Electrolyte, secondary battery, and device

Abstract

The invention relates to an electrolyte, the electrolyte comprises a lithium salt, an organic solvent and an additive, the additive comprises a pyridine trifluoroacetate compound, a chlorodifluoroacetate compound and LiNO3, the electrolyte provided by the invention can significantly reduce a Li < + > diffusion energy barrier and promote compact lithium deposition, and the lithium ion battery can be used as a lithium ion battery. According to the present invention, the pyridine trifluoroacetate, the chlorodifluoromethyl acetate and the LiNO3 in the electrolyte can form the uniform and compact CEI film on the surface of the positive electrode, such that the structure of the positive electrode active material is greatly protected, and the dissolution of the transition metal is inhibited so as to provide the excellent cycle performance of the lithium metal battery;

Description

Technical Field

[0001] The present disclosure relates to the technical field of energy storage materials, and in particular to an electrolyte and a secondary battery and a device containing the same. Background Art

[0002] Lithium metal (Li) has a high theoretical capacity (3860 mAh / g), the lowest potential (-3.04 relative to standard hydrogen electrode) and a moderate density (0.534 g / cm 3 ) is considered to be the ultimate choice for negative electrode materials. However, the carbonate electrolytes currently used in lithium-ion batteries are incompatible with lithium metal, and the violent reaction between the two generates a solid electrolyte interface (SEI) dominated by organic matter. As the cycle continues, problems such as SEI rupture, lithium dendrite growth, and the formation of "dead lithium" form a vicious cycle, consuming limited active lithium and ultimately causing a rapid decline in the electrochemical performance of the battery. Lithium nitrate (LiNO3), as a commonly used additive in ether electrolytes, has a significant improvement in battery performance. However, its extremely low solubility in carbonate electrolytes (<10 -5 g / mL) limits its application in carbonate electrolytes, so there is an urgent need to develop a new electrolyte suitable for lithium metal batteries. Summary of the invention

[0003] In view of the problems existing in the prior art, the present disclosure provides an electrolyte, characterized in that the electrolyte comprises a lithium salt, an organic solvent and an additive, wherein the additive comprises a pyridine trifluoroacetate compound represented by the following chemical formula I, a chlorodifluoroacetate compound represented by the following chemical formula II and LiNO3:

[0004]

[0005] In one aspect of the present disclosure, R1, R2, R3, R4 and R5 are independently selected from hydrogen, C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl or C 3-8 Epoxyalkyl; the C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl or C 3-8 The alkylene oxide is optionally replaced by one or more C1-3 Alkyl substitution.

[0006] In one aspect of the present disclosure, R6 is selected from C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl, C 3-8 Epoxyalkyl, C 6-12 Aryl or C 6-12 Heteroaryl, the C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl, C 3-8 Epoxyalkyl, C 6-12 Aryl or C 6-12 The heteroaryl group is optionally substituted with one or more C 1-3 Alkyl substitution.

[0007] In one aspect of the present disclosure, the mass ratio of the pyridine trifluoroacetate compound to the chlorodifluoroacetate compound is selected from 1:(0.3-2.1).

[0008] In one aspect of the present disclosure, in the additive, the mass ratio of the pyridine trifluoroacetate compound, the chlorodifluoroacetate compound and LiNO3 is selected from 1:(0.3-2.1):(0.06-0.7).

[0009] In one aspect of the present disclosure, in the additive, the mass ratio of the pyridine trifluoroacetate compound, the chlorodifluoroacetate compound and LiNO3 is selected from 1:(0.5-1):(0.2-0.3).

[0010] In one aspect of the present disclosure, the pyridine trifluoroacetate compound is selected from the following compound IA, and the chlorodifluoroacetate compound is selected from the following compound II-A:

[0011]

[0012] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the pyridine trifluoroacetate compound is selected from 0.1% to 6.2%.

[0013] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the chlorodifluoroacetate compound is selected from 1.8% to 4.2%.

[0014] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the LiNO3 is selected from 0.3% to 1.3%.

[0015] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the pyridine trifluoroacetate compound is selected from 3.5% to 4.5%.

[0016] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the chlorodifluoroacetate compound is selected from 2% to 4%.

[0017] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the LiNO3 is selected from 0.8% to 1.2%.

[0018] In one aspect of the present disclosure, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium dioxalatoborate, 4,5-dicyano-2-trifluoromethylimidazole lithium, lithium difluorophosphate, lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)amide and lithium bis(trifluoromethylsulfonyl)amide.

