WO2023066404A1 - 双取代二卤素磷酸酯类添加剂及其制备方法和应用 - Google Patents

双取代二卤素磷酸酯类添加剂及其制备方法和应用 Download PDF

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WO2023066404A1
WO2023066404A1 PCT/CN2022/129225 CN2022129225W WO2023066404A1 WO 2023066404 A1 WO2023066404 A1 WO 2023066404A1 CN 2022129225 W CN2022129225 W CN 2022129225W WO 2023066404 A1 WO2023066404 A1 WO 2023066404A1
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lithium
dihalogen
disubstituted
phosphate
temperature
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French (fr)
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贾国文
朱振涛
武燕
牛庆荣
于鑫
李超
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山东海科创新研究院有限公司
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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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/655—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having oxygen atoms, with or without sulfur, selenium, or tellurium atoms, as the only ring hetero atoms
    • C07F9/65515—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having oxygen atoms, with or without sulfur, selenium, or tellurium atoms, as the only ring hetero atoms the oxygen atom being part of a five-membered ring
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the application relates to the technical field of lithium-ion battery materials, in particular to a disubstituted dihalogen phosphate additive and its preparation method and application.
  • Lithium difluorophosphate (LIDFP) has excellent film-forming properties, which can improve the cycle stability and high and low temperature performance of lithium-ion batteries. As a new type of lithium salt additive, it is a material with good application prospects. However, when lithium difluorophosphate is added to the lithium ion electrolyte, the solubility is low. If a large amount of lithium difluorophosphate is added, the electrolyte will become turbid. Therefore, the addition amount of lithium difluorophosphate in the electrolyte is only limited to about 2%, which is difficult to commercialize.
  • the first aspect of the embodiment of the present application provides a disubstituted dihalogen phosphate additive, the molecular formula of which is shown in formula A1 or A2 :
  • R 1 and R 2 is represented by structural formula R
  • R 3 and R 4 is represented by structural formula R
  • the remaining two groups are selected from H, halogen atoms, C1-C5 Alkane groups or haloalkane groups.
  • the second aspect of the embodiments of the present application provides a method for preparing the disubstituted dihalogen phosphate additive described in any one of the above schemes, comprising the following steps:
  • the difluorophosphoric acid and the reaction solution are condensed and refluxed using a condenser tube during the dropwise addition process, and the temperature of the condenser tube is controlled at -20 ⁇ -50°C.
  • the halogen-containing gas introduced is a fluorine-nitrogen mixed gas
  • the catalyst tributyltin fluoride is added, and during the process of adding difluorophosphoric acid dropwise, the mixed solution The temperature of the solution is controlled at 0-5°C, and it is allowed to stand for 1.5-2.5 hours after the addition is completed;
  • the halogen-containing gas introduced is a fluorine-nitrogen mixed gas, and no catalyst is added.
  • the temperature of the mixed solution is controlled at 25-35°C. Stand still for 1.5 ⁇ 2.5h;
  • the halogen-containing gas introduced is chlorine gas, and the catalyst ruthenium trichloride is added.
  • the temperature of the mixed solution is controlled at 25-35°C. Let stand for 1.5-2.5 hours.
  • the reaction time in step 3) is 1.5-2.5 hours.
  • impurity removal is also included, and the impurity removal method is to perform suction filtration, nitrogen bubbling and vacuum rectification in sequence; the vacuum rectification The vacuum degree at the time is 30-100pa, and the reflux ratio is 1:4.
  • the third aspect of the embodiments of the present application also provides a disubstituted dihalogen phosphate additive described in any one of the above schemes or any one of the above methods to prepare the disubstituted dihalogen phosphate additive in the preparation of lithium ion electrolysis application in liquid.
  • the added amount of the disubstituted dihalogen phosphate additive is 0.1%-7% of the total mass of the electrolyte.
  • the electrolyte also includes lithium salts, organic solvents and auxiliary additives.
  • the auxiliary additives include vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, succinonitrile, adiponitrile, hexanetrinitrile, fluorobenzene, vinylene sulfate ester, vinyl sulfate, tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonimide and bis(oxalylboronic acid) One or more of lithium.
  • the disubstituted dihalogen phosphate additive provided in at least one embodiment of the present application can not only provide cyclic sulfate ester groups to stabilize the SEI film, but also provide dihalogen phosphate to further improve the stability of the battery, And it has high solubility in lithium-ion battery electrolyte.
  • the disubstituted dihalophosphate additives provided in at least one embodiment of the present application contain dihalophosphate groups, cyclic sulfates or cyclic sulfites.
  • the additive acts on the electrolyte
  • the The sulfuric acid or sulfurous acid group forms a lithium sulfate ester lithium salt compound on the positive electrode of the lithium-ion battery.
  • This substance can form a good SEI film, reduce the impedance of the electrolyte, and improve the low-temperature cycle performance of the lithium-ion battery.
  • the unique dihalogen phosphate group can reduce the impedance increase caused by adding a large amount of single acidic cyclic sulfate additive itself, which can strengthen the SEI film, further strengthen the SEI film and reduce the impedance of the SEI film, and It can also further avoid the problem of low solubility of difluorophosphate in the electrolyte solution of lithium-ion batteries, which in turn causes the electrolyte solution to be turbid.
  • the substitution of hydrogen by halogen atoms will lead to lower activation energy and lower HOMO and LUMO energy levels, resulting in higher reduction and oxidation potentials.
  • the high reduction potential can form an effective SEI film, which inhibits further electrolyte decomposition and significantly improves the cycle performance of the battery.
  • Fig. 1 is the infrared spectrogram of the disubstituted dihalogen phosphate of the cis structure prepared in Example 1;
  • Fig. 2 is the infrared spectrogram of the trans-structure disubstituted dihalogen phosphate prepared in Example 2.
  • the first aspect of the embodiments of the present application provides a disubstituted dihalophosphate additive, the molecular formula of which is shown in formula A1 or A2 :
  • R 1 and R 2 is represented by structural formula R
  • R 3 and R 4 is represented by structural formula R
  • the remaining two groups are selected from H, halogen atoms, C1-C5 Alkane groups or haloalkane groups.
  • the disubstituted dihalogen phosphate additives provided in the examples of this application contain dihalogen phosphate groups, cyclic sulfate or cyclic sulfite at the same time.
  • the sulfuric acid or sulfurous acid therein The group forms a sulfate ester lithium salt compound on the positive electrode of the lithium-ion battery.
  • This substance can form a good SEI film, reduce the impedance of the electrolyte, and improve the low-temperature cycle performance of the lithium-ion battery.
  • the unique dihalogen phosphate group can reduce the impedance increase caused by adding a large amount of single acidic cyclic sulfate additive itself, which can strengthen the SEI film, further strengthen the SEI film and reduce the impedance of the SEI film, and It can also further avoid the problem of low solubility of difluorophosphate in the electrolyte solution of lithium-ion batteries, which in turn causes the electrolyte solution to be turbid.
