WO2024169403A1 - 一种电池 - Google Patents

一种电池 Download PDF

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Publication number
WO2024169403A1
WO2024169403A1 PCT/CN2023/141066 CN2023141066W WO2024169403A1 WO 2024169403 A1 WO2024169403 A1 WO 2024169403A1 CN 2023141066 W CN2023141066 W CN 2023141066W WO 2024169403 A1 WO2024169403 A1 WO 2024169403A1
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Prior art keywords
battery
electrolyte
additive
positive electrode
formula
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French (fr)
Inventor
邱亚明
王海
李素丽
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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Publication of WO2024169403A1 publication Critical patent/WO2024169403A1/zh
Priority to US19/264,006 priority Critical patent/US20250337017A1/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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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

  • the present invention belongs to the field of battery technology, and specifically relates to a battery, in particular a battery with good high-temperature cycle performance and good high-temperature storage performance.
  • lithium battery technology has made rapid progress, with higher and higher energy density and excellent cycle performance, so it has been widely used in various mobile electronic products, such as mobile phones, laptops, Bluetooth headsets, etc., and has been increasingly used in power tools, electric vehicles and other power fields. How to further improve the energy density of lithium batteries has become a research focus and hotspot.
  • Lithium cobalt oxide is a commonly used large-scale commercial high-voltage positive electrode material.
  • Increasing the battery charge and discharge voltage can not only increase the platform voltage, but also increase the positive electrode gram capacity, thereby increasing the battery energy density.
  • the increase in battery voltage will intensify the side reactions at the interface between the electrolyte and the positive and negative electrodes, thereby deteriorating the battery's cycle performance.
  • adding additives has become the most common and effective means.
  • the strategy of adding additives is increasingly difficult to sufficiently stabilize the high-temperature and high-voltage performance of the battery, and the development of new and effective positive electrode protection strategies has become increasingly important.
  • the battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, and the additive of the electrolyte includes phosphorous acid Trinitrile compounds and alkyl polynitrile compounds, through the synergistic effect between the surface density of the positive electrode and the electrolyte additives, can make the positive electrode have a very stable interface film and interface coordination effect, significantly improve the stability of the electrolyte and positive electrode interface, reduce the consumption of electrolyte and damage to the positive electrode structure during battery cycling, and significantly improve the high-temperature cycling performance and high-temperature storage performance of the battery under high voltage.
  • a battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the electrolyte comprises a lithium salt, an organic solvent and a first additive and a second additive, wherein the first additive comprises a trinitrile phosphite compound, and the second additive comprises an alkyl polynitrile compound;
  • the battery satisfies the following relationship: A ⁇ B/10;
  • A is the percentage of the total mass of the first additive and the second additive to the total mass of the electrolyte;
  • B is the surface density of the positive electrode sheet, in mg/cm 2 .
  • the first additive includes a trinitrile phosphite compound
  • the second additive includes an alkyl polynitrile compound
  • the two additives can act together on the positive electrode surface; specifically, the trinitrile phosphite compound contains both a phosphite functional group and an alkyl polynitrile functional group, wherein the phosphite functional group is easily oxidized at the positive electrode to form a dense protective film rich in phosphorus to protect the positive electrode, and the alkyl polynitrile functional group is brought into the positive electrode interface after film formation, and the alkyl polynitrile functional group and the transition metal at the positive electrode interface have a strong coordination effect, which can strengthen the protection of the positive electrode on the one hand, and make the formed phosphorus-containing protective film more solid on the other hand.
  • the alkyl polynitrile compound added at the same time can further coordinate with the transition metal at the weak or broken parts of the film formation, reducing the oxidation and decomposition
  • the present application has found that, in the case of no obvious electrolyte swelling in the battery, the higher the surface density B of the positive electrode sheet, the higher the corresponding content of the positive electrode active material, and the lower the amount of electrolyte relative to the content of the positive electrode active material.
  • Transition metal coordination it is impossible to reduce the consumption of electrolyte and the damage to the positive electrode structure during the battery cycle, and significantly deteriorate the high temperature cycle performance and high temperature storage performance of the battery at high voltage (4.53V), so it is necessary to increase the content of A.
  • the electrolyte additive can form a firm and stable interface protection on the positive electrode surface, and the amount of the electrolyte additive added can well match the positive electrode surface density, effectively improve the stability of the interface protection film on the positive electrode surface, significantly improve the stability of the electrolyte and positive electrode interface, reduce the consumption of electrolyte and the damage to the positive electrode structure during the battery cycle, and significantly improve the high temperature cycle performance and high temperature storage performance of the battery at high voltage (4.53V).
  • the battery satisfies the following relationship: A ⁇ 3/C;
  • A is the percentage of the total mass of the first additive and the second additive to the total mass of the electrolyte
  • C is the liquid retention coefficient of the battery, which is the ratio of the battery liquid retention mass (g) to the battery capacity (Ah).
  • the proportion of additives in the electrolyte must be increased. Studies have found that when A ⁇ 3/C, sufficient interface protection can be formed at the positive electrode interface, significantly improving the high-temperature cycle and high-temperature storage performance of the battery under high voltage.
  • the total mass of the first additive and the second additive accounts for a percentage A of the total mass of the electrolyte of 0.5% to 5%.
  • a percentage A of the total mass of the electrolyte 0.5% to 5%.
  • the mass proportion of the first additive and the second additive is within the above range, it is beneficial for the electrolyte additive to form a more firm and stable interface protection on the positive electrode surface, significantly improve the stability of the electrolyte and positive electrode interface, and effectively improve the high temperature cycle performance and high temperature storage performance of the battery at high voltage.
  • the surface density B of the positive electrode sheet is 5 mg/cm 2 to 30 mg/cm 2 .
  • the surface density of the positive electrode sheet is too high (such as greater than 30mg/ cm2 ), the positive electrode sheet will be too thick, resulting in poor kinetic performance of the battery and inability to charge and discharge normally. If the surface density of the positive electrode is too low (such as less than 5mg/ cm2 ), the overall energy density of the battery will be too low and cannot meet application requirements.
  • the liquid retention coefficient C is 1g/Ah-2g/Ah.
  • it is 1.0g/Ah, 1.1g/Ah, 1.2g/Ah, 1.3g/Ah, 1.4g/Ah, 1.5g/Ah, 1.6g/Ah, 1.7g/Ah, 1.8g/Ah, 1.9g/Ah, 2.0g/Ah.
