CN109428078B - Battery with a battery cell - Google Patents

Battery with a battery cell Download PDF

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CN109428078B
CN109428078B CN201710744106.6A CN201710744106A CN109428078B CN 109428078 B CN109428078 B CN 109428078B CN 201710744106 A CN201710744106 A CN 201710744106A CN 109428078 B CN109428078 B CN 109428078B
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battery
lithium
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electrolyte
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CN109428078A (en
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张翠平
韩昌隆
张明
张�浩
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Contemporary Amperex Technology Co Ltd
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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
    • 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
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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

Abstract

The application relates to the field of energy storage materials, in particular to a battery. The battery comprises a positive pole piece, a negative pole piece, an isolating membrane and electrolyte, wherein the isolating membrane is arranged between the positive pole piece and the negative pole piece; the anode active material is a ternary anode material, and the additive comprises a cyclic phosphazene compound and fluorobisoxalato phosphate. The electrolyte in the battery can reduce the corrosion of HF to the positive interface and protect the positive interface; meanwhile, the increase of positive and negative interface impedance is inhibited, and the cycle storage life is prolonged, so that the high-voltage cycle performance and the high-temperature storage performance of the battery are improved.

Description

Battery with a battery cell
Technical Field
The application relates to the field of energy storage materials, in particular to a battery.
Background
In the rapidly developing information age, the demand for electronic products such as mobile phones, notebooks, cameras, and the like has increased year by year. Batteries, particularly lithium ion secondary batteries, are used as working power supplies of electronic products, have the characteristics of high energy density, no memory effect, high working voltage and the like, and are gradually replacing the traditional Ni-Cd and MH-Ni batteries.
The ternary cathode material has the advantages of high energy density, high discharge voltage, good low-temperature performance and the like, but the following two problems are generally existed: firstly, the circulation performance of battery is relatively poor, can not satisfy people to the requirement of long-life battery, secondly the battery is more serious at high temperature storage in-process flatulence, has the safety risk, and capacity decline is relatively fast in the high temperature storage in addition.
Disclosure of Invention
In order to solve the above problems, the present applicant has conducted intensive studies and, as a result, found that: when the electrolyte is added with the cyclophosphazene compound and the fluorobisoxalato phosphate, the high-voltage cycle performance and the high-temperature storage performance of the battery adopting the ternary cathode material can be well improved, and therefore the application is completed.
The application provides a battery, which comprises a positive pole piece, a negative pole piece, a separation film and electrolyte, wherein the separation film is arranged between the positive pole piece and the negative pole piece;
the structural formula of the positive active material is LiaNixCoyMzO2M is at least one of Mn, Al, Zr, Ti, V, Mg, Fe, Mo and B, a is more than or equal to 0.95 and less than or equal to 1.2, x>0，y>0，z>0, and x + y + z is 1;
the additive comprises a cyclic phosphazene compound and fluorobisoxalates;
the cyclic phosphazene compound is at least one selected from compounds shown in formula I;
Figure BDA0001389752840000021
wherein R is11、R12、R13、R14、R15、R16Each independently selected from halogen, halogen substituted C1～C12Alkyl, halogen substituted C1～C12An alkoxy group; and R is11、R13、R15At least one of them being C1～C12An alkoxy group.
The technical scheme of the application has at least the following beneficial effects:
the battery adopts a ternary positive electrode active material, and simultaneously, the cyclic phosphazene compound and the fluorobisoxalates are added into the electrolyte, so that the corrosion of HF to the positive electrode interface is reduced, and the positive electrode interface is protected; meanwhile, the increase of positive and negative interface impedance is inhibited, and the improvement of the cycle storage life is facilitated, so that the high-voltage cycle performance and the high-temperature storage performance of the battery adopting the ternary cathode active material are improved.
Detailed Description
The present application is further illustrated with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.
The embodiment of the application provides a battery, which comprises a positive pole piece, a negative pole piece, a separation film and electrolyte, wherein the separation film is arranged between the positive pole piece and the negative pole piece, the positive pole piece contains a positive active material, and the electrolyte comprises an organic solvent, electrolyte and an additive. The components of the batteries of the examples of the present application will be described below.