  • the substitution of hydrogen by halogen atoms will lead to lower activation energy and lower HOMO and LUMO energy levels, resulting in higher reduction and oxidation potentials.
  • the high reduction potential can form an effective SEI film, which inhibits further electrolyte decomposition and significantly improves the cycle performance of the battery.
  • the second aspect of the embodiments of the present application provides a method for preparing the disubstituted dihalogen phosphate additive described in any one of the above embodiments, comprising the following steps:
  • vinyl sulfate or vinyl sulfite was mixed with an organic solvent, with or without a catalyst, to obtain a mixed solution.
  • the ratio of the vinyl sulfate or vinyl sulfite to the organic solvent is not particularly limited, as long as the added organic solvent can dissolve the vinyl sulfate or vinyl sulfite, and adding the organic solvent can reduce the The severity of the reaction plays a role in protecting the reaction system.
  • the organic solvent is one or a mixture of acetonitrile, ethylene glycol dimethyl ether, and ethyl acetate.
  • the halogen-containing gas introduced is a mixed gas of fluorine and nitrogen, and tributyltin fluoride is optionally used as a catalyst.
  • the halogen-containing gas introduced is a mixed gas of fluorine and nitrogen, and no catalyst is optionally added.
  • the halogen-containing gas introduced is chlorine gas, and ruthenium trichloride is optionally used as a catalyst.
  • the temperature of the mixed solution is controlled at 0-5°C, and it is allowed to stand for 1.5-2.5 hours after the dropwise addition is completed;
  • the halogen-containing gas introduced is a fluorine-nitrogen mixed gas, and no catalyst is added.
  • the temperature of the mixed solution is controlled at 25-35°C. Stand still for 1.5 ⁇ 2.5h;
  • the halogen-containing gas introduced is chlorine gas, and the catalyst ruthenium trichloride is added.
  • the temperature of the mixed solution is controlled at 25-35°C. Let stand for 1.5-2.5 hours.
  • a halogen-containing gas is introduced into the mixed solution for halogenation, and difluorophosphoric acid is added dropwise after the halogenation is completed.
  • a condenser tube may be used to condense and reflux the difluorophosphoric acid and the reaction solution during the dropwise addition process, and the temperature of the condenser tube may optionally be controlled at -20 to -50°C .
  • the difluorophosphoric acid when the temperature of the condenser tube is controlled at -20 to -50°C, the difluorophosphoric acid can be kept in a condensed state, preventing it from volatilizing and escaping from the system, facilitating the dropwise addition reaction.
  • the catalyst tributyltin fluoride when vinyl sulfate is used as the raw material, the catalyst tributyltin fluoride is added, and during the process of adding difluorophosphoric acid dropwise, the temperature of the mixed solution can optionally be controlled at 0-5°C. It is preferable to stand still for 1.5-2.5 hours after the addition is completed; when vinyl sulfite is used as the raw material, during the process of adding difluorophosphoric acid dropwise, the temperature of the mixed solution can optionally be controlled at 25-35°C, and it can be Stand still for 1.5-2.5 hours.
  • the volume ratio of fluorine and nitrogen in the fluorine-nitrogen mixed gas is optionally 1:4.
  • the feed rate of the fluorine-nitrogen mixed gas is optionally 0.3-0.5 L/min, further optionally 0.4 L/min.
  • the gradient temperature of the embodiment of the present application is raised to 60-70° C. for reaction to obtain disubstituted dihalogen phosphate additives.
  • the gradient temperature is increased by 10° C. every 1 h until the temperature reaches 60-70° C.
  • the reaction time is 1.5-2.5 hours.
  • the disubstituted dihalogen phosphate additives described in the present application can be prepared by the above method, and the obtained disubstituted dihalogen phosphate contains both cis and trans structures.
  • impurity removal is also included, and the impurity removal method is optionally sequentially performing suction filtration, nitrogen bubbling, and vacuum distillation.
  • the vacuum degree during the vacuum distillation is 30-100 Pa, and the reflux ratio is 1:4.
  • the third aspect of the embodiments of the present application provides a disubstituted dihalophosphate additive described in any one of the above embodiments or any one of the methods above to prepare the disubstituted dihalophosphate additive in the preparation of lithium ion electrolysis application in liquid.
  • the added amount of the disubstituted dihalogen phosphate additive is optionally 0.1%-7% of the total mass of the electrolyte.
  • lithium salts, organic solvents, and auxiliary additives are also included in the electrolyte; the auxiliary additives optionally include vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, succinonitrile , adiponitrile, hexanetrinitrile, fluorobenzene, vinylene sulfate, vinyl sulfate, tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphate, lithium difluorophosphate, One or more of lithium tetrafluoroborate, lithium bisfluorosulfonimide and lithium bisoxalate borate.
  • the fourth aspect of the embodiments of the present application provides a lithium-ion battery, including a positive electrode sheet, a negative electrode sheet, a separator, and the lithium-ion battery electrolyte provided in the above embodiments.
  • the reactor was purged with dry nitrogen, and 124g (1mol) of vinyl sulfate (CAS1072-53-3) was added into a 1L four-neck flask, and the external water bath of the reactor was controlled at 0°C, and then 300g of acetonitrile solvent was added to dissolve, and 0.5g of tributyltin fluoride (1983-10-4) was used as catalyst.
  • the ventilation rate is 0.4L/min, and an external secondary anti-suckback gas is connected absorption device.
  • the constant pressure dropping funnel controls the dropwise addition of difluorophosphoric acid within 2h. After the dropwise addition, let it stand for 2h, then slowly increase the temperature (1h/10°C) to 60°C, and react at 60°C for 2h, remove the catalyst by suction filtration , The solution was bubbled with nitrogen to remove moisture and residual fluorine.
  • the molecular structural formula of the cis-structure product A1 is:
  • R2 and R3 are:
  • R1 and R3 are:
  • the absorption peak at 784.2 cm -1 and 927.09 cm -1 corresponds to the stretching vibration of the left and right CO bonds on the sulfate ring peak, and affected by the F element, the polarity change shifts.
  • 887.78cm -1 corresponds to the stretching vibration peak of the cyclic sulfate ring bond
  • 1005.88cm -1 and 1365.39cm -1 correspond to the stretching vibration peaks of the two CF bonds at the bottom
  • the stretching vibration peak at 1157.59cm -1 and 1259.62cm -1
  • the vibration peak is the comprehensive stretching vibration peak of the PF bond
  • the purity of the final product was 99.2% for the cis structure A1 , 99.4% for the trans structure, and 83.19% for the combined yield of the cis and trans structures, including 41% for the cis structure and 59% for the trans structure.
