Electrolyte additive, electrolyte, and lithium ion secondary battery comprising the same

Abstract

The present application provides electrolyte additives, electrolytes, and lithium ion secondary batteries comprising the same. The electrolyte additive comprises a substance represented by the following formula (1), wherein R1 is perfluorinated propylene or perfluorinated butylene; and R2 and R3 are each independently a five-membered single heterocyclic group or a six-membered single heterocyclic group containing one heteroatom selected from O, S, or N. With the electrolyte additive of the present application, the electrolyte comprising the same, and the lithium ion secondary battery comprising the same, the gassing expansion of the lithium ion secondary battery is inhibited, the first coulombic efficiency of the lithium ion secondary battery is improved, the cycle performance of the lithium ion secondary battery is improved, and the post-cycle resistance of the lithium ion secondary battery is reduced.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion secondary batteries, and more specifically, to electrolyte additives, electrolytes containing the electrolyte additives, and lithium-ion secondary batteries containing the electrolytes. Background Technology

[0002] In recent years, with the continuous development of electronic technology, the demand for battery devices to support the energy supply of electronic devices has been increasing. Currently, there is a need for batteries capable of storing more electricity and outputting higher power. Traditional lead-acid and nickel-metal hydride batteries can no longer meet the needs of new electronic products such as mobile devices like smartphones and stationary devices such as energy storage systems. Therefore, lithium-ion batteries have attracted widespread attention. In the development of lithium-ion batteries, their capacity and performance have been significantly improved.

[0003] The electrolyte is the carrier of ion transport in a lithium-ion battery, generally composed of organic solvents, functional additives, and lithium salts. During charging and discharging, the electrolyte decomposes, forming a passivation layer on the electrode surface—an electronically insulating but lithium-ion-conducting solid electrolyte interphase (SEI) film. Lithium ions can freely intercalate and deintercalate through this passivation layer. Simultaneously, this passivation layer is solvent-repellent, allowing it to exist stably in solvents, preventing solvent molecules from passing through and effectively preventing damage to the electrode material from solvent molecule co-intercalation. Therefore, the formation of the SEI film is crucial to the performance of lithium-ion batteries. A stable, uniformly thick SEI film with good lithium-ion conductivity can significantly improve the reversible capacity and extend the lifespan of a lithium-ion battery. The SEI film formed through electrochemical reactions has strict requirements on the reaction potential, and the introduction of functional additives, especially film-forming additives, is generally considered an effective method to improve battery performance. On the one hand, functional additives can participate in the formation of the SEI film; on the other hand, functional additives can provide a lower reaction potential, allowing them to preferentially undergo electrochemical reactions before the solvent, effectively inhibiting solvent decomposition. The addition of certain functional additives can even protect the main functional additives, forming an SEI film that has undergone multiple stages of reaction.

[0004] In existing technologies, the most commonly used functional additives in lithium-ion secondary batteries are vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Because FEC, after the introduction of fluorine, has a low least unoccupied molecular orbital (LUMO) energy and is easily reduced, it is generally considered a relatively ideal negative electrode film-forming additive. Simultaneously, fluorine, due to its small atomic radius, can improve the solubility of the additive and the wettability between the electrode and the separator, thereby improving the battery's temperature resistance. However, FEC is essentially still a carbonate compound, and its decomposition during reaction inevitably produces gas, causing battery expansion and thus degrading battery performance, especially when FEC is used extensively. Therefore, solving the problem of gas generation by carbonate additives such as FEC leading to expansion and performance degradation in lithium-ion secondary batteries is particularly important. Summary of the Invention

[0005] The main objective of this invention is to provide an electrolyte additive, an electrolyte containing the electrolyte additive, and a lithium-ion secondary battery containing the electrolyte, so as to solve the problem that the gas generation of carbonate additives such as FEC in the prior art leads to the expansion and performance degradation of lithium-ion secondary batteries.

