CN116544507A - Electrolyte and secondary battery - Google Patents

Electrolyte and secondary battery Download PDF

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Publication number
CN116544507A
CN116544507A CN202310515348.3A CN202310515348A CN116544507A CN 116544507 A CN116544507 A CN 116544507A CN 202310515348 A CN202310515348 A CN 202310515348A CN 116544507 A CN116544507 A CN 116544507A
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Prior art keywords
electrolyte
organic solvent
formula
compound
carbonate
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蔡涛涛
乔飞燕
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Sunwoda Electric Vehicle Battery Co Ltd
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Sunwoda Electric Vehicle Battery Co Ltd
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Priority to CN202310515348.3A priority Critical patent/CN116544507A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—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
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses electrolyte and a secondary battery, and belongs to the technical field of batteries. The electrolyte comprises a first organic solvent and a compound with a structure shown in a formula (I), wherein R1-R10 are respectively and independently selected from hydrogen atoms, halogen, nitryl, aldehyde groups, cyano groups, sulfonyl groups, anhydride groups, substituted or unsubstituted C1-C3 alkyl groups and substituted or unsubstituted C1-C3 alkoxy groups; the first organic solvent includes a halogenated cyclic carbonate. The electrolyte contains the halogenated cyclic carbonate and the compound with the structure shown in the formula (I), and through the synergistic effect of the halogenated cyclic carbonate and the compound, the electrolyte side reaction decomposition is effectively inhibited, and the stability of an electrode/electrolyte interface is improved, so that the cycle stability and the rate capability of the battery are improved, and the gas production problem is also improved to a certain extent.

Description

Electrolyte and secondary battery
Technical Field
The invention relates to the technical field of batteries, in particular to electrolyte and a secondary battery.
Background
The system consisting of the high-nickel ternary positive electrode and the silicon-based negative electrode is one of the most promising high-specific-energy lithium ion batteries. However, the interface stability of the high-nickel ternary positive electrode is reduced along with the increase of the nickel content, side reactions continuously occur in the electrochemical circulation process, the capacity is quickly attenuated, and the safety problems such as gas production, thermal runaway and the like are accompanied, so that the large-scale application process of the high-nickel ternary positive electrode material is hindered.
The volume expansion rate of the conventional graphite cathode can be controlled within 10%, however, the volume expansion rate of the silicon cathode can be up to more than 300%, which puts higher demands on the mechanical strength of the interface passivation layer. If the interface stability problem of the silicon-based negative electrode is not properly solved, the particles are broken due to the severe volume expansion/contraction during the lithium intercalation/deintercalation process. The constantly exposed fresh electrode/electrolyte interface continuously forms an SEI, consumes electrolyte and the amount of active lithium in the system, manifesting as reduced coulombic efficiency (especially the first week), and reduced full cell cycle life.
Electrolyte composition has a significant impact on interface stability. In particular, it has been reported in the prior art that electrolyte additives can build passivation layers (including SEI and CEI) at the electrode/electrolyte interface, thereby enhancing interface stability, inhibiting side reactions of electrolyte and active materials, and further improving electrochemical performance and battery safety. Compared with the optimization schemes such as positive and negative electrode coating, doping, morphology engineering and the like, the electrolyte additive regulation interface is simple and convenient to operate, has controllable cost and does not sacrifice energy density.
However, the electrolyte additives reported in the prior art still have limited improvement of electrochemical performance of a battery system consisting of a high-nickel ternary positive electrode and a silicon-based negative electrode.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an electrolyte and a secondary battery, wherein the electrolyte contains halogenated cyclic carbonate and a compound with a structure shown in a formula (I), and the halogenated cyclic carbonate and the compound effectively inhibit the decomposition of electrolyte side reaction through synergistic effect, and improve the stability of an electrode/electrolyte interface, so that the cycle stability and the rate capability of the battery are improved, and the gas production problem is improved to a certain extent.
In order to achieve the above object, in a first aspect of the present invention, there is provided an electrolyte comprising a first organic solvent and a compound having a structure represented by formula (I),
in the formula (I), R1-R10 are independently selected from hydrogen atom, halogen, nitro, aldehyde group, cyano, sulfonyl, anhydride group, substituted or unsubstituted C1-C3 alkyl and substituted or unsubstituted C1-C3 alkoxy;
the first organic solvent includes a halogenated cyclic carbonate.