[0019] In one aspect of the present disclosure, the organic solvent includes at least one of a carbonate compound, an ether compound, a carboxylate compound, a sulfoxide compound, and a nitrile compound.

[0020] In one aspect of the present disclosure, the pyridine trifluoroacetate compound is pyridine trifluoroacetate.

[0021] In one aspect of the present disclosure, the chlorodifluoroacetate compound is methyl chlorodifluoroacetate.

[0022] In one aspect of the present disclosure, in the additive, the mass ratio of the pyridine trifluoroacetate, methyl chlorodifluoroacetate and LiNO3 is selected from 1:(0.3-2):(0.065-0.6).

[0023] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the pyridine trifluoroacetate is selected from 1.5% to 6.2%.

[0024] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the methyl chlorodifluoroacetate is selected from 1.5% to 4%.

[0025] In one aspect of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the LiNO3 is selected from 0.4% to 1.2%.

[0026] In one aspect of the present disclosure, in the electrolyte, the molar concentration of the lithium salt is selected from 0.3 mol / L-3 mol / L.

[0027] In one aspect of the present disclosure, the carbonate compound includes at least one of a cyclic carbonate compound and a chain carbonate compound, the cyclic carbonate compound includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and γ-butyrolactone, and the chain carbonate compound includes dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, and C 1-4 At least one of the carbonate derivatives synthesized from a fatty monoalcohol and carbonic acid.

[0028] In one aspect of the present disclosure, the ether compound includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, ethylene glycol dimethyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, ethylene glycol bis(propionitrile) ether and polyethylene glycol monomethyl ether.

[0029] In one aspect of the present disclosure, the carboxylate compound includes at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0030] In one aspect of the present disclosure, the sulfoxide compound includes at least one of dimethyl sulfoxide and diethyl sulfoxide.

[0031] In one aspect of the present disclosure, the nitrile compound includes at least one of acetonitrile, propionitrile, butyronitrile, benzonitrile and malononitrile.

[0032] The present disclosure also provides a secondary battery, which includes the aforementioned electrolyte.

[0033] The secondary batteries involved in the present disclosure include, but are not limited to, lithium metal batteries.

[0034] In one aspect of the present disclosure, the secondary battery further includes a positive electrode and a negative electrode.

[0035] In one aspect of the present disclosure, the positive electrode includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector.

[0036] In one aspect of the present disclosure, the positive electrode active material may include a ternary positive electrode material, but is not limited thereto.

[0037] In one aspect of the present disclosure, the negative electrode includes a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector.

[0038] In one aspect of the present disclosure, the negative electrode active material includes lithium metal and / or lithium alloy.

[0039] In one aspect of the present disclosure, the organic solvent is selected from the combination of ethylene carbonate, propylene carbonate and dimethyl carbonate.

[0040] The present disclosure also provides a device, which includes the aforementioned secondary battery.

[0041] In the present disclosure, the role of chlorodifluoroacetate compounds is as follows: difluoroacetate compounds can undergo a Clauson ester condensation reaction on the surface of a metal lithium negative electrode, that is, esters containing α-active hydrogen undergo a condensation reaction under the action of an alkaline reagent to form a β-ketoester compound. The nucleophilic site brought by the special -CHF2 group of the difluoroacetate compound can form a polymer-rich layer very quickly, and the high fluorine content of the polymer can provide good thermal stability for the interface layer. The constructed high thermal stability polymer interface layer can greatly inhibit the subsequent side reactions between metal lithium and the electrolyte. After Cl in methyl chlorodifluoroacetate replaces H in difluoroacetate compounds, the dissociation ability of lithium salts is increased, the ion transfer impedance is reduced, the stability of the electrolyte is further increased, the possibility of gas production is reduced, and the ignition point is improved.

[0042] In the present disclosure, the role of LiNO3 is to change Li + The solvation structure of NO3 - Can replace Li + Some of the solvent molecules in the solvation shell, so Li + It is easier to desolvate during the deposition process, thereby inhibiting the growth of lithium dendrites; in addition, the addition of LiNO3 can reduce the number of solvent molecules around the cations, thereby reducing the decomposition of the solvent on the negative electrode surface, thereby forming a SEI film with more inorganic components, which not only helps the stability of the SEI film, but also promotes Li + Uniform deposition on the negative electrode surface.

