A non-aqueous electrolyte and a battery

Abstract

This application relates to the technical field of secondary batteries, and specifically relates to a non-aqueous electrolyte and a battery. To overcome the technical problem of poor high-temperature performance of existing batteries, this application provides a non-aqueous electrolyte including at least one of the bicyclic compounds shown in Structural Formula 1. At the same time, this application also discloses a battery including the above non-aqueous electrolyte. The non-aqueous electrolyte and battery provided by this application can effectively improve the high-temperature cycle performance and high-temperature storage performance of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to a non-aqueous electrolyte and a battery. Background Art

[0002] As people's performance requirements for electric vehicles and hybrid electric vehicles are getting higher and higher, battery performance, especially high-temperature performance, faces more challenges. Taking lithium-ion batteries as an example, during the charging process of lithium-ion batteries, lithium ions in the battery's positive electrode material are deintercalated and embedded into the carbon negative electrode through the electrolyte. During this process, the electrolyte reacts with the surface of the carbon negative electrode to generate compounds such as Li2CO3, Li2O, and LiOH, thereby forming a passivation film on the negative electrode surface. This passivation film is called a solid electrolyte interface film (SEI). The SEI film formed during the initial charging process can prevent the electrolyte from further decomposing on the surface of the carbon negative electrode and also plays the role of a lithium-ion tunnel, allowing only lithium ions to pass through. However, as the charge and discharge proceed, the repeated expansion and contraction of the electrode may cause the SEI film to rupture or gradually dissolve, and the exposed anode continues to react with the electrolyte, generating gas at the same time, thereby increasing the internal pressure of the battery and significantly reducing the cycle life of the battery. When the battery is stored or charged and cycled at high temperatures, the volume change of the electrode is more obvious, and the SEI film is more likely to rupture, resulting in a more obvious decline in the electrochemical performance of the battery at high temperatures. Therefore, the quality of the SEI film seriously affects the high-temperature performance of the battery.

[0003] In order to improve the performance of the battery, many researchers have improved the quality of the SEI film by adding different negative electrode film-forming agents to the electrolyte, such as additives like fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, and vinyl sulfate, thereby improving the performance of the battery. However, the above additives are still not ideal in terms of high-temperature storage performance and cycle performance, and electrolyte decomposition still occurs at higher temperatures, resulting in gas expansion, thus bringing serious safety hazards. Therefore, it is necessary to develop new additives to further improve the high-temperature cycle performance and high-temperature storage performance of the battery. Summary of the Invention

[0004] Aiming at the problem of poor high-temperature cycle and high-temperature storage stability of existing secondary batteries, the present application provides a non-aqueous electrolyte and a battery.

[0005] The technical solution adopted by the present application is as follows:

[0006] On the one hand, the present application provides a non-aqueous electrolyte, including at least one of the bicyclic compounds shown in Structural Formula 1:

[0007]

[0008] Among them, X is selected from * is the bonding position, A is selected from a single bond, a carbonyl group, a C1-C10 hydrocarbon group, a C1-C10 halogenated hydrocarbon group or a C2-C10 carbonyl-containing hydrocarbon group, and R1, R2, R3, and R4 are each independently selected from a single bond, a C1-C5 hydrocarbon group or a C1-C5 halogenated hydrocarbon group; preferably, A is selected from a single bond, a carbonyl group, a C1-C6 hydrocarbon group, a C1-C6 halogenated hydrocarbon group or a C2-C6 carbonyl-containing hydrocarbon group, and R1, R2, R3, and R4 are each independently selected from a single bond, a C1-C3 hydrocarbon group or a C1-C3 halogenated hydrocarbon group.

[0009] Specifically, the bicyclic compound is selected from the compounds shown in Structural Formula 1-1 or 1-2:

[0010]

[0011] Among them, A is selected from a single bond, a carbonyl group, a C1-C10 hydrocarbon group, a C1-C10 halogenated hydrocarbon group or a C2-C10 carbonyl-containing hydrocarbon group, and R1, R2, R3, and R4 are each independently selected from a single bond, a C1-C5 hydrocarbon group or a C1-C5 halogenated hydrocarbon group; preferably, A is selected from a single bond, a carbonyl group, a C1-C6 hydrocarbon group, a C1-C6 halogenated hydrocarbon group or a C2-C6 carbonyl-containing hydrocarbon group, and R1, R2, R3, and R4 are each independently selected from a single bond, a C1-C3 hydrocarbon group or a C1-C3 halogenated hydrocarbon group;

[0012]

[0013] Among them, A is selected from a single bond, a carbonyl group, a C1-C10 hydrocarbon group, a C1-C10 halogenated hydrocarbon group or a C2-C10 carbonyl-containing hydrocarbon group, and R1, R2, R3, and R4 are each independently selected from a single bond, a C1-C5 hydrocarbon group or a C1-C5 halogenated hydrocarbon group; preferably, A is selected from a single bond, a carbonyl group, a C1-C6 hydrocarbon group, a C1-C6 halogenated hydrocarbon group or a C2-C6 carbonyl-containing hydrocarbon group, and R1, R2, R3, and R4 are each independently selected from a single bond, a C1-C3 hydrocarbon group or a C1-C3 halogenated hydrocarbon group.