As a preferred embodiment of the present invention, the halogenated cyclic carbonate includes at least one of halogenated ethylene carbonate, halogenated propylene carbonate, halogenated butylene carbonate.
As a preferred embodiment of the present invention, the halogen element in the halogenated cyclic carbonate is at least one of F, cl.
As a preferred embodiment of the present invention, the halogenated cyclic carbonate includes at least one of fluoroethylene carbonate, difluoroethylene carbonate, 3-trifluoropropylene carbonate.
As a preferred embodiment of the present invention, the compound having the structure represented by formula (I) includes at least one of the compounds A1 to a 18:
as a preferred embodiment of the present invention, the mass ratio of the first organic solvent to the compound having the structure represented by formula (I) is (5 to 60): 1.
as a preferred embodiment of the present invention, the electrolyte further comprises the following components: a lithium salt, a second organic solvent; the second organic solvent is a chain ester and/or a cyclic ester.
As a preferred embodiment of the present invention, the electrolyte comprises the following components in mass percent: 10-20% of lithium salt, 5-40% of first organic solvent, 40-84% of second organic solvent and 0.1-5% of compound with a structure shown in formula (I).
In a second aspect of the present invention, there is provided a secondary battery comprising a positive electrode, a negative electrode, and the electrolyte.
As a preferred embodiment of the present invention, the positive electrode is a positive electrode sheet including a positive electrode active material having a chemical formula including Li a Ni x Co y Mn z M e O 2 Wherein e is more than or equal to 0 and less than or equal to 0.1,0.9, a is more than or equal to 1.1,0.33, x is more than or equal to 0.96,0.01, y is more than or equal to 0.33,0.01, z is more than or equal to 0.33, and x+y+z=1, m comprises at least one of Al, zr, sr, ti, B, mg, sn, W, Y, ba, nb, mo, ta, si, la, er, nd, gd, ce.
As a preferred embodiment of the present invention, the negative electrode is a negative electrode tab including a negative electrode active material including a carbon-silicon composite material.
The invention has the beneficial effects that:
the invention develops an electrolyte and a secondary battery, wherein the electrolyte contains halogenated cyclic carbonate and a compound with a structure shown in a formula (I), and the halogenated cyclic carbonate and the compound have synergistic effect, so that the side reaction decomposition of the electrolyte is effectively inhibited, the stability of an electrode/electrolyte interface is improved, the cycle stability and the multiplying power performance of the battery are improved, and the gas production problem is improved to a certain extent.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the invention, the technical characteristics described in an open mode comprise a closed technical scheme composed of the listed characteristics and also comprise an open technical scheme comprising the listed characteristics.
In the present invention, the numerical ranges are referred to as continuous, and include the minimum and maximum values of the ranges, and each value between the minimum and maximum values, unless otherwise specified. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range description features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
In the present invention, the specific dispersing and stirring treatment method is not particularly limited.
The reagents or apparatus used in the present invention are conventional products commercially available without the manufacturer's knowledge.
The embodiment of the invention provides an electrolyte, which comprises a first organic solvent and a compound with a structure shown as a formula (I),
in the formula (I), R1-R10 are independently selected from hydrogen atom, halogen, nitro, aldehyde group, cyano, sulfonyl, anhydride group, substituted or unsubstituted C1-C3 alkyl and substituted or unsubstituted C1-C3 alkoxy;
the first organic solvent includes a halogenated cyclic carbonate. The electrolyte contains halogenated cyclic carbonate and a compound with a structure shown in a formula (I) (the compound is called as the formula (I)) which are synergistic, so that the side reaction decomposition of the electrolyte is effectively inhibited, the stability of an electrode/electrolyte interface is improved, the cycle stability and the multiplying power performance of a battery are improved, and the gas production problem is improved to a certain extent.
The compound with the structure shown in the formula (I) takes diphenyl sulfone as a main structure, and the benzene ring contains substituent groups. The inventor researches find that the compound of the formula (I) has good film forming performance and can form an interface passivation layer on the surface of the anode and the cathode in preference to the solvent.