[0006] To achieve the above objectives, according to one aspect of the present invention, an electrolyte additive is provided, the electrolyte additive comprising a substance represented by the following formula (1):

[0007]

[0008] Wherein, R1 is perfluoropropylene or perfluorobutylene, i.e. It is perfluoro-1,2-cyclopentenidyl or perfluoro-1,2-cyclohexenidyl; and R2 and R3 are each independently a five-membered monoheterocyclic group or a six-membered monoheterocyclic group containing a heteroatom selected from O, S or N.

[0009] Furthermore, in the above-mentioned electrolyte additive, R1 is perfluoropropylene, i.e. It is perfluoro-1,2-cyclopentenidyl.

[0010] Furthermore, in the above-mentioned electrolyte additives, R2 and R3 are each independently selected from any one of furanyl, thiophenyl, pyrroleyl, pyranyl, thiophenyl, pyridyl, dihydrofuranyl, tetrahydrofuranyl, dihydrothiophenyl, tetrahydrothiophenyl, dihydropyrroleyl, tetrahydropyrroleyl, dihydropyranyl, tetrahydropyranyl, hexahydropyranyl (piperanyl), dihydrothiophenyl, tetrahydrothiophenyl, hexahydrothiophenyl, dihydropyridyl, tetrahydropyridyl or hexahydropyridyl (piperanyl).

[0011] More preferably, in the above-mentioned electrolyte additives, R2 and R3 are each independently selected from any one of furanyl, thiophenyl, pyrroleyl, pyranyl, thiophenyl, pyridyl, tetrahydrofuranyl, tetrahydrothiophenyl, tetrahydropyrroleyl, tetrahydropyranyl, tetrahydrothiophenyl, or hexahydropyridyl.

[0012] Furthermore, in the above-mentioned electrolyte additives, R1 is perfluoropropylene, and R2 and R3 are each independently selected from furanyl, thiophene, or pyrroleyl.

[0013] Furthermore, in the above-mentioned electrolyte additive, the electrolyte additive comprises any one of the following substances:

[0014]

[0015] According to another aspect of the invention, an electrolyte is provided comprising an organic solvent, a lithium salt, and the electrolyte additives described above.

[0016] Furthermore, in the above electrolyte, the amount of electrolyte additive is in the range of 0.10 parts by weight to 3.00 parts by weight, based on 100 parts by weight of organic solvent and lithium salt.

[0017] Furthermore, in the above electrolyte, the amount of electrolyte additive is in the range of 0.50 parts by weight to 2.00 parts by weight, based on 100 parts by weight of organic solvent and lithium salt.

[0018] Furthermore, in the above electrolyte, the organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, butyl carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dihexyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and propyl propionate.

[0019] According to another aspect of the present invention, a lithium-ion secondary battery is provided, comprising: a positive electrode, a negative electrode, a separator, and an electrolyte as described above.

[0020] The electrolyte additive of the present invention, the electrolyte containing the electrolyte additive, and the lithium-ion secondary battery containing the electrolyte suppress gas production expansion of the lithium-ion secondary battery, improve the initial coulombic efficiency of the lithium-ion secondary battery, improve the cycle performance of the lithium-ion secondary battery, and reduce the post-cycle impedance of the lithium-ion secondary battery. Attached Figure Description

[0021] Figure 1 Film formation characteristic curves of the negative electrode for Examples 2, 7 and Comparative Example 1 are shown.

[0022] Figure 2 Cycle performance graphs of lithium-ion batteries from Examples 2, 7, and Comparative Example 1 are shown.

[0023] Figure 3 The post-cycle impedance spectra of the lithium-ion batteries in Examples 2, 7 and Comparative Example 1 are shown. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the various embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments. The following embodiments are merely exemplary and are not intended to limit the scope of protection of the present invention.