[0014] In the non-aqueous electrolyte provided by the present invention, a bicyclic compound shown in Structural Formula 1 is added as an additive, which can significantly improve the film-forming quality of the passivation film on the electrode surface. This passivation film has the characteristic of high high-temperature stability, and can better adapt to the application environment of secondary batteries under high-voltage conditions. Furthermore, it can effectively improve the high-temperature cycle and high-temperature storage performance of the battery under high-voltage conditions. Its mechanism of action in the battery is speculated as follows: Since the bicyclic compound shown in Structural Formula 1 contains two electrochemically reactive sites (at least one of which is an acid anhydride), the compound formed by locally coordinating with working ions (such as lithium ions) in the electrolyte can preferentially undergo an electrochemical reaction with the electrode over the solvent, and form an organic-inorganic hybrid nanoscale film with more than one lithium salt unit such as lithium sulfonate or lithium sulfate at the scale of the same molecule or adjacent molecules. While ensuring the permeability of lithium ions, the structural strength of the SEI film is improved. At the same time, through local adjustment of the molecular structure, the symmetric or asymmetric structures in the present invention may have an adjusting effect on its performance in different lithium salt systems. When the bicyclic compound shown in Structural Formula 1 is used in combination with other metal salts (such as lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, etc.), its coordination ability may be comparable to the coordination ability of the anions of the metal salts, or the coordination ability and ion migration ability can enable some phosphorus-containing and fluorine-containing anions to also participate in the chemical reaction on the electrode, thereby forming more types of organic-inorganic lithium salts (such as lithium phosphate, lithium fluoride, etc.), and combining them into a nanoscale composite film, avoiding the formation of a relatively fragile structure by a single inorganic crystal structure in a small range, so as to significantly improve the stability of the film at high temperature, and further improve the high-temperature performance of the lithium-ion battery.

[0015] It should be noted that when A is selected from a hydrocarbon group or a halogenated hydrocarbon group, the hydrocarbon group can be a straight-chain hydrocarbon group, a branched-chain hydrocarbon group or a cyclic hydrocarbon group. When R1, R2, R3, R4 are each independently selected from a hydrocarbon group or a halogenated hydrocarbon group, the hydrocarbon group can also be a straight-chain hydrocarbon group, a branched-chain hydrocarbon group or a cyclic hydrocarbon group. When A or R1, R2, R3, R4 is selected from a halogenated hydrocarbon group, a fluorinated hydrocarbon group is preferred.

[0016] Preferably, when A is selected from the bicyclic compound shown in Structural Formula 1 is selected from one or more of the following compounds:

[0017]

[0018]

[0019]

[0020] Preferably, when A is selected from the bicyclic compound shown in Structural Formula 1 is selected from one or more of the following compounds:

[0021]

[0022]

[0023] Those skilled in the art can know the preparation method of the above-mentioned compound based on the common general knowledge in the field of chemical synthesis when knowing the structural formula of the compound shown in Structural Formula 1. For example, the compound shown in Structural Formula 1 can be prepared by the following methods:

[0024] Method 1: Using dihydroxyhexanedisulfonic acid as a raw material, reacting with thionyl chloride to prepare sulfite sulfonic anhydride, further oxidizing to obtain sulfate sulfonic anhydride, and then purifying by recrystallization or column chromatography. An example of its synthetic route is as follows:

[0025]

[0026] Method 2: Using dihydroxyhexanedisulfonic acid as a raw material, dehydrating at high temperature to generate hexanedisulfonic anhydride, and then purifying by recrystallization or column chromatography. An example of its synthetic route is as follows:

[0027]

[0028] Preferably, based on the total mass of the non-aqueous electrolyte being 100%, the addition amount of the bicyclic compound shown in Structural Formula 1 is 0.01 - 10%. Specifically, the addition amount of the bicyclic compound shown in Structural Formula 1 can be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.

[0029] More preferably, based on the total mass of the non-aqueous electrolyte being 100%, the addition amount of the bicyclic compound shown in Structural Formula 1 is 0.1 - 5%.

