CN116169354A - Non-aqueous electrolyte additive and application thereof - Google Patents

Non-aqueous electrolyte additive and application thereof Download PDF

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CN116169354A
CN116169354A CN202111406088.3A CN202111406088A CN116169354A CN 116169354 A CN116169354 A CN 116169354A CN 202111406088 A CN202111406088 A CN 202111406088A CN 116169354 A CN116169354 A CN 116169354A
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additive
carbon atoms
nonaqueous electrolyte
lithium
nonaqueous
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岳敏
杜建委
曾益平
大浦靖
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Shenzhen Yanyi New Materials 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
    • 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
    • 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

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Abstract

The invention provides a nonaqueous electrolyte additive and application thereof, wherein the nonaqueous electrolyte additive comprises any one or a combination of at least two of sulfonic acid phosphoric anhydride, sulfonic acid phosphite anhydride, sulfuric acid phosphoric anhydride or sulfuric acid phosphite anhydride compounds, and the nonaqueous electrolyte additive has a sulfur-containing part and a phosphorus-containing part, so that the cycle performance of a lithium ion battery can be effectively improved.

Description

Non-aqueous electrolyte additive and application thereof
Technical Field
The invention belongs to the field of lithium ion batteries, and relates to a nonaqueous electrolyte additive and application thereof.
Background
In the charging process of the lithium ion battery, the positive electrode has strong oxidizing property, the negative electrode has strong reducing property, so that the traditional electrolyte component is easily oxidized and decomposed at the positive electrode, and is easily reduced at the negative electrode, and the process leads to the consumption of the electrolyte component and the consumption of active lithium components, so that the battery cycle performance is deteriorated, the gas production is increased, and the service performance of the battery is finally influenced.
The SEI film is an electronically insulating ion conducting film formed on the surface of an electrode to isolate the electrode from an electrolyte, and is usually formed by a reduction reaction of a solvent, an additive and the like in the electrolyte under a low voltage or an oxidation reaction under a high voltage (which is often called as CEI film). The formation of the SEI film can prevent the electrolyte component from further contact with the electrode to undergo oxidative or reductive decomposition, thereby reducing the increase of impedance and the loss of active lithium, and improving the cycle performance of the battery. The excellent SEI film is usually an organic and inorganic component composite film which has better ion conduction capability for electronic insulation, and mainly contains more hetero atoms, such as additives containing components of phosphorus, nitrogen, sulfur and the like.
Based on the invention, the invention designs and develops a novel electrolyte additive with (phosphorous) phosphate groups and sulfonic (sulfuric) acid groups, can form SEI films with P and S components on the surfaces of electrodes, and has good advantages for improving the cycle performance of lithium ion batteries. Other properties of lithium ion batteries can also be improved by replacing the group attached to the P, S atom.
Disclosure of Invention
The invention aims to provide a nonaqueous electrolyte additive and application thereof, wherein the nonaqueous electrolyte additive comprises any one or a combination of at least two of sulfonic acid phosphoric anhydride, sulfonic acid phosphorous anhydride, sulfuric acid phosphoric anhydride or sulfuric acid phosphorous anhydride compounds, and the nonaqueous electrolyte additive is a novel electrolyte additive with a sulfur-containing part (sulfuric acid group or sulfonic acid group) and a phosphorus-containing part (phosphoric acid group or phosphorous acid group) and can effectively improve the cycle performance of a lithium ion battery. Other properties of lithium ion batteries can also be improved by replacing the group attached to P, S atoms; for example, by introducing unsaturated groups, the high-temperature storage performance of the battery is improved; the low-temperature discharge performance of the battery is improved, for example, by introducing fluorine groups.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the invention provides a nonaqueous electrolyte additive, which comprises a first additive and/or a second additive, wherein the structural formula of the first additive is shown as formula I, and the structural formula of the second additive is shown as formula II:
Figure BDA0003372861880000021
wherein R in formulas I and II independently comprises any one or a combination of at least two of halogen atom, saturated alkyl group with 1-6 carbon atoms, saturated alkoxy group with 1-6 carbon atoms, unsaturated alkyl group with 1-6 carbon atoms, unsaturated alkoxy group with 1-6 carbon atoms, fluoroalkyl group with 1-6 carbon atoms, fluoroalkoxy group with 1-6 carbon atoms, cyano-substituted alkyl group with 1-6 carbon atoms, cyano-substituted alkoxy group with 1-6 carbon atoms, alkyl group substituted with 1-6 isocyanate groups or alkoxy group substituted with 1-6 isocyanate groups, rf 1 、Rf 2 Independently comprises any one or a combination of at least two of fluorine atom, fluorinated alkyl group with 1-6 carbon atoms, fluorinated alkoxy group with 1-6 carbon atoms, cyano group substituted alkyl group with 1-6 carbon atoms or cyano group substituted alkoxy group with 1-6 carbon atoms.
