Electrolyte, electrochemical device, and electronic device

Abstract

The application provides an electrolyte, an electrochemical device and an electronic device. The electrolyte comprises a compound represented by formula I-A; wherein A 1 , A 2 , A 3 are each independently selected from formula I-B or formula I-C, A 1 , A 2 , A 3 at least two of which are formula I-C; in formula I-A, n is an integer selected from 1 to 10, and m is selected from 0 or 1; in formula I-B, formula I-C, represents a site at which two adjacent atoms are connected. The electrolyte can significantly improve the high-temperature storage performance, cycle performance and floating performance of the electrochemical device.

Description

[0001] This application is a divisional application of the original international application that entered the Chinese national phase (international application number PCT / CN2020 / 138741, international application date December 23, 2020, invention title "electrolyte, electrochemical device and electronic device", Chinese national phase entry date November 30, 2021, national application number 202080040377.3, invention title "electrolyte, electrochemical device and electronic device"). Technical Field

[0002] This application relates to the field of electrochemistry, specifically to an electrolyte, an electrochemical device, and an electronic device. Background Technology

[0003] Electrochemical devices (such as lithium-ion batteries) have attracted widespread attention and are therefore widely used due to their high energy density, high power density, and stable lifespan. With rapid technological advancements, diversified market demands, and the rise of energy storage systems and electric vehicles in the coming years, even greater requirements are being placed on lithium-ion batteries, such as thinner, lighter, more diverse form factors, higher safety, and higher energy density. Summary of the Invention

[0004] In some embodiments, this application provides an electrolyte comprising a compound represented by formula IA;

[0005]

[0006] Among them, A 1 A 2 A 3 Each is independently selected from form IB or form IC, A 1 A 2 A 3 At least two of them are ICs;

[0007]

[0008] In formula IA, n is selected from integers from 1 to 10, and m is selected from 0 or 1; in formulas IB and IC, Indicates the site where two adjacent atoms are connected; R 11 R 13 Each is independently selected from substituted or unsubstituted C1-C. 10 Alkylene, substituted or unsubstituted C2-C 10 alkenyl groups, substituted or unsubstituted C2-C 10 alkyne group, substituted or unsubstituted C3-C 10Allenyl, substituted or unsubstituted C6-C 10 aryl, substituted or unsubstituted C3-C 10 alicyclic hydrocarbon group; when substituted, the substituents include halogens; R 12 Each is independently selected from halogens, substituted or unsubstituted C1-C. 10 Alkyl groups, substituted or unsubstituted C2-C 10 alkenyl, substituted or unsubstituted C2-C 10 Alkyne group, substituted or unsubstituted C3-C 10 Alkenyl, substituted or unsubstituted C6-C 10 aryl, substituted or unsubstituted C3-C 10 The alicyclic hydrocarbon group; when substituted, the substituents include halogens.

[0009] In some embodiments, the compound represented by formula IA includes at least one of the compounds represented by formulas (I-1) to (I-30):

[0010]

[0011]

[0012]

[0013] In some embodiments, the mass percentage of the compound represented by Formula IA is from 0.01% to 10% based on the mass of the electrolyte.

[0014] In some embodiments, the electrolyte further includes at least one of the following: compounds represented by formula II–A, formula III–A, formula IV–A, formula VA, formula VB, or polynitrile compounds.

[0015]

[0016] Among them, R 21 R 22 Each is independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, or substituted or unsubstituted C2-C5 alkynyl groups, wherein, when substituted, the substituents include halogens; R 21 R 22 They can bond together to form a ring structure;

[0017]

[0018] Among them, A 31 A 32 A 33 A34 Each is independently selected from one of halogens, formula III-X, formula III-Y, and formula III-Z, and when formula III-Y is selected, A 31 A 32 A 33 A 34 Two or four of them are selected from formula III-Y to form a ring structure;

[0019]

[0020]

[0021] Among them, R 31 R 33 Each is independently selected from substituted or unsubstituted C1-C6 alkyl groups and substituted or unsubstituted C2-C6 alkenyl groups; R 32 Each is independently selected from substituted or unsubstituted C1-C6 alkylene groups and substituted or unsubstituted C2-C6 alkenyl groups; when substituted, the substituents include halogens; This indicates the site where two adjacent atoms are connected; in formula III-Y, the O atom is connected to the B atom in formula III-A, and k is 0 or 1;

[0022]

[0023] in, Indicates a single or double bond, where x and y independently represent 0 or 1; when one of the bonds in equation IV-A... When representing a single bond, one of x and y is 1, and the other of x and y is 0; when both in equation IV-A When both represent single bonds, then x and y are both 1; when both in equation IV-A When both represent double bonds, then x and y are both 0; A 42 A 43 A 45 A 46 Each is independently selected from halogens, substituted or unsubstituted C1-C6 alkyl groups, formula IV-B, formula IV-C, and formula IV-D, and when formula IV-C is selected, A 42 A 43 A 45 A 46 Two or four of them are selected from formula IV-C to form a ring structure; A 41 A 44 Each is independently selected from oxygen, halogen, substituted or unsubstituted C1-C6 alkyl groups, formula IV-B, formula IV-C, and formula IV-D, and when formula IV-C is selected, A 41 A 44All are selected from formula IV-C to form a cyclic structure; wherein, when substituted, the substituents include halogens; A 41 A 42 A 43 A 44 A 45 A 46 Not all of it is fluorine;

[0024]

[0025] In formulas IV-B, IV-C, and IV-D, R 41 R 43 Each is independently selected from substituted or unsubstituted C1-C6 alkyl groups and substituted or unsubstituted C2-C6 alkenyl groups; R 42 Selected from substituted or unsubstituted C1-C6 alkylene groups and substituted or unsubstituted C2-C6 alkenyl groups; wherein, when substituted, the substituents include halogens; in formula IV-C, the O atom is attached to the P atom in formula IV-A, and z represents 0 or 1;

[0026]

[0027] Among them, R 51 R 52 R 53 R 54 Each is independently selected from substituted or unsubstituted C1-C5 alkyl groups, substituted or unsubstituted C2-C5 alkyl groups. 10 alkenyl, substituted or unsubstituted C2-C 10 Alkyne group, substituted or unsubstituted C3-C 10 Alicyclic groups, substituted or unsubstituted C6-C 10 The aryl group, substituted or unsubstituted C1-C6 alicyclic group, substituted or unsubstituted C1-C6 aromatic heterocyclic group, substituted or unsubstituted C1-C6 heteroatom-containing functional group; wherein, when substituted, the substituent includes halogen, R 51 R 52 They can bond together to form a ring structure; R 53 R 54 They can bond together to form a ring structure; the heteroatoms in the heteroatom functional groups include at least one of B, N, O, Si, P and S.

[0028] In some embodiments, the electrolyte satisfies at least one of the following conditions: a) the mass percentage of the compound represented by formula II-A is 0.01% to 10% based on the mass of the electrolyte; b) the mass percentage of the compound represented by formula III-A is 0.1% to 5% based on the mass of the electrolyte; c) the mass percentage of the compound represented by formula IV-A is 0.1% to 5% based on the mass of the electrolyte; d) the sum of the mass percentages of the compounds represented by formulas VA and VB is 0.01% to 10% based on the mass of the electrolyte; e) the mass percentage of the polynitrile compound is 0.1% to 10% based on the mass of the electrolyte.

