Electrolyte for improving high-temperature capacity fading and energy storage battery

Abstract

The invention belongs to the technical field of lithium ion batteries, and relates to an electrolyte for improving high-temperature capacity fading and an energy storage battery, the electrolyte comprises an electrolyte functional additive, a lithium salt and an organic solvent, the electrolyte functional additive comprises a sulfonate additive, fluoroethylene carbonate, vinylene carbonate, lithium bis (oxalato) borate and 1, 3-propene sultone, the functional additive of the electrolyte contains unsaturated bonds and is preferentially oxidized and polymerized under high voltage of a positive electrode to form a compact and uniform CEI film. The film can prevent an electrolyte from being in direct contact with a high-activity positive electrode, reduce dissolution of transition metal and avoid collapse (such as layered-rock salt phase transformation) of a material structure, the thickness of the film is relatively thin, and the thin surface film is beneficial to reduction of a diffusion energy barrier of lithium ions and reduction of initial impedance of the battery; on the premise of improving fast charging, the problems of low capacity retention rate and low capacity recovery rate under a high temperature condition in related technologies are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to an electrolyte for improving high-temperature capacity attenuation and an energy storage battery. BACKGROUND

[0002] With the technological innovation of new energy vehicles, wearable electronic devices and portable mobile terminals, the stability of lithium ion batteries under high temperature environment is increasingly demanding. This development trend is driving the industry to accelerate the breakthrough of high-temperature resistant battery technology research and development to ensure long-term reliable operation under extreme temperature conditions. In order to realize the stable operation of the battery system under high-temperature working conditions, the electrolyte system needs to be optimized in coordination with the thermal stability and electrochemical stability of the bulk material, while ensuring the compatibility of the electrode and electrolyte interface. At present, lithium ion batteries generally have low capacity retention rate under high temperature conditions, which seriously affects the cycle performance and service life of the battery.

[0003] In order to solve the above problems, the existing technology mainly focuses on the following three aspects: developing a new lithium salt structure system with high thermal stability, constructing a composite solvent system resistant to high-temperature oxidative decomposition, and developing a high-efficiency additive with an interface self-passivation function. Among them, the electrolyte functional additive is an important means to improve the compatibility of the electrolyte and the positive electrode interface, which can effectively protect the battery interface, reduce side reactions, and thus improve the high-temperature storage performance of the battery. However, the existing electrolyte functional additives still have some deficiencies in practical application, mainly in poor compatibility of the additive with the electrolyte, easy decomposition under high temperature conditions, etc., which makes it difficult to significantly improve the cycle performance and safety of the battery.

[0004] Therefore, it is urgent to develop a new type of electrolyte functional additive which not only has good compatibility with the electrolyte, but also remains stable under high temperature conditions and is not easy to decompose, and at the same time has excellent interface repair and self-passivation functions, which can effectively improve the low capacity retention rate and capacity recovery rate during the high-temperature storage process of the battery, thereby improving the comprehensive performance of the lithium ion battery. SUMMARY

[0005] In view of the problems in the prior art, the application provides an electrolyte for improving high-temperature capacity attenuation and an energy storage battery, which solves the problem of low capacity retention rate and capacity recovery rate under high-temperature conditions in the related art under the premise of improving fast charging.

[0006] The application is realized by the following technical scheme:

[0007] An electrolyte for improving high-temperature capacity attenuation, comprising an electrolyte functional additive, a lithium salt and an organic solvent.

[0008] The electrolyte functional additive includes sulfonate additive, fluoroethylene carbonate, vinylene carbonate, lithium difluoro(oxalato)borate and 1,3-propene sultone.

[0009] Preferably, the total amount of the electrolyte functional additive and lithium salt is 4wt%-7wt% of the total amount of electrolyte, and the rest is organic solvent.

[0010] Preferably, the mass ratio of the sulfonate additive, fluoroethylene carbonate, vinylene carbonate, lithium difluoro(oxalato)borate and 1,3-propene sultone is 0.5wt%-1wt%:1wt%-3wt%:0.2wt%-0.5wt%:0.5wt%-0.8wt%:0.5wt%-1wt%.

