CN112271331A - High-voltage electrolyte of lithium ion battery and application thereof - Google Patents
High-voltage electrolyte of lithium ion battery and application thereof Download PDFInfo
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- CN112271331A CN112271331A CN202011148775.5A CN202011148775A CN112271331A CN 112271331 A CN112271331 A CN 112271331A CN 202011148775 A CN202011148775 A CN 202011148775A CN 112271331 A CN112271331 A CN 112271331A
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 114
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 52
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 239000013538 functional additive Substances 0.000 claims abstract description 17
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 11
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 11
- 239000011356 non-aqueous organic solvent Substances 0.000 claims abstract description 9
- IDUSTNHRSGBKQU-UHFFFAOYSA-N diethyl phenyl phosphite Chemical group CCOP(OCC)OC1=CC=CC=C1 IDUSTNHRSGBKQU-UHFFFAOYSA-N 0.000 claims description 59
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 13
- -1 fumaric dinitrile Chemical compound 0.000 claims description 10
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 7
- 239000004743 Polypropylene Substances 0.000 claims description 6
- 229920001155 polypropylene Polymers 0.000 claims description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 4
- 239000004698 Polyethylene Substances 0.000 claims description 4
- 229910052744 lithium Inorganic materials 0.000 claims description 4
- 229920000573 polyethylene Polymers 0.000 claims description 4
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 4
- XLGKKDZDZBIMRD-UHFFFAOYSA-N dimethyl phenyl phosphite Chemical compound COP(OC)OC1=CC=CC=C1 XLGKKDZDZBIMRD-UHFFFAOYSA-N 0.000 claims description 3
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 claims description 2
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 2
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 claims description 2
- 239000004677 Nylon Substances 0.000 claims description 2
- BTGRAWJCKBQKAO-UHFFFAOYSA-N adiponitrile Chemical compound N#CCCCCC#N BTGRAWJCKBQKAO-UHFFFAOYSA-N 0.000 claims description 2
- 239000010425 asbestos Substances 0.000 claims description 2
- 239000002131 composite material Substances 0.000 claims description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 2
- 239000004744 fabric Substances 0.000 claims description 2
- 239000003365 glass fiber Substances 0.000 claims description 2
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 claims description 2
- MCVFFRWZNYZUIJ-UHFFFAOYSA-M lithium;trifluoromethanesulfonate Chemical compound [Li+].[O-]S(=O)(=O)C(F)(F)F MCVFFRWZNYZUIJ-UHFFFAOYSA-M 0.000 claims description 2
- 229920001778 nylon Polymers 0.000 claims description 2
- 229910052895 riebeckite Inorganic materials 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 abstract description 5
- 238000007254 oxidation reaction Methods 0.000 abstract description 5
- 239000013078 crystal Substances 0.000 abstract description 4
- 238000000034 method Methods 0.000 abstract description 4
- 239000007774 positive electrode material Substances 0.000 abstract description 4
- 239000007772 electrode material Substances 0.000 abstract description 3
- 230000008569 process Effects 0.000 abstract description 3
- 238000006479 redox reaction Methods 0.000 abstract description 3
- 230000002441 reversible effect Effects 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 25
- 229910032387 LiCoO2 Inorganic materials 0.000 description 20
- 229910012820 LiCoO Inorganic materials 0.000 description 16
- 210000004027 cell Anatomy 0.000 description 15
- 239000000654 additive Substances 0.000 description 12
- 230000001351 cycling effect Effects 0.000 description 12
- 230000000996 additive effect Effects 0.000 description 9
- 238000000354 decomposition reaction Methods 0.000 description 7
- 239000002904 solvent Substances 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 229910001290 LiPF6 Inorganic materials 0.000 description 5
- 239000011259 mixed solution Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- 210000001787 dendrite Anatomy 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 238000003917 TEM image Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- RIOQSEWOXXDEQQ-UHFFFAOYSA-N triphenylphosphine Chemical group C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1 RIOQSEWOXXDEQQ-UHFFFAOYSA-N 0.000 description 2