The nonaqueous electrolyte additive provided by the invention has a novel electrolyte additive containing a sulfur-containing part (sulfuric acid group or sulfonic acid group) and a phosphorus-containing part (phosphoric acid group or phosphorous acid group), and can effectively improve the cycle performance of a lithium ion battery. Other properties of lithium ion batteries can also be improved by replacing the group attached to P, S atoms; for example, by introducing unsaturated groups, the high-temperature storage performance of the battery is improved; the low-temperature discharge performance of the battery is improved, for example, by introducing fluorine groups.
In the structure of the additive, a group Rf with strong electron withdrawing function is introduced on the phosphorus atom 1 、Rf 2 The method has the advantages that the lone pair electrons on P or O are stabilized through electron-withdrawing effect, so that the lone pair electrons can be complexed with metal ions in the charge and discharge process, the degradation of the battery cycle performance caused by the dissolution of the metal ions is reduced, and the method is particularly suitable for being used in a high-nickel ternary system.
Preferably, the first additive comprises
Figure BDA0003372861880000031
Figure BDA0003372861880000032
Figure BDA0003372861880000033
Any one or a combination of at least two of these.
Preferably, the second additive comprises
Figure BDA0003372861880000034
Figure BDA0003372861880000035
/>
Figure BDA0003372861880000036
Any one or a combination of at least two of these.
In a second aspect, the present invention provides a nonaqueous electrolyte comprising the nonaqueous electrolyte additive of the first aspect, the electrolyte further comprising a lithium salt and a nonaqueous solvent.
Preferably, the mass fraction of the additive is 0.2 to 5%, preferably 0.5 to 2%, based on 100% of the mass of the nonaqueous electrolytic solution.
Preferably, the lithium salt comprises LiPF 6 、LiBF 4 、LiClO 4 、LiAsF 6 、LiN(SO 2 CF 3 ) 2 Or LiN (SO) 2 F) 2 Any one or a combination of at least two of these.
Preferably, the molar concentration of the lithium salt is 0.5 to 2mol/L, preferably 1 to 1.5mol/L.
Preferably, the nonaqueous solvent includes any one or a combination of at least two of cyclic carbonates, chain carbonates, cyclic carboxylic acid esters, chain carboxylic acid esters, fluorocarbonates, carboxylic acid esters, fluoroethers, or sulfones.
Preferably, the nonaqueous solvent includes any one or a combination of at least two of Ethylene Carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), propylene Carbonate (PC), ethyl Acetate (EA), ethyl Propionate (EP), propyl Propionate (PP), γ -butyrolactone (GBL), methyl Acetate (MA), methyl Butyrate (MB), ethyl Butyrate (EB), or Propyl Butyrate (PB).
Preferably, the mass fraction of the nonaqueous solvent is 50 to 85% based on 100% of the mass of the nonaqueous electrolytic solution.
Preferably, the electrolyte further comprises a third additive.
Preferably, the third additive comprises fluoroethylene carbonate (FEC), vinylene Carbonate (VC), 1, 3-Propane Sultone (PS), lithium difluorooxalato borate (LiDFOB), lithium bisoxalato borate (LiBOB), lithium tetrafluoroborate (LiBF) 4 ) Lithium difluorobis (oxalato) phosphate (LiDFBOP), ethylene carbonate (VEC), 1, 3-Propenesulfonolide (PES), lithium difluorosulfonimide (LiLSI), methylene Methyldisulfonate (MMDS) or lithium difluorophosphate (LiPO) 2 F 2 ) Any one or a combination of at least two of these.
Preferably, the third additive is 0.05 to 20% by mass based on 100% by mass of the nonaqueous electrolytic solution.