[0029] In some embodiments, the compound represented by formula II–A includes at least one of the compounds represented by formulas (II-1) to (II-22):

[0030]

[0031] In some embodiments, the compound represented by Formula III-A includes at least one of lithium tetrafluoroborate, lithium dioxalate borate, and lithium difluorooxalate borate.

[0032] In some embodiments, the compound represented by formula IV-A includes at least one of lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0033] In some embodiments, the compound represented by formula VA includes at least one of the compounds represented by formulas (V-1) to (V-16):

[0034]

[0035]

[0036] The compound represented by formula VB includes at least one of the following compounds represented by formulas (V-17) to (V-20):

[0037]

[0038] In some embodiments, the polynitrile compound includes at least one selected from 1,2,3-tris(2-cyanoethoxy)propane, 1,3,6-hexanetrionitrile, 1,2-di(2-cyanoethoxy)ethane, and adiponitrile.

[0039] In some embodiments, this application also provides an electrochemical device, which includes a positive electrode, a negative electrode, a separator, and the electrolyte of this application.

[0040] In some embodiments, this application also provides an electronic device that includes the electrochemical device of this application.

[0041] The electrolyte of this application can significantly improve the high-temperature storage performance, cycle performance and float charge performance of electrochemical devices using it. Detailed Implementation

[0042] It should be understood that the disclosed embodiments are merely examples of this application, and this application can be implemented in various forms. Therefore, the specific details disclosed herein should not be construed as limiting, but are only intended to serve as the basis for the claims and as an illustrative basis for teaching those skilled in the art to implement this application in various ways.

[0043] In the description of this application, unless otherwise expressly specified and limited, the terms "Additive A," "Additive B," "Additive C," "Additive D," "Additive E," "Additive F," etc., are used for illustrative purposes only and should not be construed as indicating or implying relative importance or interrelationship. In the description of this application, unless otherwise expressly specified and limited, the letters and numbers in the terms "Formula IA," "Formula IB," "Formula I-1," "Formula II-A," "Formula II-B," "Formula II-1," etc., are used for labeling purposes only and should not be construed as indicating or implying relative importance, interrelationship, or chemical elements.

[0044] In the description of this application, unless otherwise stated, the functional groups of all compounds may be substituted or unsubstituted.

[0045] In this application, unless otherwise stated, the term "heteroatom" refers to an atom other than C and H. In some embodiments, a heteroatom includes at least one of B, N, O, Si, P, and S. In this application, the term "heteroatom-containing functional group" refers to a functional group containing at least one heteroatom. In this application, the term "heterocyclic group" refers to a cyclic group containing at least one heteroatom. In some embodiments, a heterocyclic group includes at least one of alicyclic and aromatic heterocyclic groups.

[0046] In the description of this application, the term "alicyclic hydrocarbon group" refers to a cyclic hydrocarbon with aliphatic properties, the molecule of which contains a closed carbon ring.

[0047] In this application's description, alkylene is a divalent group formed by the loss of one hydrogen atom from an alkyl group, alkenylene is a divalent group formed by the loss of one hydrogen atom from an alkenyl group, ynylene is a divalent group formed by the loss of one hydrogen atom from an ynyl group, alkoxyene is a divalent group formed by the loss of one hydrogen atom from an alkoxy group, and arylene is a divalent group formed by the loss of one hydrogen atom from an aryl group. Subunit structures not explicitly stated in this application's description are to be interpreted according to the description in this paragraph.

[0048] In the description of this application, the atenyl group represents a group in which two double bonds share a single carbon atom, and the structural formula of the atenyl group is as follows:

[0049] In the description of this application, any terms not explicitly stated, substitutions in structural formulas, etc., should be understood in accordance with the well-known, conventional, and customary means or methods of those skilled in the art.

[0050] The electrolyte, electrochemical device, and electronic device of this application are described in detail below.

[0051] Electrolyte

[0052] Additive A

[0053] In some embodiments, the electrolyte contains additive A, which is at least one of the compounds represented by formula (IA).

[0054]

[0055] Among them, A 1 A 2 A 3 Each is independently selected from form IB or form IC, A 1 A 2 A 3 At least two of them are ICs;

[0056]

[0057] In equation (IA), n is selected from integers from 1 to 10, and m is selected from 0 or 1; in equations (IB) and (IC), Indicates the site where two adjacent atoms are connected; R 11 R 13 Each is independently selected from substituted or unsubstituted C1-C. 10 Alkylene, substituted or unsubstituted C2-C 10 alkenyl groups, substituted or unsubstituted C2-C 10 alkyne group, substituted or unsubstituted C3-C 10 Allenyl, substituted or unsubstituted C6-C 10 aryl, substituted or unsubstituted C3-C 10 alicyclic hydrocarbon group; when substituted, the substituents include halogens; R 12 Each is independently selected from halogens, substituted or unsubstituted C1-C. 10 Alkyl groups, substituted or unsubstituted C2-C 10 alkenyl, substituted or unsubstituted C2-C 10 Alkyne group, substituted or unsubstituted C3-C 10 Alkenyl, substituted or unsubstituted C6-C 10aryl, substituted or unsubstituted C3-C 10 The alicyclic hydrocarbon group; when substituted, the substituents include halogens.

[0058] In the electrolyte of this application, additive A is a phosphono-oxygen polycyano functional group compound. The cyano (-CN) functional group in its structure can form a complex with the transition metal in the positive electrode active material of the electrochemical device, stabilizing the transition metal on the surface of the positive electrode active material. Simultaneously, due to the presence of the phosphono-oxygen functional group in the molecule, it can enhance the antioxidant properties of the complex formed by the transition metal, effectively inhibiting the continuous decomposition of the electrolyte and suppressing high-temperature gas generation. Therefore, this electrolyte can significantly improve the high-temperature storage performance, cycle performance, and float charge performance of the electrochemical device.

[0059] In some embodiments, additive A comprises at least one of compounds represented by formula (I-1) to (I-30);

[0060]

[0061]

[0062]

[0063] In some embodiments, the mass percentage of additive A in the electrolyte is 0.01% to 10% based on the mass of the electrolyte. In some embodiments, the mass percentage of additive A may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0%, 7.0%, 8.0%, or 9.0% based on the mass of the electrolyte.

[0064] Additive B

[0065] In some embodiments, the electrolyte may further contain additive B, which is at least one of the compounds represented by formula (II-A);

[0066]

[0067] Among them, R 21 R 22 Each is independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, or substituted or unsubstituted C2-C5 alkynyl groups, wherein, when substituted, the substituents include halogens; R 21 R 22 They can bond together to form a ring structure.