[0011] Preferably, the organic solvent includes methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate; according to the total volume of the organic solvent being 100%, dimethyl carbonate accounts for 50%-70%, ethylene carbonate accounts for 15%-25%, and methyl ethyl carbonate accounts for 15%-25%.

[0012] Preferably, the structure general formula of the sulfonate functional additive is:

[0013]

[0014] R1 is selected from any one of substituted or unsubstituted phenyl, substituted or unsubstituted alkoxy, and substituted or unsubstituted alkyl with 1-5 carbon atoms; R2 is selected from any one of fluorophenyl, halogenated alkyl with 1-5 carbon atoms, substituted or unsubstituted alkoxy, substituted or unsubstituted silicon group, and substituted or unsubstituted alkenyl with 1-5 carbon atoms.

[0015] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0016] Preferably, the concentration of the lithium salt in the electrolyte is 1.0-1.3mol / L.

[0017] A preparation method of an electrolyte for improving high-temperature capacity attenuation, including, under an argon atmosphere, adding sulfonate functional additive, fluoroethylene carbonate, lithium difluoro(oxalato)borate, vinylene carbonate, 1,3-propene sultone and lithium salt into an organic solvent, stirring and mixing at 10℃ to obtain the electrolyte.

[0018] An energy storage battery based on the electrolyte for improving high-temperature capacity attenuation, prepared based on the electrolyte for improving high-temperature capacity attenuation, and assembled into an energy storage battery by using the electrolyte for improving high-temperature capacity attenuation, positive electrode sheet, negative electrode sheet and separator.

[0019] Preferably, the preparation process of the negative electrode plate is: taking graphite as the negative electrode active material, preparing the negative electrode slurry by taking graphite, conductive agent acetylene black, binder CMC (sodium carboxymethyl cellulose) and SBR (styrene-butadiene rubber) in a mass ratio of 95.4:1.5:1.4:1.7, coating the negative electrode slurry on the copper foil current collector, vacuum drying, and obtaining the negative electrode plate.

[0020] The preparation process of the positive electrode plate is: taking NCM811 (lithium nickel cobalt manganese oxide) as the positive electrode active material, preparing the positive electrode slurry by taking the positive electrode active material, conductive agent acetylene black and binder PVDF (polyvinylidene fluoride) in a mass ratio of 95.5:2.2:2.3, coating the positive electrode slurry on the aluminum foil current collector, vacuum drying, and obtaining the positive electrode plate.

[0021] Compared with the prior art, the present application has the following beneficial technical effects:

[0022] The present application provides a kind of electrolyte functional additive combination and its application lithium ion battery, which contains unsaturated bond, preferentially oxidizes polymerization under high voltage of positive electrode, and forms dense and uniform CEI film.The film can prevent the electrolyte from directly contacting with the high-activity positive electrode, reduce the dissolution of transition metals (Ni, Co, Mn), avoid the collapse of material structure (such as layered→rock salt phase transition), and the thickness of the film is relatively thin, the thin surface film is beneficial to reduce the diffusion energy barrier of lithium ions, reduce the initial impedance of battery;The generated CEI film blocks the erosion of HF to the positive electrode particles, inhibits the generation of cracks in the particles, thereby improving the high temperature stability;It can also form an AI-O-SO2-passivation layer on the surface of aluminum foil, block the corrosion of LiFSi to aluminum, and improve the comprehensive performance of lithium ion battery.A kind of electrolyte functional additive is provided, additive A reduces the initial impedance by forming a film on the positive electrode, inhibits the dissolution of transition metal ions, improves the high temperature storage capacity retention rate and recovery rate.Electrolyte functional additive improves the compatibility of electrolyte and positive electrode interface, effectively improves the low capacity retention rate and capacity recovery rate of battery during high temperature storage from two aspects of protecting battery interface and reducing side reaction, DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] The application provides a kind of electrolyte functional additive combination and its application lithium ion battery, electrolyte functional additive A contains unsaturated bond, preferentially oxidized polymerization under high voltage of positive electrode, form dense uniform electrochemical interface CEI film.The film can prevent electrolyte and high active positive electrode direct contact, reduce transition metal (Ni, Co, Mn) dissolution, avoid material structure collapse (such as layered→rock salt phase transition), and the thickness of the film is thin, thin surface film is beneficial to reduce the diffusion energy barrier of lithium ion, reduce the initial impedance of battery;The generated CEI film blocks HF to the erosion of positive electrode particles, inhibits the generation of crack in particle, thereby improving high temperature stability;Also can form AI-O-SO2-passivation layer on the surface of aluminum foil, block LiFSi to the corrosion of aluminum, improve the comprehensive performance of lithium ion battery.

