CN117080564A

CN117080564A - Electrolyte, battery cell, battery and electricity utilization device

Info

Publication number: CN117080564A
Application number: CN202311274652.XA
Authority: CN
Inventors: 吴巧; 吴则利; 彭淑婷; 韩昌隆; 刘文浩
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-09-28
Filing date: 2023-09-28
Publication date: 2023-11-17

Abstract

An electrolyte, a battery monomer, a battery and an electricity utilization device belong to the technical field of batteries. The electrolyte comprises: a solvent comprising ethylene carbonate; an additive comprising an oxygen-containing silane compound; the mass content A of the oxygen-containing silane compound and the mass content B of the ethylene carbonate based on the total mass of the electrolyte satisfy the following conditions: a is more than or equal to 0.01 and B is more than or equal to 0.5; the oxygen-containing silane compound includes at least one of compounds having the following structure:，，，. The technical scheme of the embodiment of the application can improve the performance of the battery monomer.

Description

Electrolyte, battery cell, battery and electricity utilization device

Technical Field

The application relates to the technical field of batteries, in particular to electrolyte, a battery monomer, a battery and an electric device.

Background

With the increasing increase of environmental pollution, the new energy industry is receiving more and more attention. In the new energy industry, battery technology is an important factor in its development.

The development of battery technology requires consideration of various design factors such as capacity, energy density, cycle life, reliability, and the like. The electrolyte is an important component of the battery cell and is critical to the performance of the battery cell. Therefore, how to provide an electrolyte to improve the performance of the battery cell is a technical problem to be solved.

Disclosure of Invention

The present application has been made in view of the above problems, and an object of the present application is to provide an electrolyte solution for improving the performance of a battery cell.

In order to achieve the above object, the present application provides an electrolyte, a battery cell, a battery and an electric device.

In a first aspect, there is provided an electrolyte comprising: a solvent comprising ethylene carbonate; an additive comprising an oxygen-containing silane compound; the mass content A of the oxygen-containing silane compound and the mass content B of the ethylene carbonate satisfy the following conditions based on the total mass of the electrolyte: a is more than or equal to 0.01 and B is more than or equal to 0.5; the oxygen-containing silane compound includes at least one of compounds having the following structure:

，/>，/>，/>wherein R comprises: at least one of C1-C20 alkyl or alkoxy, C2-C20 alkenyl or alkenyloxy, C1-C20 acyl, C2-C20 ether linkage, C1-C20 silyl or C6-C20 aryl; r is R ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ Each independently includes at least one of the following substituted or unsubstituted groups: hydrogen, C1-C20 alkyl or alkoxy, C2-C20 alkenyl or alkenyloxy, C2-C20 alkynyl or alkynyloxy, C3-C20 cycloalkyl or epoxyalkyl, C6-C20 aryl, C1-C20 cyano, C1-C20 amino, C2-C20 ether linkage, C1-C20 ureido, C1-C20 carboxylate, C1-C20 sulfonate, C1-C20 isocyanate, C1-C20 thiocyanate, C4-C20 piperazinyl, C1-C20 silane, and the substituent comprises halogen elements.

The embodiment of the application provides an electrolyte, which comprises a solvent and an additive, wherein the solvent comprises ethylene carbonate, and the additive comprises an oxygen-containing silane compound. The Si-O bond in the oxygen-containing silane compound can remove proton hydrogen generated by solvolysis, can reduce the risk of reaction between the proton hydrogen and the positive electrode interface, plays a certain role in protecting the positive electrode interface, and is favorable for forming a uniform and compact electrolyte interface film. The mass content A of the oxygen-containing silane compound and the mass content B of the ethylene carbonate in the electrolyte are set to be as follows: the ratio of A to B is more than or equal to 0.01 and less than or equal to 0.5, thus being beneficial to improving the circulation stability of the battery monomer, reducing the increase rate of direct current internal resistance (DCR) in the circulation process of the battery monomer, inhibiting the decomposition of the solvent in the electrolyte from damaging the interface of the anode, reducing the gas generated by the decomposition of the solvent and improving the gas production condition of the battery monomer.

In one possible implementation, the mass content a of the oxygen-containing silane compound and the mass content B of the ethylene carbonate satisfy, based on the total mass of the electrolyte: a is more than or equal to 0.03 and B is more than or equal to 0.3.

Under the condition that B is not less than 0.03, the oxygen-containing silane compound in the electrolyte has proper mass content, which is favorable for forming a uniform, stable and compact electrolyte interface film on the positive electrode and reducing the DCR growth of the battery monomer in the long-time charge-discharge cycle process; in the case of not more than 0.3, the ethylene carbonate in the electrolyte has a proper mass content, which is beneficial to improving the conductivity of the electrolyte.

In one possible implementation, the mass content a of the oxygen-containing silane compound, based on the total mass of the electrolyte, satisfies: a is more than or equal to 0.3wt% and less than or equal to 2.5wt%. Thus, a compact and stable solid electrolyte membrane (CEI) can be effectively formed at the interface of the anode, the side reaction of the anode and the electrolyte is reduced, the cycling stability of the battery monomer is conveniently improved, the DCR growth in the cycling process of the battery monomer is reduced, and the storage gas production condition of the battery monomer, especially the storage gas production condition at high temperature, is improved.

In one possible implementation, the mass content a of the oxygen-containing silane compound, based on the total mass of the electrolyte, satisfies: a is more than or equal to 1 weight percent and less than or equal to 1.5 weight percent. Thus, the method is beneficial to further reducing the growth rate of DCR of the battery monomer in the circulation process and improving the gas production condition of the battery monomer.

In one possible implementation, the mass content B of the ethylene carbonate, based on the total mass of the electrolyte, satisfies: b is more than or equal to 5wt% and less than or equal to 30wt%. Ethylene Carbonate (EC) has a high dielectric constant and contributes to dissociation of lithium ions and to improvement of the conductivity of the electrolyte. In addition, the ethylene carbonate is locally decomposed on the surface of the negative electrode in the charge and discharge process of the battery monomer, so that a solid electrolyte interface film can be formed on the surface of the negative electrode, and a certain protection effect can be achieved on the negative electrode.

In one possible implementation, the mass content B of the ethylene carbonate, based on the total mass of the electrolyte, satisfies: b is more than or equal to 5wt% and less than or equal to 16wt%. In this way, the ethylene carbonate has a suitable mass content, and more oxygen-containing silane compound can be arranged in the electrolyte, thereby reducing side reactions of the positive electrode and the electrolyte.

In one possible implementation, the electrolyte further comprises an electrolyte salt, the mass content B of the ethylene carbonate and the mass content C of the electrolyte salt, based on the total mass of the electrolyte, satisfying: b is more than or equal to 1.2, C is less than or equal to 2.5; alternatively, 1.5.ltoreq.B.ltoreq.C.ltoreq.2.2.

In the case where the mass content of the ethylene carbonate and the mass content of the electrolyte salt satisfy the above ranges, the EC molecules may be attracted to the surroundings by the electrolyte salt molecules, so that the risk of the EC being oxidized may be reduced. For example, the electrolyte salt is LiPF ₆ Dissociated Li ⁺ Tends to coordinate with EC having a relatively high dielectric constant, typically one Li ⁺ Coordination will occur with 2-4 ECs, thereby reducing the risk of oxidation of EC molecules at the positive electrode.