[0030] Within the above range, the bicyclic compound shown in Structural Formula 1 can significantly improve the high-temperature storage performance and high-temperature cycling performance of the battery, and take into account low impedance and no gas expansion. When the addition amount of the bicyclic compound shown in Structural Formula 1 is less than 0.05%, the content is too low to form a complete passivation film on the surfaces of the positive and negative electrodes, thus it is difficult to significantly improve the high-temperature performance of the non-aqueous electrolyte battery, and the internal resistance of the battery is not significantly reduced. When the addition amount of the bicyclic compound shown in Structural Formula 1 exceeds 10%, an overly thick passivation film is easily formed on the surfaces of the positive and negative electrodes, which instead increases the internal resistance of the battery, and the battery capacity retention rate is significantly deteriorated.

[0031] Preferably, the non-aqueous electrolyte further includes auxiliary additives, which include at least one of cyclic sulfate compounds, cyclic sulfonate compounds, cyclic carbonate compounds, unsaturated phosphate compounds, and nitrile compounds. These auxiliary additives can form a more stable SEI film on the surface of the graphite negative electrode, thereby significantly improving the cycling performance of the battery.

[0032] Preferably, the cyclic sulfate compounds include at least one of ethylene sulfate, propylene sulfate, or vinyl methyl sulfate. Based on the total mass of the non-aqueous electrolyte being 100%, the addition amount of the cyclic sulfate compounds is 0.05% - 10%, preferably 0.1% - 5%, more preferably 0.5% - 3%.

[0033] Preferably, the cyclic carbonate compounds include at least one of vinylene carbonate (VC), ethylene vinylene carbonate (VEC), fluoroethylene carbonate (FEC), or the compound shown in Structural Formula 2.

[0034]

[0035] In the Structural Formula 2, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 are each independently selected from a hydrogen atom, a halogen atom, or a C1-C5 group.

[0036] More preferably, the compound shown in Structural Formula 2 includes at least one of the compounds shown in Compounds 2-1 to 2-6 below:

[0037]

[0038] The cyclic carbonate compounds can form a film together with the bicyclic compound shown in Structural Formula 1 and have a synergistic effect, thereby forming a passivation film with lower impedance and further improving the high-temperature performance of the battery. Of course, it should be understood that the specific types of the cyclic carbonate compounds are not limited to this.

[0039] Further preferably, based on the total mass of the non-aqueous electrolyte being 100%, the addition amount of the cyclic carbonate compounds is generally 0.01% - 10%, preferably 0.1% - 5%, more preferably 0.5% - 3%. In particular, the addition amount of the fluoroethylene carbonate (FEC) is generally 0.01 - 30%, preferably 0.1 - 10%, more preferably 0.5 - 5%.

[0040] Preferably, the unsaturated phosphate compounds are selected from at least one of the compounds shown in Structural Formula 3:

[0041]

[0042] R 31 、R 32 、R 33 Each independently selected from saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and at least one of R 31 、R 32 、R 33 is an unsaturated hydrocarbon group.

[0043] More preferably, the unsaturated phosphate ester compounds may be at least one of triallyl phosphate, diallylmethyl phosphate, diallylethyl phosphate, diallylpropyl phosphate, diallyltrifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallylhexafluoroisopropyl phosphate, tripropargyl phosphate, diallylmethyl phosphate, diallylethyl phosphate, diallylpropyl phosphate, diallyltrifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallylhexafluoroisopropyl phosphate.

[0044] The unsaturated phosphate ester compounds represented by the structural formula 3 are used as positive electrode film-forming additives and participate in the formation of the passivation film on the surface of the positive electrode material. This passivation film isolates the electrolyte from the positive electrode interface, can inhibit the side reactions at the electrolyte-positive electrode interface, plays a role in protecting the positive electrode, and at the same time inhibits the dissolution of transition metals in the positive electrode material, improving the impedance growth and capacity loss of the battery. In addition, the unsaturated phosphate esters represented by the structural formula 3 and the compounds represented by the structural formula 1 have a synergistic effect, forming a dense and stable SEI film on the negative electrode surface, effectively preventing the reduction reaction of the electrolyte on the negative electrode surface and the deposition of transition metals, improving the interface between the negative electrode and the electrolyte, and slowing down the side reactions at the electrode interface during storage or cycling, thereby improving the high-temperature storage and high-temperature cycling performance of the battery. Preferably, based on the total mass of the non-aqueous electrolyte being 100%, the weight percentage of the unsaturated phosphate ester compounds is 0.1% - 2.0%. When the weight percentage of the unsaturated phosphate ester compounds in the non-aqueous electrolyte is between 0.1% and 2.0%, it has a good effect on promoting the formation of the SEI film. When the weight percentage of the phosphate ester compounds in the non-aqueous electrolyte is less than 0.1% or greater than 2.0%, the promotion effect on the SEI film on the electrode will decrease.

[0045] The nitrile compounds include one or more of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexane trinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, sebaconitrile.