[0068] Additive B is a carboxylic anhydride compound. When additives A and B are added to the electrolyte at the same time, the high-temperature storage performance of the electrochemical device can be further improved. The possible reason is that carboxylic anhydrides can form a film on the surface of the positive and negative electrode active materials, and can also neutralize the alkalinity of the active material on the positive electrode surface, further inhibiting electrolyte decomposition and reducing gas production, thereby improving high-temperature storage performance.

[0069] In some embodiments, additive B comprises at least one of the compounds represented by formulas (II-1) to (II-22);

[0070]

[0071]

[0072] In some embodiments, the mass percentage of additive B in the electrolyte is 0.01% to 10% based on the mass of the electrolyte. In some embodiments, the mass percentage of additive B may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0%, 7.0%, 8.0%, or 9.0% based on the mass of the electrolyte.

[0073] <Additive C>

[0074] In some embodiments, the electrolyte may further contain additive C, wherein additive C is at least one of the compounds represented by formula (III-A);

[0075]

[0076] Among them, A 31 A 32 A 33 A 34 Each is independently selected from one of halogens, formula (III-X), formula (III-Y), and formula (III-Z), and when formula (III-Y) is selected, A 31 A 32 A 33 A 34 Two or four of them are selected from formula (III-Y) to form a ring structure;

[0077]

[0078] Among them, R 31 R 33 Each is independently selected from substituted or unsubstituted C1-C6 alkyl groups and substituted or unsubstituted C2-C6 alkenyl groups; R 32Each is independently selected from substituted or unsubstituted C1-C6 alkylene groups and substituted or unsubstituted C2-C6 alkenyl groups; when substituted, the substituents include halogens; This indicates the site where two adjacent atoms are connected; in formula (III-Y), the O atom is connected to the B atom in formula (III-A), and k is 0 or 1.

[0079] Additive C is a boron-based lithium salt compound. When additives A and C are added to the electrolyte simultaneously, the high-temperature storage performance of the electrochemical device can be further improved. The possible reason is that the boron-based lithium salt compound can form a stable interfacial film on the surface of the positive electrode active material, further reducing the contact between the positive electrode and the electrolyte, reducing electrolyte decomposition, and thus further improving the high-temperature storage performance.

[0080] In some embodiments, additive C comprises at least one of lithium tetrafluoroborate (LiBF4), lithium dioxalate borate (LiBOB), and lithium difluorooxalate borate (LiDFOB).

[0081] In some embodiments, the mass percentage of additive C in the electrolyte is 0.1% to 5% based on the mass of the electrolyte. In some embodiments, the mass percentage of additive C in the electrolyte may be 0.2%, 0.3%, 0.5%, 1%, 2%, or 3% based on the mass of the electrolyte.

[0082] <Additive D>

[0083] In some embodiments, the electrolyte may further contain additive D, which is at least one of the compounds represented by formula (IV-A);

[0084]

[0085] in, Indicates a single or double bond, where x and y independently represent 0 or 1; when one of the elements in equation (IV-A) When representing a single bond, one of x and y is 1, and the other of x and y is 0; when both in equation (IV-A) are... When both represent single bonds, then x and y are both 1; when both in equation (IV-A) represent double bonds, then x and y are both 0; A 42 A 43 A 45 A 46 Each is independently selected from halogens, substituted or unsubstituted C1-C6 alkyl groups, formula (IV-B), formula (IV-C), and formula (IV-D), and when formula (IV-C) is selected, A 42 A 43 A 45 A 46Two or four of them are selected from formula (IV-C) to form a ring structure; A 41 A 44 Each is independently selected from oxygen, halogen, substituted or unsubstituted C1-C6 alkyl groups, formula (IV-B), formula (IV-C), and formula (IV-D), and when formula (IV-C) is selected, A 41 A 44 All are selected from formula (IV-C) to form a cyclic structure; wherein, when substituted, the substituents include halogens; A 41 A 42 A 43 A 44 A 45 A 46 Not all of it is fluorine;

[0086]

[0087] In equations (IV-B), (IV-C), and (IV-D), R 41 R 43 Each is independently selected from substituted or unsubstituted C1-C6 alkyl groups and substituted or unsubstituted C2-C6 alkenyl groups; R 42 Selected from substituted or unsubstituted C1-C6 alkylene groups and substituted or unsubstituted C2-C6 alkenyl groups; wherein, when substituted, the substituents include halogens; in formula (IV-C), the O atom is attached to the P atom in formula (IV-A), and z represents 0 or 1.

[0088] Additive D is a phosphorus-based lithium salt compound. When additives A and D are added to the electrolyte at the same time, the high-temperature storage performance of the electrochemical device can be further improved. The possible reason is that phosphorus-based lithium salt compounds can form an interfacial film on the surface of the positive electrode active material. Moreover, the interfacial film containing phosphorus-based lithium salt compounds has high antioxidant properties, which can further inhibit the oxidative decomposition of the electrolyte and reduce gas production, thereby further improving the high-temperature storage performance.

[0089] In some embodiments, additive D comprises at least one of lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalate) phosphate (LiDFOP), and lithium tetrafluoro(oxalate) phosphate (LiTFOP).

[0090] In some embodiments, the fourth additive has a mass percentage content of 0.1%-5% in the electrolyte, based on the mass of the electrolyte. In some embodiments, the additive D has a mass percentage content of 0.2%, 0.3%, 0.5%, 1%, 2%, or 3% in the electrolyte, based on the mass of the electrolyte.

[0091] <Additive E>

[0092] In some embodiments, the electrolyte may also contain additive E, which is at least one of the compounds represented by formula (VA) or formula (VB);

[0093]

[0094] Among them, R 51 R 52 R 53 R 54 Each is independently selected from substituted or unsubstituted C1-C5 alkyl groups, substituted or unsubstituted C2-C5 alkyl groups. 10 alkenyl, substituted or unsubstituted C2-C 10 Alkyne group, substituted or unsubstituted C3-C 10 Alicyclic groups, substituted or unsubstituted C6-C 10 The aryl group, substituted or unsubstituted C1-C6 alicyclic group, substituted or unsubstituted C1-C6 aromatic heterocyclic group, substituted or unsubstituted C1-C6 heteroatom-containing functional group; wherein, when substituted, the substituent includes halogen, R 51 R 52 They can bond together to form a ring structure; R 53 R 54 They can bond together to form a ring structure; the heteroatoms in the functional groups containing heteroatoms include at least one of B, N, O, Si, P and S.

[0095] Additive E is a compound containing sulfur-oxygen double bond functional groups. On the one hand, compounds containing sulfur-oxygen double bonds have strong antioxidant capacity, making the electrolyte less susceptible to oxidation on the surface of the positive electrode active material. On the other hand, compounds containing sulfur-oxygen double bond functional groups can form a film on the surface of the negative electrode active material, further enhancing the protection of the active material.

[0096] In some embodiments, the compound represented by formula (VA) comprises at least one of the compounds represented by formulas (V-1) to (V-16);

[0097]

[0098] In some embodiments, the compound represented by formula (VB) comprises at least one of the compounds represented by formulas (V-17) to (V-20):

[0099]

[0100] In some embodiments, the mass percentage of additive E in the electrolyte is 0.01% to 10%, preferably 0.1% to 8%, based on the mass of the electrolyte. In some embodiments, the mass percentage of additive E in the electrolyte may be 0.02%, 0.05%, 0.2%, 0.3%, 0.4%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0%, 7.0%, or 9.0%, based on the mass of the electrolyte.