[ Positive electrode sheet ]
The positive pole piece contains a positive active material, and the positive active material adopted in the embodiment of the application is a ternary positive material. The ternary cathode material has the advantages of high energy density, high discharge voltage, good low-temperature performance and the like, and is suitable for power batteries. Further optionally, the charge cut-off voltage of the battery in the embodiment of the application is 4.2V-4.9V.
The structural formula of the ternary cathode material in the embodiment of the application is LiaNixCoyMzO2M is at least one of Mn, Al, Zr, Ti, V, Mg, Fe, Mo and B, a is more than or equal to 0.95 and less than or equal to 1.2, x>0，y>0，z>0, and x + y + z is 1;
further optionally, the ternary cathode material in the embodiments of the present application is selected from LiNi1/3Co1/3Mn1/3O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.6Co0.2Mn0.2O2、LiNi0.8Co0.1Mn0.1O2、LiNi0.5Co0.25Mn0.25O2At least one of (1).
The positive plate also comprises a binder and a conductive agent, positive slurry containing a positive active material, the binder and the conductive agent is coated on a positive current collector, and the positive plate is obtained after the positive slurry is dried.
[ electrolyte ]
In the electrolyte of the battery of the embodiment of the application, the additive comprises a cyclic phosphazene compound and fluorobisoxalato phosphate; wherein the cyclic phosphazene compound is at least one selected from compounds shown in formula I;
Figure BDA0001389752840000031
wherein R is11、R12、R13、R14、R15、R16Each independently selected from halogen, halogen substituted C1～C12Alkyl, halogen substituted C1～C12An alkoxy group; and R is11、R13、R15At least one of them being C1～C12An alkoxy group.
In the process of rapid charging of the lithium ion battery, lithium ions are rapidly removed from the positive electrode, enter the electrolyte, pass through the diaphragm, enter the negative electrode, and are embedded with lithium. In this case, lithium is highly active and therefore reacts with carbon of the negative electrode to form Li very easily2CO3And Solid substances such as LiO, LiOH and the like cover the surface of the negative electrode to form a 'film', namely a Solid Electrolyte Interface (SEI) film, and the excellent SEI film can effectively prevent solvent molecules from continuously reducing on the surface of the electrode and prevent solvated lithium ions from being inserted into graphite layers, so that the negative electrode is protected. The electrolyte additive is thus intended to contribute to the film formation on the electrode surface.
With the use of high voltage and ternary positive active materials, suitable additives must be employed to improve electrolyte kinetics and high temperature storage issues. In view of this, in the embodiment of the present application, a cyclic phosphazene compound and a fluorobisoxalato phosphate are added to an electrolyte solution at the same time. The cyclic phosphazene compound structure adopted in the embodiment of the application contains at least one alkoxy, the alkoxy is an electron donating group, the electron cloud density on a cyclic phosphazene double bond can be obviously increased, the nucleophilic ability of the cyclic phosphazene compound is increased, and an electrophilic addition reaction is generated between HF and an N ═ P double bond, which are generated by an electrolyte side reaction, so that HF is removed, the corrosion of HF to a positive electrode interface is reduced, and the positive electrode interface is indirectly protected.
The increase of DCR in the cyclic storage process mainly comes from the side reaction of the electrolyte on the positive and negative electrode interfaces, the generated by-products are deposited on the surfaces of the electrodes, and the impedance of the by-products is generally higher, so that the total DCR of the battery is increased.
In conclusion, the combination use of the cyclophosphazene compound and the fluorobisoxalato phosphate reduces the corrosion of HF to the positive electrode interface, protects the positive electrode interface, and thus can improve the storage performance of the battery of the ternary positive electrode material under the condition of high voltage; meanwhile, the increase of positive and negative interface impedance is inhibited, thereby being more beneficial to the improvement of the cycle storage life.
Further optionally, in formula I, R11、R12、R13、R14、R15、R16Each independently selected from halogen, halogen substituted C1～C6Alkyl, halogen substituted C1～C6An alkoxy group; and R is11、R13、R15At least one of them being C1～C6An alkoxy group.
Further optionally, in formula I, R11、R12、R13、R14、R15、R16Each independently selected from halogen, halogen substituted C1～C3Alkyl, halogen substituted C1～C3An alkoxy group; and R is11、R13、R15At least one of them being C1～C6An alkoxy group.