[0046] It should be noted that, unless otherwise specified, generally, the addition amount of any optional substance in the auxiliary additive in the non-aqueous electrolyte is 10% or less. Preferably, the addition amount is 0.1 - 5%, and more preferably, the addition amount is 0.1% - 3%. Specifically, the addition amount of any optional substance in the auxiliary additive can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.

[0047] In some embodiments, when the auxiliary additive is selected from vinylene carbonate fluoride, based on the total mass of the non-aqueous electrolyte being 100%, the addition amount of the vinylene carbonate fluoride is 0.05% - 30%.

[0048] The inventors found through a large number of experiments that: the bicyclic compound shown in Structural Formula 1 provided by the present invention, when used in combination with the above-mentioned auxiliary additive, shows an obvious synergistic improvement effect in enhancing the high-temperature cycle performance of the battery, indicating that the bicyclic compound shown in Structural Formula 1 and the above-mentioned additive form a film together on the electrode surface, which can make up for the film-forming defects of single addition, obtain a more stable passivation film, and jointly improve the battery cycle performance and high-temperature storage performance through synergistic effects.

[0049] Preferably, the non-aqueous electrolyte further includes an electrolyte salt, and the electrolyte salt includes one or more of lithium salts, sodium salts, potassium salts, magnesium salts, zinc salts, and aluminum salts. In a preferred embodiment, the electrolyte salt is selected from lithium salts or sodium salts.

[0050] In a preferred embodiment, the lithium salt is selected from at least one of LiPF6, LiBOB, LiDFOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO2F)2, LiClO4, LiAlCl4, LiCF3SO3, Li2B 10 Cl 10 , and lithium salts of lower aliphatic carboxylic acids. When the electrolyte salt is selected from other salts such as sodium salts, potassium salts, magnesium salts, zinc salts, or aluminum salts, the lithium in the above lithium salts can be correspondingly replaced with sodium, potassium, magnesium, zinc, or aluminum, etc.

[0051] In a preferred embodiment, the sodium salt is selected from at least one of sodium perchlorate (NaClO4), sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium trifluoromethanesulfonate (NaFSI), and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI).

[0052] In some embodiments, in the non-aqueous electrolyte, the concentration of the electrolyte salt is 0.1 mol / L - 8 mol / L. In a preferred embodiment, in the non-aqueous electrolyte, the concentration of the electrolyte salt is 0.5 mol / L - 2.5 mol / L. Specifically, the concentration of the electrolyte salt can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L.

[0053] Preferably, the non-aqueous electrolyte further includes a solvent, and the solvent includes one or more of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylate solvent, and a sulfone solvent.

[0054] Preferably, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms. Specifically, the cyclic ether can be, but is not limited to, one or more of 1,3-dioxolane (DOL), 1,4-dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF); the chain ether can be, but is not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Since the chain ether has a high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. The ether compound can be used alone or in combination of two or more in any combination and ratio. The addition amount of the ether compound is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the high-compaction lithium-ion battery of the present invention. In a non-aqueous solvent with a volume ratio of 100%, the volume ratio is usually 1% or more, preferably 2% or more, more preferably 3% or more. In addition, the volume ratio is usually 30% or less, preferably 25% or less, more preferably 20% or less. When two or more ether compounds are used in combination, the total amount of the ether compounds only needs to satisfy the above range. When the addition amount of the ether compound is within the above preferred range, it is easy to ensure the improvement effect of ionic conductivity brought by the increase in lithium-ion dissociation degree and the decrease in viscosity of the chain ether. In addition, when the negative electrode active material is a carbon material, the phenomenon of co-insertion of the chain ether and lithium ions can be suppressed, so that the input / output characteristics and charge / discharge rate characteristics can reach an appropriate range.

[0055] Preferably, the nitrile solvent may specifically be, but is not limited to, one or more of acetonitrile, glutarodinitrile, and malononitrile.

[0056] Preferably, the carbonate solvent includes cyclic carbonates or chain carbonates. The cyclic carbonate may specifically be, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate (BC); the chain carbonate may specifically be, but is not limited to, one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). There is no special limitation on the content of the cyclic carbonate, and it is arbitrary within the range that does not significantly damage the effect of the high-compaction lithium-ion battery of the present invention. However, when using only one kind, the lower limit of its content is usually 3% or more, preferably 5% or more, by volume, relative to the total amount of the solvents of the non-aqueous electrolyte. By setting this range, it is possible to avoid a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte, and it is easy to make the high-current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery reach a good range. In addition, the upper limit is usually 90% or less, preferably 85% or less, more preferably 80% or less, by volume. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, which helps to improve the stability during high-temperature storage. There is no special limitation on the content of the chain carbonate. Relative to the total amount of the solvents of the non-aqueous electrolyte, it is usually 15% or more, preferably 20% or more, more preferably 25% or more, by volume. In addition, it is usually 90% or less, preferably 85% or less, more preferably 80% or less, by volume. By making the content of the chain carbonate within the above range, it is easy to make the viscosity of the non-aqueous electrolyte reach an appropriate range, suppress the decrease in ionic conductivity, and further help to make the output characteristics of the non-aqueous electrolyte battery reach a good range. When using two or more chain carbonates in combination, it is only necessary to make the total amount of the chain carbonates satisfy the above range.