[0043] In the present disclosure, the pyridinium trifluoroacetate compounds are easily soluble in carbonate electrolytes and have better compatibility with lithium metal; thanks to the strong coordination between the carbonyl group (C=O) and lithium, the trifluoroacetic acid anion promotes the dissolution of LiNO3 in the carbonate electrolyte, forming an anion-rich solvation environment and reducing the lithium desolvation energy barrier; in addition, due to electrostatic interactions, the pyridinium cation can be adsorbed on the negatively charged lithium metal surface and preferentially undergo reduction reactions, thereby regulating subsequent deposition reactions.

[0044] In the present disclosure, both the pyridine trifluoroacetate compounds and the chlorodifluoroacetate compounds can promote the dissolution of LiNO3 in the carbonate electrolyte.

[0045] In the present disclosure, the pyridine trifluoroacetate and methyl chlorodifluoroacetate can produce a synergistic effect with LiNO 3 , which can better form a LiF-rich SEI layer.

[0046] Beneficial effects:

[0047] The pyridine trifluoroacetate compound, chlorodifluoroacetate compound and LiNO3 contained in the electrolyte of the present disclosure have the advantages of significantly reducing Li + It plays a role in diffusion energy barrier, promoting dense lithium deposition, improving electrode solution stability and regulating subsequent deposition reactions, thereby greatly protecting the structure of active materials and inhibiting transition metal dissolution, so that lithium metal batteries have excellent cycle performance. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present disclosure clearer, the technical solution of the present disclosure will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. The relevant embodiments described herein are illustrative and are used to provide a basic understanding of the present disclosure. The embodiments of the present disclosure should not be interpreted as limiting the present disclosure.

[0049] the term:

[0050] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0051] In this article, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0052] In the description herein, unless otherwise specified, “above” and “below” include the number.

[0053] Unless otherwise specified, the terms used in this disclosure have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this disclosure can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this disclosure).

[0054] The term "about" is used to describe and illustrate small changes. When used in conjunction with an event or situation, the term may refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very approximately. For example, when used in conjunction with a numerical value, the term may refer to a range of variation of less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. In addition, amounts, ratios, and other numerical values ​​are sometimes presented in this article in a range format. It should be understood that such a range format is for convenience and simplicity, and should be flexibly understood to include not only numerical values ​​explicitly designated as range limits, but also all individual numerical values ​​or subranges encompassed within the range, as if each numerical value and subrange were explicitly designated.

[0055] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0056] The present disclosure is further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present disclosure and are not used to limit the scope of the present disclosure.

[0057] Electrolyte:

[0058] In some embodiments of the present disclosure, the electrolyte provided by the present disclosure comprises a lithium salt, an organic solvent and an additive, wherein the additive comprises a pyridine trifluoroacetate compound represented by the following chemical formula I, a chlorodifluoroacetate compound represented by the following chemical formula II and LiNO3:

[0059]

[0060] R1, R2, R3, R4 and R5 are independently selected from hydrogen, C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl or C 3-8 Epoxyalkyl; the C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl or C 3-8 The alkylene oxide is optionally replaced by one or more C 1-3 Alkyl substituted; R6 is selected from C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl, C 3-8 Epoxyalkyl, C 6-12 Aryl or C 6-12 Heteroaryl, the C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl, C 3-8 Epoxyalkyl, C 6-12 Aryl or C 6-12 The heteroaryl group is optionally substituted with one or more C 1-3 Alkyl substitution.

[0061] In some embodiments of the present disclosure, in the additive, the mass ratio of the pyridine trifluoroacetate to methyl chlorodifluoroacetate is selected from 1:(0.3-2.1).

[0062] In some preferred embodiments of the present disclosure, in the additive, the mass ratio of the pyridine trifluoroacetate to methyl chlorodifluoroacetate can be selected from 1:(1 / 3), 1:0.5, 1:(2 / 3), 1:0.75, 1:1, 1:1.5, 1:2; but not limited thereto.

[0063] In some embodiments of the present disclosure, in the additive, the mass ratio of the pyridine trifluoroacetate, methyl chlorodifluoroacetate and LiNO3 is selected from 1:(0.3-2.1):(0.06-0.7).

[0064] In some preferred embodiments of the present disclosure, in the additive, the mass ratio of pyridine trifluoroacetate, methyl chlorodifluoroacetate and LiNO3 can be selected from 1: (1 / 3): (2 / 30), 1: (1 / 3): (2 / 15), 1: (1 / 3): 0.2, 1: 0.5: (1 / 15), 1: 0.5: 0.1, 1: 0.5: (2 / 15), 1: 0.5: 0.2, 1: 0.5: 0.3, 1: ( 2 / 3):(2 / 15), 1:(2 / 3):0.2, 1:0.75:0.1, 1:0.75:0.2, 1:0.75:0.3, 1:1:0.1, 1:1:0.2, 1:1:0.3, 1:1:0.4, 1:1:0.6, 1:1.5:0.2, 1:1.5:0.4, 1:1.5:0.6, 1:2:0.6, 1:2:0.2, 1:2:0.4; but not limited to.