[0025] The main purpose of the present application is to provide an electrolyte functional additive, electrolyte and lithium ion battery, which improves the fast charging and solves the problem of low capacity retention rate and capacity recovery rate under high temperature in the related art.

[0026] In order to achieve the above-mentioned purpose, a sulfonate additive is provided, and the general formula of the sulfonate additive is formula I:

[0027]

[0028] R1 is selected from any one of substituted or unsubstituted phenyl, substituted or unsubstituted alkoxy, and substituted or unsubstituted alkyl with 1-5 carbon atoms.

[0029] R2 is selected from any one of fluorophenyl, halogenated alkyl with 1-5 carbon atoms, substituted or unsubstituted alkoxy, substituted or unsubstituted silicon group, and substituted or unsubstituted alkenyl with 1-5 carbon atoms.

[0030] In a second aspect, the application provides an electrolyte, which comprises an organic solvent, a lithium salt and an electrolyte functional additive A.

[0031] The electrolyte functional additive A comprises the sulfonate additive as described in the first aspect, and the addition amount is (0.5-1%), fluoroethylene carbonate (1-3%), vinylene carbonate (0.2-0.5%), lithium difluoro(oxalato)borate (0.5-0.8%), 1,3-propylene sulfite (0.5-1%), and the total mass percentage of all the additives in the electrolyte is 4-7%, and the rest is an organic solvent.

[0032] The organic solvent comprises methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate. The organic solvent comprises the following components in terms of volume percentage, based on the total volume of 100% of the organic solvent: dimethyl carbonate 50%-70%, ethylene carbonate 15%-20%, and methyl ethyl carbonate 15%-20%.

[0033] The lithium salt includes at least one of lithium hexafluorophosphate and lithium bisfluorosulfonylimide.

[0034] The concentration of the lithium salt in the electrolyte is 1.0-1.3 mol / L.

[0035] The present application provides a kind of energy storage battery, adopts graphite as negative active material, graphite, conductive agent acetylene black, binder CMC, SBR are prepared into negative electrode slurry according to the mass percentage of 95.4:1.5:1.4:1.7, negative electrode slurry is coated on copper foil current collector, vacuum drying, and negative electrode pole piece is prepared;

[0036] NCM811 is used as positive active material, and the positive active material, conductive agent acetylene black, binder PVDF are prepared into positive electrode slurry according to the mass ratio of 95.5:2.2:2.3, the positive electrode slurry is coated on aluminum foil current collector, vacuum drying, and positive electrode pole piece is prepared;The electrolyte prepared in the example and the comparative example is assembled into 21700 battery with the above-mentioned positive electrode pole piece, negative electrode pole piece and separator.

[0037] Example 1

[0038] The present embodiment provides an electrolyte functional additive, the electrolyte functional additive is a compound (5-hexene-1-p-toluenesulfonate) shown as formula I-1, fluoroethylene carbonate, vinylene carbonate, lithium bisfluorosulfonyl oxalate, 1,3-propylene sulfone lactone.

[0039]

[0040] The electrolyte is composed of organic solvent, lithium hexafluorophosphate and the above-mentioned electrolyte functional additive.

[0041] The organic solvent includes the following components in volume percentage, taking the total volume of organic solvent as 100%.

[0042] Dimethyl carbonate 65%, vinyl carbonate 20% and methyl ethyl carbonate 15%.