- PZASAAIJIFDWSB-CKPDSHCKSA-N 8-[(1S)-1-[8-(trifluoromethyl)-7-[4-(trifluoromethyl)cyclohexyl]oxynaphthalen-2-yl]ethyl]-8-azabicyclo[3.2.1]octane-3-carboxylic acid Chemical compound FC(F)(F)C=1C2=CC([C@@H](N3C4CCC3CC(C4)C(O)=O)C)=CC=C2C=CC=1OC1CCC(C(F)(F)F)CC1 PZASAAIJIFDWSB-CKPDSHCKSA-N 0.000 description 1
- WGXCZOHFLNENHN-UHFFFAOYSA-N C(C)OP(OCC)(O)C1=CC=CC=C1 Chemical compound C(C)OP(OCC)(O)C1=CC=CC=C1 WGXCZOHFLNENHN-UHFFFAOYSA-N 0.000 description 1
- 125000002015 acyclic group Chemical group 0.000 description 1
- 239000008280 blood Substances 0.000 description 1
- 210000004369 blood Anatomy 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006864 oxidative decomposition reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- BDZBKCUKTQZUTL-UHFFFAOYSA-N triethyl phosphite Chemical compound CCOP(OCC)OCC BDZBKCUKTQZUTL-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
-
- 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
-
- 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
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention provides a high-voltage electrolyte of a lithium ion battery and application thereof. The electrolyte comprises a nonaqueous organic solvent, lithium salt and a functional additive, wherein the mass fraction of the functional additive in the electrolyte is less than 5%, the mass fraction of the nonaqueous organic solvent in the electrolyte is 60-90%, and the mass fraction of the lithium salt in the electrolyte is 10-20%. The electrolyte can form a stable CEI oxidation film on the surface of the anode, so that the electrolyte is prevented from continuously generating oxidation-reduction reaction on the surface of the anode; meanwhile, the oxide film can effectively avoid the continuous contact of electrolyte and a positive electrode material, thereby protecting the crystal structure of the electrode material, effectively reducing the loss of reversible capacity in the circulation process and improving the stability and the safety of the battery.
Description
Technical Field
The invention relates to an electrolyte, in particular to a high-voltage-resistant lithium ion battery electrolyte, and belongs to the technical field of lithium ion batteries.
Background
The lithium ion battery has the advantages of high energy density, high working voltage, long cycle life, high power, environmental friendliness and the like, and becomes a hotspot of research in the field of new energy, and the application of the lithium ion battery is also expanded from 3C electronic products, portable electronic equipment, electric tools and electric automobiles to the fields of scale energy storage, war industry, aerospace and the like. With the rapid development of lithium ion batteries and the demand of electric vehicles for high-capacity lithium ion batteries, development of high-safety, high-capacity, high-power, long-life and environment-friendly lithium ion batteries is urgently needed.
The electrolyte serves as an important component of the battery, plays a role in transporting lithium ions between the positive electrode and the negative electrode of the lithium ion battery, and is called as 'blood' of the lithium ion battery. It has important effect on the specific capacity, working temperature range, circulation efficiency, safety performance and the like of the battery. The selection of a proper electrolyte is the key to obtain a lithium ion secondary battery with high energy density, long cycle life and good safety performance, so that the research of the electrolyte meeting the requirements of the lithium ion battery is very important.
At present, the lithium ion battery has the defects of rapid capacity loss and poor cycle performance under high temperature and high pressure, and can not meet the working requirement that the lithium ion battery is often under the high temperature and high pressure. In order to meet the above requirements, an electrolyte capable of operating a lithium ion battery under a high voltage condition needs to be developed. The development of high-voltage electrolyte is more inclined to optimize the composition of a solvent and add proper additives, so that the high-voltage, oxidation-resistant and high-temperature-resistant performances of the electrolyte are improved, and the cycle performance of the lithium ion battery under high voltage is improved.
Disclosure of Invention
In order to solve the above technical problems, an object of the present invention is to provide an electrolyte for a lithium ion battery, which can improve the problem of easy oxidative decomposition of the electrolyte for a lithium ion battery under high pressure.
Another object of the present invention is to provide a lithium ion battery having the above electrolyte solution.