[0101] <Additive F>

[0102] In some embodiments, the electrolyte may further contain additive F. Additive F is a polynitrile compound, and in some embodiments, the polynitrile compound includes at least one selected from 1,2,3-tris(2-cyanoethoxy)propane, 1,3,6-hexanetrionitrile, 1,2-di(2-cyanoethoxy)ethane, and adiponitrile.

[0103] When additives A and F are added to the electrolyte simultaneously, the high-temperature storage performance and cycle performance of the electrochemical device can be further improved. This is likely because excessive addition of additive A can lead to excessively high electrolyte viscosity, affecting the kinetic performance of the electrochemical device and causing deterioration in cycle performance. Adding additive F effectively avoids excessive electrolyte viscosity and enhances the stability of the positive electrode active material, further reducing electrolyte decomposition, thereby improving the high-temperature storage performance and cycle performance of the electrochemical device.

[0104] In some embodiments, the mass percentage of additive F in the electrolyte is 0.1% to 10%, preferably 0.5% to 5%, based on the mass of the electrolyte. In some embodiments, the mass percentage of additive F in the electrolyte may be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0%, 7.0%, or 9.0%, based on the mass of the electrolyte.

[0105] In some embodiments, when additive A and additive F are added to the electrolyte simultaneously, the mass fraction ratio of additive A to additive F is 0.01-1.

[0106] Regarding the additives mentioned above in this application, when the electrolyte contains additive A, at least one of additives B, C, D, E, and F may also be added. The combined use of additive A and other additives in the electrolyte can further improve the electrochemical performance of the electrochemical device.

[0107] <Organic solvents>

[0108] In some embodiments, the electrolyte further comprises an organic solvent. The organic solvent is an organic solvent known in the art suitable for electrochemical devices, such as a non-aqueous organic solvent. In some embodiments, the non-aqueous organic solvent comprises at least one of carbonate solvents, carboxylic acid ester solvents, ether solvents, sulfone solvents, or other aprotic solvents.

[0109] In some embodiments, the carbonate solvent comprises at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, and butene carbonate.

[0110] In some embodiments, the carboxylic acid ester solvent comprises at least one of methyl formate, ethyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, 2,2-difluoroethyl acetate, ethyl 2,2-difluoroethyl acetate, γ-butyrolactone, valerate, and butyrolactone.

[0111] In some embodiments, the ether solvent comprises at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran.

[0112] In some embodiments, the sulfone solvent comprises at least one of ethyl vinyl sulfone, methyl isopropyl sulfone, isopropyl sec-butyl sulfone, and sulfolane.

[0113] In this application, the organic solvent in the electrolyte can be a single non-aqueous organic solvent or a mixture of multiple non-aqueous organic solvents. When a mixed solvent is used, electrochemical devices with different performance can be obtained by controlling the mixing ratio.

[0114] <Electrolyte salts>

[0115] In some embodiments, the electrolyte further comprises an electrolyte salt. The electrolyte salt is a suitable electrolyte salt for electrochemical devices, as known in the art. A suitable electrolyte salt can be selected for different electrochemical devices. For example, for lithium-ion batteries, lithium salts are typically used as the electrolyte salt.

[0116] In some embodiments, the lithium salt comprises at least one of an organic lithium salt or an inorganic lithium salt.

[0117] In some embodiments, the lithium salt used in this application contains at least one of fluorine and phosphorus.

[0118] In some embodiments, the lithium salt of this application comprises lithium hexafluorophosphate (LiPF6) lithium bis(sulfonyl)imide (LiN(C) y F 2y+1 SO2)(C z F 2z+1SO2), where y and z are at least one of natural numbers.

[0119] In some embodiments, the concentration of lithium salt in the electrolyte is about 0.5-3 mol / L, preferably about 0.5-2 mol / L, and more preferably about 0.8-1.5 mol / L, based on the total volume of the electrolyte.

[0120] In this application, the preparation method of the electrolyte is not limited and can be prepared according to conventional electrolyte preparation methods known to those skilled in the art.

[0121] [Electrochemical device]

[0122] Next, the electrochemical device of this application will be described.

[0123] The electrochemical device described in this application is, for example, a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor. The secondary battery is, for example, a lithium secondary battery, which includes, but is not limited to, lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0124] In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, a separator, and the electrolyte described above in this application.

[0125] In some embodiments, the charging cut-off voltage of the electrochemical device of this application is not less than 4.2V.

[0126] <Positive Electrode Tablets>

[0127] A positive electrode sheet is a type of positive electrode sheet known in the art and suitable for use in electrochemical devices. In some embodiments, the positive electrode sheet includes a positive current collector and a layer of positive active material disposed on the positive current collector. The positive active material layer includes a positive active material, a positive conductive agent, and a positive binder.

[0128] The positive electrode active material can be any conventionally known material known in the art that can be used as a positive electrode active material in electrochemical devices and is capable of reversibly inserting and deintercalating active ions. In some embodiments, the positive electrode active material contains a composite oxide containing lithium and at least one selected from cobalt, manganese, and nickel.

[0129] In some embodiments, the positive electrode active material comprises:

[0130] Li a A 1-b B b D2 (where 0.90≤a≤1.8, 0≤b≤0.5), Li a E 1-b B b O 2-c D c(where 0.90≤a≤1.8, 0 <b≤0.5,0≤c≤0.05)、LiE 2-b B b 0 4-c D c (where 0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b B c D α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2), Li a Ni 1-b-c Co b B c O 2-α F α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Co b B c O 2-α F2 (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c MnbB c D α (where 0.90≤a≤1.8, 0 <b≤0.5,0≤c≤0.05,0<α<2)、Li a Ni 1-b-c Mn b B c O 2-α F α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b- c Mn b B c O 2-α F2 (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni b E c G d O2 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Ni b Co c Mn d G eO2 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1), Li a NiG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1), Li a CoG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1), Li a MnG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn2G b O4 (where 0.90≤a≤1.8, 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3(0≤f≤2), Li 3-f At least one of Fe2(PO4)3 (0≤f≤2) and LiFePO4.

[0131] In the above chemical formulas, A is Ni, Co, Mn or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; F is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; I is Cr, V, Fe, Sc, Y or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0132] In some embodiments, the D of the positive electrode active material v 10 is no larger than 18 μm;

[0133] In some embodiments, the specific surface area (BET) of the positive electrode active material is not greater than 0.5 m². 2 / g.

[0134] Positive electrode conductive agents are used to provide conductivity to the positive electrode, thereby improving its conductivity. Positive electrode conductive agents are conductive materials known in the art that can be used as the active material layer of the positive electrode. The positive electrode conductive agent can be selected from any conductive material, as long as it does not cause a chemical change. In some embodiments, the positive electrode conductive agent comprises at least one of the following: carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber), metal-based materials (e.g., metal powders or metal fibers including copper, nickel, aluminum, silver, etc.), and conductive polymers (e.g., polyphenylene derivatives).