  • the detection method of purity is: adopt ion chromatography to detect the purity of product, utilize the area normalization method of ion chromatography to test.
  • the cis and trans structures are distinguished by infrared spectroscopy, and the structures are pre-distinguished, followed by purity testing by chromatography.
  • the reaction is designed according to the molar ratio. According to the reaction equation, 1 mol of sulfuric acid ester or vinyl sulfite will generate 1 mol of theoretical dihalogen phosphate species, and the mass of the obtained substance is divided by the mass of the theoretically obtained substance, which is the reaction yield.
  • the reactor was purged with dry nitrogen, and 108g (1mol) of vinyl sulfite (CAS3741-38-6) was added into a 1L four-necked flask, and the external water bath of the reactor was controlled at 30°C, and then 300g of acetonitrile solvent was added for dissolution.
  • difluorophosphoric acid is added dropwise. During the reaction process, the temperature is strictly controlled below 30°C. At the same time, the mixed gas of fluorine and nitrogen is turned on for ventilation. The ventilation rate is 0.4L/min, and the external secondary anti-suckback gas absorption device.
  • the constant pressure dropping funnel controls the dropwise addition of difluorophosphoric acid within 2 hours. After the dropwise addition is completed, let it stand for 2.5 hours, then slowly increase the temperature (1h/10°C) to 70°C, and react at 70°C for 2 hours, then suction filter. The solution was bubbled with nitrogen to remove moisture and residual fluorine.
  • the molecular structural formula of the cis structure product A2 is:
  • R2 and R3 are:
  • R1 and R3 are:
  • the absorption peaks at 783.89cm -1 and 889.16cm -1 correspond to the left and right CO on the sulfite ring.
  • the stretching vibration peak of the bond is affected by the F element, and the polarity change is shifted.
  • 870.28cm -1 corresponds to the stretching vibration peak of the cyclic sulfite ring bond
  • 1120.83cm -1 and 1471.84cm -1 correspond to the stretching vibration peaks of the two CF bonds at the bottom
  • the stretching vibration peak is the comprehensive stretching vibration peak of the PF bond
  • the purity of the final product was 99.7% for the cis structure A2 , 99.9% for the trans structure A2 , and the combined yield of the two structures was 89.46%, of which 39% for the cis structure and 61% for the trans structure.
  • the reactor was purged with dry nitrogen, and 108g (1mol) of vinyl sulfite (CAS3741-38-6) was added into a 1L four-necked flask, and the external water bath of the reactor was controlled at 30°C, and then 300g of ethyl acetate solvent was added to carry out Dissolve, add 0.05 g of anhydrous ruthenium trichloride into the reactor, and pass chlorine gas to one side of the four-necked flask for chlorination. Turn on the chlorine gas for ventilation, the ventilation rate is 0.4L/min, and an external secondary anti-suckback gas absorption device is connected. After chlorination for 5 hours, high-purity nitrogen gas was blown to remove chlorine for 0.5 hours. After the solution became colorless, the mixture of dichloroethylene sulfite and ethyl acetate was stored in a four-neck flask for later use.
  • the four-necked flask was connected with a condenser tube, the temperature of the external water bath was kept constant, and a condenser tube was added, and the condensation temperature was -30°C, then 209g (2.05mol) of anhydrous difluorophosphoric acid (13779-41-4) was added into a 500ml dropping funnel, When the temperature of the system reaches 30°C, add difluorophosphoric acid dropwise. The reaction process strictly controls the temperature below 30°C. At the same time, the constant pressure dropping funnel controls the dropwise addition of difluorophosphoric acid within 2 hours. Then gradually increase the temperature gradually (1h/10°C) to 70°C, react at 70°C for 2.5h, and filter with suction.
  • Filtrate transfer carries out rectification under reduced pressure, gained solution is put in 1L round-bottomed flask, utilizes 5225 fractionating head to add 1m tool explosion-proof ring silver-plated double-layer glass spring rectification column to carry out fractionation (vacuum tightness 30-100pa, reflux ratio 1: 4), wherein the front fraction is ethyl acetate, difluorophosphoric acid and other impurities, the fraction at 75-84°C in the middle section is cis structure A 2 , and the fraction at 90-101°C is trans structure A 2 .
  • the purity of the final product was 99.1% for the cis structure and 99.6% for the trans structure, and the combined yield of the two structures was 79.5%, of which 37% for the cis structure and 63% for the trans structure.
  • the molecular structural formula of the cis structure product A2 is:
  • R2 and R3 are:
  • R1 and R3 are:
  • the disubstituted dihalogen phosphate prepared in Examples 1-3 is used as an additive, and is added to the electrolyte in different amounts to prepare a lithium-ion battery.
  • the specific scheme is shown in Table 1 (wherein scheme 19 and scheme 20
  • the added A2 is prepared in Example 3, and A2 in other schemes is prepared by using Example 2), and the electrolyte also includes lithium hexafluorophosphate (concentration is 1mol/L) in addition to the ingredients added in Table 1 , an organic solvent (a mixture of ethylene carbonate, diethyl carbonate and dimethyl carbonate prepared in a mass ratio of 3:5:2).
  • the preparation method of the lithium-ion battery electrolyte is as follows: mix ethylene carbonate, diethyl carbonate and dimethyl carbonate uniformly, then add lithium hexafluorophosphate and stir evenly, and finally add the disubstituted dihalogen phosphate additives provided in this example and Auxiliary additives.
  • the battery performance of the prepared lithium-ion battery was tested, and the specific test results are shown in Table 2.
  • the specific test method is as follows:
  • S1 Charge the lithium-ion battery at 25°C with a constant current of 1C to 4.6V, charge with a constant voltage until the cut-off current is 0.05C, and then discharge it with a constant current of 1C to 3.0V, which is recorded as a charge-discharge cycle.
  • the average capacity of three cycles is the initial capacity C 0 , and the volume of the tested lithium-ion battery is recorded as V 0 ;
  • Capacity recovery rate C 2 /C 0 *100%
  • the lithium-ion battery At 25°C, charge the lithium-ion battery with a constant current of 1C to 4.6V, charge it with a constant voltage until the cut-off current is 0.05C, discharge it with a constant current of 1C to 3.0V, and record the discharge capacity; then charge it with a constant current of 1C to 4.6V , charged at a constant voltage to a cut-off current of 0.05C, placed in a -20°C environment for 24 hours, and then discharged to 2.4V at a constant current of 1C, and the discharge capacity was recorded.