[0025] As explained in the background section, fluoroethylene carbonate (FEC) and similar additives are commonly used as negative electrode film-forming additives in existing lithium-ion secondary batteries. However, the use of carbonate additives such as FEC can lead to gas generation, causing expansion and performance degradation of the lithium-ion secondary battery. To address the problems in the prior art, a typical embodiment of the present invention provides an electrolyte additive comprising a substance represented by the following formula (1):

[0026]

[0027] Wherein, R1 is perfluoropropylene or perfluorobutylene, i.e. It is perfluoro-1,2-cyclopentenidyl or perfluoro-1,2-cyclohexenidyl; and

[0028] R2 and R3 are each independently a five-membered or six-membered monoheterocyclic group containing a heteroatom selected from O, S, or N.

[0029] This invention designs a perfluorinated cyclic alkene compound as an electrolyte additive. This perfluorinated cyclic alkene compound uses fluorine atoms to replace oxygen atoms and carbonyl groups in existing additives. When this additive decomposes, it mainly releases fluoride ions, replacing carbon-based groups such as CO and / or CO2 with fluoride ions, thus avoiding gas production.

[0030] The electrolyte additive of this invention can replace or significantly reduce the amount of carbonate additives such as FEC used in existing technologies, thereby suppressing gas expansion in lithium-ion secondary batteries. Simultaneously, by changing the substituent functional groups at the alkenyl position, the reaction potential of the electrolyte additive can be effectively controlled, thereby regulating the decomposition potential of other functional additives or solvents. This is beneficial for the protection mechanism of the additives and solvents. It can effectively suppress gas expansion in lithium-ion secondary batteries and improve their safety characteristics.

[0031] The introduction of a perfluorinated framework structure into the electrolyte additive of this invention can effectively improve the wettability and temperature characteristics of the electrolyte. Furthermore, the alteration of the substituent functional groups at the alkenyl position of the electrolyte additive can trigger a multi-stage decomposition reaction, resulting in a synergistic effect. Considering factors such as the reaction potential of the additive structure, its compatibility with the solvent, and the reaction characteristics at the negative electrode, the electrolyte additive of this invention can use cyclic heterocyclic structures as substituents. Utilizing their electron-donating properties, these structures stabilize the fluorine atoms at the allyl positions of the perfluorinated cyclic alkenes, preventing excessive SEI film growth and resulting in an overly thick film during reaction decomposition. Simultaneously, the cyclic heterocyclic structure possesses relatively good charge and reaction characteristics, which is beneficial for modifying the SEI film composition and can also inhibit electrolyte decomposition at the negative electrode, thereby protecting the negative electrode.

[0032] The electrolyte additive of this invention preferentially forms an SEI film on the negative electrode surface compared to solvents such as ethylene carbonate (EC) in the electrolyte. Simultaneously, it effectively inhibits the decomposition of solvents such as EC in the electrolyte, effectively suppressing gas production and expansion in lithium-ion secondary batteries, and improving the discharge capacity and initial efficiency during the first charge-discharge process. Furthermore, the electrolyte additive of this invention introduces heterocyclic structures as substituents, particularly utilizing the favorable charge characteristics of heterocyclic structures. Specifically, five-membered or six-membered single-membered heterocyclic rings have a higher charge density than benzene rings, achieving strong electron-donating characteristics. This stabilizes the fluorine atoms at the allyl positions on the cyclic framework structure, inhibiting excessively vigorous decomposition reactions that could lead to an excessively thick SEI film, thereby reducing the resistance of the lithium-ion secondary battery and improving its cycle performance. The heterocyclic structure in the electrolyte additive of this invention inhibits the decomposition of solvents in the electrolyte on the negative electrode surface, protecting the negative electrode and thus improving the cycle and high-temperature characteristics of the lithium-ion secondary battery.

[0033] The main structure of the electrolyte additive of the present invention is a perfluorinated cyclic alkene structure with heterocyclic substituents, and the introduced heterocyclic substituents themselves have electrochemical reaction characteristics. By forming the structure shown in formula (1), a high-performance SEI film can be formed on the electrode surface to protect the electrode and improve the performance of lithium-ion secondary batteries.