  • Too low a liquid retention coefficient will result in too little electrolyte content (battery liquid retention quality), and the battery cycle will be significantly deteriorated.
  • Too high a liquid retention coefficient will result in too low an energy density of the battery, which cannot meet the needs of actual applications.
  • a simple test method for the liquid retention coefficient is as follows: charge the battery cell at 0.2C to the cut-off voltage and then discharge it at 0.2C to the cut-off voltage to obtain the battery cell capacity DC. Then weigh the entire battery cell as G1. Then disassemble the battery cell. After disassembly, soak the entire battery cell with a large amount of DMC (dimethyl carbonate). Then, fully dry the soaked battery cell and weigh it as G2.
  • the liquid retention coefficient is (G1-G2)/DC.
  • the battery satisfies the following relationship: 2A/3 ⁇ X ⁇ A/5
  • X is the percentage of the mass of the trinitrile phosphite compound to the total mass of the electrolyte.
  • the trinitrile phosphite compounds and the alkyl polynitrile compounds in the electrolyte can better exert a synergistic effect to form a sufficiently sufficient and firm protective layer.
  • Y is the percentage of the mass of the alkyl polynitrile compound to the total mass of the electrolyte.
  • the mass percentage X of the trinitrile phosphite compound to the total mass of the electrolyte is 0.1% to 3.3%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2% or 3.3%, preferably 0.5% to 2.5%.
  • the mass percentage of the trinitrile phosphite compound is, It can further strengthen the protection of the positive electrode and improve the high-temperature cycle performance and high-temperature storage performance of the battery under high voltage.
  • the trinitrile phosphite compound has a structural formula shown in formula (1):
  • the trinitrile phosphite compound includes the compounds of formula (2) to (9). At least one of the compounds shown:
  • the trinitrile phosphite compound can be purchased through commercial channels, or can be prepared by methods known in the art.
  • the alkyl polynitrile compound has a chemical formula shown in formula (10): R-(CN) n Formula (10)
  • R includes an alkyl group, and n is an integer greater than or equal to 3.
  • R includes a C 3-8 alkyl group, for example, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl or isomers thereof.
  • n is 3 or 4.
  • the alkyl polynitrile compound is a trinitrile compound or a tetranitrile compound, which can provide more nitrile-containing functional groups, further improve the coordination effect between the alkyl polynitrile compound and the transition metal at the positive electrode interface, strengthen the protection of the positive electrode, and further reduce the oxidative decomposition of the electrolyte at the uncovered sites of the protective film on the positive electrode surface.
  • the alkyl polynitrile compound includes 1,3,6-hexanetrinitrile (HTCN, NC(CH 2 ) 3 CH(CN)CH 2 CH 2 CN), 1,2,3-propanetricarbonitrile, and 1,2,2,3-tetracyanopropane.
  • HTCN 1,3,6-hexanetrinitrile
  • NC(CH 2 ) 3 CH(CN)CH 2 CH 2 CN 1,2,3-propanetricarbonitrile
  • 1,2,2,3-tetracyanopropane 1,3,6-hexanetrinitrile
  • the alkyl polynitrile compound can be purchased through commercial channels, or can be prepared by methods known in the art.
  • the electrolyte further includes a third additive.
  • the invention comprises at least one of adiponitrile (ADN), succinonitrile, fluoroethylene carbonate (FEC), 1,3-propane sultone (PS) and 1,3-propene sultone.
  • ADN adiponitrile
  • FEC fluoroethylene carbonate
  • PS 1,3-propane sultone
  • 1,3-propene sultone 1,3-propene sultone
  • the weight of the third additive is 0wt% to 15wt% of the total weight of the electrolyte, for example, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%.
  • the third additive in combination with the first additive and the second additive, can protect the positive electrode and the negative electrode at the same time, and improve the high temperature cycle performance and high temperature storage performance of the battery at high voltage.
  • the lithium salt includes one or more of lithium hexafluorophosphate (LiPF 6 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorooxalatoborate (LiDFOB), lithium bis(trifluoromethylsulfonyl imide), lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methyllithium or lithium bis(trifluoromethylsulfonyl)imide.
  • LiPF 6 lithium hexafluorophosphate
  • LiPO 2 F 2 lithium difluorooxalatoborate
  • LiDFOB lithium
  • the mass of the lithium salt accounts for 10-15wt% of the total mass of the electrolyte, for example, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%.
  • the organic solvent includes carbonate and/or carboxylate
  • the carbonate includes one or more of the following fluorinated or unsubstituted solvents: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), and ethyl methyl carbonate
  • the carboxylate includes one or more of the following fluorinated or unsubstituted solvents: propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, and ethyl butyrate.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder.
  • the mass percentage of each component in the positive electrode active material layer is: 80-99.8wt% of positive electrode active material, 0.1-10wt% of conductive agent, and 0.1-10wt% of binder.
  • the mass percentage of each component in the positive electrode active material layer is: 90-99.6wt% of positive electrode active material, 0.2-5wt% of conductive agent, and 0.2-5wt% of binder.
  • the mass percentage of each component in the negative electrode active material layer is: 80-99.8wt% of negative electrode active material, 0.1-10wt% of conductive agent, and 0.1-10wt% of binder.
  • the mass percentage of each component in the negative electrode active material layer is: 90-99.6wt% of negative electrode active material, 0.2-5wt% of conductive agent, and 0.2-5wt% of binder.
  • the conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.
  • the binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.
  • the negative electrode active material is at least one of a silicon-based negative electrode material and a carbon-based negative electrode material.
  • the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesophase carbon microbeads, hard carbon, and soft carbon.
  • the silicon-based negative electrode material includes at least one of a silicon-carbon negative electrode material and a silicon-oxygen negative electrode material.
  • the negative electrode active material is silicon carbon/graphite or silicon oxygen/graphite.
  • the positive electrode active material includes one or more of transition metal lithium oxide, lithium iron phosphate, and lithium manganese oxide; the chemical formula of the transition metal lithium oxide is Li1 + xNiyCozM (1-yz) O2 , wherein -0.1 ⁇ x ⁇ 1; 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, and 0 ⁇ y+z ⁇ 1; wherein M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.