In order to achieve any one of the above objects, the present invention firstly provides a lithium ion battery high voltage electrolyte, which includes a nonaqueous organic solvent, a lithium salt and a functional additive, wherein the mass fraction of the functional additive in the electrolyte is less than 5%, the mass fraction of the nonaqueous organic solvent in the electrolyte is 60% to 90%, and the mass fraction of the lithium salt in the electrolyte is 10% to 20%, based on 100% of the total mass of the lithium ion battery high voltage electrolyte.
According to the high-voltage electrolyte of the lithium ion battery, the specific functional additive is added, so that the high-voltage electrolyte has a wider electrochemical window and dielectric constant and a higher oxidation potential, a formed CEI film is more stable, and a positive electrode is separated from the electrolyte.
In one embodiment of the invention, the mass fraction of the functional additive in the electrolyte is 0.1% to 5%. For example, the functional electrolyte may be added in an amount of 0.2%, 0.3%, 0.4%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, or 4%.
In one embodiment of the invention, the functional additive comprises one or more of phenyl dimethyl phosphite, fumaric dinitrile, adiponitrile and propylene carbonate; preferably, the functional additive used is diethyl phenylphosphite having the following structural formula:
the invention provides a lithium ion battery high-voltage electrolyte, which comprises a non-aqueous organic solvent, lithium salt and a functional additive, wherein the functional additive is preferably phenyl diethyl phosphite. The phenyl diethyl phosphite is added into the electrolyte, so that a stable CEI film can be formed on the surface of the anode, and the electrolyte is prevented from continuously generating oxidation-reduction reaction on the surface of the anode; meanwhile, the oxide film effectively avoids continuous contact between electrolyte and a positive electrode material, thereby protecting the crystal structure of the electrode material, effectively reducing the loss of reversible capacity in the circulation process and improving the stability and the safety of the battery.
In one embodiment of the present invention, the non-aqueous organic solvent is a combination of at least two of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, dimethoxyethane, and diethyl carbonate.
In one embodiment of the invention, the concentration of lithium salt is 0.8mol/L to 1.5 mol/L; preferably, the lithium salt is one or a combination of two or more of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluorophosphate and lithium trifluoromethanesulfonate.
The invention also provides a lithium ion battery, which comprises a positive electrode, a diaphragm, electrolyte and a negative electrode, wherein the electrolyte is the high-voltage electrolyte of the lithium ion battery.
In one embodiment of the present invention, the positive electrode includes a positive current collector foil and a positive active material attached to the positive current collector foil.
In one embodiment of the present invention, the separator is one of a polypropylene film, a polyethylene film, a polypropylene/polyethylene/polypropylene composite film, nylon cloth, glass fiber, and asbestos paper.
The invention also provides a product which contains the lithium ion battery.
According to the high-voltage electrolyte of the lithium ion battery, a specific functional additive, especially the phenyl diethyl phosphite, is adopted, and the functional additive, especially the phenyl diethyl phosphite, has a lower oxidation-reduction potential, so that a stable CEI film can be formed on the surface of the anode, and the electrolyte is prevented from continuously generating oxidation-reduction reaction on the surface of the anode; meanwhile, the oxide film can effectively avoid the continuous contact of electrolyte and a positive electrode material, thereby protecting the crystal structure of the electrode material, effectively reducing the loss of reversible capacity in the circulation process and improving the stability and the safety of the battery.
Drawings
FIG. 1 shows LiCoO obtained in example 1 and comparative example 12a/Li battery cycle performance diagram.
FIG. 2 shows LiCoO obtained in example 1 and comparative example 12Rate performance graph of/Li battery.
FIG. 3 shows LiCoO obtained in example 1 and comparative example 12CV diagram of Li battery.
FIG. 4 shows the preparation of example 1 and comparative example 1The obtained LiCoO2EIS diagram of/Li cell.
FIG. 5 shows LiCoO obtained in example 1 and comparative example 12LiCoO in Li cells2SEM image of pole piece.
FIG. 6 shows LiCoO obtained in example 1 and comparative example 12SEM image of Li plate in Li battery.