The halogenated cyclic carbonate is adopted as the first organic solvent, and the halogenated cyclic carbonate and the compound shown in the formula (I) are synergistic, so that the electrolyte side reaction decomposition is inhibited, and the electrode/electrolyte interface stability is improved. (the LUMO energy level of halogenated carbonate is generally lower than that of conventional unsubstituted carbonate solvent under the induction action of halogenated element, the halogenated carbonate is reduced and decomposed to form film at the interface of negative electrode in the discharge process, the formed SEI is thin and uniform, the inorganic content in SEI component is relatively high, but in the circulation process, the volume expansion of silicon negative electrode can make fresh electrolyte interface continuously exposed, the halogenated carbonate is consumed quickly, after the halogenated carbonate is consumed, the battery is faced with "water jump" risk, so that for this problem, the further addition of compound of formula (I) into electrolyte can increase the organic component content of SEI component, and can increase the elastic modulus of SEI, increase the mechanical property of interface layer, further inhibit the volume expansion of silicon-based negative electrode and slow down the consumption rate of halogenated cyclic carbonate, and under the cooperation of both, the electrode/electrolyte interface stability and correspondent cycle life can be effectively raised, and the safety risks of interface side reaction and gas production are inhibited, in addition, the compound of formula (I) can introduce Li into SEI 2 SO 4 、RSO 2 And ROSO (r-o-n-o-n 2 Li and other components, which can improve Li + The transmission efficiency in the interface is beneficial to the dynamic performance of the battery. )
The halogenated cyclic carbonate and the compound with the structure shown in the formula (I) are combined to improve the interface stability, reduce the side reaction of the electrolyte interface and relieve the gas production phenomenon of the battery.
In one embodiment, the halogenated cyclic carbonate comprises at least one of halogenated ethylene carbonate, halogenated propylene carbonate, halogenated butylene carbonate.
The halogenated ethylene carbonate, the halogenated propylene carbonate and the halogenated butylene carbonate all have a cyclic structure and are good solvents in the electrolyte, so that the effects of improving interface stability and inhibiting side reactions of the electrolyte can be achieved by cooperating with the compound shown in the formula (I).
In one embodiment, the halogen element in the halogenated cyclic carbonate is at least one of F, cl. The halogen in the electrolyte additive is typically F and/or Cl.
In one embodiment, the halogenated cyclic carbonate includes at least one of fluoroethylene carbonate (FEC), bis-fluoroethylene carbonate (DFEC), 3-trifluoropropylene carbonate (TFPC).
The inventor researches find that fluoroethylene carbonate, difluoroethylene carbonate and 3, 3-trifluoro propylene carbonate are used as a first organic solvent, the synergistic effect with the compound of the formula (I) is better, and the secondary battery containing the electrolyte has better interface stability and relatively better cycle stability and rate capability.
In one embodiment, at least one of R1 to R10 is selected from halogen, nitro, aldehyde, cyano, sulfonyl, anhydride, substituted or unsubstituted C1 to C3 alkyl, substituted or unsubstituted C1 to C3 alkoxy.
In one embodiment, the compound having the structure of formula (I) includes at least one of the compounds A1 to a 18:
in one embodiment, the compound having the structure shown in formula (I) includes at least one of A1, A2, A4, A9, a15, a16, a17, a 18.
The different substituents on the benzene ring of the compound of formula (I) have respectively different effects: sulfur-containing products of film-forming processes (Li 2 SO 4 、RSO 2 And ROSO (r-o-n-o-n 2 Li, etc.) has good stability, li + The conduction capacity is strong, and the interface impedance can be reduced; the sulfonate substituent and the nitro substituent on the benzene ring can be respectively converted into sulfur-containing and nitrogen-containing compounds, compared with oxygen-containing analogues, the two compounds have better ionic conductivity, and the interface ion conductivity can be improved; methoxy, aldehyde, cyano and anhydride groups on the benzene ring can polymerize into chains, enhancing interface dullnessChemical layer mechanical strength; the cyano substituent can coordinate with the metal ion on the surface of the positive electrode to improve the stability of the positive electrode interface and inhibit the dissolution of the transition metal ion. For the compound shown in the formula (I) in which R1-R10 are all hydrogen atoms, the compound has the characteristic of strong affinity with a silicon-based negative electrode, the film forming texture is more uniform, and the relatively smaller molecular weight can endow the compound with larger content controllability.
In one embodiment, the mass ratio of the first organic solvent to the compound having the structure represented by formula (I) is (5 to 60): 1.
the first organic solvent and the compound with the structure shown in the formula (I) have obviously better synergistic effect within the specific mass ratio range, the prepared electrolyte has better interface stability, and the electrochemical performance of the battery is relatively better. When the mass of the first organic solvent is relatively more and the mass of the compound having the structure shown in the formula (I) is relatively less, a firm interface passivation layer may not be formed, and trace water in the electrolyte is difficult to be effectively absorbed, so that the action effect of the compound is affected; when the mass of the first organic solvent is relatively smaller and the mass of the compound having the structure represented by formula (I) is relatively larger, the interface passivation layer formed may be caused to be too thick, thereby making Li + Diffusion resistance is excessive and increases polarization.