  • the preparation method of lithium-ion battery positive electrode sheet and negative electrode sheet is as follows:
  • the preparation method of the positive electrode sheet is: mix nickel-cobalt lithium manganese oxide (LiNi 0.5 Co 0.2 Mn 0.3 ), small particle conductive carbon black (Super-P), carbon nanotubes (CNT) and polyvinylidene fluoride (PVDF), and then the mixture is dispersed in N-methylpyrrolidone, and stirred until stable and uniform under the action of a vacuum mixer to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on On an aluminum foil with a thickness of 16 ⁇ m, the aluminum foil coated with the positive electrode slurry was left to dry at room temperature, and then transferred to a blast oven at 120°C to dry for 3 hours, and the positive electrode sheet was obtained by cold pressing and die-cutting.
  • NiNi 0.5 Co 0.2 Mn 0.3 small particle conductive carbon black
  • CNT carbon nanotubes
  • PVDF polyvinylidene fluoride
  • the preparation method of the negative plate is: mix graphite, small particle conductive carbon black (Super-P), styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) by mass ratio 94.5:2:1.5:2, then the mixture Disperse in deionized water to obtain a negative electrode slurry; apply the negative electrode slurry evenly on a copper foil with a thickness of 8 ⁇ m, dry the copper foil coated with the negative electrode slurry at room temperature, and then transfer it to a drum at 120 ° C Dry in an air oven for 3 hours, and then obtain negative electrode sheets by cold pressing and die-cutting.
  • Super-P small particle conductive carbon black
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • the manufacturing method of the lithium-ion battery is as follows: the prepared positive electrode sheet, negative electrode sheet and diaphragm are laminated to obtain a bare cell; after the bare cell is put into a packaging case, the electrolyte is injected and sealed, and after standing, Lithium-ion batteries are manufactured through hot and cold pressing, chemical formation, and capacity separation processes.
  • the A 1 and A 2 substances can improve the performance of lithium-ion batteries. Furthermore, the combination of trans A1 and trans A2 can further improve the high and low temperature performance of the battery and reduce the internal resistance, because the trans structure is more stable than the cis structure, and the formed SEI film will be more stable. It is stable, and due to the film-forming properties of difluorophosphate, adding a small amount of its internal resistance will not cause a further increase in its internal resistance due to the increase in film thickness. With the further increase of the added amount, the internal resistance will continue to increase, and the corresponding performance will decline. In Scheme 22, turbidity occurs when the amount of lithium difluorophosphate added is greater than 2.5%.