In a third aspect, the present invention provides a lithium ion battery comprising the nonaqueous electrolyte as described in the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) The non-aqueous electrolyte additive provided by the invention has a novel electrolyte additive containing a sulfur-containing part (sulfuric acid group or sulfonic acid group) and a phosphorus-containing part (phosphoric acid group or phosphorous acid group), and can effectively improve the cycle performance of a lithium ion battery. Other properties of lithium ion batteries can also be improved by replacing the group attached to P, S atoms; for example, by introducing unsaturated groups, the high-temperature storage performance of the battery is improved; the low-temperature discharge performance of the battery is improved, for example, by introducing fluorine groups.
(2) In the structure of the non-aqueous electrolyte additive, the group with strong electron-withdrawing function is introduced to the phosphorus atom, and the function is to stabilize the lone pair electron on P or O by the electron-withdrawing function, so that the non-aqueous electrolyte additive can complex with metal ions in the charge and discharge process, reduce the deterioration of the battery cycle performance caused by the dissolution of the metal ions, and is particularly suitable for being used in a high-nickel ternary system.
Drawings
FIG. 1 is a nuclear magnetic spectrum of difluorophosphite ethyl sulfate anhydride of example 1.
FIG. 2 is a nuclear magnetic spectrum of propenyl sulfonic acid difluorophosphoric anhydride of example 15.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
The terms "comprising," "including," "having," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.
The conjunction "consisting of …" excludes any unspecified element, step or component. If used in a claim, such phrase will cause the claim to be closed, such that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of …" appears in a clause of the claim body, rather than immediately following the subject, it is limited to only the elements described in that clause; other elements are not excluded from the stated claims as a whole.
When an equivalent, concentration, or other value or parameter is expressed as a range, preferred range, or a range bounded by a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when ranges of "1 to 5" are disclosed, the described ranges should be construed to include ranges of "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a numerical range is described herein, unless otherwise indicated, the range is intended to include its endpoints and all integers and fractions within the range.
The singular forms include plural referents unless the context clearly dictates otherwise. "optional" or "any" means that the subsequently described event or event may or may not occur, and that the description includes both cases where the event occurs and cases where the event does not.
The indefinite articles "a" and "an" preceding an element or component of the invention are not limited to the requirement (i.e. the number of occurrences) of the element or component. Thus, the use of "a" or "an" should be interpreted as including one or at least one, and the singular reference of an element or component includes the plural reference unless the amount clearly dictates otherwise.
The description of the terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., herein describe means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily for the same embodiment or example.
The invention discloses a plurality of synthesis methods shown in a formula I and a formula II, and particularly the synthesis methods are also changed to a certain extent according to the different structures of substances. Wherein the sulfur-containing part and the phosphorus-containing part are mainly separated, and can be combined by respectively preparing acid or acyl chloride of the two parts and finally utilizing the reaction of the two parts.
For example, difluorophosphite ethyl sulfate anhydride
Figure BDA0003372861880000071
Specific methods include preparation of ethylsulfuric acid, preparation of ethylsulfuric acid dichlorophosphite anhydride and fluorination of ethylsulfuric acid dichlorophosphite anhydride. Firstly, adding 2mol of ethanol into a three-neck flask under the protection of nitrogen, starting stirring, controlling the temperature below 20 ℃, and gradually dropwise adding 122gChlorosulfonic acid was added dropwise for 1h. After the dripping is finished, the reaction is continued for 12 hours until no acidic tail gas is generated. At this time, the reaction was stopped, and excess ethanol was distilled off by rotary evaporation to obtain ethylsulfuric acid. 0.5mol of ethyl sulfuric acid is taken and dispersed in 200ml of dichloromethane, and then 1mol of phosphorus trichloride prepared in advance is gradually added dropwise under the ice water bath condition, and the reaction time is 24 hours. After the reaction is completed, rotary steaming is carried out to remove most of unreacted phosphorus trichloride, and then 4 times equivalent of fluoridation reagent KHF of ethyl sulfuric acid is added 2 The fluorination was carried out at a temperature of 80 ℃. After the fluorination reaction for 24 hours, the temperature is reduced to stop the reaction. Filtering to remove salt, and distilling to obtain the product
Figure BDA0003372861880000072
The nuclear magnetic resonance is shown in FIG. 1 by nuclear magnetic resonance detection analysis.