In the compounds represented by formula I, halogen-substituted alkyl or alkoxy includes partial substitution, i.e., the hydrogen atom on alkyl or alkoxy is partially substituted with halogen; halogen-substituted alkyl or alkoxy also includes all substitution, i.e., all hydrogen atoms on the alkyl or alkoxy are substituted with halogen;
halogen may be selected from fluorine, chlorine, bromine and preferably fluorine.
Further alternatively, the cyclic phosphazene compound is selected from at least one of compounds represented by the following structural formulae, without being limited thereto:
Figure BDA0001389752840000051
further optionally, the fluorobisoxalato phosphate is at least one selected from the group consisting of compounds represented by formula II;
Figure BDA0001389752840000052
wherein R is21、R22Each independently selected from halogen, halogen substituted C1～C12Alkyl, halogen substituted C1～C12An alkoxy group;
A+represents lithium ion, sodium ion or potassium ion, and is preferably lithium ion.
Further optionally, R21、R22Each independently selected from halogen, halogen substituted C1～C6Alkyl, halogen substituted C1～C6An alkoxy group.
Further optionally, the fluorobisoxalato phosphate is selected from at least one of the compounds represented by the following structural formula;
Figure BDA0001389752840000053
(lithium bistrifluoromethylbisoxalato phosphate, compound B1);
Figure BDA0001389752840000054
(lithium bis-difluoromethyl bis-oxalate phosphate, compound B2);
Figure BDA0001389752840000055
(lithium difluorobis (oxalato) phosphate, compound B3);
Figure BDA0001389752840000061
(lithium bis-pentafluoroethyl bis-oxalate phosphate, compound B4).
Further optionally, the content of the cyclophosphazene compound in the electrolyte is 0.001% -3% by mass. If the content of the cyclic phosphazene compound is too low, it is difficult to suppress hydrogen fluoride, and its improving effect on the electrolyte is not significant, and if the content of the cyclic phosphazene compound is too high, the cycle performance of the battery is deteriorated.
The upper limit of the content range of the cyclophosphazene compound in the electrolyte solution is selected from 3%, 2.5%, 2%, 1.8%, 1.6%, 1.5%, 1.3%, 1.2%, 1%, 0.8%, 0.6% and the lower limit is selected from 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.3%, 0.5%. More preferably, the content of the cyclic phosphazene compound in the electrolyte is 0.1-2%.
Further optionally, the mass percentage of the fluorobisoxalato phosphate in the electrolyte is 0.001% -3%. If the content of the fluorobisoxalato phosphate is too low, the improvement effect on the positive electrode is not obvious, and if the content of the fluorobisoxalato phosphate is too high, the performance of the battery is not linearly improved.
In the embodiment of the present invention, the upper limit of the mass percentage range of the fluorobisoxalato phosphate in the electrolyte solution is selected from 3%, 2.5%, 2%, 1.8%, 1.6%, 1.5%, 1.3%, 1.2%, 1%, 0.8%, 0.6%, and the lower limit thereof is selected from 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.3%, 0.5%. More preferably, the percentage content of the fluorobisoxalato phosphate in the electrolyte is 0.1-2%.
In the electrolyte of the embodiment of the present application, the electrolyte is not selected from fluorobisoxalato phosphate.
When the battery is a lithium ion battery, the electrolyte is selected from at least one of lithium hexafluorophosphate, lithium bis (trifluoromethyl) sulfonimide, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium hexafluoroarsenate, lithium bis (oxalato) borate, and lithium perchlorate, and more preferably is lithium hexafluorophosphate.
The electrolyte of the embodiment of the present application may further include other additives, including but not limited to:
1. dinitrile compounds: at least one compound selected from the compounds shown in the formula III-1;
Figure BDA0001389752840000062
wherein R is31Selected from substituted or unsubstituted C1～C12An alkylene group; the substituent is selected from halogen and C1～C3Alkyl radical, C2～C4An alkenyl group.
Specifically, the dinitrile compound may be selected from at least one of glutaronitrile and adiponitrile, but is not limited thereto.