[0034] The electrolyte additive of this invention has a low reaction potential and can preferentially form a film on the electrode surface before the solvent in the electrolyte, forming a dense protective layer and inhibiting the decomposition of the solvent in the electrolyte. By using the electrolyte additive of this invention, gas production and expansion of lithium-ion secondary batteries can be suppressed, while the initial coulombic efficiency of lithium-ion secondary batteries can be improved, the cycle performance of lithium-ion secondary batteries can be improved, and the post-cycle impedance of lithium-ion secondary batteries can be reduced.

[0035] In some embodiments of the present invention, in formula (1), R1 is perfluoropropylidene, i.e. R1 is a perfluoro-1,2-cyclopentenyldiyl. In some other embodiments of the present invention, R1 in formula (1) is a perfluorobutylene, i.e. It is perfluorinated-1,2-cyclohexenediyl.

[0036] In some embodiments of the present invention, in formula (1), R2 and R3 are each independently selected from any one of furanyl, thiophenyl, pyrroleyl, pyranyl, thiophenyl, pyridyl, dihydrofuranyl, tetrahydrofuranyl, dihydrothiophenyl, tetrahydrothiophenyl, dihydropyrroleyl, tetrahydropyrroleyl, dihydropyranyl, tetrahydropyranyl, hexahydropyranyl (piperanyl), dihydrothiophenyl, tetrahydrothiophenyl, hexahydrothiophenyl, dihydropyridyl, tetrahydropyridyl or hexahydropyridyl (piperanyl).

[0037] In a preferred embodiment of the present invention, in formula (1), R2 and R3 are each independently selected from any one of furanyl, thiophenyl, pyrroleyl, pyranyl, thiophenyl, pyridyl, tetrahydrofuranyl, tetrahydrothiophenyl, tetrahydropyrroleyl, tetrahydropyranyl, tetrahydrothiophenyl or hexahydropyridyl.

[0038] In some embodiments of the present invention, in formula (1), R1 is perfluoropropylidene, i.e. It is a perfluorinated-1,2-cyclopentenyldiyl group, and R2 and R3 are each independently selected from furanyl, thiophene, or pyrroleyl groups. When R2 and R3 are each independently selected from the above groups, the reaction potential of the electrolyte additive can be reduced more effectively, stronger electron-donating characteristics can be provided, the fluorine atom at the allyl position on the cyclic framework structure can be stabilized, the SEI film composition can be improved, the electrolyte decomposition on the negative electrode surface can be inhibited to protect the negative electrode, the resistance of the lithium-ion secondary battery can be further reduced, the initial coulombic efficiency of the lithium-ion secondary battery can be further improved, and the cycle performance of the lithium-ion secondary battery can be further improved.

[0039] In some embodiments of the present invention, in order to further improve the initial coulombic efficiency of the lithium-ion secondary battery, further improve the cycle performance of the lithium-ion secondary battery, and further reduce the post-cycle impedance of the lithium-ion secondary battery, the electrolyte additive comprises any one of the following substances:

[0040]

[0041]

[0042] In one embodiment of the present invention, an exemplary perfluorinated cyclic alkene with heterocyclic substituents, taking 1,2-di(3-furanyl)-perfluorinated-1,2-cyclopentene as an example, gains 4 electrons during the first charge and discharge to generate the following product, which can participate in the formation of the SEI film on the negative electrode surface.

[0043]

[0044] In another typical embodiment of the present invention, an electrolyte is provided, comprising an organic solvent, a lithium salt, and the electrolyte additives described above. Due to the inclusion of the electrolyte additives of the present invention, the electrolyte of the present invention can effectively form a stable SEI film on the surface of the negative electrode during the first charge-discharge process of the battery, suppressing the decomposition of the solvent in the electrolyte. Furthermore, the electrolyte of the present invention suppresses gas expansion in the lithium-ion secondary battery, improves the initial coulombic efficiency of the lithium-ion secondary battery, improves the cycle performance of the lithium-ion secondary battery, and reduces the post-cycle impedance of the lithium-ion secondary battery.