Example 1
The embodiment provides a nonaqueous electrolyte, and the preparation method of the nonaqueous electrolyte comprises the following steps:
in a glove box filled with argon, a mixed solvent is prepared according to the volume ratio of EC/EMC/DEC=3:5:2, and then a certain amount of lithium hexafluorophosphate is slowly added into the solvent to prepare a nonaqueous electrolyte containing 1.1mol/L lithium hexafluorophosphate. Adding a third additive of vinylene carbonate VC, 1, 3-propane sultone PS and lithium bis (fluorosulfonyl) imide LiFSI with stirring, wherein the mass percentages of the third additive of vinylene carbonate VC, 1.5% and lithium bis (fluorosulfonyl) imide LiFSI are respectively 1%, 1.5% and 1% based on 100% of the mass of the finally prepared nonaqueous electrolyte; then adding 1% of ethyl sulfuric acid difluoro-phosphite anhydride serving as a first additive into the nonaqueous electrolyte
Figure BDA0003372861880000081
Stirring for dissolution to obtain a non-aqueous electrolyte, wherein the nuclear magnetic spectrum of ethyl sulfuric acid difluoro phosphite anhydride is shown in figure 1.
Example 2
This example differs from example 1 only in that the first additive is
Figure BDA0003372861880000082
Other conditions and parameters and implementationsExample 1 is identical.
Example 3
This example differs from example 1 only in that the first additive is
Figure BDA0003372861880000083
Other conditions and parameters were exactly the same as in example 1.
Example 4
This example differs from example 1 only in that the first additive is
Figure BDA0003372861880000084
Other conditions and parameters were exactly the same as in example 1. />
Example 5
This example differs from example 1 only in that the first additive is
Figure BDA0003372861880000085
Other conditions and parameters were exactly the same as in example 1.
Example 6
This example differs from example 1 only in that the first additive is
Figure BDA0003372861880000091
Other conditions and parameters were exactly the same as in example 1.
Example 7
This example differs from example 1 only in that the first additive is
Figure BDA0003372861880000092
Other conditions and parameters were exactly the same as in example 1.
Example 8
This example differs from example 1 only in that the first additive is
Figure BDA0003372861880000093
Other conditions and parameters were exactly the same as in example 1.
Example 9
This example differs from example 1 only in that the first additive is
Figure BDA0003372861880000094
Other conditions and parameters were exactly the same as in example 1.
Example 10
The embodiment provides a nonaqueous electrolyte, and the preparation method of the nonaqueous electrolyte comprises the following steps:
in a glove box filled with argon, a mixed solvent is prepared according to the volume ratio of EC/EMC/DEC=3:5:2, and then a certain amount of lithium hexafluorophosphate is slowly added into the solvent to prepare a nonaqueous electrolyte containing 1.1mol/L lithium hexafluorophosphate. Adding a third additive of vinylene carbonate VC, 1, 3-propane sultone PS and lithium bis (fluorosulfonyl) imide LiFSI with stirring, wherein the mass percentages of the third additive of vinylene carbonate VC, 1.5% and lithium bis (fluorosulfonyl) imide LiFSI are respectively 1%, 1.5% and 1% based on 100% of the mass of the finally prepared nonaqueous electrolyte; then adding a second additive ethyl sulfuric acid difluorophosphoric anhydride with the mass percent of 1% into the nonaqueous electrolyte
Figure BDA0003372861880000101
Stirring and dissolving to obtain the non-aqueous electrolyte.
Example 11
This example differs from example 10 only in that the second additive is
Figure BDA0003372861880000102
Other conditions and parameters were exactly the same as in example 10.
Example 12
This example differs from example 10 only in that the second additive is
Figure BDA0003372861880000103
Other conditions and parameters were exactly the same as in example 10.
Example 13
This example differs from example 10 only in that the second additive is
Figure BDA0003372861880000104
Other conditions and parameters were exactly the same as in example 10.
Example 14
This example differs from example 10 only in that the second additive is
Figure BDA0003372861880000105
Other conditions and parameters were exactly the same as in example 10.
Example 15
This example differs from example 10 only in that the second additive is difluorophosphoric anhydride propenyl sulfonate
Figure BDA0003372861880000111
Other conditions and parameters were exactly the same as in example 10. The nuclear magnetic spectrum of the propenyl sulfonic acid difluorophosphoric anhydride is shown in figure 2.