The dinitrile compound has a negatively charged cyano group (CN-), and can stabilize metal ions of a cathode material through complexation, inhibit the dissolution of the metal ions, and thus improve the electrical performance of the battery.
2. Cyclic carbonate compound containing unsaturated bond: at least one compound selected from the compounds shown in the formula III-2;
Figure BDA0001389752840000071
R32selected from alkenyl-substituted C1～C6Alkylene, substituted or unsubstituted C2～C6An alkenylene group.
The unsaturated bond-containing cyclic carbonate compound is selected from at least one of the following compounds, and the specific structural formula is as follows:
Figure BDA0001389752840000072
the double bond contained in the unsaturated bond-containing cyclic carbonate compound may undergo a reduction reaction at the anode to generate a polymer protective film, i.e., participate in the generation of the SEI film.
3. Cyclic sulfate compound: at least one compound selected from the compounds shown in the formula III-3,
Figure BDA0001389752840000073
R33selected from substituted or unsubstituted C1～C6Alkylene, substituted or unsubstituted C2～C6Alkenylene, the substituent being selected from halogen, C1～C3Alkyl radical, C2～C4An alkenyl group.
The cyclic sulfate compound is selected from at least one of vinyl sulfate (DTD for short), allyl sulfate (TMS for short) and 4-methyl ethylene sulfate (PLS for short), and the specific structural formula is as follows;
Figure BDA0001389752840000081
the cyclic sulfate compound is a good film forming additive for the positive and negative electrode interfaces, and can reduce film forming impedance.
4. Sultone compounds: at least one compound selected from the compounds shown in the formula III-4;
Figure BDA0001389752840000082
wherein R is34Selected from substituted or unsubstituted C1～C6Alkylene, substituted or unsubstituted C2～C6Alkenylene, the substituent being selected from halogen, C1～C3Alkyl radical, C2～C4An alkenyl group.
Specifically, the sultone compound is selected from at least one of 1, 3-propane sultone (PS for short) and 1, 3-propylene sultone (PES for short), and the specific structural formula is as follows;
Figure BDA0001389752840000083
the sultone compound can participate in film formation of positive and negative electrodes, so that high-temperature storage gas generation is remarkably inhibited.
5. Lithium difluorophosphate:
lithium difluorophosphate participates in the film formation of the positive electrode interface, and the film formation is relatively stable, so that the high-temperature storage performance of the battery is improved.
The dosage of the additive can be between 0.01 and 3 percent.
In the electrolyte of the embodiment of the present application, the organic solvent is a non-aqueous organic solvent, and the organic solvent may be a compound having 1 to 8 carbon atoms and containing at least one ester group, and may be an ether compound.
Specifically, the organic solvent is selected from C1～C8Chain carbonate and C1～C8Cyclic carbonate, C1～C8Chain carboxylate, Ring C1～C8Cyclic carboxylic acid ester, C2～C8At least one of ethers.
As C1～C8Examples of the chain carbonate include: at least one of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate and ethyl propyl carbonate;
as C1～C8Examples of the cyclic carbonates include: at least one of ethylene carbonate, propylene carbonate, butylene carbonate and fluoroethylene carbonate;
as C1～C8Examples of the chain carboxylic acid ester include: at least one of methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, and ethyl butyrate;
as C1～C8Examples of cyclic carboxylic acid esters include: 1, 4-butyrolactone.
As C2～C8As an example of the ether, tetrahydrofuran is listed.
In the examples of the present application, C can be used as the organic solvent1～C8Chain carbonate and C1～C8An organic solvent for the cyclic carbonate is used.
Further, an organic solvent used in combination of Ethylene Carbonate (EC) and diethyl carbonate (DEC) can be selected.
In the embodiment of the present application, the preparation method of the electrolyte may be a conventional method, for example, the organic solvent, the lithium salt and the additive may be mixed uniformly.
[ negative electrode sheet ]
The negative electrode sheet contains a negative electrode active material, a binder and a conductive agent, wherein the negative electrode active material can be selected from carbon materials such as hard carbon, natural graphite, artificial graphite, soft carbon, carbon black, acetylene black, carbon nanotubes, graphene, carbon nanofibers and the like. Examples of the other negative electrode active material include simple substances of elements that are alloyed with sodium, such as Si, Ge, Pb, In, Zn, H, Ca, Sr, Ba, Ru, and Rh, and oxides and carbides containing these elements. However, the material is not limited to these materials, and conventionally known materials that can be used as a negative electrode active material of a sodium ion battery can be used. These negative electrode active materials may be used alone or in combination of two or more.