In one possible implementation, the mass content C of the electrolyte salt, based on the total mass of the electrolyte, satisfies: c is more than or equal to 8wt% and less than or equal to 17wt%; alternatively, 10wt% or more and 17wt% or less of C. Thus, the electrolyte has proper ionic conductivity and the battery monomer has proper internal resistance.

In one possible implementation, the electrolyte salt includes: at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalato phosphate, lithium bisoxalato borate, or lithium difluorooxalato borate. In this way, the electrolyte salt is conveniently selected according to flexibility.

In one possible implementation, the electrolyte salt comprises lithium hexafluorophosphate.

In one possible implementation, the oxygen-containing silane compound includes: at least one of chloro (dimethyl) methoxy silane, divinyl tetramethyl disiloxane, diethoxymethyl vinyl silane, dimethoxy methyl vinyl silane, trimethoxy silane, n-hexadecyl trimethoxy silane, 3-chloroisobutyl trimethoxy silane, (3-aminopropyl) trimethoxy silane, 3-piperazinyl propyl trimethoxy silane, triethoxy silane, propyl triethoxy silane, n-octyl triethoxy silane, (3-glycidoxypropyl) triethoxy silane, phenyl triethoxy silane, 2-cyanoethyl triethoxy silane, diethylaminomethyl triethoxy silane, 3-aminopropyl triethoxy silane, 3-ureidopropyl triethoxy silane, 3-isocyanatopropyl triethoxy silane, 3-thiocyanopropyltriethoxy silane, vinyltris (trimethylsiloxy) silane, vinyltris [ (1-methylvinyl) oxy ] silane, vinyltris (2-methoxyethoxy) silane, triacetoxyethyl silane, methyltriacetoxy silane, tetramethoxy silane, tetraphenoxy silane. The above-mentioned oxygen-containing silane compound has a relatively suitable solubility in a solvent, and is convenient for exerting the function of the oxygen-containing silane compound.

In one possible implementation, the oxygen-containing silane compound includes: at least one of vinyltris (trimethylsiloxy) silane, vinyltris [ (1-methylvinyl) oxy ] silane, and vinyltris (2-methoxyethoxy) silane. The oxygen-containing silane compound has a good matching effect with EC, and the battery monomer has a high cycle capacity retention rate and a low gas yield.

In one possible implementation, the mass content D of HF in the electrolyte satisfies: d is less than or equal to 150ppm. In this way, it is advantageous to improve the cycle life of the battery cell.

In one possible implementation, the mass content E of water in the electrolyte satisfies: e is less than or equal to 20ppm. Thus, the integrity of the CEI film is improved, the occurrence of side reaction is reduced, and the cycle performance of the battery monomer is improved.

In one possible implementation, the solvent further comprises ethyl methyl carbonate. The solvent may be a blend solvent of ethylene carbonate and ethylmethyl carbonate. The sum of the mass contents of ethylene carbonate, ethylmethyl carbonate, additives, electrolyte salts is 100wt% or close to 100wt% based on the total mass of the electrolyte.

In a second aspect, there is provided a battery cell comprising the electrolyte of the first aspect and any one of the possible implementations thereof.

In one possible implementation, the battery cell further includes a positive electrode sheet including a positive electrode active material including a transition metal oxide of lithium. The battery monomer prepared by taking the transition metal oxide of lithium as the positive electrode active material has higher capacity.

In one possible implementation, the lithium transition metal oxide has the formula Li _a Ni _b Co _c M _d N _e O _f A _g Wherein a is more than or equal to 0.8 and less than or equal to 1.3,0.1, b is more than or equal to less than or equal to 0.98,0.01 and less than or equal to 0.3, d is more than or equal to 0.01 and less than or equal to 0.6,0 and less than or equal to 0.5, f is more than or equal to 0 and less than or equal to 2, g is more than or equal to 0 and less than or equal to 2, M comprises at least one of Mn or Al, N comprises at least one of B, W, si, ti, zr, sr, sn, tb, nb, sb, se, ce or Te, and A comprises at least one of S, N, P, F, cl, br or I.

In one possible implementation, the volume average particle diameter Dv50 of the positive electrode active material satisfies: dv50.ltoreq.3μm.ltoreq.15μm, alternatively, dv50.ltoreq.5μm.ltoreq.10μm. Under the condition that the average grain diameter of the positive electrode active material is not smaller than 3 mu m, the positive electrode active material has proper specific surface area, proper surface energy and less possibility of agglomeration and side reaction with electrolyte are reduced, and the risk of increasing the internal resistance of the battery monomer can be reduced, so that the risk of increasing the temperature caused by excessive energy accumulation in the charging and discharging process can be reduced, and the reliability of the battery monomer is improved. Under the condition that the volume average particle size of the positive electrode active material is not more than 15 mu m, the positive electrode active material has a proper specific surface area, the combination between the positive electrode active material and the current collector is firm, the risk that the positive electrode active material is separated from the current collector can be reduced, and the risk of local short circuit of a battery cell caused by the fact that the positive electrode active material is free in electrolyte and contacted with the negative electrode active material can be reduced.

In one possible implementation, the mass content a of the oxygen-containing silane compound and the volume average particle diameter Dv50 of the positive electrode active material satisfy: 0.03 wt%/mum is less than or equal to A, and Dv50 is less than or equal to 0.8 wt%/mum; alternatively, 0.05 wt.%/μm.ltoreq.A: dv50.ltoreq.0.3 wt.%/μm. The relationship between the two is limited, so that the positive electrode interface can be effectively protected, the side reaction between the solvent and the positive electrode interface is reduced, and the gas yield of the battery is reduced.

In a third aspect, there is provided a battery comprising the battery cell of the second aspect and any one of the possible implementations thereof.

In a fourth aspect, there is provided an electrical device comprising a battery according to the third aspect.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a battery cell according to an embodiment of the application;

FIG. 2 is a schematic diagram of a battery according to an embodiment of the application;

Fig. 3 is a schematic diagram of an electrical device according to an embodiment of the application.

Detailed Description

Embodiments of the electrolyte, the battery cell, the battery, and the electric device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with the given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

At present, the lithium ion battery technology is rapidly developed, and the application field is continuously expanded. The lithium ion battery is not only applied to electronic devices such as mobile phones and notebook computers, but also widely applied to vehicles such as electric motorcycles and electric automobiles, and has been expanded in various fields such as military equipment and aviation fields. The market demands put higher demands on various aspects such as the cycle performance, the safety performance and the like of the lithium ion battery. Currently, in commercial lithium ion batteries, ethylene Carbonate (EC) having a high dielectric constant is mostly used as a main component of the nonaqueous electrolyte. However, EC has poor oxidation resistance and is easily oxidized and decomposed to generate gas, thereby causing a large expansion of the volume of the battery cell. The electrolyte is added with the corresponding additive, which is beneficial to improving the gas production of the battery monomer, reducing the expansion of the battery monomer and improving the cycle performance of the battery monomer. However, what kind of additive is added, and how the content of the additive in the electrolyte is set are critical to the performance of the battery.

In view of this, embodiments of the present application provide an electrolyte that includes a solvent including ethylene carbonate and an additive including an oxygen-containing silane compound. By reasonably setting the mass ratio of the oxygen-containing silane compound to the ethylene carbonate, the cycle performance of the battery monomer can be improved, and the gas production phenomenon of the battery monomer can be improved.

The battery monomer in the embodiment of the application can be used as a minimum unit of the battery. The battery cell comprises a positive pole piece, a negative pole piece, a separation membrane, electrolyte and the like.