Example 16
This example differs from example 10 only in that the second additive is
Figure BDA0003372861880000112
Other conditions and parameters were exactly the same as in example 10.
Example 17
This example differs from example 1 only in that the mass fraction of the first additive is 0.4% and the other conditions and parameters are exactly the same as in example 1.
Example 18
This example differs from example 1 only in that the mass fraction of the first additive is 3% and the other conditions and parameters are exactly the same as in example 1.
Example 19
The embodiment provides a nonaqueous electrolyte, and the preparation method of the nonaqueous electrolyte comprises the following steps:
in a glove box filled with argon, a mixed solvent is prepared according to the volume ratio of EC/EMC/DEC=3:5:2, and then a certain amount of lithium hexafluorophosphate is slowly added into the solvent to prepare a nonaqueous electrolyte containing 1.1mol/L lithium hexafluorophosphate. To finally produce the nonaqueous electrolyteAdding a third additive of vinylene carbonate VC, 1, 3-propane sultone PS and lithium bis (fluorosulfonyl) imide LiFSI with the mass percentage of 100% being 1%, 1.5% and 1% respectively under stirring; then adding 0.5% of ethyl sulfuric acid difluoro-phosphite anhydride serving as a first additive into the nonaqueous electrolyte
Figure BDA0003372861880000113
And 0.5% by mass of a second additive propenyl sulfonic acid difluorophosphoric anhydride
Figure BDA0003372861880000121
Stirring and dissolving to obtain the non-aqueous electrolyte.
Comparative example 1
This comparative example differs from example 1 only in that the first additive ethyl sulfate difluorophosphite is not added, and other conditions and parameters are exactly the same as in example 1.
Comparative example 2
This comparative example differs from example 1 only in that the first additive ethyl sulfuric acid difluorophosphite anhydride was replaced with lithium difluorophosphate, and the other conditions and parameters were exactly the same as in example 1.
Comparative example 3
This comparative example differs from example 1 only in that the first additive ethyl sulfuric acid difluorophosphite is replaced by vinyl sulfate, the other conditions and parameters being exactly the same as in example 1.
Performance test:
the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622), conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) according to the mass ratio of 95:3:2, fully stirring and uniformly mixing in an NMP solvent system, coating on an aluminum foil, drying and cold pressing to obtain a positive electrode plate; graphite as a negative electrode active material, acetylene black as a conductive agent, styrene-butadiene rubber as a binder and carboxymethyl cellulose (CMC) as a thickener according to the mass ratio of 96:2:1:1, fully stirring and mixing in a deionized water solvent system, coating the mixture on a copper foil, drying and cold pressing the copper foil to obtain a negative plate; sequentially laminating the positive plate, the isolating film and the negative plate, and then arranging the positive plate, the isolating film and the negative plate along the same directionThe bare cell is obtained by winding, the bare cell is placed in an outer package, the electrolyte obtained in the examples 1-19 and the comparative examples 1-3 is injected, and the prepared lithium ion battery is subjected to the procedures of packaging, standing at 45 ℃, high-temperature clamp formation, secondary packaging, capacity division and the like to obtain an NCM622/AG-4.3V lithium ion battery containing the electrolyte, and the battery performance test shown in the following is carried out on the prepared lithium ion battery:
a. normal temperature cycle performance
Under the condition of normal temperature (25 ℃), the lithium ion battery is charged to 4.3V under the condition of constant current and constant voltage of 1C, and then discharged to 3.0V under the condition of constant current of 1C. After 1000 cycles of charge and discharge, the capacity retention after 1000 th cycle was calculated according to the following formula:
Figure BDA0003372861880000131
b. high temperature cycle performance
The lithium ion battery is charged to 4.3V under the condition of high temperature (45 ℃) and constant current at 1C, and then discharged to 3.0V under the condition of constant current at 1C. After 500 cycles of charge and discharge, the capacity retention after 500 th cycle was calculated according to the following formula:
Figure BDA0003372861880000132
c. high temperature storage performance
The lithium ion battery is charged and discharged once at 1C/1C under the condition of normal temperature (25 ℃) (the discharge capacity is recorded as DC) 0 ) An initial thickness of D 1 The method comprises the steps of carrying out a first treatment on the surface of the Then charging the battery to 4.3V full power under the condition of 1C constant current and constant voltage; the lithium ion battery (100% SOC) is placed at 70 ℃ and is stored for 48 hours at a temperature of Wen Xiangzhong, and after being taken out, the thickness D is measured 2 The thickness change rate of the lithium ion battery was calculated using the following formula:
Figure BDA0003372861880000133
d. low temperature discharge performance
Charging the prepared battery to 4.3V at constant current of 1.0C under the environment of 25 ℃ until the battery reaches a full charge state (100% SOC); then placing the battery in an environment with the environmental temperature of minus 20 ℃ for 4 hours in an open circuit, then performing discharge test with the 1C multiplying power, recording the 1C discharge capacity at the low temperature of minus 20 ℃, and calculating the ratio of the discharge capacity at the low temperature of minus 20 ℃ to the normal temperature discharge capacity to obtain the 1C discharge efficiency at the low temperature of minus 20 ℃, wherein the test result is shown in the table 1:
TABLE 1
Figure BDA0003372861880000141
Figure BDA0003372861880000151
As can be seen from Table 1, examples 1 to 19 show that the nonaqueous electrolyte additive of the present invention has a sulfur-containing moiety (sulfuric acid group or sulfonic acid group) and a phosphorus-containing moiety (phosphoric acid group or phosphorous acid group), can effectively improve the cycle performance of a lithium ion battery, is particularly suitable for use in a high-nickel ternary system, and can effectively suppress the capacity fade caused by metal elution. The NCM622/AG-4.3V lithium ion battery prepared by the non-aqueous electrolyte additive can reach more than 75.9% in capacity retention rate after 1000 weeks of circulation at 25 ℃, more than 62.7% in capacity retention rate after 500 weeks of circulation at 45 ℃, less than 30.8% in thickness change rate after 48 hours of storage at 100% SOC 70 ℃ and more than 62.2% in 1C discharge efficiency at low temperature of-20 ℃.
From the comparison of the data of examples 4 and 6, examples 13 and 15, the low-temperature discharge performance of the fluorosulfonic acid group is superior to that of lithium alkylsulfonate; the fluorine-based SEI film with inorganic components of lithium fluoride is formed on the surface of the electrode, so that the impedance is low, and the low-temperature discharge performance of the battery is good.
As can be seen from the comparison of the data of examples 2 and 6, the high temperature storage properties of the unsaturated alkyl sulfonic acid groups are superior to those of the saturated alkyl sulfonic acid groups; the unsaturated group has high SEI film resistance formed on the electrode surface due to the polymerization property, which can lead to the reduction of the battery cycle performance and the deterioration of the low-temperature rate performance, however, the side reaction between the electrode and the electrolyte is reduced due to the improvement of the protection of the pole piece, the high-temperature storage performance is improved to a certain extent, and the gas yield is reduced.
From the comparison of the two sets of data of examples 1 and 7, examples 10 and 16, the high temperature storage performance of the unsaturated alkylthio group is superior to that of the saturated alkylthio group; the unsaturated group has high SEI film resistance formed on the electrode surface due to the polymerization property, which can lead to the reduction of the battery cycle performance and the deterioration of the low-temperature rate performance, however, the side reaction between the electrode and the electrolyte is reduced due to the improvement of the protection of the pole piece, the high-temperature storage performance is improved to a certain extent, and the gas yield is reduced.
As can be obtained by comparing the embodiment 1 with the embodiment 17-18, the quality fraction of the additive in the electrolyte can influence the performance of the electrolyte, the electrolyte with better performance can be prepared by controlling the concentration of the additive to be 0.5-2%, and if the concentration of the additive is too low, no obvious effect is obtained; if the concentration of the additive is too high, an increase in impedance and deterioration of circulation are caused.
Comparative example 1 the cycle performance of the lithium ion battery prepared without the first additive or the second additive of the non-aqueous electrolyte additive of the present invention was inferior to that of the lithium ion battery prepared in examples. The electrolyte additive of comparative example 2 has lithium difluorophosphate having a phosphorus-containing moiety, the electrolyte additive of comparative example 3 has vinyl sulfate having a sulfur-containing moiety, and the nonaqueous electrolyte additives of examples 1 to 19 of the present invention having sulfur-containing moieties and phosphorus-containing moieties have comparable lithium ion battery cycle performance.