And coating negative electrode slurry containing a negative electrode active material, a binder and a conductive agent on a negative electrode current collector, and drying the negative electrode slurry to obtain a negative electrode sheet.
[ separator ]
In the above battery, the specific kind of the separator is not particularly limited and may be any separator material used in the existing battery, such as polyethylene, polypropylene, polyvinylidene fluoride, and multi-layer composite films thereof, but not limited thereto.
The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
In the following examples and comparative examples, reagents, materials and instruments used were commercially available or synthetically available, unless otherwise specified. The reagents used were specifically as follows:
additive:
cyclic phosphazene compound: the aforementioned compounds A1 to A4; fluorobisoxalato phosphate: the aforementioned compounds B1 to B4; other additives: glutaronitrile, ethylene sulfate (DTD), Vinylene Carbonate (VC), 1, 3-Propane Sultone (PS), lithium difluorophosphate;
lithium salt: lithium hexafluorophosphate (LiPF)6)。
Organic solvent: ethylene Carbonate (EC), diethyl carbonate (DEC).
Positive electrode active material: the nickel cobalt lithium manganate ternary material.
And (3) isolation film: a16 μm polyethylene porous polymer film (PE) was used as a separator.
(1) Preparation of the electrolyte
Adding the additive into a nonaqueous organic solvent according to a certain mass ratio in a glove box filled with argon (the water content is less than 10ppm, the oxygen content is less than 1ppm), adding a proper amount of other additives, uniformly mixing, and slowly adding a proper amount of lithium salt (LiPF) into the nonaqueous organic solvent (EC: DEC ═ 3:7)6) And after the lithium salt is completely dissolved, obtaining an electrolyte with the lithium salt concentration of 1mol/L, namely the electrolyte.
(2) Preparing a positive plate:
the positive electrode active material, the conductive agent Super P and the binder polyvinylidene fluoride (PVDF) are prepared into positive electrode slurry in N-methyl pyrrolidone (NMP). The solid content of the positive electrode slurry is 50 wt%, and the mass ratio of the positive electrode active material, Super P and PVDF in the solid components is 6:2:2: 2. Coating the positive electrode slurry on a current collector aluminum foil, drying at 85 ℃, cold-pressing, trimming, cutting into pieces, slitting, and drying at 85 ℃ for 4h to obtain the positive electrode plate.
(3) Preparing a negative plate:
graphite as a negative active material is uniformly mixed with a conductive agent Super P, a thickening agent CMC and a binding agent Styrene Butadiene Rubber (SBR) in deionized water to prepare negative slurry. The solid content in the negative electrode slurry is 53 wt%, and the mass ratio of graphite, Super P, CMC and Styrene Butadiene Rubber (SBR) as a binder in the solid components is 6:2:2: 2. Coating the negative electrode slurry on a current collector copper foil, drying at 85 ℃, then carrying out cold pressing, trimming, cutting and slitting, and drying for 12h at 120 ℃ under a vacuum condition to prepare the negative electrode sheet.
(4) Preparing a lithium ion battery:
the prepared positive plate, the prepared isolating membrane and the prepared negative plate are sequentially stacked, the isolating membrane is positioned between the positive plate and the negative plate to play a role in isolating the positive plate from the negative plate, a naked battery cell is obtained by winding, a tab is welded, the naked battery cell is placed in an outer package, the prepared electrolyte is injected into the dried battery cell, and the lithium ion battery is packaged, stood, formed, shaped, subjected to capacity test and the like, so that the preparation of the lithium ion battery (the thickness of the soft package lithium ion battery is 4.0mm, the width of the soft package lithium ion battery is 60mm, and the length of the soft package lithium ion battery is 140mm) is completed.
In examples 1 to 20 and comparative examples 1 to 5, the solvent and additive ratios used are shown in table 1, wherein the additive ratio in table 1 is a mass percentage calculated based on the total mass of the electrolyte; the positive electrode active material in the positive electrode sheet is shown in table 1.