  • the present disclosure provides a battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the additives of the electrolyte include a trinitrile phosphite compound and an alkyl polynitrile compound.
  • the battery can solve the problem of large side reactions between the electrolyte and the electrode interface of the battery under high voltage, and the high The problem of significantly deteriorated high-temperature cycling performance and high-temperature storage performance.
  • the positive electrode Adding an appropriate amount of electrolyte additives according to the surface density of the positive electrode can make the positive electrode have a very stable interface film and interface coordination effect, significantly improve the stability of the electrolyte and positive electrode interface, reduce the consumption of electrolyte and damage to the positive electrode structure during battery cycling, and significantly improve the high-temperature cycling performance and high-temperature storage performance of the battery under high voltage. It has been experimentally verified that the battery provided by the present invention has a cycle capacity retention rate of 80% at 45°C and the number of cycles can be as high as 562, and the thickness expansion rate can be as low as 5.9% when stored at 60°C.
  • Lithium-ion batteries are prepared by the following steps:
  • the positive electrode active materials of lithium cobalt oxide (LiCoO 2 ), polyvinylidene fluoride (PVDF), SP (superP) and carbon nanotubes (CNT) are mixed in a mass ratio of 96:2:1.5:0.5, N-methylpyrrolidone (NMP) is added, and the mixture is stirred under the action of a vacuum stirrer until the mixed system becomes a positive electrode active slurry with uniform fluidity; the positive electrode active slurry is evenly coated on both surfaces of an aluminum foil; the coated aluminum foil is dried, and then rolled and cut to obtain the desired positive electrode sheet, and the surface density of the positive electrode is B mg/cm 2 (the specific surface density is described in Table 1).
  • NMP N-methylpyrrolidone
  • the negative electrode active material silicon carbon/artificial graphite (containing 5% silicon carbon and 95% artificial graphite), carboxymethyl fiber Sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) are mixed in a mass ratio of 94.5:2.5:1.5:1:0.5, deionized water is added, and a negative electrode active slurry is obtained under the action of a vacuum mixer; the negative electrode active slurry is evenly coated on both surfaces of a copper foil; the coated copper foil is dried at room temperature, then transferred to an oven at 80°C for drying for 10 hours, and then cold pressed and cut to obtain a negative electrode sheet.
  • EC/PC/DEC/PP were mixed uniformly in a mass ratio of 10/20/40/30, and then 1 mol/L of fully dried lithium hexafluorophosphate (LiPF 6 ) was quickly added thereto.
  • LiPF 6 lithium hexafluorophosphate
  • 12 wt % of fluoroethylene carbonate, 2 wt % of 1,3-propane sultone, 1 wt % of adiponitrile, trinitrile phosphite compounds, and alkyl polynitrile compounds (specific amounts are described in Table 1) were added based on the total mass of the electrolyte, and stirred uniformly. After passing the moisture and free acid tests, the desired electrolyte was obtained.
  • the positive electrode sheet of step 1), the negative electrode sheet of step 2) and the separator are stacked in the order of positive electrode sheet, separator and negative electrode sheet, and then wound to obtain a battery cell; the battery cell is placed in an outer packaging aluminum foil, and the electrolyte of step 3) is injected into the outer packaging, and a lithium-ion battery is obtained after vacuum packaging, standing, forming, shaping, sorting and other processes.
  • the battery disclosed in the present invention has a charge and discharge range of 3.0 to 4.53V.
  • the lithium-ion batteries obtained in the embodiment and the comparative example were subjected to a 45° C. cycle performance test and a 60° C. storage performance test, respectively.
  • the test results are shown in Table 2.
  • the battery in Table 1 was charged and discharged at 45°C at a rate of 1C within the charge and discharge cut-off voltage range.
  • the discharge capacity of the first week of the test was calculated as x2mAh, and the discharge capacity of the Nth week was calculated as y2mAh.
  • Thickness expansion ratio [(thickness after storage - thickness before storage)/thickness before storage] ⁇ 100%.
  • the battery in Table 1 is charged to the cut-off voltage at 0.2C and then discharged to the cut-off voltage at 0.2C to obtain the cell capacity DC.
  • the cell is then weighed as G1.
  • the cell is then disassembled and soaked in a large amount of DMC.
  • the soaked cell is then fully dried and weighed as G2.
  • the liquid retention coefficient is (G1-G2)/DC.
  • Example 11a An equal amount of 1,2,3-propanetricarbonitrile replaces 1,3,6-hexanetricarbonitrile
  • Example 11b An equal amount of 1,2,2,3-tetracyanopropane replaces 1,3,6-hexanetrinitrile
  • Example 11b Equal amounts of 1,2,3-propanetricarbonitrile and 1,2,2,3-tetracyanopropane (mass ratio 1:1) were used to replace 1,3,6-hexanetricarbonitrile.
  • Example 6 The same method was carried out as in Example 6, except that the type of the trinitrile phosphite compound was changed;
  • Example 12a An equal amount of the compound represented by formula 5 is substituted for the compound represented by formula (2);
  • Example 12b An equal amount of the compound represented by formula 8 is substituted for the compound represented by formula (2);
  • Example 12c The compound represented by formula (2) accounts for 0.75 wt%, and the compound represented by formula (4) accounts for 0.75 wt%.
  • Example 13a Compared with Example 11a, the content of 1,2,3-propanetricarbonitrile is 1%;
  • Example 13b Compared with Example 11a, the content of 1,2,3-propanetricarbonitrile is 2.5%;
  • Example 13c Compared with Example 11b, the content of 1,2,2,3-tetracyanopropane is 1%;
  • Example 13d Compared with Example 11b, the content of 1,2,2,3-tetracyanopropane is 0.5%.
  • Example 12 The same method was carried out as in Example 12, except that the content of the trinitrile phosphite compound was changed;
  • Embodiment 14a Compared with Embodiment 12a, the content of the compound represented by Formula 5 is 0.5 wt %;
  • Embodiment 14b Compared with Embodiment 12a, the content of the compound represented by Formula 5 is 2.5wt%;
  • Embodiment 14c Compared with Embodiment 12b, the content of the compound represented by Formula 8 is 0.5 wt %;
  • Example 14d Compared with Example 12b, the content of the compound represented by Formula 8 is 2.5 wt%.