[0135] Positive electrode binders are known in the art and can be used as binders for positive electrode active material layers. Positive electrode binders can improve the adhesion between positive electrode active material particles and between the positive electrode active material particles and the positive electrode current collector. In some embodiments, the positive electrode binder comprises at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon.

[0136] In some embodiments, the compaction density of the positive electrode active material layer is less than 4.5 g / cm³. 3 In some embodiments, the compaction density of the positive electrode active material layer is 4.0-4.3 g / cm³. 3 .

[0137] The positive current collector is metal, and in some embodiments, the metal is, for example, but not limited to, aluminum foil.

[0138] In some embodiments, the structure of the positive electrode is a structure known in the art for use in electrochemical devices.

[0139] In some embodiments, the method for preparing the positive electrode sheet is a method known in the art for preparing positive electrode sheets that can be used in electrochemical devices. In some embodiments, in the preparation of the positive electrode slurry, a positive electrode active material and a binder are typically added, and conductive materials and thickeners are added as needed before dissolving or dispersing in a solvent to form the positive electrode slurry. The solvent is removed by evaporation during the drying process. The solvent is a solvent known in the art that can be used as a layer of positive electrode active material, such as, but not limited to, N-methylpyrrolidone (NMP).

[0140] Negative electrode film

[0141] The negative electrode sheet is a type of negative electrode sheet known in the art and used in electrochemical devices. In some embodiments, the negative electrode sheet includes a negative electrode current collector and a layer of negative electrode active material disposed on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

[0142] The negative electrode active material can be any conventionally known material known in the art that can be used as a negative electrode active material in electrochemical devices, capable of intercalating or deintercalating active ions, or capable of doping or dedoping active ions.

[0143] In some embodiments, the negative electrode active material comprises at least one of lithium metal, lithium metal alloy, materials capable of doping / dedoping lithium, transition metal oxides, and carbon materials.

[0144] In some embodiments, the lithium metal alloy contains lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, or Sn.

[0145] In some embodiments, the material capable of doping / dedoping lithium contains Si, SiO x (0 < x < 2), Si / C composite, Si-Q alloy (where Q is not Si and is an alkali metal, alkaline earth metal, Group 13 to Group 16 element, transition element, rare earth element, or a combination thereof), Sn, SnO z (0 < z < 2), Sn / C composite, Sn-R alloy (where R is not Sn and is an alkali metal, alkaline earth metal, Group 13 to Group 16 element, transition element, rare earth element, or a combination thereof), or at least one of them.

[0146] Exemplary elements of Q and R may be at least one of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po.

[0147] In some embodiments, SiO x (0 < x < 2) is a porous silicon-based anode active material, and the average particle size D50 of the porous SiO x particles is 1 μ m to 20 μ m. In some embodiments, when measured on the surface, the average diameter of the pores in the SiO x particles is 30 nm to 500 nm, and the specific surface area of the SiO x particles is 5 m 2 / g to 50 m 2 / g. In some embodiments, the SiO x particle silicon-based anode active material may further contain at least one of Li2SiO3 and Li4SiO4.

[0148] In some embodiments, the carbon in the Si / C composite is not aggregated and dispersed in a bulk form within the Si particles, but rather uniformly dispersed in an atomic state within the Si particles. In some embodiments, the molar ratio of C to Si (i.e., C / Si) can be in the range of greater than 0 and less than 18. In some embodiments, the carbon content in the Si / C composite can be 1%-50% relative to the total weight of the Si / C composite. In some embodiments, the particle size of the Si / C composite can be 10 nm-100 nm. μ m.

[0149] The carbon material can be any carbon material known in the art that can be used as a carbon-based negative electrode active material in electrochemical devices. In some embodiments, the carbon material comprises at least one of crystalline carbon and amorphous carbon. In some embodiments, the crystalline carbon is natural graphite or artificial graphite. In some embodiments, the crystalline carbon is in the shape of amorphous, plate-like, flake-like, spherical, or fibrous. In some embodiments, the crystalline carbon is low-crystallinity carbon and high-crystallinity carbon. In some embodiments, low-crystallinity carbon comprises at least one of soft carbon and hard carbon. In some embodiments, high-crystallinity carbon comprises at least one of natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbon. In some embodiments, high-temperature calcined carbon is petroleum or coke derived from coal tar pitch. In some embodiments, amorphous carbon comprises at least one of soft carbon, hard carbon, mesophase pitch carbonization products, and calcined coke.

[0150] Negative electrode conductive agents are used to provide conductivity to the negative electrode, thereby improving its conductivity. Negative electrode conductive agents are conductive materials known in the art that can be used as the active material layer of the negative electrode. The negative electrode conductive agent can be selected from any conductive material, as long as it does not cause a chemical change. In some embodiments, the negative electrode conductive agent comprises at least one of the following: carbon-based materials (e.g., natural graphite, artificial graphite, conductive carbon black, acetylene black, Ketjen black, carbon fiber), metal-based materials (e.g., metal powders or metal fibers including copper, nickel, aluminum, silver, etc.), and conductive polymers (e.g., polyphenylene derivatives).

[0151] Negative electrode binders are known in the art and can be used as binders for the negative electrode active material layer. In some embodiments, the negative electrode binder comprises at least one of the following: ethylene difluoropropylene-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon.

[0152] The negative electrode current collector is a metal. In some embodiments, the negative electrode current collector is, for example, but not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0153] In some embodiments, the structure of the negative electrode is a structure known in the art for use in electrochemical devices.

[0154] In some embodiments, the method for preparing the negative electrode sheet is a method known in the art for preparing negative electrode sheets that can be used in electrochemical devices. In some embodiments, in the preparation of the negative electrode slurry, a negative electrode active material and a binder are typically added, and conductive materials and thickeners are added as needed, followed by dissolution or dispersion in a solvent to form the negative electrode slurry. The solvent is removed by evaporation during the drying process. The solvent is a solvent known in the art that can be used as a layer of negative electrode active material, such as, but not limited to, water. The thickener is a thickener known in the art that can be used as a layer of negative electrode active material, such as, but not limited to, sodium carboxymethyl cellulose.

[0155] <Isolation membrane>

[0156] The separator is a separator known in the art that can be used in electrochemical devices, such as, but not limited to, polyolefin porous membranes. In some embodiments, the polyolefin porous membrane may be a single-layer or multi-layer membrane composed of one or more of polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-methyl methacrylate copolymer.

[0157] In some embodiments, a coating is applied to the polyolefin porous membrane. In some embodiments, the coating comprises an organic coating and an inorganic coating. In some embodiments, the organic coating comprises at least one selected from polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, acrylic-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, and sodium carboxymethyl cellulose. In some embodiments, the inorganic coating comprises at least one selected from SiO2, Al2O3, CaO, TiO2, ZnO2, MgO, ZrO2, and SnO2.