The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.

Claims (10)

1. The nonaqueous electrolyte additive is characterized by comprising a first additive and/or a second additive, wherein the structural formula of the first additive is shown as formula I, and the structural formula of the second additive is shown as formula II:
Figure FDA0003372861870000011
wherein R in formulas I and II independently comprises any one or a combination of at least two of halogen atom, saturated alkyl group with 1-6 carbon atoms, saturated alkoxy group with 1-6 carbon atoms, unsaturated alkyl group with 1-6 carbon atoms, unsaturated alkoxy group with 1-6 carbon atoms, fluoroalkyl group with 1-6 carbon atoms, fluoroalkoxy group with 1-6 carbon atoms, cyano-substituted alkyl group with 1-6 carbon atoms, cyano-substituted alkoxy group with 1-6 carbon atoms, alkyl group substituted with 1-6 isocyanate groups or alkoxy group substituted with 1-6 isocyanate groups, rf 1 、Rf 2 Independently comprises any one or a combination of at least two of fluorine atom, fluorinated alkyl group with 1-6 carbon atoms, fluorinated alkoxy group with 1-6 carbon atoms, cyano group substituted alkyl group with 1-6 carbon atoms or cyano group substituted alkoxy group with 1-6 carbon atoms.
2. The nonaqueous electrolyte additive according to claim 1, wherein the first additive comprises
Figure FDA0003372861870000012
Figure FDA0003372861870000013
Figure FDA0003372861870000014
Any one or a combination of at least two of these.
3. As in claim 1Or 2, wherein the second additive comprises
Figure FDA0003372861870000021
Figure FDA0003372861870000022
/>
Figure FDA0003372861870000023
Any one or a combination of at least two of these.
4. A nonaqueous electrolyte, characterized in that the nonaqueous electrolyte comprises the nonaqueous electrolyte additive according to any one of claims 1 to 3, and the electrolyte further comprises a lithium salt and a nonaqueous solvent.
5. The nonaqueous electrolyte according to claim 4, wherein the mass fraction of the nonaqueous electrolyte additive is 0.2 to 5%, preferably 0.5 to 2%, based on 100% of the mass of the nonaqueous electrolyte.
6. The nonaqueous electrolyte according to claim 4 or 5, wherein the lithium salt comprises LiPF 6 、LiBF 4 、LiClO 4 、LiAsF 6 、LiN(SO 2 CF 3 ) 2 Or LiN (SO) 2 F) 2 Any one or a combination of at least two of the following;
preferably, the molar concentration of the lithium salt is 0.5 to 2mol/L, preferably 1 to 1.5mol/L.
7. The nonaqueous electrolyte according to any one of claims 4 to 6, wherein the nonaqueous solvent comprises any one or a combination of at least two of a cyclic carbonate, a chain carbonate, a cyclic carboxylic acid ester, a chain carboxylic acid ester, a fluorocarbonate, a carboxylic acid ester, a fluoroether, and a sulfone;
preferably, the nonaqueous solvent comprises any one or a combination of at least two of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethyl acetate, ethyl propionate, propyl propionate, gamma-butyrolactone, methyl acetate, methyl butyrate, ethyl butyrate, or propyl butyrate.
8. The nonaqueous electrolytic solution according to any one of claims 4 to 7, wherein the mass fraction of the nonaqueous solvent is 50 to 85% based on 100% of the mass of the nonaqueous electrolytic solution.
9. The nonaqueous electrolyte according to any one of claims 4 to 8, wherein the electrolyte further comprises a third additive;
preferably, the third additive comprises any one or a combination of at least two of fluoroethylene carbonate, vinylene carbonate, 1, 3-propane sultone, lithium difluorooxalato borate, lithium bisoxalato borate, lithium tetrafluoroborate, lithium difluorobisoxalato phosphate, ethylene carbonate, 1, 3-propenesulfonato lactone, lithium difluorosulfimide, methyldisulfonate, or lithium difluorophosphate;
preferably, the third additive is 0.05 to 20% by mass based on 100% by mass of the nonaqueous electrolytic solution.
10. A lithium ion battery comprising the nonaqueous electrolyte according to any one of claims 4 to 9.
CN202111406088.3A 2021-11-24 2021-11-24 Non-aqueous electrolyte additive and application thereof Pending CN116169354A (en)

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