  • Example 15a The third additive is 8 wt% of fluoroethylene carbonate, 2 wt% of 1,3-propane sultone, and 2.5 wt% of adiponitrile; the total amount of the third additive is reduced;
  • Example 15b The third additive is 12 wt% of fluoroethylene carbonate, 2 wt% of 1,3-propane sultone, and 1 wt% of succinonitrile;
  • Example 15c The third additive is 14 wt% of fluoroethylene carbonate and 1 wt% of adiponitrile.
  • Example 12a From the comparison between Examples 2-3 and Example 6 and Examples 12a-12b, it can be seen that adjusting the structural formula of the trinitrile phosphite compound has a slight effect on the performance of the battery, but overall a high-voltage battery can be obtained.
  • the battery has good high-temperature storage performance and high-temperature cycle performance; among them, the cycle performance of Example 12a is better than that of Example 6, because the trinitrile phosphite compound of Formula 5 in Example 12a contains fluorine, which can improve the oxidation resistance of the trinitrile phosphite compound, and is more stable and long-lasting at the positive electrode.

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Abstract

一种电池，所述电池包括正极片、负极片、隔膜和电解液，所述电解液的添加剂包括亚磷酸三腈类化合物和烷基多腈类化合物，所述电池满足如下关系式：A≥B/10；其中，A为所述第一添加剂和第二添加剂的总质量占电解液总质量的百分含量；B为所述正极的面密度，单位mg/cm 2。所述电池能够解决高电压下电池的电解液和电极界面之间的副反应大，高电压下电池的高温循环性能和高温存储性能明显恶化的问题。通过根据正极的面密度加入合适量的电解液添加剂，能够使得正极具有非常稳定的界面膜和界面配位效应，显著提升电解液和正极界面的稳定性，降低电池循环过程中对电解液的消耗和对正极结构的破坏，显著改善电池在高电压下的高温循环性能和高温存储性能。

Description

一种电池 技术领域
本公开属于电池技术领域，具体涉及一种电池，特别是一种高温循环性能好、高温存储性能好的电池。
背景技术
近十年以来锂电技术突飞猛进，具备越来越高能量密度的同时还具备优秀的循环性能，从而在各种移动电子产品上得到广泛的应用，如手机、笔记本电脑、蓝牙耳机等，还在电动工具、电动汽车等动力领域得到越来越多的应用。如何进一步提高锂电池的能量密度，成为研究的重点和热点。
在不发生大的体系变更的情况下，电池能量密度的提高可通过简单的提升电池电压来实现。钴酸锂是常用的一种大规模商业化的高电压正极材料，提升电池充放电电压，不仅能提升平台电压，还能提升正极克容量，从而实现电池能量密度的增加。但是，电池电压的增加会使得电解液和正负极界面的副反应加剧，从而使得电池的循环性能出现恶化。
为了提升电池的高电压循环稳定性，除了调整电解液中的溶剂组分外，通过添加添加剂成为了最常用且有效的手段。但是，随着电池电压的进一步提升，通过添加添加剂的策略越来越难以起到足够的稳定电池高温高压性能的作用，开发新型有效正极保护策略就变得愈加重要。
发明内容
为了解决高电压下电池中电解液和电极界面之间的副反应大，高电压下电池的高温循环性能和高温存储性能明显恶化的问题，本公开提供一种电池。所述电池包括正极片、负极片、隔膜和电解液，所述电解液的添加剂包括亚磷酸 三腈类化合物和烷基多腈类化合物，通过正极的面密度和电解液添加剂之间的协同作用，能够使得正极具有非常稳定的界面膜和界面配位效应，显著提升电解液和正极界面的稳定性，降低电池循环过程中电解液的消耗和对正极结构的破坏，显著改善电池在高电压下的高温循环性能和高温存储性能。
本公开目的是通过如下技术方案实现的：
一种电池，所述电池包括正极片、负极片、隔膜和电解液，所述电解液包括锂盐、有机溶剂和第一添加剂和第二添加剂，所述第一添加剂包括亚磷酸三腈类化合物，所述第二添加剂包括烷基多腈类化合物；
所述电池满足如下关系式：
A≥B/10；
其中，A为所述第一添加剂和第二添加剂的总质量占电解液总质量的百分含量；B为所述正极片的面密度，单位mg/cm2。
根据本公开的实施方式，所述第一添加剂包括亚磷酸三腈类化合物，所述第二添加剂包括烷基多腈类化合物，两种添加剂能够共同作用在正极表面；具体的，所述亚磷酸三腈类化合物同时含有亚磷酸酯官能团和烷基多腈官能团，其中的亚磷酸酯官能团容易在正极被氧化形成富含磷的致密保护膜保护正极，同时成膜后会将烷基多腈官能团带入正极界面处，烷基多腈官能团和正极界面处的过渡金属之间具有较强的配位作用，一方面能够加强对正极的保护，另一方面还能够使得形成的含磷保护膜更加牢固。同时加入的烷基多腈类化合物可进一步在成膜薄弱部位或者破裂处与过渡金属进行配位，减少正极表面的保护膜未覆盖位点对电解液的氧化分解。