[0043] The mass percentage of the functional additive (5-hexene-1-p-toluenesulfonate) of formula I-1 is 0.5%, the mass percentage of the fluoroethylene carbonate is 1%, the mass percentage of the vinylene carbonate is 0.3%, the mass percentage of the lithium bisfluorosulfonyl oxalate is 0.5%, and the mass percentage of the 1,3-propylene sulfone lactone is 0.5%, taking the total mass of electrolyte as 100%.

[0044] The concentration of lithium hexafluorophosphate in the electrolyte is 1.0 mol / L.

[0045] The electrolyte is prepared by the following method:

[0046] Under an argon atmosphere, a compound represented by formula I-1 (5-hexene-1-p-toluenesulfonate), fluoroethylene carbonate, lithium difluoro(oxalato)borate, vinylene carbonate, 1,3-propene sultone, and lithium bisfluorosulfonylimide are added to an organic solvent formed by mixing methyl ethyl carbonate, ethylene carbonate, and dimethyl carbonate, and stirred at a temperature of 10°C to obtain the electrolyte.

[0047] Example 2

[0048] The present example provides an electrolyte functional additive and an electrolyte, which is different from Example 1 in that an electrolyte functional additive (formula I-2) (polyethylene glycol monomethyl ether methanesulfonate) is added to the electrolyte in an amount of 0.5%,

[0049]

[0050] The electrolyte is composed of an organic solvent, lithium bisfluorosulfonylimide, and the above-mentioned electrolyte functional additive.

[0051] The organic solvent includes the following components in percentage by volume, based on 100% of the total volume of the organic solvent:

[0052] Dimethyl carbonate 50%, ethylene carbonate 25%, and methyl ethyl carbonate 25%.

[0053] The mass percentage of the polyethylene glycol monomethyl ether methanesulfonate is 0.5%, the mass percentage of the fluoroethylene carbonate is 1%, the mass percentage of the vinylene carbonate is 0.3%, the mass percentage of the lithium difluoro(oxalato)borate is 0.5%, and the mass percentage of the 1,3-propene sultone is 0.5%, based on 100% of the total mass of the electrolyte.

[0054] The concentration of lithium hexafluorophosphate and lithium bisfluorosulfonylimide in the electrolyte is 1.1 mol / L.

[0055] The electrolyte is prepared by the following method:

[0056] Under an argon atmosphere, a compound represented by formula I-1 (5-hexene-1-p-toluenesulfonate), fluoroethylene carbonate, lithium difluoro(oxalato)borate, vinylene carbonate, 1,3-propene sultone, and lithium bisfluorosulfonylimide are added to an organic solvent formed by mixing methyl ethyl carbonate, ethylene carbonate, and dimethyl carbonate, and stirred at a temperature of 10°C to obtain the electrolyte.

[0057] Example 3

[0058] The embodiment provides an electrolyte functional additive and an electrolyte, which are different from those in the embodiment 1 in that the structure of the functional additive is shown as formula I-3 (3-fluoropropanol p-toluenesulfonate), and the adding amount is 0.8%, and the embodiment 1 is not limited in this aspect.

[0059]

[0060] The electrolyte is composed of an organic solvent, lithium difluorooxalate borate and the electrolyte functional additive.

[0061] The organic solvent includes the following components in percentage by volume, taking the total volume of the organic solvent as 100%:

[0062] Dimethyl carbonate 70%, ethylene carbonate 15% and methyl ethyl carbonate 15%.

[0063] The mass percentage of the 3-fluoropropanol p-toluenesulfonate is 0.5%, the mass percentage of the fluoroethylene carbonate is 1%, the mass percentage of the vinylene carbonate is 0.2%, the mass percentage of the lithium difluorooxalate borate is 0.5%, and the mass percentage of the 1,3-propene sultone is 0.5%, taking the total mass of the electrolyte as 100%.

[0064] The concentration of lithium hexafluorophosphate in the electrolyte is 1.0 mol / L.