[0057] Preferably, a chain carbonate having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonate") may also be preferably used. The number of fluorine atoms of the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms may be bonded to the same carbon or to different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.

[0058] Preferably, the carboxylic acid ester solvent may specifically be, but is not limited to, one or more of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate.

[0059] Preferably, the sulfone solvent includes cyclic sulfones and chain sulfones. However, preferably, in the case of cyclic sulfones, they are usually compounds having 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and in the case of chain sulfones, they are usually compounds having 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. There is no special limitation on the addition amount of the sulfone solvent, and it is arbitrary within the range that does not significantly damage the effect of the high-compaction lithium-ion battery of the present invention. Relative to the total amount of the solvent in the non-aqueous electrolyte, the volume ratio is usually 0.3% or more, preferably 0.5% or more, more preferably 1% or more. Additionally, the volume ratio is usually 40% or less, preferably 35% or less, more preferably 30% or less. When two or more sulfone solvents are used in combination, the total amount of the sulfone solvents only needs to satisfy the above range. When the addition amount of the sulfone solvent is within the above range, it tends to obtain an electrolyte with excellent high-temperature storage stability.

[0060] More preferably, the solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate.

[0061] On the other hand, the present application also provides a battery, including a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte as described above.

[0062] Since the battery adopts the non-aqueous electrolyte as described above, a passivation film with excellent performance can be formed on the positive electrode and the negative electrode, thereby effectively improving the high-temperature storage performance and high-temperature cycle performance of the battery and enhancing the battery power characteristics.

[0063] Preferably, the battery is a secondary battery, and the secondary battery can be a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a magnesium secondary battery, a zinc secondary battery, an aluminum secondary battery, etc.

[0064] Preferably, the battery is a lithium metal battery, a lithium-ion battery, a lithium-sulfur battery, or a sodium-ion battery.

[0065] Preferably, the positive electrode includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the type of the positive electrode active material is not particularly limited and can be selected according to actual needs as long as it is a positive electrode active material or a conversion-type positive electrode material that can reversibly intercalate / deintercalate metal ions (such as lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.).

[0066] Preferably, the battery is a lithium-ion battery, and its positive electrode active material can be selected from LiFe1-x’ M’ x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z One or more of O2, wherein M’ is selected from one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, M is selected from one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0 ≤ x’ < 1, 0 ≤ y’ ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x ≤ 1, 0 ≤ z ≤ 1, x + y + z ≤ 1. The positive electrode active material may also be selected from one or several of sulfides, selenides, and halides. More preferably, the positive electrode active material may be selected from LiCoO2, LiFePO4, LiFe 0.8 Mn 0.2 PO4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2, LiMn2O4, LiNi 0.5 Co 0.2 Al 0.3 One or more of O2.

[0067] Preferably, the battery is a sodium ion battery, and its positive electrode active material may be selected from one or several of metallic sodium, carbon materials, alloy materials, transition metal oxides, transition metal sulfides, phosphorus-based materials, titanate materials, Prussian blue-based materials. The carbon materials may be selected from one or several of graphite, soft carbon, and hard carbon. The alloy materials may be alloy materials composed of at least two of Si, Ge, Sn, Pb, and Sb, and the alloy materials may also be alloy materials composed of at least one of Si, Ge, Sn, Pb, and Sb and C. The chemical formulas of the transition metal oxides and the transition metal sulfides are M1 x N y, M1 can be selected from one or more of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V, N is selected from O or S, the phosphorus-based material can be selected from one or more of red phosphorus, white phosphorus, and black phosphorus, and the titanate material can be selected from one or more of Na2Ti3O7, Na2Ti6O 13 , Na4Ti5O 12 , Li4Ti5O 12 , one or more of NaTi2(PO4)3, and the molecular formula of the Prussian blue-based material is Na x M[M′(CN)6] y ·zH2O, where M is a transition metal, M′ is a transition metal, 0 < x ≤ 2, 0.8 ≤ y < 1, 0 < z ≤ 20.

[0068] Preferably, the positive electrode further includes a positive electrode current collector, and the positive electrode material layer covers the surface of the positive electrode current collector.

[0069] The positive electrode current collector is selected from metal materials that can conduct electrons. Preferably, the positive electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0070] Preferably, the positive electrode active material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent are blended to obtain the positive electrode active material layer.