本申请研究发现，在电池不明显涨液的情况下，正极片的面密度B越高，对应的正极活性物质的含量越高，则电解液量相对正极活性物质的含量越低。当第一添加剂和第二添加剂的总质量占电解液总质量的百分含量保持不变时，正极片的面密度B越高，则第一添加剂和第二添加剂加入量相对正极活性物质的含量越低，若A<B/10，无法形成足够的正极保护(即含磷的正极保护膜和正极过 渡金属配位)，无法降低电池循环过程中电解液的消耗和对正极结构的破坏，显著恶化电池在高电压下(4.53V)的高温循环性能和高温存储性能，因此需要提高A的含量。当所述电池满足A≥B/10时，电解液添加剂才能够在正极表面形成牢固稳定的界面保护，且电解液添加剂的加入量能够很好地匹配正极面密度，有效提升正极表面界面保护膜的稳定性，显著提升电解液和正极界面的稳定性，降低电池循环过程中电解液的消耗和对正极结构的破坏，显著改善电池在高电压下(4.53V)的高温循环性能和高温存储性能。
根据本公开的实施方式，所述电池满足如下关系式：
A≥3/C；
其中，A为所述第一添加剂和第二添加剂的总质量占电解液总质量的百分含量；C为所述电池的保液系数，电池的保液系数是电池保液质量(g)与电池容量(Ah)的比值。
电池保液系数C越低，电池保液质量相对电池容量越低，电池保液质量相对正极活性物质的含量因此越低，要达到同样的正极保护效果，添加剂在电解液中的占比必须有所提升。研究发现，当A≥3/C时，才能够在正极界面形成足够的界面保护，显著改善电池高电压下的高温循环和高温存储性能。
根据本公开的实施方式，所述第一添加剂和第二添加剂的总质量占电解液总质量的百分含量A为0.5％～5％。例如为0.5％、0.6％、0.7％、0.8％、0.9％、1％、1.2％、1.5％、1.6％、1.8％、2.0％、2.2％、2.4％、2.5％、2.6％、2.7％、2.8％、3.0％、3.4％、3.5％、4％、4.5％、4.8％或5％。第一添加剂和第二添加剂的质量占比在上述范围时，有利于电解液添加剂在正极表面形成更牢固稳定的界面保护，显著提升电解液和正极界面的稳定性，有效改善电池在高电压下的高温循环性能和高温存储性能。
根据本公开的实施方式，所述正极片的面密度B为5mg/cm2～30mg/cm2。例如为5mg/cm2、6mg/cm2、7mg/cm2、8mg/cm2、9mg/cm2、10mg/cm2、12mg/cm2、13mg/cm2、15mg/cm2、18mg/cm2、20mg/cm2、22mg/cm2、23mg/cm2、24mg/cm2、 25mg/cm2、26mg/cm2、28mg/cm2或30mg/cm2。在一些实施方式中，所述正极片的面密度过高(如大于30mg/cm2)会导致正极片过厚，使得电池的动力学性能差而无法正常充放电，所述正极的面密度过低(如小于5mg/cm2)会导致电池整体能量密度过低，无法满足应用需求。
根据本公开的实施方式，所述保液系数C为1g/Ah-2g/Ah。例如为1.0g/Ah、1.1g/Ah、1.2g/Ah、1.3g/Ah、1.4g/Ah、1.5g/Ah、1.6g/Ah、1.7g/Ah、1.8g/Ah、1.9g/Ah、2.0g/Ah。保液系数太低会导致电解液含量(电池保液质量)太少，电池循环显著恶化。保液系数太高会导致电池的能量密度过低，无法满足实际应用需求。保液系数简单的测试方法如下：将电芯0.2C充电至截止电压后再0.2C放电至截止电压，得到电芯容量DC，后将电芯整体称重为G1,后将电芯拆解，拆解后电芯整体用大量DMC(碳酸二甲酯)浸泡，后将浸泡后的电芯充分烘干，再称重为G2，则保液系数为(G1-G2)/DC。
根据本公开的实施方式，所述电池满足如下关系式：
2A/3≥X≥A/5
其中，X为所述亚磷酸三腈类化合物的质量占电解液总质量的百分含量。
根据本公开的实施方式，当所述电池满足2A/3≥X≥A/5时，电解液中的亚磷酸三腈类化合物和烷基多腈类化合物之间能够更好的发挥协同作用，形成足够充分和牢固的保护层。
根据本公开的实施方式，所述电池满足如下关系式：
Y＝A-X
其中，Y为所述烷基多腈类化合物的质量占电解液总质量的百分含量。
根据本公开的实施方式，所述亚磷酸三腈类化合物的质量占电解液总质量的百分含量X为0.1％～3.3％，例如为0.1％、0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％、1.0％、1.1％、1.2％、1.3％、1.4％、1.5％、1.6％、1.7％、1.8％、1.9％、2％、2.1％、2.2％、2.3％、2.4％、2.5％、2.6％、2.7％、2.8％、2.9％、3.0％、3.1％、3.2％或3.3％，优选为0.5％～2.5％。优选亚磷酸三腈类化合物的质量占比， 能够进一步加强对正极的保护，提升电池在高电压下的高温循环性能和高温存储性能。
根据本公开的实施方式，所述亚磷酸三腈类化合物具有式(1)所示结构式：
式(1)中，R1、R2、R3相同或不同，彼此独立地包括无取代或任选被一个、两个或更多个Ra取代的C1-10亚烷基、C6-12亚芳基、-C1-10亚烷基-C(＝O)-O-C1-10亚烷基-；每一个Ra相同或不同，彼此独立地包括卤素、C1-10烷基。
根据本公开的实施方式，式(1)中，R1、R2、R3相同或不同，彼此独立地包括无取代或任选被一个、两个或更多个Ra取代的C1-6亚烷基、C6-8亚芳基、-C1-6亚烷基-C(＝O)-O-C1-6亚烷基-；每一个Ra相同或不同，彼此独立地包括卤素、C1-6烷基。
根据本公开的实施方式，式(1)中，R1、R2、R3相同或不同，彼此独立地包括无取代或任选被一个、两个或更多个Ra取代的C1-3亚烷基、亚苯基、-C1-3亚烷基-C(＝O)-O-C1-3亚烷基-；每一个Ra相同或不同，彼此独立地包括卤素、C1-3烷基。