[0065] The electrolyte is prepared by the following method:

[0066] Under an argon atmosphere, 3-fluoropropanol p-toluenesulfonate, fluoroethylene carbonate, lithium difluorooxalate borate, vinylene carbonate, 1,3-propene sultone and lithium hexafluorophosphate are added into an organic solvent formed by mixing methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate, and then the mixture is stirred at 10 DEG C to obtain the electrolyte.

[0067] Embodiment 4

[0068] The embodiment provides an electrolyte functional additive and an electrolyte, which are different from those in the embodiment 1 in that the structure of the functional additive A is shown as formula I-4 (trimethylsilyl trifluoromethanesulfonate).

[0069]

[0070] The electrolyte is composed of an organic solvent, lithium hexafluorophosphate and the electrolyte functional additive.

[0071] The organic solvent includes the following components in percentage by volume, taking the total volume of the organic solvent as 100%:

[0072] Dimethyl carbonate 65%, ethylene carbonate 15% and methyl ethyl carbonate 20%.

[0073] The mass percentage of the trimethylsilyl triflate is 1.0%, the mass percentage of the fluoroethylene carbonate is 1%, the mass percentage of the vinylene carbonate is 0.2%, the mass percentage of the lithium difluoro(oxalato)borate is 0.5%, and the mass percentage of the 1,3-propene sultone is 0.5%, based on the total mass of the electrolyte being 100%.

[0074] The concentration of lithium hexafluorophosphate in the electrolyte is 1.3 mol / L.

[0075] The electrolyte is prepared by the following method:

[0076] Under an argon atmosphere, trimethylsilyl triflate, fluoroethylene carbonate, lithium difluoro(oxalato)borate, vinylene carbonate, 1,3-propene sultone, and lithium hexafluorophosphate are added to an organic solvent formed by mixing methyl ethyl carbonate, ethylene carbonate, and dimethyl carbonate, and the mixture is stirred at 10°C to obtain the electrolyte.

[0077] Example 5

[0078] This example provides an electrolyte functional additive and an electrolyte, which differ from those of Example 1 only in that the functional additive A is shown as formula I-5 (trimethylsilyl phenyl sulfonate).

[0079]

[0080] The electrolyte is composed of an organic solvent, lithium hexafluorophosphate, and the above-mentioned electrolyte functional additive.

[0081] The organic solvent includes the following components by volume percentage, based on the total volume of the organic solvent being 100%:

[0082] The organic solvent includes the following components by volume percentage, based on the total volume of the organic solvent being 100%:

[0083] The mass percentage of the trimethylsilyl phenyl sulfonate is 0.5%, the mass percentage of the fluoroethylene carbonate is 1%, the mass percentage of the vinylene carbonate is 0.2%, the mass percentage of the lithium difluoro(oxalato)borate is 0.5%, and the mass percentage of the 1,3-propene sultone is 0.5%, based on the total mass of the electrolyte being 100%.

[0084] The concentration of lithium hexafluorophosphate in the electrolyte is 1.3 mol / L.

[0085] The electrolyte is prepared by the following method:

[0086] The electrolyte is prepared by mixing the organic solvent, lithium hexafluorophosphate and the electrolyte functional additive under argon atmosphere at a temperature of 10°C.

[0087] Example 6

[0088] The electrolyte functional additive and electrolyte of the present example are the same as those of Example 1 except that the functional additive A is 4-fluorophenyl triflate as shown in Formula I-6.

[0089]

[0090] The electrolyte is prepared by mixing the organic solvent, lithium hexafluorophosphate and the electrolyte functional additive under argon atmosphere at a temperature of 10°C.

[0091] The organic solvent comprises the following components in percentage by volume, based on the total volume of the organic solvent as 100%:

[0092] The organic solvent comprises dimethyl carbonate 60%, ethylene carbonate 20% and methyl ethyl carbonate 20%.

[0093] The mass percentage of 4-fluorophenyl triflate is 0.6%, the mass percentage of fluoroethylene carbonate is 1%, the mass percentage of vinylene carbonate is 0.2%, the mass percentage of lithium difluoro(oxalato)borate is 0.5% and the mass percentage of 1,3-propene sultone is 0.5%, based on the total mass of the electrolyte as 100%.