FIG. 7 shows LiCoO in the middle of the products of example 1 and comparative example 12LiCoO in Li cells2TEM image of the pole piece.
Detailed Description
Example 1
This example provides a lithium ion half cell, which was prepared by the following procedure.
1.0mol of LiPF6Dissolving in a solvent with the volume ratio of 1: 1, a blank electrolyte is formed in a mixed solution (volume is 0.5L) of Ethylene Carbonate (EC)/dimethyl carbonate (DMC), and then 0.1 wt% of diethyl phenylphosphite (DEPP) is added into the blank electrolyte to serve as an additive, namely the diethyl phenylphosphite accounts for 0.1% of the total weight of the electrolyte. Assembled into LiCoO2a/Li half cell.
Comparative example 1
For comparison, a blank electrolyte was also assembled into LiCoO2Li half cell, forming comparative example 1.
FIG. 1 is LiCoO2The cycle diagrams of the Li battery in the base electrolyte (comparative example 1) and the electrolyte containing DEPP (example 1) are shown in figure 1, and the cycle performance diagram obtained by cycling the battery for 100 weeks at a constant current density of 185mAh/g at 1C in the range of 3.0-4.5V is shown in figure 1, the initial capacities of the base electrolyte and 0.1 wt% diethyl phenylphosphite are respectively 174.5mAh/g and 172.4mAh/g, the initial capacities after 100 weeks of cycling are respectively 61.3mAh/g and 116mAh/g, and the capacity retention rates are respectively 35% and 67%, which shows that the diethyl phenylphosphite can effectively improve LiCoO2Specific discharge capacity and cycle retention rate of (a).
FIG. 2 is LiCoO2The rate diagrams of the Li cell in the base electrolyte (comparative example 1) and the DEPP-containing electrolyte (example 1) show from FIG. 2 that at low rates the capacities are approximately similar, but with rateThe difference between the two is obviously observed, the effect is similar to that of the circulating capacity, and the effect of the phenyl diethyl phosphite on the LiCoO is reflected2The effect of the half cell. It is noted that the battery containing 0.1% diethyl phenylphosphite still maintained 179mAh g when the current was changed to low after 5 weeks of cycling at 5C high rate-1The specific discharge capacity indicates that the battery containing the additive can resist high current without causing great damage.
FIG. 3 is LiCoO2CV graphs of a/Li battery in a base electrolyte (comparative example 1) and a DEPP-containing electrolyte (example 1), wherein a graph a of fig. 3 is a CV comparison graph of a first turn, and a graph b of fig. 3 corresponds to a CV comparison graph of a second turn. As can be seen from FIG. 3, the oxidation potential of the battery containing 0.1% of phenyl diethyl phosphite electrolyte was advanced compared to that of the base electrolyte, indicating that phenyl diethyl phosphite is superior to EC decomposition, and the formed CEI film can inhibit the decomposition of the base electrolyte and Co3+Decomposition of (3). Meanwhile, the reduction peak position of the electrolyte containing phenyl diethyl phosphite is higher than that of the basic electrolyte, which shows that the phenyl diethyl phosphite can be preferentially reduced at the anode to form an interface film. The higher the peak height of the phenyl diethyl phosphite-containing electrolyte compared to the base electrolyte, indicates the faster the mobility of lithium ions of the lithium ions in the phenyl diethyl phosphite electrolyte. Further, the potential difference between the oxidation reduction peaks indicates the degree of polarization, and it is apparent that the degree of polarization of the battery is weaker in the electrolyte containing DEPP than in the base electrolyte.
FIG. 4 is LiCoO2Impedance plots of the/Li cell after cycling in the base electrolyte (comparative example 1) and the DEPP-containing electrolyte (example 1), it is evident from fig. 4 that an ac impedance profile is observed. It is well known that the formation of the CEI layer is mainly caused by the oxidation and decomposition of the electrolyte, the size of the semicircle is mainly related to the (charge transfer rate) resistance of the CEI film, and the slope is mainly related to the transfer of lithium ions. As can be seen from the EIS chart, 0.1 wt% R of diethyl phenylphosphiteCEIAnd RLi+Are all smaller than that of the basic electrolyte, which shows that the CEI film generated by the decomposition of the phenyl diethyl phosphite is more favorable for the intercalation and deintercalation of lithium ions.