[ electrolyte ]

The embodiment of the application provides an electrolyte, which comprises the following components: a solvent and an additive, wherein the solvent comprises ethylene carbonate and the additive comprises an oxygen-containing silane compound.

The oxygen-containing silane compound in the embodiment of the present application refers to a compound which includes a si—o bond and at least one organic group is directly bonded to a silicon atom. Wherein, the organic group may refer to the remaining part of the organic matter after one atom or group of atoms is removed.

Ethylene Carbonate (EC) has a relatively high dielectric constant, which is advantageous for dissociation of metal ions, such as lithium ions, and thus for improving the conductivity of the electrolyte. In addition, EC may decompose or partially decompose at the surface of the anode, thereby forming a solid electrolyte interface (Solid Electrolyte Interface, SEI) film, which may protect the anode to some extent.

During charging, as the voltage increases, the positive electrode active material in the cell produces a species with oxidizing properties (e.g., ternary positive electrode material precipitates oxygen atoms and produces highly oxidizing Ni ⁴⁺ ) And can cause dehydrogenation (i.e., oxidative decomposition) of EC at the surface of the positive electrode, thereby generating EC from which one hydrogen atom is removed, and adsorbed on the surface of the positive electrode active material. As delithiation proceeds, the driving force for decomposition of the solvent at the surface of the positive electrode continues to rise, so that EC will further remove one hydrogen atom to produce Vinylene Carbonate (VC). At the same time, ring opening of EC may also occur, producing oligomers such as C ₆ H ₈ O ₆ 、C ₉ H ₁₄ O ₈ 、C ₇ H ₁₀ O ₆ Etc., the dehydrogenation products of these solvents may eventually be oxidized to CO and CO ₂ . Therefore, the gas production in the battery monomer is obvious, and the battery monomer can expand, so that the performance of the battery monomer is not improved. At the same time these reactions also generate protons, thereby causing LiPF ₆ Is decomposed to produce HF, li _x PF _y O _z And PF (physical filter) ₃ And products such as O and the like affect the cycling stability of the lithium ion battery. Si-O in the oxygen-containing silane compound can remove proton hydrogen generated by solvolysis to a certain extent, inhibit the generation of HF, reduce the damage of HF to a positive electrode, and be beneficial to improving the cycle performance of a battery monomer; on the other hand, the oxygen-containing silane compound can form a uniform and dense positive electrode-electrolyte interface (CEI) film at the positive electrode interface, thereby serving to protect the positive electrode and reduce the generation of anionic oxygen (e.g., O ₂ ^- 、O ^- ) Thereby reducing the risk of oxidation of the solvent by anionic oxygen and thus reducing gas production.

The oxygen-containing silane compound includes at least one of compounds having the following structure:

，/>，/>，/>。

r comprises: at least one of C1-C20 alkyl or alkoxy, C2-C20 alkenyl or alkenyloxy, C1-C20 acyl, C2-C20 ether linkage, C1-C20 silyl or C6-C20 aryl.

R is the same group for the same structural formula. R may be the same or different for different structural formulae. For example, forIn other words, two R groups are the same group. For->And->The R groups in the former and the latter formulae may be the same or different.

C1 alkyl represents a carbon number of 1 contained therein, and C20 alkyl represents a carbon number of 20 contained therein. Similarly, n in Cn represents the number of carbon atoms.

The alkyl group is a saturated hydrocarbon group. As an example, C1 alkyl is-CH ₃ C2 alkyl is-CH ₂ CH ₃ 。

Alkoxy groups are composed of one alkyl group and one oxygen atom. As an example, C1 alkoxy is-OCH ₃ 。

Alkenyl groups can be considered as hydrocarbon groups in which one or more hydrogen atoms are missing from the olefin molecule. As an example, c2 alkenyl is ch2=ch-.

Alkenyloxy radicalIs composed of an alkenyl group and an oxygen atom. As an example, C2 alkenyloxy is-och=ch ₂ 。

Acyl is- (c=o) -. As an example, C2 acyl is acetyl CH ₃ -CO-。

R1, R2, R3, R4, R5, R6 each independently comprise at least one of the following substituted or unsubstituted groups: hydrogen, C1-C20 alkyl or alkoxy, C2-C20 alkenyl or alkenyloxy, C2-C20 alkynyl or alkynyloxy, C3-C20 cycloalkyl or epoxyalkyl, C6-C20 aryl, C1-C20 cyano, C1-C20 amino, C2-C20 ether linkage, C1-C20 ureido, C1-C20 carboxylate, C1-C20 sulfonate, C1-C20 isocyanate, C1-C20 thiocyanate, C4-C20 piperazinyl, C1-C20 silane, and the substituent comprises halogen elements.

The Si-O bond in the oxygen-containing silane compound can remove proton hydrogen generated by solvolysis, can reduce the risk of reaction between the proton hydrogen and the positive electrode interface, plays a certain role in protecting the positive electrode interface, and is favorable for forming a uniform and compact electrolyte interface film. Thus, the cycle life of the battery monomer is prolonged, the internal resistance of the battery monomer in the long-term charge-discharge cycle process is reduced, and the gas production of the battery monomer is reduced.

Alternatively, the phosphine group is not included in the group of R6, or, alternatively, the P element is not included in the group of R6.

The alkyl, alkoxy, acyl, amino, isocyanate, and other groups in the embodiments of the present application have popular explanations in the art, and are not described herein.

The mass content A of the oxygen-containing silane compound and the mass content B of the ethylene carbonate based on the total mass of the electrolyte satisfy the following conditions: a is more than or equal to 0.01 and B is more than or equal to 0.5. For example, A: B is 0.01,0.02,0.05,0.1,0.3,0.5 or any value within the above range.

Under the condition that the ratio A to the ratio B is not less than 0.01, the oxygen-containing silane compound in the electrolyte has proper mass content, is favorable for forming a uniform, stable and compact electrolyte interface film on the positive electrode, is favorable for reducing the DCR growth of the battery monomer in the long-time charge and discharge cycle process, can improve the cycle life of the battery monomer and reduce the gas production in the battery monomer. That is, the risk that the improvement of the gas production and the cycle performance is not obvious due to the too small mass content a of the alkoxysilane compound can be reduced, and the risk that the gas production of the battery cell is deteriorated due to the too large mass content B of the ethylene carbonate can be reduced.

Under the condition that the ratio A to the ratio B is not more than 0.5, the ethylene carbonate in the electrolyte has proper mass content, thereby being beneficial to improving the conductivity of the electrolyte, and simultaneously, a relatively uniform and compact SEI film can be formed, and the cycle performance of the battery monomer is improved. That is, the risk of an increase in interfacial resistance due to an excessively thick CEI film resulting from an excessively large mass content a of the alkoxysilane compound can be reduced, and the risk of an increase in resistance of the battery cell due to a poor conductivity of the electrolyte resulting from an excessively small mass content B of the ethylene carbonate can be reduced.

Therefore, by setting A to be more than or equal to 0.01 and B to be more than or equal to 0.5, the battery monomer has lower internal resistance increase rate, higher cycle life and lower gas yield.

In some embodiments, the mass content a of the alkoxysilane compound and the mass content B of the ethylene carbonate based on the total mass of the electrolyte satisfy: a is more than or equal to 0.03 and B is more than or equal to 0.3. For example, A: B is 0.03,0.04,0.05,0.08,0.1,0.2,0.3 or any value within the above range. Thus, the method is beneficial to reducing the DCR growth rate of the battery monomer, improving the gas production condition of the battery monomer and prolonging the cycle life of the battery monomer.