In one embodiment, the mass ratio of the first organic solvent to the compound having the structure represented by formula (I) is (10 to 40): 1.
in one embodiment, the electrolyte further comprises the following components: a lithium salt, a second organic solvent; the second organic solvent is a chain ester and/or a cyclic ester.
The lithium salt is a conventional component in the electrolyte, and the kind of lithium salt conventional in the art may be selected.
In one embodiment, the lithium salt comprises a first lithium salt and a second lithium salt;
the first lithium salt comprises lithium hexafluorophosphate (LiPF) 6 )；
The second lithium salt comprises lithium tetrafluoroborate (LiBF 4 ) Lithium bisoxalato borate (LiBOB), lithium difluorooxalato borate (LiDFOB), difluoroLithium bis (fluorosulfonyl) imide (LiFePO), lithium bis (fluorosulfonyl) imide (LiLiFeSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium perchlorate (LiClO) 4 ) Lithium difluorophosphate (LiDFPO) 2 ) At least one of lithium pentafluoroethyl trifluoroborate (LiDAB), lithium 2-trifluoromethyl-4, 5-dicyanoimidazole (LiTDI), lithium bis (2-fluoromalonate) borate (LiBFMB), lithium dimethyl catecholborate (LiCBB), lithium 4-pyridyltrimethylborate (LPTB), lithium 2-fluorophenol trimethylborate (LFPTB).
The lithium hexafluorophosphate has moderate ion migration number, moderate dissociation constant, good oxidation resistance and good aluminum foil passivation capability in a common nonaqueous organic solvent, can be matched with various anode and cathode materials, and is the most main lithium salt in a lithium ion battery. The second lithium salt is used as an auxiliary lithium salt and plays a role in improving the stability of the electrolyte and the migration number of lithium ions after being compounded with lithium hexafluorophosphate.
In one embodiment, the mass ratio of the first lithium salt to the second lithium salt is 1: (0.1-0.5).
When the mass ratio of the first lithium salt to the second lithium salt is within the above range, the electrolyte has good conductivity and proper viscosity.
In one embodiment, the chain ester includes at least one of dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), methylpropyl carbonate (MPC), diphenyl carbonate (DPhC), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB).
In one embodiment, the cyclic ester comprises at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), gamma-butyrolactone (gamma-GBL).
In one embodiment, the electrolyte comprises the following components in percentage by mass: 10-20% of lithium salt, 5-40% of first organic solvent, 40-84% of second organic solvent and 0.1-5% of compound with a structure shown in formula (I).
When the mass percentages of the components in the electrolyte are within the ranges, the first organic solvent and the compound with the structure shown in the formula (I) have remarkable effect of improving the performance of the electrolyte, and the electrolyte is suitable in viscosity, high in conductivity and excellent in electrochemical performance.
The method for preparing the electrolyte is not particularly limited in the present invention, and one skilled in the art may prepare the electrolyte according to a conventional method.
For example, the preparation method of the electrolyte of the invention comprises the following steps:
mixing a first organic solvent and a second organic solvent, and removing water to obtain a first mixed solution;
adding lithium salt into the first mixed solution to obtain a second mixed solution;
and adding a compound with a structure shown in a formula (I) into the second mixed solution to obtain the electrolyte.
An embodiment of the present invention provides a secondary battery including a positive electrode, a negative electrode, and the electrolyte.
For the present invention, the positive electrode and the negative electrode in the secondary battery can be made of conventional materials in the conventional art; the preparation method of the secondary battery may be a preparation method conventional in the art.
In one embodiment, the positive electrode is a positive electrode sheet comprising a positive electrode active material having a chemical formula comprising Li a Ni x Co y Mn z M e O 2 Wherein e is more than or equal to 0 and less than or equal to 0.1,0.9, a is more than or equal to 1.1,0.33, x is more than or equal to 0.96,0.01, y is more than or equal to 0.33,0.01, z is more than or equal to 0.33, and x+y+z=1, m comprises at least one of Al, zr, sr, ti, B, mg, sn, W, Y, ba, nb, mo, ta, si, la, er, nd, gd, ce.