[0158] This application does not impose any particular limitations on the morphology and thickness of the separator. The method for preparing the separator is a well-known method in the art and can be used in electrochemical devices.

[0159] <Outer Packaging Shell>

[0160] In some embodiments, the electrochemical device further includes an outer packaging housing. The outer packaging housing is a type of outer packaging housing known in the art that can be used in electrochemical devices and is stable to the electrolyte used, such as, but not limited to, a metallic outer packaging housing.

[0161] [Electronic Devices]

[0162] Finally, the electronic device described in this application is described.

[0163] The electronic device covered by this application is any electronic device, such as, but not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors. It should be noted that the electrochemical device covered by this application is applicable not only to the electronic devices listed above, but also to energy storage power stations, maritime transport vehicles, and air transport vehicles. Air transport vehicles include both intra-atmosphere and extra-atmosphere air transport vehicles.

[0164] In some embodiments, the electronic device includes the electrochemical device described above in this application.

[0165] The present application is further illustrated below with reference to the embodiments. In the specific embodiments described below, only examples of lithium-ion batteries are shown, but the present application is not limited thereto. Unless otherwise specified, the reagents, materials, and instruments used in the following embodiments and comparative examples are commercially available or synthesized.

[0166] The specific compounds used in the examples are as follows.

[0167] Additive A:

[0168]

[0169] Additive C:

[0170] Lithium tetrafluoroborate (LiBF4) and lithium difluorooxalate borate (LiDFOB).

[0171] Additive D:

[0172] Lithium difluorophosphate (LiPO2F2) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0173] Additive E:

[0174] 2,4-Butyrolactone

[0175] 1,3-Propanesulfonyl lactone

[0176] vinyl sulfate

[0177] 4-Methylvinyl sulfate

[0178] Additive F:

[0179] 1,2,3-Tris(2-cyanoethoxy)propane 1,3,6-Hexanetrionitrile adiponitrile

[0180] 1,2-Di(2-cyanoethoxy)ethane

[0181] The lithium-ion batteries of Examples 1-6, S1-S11, and Sˊ were all prepared according to the following method.

[0182] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), and propyl propionate (PP) were mixed uniformly in a mass ratio of 1:1:1:1:1 to form a non-aqueous organic solvent. Then, thoroughly dried lithium salt LiPF6 (1M) was dissolved in the above non-aqueous organic solvent to form a basic electrolyte. A certain mass of additives was added to the basic electrolyte to prepare the electrolytes used in Examples 1-62, Comparative Examples 1-6, Examples S1-S11, and Comparative Example Sˊ.

[0183] (2) Preparation of positive electrode

[0184] The positive electrode active material LCO (molecular formula LiCoO2), conductive carbon black, and binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 97.9:0.9:1.2 to form a uniform positive electrode slurry. This slurry was then coated onto the positive electrode current collector Al foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0185] (3) Preparation of negative electrode

[0186] The negative electrode active material graphite, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) were thoroughly mixed in an appropriate amount of deionized water solvent at a weight ratio of 97.4:1.4:1.2 to form a uniform negative electrode slurry. This slurry was then coated onto the negative electrode current collector Cu foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0187] (4) Preparation of the separating membrane

[0188] PE porous polymer film is used as the separator.

[0189] (5) Preparation of lithium-ion batteries

[0190] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator acting as a separator between the positive and negative electrode sheets. Then, the electrode assembly is wound up to obtain the electrode assembly. The electrode assembly is placed in the outer packaging foil, leaving an injection port. The prepared electrolyte is poured in through the injection port. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is completed.

[0191] The following describes the performance testing process of the lithium-ion batteries in Examples 1-62 and Comparative Examples 1-6, Examples S1-S11 and Comparative Example Sˊ.

[0192] (1) High-temperature storage performance test at 4.45V

[0193] The battery was charged at 25℃ with a constant current of 0.5C to 4.45V, and then charged with a constant voltage to a current of 0.05C. The thickness of the lithium-ion battery was measured and recorded as d0. The battery was then placed in an 85℃ oven for 24 hours, and the thickness was monitored and recorded as d. The thickness expansion rate (%) of the lithium-ion battery after 24 hours of high-temperature storage is calculated as (d-d0) / d0 × 100%. The test was stopped if the thickness expansion rate exceeded 50%.

[0194] (2) High-temperature storage performance test at 4.5V

[0195] The battery was charged at 25℃ with a constant current of 0.5C to 4.5V, and then charged with a constant voltage to a current of 0.05C. The thickness of the lithium-ion battery was measured and recorded as d0. The battery was then placed in an 85℃ oven for 24 hours, and the thickness was monitored and recorded as d. The thickness expansion rate (%) of the lithium-ion battery after 24 hours of high-temperature storage is calculated as (d-d0) / d0 × 100%. The test was stopped if the thickness expansion rate exceeded 50%.

[0196] (3) Cyclic performance test

[0197] At 25°C, the battery was charged at 0.7C to 4.45V, and then charged at a constant voltage of 0.05C at 4.45V. It was then discharged at 1C to 3.0V, and this cycle of 0.7C charging and 1C discharging was repeated 800 times, recording the current capacity retention rate.

[0198] (4) Float charging performance test

[0199] The battery was discharged to 3.0V at 0.5C at 25℃, then charged to 4.45V at 0.5C, and then charged at a constant voltage of 0.05C at 4.45V. The thickness of the lithium-ion battery was measured and recorded as d0. The battery was then placed in a 45℃ oven and charged at a constant voltage of 4.45V for 42 days. The thickness change was monitored and recorded as d. The thickness expansion rate (%) of the lithium-ion battery during float charging is calculated as (d-d0) / d0×100%.

[0200] The types and contents of additives in the electrolytes used in Examples 1-62 and Comparative Examples 1-6, Examples S1-S11 and Comparative Example Sˊ, as well as the performance test results of the lithium-ion batteries, are shown in Tables 1-4, respectively. The contents of each additive are mass percentages calculated based on the mass of the electrolyte.

[0201] Table 1

[0202]

[0203]

[0204] Note: The blank spaces in Table 1 indicate that no data has been added.

[0205] As can be seen from the examples and comparative examples in Table 1, compound I-5, as additive A, not only improves the 4.45V high-temperature storage performance of lithium-ion batteries but also their 4.5V high-temperature storage performance, and also significantly improves the battery's cycle performance. The improvement effect varies for different charging cut-off voltages; with increasing content, the degree of improvement initially increases, then decreases, and finally tends to reach equilibrium. Compounds I-11, I-12, and I-30, also additive A, also improve the high-temperature storage performance and cycle performance of lithium batteries at different charging cut-off voltages to varying degrees. Furthermore, when additive E is added to the electrolyte containing additive A, the high-temperature storage performance and cycle performance of the lithium battery at different charging cut-off voltages are further improved.