根据本公开的实施方式，式(1)中，R1、R2、R3相同或不同，彼此独立地包括无取代或任选被一个、两个或更多个Ra取代的-CH2-、-CH2CH2-、-CH2CH2CH2-、-CH2CH(CH3)-、邻亚苯基、间亚苯基、对亚苯基、-CH2-C(＝O)-O-CH2-、-CH2CH2-C(＝O)-O-CH2CH2-；每一个Ra相同或不同，彼此独立地包括F、-CH3、-CH2CH3、-CH2CH2CH3、-CH(CH3)CH3。
根据本公开的实施方式，所述亚磷酸三腈类化合物包括式(2)～式(9)所 示的化合物中的至少一种：

根据本公开的实施方式，所述亚磷酸三腈类化合物可以是通过商业途径购买获得的，也可以是采用本领域已知的方法制备得到。
根据本公开的实施方式，所述烷基多腈类化合物具有式(10)所示化学式：
R-(CN)n   式(10)
式(10)中，R包括烷基，n为大于等于3的整数。
根据本公开的实施方式，式(10)中，R包括C3-8烷基，例如包括正丙基、正丁基、正戊基、正己基、正庚基、正辛基或它们的同分异构体基团。
根据本公开的实施方式，式(10)中，n为3或4。n为3或4时，烷基多腈类化合物为三腈化合物或四腈化合物，可以提供更多的含腈官能团，进一步提高烷基多腈化合物和正极界面处的过渡金属之间的配位作用，加强对正极的保护，进一步减少正极表面的保护膜未覆盖位点对电解液的氧化分解。
根据本公开的实施方式，所述烷基多腈类化合物包括1,3,6-己烷三腈(HTCN，NC(CH2)3CH(CN)CH2CH2CN)，1,2,3-丙三甲腈，1,2,2,3-四氰基丙烷。
根据本公开的实施方式，所述烷基多腈类化合物可以是通过商业途径购买获得的，也可以是采用本领域已知的方法制备得到。
根据本公开的实施方式，所述电解液还包括第三添加剂，所述第三添加剂 包括己二腈(ADN)、丁二腈、氟代碳酸乙烯酯(FEC)、1,3-丙烷磺酸内酯(PS)、1,3-丙烯磺酸内酯中的至少一种。
根据本公开的实施方式，所述第三添加剂的重量为所述电解液总重量的0wt％～15wt％，例如为0.5wt％、1wt％、1.5wt％、2wt％、2.5wt％、3wt％、3.5wt％、4wt％、4.5wt％、5wt％、5.5wt％、6wt％、6.5wt％、7wt％、7.5wt％、8wt％、9wt％、10wt％、11wt％、12wt％、13wt％、14wt％或15wt％。第三添加剂与第一添加剂和第二添加剂组合作用下，可以同时保护正极和负极，改善电池在高电压下的高温循环性能和高温存储性能。
根据本公开的实施方式，所述锂盐包括六氟磷酸锂(LiPF6)、二氟磷酸锂(LiPO2F2)、二氟草酸硼酸锂(LiDFOB)、双三氟甲基磺酰亚胺锂、二氟双草酸磷酸锂、四氟硼酸锂、双草酸硼酸锂、六氟锑酸锂、六氟砷酸锂、二(三氟甲基磺酰)亚胺锂、二(五氟乙基磺酰)亚胺锂、三(三氟甲基磺酰)甲基锂或二(三氟甲基磺酰)亚胺锂中的一种或两种以上。
根据本公开的实施方式，所述锂盐的质量占电解液总质量的百分含量的10～15wt％，例如为10wt％、11wt％、12wt％、13wt％、14wt％或15wt％。
根据本公开的实施方式，所述有机溶剂包括碳酸酯和/或羧酸酯，所述碳酸酯包括氟代或未取代的下述溶剂中的一种或几种：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二甲酯、碳酸二乙酯(DEC)、碳酸甲乙酯；所述羧酸酯包括氟代或未取代的下述溶剂中的一种或几种：乙酸丙酯、乙酸正丁酯、乙酸异丁酯、乙酸正戊酯、乙酸异戊酯、丙酸丙酯(PP)、丙酸乙酯(EP)、丁酸甲酯、正丁酸乙酯。
根据本公开的实施方式，所述正极片包括正极集流体和涂覆在正极集流体一侧或两侧表面的正极活性物质层，所述正极活性物质层包括正极活性物质、导电剂和粘结剂。
根据本公开的实施方式，所述正极活性物质层中各组分的质量百分含量为：80-99.8wt％的正极活性物质、0.1-10wt％的导电剂、0.1-10wt％的粘结剂。
优选地，所述正极活性物质层中各组分的质量百分含量为：90-99.6wt％的正极活性物质、0.2-5wt％的导电剂、0.2-5wt％的粘结剂。
根据本公开的实施方式，所述负极活性物质层中各组分的质量百分含量为：80-99.8wt％的负极活性物质、0.1-10wt％的导电剂、0.1-10wt％的粘结剂。
优选地，所述负极活性物质层中各组分的质量百分含量为：90-99.6wt％的负极活性物质、0.2-5wt％的导电剂、0.2-5wt％的粘结剂。
根据本公开的实施方式，所述导电剂包括导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、碳纳米管、金属粉、碳纤维中的至少一种。
根据本公开的实施方式，所述粘结剂包括羧甲基纤维素钠、丁苯胶乳、聚四氟乙烯、聚氧化乙烯中的至少一种。
根据本公开的实施方式，所述负极活性物质为硅基负极材料和碳基负极材料中的至少一种。
根据本公开的实施方式，所述碳基负极材料包括人造石墨、天然石墨、中间相碳微球、硬碳、软碳中的至少一种。
根据本公开的实施方式，所述硅基负极材料包括硅碳负极材料、硅氧负极材料中的至少一种。
根据本公开的实施方式，所述负极活性物质为硅碳/石墨或硅氧/石墨。
根据本公开的实施方式，所述的正极活性物质包括过渡金属锂氧化物、磷酸铁锂、锰酸锂中的一种或几种；所述过渡金属锂氧化物的化学式为Li1+xNiyCozM(1-y-z)O2，其中，-0.1≤x≤1；0≤y≤1，0≤z≤1，且0≤y+z≤1；其中，M为Mg、Zn、Ga、Ba、Al、Fe、Cr、Sn、V、Mn、Sc、Ti、Nb、Mo、Zr中的一种或几种。
本公开的有益效果：
本公开提供一种电池，所述电池包括正极片、负极片、隔膜和电解液，所述电解液的添加剂包括亚磷酸三腈类化合物和烷基多腈类化合物。所述电池能够解决高电压下电池的电解液和电极界面之间的副反应大，高电压下电池的高 温循环性能和高温存储性能明显恶化的问题。根据正极的面密度加入合适量的电解液添加剂，能够使得正极具有非常稳定的界面膜和界面配位效应，显著提升电解液和正极界面的稳定性，降低电池循环过程中对电解液的消耗和对正极结构的破坏，显著改善电池在高电压下的高温循环性能和高温存储性能。经过实验验证发现，本公开提供的电池在45℃循环容量保持率80％循环圈数可高达562，60℃存储下厚度膨胀率可低至5.9％。