[0065] In some preferred embodiments of the present disclosure, in the additive, the mass ratio of pyridine trifluoroacetate, methyl chlorodifluoroacetate and LiNO3 is selected from 1:(0.3-2):(0.065-0.6).

[0066] In some preferred embodiments of the present disclosure, in the additive, the mass ratio of the pyridine trifluoroacetate, methyl chlorodifluoroacetate and LiNO3 is selected from 1:(0.5-1):(0.2-0.3).

[0067] In some embodiments of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the pyridine trifluoroacetate is selected from 0.1% to 6.2%.

[0068] In some preferred embodiments of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the pyridine trifluoroacetate is selected from 3.5% to 4.5%.

[0069] In some embodiments of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the methyl chlorodifluoroacetate is selected from 1.8% to 4.2%.

[0070] In some preferred embodiments of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the methyl chlorodifluoroacetate is selected from 2% to 4%.

[0071] In some embodiments of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the LiNO 3 is selected from 0.3% to 1.3%.

[0072] In some preferred embodiments of the present disclosure, based on the total mass of the electrolyte, the mass percentage of the LiNO3 is selected from 0.8% to 1.2%.

[0073] In some embodiments of the present disclosure, in the electrolyte, the molar concentration of the lithium salt is selected from 0.3 mol / L-3 mol / L; for example, the molar concentration of the lithium salt can be selected from 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.7 mol / L, 2.8 mol / L, 2.9 mol / L, 3.0 mol / L; but is not limited thereto.

[0074] In some embodiments of the present disclosure, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium dioxalatoborate, 4,5-dicyano-2-trifluoromethylimidazole lithium, lithium difluorophosphate, lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)amide and lithium bis(trifluoromethylsulfonyl)amide.

[0075] In some preferred embodiments of the present disclosure, the lithium salt includes lithium hexafluorophosphate.

[0076] In some embodiments of the present disclosure, the organic solvent includes at least one of a carbonate compound, an ether compound, a carboxylate compound, a sulfoxide compound, and a nitrile compound.

[0077] In some embodiments of the present disclosure, the carbonate compound includes at least one of a cyclic carbonate compound and a chain carbonate compound, the cyclic carbonate compound includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and γ-butyrolactone, and the chain carbonate compound includes dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, and C 1-4 At least one of the carbonate derivatives synthesized from a fatty monoalcohol and carbonic acid.

[0078] In some embodiments of the present disclosure, the ether compound includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, ethylene glycol dimethyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, ethylene glycol bis(propionitrile) ether and polyethylene glycol monomethyl ether.

[0079] In some embodiments of the present disclosure, the carboxylate compound includes at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate and ethyl butyrate.

[0080] In some embodiments of the present disclosure, the sulfoxide compound includes at least one of dimethyl sulfoxide and diethyl sulfoxide.

[0081] In some embodiments of the present disclosure, the nitrile compound includes at least one of acetonitrile, propionitrile, butyronitrile, benzonitrile and malononitrile.

[0082] In some preferred embodiments of the present disclosure, the organic solvent includes ethylene carbonate, propylene carbonate and dimethyl carbonate, but is not limited thereto.

[0083] positive electrode:

[0084] In some embodiments of the present disclosure, the lithium metal battery provided by the present disclosure further includes a positive electrode, and the positive electrode includes a positive electrode collector and a positive electrode active material disposed on the positive electrode collector.

[0085] In some embodiments of the present disclosure, the positive electrode current collector may be selected from one of stainless steel, nickel, aluminum, titanium, carbon, a conductive resin, an aluminum sheet coated with nickel or titanium, and a stainless steel sheet coated with nickel or titanium.

[0086] In some preferred embodiments of the present disclosure, the positive electrode current collector may be made of metal foil or porous metal plate, for example, foil or porous plate of metal such as aluminum, copper, nickel, titanium or silver or alloys thereof, such as aluminum foil.

[0087] In some embodiments of the present disclosure, the positive electrode active material may be various materials suitable for lithium metal batteries; for example, the positive electrode active material may include but is not limited to lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, olivine-structured lithium-containing phosphates, lithium metal fluoride sulfates, lithium metal vanadates, and lithium-free metal oxides, etc. Other conventionally known materials that can be used as battery positive electrode active materials may also be used.