In some embodiments, the mass content a of the alkoxysilane compound, based on the total mass of the electrolyte, satisfies: a is more than or equal to 0.3wt% and less than or equal to 2.5wt%, and optionally, A is more than or equal to 1wt% and less than or equal to 1.5wt%. Thus, a compact and stable solid electrolyte membrane (CEI) can be effectively formed at the interface of the anode, the side reaction of the anode and the electrolyte is reduced, the cycling stability of the battery is conveniently improved, the DCR growth in the cycling process of the battery is reduced, and the gas production in high-temperature storage is improved.

A may be 0.3wt%,0.4wt%,0.8wt%,1wt%,1.5wt%,2wt%,2.5wt% or any value within the above range.

In some embodiments, the mass content B of the ethylene carbonate, based on the total mass of the electrolyte, satisfies: b is more than or equal to 5% and less than or equal to 30% by weight, preferably more than or equal to 5% and less than or equal to 16% by weight. The ethylene carbonate has higher dielectric constant, is beneficial to dissociation of lithium ions and is beneficial to improving the conductivity of the electrolyte. In the charge and discharge process of the battery monomer, in addition, the ethylene carbonate is locally decomposed on the surface of the negative electrode, so that a solid electrolyte interface film can be formed on the surface of the negative electrode, the negative electrode is protected, and the cycle performance of the battery is improved.

B may be 5wt%,8wt%,10wt%,16wt%,20wt%,30wt% or any value within the above range.

In some embodiments, the electrolyte further comprises an electrolyte salt, the mass content B of ethylene carbonate and the mass content C of electrolyte salt, based on the total mass of the electrolyte, satisfying: b is more than or equal to 1.2, C is less than or equal to 2.5; alternatively, 1.5.ltoreq.B.ltoreq.C.ltoreq.2.2.

For example, B: C is 1.2,1.4,1.5,1.6,1.8,2.1,2.2,2.3,2.4,2.5 or any value within the above range.

The electrolyte salt may be a lithium salt, in which case the electrolyte is the electrolyte in a lithium ion battery cell.

The electrolyte salt molecules may form solvated structures with the solvent molecules, i.e. the surroundings of the electrolyte salt molecules may attract a certain number of solvent molecules. For example, the electrolyte salt is LiPF ₆ The solvent is Ethylene Carbonate (EC), dissociated Li ⁺ Tends to coordinate with EC having a relatively high dielectric constant, typically one Li ⁺ Coordination will occur with 2-4 ECs, thereby reducing the risk of oxidation of EC molecules at the positive electrode.

In this embodiment, in the case where the mass content B of the ethylene carbonate and the mass content C of the electrolyte salt satisfy the above ranges, the EC molecules can be attracted to the surroundings by the electrolyte salt molecules, so that the risk of the EC being oxidized at the positive electrode can be reduced.

In some embodiments, the mass content C of the electrolyte salt, based on the total mass of the electrolyte, satisfies: c is more than or equal to 8wt% and less than or equal to 17wt%; alternatively, 10wt% or more and 17wt% or less of C. Thus, the electrolyte has proper ionic conductivity and the battery monomer has proper internal resistance.

C may be 8wt%,9wt%,10wt%,12wt%,16wt%,17wt% or any value within the above range.

In some embodiments, the electrolyte salt comprises: at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalato phosphate, lithium bisoxalato borate, or lithium difluorooxalato borate. In this way, the electrolyte salt is conveniently selected according to flexibility.

In the electrolyte, the electrolyte salt exists in the form of cations and anions. In determining the type of the electrolyte salt, the determination may be made by detecting the form of the anion. For example, lithium hexafluorophosphate as PF in electrolyte ₆ ^- And Li (lithium) ⁺ Is present in the form of (c).

In some embodiments, the electrolyte salt comprises lithium hexafluorophosphate. Wherein the chemical formula of the lithium hexafluorophosphate is LiPF ₆ 。

In some embodiments, the oxygen-containing silane compound includes: at least one of chloro (dimethyl) methoxy silane, divinyl tetramethyl disiloxane, diethoxymethyl vinyl silane, dimethoxy methyl vinyl silane, trimethoxy silane, n-hexadecyl trimethoxy silane, 3-chloroisobutyl trimethoxy silane, (3-aminopropyl) trimethoxy silane, 3-piperazinyl propyl trimethoxy silane, triethoxy silane, propyl triethoxy silane, n-octyl triethoxy silane, (3-glycidoxypropyl) triethoxy silane, phenyl triethoxy silane, 2-cyanoethyl triethoxy silane, diethylaminomethyl triethoxy silane, 3-aminopropyl triethoxy silane, 3-ureidopropyl triethoxy silane, 3-isocyanatopropyl triethoxy silane, 3-thiocyanopropyltriethoxy silane, vinyltris (trimethylsiloxy) silane, vinyltris [ (1-methylvinyl) oxy ] silane, vinyltris (2-methoxyethoxy) silane, triacetoxyethyl silane, methyltriacetoxy silane, tetramethoxy silane, tetraphenoxy silane.

The above-mentioned oxygen-containing silane compound has a relatively suitable solubility in a solvent, and is convenient for exerting the function of the oxygen-containing silane compound.

In some embodiments, the oxygen-containing silane compound includes: at least one of vinyltris (trimethylsiloxy) silane, vinyltris [ (1-methylvinyl) oxy ] silane, and vinyltris (2-methoxyethoxy) silane.

The oxygen-containing silane compound and the EC solvent have good matching effect, and the battery monomer has higher circulation capacity retention rate and lower gas yield.

In some embodiments, the solvent in the electrolyte may include, in addition to the Ethylene Carbonate (EC): propylene Carbonate (PC), fluoroethylene carbonate (FEC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene Carbonate (BC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethylsulfone (MSM), methylsulfone (EMS) and diethylsulfone (ESE).

In some embodiments, the additives in the electrolyte may include other additives in addition to the oxygen-containing silane compound, such as negative electrode film-forming additives, positive electrode film-forming additives, additives capable of improving certain properties of the battery, such as additives that improve overcharge properties of the battery, additives that improve high or low temperature properties of the battery, and the like.

In some embodiments, the mass content D of HF in the electrolyte satisfies: d is less than or equal to 150ppm. For example, D is 150ppm,100ppm,50ppm or any value within the above range.

HF can adversely affect the positive electrode-electrolyte interface (CEI) film, causing the positive electrode active material to decompose or corrode, which is detrimental to the improvement of the cycle life of the battery cell. By setting the mass content D of HF to 150ppm or less, it is advantageous to improve the cycle life of the battery cell.

In some embodiments, the mass content E of water in the electrolyte satisfies: e is less than or equal to 20ppm. For example, E is 20ppm,10ppm or any value within the above range.

The electrolyte of the embodiment of the application is a non-aqueous electrolyte, but in the process of the configuration of the electrolyte, H in the air is contacted ₂ O, resulting in a smaller content of water in the electrolyte.

In this embodiment, the quality content of water in the electrolyte is controlled, so that the integrity of the CEI film can be improved, the occurrence of side reactions can be reduced, and the cycle performance of the battery cell can be improved.

[ Positive electrode sheet ]

The positive pole piece comprises a positive current collector and a positive film layer arranged on the positive current collector.

The positive current collector can be a metal foil or a composite current collector. For example, the positive electrode current collector may be aluminum foil.