具体实施方式
下文将结合具体实施例对本公开的技术方案做更进一步的详细说明。应当理解，下列实施例仅为示例性地说明和解释本公开，而不应被解释为对本公开保护范围的限制。凡基于本公开上述内容所实现的技术均涵盖在本公开旨在保护的范围内。
下述实施例中所使用的实验方法如无特殊说明，均为常规方法；下述实施例中所用的试剂、材料等，如无特殊说明，均可从商业途径得到。
在本公开的描述中，需要说明的是，术语“第一”、“第二”等仅用于描述目的，而并非指示或暗示相对重要性。
锂离子电池通过以下步骤制备得到：
1)正极片制备
将正极活性物质钴酸锂(LiCoO2)、聚偏氟乙烯(PVDF)、SP(superP)和碳纳米管(CNT)按照96:2:1.5:0.5的质量比进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌，直至混合体系成均一流动性的正极活性浆料；将正极活性浆料均匀涂覆于铝箔的两个表面；将涂覆好的铝箔烘干，然后经过辊压、分切得到所需的正极片，正极的面密度为B mg/cm2时(具体面密度如表1所述)。
2)负极片制备
将负极活性物质硅碳/人造石墨(含5％硅碳和95％人造石墨)、羧甲基纤维 素钠(CMC-Na)、丁苯橡胶、导电炭黑(SP)和单壁碳纳米管(SWCNTs)按照质量比94.5:2.5:1.5:1:0.5进行混合，加入去离子水，在真空搅拌机作用下获得负极活性浆料；将负极活性浆料均匀涂覆在铜箔的两个表面；将涂覆好的铜箔在室温下晾干，随后转移至80℃烘箱干燥10h，然后经过冷压、分切得到负极片。
3)电解液的制备
在充满氩气的手套箱中(H2O<0.1ppm，O2<0.1ppm)，将EC/PC/DEC/PP按照10/20/40/30的质量比混合均匀，然后往其中快速加入1mol/L的充分干燥的六氟磷酸锂(LiPF6)，溶解后加入基于电解液总质量12wt％的氟代碳酸乙烯酯，2wt％的1,3-丙烷磺酸内酯，1wt％的己二腈，亚磷酸三腈类化合物，以及烷基多腈类化合物(具体用量如表1所述)，搅拌均匀，经过水分和游离酸检测合格后，得到所需的电解液。
4)锂离子电池的制备
将步骤1)的正极片、步骤2)的负极片和隔离膜按照正极片、隔离膜和负极片的顺序层叠设置后，再进行卷绕得到电芯；将电芯置于外包装铝箔中，将步骤3)的电解液注入外包装中，经过真空封装、静置、化成、整形、分选等工序，获得锂离子电池。本公开电池充放电范围为3.0～4.53V。
对实施例和对比例获得的锂离子电池分别进行45℃循环性能测试和60℃存储性能测试，测试结果见表2。
1)45℃循环性能测试
将表1的电池在45℃下按照1C的倍率在充放电截止电压范围内进行充放电循环，测试第1周的放电容量计为x2mAh，第N周的放电容量计为y2mAh；第N周的容量除以第1周的容量，得到第N周的循环容量保持率R＝y2/x2，记录循环容量保持率R为80％时对应的循环周数。
2)60℃存储性能测试
将表1的电池在25℃下按照1C的倍率充电到截止电压，截止电流0.025C，静置5min，测试锂离子电池的厚度(以此为存储前的厚度)。充满电的电芯/电池在 (60±2)℃条件下开路搁置35天，储存35天后在室温条件下开路搁置2h，测存储后的冷厚度，计算锂离子电池厚度膨胀率：
厚度膨胀率＝[(存储后厚度‐存储前厚度)/存储前厚度]×100％。
3)保液系数简单的测试
将表1的电池在0.2C充电至截止电压后再0.2C放电至截止电压，得到电芯容量DC，后将电芯整体称重为G1,后将电芯拆解，拆解后电芯整体用大量DMC浸泡，后将浸泡后的电芯充分烘干，再称重为G2，则保液系数为(G1-G2)/DC。
表1实施例和对比例的电池的组成
实施例11组
参照实施例6进行，不同之处在于，改变烷基多腈类化合物的种类；
实施例11a：等量的1,2,3-丙三甲腈替代1,3,6-己烷三腈；
实施例11b：等量的1,2,2,3-四氰基丙烷替代1,3,6-己烷三腈；
实施例11b：等量的1,2,3-丙三甲腈和1,2,2,3-四氰基丙烷(质量比1:1)替代1,3,6-己烷三腈。
实施例12组
参照实施例6进行，不同之处在于，改变亚磷酸三腈类化合物的种类；
实施例12a：等量的式5所示的化合物替代式(2)所示的化合物；
实施例12b：等量的式8所示的化合物替代式(2)所示的化合物；
实施例12c：式(2)所示的化合物占比为0.75wt％，式(4)所示的化合物占比为0.75wt％。
实施例13组
参照实施例11组进行，不同之处在于，改变烷基多腈类化合物的含量；
实施例13a：与实施例11a相比，1,2,3-丙三甲腈的含量占比为1％；
实施例13b：与实施例11a相比，1,2,3-丙三甲腈的含量占比为2.5％；
实施例13c：与实施例11b相比，1,2,2,3-四氰基丙烷的含量占比为1％；
实施例13d：与实施例11b相比，1,2,2,3-四氰基丙烷的含量占比为0.5％。
实施例14组
参照实施例12组进行，不同之处在于，改变亚磷酸三腈类化合物的含量；
实施例14a：与实施例12a相比，式5所示的化合物的含量占比为0.5wt％；
实施例14b：与实施例12a相比，式5所示的化合物的含量占比为2.5wt％；
实施例14c：与实施例12b相比，式8所示的化合物的含量占比为0.5wt％；
实施例14d：与实施例12b相比，式8所示的化合物的含量占比为2.5wt％。
实施例15组
参照实施例6进行，不同之处在于，不同之处在于，改变第三添加剂的种类 和含量；
实施例15a：第三添加剂为8wt％的氟代碳酸乙烯酯，2wt％的1,3-丙烷磺酸内酯，2.5wt％的己二腈；第三添加剂的总量占比变小；
实施例15b：第三添加剂为12wt％的氟代碳酸乙烯酯，2wt％的1,3-丙烷磺酸内酯，1wt％的丁二腈；