  • additives A 1 and A 2 can be added in an amount greater than the limit of 2.5%. Therefore, the novel additive in the embodiment of the present application can enhance the performance of the lithium-ion battery, and is a good additive material. At the same time, we can also see from the results that a small amount of difluorophosphate additives made by chlorination (about 2%) can protect lithium-ion batteries, but as the amount of addition increases, lithium-ion batteries The performance of the battery began to decline.

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Abstract

双取代二卤素磷酸酯类添加剂及其制备方法和应用。添加剂的分子式如式A 1 或A 2 A2 所示，其中，R 1与R 2其中的一个基团为结构式R R 所示，R 3与R 4其中的一个基团为结构式R所示，剩余两个基团相同，选自H、卤素原子、C1～C5的烷烃基或卤代烷烃基。

Description

双取代二卤素磷酸酯类添加剂及其制备方法和应用
本申请要求在2022年05月23日提交中国专利局、申请号为202210559361.4、申请名称为“双取代二卤素磷酸酯类添加剂及其制备方法和应用”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及锂离子电池材料技术领域，具体涉及双取代二卤素磷酸酯类添加剂及其制备方法和应用。
背景技术
二氟磷酸锂(LIDFP)具有优秀的成膜性能，可以很好的改善锂离子电池的循环稳定性及高低温性能，作为一种新型的锂盐添加剂是一种应用前景良好的材料。但是二氟磷酸锂添加于锂离子电解液中时溶解性较低，如果加入大量的二氟磷酸锂，电解液会发生浑浊的现象。因此二氟磷酸锂的在电解液中的添加量仅仅限制在百分之二左右，难以进行商业化。
二氟磷酸锂中，对电池起到关键性能提升的要素是其中含有二氟磷酸根，因此含有二氟磷酸根的二氟磷酸酯类添加剂就应运而生。然而，目前对于二氟磷酸酯的研究还在初期阶段，现有技术中有采用二氟磷酸甲酯，二氟磷酸乙酯来提供二氟磷酸根的技术方案，但二氟磷酸甲酯，二氟磷酸乙酯容易水解，也容易歧化，转化成一氟磷酸酯与三氟氧磷，导致纯度迅速下降。
发明内容
为了解决现有技术中存在的以上至少一个不足之处，本申请实施例的第一方面提供了一种双取代二卤素磷酸酯类添加剂，所述添加剂的分子式如式A 1或A 2所示：
Figure PCTCN2022129225-appb-000001
其中，R 1与R 2其中的一个基团为结构式R所示，R 3与R 4其中的一个基团为结构式R所示，剩余两个基团相同选自H、卤素原子、C1～C5的烷烃基或卤代烷烃基。
本申请实施例的第二方面提供了一种上述任意一项方案所述的双取代二卤素磷酸酯类添加剂的制备方法，包括如下步骤：
1)将硫酸乙烯酯或亚硫酸乙烯酯与有机溶剂混合，加或不加催化剂，得 到混合溶液；
2)在混合溶液中通入含卤素气体进行卤化，待卤化完成后滴加二氟磷酸；
3)待二氟磷酸滴加完成后，梯度升温至60～70℃，进行反应，得到双取代二卤素磷酸酯类添加剂。
在本申请的一些实施例中，所述步骤2)中滴加二氟磷酸时，在滴加过程中利用冷凝管对二氟磷酸及反应液进行冷凝回流，冷凝管的温度控制在-20～-50℃。
在本申请的一些实施例中，采用硫酸乙烯酯为原料时，通入的含卤素气体为氟氮混合气，添加催化剂三丁基氟化锡，在滴加二氟磷酸的过程中，混合溶液的温度控制在0～5℃，滴加完成后静置1.5～2.5h；
采用亚硫酸乙烯酯为原料时，通入的含卤素气体为氟氮混合气，不添加催化剂，在滴加二氟磷酸的过程中，混合溶液的温度控制在25～35℃，滴加完成后静置1.5～2.5h；
采用亚硫酸乙烯酯为原料时，通入的含卤素气体为氯气，添加催化剂三氯化钌，在滴加二氟磷酸的过程中，混合溶液的温度控制在25～35℃，滴加完成后静置1.5～2.5h。
在本申请的一些实施例中，所述步骤3)中反应的时间为1.5～2.5h。
在本申请的一些实施例中，所述步骤3)中反应结束后还包括除杂，所述除杂的方式为依次进行抽滤、氮气鼓泡和减压精馏；所述减压精馏时的真空度为30～100pa，回流比为1:4。
本申请实施例的第三方面还提供了一种上述任意一项方案所述的双取代二卤素磷酸酯类添加剂或上述任意一项方法制备得到双取代二卤素磷酸酯类添加剂在制备锂离子电解液中的应用。
在本申请的一些实施例中，所述双取代二卤素磷酸酯类添加剂的添加量为电解液总质量的0.1％～7％。
在本申请的一些实施例中，所述电解液中还包括锂盐、有机溶剂和辅助添加剂。
在本申请的一些实施例中，所述辅助添加剂包括碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯、丁二腈、己二腈、己烷三腈、氟苯、硫酸亚乙烯酯、硫酸乙烯酯、三(三甲基硅基)硼酸酯、三(三甲基硅基)磷酸酯、二氟磷酸锂、四氟硼酸锂、双氟磺酰亚胺锂和双草酸硼酸锂中的一种或几种。
本申请相较于现有技术取得了以下技术效果：
(1)本申请至少一个实施例所提供的双取代二卤素磷酸酯类添加剂，既可以提供环状硫酸酯基团，稳固SEI膜，也可以提供二卤素磷酸根，进一步提升电池的稳定性，且在锂离子电池电解液中溶解度高。
(2)本申请至少一个实施例所提供的双取代二卤素磷酸酯类添加剂中，同时含有二卤素磷酸基团、环状硫酸酯或环状亚硫酸酯，该添加剂作用于电解液时，其中的硫酸或亚硫酸基团于锂离子电池正极形成硫酸酯类锂盐化合物，该物质可以形成良好的SEI膜，降低电解液的阻抗，提升锂离子电池的低温循环性能。而特有的二卤素磷酸基团可以降低添加多量单一的酸性环状硫酸酯类添加剂本身带来的阻抗增加，可以起到增强SEI膜的作用，进一步补强SEI膜且降低SEI膜的阻抗，而且还可以进一步避免二氟磷酸盐在锂离子电池电解液中溶解度低，进而造成电解液浑浊的问题。卤素原子取代氢会导致活化能降低并降低HOMO和LUMO能级，从而导致还原电位和氧化电位升高。高的还原电位可形成有效的SEI膜，其抑制进一步的电解液分解并明显改善电池的循环性能。
附图说明
此处所说明的附图用来提供对本申请的进一步理解，构成本申请的一部分，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。在附图中：
图1为实施例1制备得到的顺式结构的双取代二卤素磷酸酯的红外光谱图；
图2为实施例2制备得到的反式结构的双取代二卤素磷酸酯的红外光谱图。
具体实施方式
本申请实施例的第一方面提供了一种双取代二卤素磷酸酯类添加剂，所述添加剂的分子式如式A 1或A 2所示：
Figure PCTCN2022129225-appb-000002
Figure PCTCN2022129225-appb-000003
其中，R 1与R 2其中的一个基团为结构式R所示，R 3与R 4其中的一个基团为结构式R所示，剩余两个基团相同选自H、卤素原子、C1～C5的烷烃基或卤代烷烃基。