[0045] In some embodiments of the present invention, in the electrolyte of the present invention, based on 100 parts by weight of organic solvent and lithium salt, the amount of electrolyte additive is in the range of 0.10 parts by weight to 3.00 parts by weight, preferably in the range of 0.15 parts by weight to 2.80 parts by weight, more preferably in the range of 0.20 parts by weight to 2.60 parts by weight, further preferably in the range of 0.25 parts by weight to 2.40 parts by weight, further preferably in the range of 0.30 parts by weight to 2.20 parts by weight, further preferably in the range of 0.35 parts by weight to 2.00 parts by weight, further preferably in the range of 0.40 parts by weight to 2.00 parts by weight, and further preferably in the range of 0.45 parts by weight to 2.00 parts by weight. By controlling the amount of electrolyte additive within the above range, the initial coulombic efficiency of the lithium-ion secondary battery can be improved, the cycle performance of the lithium-ion secondary battery can be improved, and the post-cycle impedance of the lithium-ion secondary battery can be reduced.

[0046] In some embodiments of the present invention, in the electrolyte of the present invention, based on 100 parts by weight of organic solvent and lithium salt, the amount of electrolyte additive is in the range of 0.50 parts by weight to 2.00 parts by weight, preferably in the range of 0.50 parts by weight to 1.50 parts by weight, more preferably in the range of 0.50 parts by weight to 1.30 parts by weight, further preferably in the range of 0.70 parts by weight to 1.10 parts by weight, and most preferably in the range of 0.90 parts by weight to 1.10 parts by weight. By controlling the amount of electrolyte additive within the above range, the initial coulombic efficiency of the lithium-ion secondary battery can be further improved, the cycle performance of the lithium-ion secondary battery can be further improved, and the post-cycle impedance of the lithium-ion secondary battery can be further reduced.

[0047] Specifically, based on 100 parts by weight of organic solvent and lithium salt, the amount of electrolyte additive can be in the following ranges: 0.55 parts by weight to 1.90 parts by weight, 0.60 parts by weight to 1.80 parts by weight, 0.65 parts by weight to 1.70 parts by weight, 0.70 parts by weight to 1.60 parts by weight, 0.75 parts by weight to 1.50 parts by weight, 0.80 parts by weight to 1.40 parts by weight, 0.85 parts by weight to 1.30 parts by weight, 0.90 parts by weight to 1.20 parts by weight, 0.95 parts by weight to 1.10 parts by weight, or 1.00 parts by weight to 1.05 parts by weight.

[0048] In this invention, the organic solvent can be any organic solvent used in electrolytes to date. Examples of organic solvents include, but are not limited to: straight-chain carbonates and / or cyclic carbonates, such as ethylene carbonate, propylene carbonate, butyl carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and fluoroethylene carbonate; ethers, such as 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, and diethyl ether; sulfones, such as sulfolane and methylsulfolane; nitriles, such as acetonitrile, propionitrile, and acrylonitrile; and esters, such as acetates, propionates, and butyrates. These organic solvents can be used alone or in combination. In some embodiments of the present invention, the organic solvent in the electrolyte is selected from one or more of ethylene carbonate, propylene carbonate, butyl carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dihexyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and propyl propionate. In a preferred embodiment, at least one carbonate is used as the organic solvent of the electrolyte of the present invention. In a preferred embodiment, at least one linear carbonate and at least one cyclic carbonate are used together as the organic solvent of the electrolyte of the present invention.

[0049] The present invention places no special restrictions on the lithium salts contained in the electrolyte, and those lithium salts known in the prior art that can be used in lithium battery electrolytes can all be adopted. Examples of lithium salts can include one or more of LiCl, LiBr, LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2F)2, LiN(CF3SO2)2, LiC(CF3SO2)3, LiAlCl4, and Li2SiF6.

[0050] In another typical embodiment of the present invention, a lithium ion secondary battery is provided, including: a positive electrode, a negative electrode, a separator, and the electrolyte described above. Since the lithium ion secondary battery of the present invention uses the electrolyte described above, therefore, this lithium ion secondary battery has an improved initial Coulomb efficiency, improved cycle performance, and reduced impedance after cycling.