FIG. 5 is LiCoO2SEM pictures of a/Li battery after cycling in a base electrolyte (comparative example 1) and a DEPP-containing electrolyte (example 1), panel a in FIG. 5 being LiCoO before not cycling2Pole piece, panel b in FIG. 5 and panel c in FIG. 5 are LiCoO containing no and diethyl phenylphosphite after 100 cycles2The pole piece can be seen from the figure, the pole piece surface of the basic electrolyte has a thick surface layer. This is due to repeated deposition of reduction reaction of the electrolyte due to rearrangement of the SEI film. Recycled LiCoO in an electrolyte containing 0.1 wt% of a diethyl phenylphosphite additive2The shape of the sheet is very similar to that before the circulation, and the surface film is compact and continuous, which shows that the phenyl diethyl phosphite additive greatly reduces the subsequent side reaction of the electrode/electrolyte interface. This provides evidence for high quality and good stability of the CEI membrane in the presence of the phenyl diethyl phosphite additive.
Fig. 6 is an SEM image of the Li electrode before non-cycling and after cycling in the base electrolyte and the DEPP-containing electrolyte, and fig. 6 is an SEM image of the lithium sheet, the Li sheet before non-cycling (panel a in fig. 6), after cycling of the base electrolyte (panel b in fig. 6) and after cycling of the phenyl diethyl phosphite-containing electrolyte (panel c in fig. 6); it can be seen from the figure that under the action of the base electrolyte, a large number of lithium dendrites appear on the surface of the Li sheet, compared to less dendrites under the action of the electrolyte with additives. The phenyl diethyl phosphite can effectively inhibit the formation of dendrites on the surface of the Li electrode.
FIG. 7 is LiCoO2TEM images before and after cycling in the base electrolyte and the DEPP-containing electrolyte, panel a in FIG. 7 being an acyclic LiCoO2Image of the pole piece, panel b in FIG. 7, LiCoO circulating in the base electrolyte2Image of the pole piece, panel c in FIG. 7 is LiCoO circulating in a phenyl diethyl phosphite-containing electrolyte2Images of the pole pieces, after 100 cycles in the basic electrolyte, LiCoO2A film of non-uniform thickness appeared on the surface of the particles as a result of electrolyte decomposition, indicating LiCoO after repeated cycling below 4.5V2Crystal ofThe bulk structure is destroyed in the base electrolyte. This is responsible for LiCoO2An important reason for the rapid decay of the electrode capacity. However, after 100 cycles in an electrolyte containing 0.1 wt% of phenyl diethyl phosphite, LiCoO2The electrode surface is covered by a thin and uniform film. The particles were barely visible, indicating that the phenyl diethyl phosphite additive was effective in inhibiting LiCoO2Decomposition of surface electrolyte solvent to inhibit LiCoO under high pressure2Structural damage to the particles. These all contribute to the enhancement of LiCoO2Cycling stability of the cell.
Example 2
1.0mol of LiPF6Dissolving in a solvent with the volume ratio of 1: 1, 0.5L of mixed solution of Ethylene Carbonate (EC)/dimethyl carbonate (DMC) is formed into blank electrolyte, and then 0.5 wt% of phenyl diethyl phosphite is added into the blank electrolyte as an additive, namely 0.5% of phenyl diethyl phosphite in the total weight of the electrolyte. Assembled into LiCoO2a/Li half cell.
Example 3
1.0mol of LiPF6Dissolving in a solvent with the volume ratio of 1: 1, forming a blank electrolyte in a mixed solution of Ethylene Carbonate (EC)/dimethyl carbonate (DMC) (the volume is 0.5L), and adding 1 wt% of phenyl diethyl phosphite serving as an additive into the blank electrolyte, wherein the phenyl diethyl phosphite accounts for 1% of the total weight of the electrolyte. Assembled into LiCoO2a/Li half cell.