In one embodiment, the negative electrode is a negative electrode tab comprising a negative electrode active material comprising a carbon-silicon composite.
In one embodiment, the secondary battery has a normal temperature DCR of less than 34.5mΩ, and does not include 34.5mΩ.
The invention is further illustrated by the following specific examples:
example 1
The embodiment provides an electrolyte and a secondary battery, and the preparation method thereof is as follows:
(1) Preparation of electrolyte
At room temperature, in a glove box filled with argon (H 2 O<1ppm,O 2 <1 ppm) uniformly mixing a first organic solvent and a second organic solvent, and removing water to obtain a first mixed solution;
then adding lithium salt into the first mixed solution, continuously stirring and cooling to obtain a second mixed solution;
adding a compound with a structure shown in a formula (I) into the second mixed solution, and uniformly stirring to obtain the electrolyte;
the addition amounts of the respective components in the electrolytic solution are shown in table 1, wherein the sum of the component masses of the first organic solvent, the second organic solvent, the lithium salt and the compound having the structure shown in formula (I) is 100%.
(2) Preparation of positive electrode plate
Positive electrode active material Li (Ni 0.9 Mn 0.05 Co 0.05 )O 2 (NMC 90), conductive agent acetylene black (Super P) and binder polyvinylidene fluoride (PVDF) are uniformly mixed according to the mass ratio NMC90:super P: PVDF=90:7:3, and uniformly dispersed in 1-methyl-2-pyrrolidone (NMP) to prepare uniform black slurry, and the prepared slurry is coated on two sides of an aluminum foil, baked, rolled and cut into pieces to obtain the positive plate.
(3) Preparation of negative electrode plate
The negative electrode active material components of silicon oxide (SiO), artificial Graphite (AG), conductive agent acetylene black (SuperP) and binder SBR are uniformly mixed according to the mass ratio of SiO: AG: superP: SBR=11:83:3:3, uniformly dispersed in deionized water to prepare uniform black slurry, and the prepared slurry is coated on two sides of a copper foil, baked, rolled and cut into pieces to obtain a negative electrode plate.
(4) Manufacturing of battery
And stacking the prepared positive plate, the diaphragm and the negative plate in sequence, enabling the diaphragm to be positioned between the positive plate and the negative plate, winding, hot-pressing and shaping, welding the electrode lugs to obtain a bare cell, placing the bare cell in an outer packaging aluminum-plastic film, placing in an oven with the temperature of 85+/-10 ℃ for baking for 24 hours, injecting the prepared electrolyte into the dried battery, standing, forming and capacity-dividing to prepare the lithium ion soft package battery.
Remaining examples and comparative examples
In the remaining examples and comparative examples, an electrolyte and a secondary battery were provided, respectively, and the preparation was performed by referring to the method of example 1, with only a part of the variables (see table 1 for details in particular) being changed, and the other variables in table 1 were the same as those in example 1.
TABLE 1
Battery performance test
The performance test was performed on the soft pack batteries prepared in the above examples and comparative examples, and the specific method is as follows:
(1) Normal temperature DCR test: at 25±2 ℃, the soft pack battery 1C was charged to 4.25V, then discharged for 30 minutes at 1C capacity, and after being adjusted to 50% soc, the 5C constant current pulse discharge was performed for 10s and then charged for 10s, to calculate dcr= (voltage before pulse discharge-voltage after pulse discharge)/discharge current×100%. After storage at 60 ℃ for 30 days, when the battery was completely cooled to 25±2 ℃, DCR was again tested, and the internal resistance change rate = (DCR after 30 days-DCR before 30 days)/DCR before 30 days was 100%, and the obtained recording results are shown in table 2.
(2) And (3) testing normal temperature cycle performance: and (3) at 25+/-2 ℃, carrying out charge-discharge cycle test on the soft package battery within the range of 2.8-4.25V at the charge-discharge multiplying power of 1C/1C, and recording the first-week discharge specific capacity and the discharge specific capacity after 1000-week cycle of the battery. Capacity retention for 1000 weeks = specific discharge capacity for 1000 weeks/specific discharge capacity for first week x 100%, recorded data are shown in table 2.