[0088] In some preferred embodiments of the present disclosure, the positive electrode active material may include one or more of lithium cobalt oxide (LCO), nickel cobalt manganese ternary material (NMC) and lithium nickel cobalt aluminum oxide (NCA), but is not limited thereto.

[0089] In some other preferred embodiments of the present disclosure, the positive electrode active material may include lithium manganese oxide (LiMn2O4), but is not limited thereto.

[0090] In some other preferred embodiments of the present disclosure, the positive electrode active material may include lithium iron phosphate (LFP), but is not limited thereto.

[0091] In some other preferred embodiments of the present disclosure, the positive electrode active material may include lithium cobalt sulfate fluoride (LiCoFSO 4 ), but is not limited thereto.

[0092] In some other preferred embodiments of the present disclosure, the positive electrode active material may include lithium nickel vanadate (LiNiVO 4 ), but is not limited thereto.

[0093] In some other preferred embodiments of the present disclosure, the positive electrode active material may contain V2O5 and / or MnO2.

[0094] In some embodiments of the present disclosure, the positive electrode active material also includes a binder, which may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA) and polyvinyl alcohol (PVA), but is not limited thereto.

[0095] In some embodiments of the present disclosure, the positive electrode active material further includes a conductive agent, and the positive electrode conductive agent may be selected from one or more of graphite, acetylene black, conductive fiber, metal powder, and organic conductive polymer.

[0096] In some preferred embodiments of the present disclosure, the graphite may be selected from natural graphite or artificial graphite; the acetylene black may be selected from Ketjen black; the conductive fiber may be selected from carbon fiber or metal fiber; the metal powder may be selected from copper powder or nickel powder; and the organic conductive polymer may be selected from polyphenylene derivatives.

[0097] In some preferred embodiments of the present disclosure, the positive electrode active material is selected from LiNi 0.3 Co 0.3 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.8 Co 0.1 Mn 0.1 One or more of O2, LiCoO2 and LiFePO4.

[0098] In some preferred embodiments of the present disclosure, the positive electrode can be prepared by coating; for example, the positive electrode active material, binder, conductive agent and organic solvent are first mixed in a predetermined ratio, and the organic solvent can be N-methylpyrrolidone (NMP), and the mixture is stirred into a uniform system to obtain a positive electrode slurry; then, the positive electrode slurry is coated on the positive electrode collector, and after drying, rolling and other processes, the positive electrode is obtained.

[0099] negative electrode:

[0100] In some embodiments of the present disclosure, the lithium metal battery provided by the present disclosure further includes a negative electrode, and the negative electrode includes a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector.

[0101] In some embodiments of the present disclosure, the negative electrode current collector may be made of a metal foil or a porous metal plate, for example, a foil or a porous plate made of a metal such as copper, nickel, titanium or iron, or an alloy thereof, such as copper foil.

[0102] In some embodiments of the present disclosure, the negative electrode active material layer involved in the present disclosure includes a lithium-containing metal material, and the lithium-containing metal material includes metallic lithium, a lithium alloy, a lithium-carbon composite material, a lithium metal oxide or a lithium metal nitride.

[0103] In some embodiments of the present disclosure, the lithium alloy includes any one or a combination of two or more of Li-Sn alloy, Li-Sn-O alloy, Li-Mg alloy, Li-B alloy, Li-Al alloy, etc., but is not limited thereto.

[0104] In some embodiments of the present disclosure, the negative electrode active material can be formed on the negative electrode current collector by at least one of mechanical rolling, vapor deposition, and chemical plating, wherein the vapor deposition method can be a physical vapor deposition method; the physical vapor deposition method can be at least one of an evaporation method and a sputtering method, for example, at least one of a vacuum evaporation method, a thermal evaporation method, an electron beam evaporation method, and a magnetron sputtering method.

[0105] In some preferred embodiments of the present disclosure, the negative electrode is obtained by pressing lithium foil on a negative electrode current collector based on copper and cutting; wherein the thickness of the copper substrate is 6-20 μm, preferably 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm; the thickness of the lithium foil is 20-100 μm, preferably 50 μm.

[0106] Diaphragm:

[0107] The material and shape of the separator used in the lithium metal battery and electrochemical device of the present disclosure are not particularly limited, and may be any technology disclosed in the prior art.