本申请实施例所提供的双取代二卤素磷酸酯类添加剂中，同时含有二卤素磷酸基团、环状硫酸酯或环状亚硫酸酯，该添加剂作用于电解液时，其中的硫酸或亚硫酸基团于锂离子电池正极形成硫酸酯类锂盐化合物，该物质可以形成良好的SEI膜，降低电解液的阻抗，提升锂离子电池的低温循环性能。而特有的二卤素磷酸基团可以降低添加多量单一的酸性环状硫酸酯类添加剂本身带来的阻抗增加，可以起到增强SEI膜的作用，进一步补强SEI膜且降低SEI膜的阻抗，而且还可以进一步避免二氟磷酸盐在锂离子电池电解液中溶解度低，进而造成电解液浑浊的问题。卤素原子取代氢会导致活化能降低并降低HOMO和LUMO能级，从而导致还原电位和氧化电位升高。高的还 原电位可形成有效的SEI膜，其抑制进一步的电解液分解并明显改善电池的循环性能。
本申请实施例的第二方面提供了一种上述任意一项实施例所述的双取代二卤素磷酸酯类添加剂的制备方法，包括如下步骤：
1)将硫酸乙烯酯或亚硫酸乙烯酯与有机溶剂混合，加或不加催化剂，得到混合溶液；
2)在混合溶液中通入含卤素气体进行卤化，待卤化完成后滴加二氟磷酸；
3)待二氟磷酸滴加完成后，梯度升温至60～70℃，进行反应，得到双取代二卤素磷酸酯类添加剂。
本申请实施例将硫酸乙烯酯或亚硫酸乙烯酯与有机溶剂混合，加或不加催化剂，得到混合溶液。在本申请的实施例中，所述硫酸乙烯酯或亚硫酸乙烯酯与有机溶剂的比例没有特殊限定，添加的有机溶剂能够溶解硫酸乙烯酯或亚硫酸乙烯酯即可，同时添加有机溶剂可降低反应的剧烈程度，起到保护反应体系的作用。在一些实施例中，所述有机溶剂为乙腈、乙二醇二甲醚、乙酸乙酯中的一种或两种混合。
在本申请中，当采用硫酸乙烯酯为原料时，通入的含卤素气体为氟氮混合气，可选地采用三丁基氟化锡作为催化剂。当采用亚硫酸乙烯酯为原料时，通入的含卤素气体为氟氮混合气，可选地不添加催化剂。当采用亚硫酸乙烯酯为原料时，通入的含卤素气体为氯气，可选地采用三氯化钌作为催化剂。
在滴加二氟磷酸的过程中，混合溶液的温度控制在0～5℃，滴加完成后静置1.5～2.5h；
采用亚硫酸乙烯酯为原料时，通入的含卤素气体为氟氮混合气，不添加催化剂，在滴加二氟磷酸的过程中，混合溶液的温度控制在25～35℃，滴加 完成后静置1.5～2.5h；
采用亚硫酸乙烯酯为原料时，通入的含卤素气体为氯气，添加催化剂三氯化钌，在滴加二氟磷酸的过程中，混合溶液的温度控制在25～35℃，滴加完成后静置1.5～2.5h。
得到混合溶液后，本申请实施例在混合溶液中通入含卤素气体进行卤化，待卤化完成后滴加二氟磷酸。在一些实施例中，滴加二氟磷酸时，在滴加过程中可选地采用冷凝管对二氟磷酸及反应液进行冷凝回流，冷凝管的温度可选地控制在-20～-50℃。在一些实施例中，将冷凝管的温度控制在-20～-50℃时，可以使得二氟磷酸处于冷凝状态，防止其产生挥发，逸出体系，便于进行滴加反应。
在本申请实施例中，当采用硫酸乙烯酯为原料时，添加催化剂三丁基氟化锡，在滴加二氟磷酸的过程中，混合溶液的温度可选地控制在0～5℃，滴加完成后优选静置1.5～2.5h；当采用亚硫酸乙烯酯为原料时，在滴加二氟磷酸的过程中，混合溶液的温度可选地控制在25～35℃，滴加完成后可选地静置1.5～2.5h。
在本申请实施例中，所述氟氮混合气中氟和氮的体积比可选地为1:4。在本申请中，所述氟氮混合气的通入量可选地为0.3～0.5L/min，进一步可选地为0.4L/min。
待二氟磷酸滴加完成后，本申请实施例的梯度升温至60～70℃，进行反应，得到双取代二卤素磷酸酯类添加剂。在一些实施例中，所述梯度升温时为每1h升温10℃，直至升温至60～70℃。在一些实施例中，所述反应的时间为1.5～2.5h。
本申请实施例通过上述方法可制备得到本申请中所述的双取代二卤素磷 酸酯类添加剂，得到的双取代二卤素磷酸酯类中含有顺式和反式两种结构。
反应结束后，在一些实施例中，还包括除杂，所述除杂的方式可选地为依次进行抽滤、氮气鼓泡和减压精馏。在一些实施例中，所述减压精馏时的真空度为30～100pa，回流比为1:4。
本申请实施例的第三方面提供了一种上述任意一项实施例所述的双取代二卤素磷酸酯类添加剂或上述任意一项方法制备得到双取代二卤素磷酸酯类添加剂在制备锂离子电解液中的应用。
在一些实施例中，所述双取代二卤素磷酸酯类添加剂的添加量可选地为电解液总质量的0.1％～7％。
在一些实施例中，所述电解液中还包括锂盐、有机溶剂和辅助添加剂；所述辅助添加剂可选地包括碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯、丁二腈、己二腈、己烷三腈、氟苯、硫酸亚乙烯酯、硫酸乙烯酯、三(三甲基硅基)硼酸酯、三(三甲基硅基)磷酸酯、二氟磷酸锂、四氟硼酸锂、双氟磺酰亚胺锂和双草酸硼酸锂中的一种或几种。
本申请实施例的第四方面提供了一种锂离子电池，包括正极片、负极片、隔膜和以上实施例提供的锂离子电池电解液。
为了进一步说明本申请，下面结合具体实施例对本申请提供的技术方案进行详细地描述，但不能将它们理解为对本申请保护范围的限定。
实施例1
首先对反应器进行干燥氮气吹扫，取124g(1mol)硫酸乙烯酯(CAS1072-53-3)加入到1L四口烧瓶内，控制反应器外部水浴0℃，随后加入300g乙腈溶剂进行溶解，加入0.5g三丁基氟化锡(1983-10-4)作为催化剂。四口烧瓶接冷凝管，冷凝温度为-30℃，外加机械搅拌，随后将209g (2.05mol)无水二氟磷酸(13779-41-4)加入500ml滴液漏斗内，四口烧瓶通氟氮混合气(F 2:N 2＝1:4)进行氟化。待体系温度达到0℃时，滴加二氟磷酸，反应过程严格控制温度在5℃以下，同时打开氟氮混合气，进行通气，通气量为0.4L/min，外接二级防倒吸气体吸收装置。恒压滴液漏斗控制二氟磷酸2h内滴加完成，滴加完成后，静置2h，随后缓慢梯度升温(1h/10℃)，升至60℃，60℃反应2h后，抽滤去除催化剂，溶液进行氮气鼓泡，去除水分及残留氟气。转移进行减压精馏，将所得溶液放至1L圆底烧瓶内，利用5225分馏头外加1m具防爆环镀银双层玻璃弹簧精馏柱进行分馏(真空度30-100pa，回流比1:4)，其中前馏分为乙腈与二氟磷酸及其他杂质，取中段60-75℃馏分为顺式结构产物A 1，具体红外图谱如图1所示，80-90℃馏分为反式结构产物A 1，后馏分为硫酸乙烯酯分解产物及焦油。
顺式结构产物A 1的分子结构式为：
Figure PCTCN2022129225-appb-000004
其中R 2和R 3为：
Figure PCTCN2022129225-appb-000005
反式结构产物A 1的分子结构式为
Figure PCTCN2022129225-appb-000006
其中R 1和R 3为：
Figure PCTCN2022129225-appb-000007
由图1可以看出：649.12cm -1处对应S＝0键的伸缩振动峰，784.2cm -1，927.09cm -1处的吸收峰，对应硫酸酯环上的左右两个C-O键的伸缩振动峰，并受F元素影响，极性变化发生偏移。887.78cm -1处对应环状硫酸酯环键的伸缩振动峰，1005.88cm -1与1365.39cm -1对应底端两种C-F键的伸缩振动峰，1157.59cm -1与1259.62cm -1处的伸缩振动峰为P-F键的综合伸缩振动峰，956.06cm -1处为一端P＝O键的伸缩振动峰，另一端与前段红外谱图发生重合。