[0094] The concentration of lithium hexafluorophosphate and lithium difluorosulfonylimide in the electrolyte is 1.0 mol / L.

[0095] The electrolyte is prepared by mixing the organic solvent, lithium hexafluorophosphate and the electrolyte functional additive under argon atmosphere at a temperature of 10°C.

[0096] The electrolyte is prepared by mixing the organic solvent, lithium hexafluorophosphate and the electrolyte functional additive under argon atmosphere at a temperature of 10°C.

[0097] Example 7

[0098] The electrolyte functional additive and electrolyte of the present example are the same as those of Example 1 except that the amount of fluoroethylene carbonate in Example 1 is adjusted to 2%.

[0099] Example 8

[0100] This example provides an electrolyte additive and electrolyte, which is different from example 1 only in that the amount of fluoroethylene carbonate added in the example is adjusted to 3%, and the others are the same as example 1.

[0101] Example 9

[0102] This example provides an electrolyte additive and electrolyte, which is different from example 1 only in that the amount of fluoroethylene carbonate added in the example is adjusted to 3%, and the others are the same as example 1.

[0103] Example 10

[0104] This example provides an electrolyte additive and electrolyte, which is different from example 1 only in that the amount of fluoroethylene carbonate added in the example is adjusted to 3%, and the others are the same as example 1.

[0105] Example 11

[0106] This example provides an electrolyte additive and electrolyte, which is different from example 1 only in that the amount of fluoroethylene carbonate added in the example is adjusted to 3%, and the others are the same as example 1.

[0107] Example 12

[0108] This example provides an electrolyte additive and electrolyte, which is different from example 1 only in that the amount of fluoroethylene carbonate added in the example is adjusted to 3%, and the others are the same as example 1.

[0109] Example 13

[0110] This example provides an electrolyte additive and electrolyte, which is different from example 1 only in that the amount of fluoroethylene carbonate added in the example is adjusted to 3%, and the others are the same as example 1.

[0111] Comparative Example 1

[0112] This comparative example provides an electrolyte, which is different from example 1 only in that the electrolyte functional additive A is not contained in comparative example 1, and the others are the same as example 1.

[0113] Test data of comparative example 1 and examples 1-6 as shown in table 1

[0114]

[0115]

[0116] Analysis: Example 1 contains an alkenyl group, which undergoes radical polymerization at the positive electrode at high voltage, forming a cross-linked polymer CEI film that blocks the positive electrode from contacting the electrolyte and inhibits the dissolution of transition metal ions;

[0117] Example 2 contains an ether group, which facilitates lithium ion desolvation and reduces the formation energy barrier of the SEI film, and the reduction product CH3SO2Li of the sulfonate group enhances the toughness of the SEI;

[0118] Example 3 contains F atoms, which form Ni-F bonds with Ni 3+ in the positive electrode, inhibiting interfacial side reactions; the propanol segment improves electrolyte wettability and reduces the Li+ concentration gradient at the interface;

[0119] Example 4 contains a silicon group, which efficiently removes H2O and HF, blocking acid-catalyzed chain reactions, and the triflate group decomposes to form LiF / Li2SO4, constructing a high-ionic-conductivity CEI;

[0120] Example 5 contains a benzene ring conjugated system, which inhibits further oxidation of the solvent, and the decomposition product SiO2 of the silane group is used to fill the pores of the CEI film, improving its density;

[0121] Example 6 contains a fluorinated aromatic ring that undergoes ring-opening / polymerization at high voltage, forming a conductive CEI containing C-F bonds and LiF, and the triflate group provides self-repairing ability, dynamically repairing CEI cracks.

[0122] Example 7 and Example 8 increase the content of fluorinated ethylene carbonate compared to Example 1, and tests show that it has little effect on high-temperature storage performance.

[0123] Example 9 increases the content of vinylene carbonate compared to Example 1, and the initial DCR increases, possibly because the inorganic component in the vinylene carbonate film-forming component is more rigid and the DCR increases slightly.