[0108] In some embodiments of the present disclosure, the diaphragm involved in the present disclosure can be any known porous structure isolation membrane with electrochemical stability and chemical stability, such as a single-layer or multi-layer film of one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

[0109] Lithium Metal Batteries:

[0110] In some embodiments of the present disclosure, the lithium metal battery involved in the present disclosure includes the above-mentioned positive electrode, negative electrode, separator, electrolyte, etc., but is not limited thereto.

[0111] In some embodiments of the present disclosure, the positive electrode and the negative electrode are alternately stacked, and an isolation membrane is provided between the positive electrode and the negative electrode to isolate the positive electrode and the negative electrode, thereby obtaining a battery cell, or the battery cell can be obtained by winding; the battery cell is placed in a casing, an electrolyte is injected, and the casing is sealed to obtain the aforementioned lithium metal battery.

[0112] In some embodiments of the present disclosure, the lithium metal battery involved in the present disclosure may include an outer packaging, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0113] In some embodiments of the present disclosure, the present disclosure further provides a battery module. The battery module includes the above-mentioned lithium metal battery. The battery module of the present disclosure uses the above-mentioned lithium metal battery, and therefore has at least the same advantages as the lithium metal battery. The number of lithium metal batteries contained in the battery module of the present disclosure can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0114] In some embodiments of the present disclosure, the present disclosure further provides a battery pack, which includes the above-mentioned battery module. The number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0115] Device:

[0116] The present disclosure also provides a device comprising at least one of the above-mentioned lithium metal battery, battery module or battery pack.

[0117] In some embodiments of the present disclosure, the device includes, but is not limited to: electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, etc. In order to meet the device's requirements for high power and high energy density of lithium metal batteries, a battery pack or battery module can be used.

[0118] The present disclosure is further described below in conjunction with the examples. It should be understood that these examples are only used to illustrate the present disclosure and are not used to limit the scope of the present disclosure.

[0119] Examples and Comparative Examples

[0120] Test method:

[0121] Cycle capacity retention test:

[0122] At room temperature (25°C), the prepared lithium metal battery was charged to 4.2V at 1C constant current and constant voltage, and then switched to constant voltage charging. The charging cutoff current was 0.05C. After the battery was allowed to stand for 30 minutes, it was discharged at a cross-current rate of 1C to a lower limit voltage of 3.0V. The lithium metal battery was charged and discharged 500 times in the above manner to obtain the 200th cycle discharge capacity, and the 200-cycle capacity retention rate = 200th cycle discharge capacity / 1st cycle discharge capacity.

[0123] Embodiment 1:

[0124] Embodiment 1 comprises the following steps:

[0125] (1) Preparation of electrolyte:

[0126] Ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC) are mixed in a mass ratio of 2:1:5, and then lithium hexafluorophosphate is added thereto until the concentration of lithium hexafluorophosphate reaches 1.0 mol / L, and then an additive is added, the additive comprising pyridine trifluoroacetate, LiNO3 and methyl chlorodifluoroacetate. Based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 0.4%, the content of methyl chlorodifluoroacetate is 2%, and the content of lithium salt in the electrolyte is 12.5%.

[0127] (2) Preparation of positive electrode:

[0128] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent acetylene black and multi-walled carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are dissolved in a solvent N-methylpyrrolidone (NMP) in a weight ratio of 95:2:1:2, and the positive electrode slurry is obtained after sufficient homogenization and mixing; the positive electrode slurry is then evenly coated on the positive electrode current collector aluminum foil, and then baked, cold pressed, and die-cut to obtain the positive electrode.

[0129] (3) Preparation of negative electrode:

[0130] The lithium foil and the copper foil are cold pressed to obtain the negative electrode sheet, and the negative electrode is obtained after slitting and die cutting.

[0131] (4) Preparation of lithium metal batteries:

[0132] The negative electrode, separator (polyethylene (PE) porous polymer film) and positive electrode obtained above are stacked in sequence, so that the separator is between the positive and negative electrodes to play the role of electronic insulation. The stacking is used to make a battery cell. After baking, the aluminum-plastic film is punched and the battery cell is placed in the pit. After packaging and liquid injection, a lithium metal battery is obtained.

[0133] (5) Lithium metal battery formation steps:

[0134] The first charging formation step of Example 1 is as follows: charging at a constant current of 0.05C for 120 minutes, standing for 5 minutes, charging at a constant current of 0.1C for 1 hour, standing for 5 minutes, then charging at a constant current of 0.2C for 2 hours, standing for 5 minutes, and finally discharging at a constant current of 0.2C for 1.5 hours to complete the formation; the formed battery is evacuated and then repackaged to obtain a soft-pack lithium metal battery.