[0051] The positive electrode of the present invention includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material. The positive electrode active material layer is formed on both surfaces of the positive electrode current collector. Metal foils such as aluminum foil, nickel foil, or stainless steel foil can be used as the positive electrode current collector.

[0052] The positive electrode active material layer contains one or more positive electrode materials capable of inserting and extracting lithium ions as the positive electrode active material, and may contain additional materials such as a positive electrode binder and / or a positive electrode conductive agent when necessary.

[0053] Preferably, the positive electrode material is a lithium-containing compound. Examples of such lithium-containing compounds include lithium-transition metal composite oxides, lithium-transition metal phosphate compounds, and the like. Lithium-transition metal composite oxides are oxides containing Li and one or more transition metal elements as constituent elements, and lithium-transition metal phosphate compounds are phosphate compounds containing Li and one or more transition metal elements as constituent elements. The transition metal elements are advantageously one or more of Co, Ni, Mn, Fe, etc.

[0054] Examples of lithium-transition metal composite oxides can include, for example, LiCoO2 and LiNiO2, etc. Examples of lithium-transition metal phosphate compounds can include, for example, LiFePO4 and LiFe 1-u Mn u PO4(0 < u < 1), etc.

[0055] The negative electrode of the present invention includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material. The negative electrode active material layer is formed on both surfaces of the negative electrode current collector. Metal foils such as copper (Cu) foil, nickel foil, or stainless steel foil can be used as the negative electrode current collector.

[0056] The negative electrode active material layer contains one or more negative electrode materials capable of inserting and extracting lithium ions as negative electrode active materials, and may contain other materials, such as negative electrode binders and / or negative electrode conductive agents, if necessary.

[0057] The negative electrode active material can be selected from one or more of lithium metal, lithium alloy, carbon materials, silicon or tin and their oxides.

[0058] The separator of the present invention is used to separate the positive and negative electrodes in a battery and allow lithium ions to pass through while preventing short circuits caused by contact between the positive and negative electrodes. The separator is, for example, a porous membrane formed of synthetic resin or ceramic, and may be a laminated membrane in which two or more porous membranes are laminated. Examples of synthetic resins include, for example, polytetrafluoroethylene, polypropylene, and polyethylene.

[0059] In embodiments of the present invention, when the lithium-ion secondary battery is charged, for example, lithium ions are extracted from the positive electrode and embedded in the negative electrode through the electrolyte impregnated in the separator. When the lithium-ion secondary battery is discharged, for example, lithium ions are extracted from the negative electrode and embedded in the positive electrode through the electrolyte impregnated in the separator.

[0060] In another typical embodiment of the present invention, the use of the electrolyte additive of this application in the preparation of lithium-ion secondary batteries is provided. After the electrolyte additive of this application is added to the lithium-ion secondary battery, during the first charge-discharge cycle of the lithium-ion secondary battery, the electrolyte additive of this application will preferentially form a film on the electrode surface over the solvent in the electrolyte, forming a dense protective layer, thereby improving the performance of the lithium-ion secondary battery.

[0061] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0062] Comparative Example 1

[0063] Preparation of positive electrode

[0064] 97.00 g of lithium cobalt oxide (LCO), 1.50 g of Super P conductive agent, and 1.50 g of polyvinylidene fluoride binder were mixed to obtain a positive electrode mixture. The obtained mixture was then dispersed in N-methylpyrrolidone to obtain a positive electrode mixture slurry. Subsequently, the obtained positive electrode mixture slurry was uniformly coated onto aluminum foil to obtain a positive electrode active material layer. The positive electrode active material layer was dried, and a positive electrode sheet was formed using a stamping process.

[0065] Preparation of negative electrode

[0066] 97.50g of graphite powder, 1.00g of carbon black conductive agent, 1.50g of CMC (sodium carboxymethyl cellulose) binder, and an appropriate amount of water were stirred to prepare a negative electrode mixture slurry. The obtained negative electrode mixture slurry was then uniformly coated onto copper foil to obtain a negative electrode active material layer. The negative electrode active material layer was dried, and a negative electrode sheet was formed using a stamping process.