[0206] Although the additive in Comparative Example 1 also contains both cyano and phosphono groups, its high-temperature storage performance and cycle performance are far inferior to those of the example containing additive A. The possible reason is that additive A is a phosphono-oxygen polycyano functional group compound. The cyano (-CN) functional group in its structure can form a complex with the transition metal in the positive electrode active material, which can stabilize the transition metal on the surface of the positive electrode active material. At the same time, since the molecule contains phosphono-oxygen functional groups, it can attach to the surface of the positive electrode active material synchronously with the cyano group, improving the antioxidant properties of the complex formed by the transition metal. Therefore, it can effectively inhibit the continuous decomposition of the electrolyte and suppress high-temperature gas generation.

[0207] Table 2

[0208]

[0209]

[0210] Note: The blank spaces in Table 2 indicate that no data has been added.

[0211] As can be seen from the examples and comparative examples in Table 2, when additive C is added to the electrolyte containing additive A, the high-temperature storage performance of lithium-ion batteries at 4.5V is further improved.

[0212] Table 3

[0213]

[0214]

[0215] Note: The blank spaces in Table 3 indicate that no data has been added.

[0216] As can be seen from the examples and comparative examples in Table 3, the combined use of additive A and additive F can significantly improve the float charging performance of lithium-ion batteries.

[0217] Table 4

[0218]

[0219]

[0220] Note: The blank spaces in Table 4 indicate that no data has been added.

[0221] As can be seen from the examples and comparative examples in Table 4, the combination of various additives C to F with additive A can further improve the high-temperature storage performance of lithium-ion batteries.

[0222] The lithium-ion batteries in Examples 63-80 and Comparative Examples 7-9 were all prepared according to the following method.

[0223] (1) Preparation of electrolyte

[0224] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly in a mass ratio of 3:3:4. Then, thoroughly dried lithium salt LiPF6 (1M) was dissolved in the above non-aqueous organic solvent to form a basic electrolyte. A certain mass of additives was added to the basic electrolyte to prepare the electrolytes used in Examples 63-80 and Comparative Examples 7-9.

[0225] (2) Preparation of positive electrode

[0226] The positive electrode active material NCM811 (molecular formula LiNi) 0.8 Mn 0.1 Co 0.1 O2), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed thoroughly in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 96:2:2 to form a uniform positive electrode slurry. This slurry is then coated onto the positive electrode current collector Al foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0227] (3) Preparation of negative electrode

[0228] The negative electrode active material graphite, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) were thoroughly mixed in an appropriate amount of deionized water solvent at a weight ratio of 97.4:1.4:1.2 to form a uniform negative electrode slurry. This slurry was then coated onto the negative electrode current collector Cu foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0229] (4) Preparation of the separating membrane

[0230] PE porous polymer film is used as the separator.

[0231] (5) Preparation of lithium-ion batteries

[0232] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator acting as a separator between the positive and negative electrode sheets. Then, the electrode assembly is wound up to obtain the electrode assembly. The electrode assembly is placed in the outer packaging foil, leaving an injection port. The prepared electrolyte is poured in through the injection port. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is completed.

[0233] The following describes the testing process for the 85°C high-temperature storage performance of the lithium-ion batteries in Examples 63-80 and Comparative Examples 7-9.

[0234] The battery was charged at 25°C with a constant current of 0.5C to 4.25V, and then charged with a constant voltage to a current of 0.05C. The thickness of the lithium-ion battery was measured and recorded as d0. The battery was then placed in an 85°C oven for 24 hours, and the thickness was monitored and recorded as d. The thickness expansion rate (%) of the lithium-ion battery after 24 hours of high-temperature storage is calculated as (d-d0) / d0×100%. If the thickness expansion rate exceeds 50%, the test is stopped.

[0235] Table 5 shows the types and contents of additives in the electrolytes used in Examples 63-80 and Comparative Examples 7-9, as well as the performance test results of the lithium-ion batteries. The contents of each additive are calculated as a percentage by mass based on the mass of the electrolyte.

[0236] Table 5

[0237]

[0238]

[0239] Note: The blank spaces in Table 5 indicate that no data has been added.

[0240] As can be seen from the examples and comparative examples in Table 5, lithium difluorophosphate (LiPO2F2) and lithium tetrafluorooxalate phosphate (LiTFOP) can form films on the cathode, inhibit the continuous oxidation and decomposition of the electrolyte, and reduce gas production. Therefore, adding additive D to the electrolyte containing additive A can further improve the high-temperature storage performance.

[0241] The lithium-ion batteries in Examples 81-96 and Comparative Examples 10-12 were all prepared according to the following method.

[0242] (1) Preparation of electrolyte

[0243] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP) were mixed uniformly in a mass ratio of 1:2:6:1. Then, thoroughly dried lithium salt LiPF6 (1M) was dissolved in the above non-aqueous organic solvent to form a basic electrolyte. A certain mass of additives was added to the basic electrolyte to prepare the electrolytes used in Examples 81-96 and Comparative Examples 10-12.

[0244] (2) Preparation of positive electrode

[0245] The positive electrode active material LCO (molecular formula LiCoO2), conductive carbon black, and binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 97.9:0.9:1.2 to form a uniform positive electrode slurry. This slurry was then coated onto the positive electrode current collector Al foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0246] (3) Preparation of negative electrode

[0247] The negative electrode active material graphite, silicon oxide material, thickener sodium carboxymethyl cellulose (CMC), and modified polyacrylic acid are mixed thoroughly in an appropriate amount of deionized water solvent at a weight ratio of 87:10:0.6:2.4 to form a uniform negative electrode slurry. This slurry is then coated onto the negative electrode current collector Cu foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0248] (4) Preparation of the separating membrane

[0249] PE porous polymer film is used as the separator.

[0250] (5) Preparation of lithium-ion batteries

[0251] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator acting as a separator between the positive and negative electrode sheets. Then, the electrode assembly is wound up to obtain the electrode assembly. The electrode assembly is placed in the outer packaging foil, leaving an injection port. The prepared electrolyte is poured in through the injection port. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is completed.

[0252] The following describes the testing process for the 60°C high-temperature storage performance of the lithium-ion batteries in Examples 81-96 and Comparative Examples 10-12.

[0253] The battery was charged at 25℃ with a constant current of 0.5C to 4.45V, and then charged with a constant voltage to a current of 0.05C. The thickness of the lithium-ion battery was measured and recorded as d0. The battery was then placed in a 60℃ oven for 12 days, and the thickness was monitored and recorded as d. The thickness was measured every 4 days. The thickness expansion rate (%) of the lithium-ion battery after 12 days of storage at 60℃ is calculated as (d-d0) / d0 × 100%. The test was stopped when the thickness expansion rate exceeded 100%.

[0254] Table 5 shows the types and contents of additives in the electrolytes used in Examples 81-96 and Comparative Examples 10-12, as well as the performance test results of the lithium-ion batteries. The contents of each additive are calculated as a percentage by mass based on the mass of the electrolyte.

[0255] Table 6

[0256]

[0257] Note: The blank spaces in Table 6 indicate that no data has been added.

[0258] As can be seen from the examples and comparative examples in Table 6, when compound II-8 or compound II-9 is combined with additive A, it can improve the high-temperature storage performance of lithium-ion batteries. The possible reason is that compound II-8 or compound II-9 can form a film on the silicon anode, while additive A acts as a protective additive for the cathode. Therefore, additive A and additive B work synergistically to improve the high-temperature storage performance of lithium-ion batteries.