[0135] Embodiment 2:

[0136] The steps of Example 2 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 0.4%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0137] Embodiment 3:

[0138] The steps of Example 3 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 0.4%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0139] Embodiment 4:

[0140] The steps of Example 4 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 2%.

[0141] Embodiment 5:

[0142] The steps of Example 5 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0143] Embodiment 6:

[0144] The steps of Example 6 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0145] Embodiment 7:

[0146] The steps of Example 7 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 2%.

[0147] Embodiment 8:

[0148] The steps of Example 8 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0149] Embodiment 9:

[0150] The steps of Example 9 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 2%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0151] Embodiment 10:

[0152] The steps of Example 10 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 0.4%, and the mass percentage content of methyl chlorodifluoroacetate is 2%.

[0153] Embodiment 11:

[0154] The steps of Example 11 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 0.4%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0155] Embodiment 12:

[0156] The steps of Example 12 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 0.4%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0157] Embodiment 13:

[0158] The steps of Example 13 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 2%.

[0159] Embodiment 14:

[0160] The steps of Example 14 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0161] Embodiment 15:

[0162] The steps of Example 15 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0163] Embodiment 16:

[0164] The steps of Example 16 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 2%.

[0165] Embodiment 17:

[0166] The steps of Example 17 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0167] Embodiment 18:

[0168] The steps of Example 18 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0169] Embodiment 19:

[0170] The steps of Example 19 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 0.4%, and the mass percentage content of methyl chlorodifluoroacetate is 2%.

[0171] Embodiment 20:

[0172] The steps of Example 20 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 0.4%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0173] Embodiment 21:

[0174] The steps of Example 21 are the same as those of Example 1, except that, in the preparation of the electrolyte: among the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 0.4%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0175] Embodiment 22:

[0176] The steps of Example 22 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 2%.

[0177] Embodiment 23:

[0178] The steps of Example 23 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0179] Embodiment 24:

[0180] The steps of Example 24 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 0.8%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0181] Embodiment 25:

[0182] The steps of Example 25 are the same as those of Example 1, except that, in the preparation of the electrolyte: among the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 2%.

[0183] Embodiment 26:

[0184] The steps of Example 26 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 3%.

[0185] Embodiment 27:

[0186] The steps of Example 27 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additives, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 6%, the mass percentage content of LiNO3 is 1.2%, and the mass percentage content of methyl chlorodifluoroacetate is 4%.

[0187] Comparative Example 1:

[0188] The steps of Comparative Example 1 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additive, based on the total weight of the electrolyte, the mass percentage content of LiNO3 is 0.8%, the content of methyl chlorodifluoroacetate is 3%, and the additive does not contain pyridine trifluoroacetate.

[0189] Comparative Example 2:

[0190] The steps of Comparative Example 2 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additive, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the content of methyl chlorodifluoroacetate is 3%, and the additive does not contain LiNO3.

[0191] Comparative Example 3:

[0192] The steps of Comparative Example 3 are the same as those of Example 1, except that, in the preparation of the electrolyte: in the additive, based on the total weight of the electrolyte, the mass percentage of pyridine trifluoroacetate is 4%, the mass percentage content of LiNO3 is 0.8%, and the additive does not contain methyl chlorodifluoroacetate.

[0193] Comparative Example 4:

[0194] The steps of Comparative Example 4 are the same as those of Example 1, except that no additive is added in the preparation of the electrolyte.

[0195] Electrochemical testing:

[0196] The lithium metal batteries of Examples 1-27 and Comparative Examples 1-4 were subjected to electrochemical tests, and the obtained data are shown in Table 1.

[0197] [Table 1]

[0198]

[0199]

[0200]

[0201] Wherein, “-” indicates that the corresponding compound does not exist.