[0124] Examples 10, 11, 12, and 13 adjust the amount of lithium salt additive and 1,3-propylene sulfite additive, and the high-temperature storage performance is not much different from that of Example 1. The functional additive A still plays a role in the system. Therefore, the additive A improves the high-temperature performance of the ternary battery, such as

[0125] Table 2 shows the data table of the sulfonate additives in Examples 1-6;

[0126] melting point boiling point density formula i-1 78℃ 122℃ 1.117 g / cm 3 ]] formula i-2 58℃ 259℃ 1.20 g / cm 3 ]] formula i-3 34℃ 160℃ 1.0 g / cm 3 ]] formula i-4 25℃ 140℃ 1.3 g / cm 3 ]] formula i-5 9℃ 261℃ 1.1 g / cm 3 ]]> formula i-6 65℃ 267.95℃ 1.6 g / cm 3 ]]

[0127] The application provides a kind of energy storage battery, adopt graphite as negative active material, graphite, conductive agent acetylene black, binder CMC, SBR are prepared into negative electrode slurry according to the mass percentage of 95.4:1.5:1.4:1.7, negative electrode slurry is coated on copper foil current collector, vacuum drying, and negative electrode sheet is prepared;NCM811 is used as positive active material, positive active material, conductive agent acetylene black, binder PVDF are prepared into positive electrode slurry according to the mass ratio of 95.5:2.2:2.3, positive electrode slurry is coated on aluminum foil current collector, vacuum drying, and positive electrode sheet is prepared;The electrolyte prepared by the examples and comparative examples is assembled into 21700 battery with the above-mentioned positive electrode sheet, negative electrode sheet and separator.

[0128] The application adds an electrolyte functional additive containing an unsaturated bond in the electrolyte, promotes preferential oxidation polymerization of the electrolyte functional additive under high pressure of the positive electrode, forms a dense and uniform CEI film, and effectively improves the compatibility of the electrolyte and the positive electrode interface.

[0129] The electrolyte functional additive of the application forms a CEI film with a relatively small thickness on the surface of the positive electrode, reduces the diffusion energy barrier of lithium ions, thereby reducing the initial impedance of the battery, and is beneficial to improving the charge-discharge efficiency of the battery.

[0130] The CEI film generated by the electrolyte functional additive of the application can effectively block the corrosion of HF on the positive electrode particles, inhibit the generation of cracks in the particles, and significantly improve the high-temperature stability and cycle life of the battery.

[0131] The electrolyte functional additive of the application can form an AI-O-SO2-passivation layer on the surface of the aluminum foil, effectively block the corrosion of LiFSi on aluminum, improve the comprehensive performance of the lithium ion battery, and prolong the service life of the battery.

[0132] The electrolyte functional additive of the application has good thermal stability through the optimized molecular structure design, is not easy to decompose within the use temperature range of the electrolyte, and significantly improves the high-temperature storage capacity retention rate and capacity recovery rate of the battery.

[0133] In the application, all the embodiments and preferred implementation methods mentioned in the present application can be combined to form new technical solutions if not otherwise specified.

[0134] In the application, all the technical features and preferred features mentioned in the present application can be combined to form new technical solutions if not otherwise specified.

[0135] In the present application, unless otherwise specified, percentage (%) or part refers to the percentage by weight or weight parts of the composition.

[0136] In the present application, unless otherwise specified, each component or its preferred components involved can be combined with each other to form a new technical solution.

[0137] In the present application, unless otherwise specified, the numerical range "a~b" represents a shorthand notation for any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "6~22" represents that all real numbers between "6~22" have been listed herein, and "6~22" is only a shorthand notation for these numerical combinations.

[0138] The lower limit and upper limit of the "range" disclosed in the present application can be one or more lower limits and one or more upper limits, respectively.

[0139] In the present application, the term "and / or" used herein refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0140] In the present application, unless otherwise specified, each reaction or operation step can be carried out sequentially or according to the sequence. Preferably, the reaction method herein is carried out sequentially.

[0141] Unless otherwise specified, the professional and scientific terms used herein have the same meaning as understood by those skilled in the art. In addition, any method or material similar or equivalent to that described can also be applied in the present application.