[0071] Preferably, the positive electrode binder includes one or more of thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene, copolymers of tetrafluoroethylene - hexafluoropropylene, copolymers of tetrafluoroethylene - perfluoroalkyl vinyl ether, copolymers of ethylene - tetrafluoroethylene, copolymers of vinylidene fluoride - tetrafluoroethylene, copolymers of vinylidene fluoride - trifluoroethylene, copolymers of vinylidene fluoride - trichloroethylene, copolymers of vinylidene fluoride - fluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene - butadiene rubber.

[0072] Preferably, the positive electrode conductive agent includes one or more of metal conductive agents, carbon-based materials, metal oxide-based conductive agents, and composite conductive agents. Specifically, the metal conductive agent can be metals such as copper powder, nickel powder, and silver powder; the carbon-based material can be carbon-based materials such as conductive graphite, conductive carbon black, conductive carbon fiber, or graphene; the metal oxide-based conductive agent can be tin oxide, iron oxide, zinc oxide, etc.; the composite conductive agent can be composite powder, composite fiber, etc. More specifically, the conductive carbon black can be one or more of acetylene black, 350G, Ketjen black, carbon fiber (VGCF), and carbon nanotubes (CNTs).

[0073] Preferably, the negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one or more of a silicon-based negative electrode, a carbon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. Among them, the silicon-based negative electrode includes one or more of silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials; the carbon-based negative electrode includes one or more of graphite, hard carbon, soft carbon, graphene, and mesophase carbon microspheres; the tin-based negative electrode includes one or more of tin, tin-carbon, tin-oxygen, and tin metal compounds; the lithium negative electrode includes one or more of metallic lithium and lithium alloys. The lithium alloy may specifically be at least one of a lithium-silicon alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-aluminum alloy, a lithium-tin alloy, and a lithium-indium alloy.

[0074] Preferably, the negative electrode further includes a negative electrode current collector, and the negative electrode active material layer covers the surface of the negative electrode current collector. The material of the negative electrode current collector may be the same as that of the positive electrode current collector, which will not be elaborated here.

[0075] Preferably, the negative electrode active material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent are blended to obtain the negative electrode active material layer. The negative electrode binder and the negative electrode conductive agent may be the same as the positive electrode binder and the positive electrode conductive agent respectively, which will not be elaborated here.

[0076] Preferably, the separator can be an existing conventional separator, which can be a ceramic separator, a polymer separator, a non-woven fabric, an inorganic-organic composite separator, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP, and three-layer PP / PE / PP separators.

[0077] The non-aqueous electrolyte provided by the present application contains a bicyclic compound shown in Structural Formula 1, which can greatly improve the film formation of the non-aqueous electrolyte on the positive and negative electrodes with a small addition amount. The formed passivation film has great flexibility, high stability, relatively slow impedance growth, improves the performance stability of the positive and negative electrode materials during long-term cycling, extends the cycle life of the battery. At the same time, the stability of the passivation film at high temperatures is particularly excellent. Therefore, using the non-aqueous electrolyte provided by the present application helps to improve the high-temperature performance of the battery and enhances the environmental adaptability of the battery. Detailed implementation manners

[0078] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the embodiments in the present application. Obviously, the described embodiments are only a 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 of ordinary skill in the art without creative efforts belong to the protection scope of the present application.

[0079] The present application will be further described below through embodiments.

[0080] Table 1

[0081]

[0082]

[0083] Note: Compounds 1-6 used in the following examples and comparative examples are selected from Table 1.

[0084] Example 1

[0085] 1) Preparation of non-aqueous electrolyte:

[0086] Ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) were mixed at a mass ratio of EC:DEC:EMC = 1:1:1, and then lithium hexafluorophosphate (LiPF6) was added to a molar concentration of 1 mol / L. Based on the total weight of the non-aqueous electrolyte being 100%, compound 1 was added in the amount shown in Example 1 of Table 2.

[0087] 2) Preparation of positive electrode plate:

[0088] The positive electrode active material lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 93:4:3, and then they were dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The slurry was uniformly coated on both sides of the aluminum foil, dried, calendered, and vacuum dried, and then an aluminum lead wire was welded with an ultrasonic welder to obtain a positive electrode plate, and the thickness of the electrode plate was between 120-150 μm.

[0089] 3) Preparation of negative electrode plate:

[0090] The negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed at a mass ratio of 94:1:2.5:2.5, and then they were dispersed in deionized water to obtain a negative electrode slurry. The slurry was coated on both sides of the copper foil, dried, calendered, and vacuum dried, and then a nickel lead wire was welded with an ultrasonic welder to obtain a negative electrode plate, and the thickness of the electrode plate was between 120-150 μm.