[0202] It can be seen that the cycle performance of Examples 1-27 is better than that of Comparative Examples 1-4. This is because pyridinium trifluoroacetate is introduced into the electrolyte as an additive, which is easily soluble in carbonate electrolytes and has better compatibility with lithium metal. Thanks to the strong coordination between the carbonyl group (C=O) and lithium, the trifluoroacetic acid anion promotes the dissolution of LiNO3 in the carbonate electrolyte, forming an anion-rich solvation environment, reducing the Li+ desolvation energy barrier, and at the same time, under the joint action of methyl chlorodifluoroacetate, a LiF-rich SEI layer is formed. In addition, due to electrostatic interactions, pyridinium cations can be adsorbed on the negatively charged lithium metal surface and preferentially reduced, regulating subsequent deposition behavior. The use of this electrolyte can significantly reduce Li + The diffusion energy barrier promotes dense lithium deposition, thereby forming a uniform and dense CEI film on the surface of the positive electrode, which greatly protects the structure of the positive electrode material, and the dissolution of the transition metal is inhibited, thereby having excellent cycle performance. From Examples 1-27, it can be found that when the mass percentage of pyridine trifluoroacetate is about 4%, the mass percentage content of LiNO3 is about 0.8%, and the content of methyl chlorodifluoroacetate is about 3%, the cycle performance is optimal, and the capacity retention rate is 96.5%. It can be seen from Comparative Examples 1, 2 and 3 that the three additives need to cooperate with each other to effectively improve the cycle performance. It can be seen from the cycle data of Comparative Example 4 that the cycle performance of the lithium metal battery in the comparative example without adding any additives is very poor.

[0203] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present disclosure, and that changes, substitutions and modifications may be made to the embodiments without departing from the spirit, principles and scope of the present disclosure.

Claims

1. An electrolyte, characterized in that: The electrolyte comprises a lithium salt, an organic solvent and an additive, wherein the additive comprises a pyridine trifluoroacetate compound represented by the following chemical formula I, a chlorodifluoroacetate compound represented by the following chemical formula II and LiNO3: R1, R2, R3, R4 and R5 are independently selected from hydrogen, C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl or C 3-8 Epoxyalkyl; the C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl or C 3-8 The alkylene oxide is optionally replaced by one or more C 1-3 Alkyl substitution; R6 is selected from C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl, C 3-8 Epoxyalkyl, C 6-12 Aryl or C 6-12 Heteroaryl, the C 1-11 Alkyl, C 1-8 Alkoxy, C 2-6 Alkenyl, C 2-6 Alkenyloxy, C 2-6 Alkynyl, C 2-6 Alkynyloxy, C 3-8 Cycloalkyl, C 3-8 Epoxyalkyl, C 6-12 Aryl or C 6-12 The heteroaryl group is optionally substituted with one or more C 1-3 Alkyl substitution.

2. The electrolyte according to claim 1, wherein The mass ratio of the pyridine trifluoroacetate compound to the chlorodifluoroacetate compound is selected from 1:(0.3-2.1).

3. The electrolyte according to claim 1, characterized in that In the additive, the mass ratio of the pyridine trifluoroacetate compound, the chlorodifluoroacetate compound and LiNO3 is selected from 1:(0.3-2.1):(0.06-0.7).

4. The electrolyte according to claim 3, characterized in that In the additive, the mass ratio of the pyridine trifluoroacetate compound, the chlorodifluoroacetate compound and LiNO3 is selected from 1:(0.5-1):(0.2-0.3).

5. The electrolyte according to claim 1, characterized in that The pyridine trifluoroacetate compound is selected from the following compound IA, and the chlorodifluoroacetate compound is selected from the following compound II-A:

6. The electrolyte according to claim 1, characterized in that Based on the total mass of the electrolyte, the mass percentage of the pyridine trifluoroacetate compound is selected from 0.1%-6.2%; and / or Based on the total mass of the electrolyte, the mass percentage of the chlorodifluoroacetate compound is selected from 1.8%-4.2%; and / or Based on the total mass of the electrolyte, the mass percentage of the LiNO3 is selected from 0.3%-1.3%.

7. The electrolyte according to claim 6, characterized in that Based on the total mass of the electrolyte, the mass percentage of the pyridine trifluoroacetate compound is selected from 3.5%-4.5%; and / or Based on the total mass of the electrolyte, the mass percentage of the chlorodifluoroacetate compound is selected from 2%-4%; and / or Based on the total mass of the electrolyte, the mass percentage of the LiNO3 is selected from 0.8%-1.2%.

8. The electrolyte according to claim 1, characterized in that The lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium dioxalatoborate, 4,5-dicyano-2-trifluoromethylimidazolium lithium, lithium difluorophosphate, lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)amide and lithium bis(trifluoromethylsulfonyl)amide; and / or The organic solvent includes at least one of a carbonate compound, an ether compound, a carboxylate compound, a sulfoxide compound and a nitrile compound.

9. A secondary battery, characterized in that: The secondary battery comprises the electrolyte according to any one of claims 1 to 8.

10. A device, characterized in that: The device comprises the secondary battery according to claim 9.

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