实施例15c：第三添加剂为14wt％的氟代碳酸乙烯酯，1wt％的己二腈。
表2实施例和对比例的锂离子电池的循环性能测试结果

从上述性能测试结果可以看出，对比例1-2、4-6中没有同时加入1,3,6-己烷三腈和亚磷酸三腈类化合物，获得的电池的高温循环性能和高温存储明显较实施例1明显变差。对比例3中同时加入1,3,6-己烷三腈和亚磷酸三腈类化合物，性能较对比例1有所提升，但是由于添加剂的加入量不足，难以形成足够的正极保护，性能也明显较差。
从实施例1-8对比可以看出，当电解液体系中加入1,3,6-己烷三腈和亚磷酸三腈类化合物后，获得的电池的高温循环性能和高温存储性能较对比例1-6得到显著提升，但随着两种添加剂含量的增加，对电池的高温循环性能和高温存储性能的改善幅度逐步降低。实施例9的正极片的面密度过大，导致电池的各项性能较实施例1-8显著恶化。但是实施例9与对比例7相比，电池的高温循环性能和高温存储性能同样得到了显著的提升。
从对比例8和实施例1可以看出，当保液系数过低，电池各项性能显著恶化。从实施例2和实施例10则可以看出，当保液系数有所提升时，电池循环会有轻微提升。
从实施例2-3，以及实施例6和实施例12a-12b的对比可以看出，调整亚磷酸三腈类化合物的结构式对电池的性能略有影响，但是整体上都会获得具有高电 压下较好的高温存储性能和高温循环性能的电池；其中，实施例12a的循环性能比实施例6的好，因为实施例12a中式5的亚磷酸三腈类化合物含氟，能够提升亚磷酸三腈类化合物的耐氧化性提升，在正极更加稳定长效。同时，从实施例2-5对比可以看出，当实施例4和5的电池中，电解液中的第一添加剂的加入量占比不满足2A/3≥X≥A/5时，电池的高温循环性能和高温存储性能比实施例2和3略差一些。
以上，对本公开的实施方式进行了说明。但是，本公开不限定于上述实施方式。凡在本公开的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本公开的保护范围之内。

Claims (15)

  1. 一种电池，所述电池包括正极片、负极片、隔膜和电解液，所述电解液包括锂盐、有机溶剂和第一添加剂和第二添加剂，所述第一添加剂包括亚磷酸三腈类化合物，所述第二添加剂包括烷基多腈类化合物；
    所述电池满足如下关系式：
    A≥B/10；
    其中，A为所述第一添加剂和第二添加剂的总质量占电解液总质量的百分含量；B为所述正极的面密度，单位mg/cm2。
  2. 根据权利要求1所述的电池，其特征在于，所述电池还满足如下关系式：
    A≥3/C；
    其中，A为所述第一添加剂和第二添加剂的总质量占电解液总质量的百分含量；C为所述电池的保液系数，为电池保液质量(g)与电池容量(Ah)的比值。
  3. 根据权利要求1或2所述的电池，其特征在于，所述第一添加剂和第二添加剂的总质量占电解液总质量的百分含量A为0.5％～5％。
  4. 根据权利要求1-3任一项所述的电池，其特征在于，所述正极的面密度B为5mg/cm2～30mg/cm2。
  5. 根据权利要求2-4任一项所述的电池，其特征在于，所述保液系数C为1g/Ah-2g/Ah。
  6. 根据权利要求1-5任一项所述的电池，其特征在于，所述电池满足如下关系式：
    2A/3≥X≥A/5
    其中，X为所述亚磷酸三腈类化合物的质量占电解液总质量的百分含量。
  7. 根据权利要求6所述的电池，其特征在于，所述亚磷酸三腈类化合物的质量占电解液总质量的百分含量X为0.1％～3.3％。
  8. 根据权利要求1-7任一项所述的电池，其特征在于，所述亚磷酸三腈类化 合物具有式(1)所示结构式：
    式(1)中，R1、R2、R3相同或不同，彼此独立地包括无取代或任选被一个、两个或更多个Ra取代的C1-10亚烷基、C6-12亚芳基、-C1-10亚烷基-C(＝O)-O-C1-10亚烷基-；每一个Ra相同或不同，彼此独立地包括卤素、C1-10烷基。
  9. 根据权利要求8所述的电池，其特征在于，式(1)中，R1、R2、R3相同或不同，彼此独立地包括无取代或任选被一个、两个或更多个Ra取代的C1-6亚烷基、C6-8亚芳基、-C1-6亚烷基-C(＝O)-O-C1-6亚烷基-；每一个Ra相同或不同，彼此独立地包括卤素、C1-6烷基。
  10. 根据权利要求8或9所述的电池，其特征在于，式(1)中，R1、R2、R3相同或不同，彼此独立地包括无取代或任选被一个、两个或更多个Ra取代的-CH2-、-CH2CH2-、-CH2CH2CH2-、-CH2CH(CH3)-、邻亚苯基、间亚苯基、对亚苯基、-CH2-C(＝O)-O-CH2-、-CH2CH2-C(＝O)-O-CH2CH2-；每一个Ra相同或不同，彼此独立地包括F、-CH3、-CH2CH3、-CH2CH2CH3、-CH(CH3)CH3。
  11. 根据权利要求1-10任一项所述的电池，其特征在于，所述亚磷酸三腈类化合物包括式(2)～式(9)所示的化合物中的至少一种：

  12. 根据权利要求1-11任一项所述的电池，其特征在于，所述烷基多腈类化合物具有式(10)所示化学式：
    R-(CN)n    式(10)
    式(10)中，R包括烷基，n为大于等于3的整数。
  13. 根据权利要求12所述的电池，其特征在于，式(10)中，R包括C3-8烷基；和/或，n为3或4。
  14. 根据权利要求1-13任一项所述的电池，其特征在于，所述烷基多腈类化合物包括1,3,6-己烷三腈、1,2,3-丙三甲腈，1,2,2,3-四氰基丙烷中的至少一种。
  15. 根据权利要求1-14任一项所述的电池，其特征在于，所述电解液还包括第三添加剂，所述第三添加剂包括己二腈(ADN)、丁二腈、氟代碳酸乙烯酯(FEC)、1,3-丙烷磺酸内酯(PS)、1,3-丙烯磺酸内酯中的至少一种；
    优选地，所述第三添加剂的重量为所述电解液总重量的0wt％～15wt％。
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