TABLE 1
Figure BDA0001389752840000111
Figure BDA0001389752840000121
Note: "/" indicates no addition of any material.
Next, a test procedure of the lithium ion battery is explained.
(1) Cycle performance testing of lithium ion batteries
Under the condition of room temperature, the lithium ion battery is charged to 4.2V at a constant current of 4C, then charged to a current of 0.05C at a constant voltage of 4.2V, and then discharged to 2.8V at a constant current of 1C, and the process is a charge-discharge cycle. And calculating the capacity retention rate of the lithium ion battery after 300 cycles by taking the capacity of the first discharge as 100%. The capacity retention (%) after 300 cycles of the lithium ion battery was equal to the discharge capacity at 300 cycles/the capacity at the first discharge × 100%.
(2) High-temperature gas production performance test of lithium ion battery
Charging the lithium ion battery to 4.2V at a constant current of 1C at room temperature, then charging the lithium ion battery to a current of 0.05C at a constant voltage of 4.2V, after the battery is fully charged, testing the volume of the battery by adopting a drainage method, recording, storing the battery at 80 ℃, taking out the battery after 24 hours, standing for 60 minutes at room temperature, testing the volume by adopting the drainage method within 1 hour after cooling to the room temperature, recording, and storing and testing according to the steps until 30 days. And calculating the volume expansion rate of the battery along with the storage time by taking the volume of the battery tested before storage as a reference.
The lithium ion battery stored at 80 ℃ for a certain number of days, and then the volume expansion ratio (%) (battery volume measured after storage on the N-th day/battery volume measured before storage) -1.
(3) 60 ℃ storage life test of lithium ion battery
The lithium ion battery was charged at 60 ℃ to 4.2V at 1C, then charged at a constant voltage of 4.2V to a current of 0.05C, and then the capacity of the battery was measured every 30 days, and based on the capacity measured at the first time, the capacity retention (%) — capacity obtained in the nth test/capacity measured at the first time × 100%.
TABLE 2 high-temperature storage gassing and capacity retention rate of lithium ion batteries
Figure BDA0001389752840000131
Figure BDA0001389752840000141
From the test results in table 1, it can be seen that, compared with the storage gas generation, the capacity retention after cycling, and the capacity retention after storage obtained by the test in comparative examples 1 to 5, the performances of examples 1 to 20 are greatly improved, which indicates that the use of the cyclic phosphazene compound having an alkoxy group in combination with lithium fluorobisoxalato phosphate can form a relatively stable interfacial film at the positive and negative electrode interfaces, thereby effectively improving the dynamic performance of the battery.
According to examples 1 to 6, it is understood that the specific properties of fluorobisoxalato phosphate are gradually improved as the content thereof is gradually increased. In comparative example 4, lithium fluorobisoxalato phosphate has a high content and is easily oxidized at high temperature to cause side reactions, thereby deteriorating the high-temperature storage performance. Meanwhile, in the embodiment 1, the content of lithium fluorobisoxalato phosphate is too small, so that a complete interface film cannot be formed on the positive electrode and the negative electrode, and the improvement effect on the performance of the battery is limited.
From examples 7 to 12, it is understood that the respective properties are gradually improved as the content of the cyclic phosphazene compound having an alkoxy group is gradually increased. In comparative example 5, the content of the cyclic phosphazene compound is high, so that the viscosity of the electrolyte is high, and the dynamic performance of the electrolyte is deteriorated. The lower content of alkoxy pentafluorocyclophosphane in example 7 was not sufficient to remove hydrofluoric acid generated in the electrolyte, and the improvement effect on the battery performance was limited.
Comparative example 2 lithium fluorobisoxalato phosphate alone, although it can form a film at the positive electrode interface, could not suppress hydrogen fluoride generated in the electrolyte, i.e., hydrogen fluoride could not suppress destruction of the electrode interface to deteriorate the battery performance.
Comparative example 3 addition of the cyclic phosphazene compound having an alkoxy group alone can trap HF and suppress corrosion of the electrolyte to the electrode interface, but since a good interfacial film is not formed at the positive electrode, occurrence of side reactions cannot be effectively suppressed, and thus the room temperature cycle performance is poor.