The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

The positive electrode film layer includes a positive electrode active material. The positive electrode active material may be a positive electrode active material for a battery known in the art.

The positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.

The positive electrode film layer may further optionally include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[ negative electrode sheet ]

The negative pole piece comprises a negative pole current collector and a negative pole film layer arranged on the negative pole current collector.

The negative current collector may be a metal foil or a composite current collector. The negative electrode current collector may be copper foil. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

The negative electrode film layer includes a negative electrode active material therein. The negative electrode active material may employ a negative electrode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may include at least one of elemental silicon, a silicon oxygen compound, a silicon carbon compound, a silicon nitrogen compound, and a silicon alloy. The tin-based material may include at least one of elemental tin, a tin oxide, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

The negative electrode film layer may further optionally include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[ isolation Membrane ]

The isolating film is used for isolating the positive pole piece and the negative pole piece. The embodiment of the application has no special limitation on the type of the isolating membrane, and any known porous isolating membrane with good chemical stability and mechanical stability can be selected.

The material of the isolating film may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

The positive electrode sheet, the negative electrode sheet and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

[ Battery cell ]

The embodiment of the application provides a battery cell, which comprises the electrolyte in the embodiment.

In some embodiments, the battery cell further includes a positive electrode sheet comprising a positive electrode active material, the positive electrode active material including a transition metal oxide of lithium.

In some embodiments, the transition metal oxide of lithium has the formula Li _a Ni _b Co _c M _d N _e O _f A _g Wherein a is more than or equal to 0.8 and less than or equal to 1.3,0.1, b is more than or equal to less than or equal to 0.98,0.01 and less than or equal to 0.3, d is more than or equal to 0.01 and less than or equal to 0.6,0 and less than or equal to 0.5, f is more than or equal to 0 and less than or equal to 2, g is more than or equal to 0 and less than or equal to 2, M comprises at least one of Mn or Al, N comprises at least one of B, W, si, ti, zr, sr, sn, tb, nb, sb, se, ce or Te, and A comprises at least one of S, N, P, F, cl, br or I.

In some embodiments, b+c+d+e=1 and f+g=2. For example, when a is S, f+g=2. In other embodiments, f+g may also be less than 2.

A may be a doping element, which may occupy the position of the O element. The N element may be a doping element, which may occupy the position of the M element.

a may be 0.8,1,1.2,1.3 or any value within the above range, b may be 0.1,0.2,0.4,0.6,0.98 or any value within the above range, c may be 0.01,0.1,0.2,0.3 or any value within the above range, d may be 0.01,0.05,0.1,0.3,0.5,0.6 or any value within the above range, e may be 0,0.2,0.4,0.5 or any value within the above range, f may be 0,0.5,0.8,1,1.2,2 or any value within the above range, and g may be 0,0.5,0.8,1,1.2,2 or any value within the above range.

As an example, the transition metal oxide of lithium is a ternary material, such as LiNi _0.6 Co _0.2 Mn _0.2 O ₂ 、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ 、LiNi _0.5 Co _0.2 Al _0.3 O ₂ The method comprises the steps of carrying out a first treatment on the surface of the The transition metal oxide of lithium may also be a doped ternary material, such as LiNi _0.5 Co _0.3 Mn _0.1 Ti _0.1 O ₂ Etc.

In some embodiments, the lithium transition metal oxide is a lithium-rich manganese-based material having the formula nLi ₂ MnO ₃ ·(1-n)LiM ³ O ₂ ，M ³ Comprises at least one of Co, ni and Mn, and n is more than 0 and less than 1. For example, the transition metal oxide of lithium is Li [ Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ 。

In the positive electrode sheet, the battery cell, or the power consumption device, li is released and consumed during the charge and discharge process, and the molar content of Li is different when the battery cell is discharged to different states. In the listing of the positive electrode material, the molar content of Li is in the initial state of the material, namely the state before charging, and the molar content of Li is changed after charge and discharge cycles when the positive electrode material is applied to a battery system.

In the examples of the positive electrode material according to the present application, the molar content of O is only a theoretical state value, and the molar content of oxygen changes due to lattice oxygen release, and the actual molar content of O floats, so that the measured oxygen element content f in the positive electrode active material may be 2 or less.

In some embodiments, the volume average particle diameter Dv50 of the positive electrode active material satisfies: dv50.ltoreq.3μm.ltoreq.15μm, alternatively, dv50.ltoreq.5μm.ltoreq.10μm. For example, dv50 is 3 μm,4 μm,5 μm,6 μm,8 μm,10 μm,15 μm or any value within the above range.

As an example, the positive electrode active material is a ternary material, and the volume average particle diameter Dv50 of the ternary material satisfies: dv50 is less than or equal to 3 μm and less than or equal to 15 μm.

Under the condition that the average grain diameter of the positive electrode active material is not smaller than 3 mu m, the positive electrode active material has proper specific surface area, proper surface energy and less possibility of agglomeration and side reaction with electrolyte are reduced, and the risk of increasing the internal resistance of the battery monomer can be reduced, so that the risk of increasing the temperature caused by excessive energy accumulation in the charging and discharging process can be reduced, and the reliability of the battery monomer is improved. Under the condition that the volume average particle size of the positive electrode active material is not more than 15 mu m, the positive electrode active material has a proper specific surface area, the combination between the positive electrode active material and the current collector is firm, the risk that the positive electrode active material is separated from the current collector can be reduced, and the risk of local short circuit of a battery cell caused by the fact that the positive electrode active material is free in electrolyte and contacted with the negative electrode active material can be reduced.

In some embodiments, the mass content a of the alkoxysilane compound and the volume average particle diameter Dv50 of the positive electrode active material satisfy: 0.03 wt.%/μm.ltoreq.A: dv50.ltoreq.0.8 wt.%/μm, alternatively 0.05 wt.%/μm.ltoreq.A: dv50.ltoreq.0.3 wt.%/μm.

By limiting the relation between the mass content A of the oxygen-containing silane compound and the volume average particle diameter Dv50 of the positive electrode active material, the oxygen-containing silane compound A has proper mass content while the positive electrode active material has proper specific surface area, so that the side reaction between the positive electrode active material and the solvent can be further reduced, the gas yield of the battery monomer is reduced, the internal resistance growth rate of the battery monomer is reduced, the positive electrode interface is effectively protected, and the cycle performance of the battery monomer is improved.

Compared with the method only setting the volume average particle diameter Dv50 of the positive electrode active material or the mass content A of the oxygen-containing silane compound, the method setting the relationship between the mass content A of the oxygen-containing silane compound and the volume average particle diameter Dv50 of the positive electrode active material has the advantage that the oxygen-containing silane compound with proper mass content is arranged for the positive electrode active material per unit volume, thereby not only being beneficial to fully playing roles of the oxygen-containing silane compound and inhibiting the oxidation of a solvent, but also being beneficial to reducing the risk of excessively thick CEI film, and further being beneficial to improving the cycle performance of a battery cell.

In some embodiments, the battery cell is a lithium ion battery cell.

In some embodiments, the upper operating voltage of the battery cell is 4.5V. That is, the battery cell can operate at a voltage of 4.5V, and the battery cell has better cycle performance and less gas generation.

The shape of the battery cell is not particularly limited in the embodiment of the present application, and may be cylindrical, square or any other shape.

Fig. 1 is a schematic view of a battery cell according to an embodiment of the application. For example, as shown in fig. 1, the battery cell 3 is a square battery cell. The battery cell 3 includes a case 31, an end cap assembly 32, and an electrode assembly 33 disposed in the case 31, and an electrolyte is impregnated in the electrode assembly 33.