最终产物纯度顺式结构A 1为99.2％，反式结构纯度为99.4％，顺反两种结构综合产率83.19％，其中顺式结构为41％，反式结构为59％。
其中纯度的检测方法为：采用离子色谱检测产物的纯度，利用离子色谱的面积归一法进行测试。顺式与反式结构利用红外光谱进行区分，预先区分出结构，随后利用色谱进行纯度检测。
产率计算方法：反应按照摩尔比进行设计，根据反应方程式，1mol硫酸酯或亚硫酸乙烯酯会生成1mol理论二卤素磷酸酯类物质，将所得物质的质量除以理论所得物质质量，即为反应收率。
实施例2
首先对反应器进行干燥氮气吹扫，取108g(1mol)亚硫酸乙烯酯(CAS3741-38-6)加入到1L四口烧瓶内，控制反应器外部水浴30℃，随后加入300g乙腈溶剂进行溶解，四口烧瓶接冷凝管，冷凝温度为-30℃，外加机械搅拌，随后将209g(2.05mol)无水二氟磷酸(13779-41-4)加入500ml滴液漏斗内，四口烧瓶通氟氮混合气(F 2:N 2＝1:4)进行氟化。待体系温度达到30℃时，滴加二氟磷酸，反应过程严格控制温度在30℃以下，同时打开氟 氮混合气，进行通气，通气量为0.4L/min，外接二级防倒吸气体吸收装置。恒压滴液漏斗控制二氟磷酸2h内滴加完成，滴加完成后，静置2.5h，随后缓慢梯度升温(1h/10℃)，升至70℃，70℃反应2h后，抽滤，溶液进行氮气鼓泡，去除水分及残留氟气。转移进行减压精馏，将所得溶液放至1L圆底烧瓶内，利用5225分馏头外加1m具防爆环镀银双层玻璃弹簧精馏柱进行分馏(真空度30-100pa，回流比1:4)，其中前馏分为乙腈与二氟磷酸及其他杂质，取中段110-120℃馏分为顺式结构A 2，130-140℃馏分为反式结构A 2，具体红外图谱如图2所示。后馏分为硫酸乙烯酯分解产物及焦油。
顺式结构产物A 2的分子结构式为：
Figure PCTCN2022129225-appb-000008
其中R 2和R 3为：
Figure PCTCN2022129225-appb-000009
反式结构产物A 2的分子结构式为
Figure PCTCN2022129225-appb-000010
其中R 1和R 3为：
Figure PCTCN2022129225-appb-000011
由图2可以看出，在649.17cm -1处对应环内S＝0键的伸缩振动峰， 783.89cm -1，889.16cm -1处的吸收峰，对应亚硫酸酯环上的左右两个C-O键的伸缩振动峰，并受F元素影响，极性变化发生偏移。870.28cm -1处对应环状亚硫酸酯环键的伸缩振动峰，1120.83cm -1与1471.84cm -1对应底端两种C-F键的伸缩振动峰，1197.16cm -1与1364.15cm -1处的伸缩振动峰为P-F键的综合伸缩振动峰，1003.87cm -1处为一端反式P＝O键的伸缩振动峰，由于结构存在键间极性影响3067.99cm -1为另一端反式P＝O键的伸缩振动峰。
最终产物纯度顺式结构A 2为99.7％，反式结构A 2纯度为99.9％，顺反两种结构综合产率89.46％，其中顺式结构为39％，反式结构为61％。
实施例3
首先对反应器进行干燥氮气吹扫，取108g(1mol)亚硫酸乙烯酯(CAS3741-38-6)加入到1L四口烧瓶内，控制反应器外部水浴30℃，随后加入300g乙酸乙酯溶剂进行溶解，反应器内加入无水三氯化钌0.05g，四口烧瓶一侧通氯气进行氯化。打开氯气，进行通气，通气量为0.4L/min，外接二级防倒吸气体吸收装置。氯化5h后，鼓高纯氮气进行除氯0.5h，待溶液变为无色后，双氯代亚硫酸乙烯酯与乙酸乙酯混合液于四口烧瓶内备用。
四口烧瓶接冷凝管，外部水浴温度不变，加冷凝管，冷凝温度为-30℃，随后将209g(2.05mol)无水二氟磷酸(13779-41-4)加入500ml滴液漏斗内，待体系温度达到30℃时，滴加二氟磷酸，反应过程严格控制温度在30℃以下，同时恒压滴液漏斗控制二氟磷酸2h内滴加完成，滴加完成后，静置1.5h，随后缓慢梯度升温(1h/10℃)，升至70℃，70℃反应2.5h后，抽滤。滤液转移进行减压精馏，将所得溶液放至1L圆底烧瓶内，利用5225分馏头外加1m具防爆环镀银双层玻璃弹簧精馏柱进行分馏(真空度30-100pa，回流比1:4)，其中前馏分为乙酸乙酯与二氟磷酸及其他杂质，取中段75-84℃ 馏分为顺式结构A 2，90-101℃馏分为反式结构A 2。最终产物纯度顺式结构A 2纯度为99.1％，反式结构纯度为99.6％，顺反两种结构综合产率79.5％，其中顺式结构为37％，反式结构为63％。
顺式结构产物A 2的分子结构式为：
Figure PCTCN2022129225-appb-000012
其中R 2和R 3为：
Figure PCTCN2022129225-appb-000013
反式结构产物A 2的分子结构式为
Figure PCTCN2022129225-appb-000014
其中R 1和R 3为：
Figure PCTCN2022129225-appb-000015
性能测试
将实施例1～3制备得到的双取代二卤素磷酸酯作为添加剂，采用不同的添加量添加到电解液中，制备锂离子电池，具体方案如表1所示(其中方案19和方案20中的添加的A 2为实施例3制备得到，其他方案中的A 2均为采用实施例2制备得到的)，电解液中除表1中添加的成分外还包括六氟磷酸锂(浓度为为1mol/L)，有机溶剂(按照质量比为3:5:2配制的碳酸乙烯酯、碳酸二乙酯和碳酸二甲酯的混合液)。
该锂离子电池电解液的制备方法为：将碳酸乙烯酯、碳酸二乙酯和碳酸二甲酯混合均匀，然后加入六氟磷酸锂搅拌均匀，最后加入本实施例提供的双取代二卤素磷酸酯类添加剂和辅助添加剂。
对制备得到的锂离子电池的电池性能进行测试，具体测试结果如表2所示。具体测试方法如下：
(1)内阻
在室温下(25℃左右)，对锂离子电池以1C恒流充电至4.6V，恒压充电至截止电流为0.05C，采用交流内阻测试器测定锂离子电池的内阻。
(2)常温循环性能测试
在25℃下，对锂离子电池以1C恒流充电至4.6V，恒压充电至截止电流为0.05C，然后以1C恒流放电至3.0V，记为一个充放电循环，重复进行200次循环。25℃下，锂离子电池200次循环后的容量保持率的计算公式为：25℃循环200周的容量保持率＝(第200次循环的放电容量/首次放电容量)*100％。
(3)高温循环性能测试
在45℃下，对锂离子电池以1C恒流充电至4.6V，恒压充电至截止电流为0.05C，然后以1C恒流放电至3.0V，记为一个充放电循环，重复进行500次循环。45℃下，锂离子电池500次循环后的容量保持率的计算公式为：45℃循环500周的容量保持率＝(第500次循环的放电容量/首次放电容量)*100％。
(4)高温存储性能测试
S1：在25℃下对锂离子电池以1C恒流充电至4.6V，恒压充电至截止电流为0.05C，然后以1C恒流放电至3.0V，记为一个充放电循环，循环三次，以三次循环的平均容量为初始容量C 0，测试锂离子电池的体积，记为V 0；