[0091] 4) Preparation of battery cell:

[0092] A three-layer separator with a thickness of 20 μm is placed between the positive electrode plate and the negative electrode plate. Then, the sandwich structure composed of the positive electrode plate, the negative electrode plate, and the separator is wound. After that, the wound body is flattened and placed in an aluminum foil packaging bag, and vacuum baked at 75 °C for 48 h to obtain a battery cell to be filled with electrolyte.

[0093] 5) Electrolyte filling and formation of the battery cell:

[0094] In a glove box with the dew point controlled below -40 °C, the electrolyte prepared above is injected into the battery cell, and after vacuum packaging, it is left standing for 24 h.

[0095] Then, the following steps are carried out for the conventional formation of the first charge: constant current charging at 0.05C for 180 min, constant current charging at 0.2C until 3.95V, secondary vacuum sealing, and then further constant current charging at a current of 0.2C until 4.2V. After standing at room temperature for 24 h, it is discharged at a constant current of 0.2C until 3.0V to obtain a LiNi 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium-ion battery.

[0096] II. Battery performance testing

[0097] (1) High-temperature cycle performance testing

[0098] The lithium-ion battery prepared in Example 1 is placed in an oven at a constant temperature of 45 °C, and charged at a constant current of 1C until 4.2V (LiNi 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium-ion battery), then charged at a constant voltage until the current drops to 0.02C, and then discharged at a constant current of 1C until 3.0V. Such a cycle is carried out, and the discharge capacity of the first time and the discharge capacity of the last time are recorded.

[0099] The capacity retention rate of the cycle is calculated according to the following formula:

[0100] Battery capacity retention rate (%) = Discharge capacity of the last time / Discharge capacity of the first time × 100%.

[0101] (2) High-temperature storage performance testing

[0102] The lithium-ion battery prepared in Example 1 is formed and then charged at a constant current and constant voltage of 1C to 4.2V (LiNi 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium-ion battery) at room temperature. The initial discharge capacity and the initial battery thickness are measured. Then, after storing in an environment of 60 °C for 30 days, it is discharged to 3.0V at 1C, and the retention capacity, recovery capacity of the battery, and the battery thickness after storage are measured. The calculation formulas are as follows:

[0103] Battery capacity retention rate (%) = Retained capacity / Initial capacity × 100%;

[0104] Battery capacity recovery rate (%) = Recovered capacity / Initial capacity × 100%;

[0105] Volume expansion rate (%) = (Battery thickness after storage - Initial battery thickness) / Initial battery thickness × 100%, and the test results are shown in Table 2.

[0106] Examples 2 - 17

[0107] Examples 2 - 17 are used to illustrate the non-aqueous electrolyte, lithium-ion battery and its preparation method of the present application, including most of the operation steps in Example 1, and the differences are as follows:

[0108] In the preparation steps of the non-aqueous electrolyte:

[0109] Based on the total weight of the non-aqueous electrolyte being 100%, components with the addition amounts shown in Examples 2 - 17 in Table 2 are added. The obtained test results are filled in Table 2.

[0110] Comparative Examples 1 - 6

[0111] Comparative Examples 1 - 6 are used to comparatively illustrate the non-aqueous electrolyte, lithium-ion battery and its preparation method of the present application, including most of the operation steps in Example 1, and the differences are as follows:

[0112] Based on the total weight of the non-aqueous electrolyte being 100%, components with the addition amounts shown in Comparative Examples 1 - 6 in Table 2 are added. The obtained test results are filled in Table 2.

[0113] Table 2

[0114]

[0115]

[0116] Comparing the test results of Comparative Examples 1-8, it can be seen that as the addition amount of the bicyclic compound shown in Structural Formula 1 increases, the high-temperature cycling performance and high-temperature storage performance of the lithium-ion battery first increase and then decrease. In particular, when the addition amount of the compound shown in Structural Formula 1 is 0.5-5%, the lithium-ion battery has the optimal high-temperature cycling performance and storage performance. That is, when the addition amount of the bicyclic compound shown in Structural Formula 1 is too low, the improvement of the performance of the lithium-ion battery is not obvious enough. However, the addition amount of the bicyclic compound shown in Structural Formula 1 is not the more the better. The reason is that as the content of the bicyclic compound shown in Structural Formula 1 is added, the composition of the passivation film on the electrode surface changes. Since the composition of the passivation film is relatively complex, including the mixed products obtained from the decomposition of electrolyte salts, solvents, and additives, its performance is the comprehensive performance of the combined components. If the content of the decomposition products of the bicyclic compound shown in Structural Formula 1 in the passivation film is too large due to the excessive addition of the bicyclic compound shown in Structural Formula 1, it is instead not conducive to the inhibitory effect of the passivation film on gas generation during high-temperature storage.