The electrode assembly 33 may be made of a positive electrode tab, a negative electrode tab, and a separator through a winding process or a lamination process.

The end cap assembly 32 includes electrode terminals 322, for example, as shown in fig. 1, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and one of which is a negative electrode terminal.

The battery cell 3 further includes a current collecting member 34, and the current collecting member 34 is used to connect the tab 331 and the electrode terminal 322 of the electrode assembly 33.

In some embodiments, the battery cells may be assembled into a battery module, and the number of battery cells included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

[ Battery ]

The embodiment of the application provides a battery, which comprises the battery cells in the embodiment. Fig. 2 is a schematic view of a battery according to an embodiment of the present application. As shown in fig. 2, the battery 5 may include a plurality of battery cells (not shown).

The battery unit 3 may be directly assembled into the battery 5, or may be assembled into a battery module, and then the battery 5 is assembled from a plurality of battery modules.

[ electric device ]

The embodiment of the application provides an electric device, which comprises the battery described in the embodiment.

Fig. 3 is a schematic diagram of an electrical device according to an embodiment of the application. As shown in fig. 3, the present application provides an electric device 6 including the battery in the above embodiment.

Optionally, the power utilization device may also be an energy storage device, a lighting device, a spacecraft, and the like, and embodiments of the present application include, but are not limited to, this.

Hereinafter, embodiments of the present application are described. The following examples are illustrative only and are not to be construed as limiting the application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Examples (example)

Example 1

In example 1, the electrolyte includes a ethylene carbonate solvent, an oxygen-containing silane compound additive, and an electrolyte salt. Wherein the additive is vinyl tri (2-methoxyethoxy) silane, and the electrolyte salt is LiPF ₆ . The mass content A of vinyltris (2-methoxyethoxy) silane was 1wt%, the mass content B of ethylene carbonate was 15wt%, and LiPF based on the total mass of the electrolyte ₆ The mass content C is 10wt%.

Examples 2 to 4

Examples 2-4 differ from example 1 in that: the mass content A of the oxygen-containing silane compound additive is different; accordingly, the values of A: B are different.

Examples 5 to 7

Examples 5-7 differ from example 1 in that: the mass content B of the ethylene carbonate solvent is different; accordingly, the values of A, B and C are different.

Examples 8 to 11

Examples 8-11 differ from example 1 in that: the mass content A of the oxygenated silane compound additive and the mass content B of the ethylene carbonate solvent are different; accordingly, the values of A, B and C are different.

Examples 12 to 14

Examples 12-13 differ from example 6 in that: the mass content C of the electrolyte salts is different; accordingly, the values of B: C are different. Example 14 differs from example 7 in that: the mass content C of the electrolyte salts is different; accordingly, the values of B: C are different.

Examples 15 to 17

Examples 15-17 differ from example 1 in that: the specific kind of the oxygen-containing silane compound of the additive varies.

Example 18

Example 18 differs from example 1 in that: the specific kind of electrolyte salt varies.

Examples 19 to 21

Examples 19-21 differ from example 4 in that: the volume average particle diameters Dv50 of the positive electrode active materials are different.

Example 22

Example 22 differs from example 1 in that: the mass content A of the oxygen-containing silane compound additive, the mass content B of the ethylene carbonate solvent, the mass content C of the electrolyte salt, and the volume average particle diameter Dv50 of the positive electrode active material are all different, and accordingly, the values of A: B, B: C, A: dv50 are different.

In examples 1 to 22, the positive electrode active material was LiNi _0.6 Co _0.2 Mn _0.2 O ₂ 。

Comparative example 1

Comparative example 1 differs from example 1 in that: the oxygen-containing silane compound additive is not included in the electrolyte. Wherein the mass content of the solvent EC is 15wt%, and the mass content of the electrolyte salt is 10wt%.

Comparative examples 2 to 3

Comparative examples 2 to 3 differ from example 1 in that: a and B are different.

Table 1 experimental parameters of examples and comparative examples

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Table 2 test results of examples and comparative examples

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[ preparation of Battery cell ]

(1) Preparing a positive electrode plate: dissolving an anode active material, a binder polyvinylidene fluoride (PVDF) and a conductive agent (acetylene black) in a solvent N-methylpyrrolidone (NMP) according to a mass ratio of 97:2:1, and fully stirring and uniformly mixing to prepare anode slurry; and uniformly coating the anode slurry on an anode current collector aluminum foil, and then drying, cold pressing and cutting to obtain an anode plate.

(2) Preparing a negative electrode plate: dissolving negative electrode active material artificial graphite, conductive agent acetylene black, binder Styrene Butadiene Rubber (SBR) and thickener sodium carboxymethylcellulose (CMC-Na) in deionized water according to the mass ratio of 96:1.5:1.5:1.0, and fully stirring and uniformly mixing to prepare negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector copper foil, and then drying, cold pressing and cutting to obtain a negative electrode plate.

(3) Isolation film: a polypropylene film is used.

(4) Preparation of electrolyte: in a vacuum glove box (argon atmosphere, H ₂ O＜0.1ppm，O ₂ Less than 0.1 ppm) the oxygen-containing silane compound additive and the electrolyte salt are dissolved in a mixed solvent of ethylene carbonate EC and ethylmethyl carbonate EMC according to corresponding proportion, and are uniformly stirred to obtain the electrolyte.

(5) Preparation of a lithium ion battery: sequentially stacking and winding the positive electrode plate, the isolating film and the negative electrode plate to obtain an electrode assembly; and placing the electrode assembly into an outer package, adding the prepared electrolyte, and performing the procedures of packaging, standing, formation, aging and the like to obtain the lithium ion battery cell.

It should be noted that the mass content of each component (for example, the mass content of the additive, the mass content of the electrolyte, the mass content of the solvent), the volume average particle diameter, the internal resistance of the battery cell, the gas generating performance of the battery cell, the cycle performance of the battery cell, and the like in the electrolyte according to the embodiment of the present application are common knowledge in the art, and have the meaning that they are known in the art and can be measured by the test methods and apparatuses known in the art.

[ test of cycle Performance of Battery cell ]

And (3) placing the prepared lithium ion battery monomer at 25 ℃ for 5 minutes, charging to 4.5V at a constant current with a rate of 0.5C, charging to a current of less than or equal to 0.05C at a constant voltage, placing for 5 minutes, and discharging to 2.8V at a constant current with a rate of 1C, wherein the discharge capacity is recorded as the discharge capacity of the lithium ion battery monomer in the 1 st cycle. And carrying out 600-cycle charge and discharge tests on the lithium ion battery monomer according to the method, and recording the discharge capacity of each cycle.

The capacity retention rate after 600 cycles of 0.5C/1C at 25 ℃ of the lithium ion battery cell=600 th cycle discharge capacity/1 st cycle discharge capacity×100%.

[ test of DCR growth Rate of Battery cell ]

In the embodiment of the application, the internal resistance of the battery is represented by direct current impedance (Direct Current Internal Resistance, DCR), and a testing method of the DCR is described below.

Charging the battery cell at 25deg.C constant current to 4.5V, charging at constant voltage of 4.5V to current of 0.05C, discharging at 0.5C for 1 hr, discharging at 4C current for 30s, recording initial voltage V1 at the beginning of discharge and voltage V2 at 30s, and initial DCR= (V1-V2)/I ₁ ，I ₁ The corresponding current is 4C.