[0067] Preparation of electrolyte

[0068] 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of dihexyl carbonate, 30.50 g of propyl propionate and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte.

[0069] Battery assembly

[0070] The battery was assembled in a dry laboratory. The positive electrode sheet prepared in the above steps was used as the positive electrode, and the negative electrode sheet as the negative electrode. The positive electrode, negative electrode, electrolyte, separator, and coin cell casing were then assembled. After assembly, the battery was allowed to stand for 12 hours to age, yielding a lithium-ion battery.

[0071] Example

[0072] The lithium-ion battery of the present invention was prepared using the same method as in Comparative Example 1, except that the additives represented by the following formulas (1-1), (1-2), (1-3), (1-4), (1-5), (1-6), (1-7), (1-8), (1-9), (1-10), (1-11), or (1-12) were used respectively. For specific dosages, please refer to the following examples.

[0073]

[0074]

[0075] Example 1

[0076] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 0.50 g of the additive represented by formula (1-1) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0077] Example 2

[0078] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of the additive represented by formula (1-1) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0079] Example 3

[0080] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 2.00 g of the additive represented by formula (1-1) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0081] Example 4

[0082] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 0.10 g of the additive represented by formula (1-1) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0083] Example 5

[0084] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 3.00 g of the additive represented by formula (1-1) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0085] Example 6

[0086] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 0.50 g of the additive represented by formula (1-2) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0087] Example 7

[0088] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of the additive represented by formula (1-2) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0089] Example 8

[0090] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 2.00 g of the additive represented by formula (1-2) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0091] Example 9

[0092] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 0.10 g of an additive represented by formula (1-2) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0093] Example 10

[0094] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 3.00 g of the additive represented by formula (1-2) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0095] Example 11

[0096] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-3) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0097] Example 12

[0098] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-4) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0099] Example 13

[0100] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-5) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0101] Example 14

[0102] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-6) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0103] Example 15

[0104] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-7) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0105] Example 16

[0106] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-8) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0107] Example 17

[0108] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-9) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0109] Example 18

[0110] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-10) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0111] Example 19

[0112] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-11) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0113] Example 20

[0114] A lithium-ion battery was prepared using the same method as Comparative Example 1, except that: 21.79 g of ethylene carbonate, 9.89 g of propylene carbonate, 22.40 g of diethyl carbonate, 30.50 g of propyl propionate, and 15.42 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 1.00 g of an additive represented by formula (1-12) was added to the basic electrolyte, and the mixture was stirred thoroughly to manufacture the lithium-ion battery.

[0115] Battery performance testing

[0116] The lithium-ion batteries in Examples 1-20 and Comparative Example 1 were subjected to charge-discharge tests and impedance tests at room temperature and voltages between 3.0 and 4.45 V. The batteries from the examples and comparative examples were first subjected to one 0.1C cycle test at 25°C, and then to 100 1C cycles at 45°C to determine the initial coulombic efficiency, capacity retention after cycling at 45°C, and impedance value after cycling. The experimental results are shown in Table 1 below. Figure 1 , Figure 2 and Figure 3As shown in the image.

[0117] Table 1 Battery performance test results

[0118]

[0119]

[0120] In Table 1, “Electrolyte additive dosage” is a weight percentage based on the total weight of the base electrolyte.

[0121] The test results above show that the embodiments of the present invention achieve the following technical effects:

[0122] A comparison of the results of Examples 1-20 with Comparative Example 1 shows that, compared with Comparative Example 1 which did not add electrolyte additives, the lithium-ion batteries in Examples 1-20, which added additives with the structures shown in Formulas (1-1) to (1-12) in the electrolyte, have higher initial coulombic efficiency, higher capacity retention after cycling at 45°C, and lower post-cycle impedance.