Although the present application has been described with reference to preferred embodiments, it is not intended to limit the scope of the claims, and many possible variations and modifications may be made by one skilled in the art without departing from the spirit of the application.

Claims (10)

1. A battery comprises a positive pole piece, a negative pole piece, a separation film and electrolyte, wherein the separation film is arranged between the positive pole piece and the negative pole piece;
it is characterized in that the preparation method is characterized in that,
the structural formula of the positive active material is LiaNixCoyMzO2M is at least one of Mn, Al, Zr, Ti, V, Mg, Fe, Mo and B, a is more than or equal to 0.95 and less than or equal to 1.2, x>0，y>0，z>0, and x + y + z is 1;
the additive comprises a cyclic phosphazene compound and fluorobisoxalates;
the cyclic phosphazene compound is at least one selected from compounds shown in formula I;
Figure FDA0001389752830000011
wherein R is11、R12、R13、R14、R15、R16Each independently selected from halogen, halogen substituted C1～C12Alkyl, halogen substituted C1～C12An alkoxy group; and R is11、R13、R15At least one of them being C1～C12An alkoxy group.
2. The battery according to claim 1, wherein the fluorobisoxalato phosphate is at least one selected from the group consisting of compounds represented by formula II;
Figure FDA0001389752830000012
wherein R is21、R22Each independently selected from halogen, halogen substituted C1～C12Alkyl, halogen substituted C1～C12An alkoxy group;
A+represents lithium ion, sodium ion or potassium ion, and is preferably lithium ion.
3. The battery according to claim 1, wherein the cyclic phosphazene compound is selected from at least one of compounds represented by the following structural formulae;
Figure FDA0001389752830000021
4. the battery of claim 1, wherein the fluorobisoxalato phosphate is selected from at least one of the compounds represented by the following structural formula;
Figure FDA0001389752830000022
5. the battery according to claim 1, wherein the content of the cyclic phosphazene compound in the electrolyte is 0.001 to 3% by mass, preferably 0.1 to 2% by mass.
6. The battery according to claim 1, wherein the fluorobisoxalato phosphate is present in the electrolyte in an amount of 0.01 to 3% by weight, preferably 0.1 to 2% by weight.
7. The cell according to claim 1, wherein the electrolyte is selected from at least one of lithium hexafluorophosphate, lithium bis (trifluoromethyl) sulfonimide, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium hexafluoroarsenate, lithium bis (oxalato) borate, lithium perchlorate, preferably lithium hexafluorophosphate.
8. The battery according to claim 1, wherein the additive further comprises at least one of a dinitrile compound, a cyclic carbonate compound containing an unsaturated bond, a cyclic sulfate compound, a sultone compound, and lithium difluorophosphate;
preferably, the dinitrile compound is selected from at least one compound shown in a formula III-1, the cyclic carbonate compound containing unsaturated bonds is selected from at least one compound shown in a formula III-2, the cyclic sulfate compound is selected from at least one compound shown in a formula III-3, and the sultone compound is selected from at least one compound shown in a formula III-4;
Figure FDA0001389752830000031
wherein R is31Selected from substituted or unsubstituted C1～C12An alkylene group or a substituted alkylene group,
R32selected from alkenyl-substituted C1～C6Alkylene, substituted or unsubstituted C2～C6An alkenylene group, a carboxyl group,
R33、R34each independently selected from substituted or unsubstituted C1～C6Alkylene, substituted or unsubstituted C2～C6An alkenylene group, a carboxyl group,
the substituent is selected from halogen and C1～C3Alkyl radical, C2～C4An alkenyl group.
9. The cell according to claim 8, wherein the dinitrile compound is selected from at least one of glutaronitrile and adiponitrile, the cyclic carbonate compound containing an unsaturated bond is selected from ethylene carbonate, the cyclic sulfate compound is selected from vinyl sulfate, and the sultone compound is selected from 1, 3-propylene sultone.
10. The battery of claim 1, wherein the battery has a charge cutoff voltage of not less than 4.2V.
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CN112349960B (en) * 2019-08-08 2021-12-07 宁德时代新能源科技股份有限公司 Electrolyte and lithium ion battery
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