Then, the battery cell was charged to 4.5V at a constant current of 0.5C, charged to a cutoff current of 0.05C at a constant voltage of 4.5V, and then discharged to 2.8V at a constant current of 1C, which is one charge-discharge cycle. This cycle is repeated for the same cell.

After 600 cycles, the battery is singly usedThe body was charged to 4.5V at a constant current of 0.33C, charged to a current of 0.05C at a constant voltage of 4.5V, discharged for 1 hour at 0.5C, discharged for 30s at 4C, and the initial voltage V3 at the start of discharge and the voltage V4 at 30s at discharge were recorded to calculate dcr= (V3-V4)/I at circle 600 ₂ ，I ₂ The corresponding current is 4C.

Cyclic DCR increase rate (%) = (DCR at round 600-initial DCR)/initial dcr×100%.

[ test of gas production Performance of Battery cell ]

In the embodiment of the application, the gas production performance of the battery cell is represented by the volume expansion rate of the battery cell, and the method for testing the volume expansion rate is described below.

After fully charging the battery cells to 4.5V at 1C, the battery cells were allowed to stand in an incubator at 70 ℃ for 30 days. And measuring the initial volume of the battery monomer and the volume after standing for 30 days by a drainage method to obtain the volume expansion rate of the battery monomer.

The volume expansion ratio (%) = [ (volume after 30 days of standing/initial volume) -1] ×100% of the battery cell. [ test of Components in electrolyte ]

The solvent and the additive can be determined by gas chromatography, and the components and the content can be quantitatively analyzed by referring to the standard GB/T9722-2006. The electrolyte salt can quantitatively analyze the concentration of inorganic components/lithium salt in the electrolyte by an ion chromatography analysis method with reference to a standard JY/T020-1996.

[ test of HF content in electrolyte ]

Adopting acid-base titration method hydrofluoric acid content analysis (SYA); determination of the content of 5.10 free acid of the reference standard HG/T4067-2015 lithium hexafluorophosphate electrolyte; in a dry environment, titrating the free acid in the electrolyte with a triethylamine standard solution, wherein the free acid is calculated according to the HF content:

HF(ppm)=（V2-V1)/1000*C*20/m*1000000=（V2-V1)*C/m*20,000；

wherein: c-the concentration of SYA standard solution, 0.02mol/L;

v1-volume reading of burette before beginning titration, mL;

v2-after the electrolyte sample is added, when titration is carried out to an end point, the volume of the burette reads and the volume of the burette is mL;

20-molar mass of HF, g/mol;

m-the amount of electrolyte weighed, g;

20000-coefficient converted to μg/g.

[ H in electrolyte solution ] ₂ Testing of O content]

The measurement is carried out by the Karl Fischer coulomb method.

Injecting electrolyte into the balanced electrolytic cell, indicating that the electrode detects H ₂ After O, electrode oxidation I occurs ^- Is I ₂ ，I ₂ And H ₂ O produces a quantitative chemical reaction to calculate the water content; measuring the water content of 5.9 of the reference standard HG/T4067-2015 lithium hexafluorophosphate electrolyte; i ₂ And H ₂ Quantitative chemical reaction formula of O: i ₂ +H ₂ O+SO ₂ +3C ₅ H ₅ N=2C ₅ H ₅ N·HI+C ₅ H ₅ N·SO ₃ The method comprises the steps of carrying out a first treatment on the surface of the The amount of water was calculated from the amount of iodine consumed.

[ test of volume average particle diameter ]

Dv50: the particle diameter of 50% of the total volume is larger than this value, and the particle diameter of 50% of the total volume is smaller than this value, dv50 representing the median particle size of the powder. In the present application Dv50 is determined by the particle size analyzer-laser diffraction method, and specifically, the measurement is carried out by the manufacturer's instructions by using a laser diffraction scattering particle size analyzer with reference to standard GB/T19077-2016, unless otherwise specified.

The addition of an oxygen-containing silane compound to the electrolyte, as shown in examples 1-22 and comparative example 1, is advantageous in improving the cycle life of the battery cell and reducing the volume expansion rate of the battery cell during long-term charge-discharge cycles.

In the case where the ratio of the mass content of the oxygen-containing silane compound to the mass content of the ethylene carbonate is more than 0.5, as shown in the combination of examples 1 to 22 and comparative examples 2 to 3, the battery cell has a high internal resistance increase rate and the cycle performance of the battery cell is poor; under the condition that the ratio of the mass content of the oxygen-containing silane compound to the mass content of the ethylene carbonate is smaller than 0.01, the battery monomer has larger volume expansion rate, and the cycle performance of the battery monomer is poor. Therefore, by setting the ratio of the mass content of the oxygen-containing silane compound to the mass content of the ethylene carbonate to be 0.01-0.5, the battery cell has a lower internal resistance increase rate and a smaller volume expansion rate, and also has a higher circulation capacity retention rate.

As shown in examples 1, 3 to 4 and 2, the mass content of the oxygen-containing silane compound additive in the electrolyte was reasonably set so that the battery cell had a small DCR increase rate and a low volume expansion rate at the same time when the ratio of the mass content of the oxygen-containing silane compound to the mass content of the ethylene carbonate was 0.03 or more. In combination with the embodiments 1, 6, 5 and 7, the mass content of the ethylene carbonate is reasonably set, and the ethylene carbonate and the electrolyte salt form a solvated structure, so that the risk of oxidizing the ethylene carbonate at the positive electrode is reduced, the occurrence of side reaction can be reduced, and the cycle performance of the battery monomer is improved. As shown in examples 6 and 12 to 13 or in examples 14 and 7, the mass content of the electrolyte salt is reasonably set so that the ratio of the mass content of the ethylene carbonate to the mass content of the electrolyte salt is in the range of 1.5 to 2.2, which is beneficial to reducing the capacity fade and DCR growth rate during the battery cell cycle and simultaneously beneficial to inhibiting the volume expansion of the battery cell at high temperature.

In combination with examples 1, 3 and 11, when the mass content A of the additive is 0.4wt% to 1.5wt%, the mass content B of the solvent EC is 5wt% to 16wt%, the mass content C of the electrolyte salt is 10wt% to 16wt%, and the volume average particle diameter Dv50 of the positive electrode active material is 5 μm to 10 μm, the battery monomer corresponding to the examples meeting all ranges simultaneously has higher cycle capacity retention rate, lower DCR growth rate and smaller volume expansion rate, so that the battery monomer has better comprehensive performance.

As shown in connection with examples 15-17, the examples of the present application are applicable to a variety of oxygen-containing silane compounds; as shown in connection with examples 1 and 18, the present examples are applicable to a variety of electrolyte salts. In the case where the volume average particle diameter of the positive electrode active material and the mass content of the additive satisfy the appropriate ranges, as shown in the combination of examples 19 to 22, it is advantageous to suppress occurrence of side reactions, and the battery cell has a high cycle life. Specifically, as shown in combination with examples 1 and 2, or as shown in combination with examples 7 and 8, the battery cell has better cycle and gassing properties than when only the volume average particle diameter of the positive electrode active material is set, while the relationship between the additive mass content and the volume average particle diameter of the positive electrode active material is set. As shown in examples 4, 21 and examples 19 to 20, the battery cell has better cycle performance and lower volume expansion ratio than the case where only the mass content of the additive was set while adjusting the relationship between the mass content of the additive and the volume average particle diameter of the positive electrode active material so as to fall within the respective ranges.