[0117] Comparing the test results of Comparative Example 4, Examples 9-13 and Comparative Examples 1-5, it can be seen that compared with the traditional vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and triallyl phosphate, using the bicyclic compound shown in Structural Formula 1 provided in the present application as an additive can greatly improve the film formation on the positive and negative electrodes of the non-aqueous electrolyte, and improve the storage performance and cycling performance of the lithium-ion battery at high temperatures.

[0118] Comparing the test results of Comparative Example 4 and Examples 14-17, it can be seen that compared with the single addition of the bicyclic compound shown in Structural Formula 1, the bicyclic compound shown in Structural Formula 1 and the auxiliary additive are used in combination to have a synergistic effect, forming a film together on the electrode surface to make up for the film formation defects of single addition, obtaining a more stable passivation film, and jointly improving the battery cycling performance and high-temperature storage performance.

[0119] Comparing the test results of Example 14 and Comparative Example 6, it can be seen that compared with the traditional combination additives of vinylene carbonate (VC) and ethylene sulfate (DTD), using the bicyclic compound shown in Structural Formula 1 provided in the present application in combination with vinylene carbonate (VC) further improves the high-temperature performance of the battery, indicating that the decomposition products of the bicyclic compound shown in Structural Formula 1 have good affinity with the decomposition products of vinylene carbonate (VC), and the combined product obtained by their joint combination has higher stability at high temperatures than their individual decomposition products. Therefore, the passivation film formed by the compound shown in Structural Formula 1 and ethylene sulfate shows more excellent high-temperature stability.

[0120] In summary, the non-aqueous electrolyte provided by this application contains the bicyclic compound shown in Structural Formula 1, enabling the battery to form a stable SEI film during charge and discharge processes, improving the performance stability of the positive and negative electrode materials during long-term cycling, and enhancing the electrochemical performance of the battery under high-temperature conditions.

[0121] The above further describes this application with the aid of specific embodiments. However, it should be understood that this specific description should not be construed as a limitation on the essence and scope of this application. Various modifications made by those of ordinary skill in the art to the above embodiments after reading this specification all fall within the scope protected by this application.

Claims

1. A non-aqueous electrolyte, characterized in that, including at least one of the bicyclic compounds shown in Structural Formula 1: Among them, X is selected from * is the bonding position, A is selected from a single bond, a carbonyl group, a C1-C10 hydrocarbon group, a C1-C10 halogenated hydrocarbon group or a C2-C10 carbonyl-containing hydrocarbon group, and R1, R2, R3, and R4 are each independently selected from a single bond, a C1-C5 hydrocarbon group or a C1-C5 halogenated hydrocarbon group.

2. The non-aqueous electrolyte according to claim 1, wherein The bicyclic compound shown in Structural Formula 1 is selected from one or more of the following compounds:

3. The non-aqueous electrolyte according to claim 1, characterized in that, Based on the total mass of the non-aqueous electrolyte being 100%, the addition amount of the bicyclic compound is 0.1% - 5.0%.

4. The non-aqueous electrolyte according to claim 1, wherein The non-aqueous electrolyte further includes an auxiliary additive, and the auxiliary additive includes at least one of cyclic sulfate compounds, cyclic sulfonate compounds, cyclic carbonate compounds, unsaturated phosphate compounds, and nitrile compounds.

5. The non-aqueous electrolyte according to claim 4, characterized in that, The cyclic sulfate compound is selected from at least one of ethylene sulfate, propylene sulfate, or vinyl methyl sulfate; The cyclic sulfonate compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone, or 1,3-propene sultone; The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene vinylene carbonate, fluoroethylene carbonate, or the compound shown in Structural Formula 2, In the said structural formula 2, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 are each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group; The unsaturated phosphate compound is selected from at least one of the compounds shown in Structural Formula 3: R 31 、R 32 、R 33 Each independently selected from saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 )3, where m is a natural number from 1 to 3, and at least one of R 31 、R 32 、R 33 is an unsaturated hydrocarbon group; The nitrile compound includes one or more of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexane trinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, sebaconitrile.

6. The non-aqueous electrolyte according to claim 4, characterized in that, Based on the total mass of the non-aqueous electrolyte being 100%, the addition amount of each of the auxiliary additives is 0.05 - 10%.

7. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte further includes an electrolyte salt selected from at least one of LiPF6, LiBOB, LiDFOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO2F)2, LiClO4, LiAlCl4, LiCF3SO3, Li2B 10 Cl 10 , and lower aliphatic carboxylic acid electrolyte salts.

8. The non-aqueous electrolyte according to claim 1, wherein The non-aqueous electrolyte further includes a solvent, and the solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate.

9. A battery, characterized in that, including a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte according to any one of claims 1 - 8.

10. The battery according to claim 9, wherein The positive electrode includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material selected from LiFe 1-x’ M’ x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z O2, and one or more of them, wherein M’ is selected from one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, M is selected from one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0≤x’<1, 0≤y’≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x + y + z≤1.

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