11、R 12、R 13各自独立地选自H，含1～20个碳原子的饱和烷基或不饱和烷基，含6～18个碳原子以及至少一个苯环的基团。
  2. 根据权利要求1所述的电解液，其中，R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自H。
  3. 根据权利要求1所述的电解液，其中，R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自1～5个碳原子的饱和烷基。
  4. 根据权利要求1所述的电解液，其中，R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自2～5个碳原子的饱和烷基。
  5. 根据权利要求1所述的电解液，其中，R 1、R 2、R 3、R 4、R 5、R 6、R 7、R 8、R 9、R 10各自独立地选自甲基、亚甲基或乙基。
  6. 根据权利要求1所述的电解液，其中，R 1与R 2或R 7与R 8联合形成具有至少一个双键且含有选自O、S、N中的至少一个杂原子的3～6元杂环结构。
  7. 根据权利要求1所述的电解液，其中，所述第一添加剂选自下述化合物中的一种或多种：
    化合物1-1：2-异丙烯基-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼烷，
    化合物1-2：5,5-二甲基-2-(异丙烯-1-基)-1,3,2-二氧杂环己硼烷，
    化合物1-3：2-(2,5-二氢呋喃-3-基)-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼烷，
    化合物1-4：反式-2-丁烯-2-硼酸频哪醇酯，
    化合物1-5：2-(3,6-二氢-2H-噻喃-4-基)-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼，以及
    化合物1-6：2-(1-苯乙烯基)-4,4,5,5-四甲基-(1,3,2)二氧杂戊硼烷。
  8. 根据权利要求1所述的电解液，其中，所述第一添加剂为式Ⅰ所示的烯基二氧硼烷化合物，其中R 1、R 2、R 3、R 4、R 5各自独立地选自H、含1～5个碳原子的饱和烷基，或者R 1与R 2联合形成具有至少一个双键且含有选自O、S、N中的至少一个杂原子的3～6元杂环结构。
  9. 根据权利要求1所述的电解液，其中，所述第一添加剂选自下述化合物中的一种或多种：
    化合物1-1：2-异丙烯基-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼烷、
    化合物1-2：5,5-二甲基-2-(异丙烯-1-基)-1,3,2-二氧杂环己硼烷，
    化合物1-3：2-(2,5-二氢呋喃-3-基)-4,4,5,5-四甲基-1,3,2-二氧杂环戊硼烷，和化合物1-4：反式-2-丁烯-2-硼酸频哪醇酯。
  10. 根据权利要求1-9任一项所述的电解液，其中，所述第二添加剂包括如式III所示的磷酸环酐：其中R 11、R 12、R 13各自独立地选自H。
  11. 根据权利要求1-9任一项所述的电解液，其中，所述第二添加剂包括如式III所示的磷酸环酐：其中R 11、R 12、R 13各自独立地选自含1～5个碳原子的饱和烷基或不饱和烷基。
  12. 根据权利要求1-9任一项所述的电解液，其中，所述第二添加剂选自下述化合物中的一种或多种：
    化合物2-1：三甲基磷酸环酐，
    化合物2-2：三乙基磷酸环酐，
    化合物2-3：三丙基磷酸环酐，以及
    化合物2-4：三苯基磷酸环酐。
  13. 根据权利要求1-12任一项所述的电解液，其中，所述第一添加剂在所述电解液中的浓度为0.1wt％～3wt％。
  14. 根据权利要求1-12任一项所述的电解液，其中，所述第一添加剂在 所述电解液中的浓度为1wt％～1.5wt％。
  15. 根据权利要求1-14任一项所述的电解液，其中，所述第二添加剂在所述电解液中的浓度为0.05wt％～2wt％。
  16. 根据权利要求1-14任一项所述的电解液，其中，所述第二添加剂在所述电解液中的浓度为0.5wt％～1.5wt％。
  17. 根据权利要求1-16任一项所述的电解液，其中，所述电解质锂盐选自：LiPF 6、LiPO 2F 2、Li 2PO 3F、LiBF 4、LiSO 3F、LiTFMSB、LiN(SO 2F) 2、LiN(SO 2CF3) 2、LiN(SO 2C 2F 5) 2、LiBOB、LiPFO和四氟[草酸根-O,O’]磷酸锂中的一种或多种。
  18. 根据权利要求1-16任一项所述的电解液，其中，所述电解质锂盐选自：LiPF 6、LiBF 4、LiSO 3F、LiTFMSB、LiPO 2F 2、LiN(SO 2CF 3) 2、LiN(SO 2F) 2、LiBOB和LiPFO中的一种或多种。
  19. 根据权利要求1-18任一项所述的电解液，其中，所述电解质锂盐在电解液中的浓度为0.5M～2M。
  20. 根据权利要求1-18任一项所述的电解液，其中，所述电解质锂盐在电解液中的浓度为0.8M～1.2M。
  21. 一种锂离子电池，包括正极、负极、隔离膜，以及根据权利要求1-20任一项所述的电解液。
  22. 一种电池模块，包括根据权利要求21所述的锂离子电池。
  23. 一种电池包，包括根据权利要求22所述的电池模块。
  24. 一种装置，包括根据权利要求21所述的锂离子电池，所述锂离子电池用作所述装置的电源。
  25. 根据权利要求24所述的装置，其中，所述装置包括电动车辆、混合动力电动车辆、插电式混合动力电动车辆、电动自行车、电动踏板车、电动高尔夫球车、电动卡车、电动船舶、储能系统。
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