In the embodiment of the application, the content of HF and water in the electrolyte is related to the environment in which the electrolyte is disposed, and less related to the mass content of additives, solvents EC and electrolyte salts.

It should be noted that other solvent substances may be added to the electrolyte in the embodiment of the present application, and the electrolyte may be also suitable for other positive electrode active materials.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

1. An electrolyte, comprising:

a solvent comprising ethylene carbonate;

an additive comprising an oxygen-containing silane compound;

the mass content A of the oxygen-containing silane compound and the mass content B of the ethylene carbonate satisfy the following conditions based on the total mass of the electrolyte: a is more than or equal to 0.01 and B is more than or equal to 0.5;

，/>，/>，/>，

Wherein R comprises: at least one of C1-C20 alkyl or alkoxy, C2-C20 alkenyl or alkenyloxy, C1-C20 acyl, C2-C20 ether linkage, C1-C20 silyl or C6-C20 aryl;

R ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ each independently includes at least one of the following substituted or unsubstituted groups: hydrogen, C1-C20 alkyl or alkoxy, C2-C20 alkenyl or alkenyloxy, C2-C20 alkynyl or alkynyloxy, C3-C20 cycloalkyl or epoxyalkyl, C6-C20 aryl, C1-C20 cyano, C1-C20 amino, C2-C20 ether linkage, C1-C20 ureido, C1-C20 carboxylate, C1-C20 sulfonate, C1-C20 isocyanate, C1-C20 thiocyanate, C4-C20 piperazinyl, C1-C20 silane, and the substituent comprises halogen elements.

2. The electrolyte according to claim 1, wherein the mass content a of the oxygen-containing silane compound and the mass content B of the ethylene carbonate satisfy, based on the total mass of the electrolyte: a is more than or equal to 0.03 and B is more than or equal to 0.3.

3. The electrolyte according to claim 1, wherein the mass content a of the oxygen-containing silane compound, based on the total mass of the electrolyte, satisfies: a is more than or equal to 0.3wt% and less than or equal to 2.5wt%.

4. The electrolyte according to claim 3, wherein the mass content a of the oxygen-containing silane compound based on the total mass of the electrolyte satisfies: a is more than or equal to 1 weight percent and less than or equal to 1.5 weight percent.

5. The electrolyte according to claim 1, wherein the mass content B of the ethylene carbonate satisfies, based on the total mass of the electrolyte: b is more than or equal to 5wt% and less than or equal to 30wt%.

6. The electrolyte according to claim 5, wherein the mass content B of the ethylene carbonate satisfies, based on the total mass of the electrolyte: b is more than or equal to 5wt% and less than or equal to 16wt%.

7. The electrolyte of claim 1, further comprising an electrolyte salt, wherein the mass content B of the ethylene carbonate and the mass content C of the electrolyte salt satisfy, based on the total mass of the electrolyte: b is more than or equal to 1.2 and C is more than or equal to 2.5.

8. The electrolyte according to claim 7, wherein the mass content B of the ethylene carbonate and the mass content C of the electrolyte salt satisfy, based on the total mass of the electrolyte: b is more than or equal to 1.5, and C is more than or equal to 2.2.

9. The electrolyte according to claim 7, wherein the mass content C of the electrolyte salt, based on the total mass of the electrolyte, satisfies: c is more than or equal to 8wt% and less than or equal to 17wt%.

10. The electrolyte according to claim 9, wherein the mass content C of the electrolyte salt, based on the total mass of the electrolyte, satisfies: c is more than or equal to 10wt% and less than or equal to 17wt%.

11. The electrolyte of claim 7 wherein the electrolyte salt comprises: at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalato phosphate, lithium bisoxalato borate, or lithium difluorooxalato borate.

12. The electrolyte of claim 11 wherein the electrolyte salt comprises lithium hexafluorophosphate.

13. The electrolyte of claim 1, wherein the oxygen-containing silane compound comprises: at least one of chloro (dimethyl) methoxy silane, divinyl tetramethyl disiloxane, diethoxymethyl vinyl silane, dimethoxy methyl vinyl silane, trimethoxy silane, n-hexadecyl trimethoxy silane, 3-chloroisobutyl trimethoxy silane, (3-aminopropyl) trimethoxy silane, 3-piperazinyl propyl trimethoxy silane, triethoxy silane, propyl triethoxy silane, n-octyl triethoxy silane, (3-glycidoxypropyl) triethoxy silane, phenyl triethoxy silane, 2-cyanoethyl triethoxy silane, diethylaminomethyl triethoxy silane, 3-aminopropyl triethoxy silane, 3-ureidopropyl triethoxy silane, 3-isocyanatopropyl triethoxy silane, 3-thiocyanopropyltriethoxy silane, vinyltris (trimethylsiloxy) silane, vinyltris [ (1-methylvinyl) oxy ] silane, vinyltris (2-methoxyethoxy) silane, triacetoxyethyl silane, methyltriacetoxy silane, tetramethoxy silane, tetraphenoxy silane.

14. The electrolyte of claim 13, wherein the oxygen-containing silane compound comprises: at least one of vinyltris (trimethylsiloxy) silane, vinyltris [ (1-methylvinyl) oxy ] silane, and vinyltris (2-methoxyethoxy) silane.

15. Electrolyte according to claim 1, characterized in that the mass content D of HF in the electrolyte satisfies: d is less than or equal to 150ppm.

16. Electrolyte according to any one of claims 1-15, characterized in that the mass content E of water in the electrolyte satisfies: e is less than or equal to 20ppm.

17. A battery cell comprising the electrolyte of any one of claims 1-16.

18. The battery cell of claim 17, further comprising a positive electrode sheet comprising a positive electrode active material comprising a transition metal oxide of lithium.

19. The battery cell of claim 18, wherein the lithium transition metal oxide has a formula of Li _a Ni _b Co _c M _d N _e O _f A _g Wherein a is more than or equal to 0.8 and less than or equal to 1.3,0.1, b is more than or equal to less than or equal to 0.98,0.01 and less than or equal to 0.3, d is more than or equal to 0.01 and less than or equal to 0.6,0 and less than or equal to 0.5, f is more than or equal to 0 and less than or equal to 2, g is more than or equal to 0 and less than or equal to 2, M comprises at least one of Mn or Al, N comprises at least one of B, W, si, ti, zr, sr, sn, tb, nb, sb, se, ce or Te, and A comprises at least one of S, N, P, F, cl, br or I.

20. The battery cell according to claim 18 or 19, wherein the positive electrode active material has a volume average particle diameter Dv50 that satisfies: dv50 is less than or equal to 3 μm and less than or equal to 15 μm.

21. The battery cell according to claim 20, wherein the positive electrode active material has a volume average particle diameter Dv50 that satisfies: dv50 is less than or equal to 5 μm and less than or equal to 10 μm.

22. The battery cell according to claim 20, wherein the mass content a of the oxygen-containing silane compound and the volume average particle diameter Dv50 of the positive electrode active material satisfy: 0.03 wt.%/μm.ltoreq.A.Dv50.ltoreq.0.8 wt.%/μm.

23. The battery cell according to claim 22, wherein the mass content a of the oxygen-containing silane compound and the volume average particle diameter Dv50 of the positive electrode active material satisfy: 0.05 wt.%/μm.ltoreq.A.Dv50.ltoreq.0.3 wt.%/μm.

24. A battery comprising a cell according to any one of claims 17-23.

25. An electrical device comprising the battery of claim 24.