[0259] The above description is merely an example of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and are all within the scope of the technical solution of this application.

Claims

1. An electrolyte, wherein, a compound represented by Formula I-A; wherein A 1 , A 2 , A 3 are each independently selected from Formula I-B or Formula I-C, A 1 , A 2 , A 3 at least two of which are Formula I-C; wherein, in Formula I-A, n is an integer selected from 1 to 10, and m is selected from 0 or 1; wherein, in formula I-B, formula I-C, represents the site at which two adjacent atoms are attached; wherein R 11 , R 13 are each independently selected from substituted or unsubstituted C1-C 10 alkylene, substituted or unsubstituted C2-C 10 alkenylene, substituted or unsubstituted C2-C 10 alkynylene, substituted or unsubstituted C3-C 10 alkynylene, substituted or unsubstituted C6-C 10 arylene, substituted or unsubstituted C3-C 10 cycloalkylidene; when substituted, substituents include halogen; R 12 each independently selected from halogen, substituted or unsubstituted C1-C 10 alkyl, substituted or unsubstituted C2-C 10 alkenyl, substituted or unsubstituted C2-C 10 alkynyl, substituted or unsubstituted C3-C 10 alkenyl, substituted or unsubstituted C6-C 10 aryl, substituted or unsubstituted C3-C 10 cycloalkyl; and when substituted, substitutions include halogen; the electrolyte further comprises a compound represented by Formula IV-A; wherein represents a single or double bond, and x, y each independently represents 0 or 1 ; when one of x, y in formula IV-A when one of x, y in formula IV-A when one of x, y in formula IV-A when both of the two x, y are both 1 when both of the two when both of the double bonds in formula IV-A are represented by =CH2, then x, y are both 0; A 42 A 43 A 45 A 46 Each is independently selected from halogens, substituted or unsubstituted C1-C6 alkyl groups, formula IV-B, formula IV-C, and formula IV-D, and when formula IV-C is selected, A 42 A 43 A 45 A 46 Two or four of them are selected from formula IV-C to form a ring structure; A 41 A 44 Each is independently selected from oxygen, halogen, substituted or unsubstituted C1-C6 alkyl groups, formula IV-B, formula IV-C, and formula IV-D, and when formula IV-C is selected, A 41 A 44 All are selected from formula IV-C to form a cyclic structure; wherein, when substituted, the substituents include halogens; A 41 、A 42 、A 43 、A 44 、A 45 、A 46 not all fluorine; in Formula IV-B, Formula IV-C, Formula IV-D, R 41 , R 43 each independently is selected from substituted or unsubstituted C1-C6alkyl, substituted or unsubstituted C2-C6alkenyl; R 42 selected from substituted or unsubstituted C1-C6alkylene, substituted or unsubstituted C2-C6alkenylene; wherein, when substituted, the substituent includes halogen; in Formula IV-C, an O atom is connected to a P atom in Formula IV-A, and z represents 0 or 1; wherein, the mass percentage content of the compound represented by Formula I-A is 0.01% to 10% based on the mass of the electrolyte; the electrolyte further comprises a polycarbonic compound; wherein, the polycarbonic compound includes at least one of 1,2,3-tris(2-cyanoethoxy)propane, 1,3,6-hexanetricarbonitrile, 1,2-bis(2-cyanoethoxy)ethane, and adiponitrile; wherein, the ratio of the mass fraction of the compound represented by Formula I-A to the polycarbonic compound is 0.01 to 1.

2. The electrolyte of claim 1, wherein, the compound represented by Formula I-A includes at least one of compounds represented by (I-1) to (I-30):

3. The electrolyte of claim 1, wherein, the electrolyte further comprises at least one of a compound represented by Formula II-A, a compound represented by Formula III-A, a compound represented by V-A, or a compound represented by Formula V-B; wherein R 21 , R 22 each independently is selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, substituted or unsubstituted C2-C5 alkynyl, substituted, the substituents including halogen; R 21 , R 22 may be bonded to form a cyclic structure; wherein A 31 , A 32 , A 33 , A 34 are each independently selected from halogen, one of formulae III-X, III-Y, III-Z, and when formula III-Y is selected, A 31 , A 32 , A 33 , A 34 two or four of which are selected from formula III-Y to form a cyclic structure; wherein R 31 , R 33 each independently is selected from substituted or unsubstituted C1-C6alkyl, substituted or unsubstituted C2-C6alkenyl; R 32 each independently selected from substituted or unsubstituted C1-C6alkylene, substituted or unsubstituted C2-C6alkenylene; wherein, when substituted, the substituent includes halogen; represents the site at which two adjacent atoms are attached; in Formula III-Y, an O atom is connected to a B atom in Formula III-A, and k is 0 or 1; wherein R 51 , R 52 , R 53 , R 54 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C 10 enyl, substituted or unsubstituted C2-C 10 ynyl, substituted or unsubstituted C3-C 10 ycloalkyl, substituted or unsubstituted C6-C 10 ryl, substituted or unsubstituted C1-C6 aliphatic heterocyclyl, substituted or unsubstituted C1-C6 aromatic heterocyclyl, substituted or unsubstituted C1-C6 heteroatom-containing functional group; wherein, when substituted, the substituents include halogen, R 51 , R 52 may bond to form a ring structure; R 53 , R 54 may bond to form a ring structure; and the heteroatom in the heteroatom-containing functional group includes at least one of B, N, O, Si, P, and S.

4. The electrolyte according to claim 3, satisfying at least one of the following conditions: a) the mass percentage content of the compound represented by Formula II-A is 0.01% to 10% based on the mass of the electrolyte; b) the mass percentage content of the compound represented by Formula III-A is 0.1% to 5% based on the mass of the electrolyte; c) the mass percentage content of the compound represented by Formula IV-A is 0.1% to 5% based on the mass of the electrolyte; d) the sum of the mass percentage contents of the compounds represented by Formula V-A and Formula V-B is 0.01% to 10% based on the mass of the electrolyte; e) the mass percentage content of the polycarbonic compound is 0.1% to 10% based on the mass of the electrolyte.

5. The electrolyte of claim 3, wherein, the compound represented by Formula II-A includes at least one of compounds represented by Formula (II-1) to Formula (II-22):

6. The electrolyte of claim 3, wherein, the compound represented by Formula III-A includes at least one of lithium tetrafluoroborate, lithium bis(oxalato)borate, and lithium difluoro(oxalato)borate.

7. The electrolyte of claim 1, wherein, the compound represented by Formula IV-A includes at least one of lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

8. The electrolyte according to claim 3, wherein, the compound represented by Formula V-A includes at least one of compounds represented by Formula (V-1) to Formula (V-16): the compound represented by Formula V-B includes at least one of compounds represented by Formula (V-17) to Formula (V-20):

9. An electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte according to any one of claims 1 to 8.

10. An electronic device comprising the electrochemical device according to claim 9.

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