[0123] A comparison of the results of Examples 4-5 with Comparative Example 1 shows that, based on a total weight of 100g of organic solvent and lithium salt, when the amount of electrolyte additive of Formula (1-1) is in the range of 0.10g to 3.00g, the initial coulombic efficiency and capacity retention after cycling at 45°C are improved, and the impedance after cycling is reduced.

[0124] A comparison of the results from Examples 1-3 and Examples 4-5 shows that, based on a total weight of 100g of organic solvent and lithium salt, when the amount of electrolyte additive in formula (1-1) is in the range of 0.50g to 2.00g, the initial coulombic efficiency and capacity retention after cycling at 45°C are further improved, and the impedance after cycling is further reduced.

[0125] Comparing the results of Examples 9-10 with those of Comparative Example 1 yields similar results, namely, based on a total weight of 100g of organic solvent and lithium salt, when the amount of electrolyte additive of formula (1-2) is in the range of 0.10g to 3.00g, the initial coulombic efficiency and capacity retention after cycling at 45°C are improved, and the impedance after cycling is reduced.

[0126] Comparing the results of Examples 6-8 with those of Examples 9-10 yields similar results, namely, based on a total weight of 100g of organic solvent and lithium salt, when the amount of electrolyte additive of formula (1-2) is in the range of 0.50g to 2.00g, the initial coulombic efficiency and capacity retention after cycling at 45°C are further improved, and the post-cycle impedance is further reduced.

[0127] The battery performance test results above show that the lithium-ion secondary battery containing the electrolyte additive of the present invention exhibits excellent performance in terms of initial coulombic efficiency, high-temperature cycle performance, and post-cycle impedance.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrolyte additive, characterized in that, The electrolyte additive comprises a substance represented by the following formula (1): Equation (1) Wherein, R1 is perfluoropropylidene or perfluorobutylidene; and R2 and R3 are each independently a five-membered or six-membered monoheterocyclic group containing one heteroatom, wherein the heteroatom is selected from O, S, or N. R2 and R3 are each independently selected from any one of furanyl, pyrrolyl, pyranyl, thiaranyl, pyridyl, dihydrofuranyl, tetrahydrofuranyl, dihydrothiophenyl, tetrahydrothiophenyl, dihydropyrrolyl, tetrahydropyrrolyl, dihydropyranyl, tetrahydropyranyl, hexahydropyranyl, dihydrothiaranyl, tetrahydrothiaranyl, hexahydrothiaranyl, dihydropyridyl, tetrahydropyridyl, or hexahydropyridyl.

2. The electrolyte additive according to claim 1, characterized in that, R1 is perfluoropropylidene.

3. The electrolyte additive according to claim 1 or 2, characterized in that, R2 and R3 are each independently selected from any one of furanyl, pyrrolyl, pyranyl, thiaranyl, pyridyl, tetrahydrofuranyl, tetrahydrothiophenyl, tetrahydropyrrolyl, tetrahydropyranyl, tetrahydrothiaranyl, or hexahydropyridyl.

4. The electrolyte additive according to claim 1, characterized in that, The electrolyte additive comprises any one of the following substances: , , , , , , , , , , , or .

5. An electrolyte comprising an organic solvent, a lithium salt, and an electrolyte additive according to any one of claims 1 to 4.

6. The electrolyte according to claim 5, characterized in that, The amount of the electrolyte additive is in the range of 0.10 parts by weight to 3.00 parts by weight, based on 100 parts by weight of the organic solvent and the lithium salt.

7. The electrolyte according to claim 5, characterized in that, The amount of the electrolyte additive is in the range of 0.50 parts by weight to 2.00 parts by weight, based on 100 parts by weight of the organic solvent and the lithium salt.

8. The electrolyte according to any one of claims 5 to 7, characterized in that, The organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, butyl carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dihexyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and propyl propionate.

9. A lithium-ion secondary battery, characterized in that, include: positive electrode, negative electrode, Diaphragm, and The electrolyte according to any one of claims 5 to 8.

Images