[0142] It should be understood that when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or collections thereof.

[0143] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0144] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form; any person skilled in the art can easily implement the present application according to the description and the above description; however, any person skilled in the art can make some changes, modifications and equivalent changes within the scope of the technical solutions of the present application, and the equivalent embodiments of the present application are still within the protection scope of the technical solutions of the present application.

Claims

1. An electrolyte solution for improving high-temperature capacity fade, characterized by, The electrolyte functional additive, the lithium salt and the organic solvent are included. The electrolyte functional additive includes sulfonate additives, fluoroethylene carbonate, vinylene carbonate, lithium difluoro (oxalato) borate and 1,3-propylene sulfite.

2. The electrolyte solution for improving high-temperature capacity fade according to claim 1, wherein The sum of the added amounts of the electrolyte functional additive and the lithium salt accounts for 4wt%-7wt% of the total amount of the electrolyte, and the rest is the organic solvent.

3. The electrolyte solution for improving high-temperature capacity fade according to claim 1, wherein The mass ratio among the sulfonate additives, fluoroethylene carbonate, vinylene carbonate, lithium difluoro (oxalato) borate and 1,3-propylene sulfite is 0.5wt%-1wt%:1wt%-3wt%:0.2wt%-0.5wt%:0.5wt%-0.8wt%:0.5wt%-1wt%.

4. The electrolyte solution for improving high-temperature capacity fade according to claim 1, wherein The organic solvent includes methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate; according to the total volume of the organic solvent being 100%, dimethyl carbonate accounts for 50%-70%, ethylene carbonate accounts for 15%-25% and methyl ethyl carbonate accounts for 15%-25%.

5. The electrolyte solution for improving high-temperature capacity fade according to claim 1, wherein The structural general formula of the sulfonate functional additive is: R1 is selected from any one of substituted or unsubstituted phenyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkyl with 1-5 carbon atoms; R2 is selected from any one of fluorophenyl, halogenated alkyl with 1-5 carbon atoms, substituted or unsubstituted alkoxy, substituted or unsubstituted silicon base, substituted or unsubstituted alkenyl with 1-5 carbon atoms.

6. The electrolyte solution for improving high-temperature capacity fade according to claim 1, wherein The lithium salt includes at least one of lithium hexafluorophosphate and lithium bisfluorosulfonylimide.

7. The electrolyte solution for improving high-temperature capacity fade according to claim 1, wherein The concentration of the lithium salt in the electrolyte is 1.0-1.3mol / L.

8. The method of claim 1, wherein the electrolyte solution is prepared by adding the additive to the electrolyte solution. The electrolyte is obtained by adding the sulfonate functional additive, fluoroethylene carbonate, lithium difluoro (oxalato) borate, vinylene carbonate, 1,3-propylene sulfite and the lithium salt into the organic solvent under stirring at 10℃ under an argon atmosphere.

9. An energy storage battery based on an electrolyte for improving high-temperature capacity fade, prepared based on the electrolyte for improving high-temperature capacity fade according to any one of claims 1-7, characterized in that, The electrolyte for improving high-temperature capacity attenuation is used to assemble an energy storage battery together with a positive electrode sheet, a negative electrode sheet and a separator.

10. The energy storage battery based on the electrolyte for improving high-temperature capacity attenuation according to claim 9, wherein, The preparation process of the negative electrode sheet is as follows: graphite is used as the negative electrode active material, graphite, conductive agent acetylene black, binder CMC and SBR are prepared into negative electrode slurry at a mass ratio of 95.4:1.5:1.4:1.7, the negative electrode slurry is coated on a copper foil current collector, vacuum drying is performed, and the negative electrode sheet is prepared; The preparation process of the positive electrode sheet is as follows: NCM811 is used as the positive electrode active material, the positive electrode active material, conductive agent acetylene black and binder PVDF are prepared into positive electrode slurry at a mass ratio of 95.5:2.2:2.3, the positive electrode slurry is coated on an aluminum foil current collector, vacuum drying is performed, and the positive electrode sheet is prepared.

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