Example 4
1.0mol of LiPF6Dissolving in a solvent with the volume ratio of 1: 1, forming a blank electrolyte in a mixed solution of Ethylene Carbonate (EC)/dimethyl carbonate (DMC) (the volume is 0.5L), and adding 2 wt% of phenyl diethyl phosphite serving as an additive into the blank electrolyte, wherein the phenyl diethyl phosphite accounts for 2% of the total weight of the electrolyte. A LiCoO2/Li half cell was assembled.
Example 5
1.0mol of LiPF6Dissolving in a solvent with the volume ratio of 1: 1 in a mixed solution of Ethylene Carbonate (EC)/dimethyl carbonate (DMC) (the volumes are all0.5L) to form a blank electrolyte, and then adding 3 wt% of phenyl diethyl phosphite serving as an additive into the blank electrolyte, wherein the phenyl diethyl phosphite accounts for 3% of the total weight of the electrolyte. Assembled into LiCoO2a/Li half cell.
Comparative example 2
This comparative example provides a lithium ion half cell which differs from example 1 only in that diethyl phenylphosphite is replaced by dimethyl phenylphosphite.
Comparative example 3
This comparative example provides a lithium ion half cell which differs from example 1 only in that diethyl phenylphosphite is replaced with 10 wt% triethyl phosphite.
Comparative example 4
This comparative example provides a lithium ion half cell which differs from example 1 only in that the phenyl diethyl phosphite is replaced with triphenylphosphine.
The test results of lithium ion batteries prepared by using the electrolytes of examples 1 to 5 and comparative examples 1 to 4 are shown in table 1.
TABLE 1
| Sample (I) | Specific capacity of first discharge/mAh.g-1 | Capacity retention ratio of 100 cycles/%) |
| Example 1 | 172 | 67.4 |
| Example 2 | 171.6 | 63.6 |
| Example 3 | 171.7 | 58.5 |
| Example 4 | 173.2 | 56.9 |
| Example 5 | 170 | 55.7 |
| Comparative example 1 | 174.5 | 35 |
| Comparative example 2 | 171.3 | 50.4 |
| Comparative example 3 | 174 | 50.3 |
| Comparative example 4 | 168 | 50.6 |
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. The lithium ion battery high-voltage electrolyte comprises a non-aqueous organic solvent, a lithium salt and a functional additive, wherein the mass fraction of the functional additive in the electrolyte is less than 5%, the mass fraction of the non-aqueous organic solvent in the electrolyte is 60% -90%, and the mass fraction of the lithium salt in the electrolyte is 10% -20%, based on 100% of the total mass of the lithium ion battery high-voltage electrolyte.
2. The high-voltage electrolyte for the lithium ion battery of claim 1, wherein the mass fraction of the functional additive in the electrolyte is 0.1-5%.
3. The high voltage lithium ion battery electrolyte of claim 1 or 2, wherein the functional additive comprises one or a combination of two or more of phenyl dimethyl phosphite, fumaric dinitrile, adiponitrile, and propylene carbonate.
4. The high-voltage electrolyte of the lithium ion battery as claimed in claim 3, wherein the functional additive is diethyl phenylphosphite with a structural formula shown as follows:
5. the high voltage electrolyte of lithium ion battery of claim 1, wherein the non-aqueous organic solvent is a combination of at least two of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, dimethoxyethane, diethyl carbonate.
6. The lithium ion battery high-voltage electrolyte according to claim 1, wherein the lithium salt is one or a combination of two or more of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluorophosphate and lithium trifluoromethanesulfonate.
7. A lithium-ion battery high-voltage electrolyte according to claim 1 or 6, wherein the lithium salt concentration is 0.8-1.5 mol/L.
8. A lithium ion battery, which comprises a positive electrode, a diaphragm, an electrolyte and a negative electrode, wherein the electrolyte is the high-voltage electrolyte of the lithium ion battery of any one of claims 1 to 7.
9. The lithium ion battery of claim 9, wherein the separator is one of a polypropylene film, a polyethylene film, a polypropylene/polyethylene/polypropylene composite film, nylon cloth, glass fiber, and asbestos paper.
10. A product comprising the lithium ion battery of claim 8 or 9.
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