S2：在25℃下对锂离子电池以1C恒流充电至4.6V，恒压充电至截止电 流为0.05C，然后放入60℃的高温测试柜中存储7天，取出后测试锂离子电池的体积，记为V n；
S3：在25℃下搁置5h后，对锂离子电池以1C恒流放电至3V，记录放电容量C 1，然后在25℃下对锂离子电池以1C恒流充电至4.6V，恒压充电至截止电流为0.05C，再以1C恒流放电至3V，记录恢复容量C 2；
锂离子电池的容量保持率、容量恢复率和体积膨胀率的计算公式如下：
容量保持率＝C 1/C 0*100％
容量恢复率＝C 2/C 0*100％
体积膨胀率＝(V n-V 0)/V 0*100％。
(5)低温性能测试
在25℃下，对锂离子电池以1C恒流充电至4.6V，恒压充电至截止电流为0.05C，以1C恒流放电至3.0V，记录放电容量；然后以1C恒流充电至4.6V，恒压充电至截止电流为0.05C，置于-20℃的环境中搁置24h，再以1C恒流放电至2.4V，记录放电容量。-20℃下，锂离子电池的低温放电效率的计算为：-20℃的低温放电效率＝(-20℃下1C放电容量/25℃下1C放电容量)*100％。
锂离子电池正极片和负极片的制备方法如下所示：
该锂离子电池中，正极片的制备方法为：按质量比为94.5:2:1.5:1.5混合镍钴锰酸锂(LiNi 0.5Co 0.2Mn 0.3)、小颗粒导电炭黑(Super-P)、碳纳米管(CNT)和聚偏氟乙烯(PVDF)，然后将混合物分散在N-甲基吡咯烷酮中，在真空搅拌机作用下搅拌至稳定均一，获得正极浆料；将正极浆料均匀涂覆于厚度为16μm的铝箔上，将涂有正极浆料的铝箔置于室温下晾干，随后转移至120℃的鼓风烘箱中干燥3h，经冷压、模切得到正极片。负极片的制备方法为：按 质量比94.5:2:1.5:2混合石墨、小颗粒导电炭黑(Super-P)、丁苯橡胶(SBR)和羧甲基纤维素(CMC)，然后将混合物分散在去离子水中，得到负极浆料；将负极浆料均匀涂覆于厚度为8μm的铜箔上，将涂有负极浆料的铜箔置于室温下晾干，随后转移至120℃的鼓风烘箱中干燥3h，经冷压、模切得到负极片。该锂离子电池的制作方法为：将制备好的正极片、负极片以及隔膜，通过叠片工序得到裸电芯；将裸电芯放入包装壳后，注入电解液后封口，经静置、热冷压、化成、分容工序，制作得到锂离子电池。
表1 锂离子电池电解液中各组分的添加量
Figure PCTCN2022129225-appb-000016
Figure PCTCN2022129225-appb-000017
表2 性能测试结果
Figure PCTCN2022129225-appb-000018
Figure PCTCN2022129225-appb-000019
通过测试结果可以看出，A 1与A 2类物质，可以对锂离子电池的性能起到提升作用。进一步的，采用反式A 1与反式A 2的结合可以进一步提高电池的高低温性能及降低内阻，这是因为反式结构较顺式结构的稳定性更好，形成的SEI膜会更加的稳固，且由于二氟磷酸根的沉积成膜特性，少量添加其内阻也不会因为膜的厚度提升，导致其内阻的进一步增大。而随着添加的量进一步增大，内阻会不断的提高，相应的性能会出现滑坡。方案22在二氟磷酸锂添加量大于2.5％时出现了浑浊现象，这种电解液是不能够应用于锂离子电池内部的，会造成不可控的安全影响。而添加剂A 1与A 2添加量可以大于2.5％的限制。因此本申请实施例的新型添加剂可以起到增强锂离子电池性能的作用，是一种良好的添加剂材料。同时我们也可以从结果看出利用氯代制作的二氟磷酸酯类添加剂，少量添加(约2％左右)，可以起到保护锂离子电池的作用，但是随着添加量的增加，锂离子电池的性能开始出现下降，原因是因为添加量过多，氯离子在高温下产生分解，变为游离氯，破坏电池正负极也与其他物质一起产生生成腐蚀性物质，造成电池的产气，因此会造成膨胀率高的问题。
以上所述仅是本申请的部分实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请原理的前提下，还可以做出若干改进和润 饰，这些改进和润饰也应视为本申请的保护范围。

Claims (10)

  1. 一种双取代二卤素磷酸酯类添加剂，其特征在于，所述添加剂的分子式如式A 1或A 2所示：
    Figure PCTCN2022129225-appb-100001
    其中，R 1与R 2其中的一个基团为结构式R所示，R 3与R 4其中的一个基团为结构式R所示，剩余两个基团相同选自H、卤素原子、C1～C5的烷烃基或卤代烷烃基。
  2. 权利要求1所述的双取代二卤素磷酸酯类添加剂的制备方法，其特征在于，包括如下步骤：
    1)将硫酸乙烯酯或亚硫酸乙烯酯与有机溶剂混合，加或不加催化剂，得到混合溶液；
    2)在混合溶液中通入含卤素气体进行卤化，待卤化完成后滴加二氟磷酸；
    3)待二氟磷酸滴加完成后，梯度升温至60～70℃，进行反应，得到双取代二卤素磷酸酯类添加剂。
  3. 根据权利要求2所述的制备方法，其特征在于，所述步骤2)中滴加二氟磷酸时，在滴加过程中利用冷凝管对二氟磷酸及反应液进行冷凝回流，冷凝管的温度控制在-20～-50℃。
  4. 根据权利要求2所述的制备方法，其特征在于，采用硫酸乙烯酯为原料时，通入的含卤素气体为氟氮混合气，添加催化剂三丁基氟化锡，在滴加二氟磷酸的过程中，混合溶液的温度控制在0～5℃，滴加完成后静置1.5～2.5h；
    或采用亚硫酸乙烯酯为原料，通入的含卤素气体为氟氮混合气时，不添加催化剂，在滴加二氟磷酸的过程中，混合溶液的温度控制在25～35℃，滴加完成后静置1.5～2.5h；
    或采用亚硫酸乙烯酯为原料，通入的含卤素气体为氯气时，添加催化剂三氯化钌，在滴加二氟磷酸的过程中，混合溶液的温度控制在25～35℃，滴加完成后静置1.5～2.5h。
  5. 根据权利要求2所述的制备方法，其特征在于，所述步骤3)中反应的时间为1.5～2.5h。
  6. 根据权利要求2所述的制备方法，其特征在于，所述步骤3)中反应结束后还包括除杂，所述除杂的方式为依次进行抽滤、氮气鼓泡和减压精馏； 所述减压精馏时的真空度为30～100pa，回流比为1:4。
  7. 一种根据权利要求1所述的双取代二卤素磷酸酯类添加剂或根据权利要求2～6任意一项方法制备得到双取代二卤素磷酸酯类添加剂在制备锂离子电解液中的应用。
  8. 根据权利要求7所述的应用，其特征在于，所述双取代二卤素磷酸酯类添加剂的添加量为电解液总质量的0.1％～7％。
  9. 根据权利要求7所述的应用，其特征在于，所述电解液中还包括锂盐、有机溶剂和辅助添加剂。
  10. 根据权利要求9所述的应用，其特征在于，所述辅助添加剂包括碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯、丁二腈、己二腈、己烷三腈、氟苯、硫酸亚乙烯酯、硫酸乙烯酯、三(三甲基硅基)硼酸酯、三(三甲基硅基)磷酸酯、二氟磷酸锂、四氟硼酸锂、双氟磺酰亚胺锂和双草酸硼酸锂中的一种或几种。
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