(3) High temperature storage performance: and (3) placing the soft package battery at 60+/-2 ℃, carrying out charge and discharge test at a charge and discharge multiplying power of 1C/1C within a range of 2.8-4.25V, recording the first week discharge specific capacity of the battery, storing for 30 days at 60+/-2 ℃, carrying out charge and discharge test again, and recording the discharge specific capacity. High-temperature storage capacity retention = specific discharge capacity after 30 days/specific discharge capacity at first week x 100%, and the recorded data are shown in table 2.
(4) High temperature gas production test: and (3) charging the soft-packed battery to 4.25V at the constant current of 1C multiplying power at the temperature of 25+/-2 ℃ and then charging the soft-packed battery to the constant voltage of 4.25V until the current is lower than 0.05C, so that the soft-packed battery is in a 4.25V full charge state. Testing the volume of the fully charged battery before storage and marking as V0; the fully charged battery was then placed in an oven at 70±2 ℃, and after two days the battery was removed, immediately tested for its stored volume and recorded as V1. The volume expansion ratio= (V1-V0)/v0×100% and the obtained results are shown in table 2.
TABLE 2
As is apparent from the comparison of examples 1 to 25 and comparative examples 1 to 3, when the structural formula shown in formula (I) is contained in the electrolyte additive, the first organic solvent contains the halogenated cyclic carbonate, decomposition of the electrolyte by side reaction is effectively suppressed by the synergistic effect of the compound of the structure shown in formula (I) and the halogenated cyclic carbonate, and the electrode/electrolyte interface stability is improved, so that the cycle stability and rate performance of the battery are improved, and the problem of gas generation is also improved to some extent.
As is clear from the comparison of examples 8 to 16, when the mass ratio of the compound having the structure shown in formula (I), the first organic solvent, and the first organic solvent to the compound having the structure shown in formula (I) is within the scope of the present invention, it is advantageous to coordinate the actions of each constituent substance in the electrolyte, promoting the superior performance of the battery.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims (11)

1. An electrolyte solution, characterized by comprising a first organic solvent and a compound having a structure represented by formula (I),
in the formula (I), R1-R10 are independently selected from hydrogen atom, halogen, nitro, aldehyde group, cyano, sulfonyl, anhydride group, substituted or unsubstituted C1-C3 alkyl and substituted or unsubstituted C1-C3 alkoxy;
the first organic solvent includes a halogenated cyclic carbonate.
2. The electrolyte of claim 1 wherein the halogenated cyclic carbonate comprises at least one of halogenated ethylene carbonate, halogenated propylene carbonate, halogenated butylene carbonate.
3. The electrolyte of claim 1, wherein the halogen element in the halogenated cyclic carbonate is at least one of F, cl.
4. The electrolyte of claim 3 wherein the halogenated cyclic carbonate comprises at least one of fluoroethylene carbonate, bis-fluoroethylene carbonate, 3-trifluoropropylene carbonate.
5. The electrolyte according to claim 1, wherein the compound having the structure represented by formula (I) includes at least one of compounds A1 to a 18:
6. the electrolyte according to claim 1, wherein the mass ratio of the first organic solvent to the compound having the structure represented by formula (I) is (5 to 60): 1.
7. the electrolyte of claim 1, further comprising the following components: a lithium salt, a second organic solvent; the second organic solvent is a chain ester and/or a cyclic ester.
8. The electrolyte according to claim 7, comprising the following components in percentage by mass: 10-20% of lithium salt, 5-40% of first organic solvent, 40-84% of second organic solvent and 0.1-5% of compound with a structure shown in formula (I).
9. A secondary battery comprising a positive electrode, a negative electrode, and the electrolyte of any one of claims 1 to 8.
10. The secondary battery according to claim 9, wherein the positive electrode is a positive electrode sheet including a positive electrode active material having a chemical formula including Li a Ni x Co y Mn z M e O 2 Wherein e is more than or equal to 0 and less than or equal to 0.1,09.ltoreq.a 1.1,0.33.ltoreq.x 0.96,0.01.ltoreq.y 0.33,0.01.ltoreq.z.ltoreq.0.33, and x+y+z=1, M comprising at least one of Al, zr, sr, ti, B, mg, sn, W, Y, ba, nb, mo, ta, si, la, er, nd, gd, ce.
11. The secondary battery of claim 9, wherein the negative electrode is a negative electrode tab comprising a negative electrode active material comprising a carbon-silicon composite.
CN202310515348.3A 2023-05-08 2023-05-08 Electrolyte and secondary battery Pending CN116544507A (en)

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