CN118281347A - Electrolyte, secondary battery and electronic device - Google Patents

Abstract

The application provides an electrolyte, a secondary battery and an electronic device, wherein the electrolyte comprises: an organic solvent and an electrolyte salt, wherein the organic solvent comprises a nitrile solvent, and the ortho carbon atom of a cyano group in the nitrile solvent is a quaternary carbon atom. According to the application, the ortho-carbon atom of the cyano group in the nitrile solvent in the electrolyte is a quaternary carbon atom, and the nitrile solvent has higher stability relative to the battery cathode, so that the electrolyte can not only utilize the advantages of high dielectric constant, low viscosity and high flash point of the nitrile solvent, but also reduce the influence on the battery performance due to incompatibility of the nitrile solvent and the battery cathode.

Description

Electrolyte, secondary battery and electronic device

Technical Field

The present application relates to the field of battery technology, and in particular to electrolytes, secondary batteries and electronic devices.

Background technique

Nitrile solvents have high oxidation stability voltage, which can meet the working voltage window of mainstream battery positive electrode materials. In addition, nitrile solvents have high dielectric constant, low viscosity and high flash point, which ensure that the electrolyte system with nitrile solvents as the main solvent has high conductivity and high safety.

However, nitrile solvents are very likely to react with the highly reducing negative electrode in the battery, resulting in incompatibility between the negative electrode and the nitrile solvents. Therefore, nitrile solvents are currently difficult to use as the main solvent of the electrolyte and are generally added to the electrolyte in the form of additives.

Therefore, it is necessary to overcome the problem that nitrile solvents are incompatible with the battery negative electrode.

Summary of the invention

The present application provides an electrolyte, a secondary battery and an electronic device. The electrolyte can effectively improve the problem of incompatibility between the nitrile solvent and the negative electrode of the battery by selecting a special nitrile solvent.

In a first aspect, the present application provides an electrolyte solution, comprising: an organic solvent and an electrolyte salt, wherein the organic solvent comprises a nitrile solvent, and the ortho-carbon atom of the cyano group in the nitrile solvent is a quaternary carbon atom.

According to the present application, the ortho-carbon atom of the cyano group in the nitrile solvent in the electrolyte is a quaternary carbon atom, and the nitrile solvent has higher stability relative to the battery negative electrode. Therefore, the electrolyte can not only utilize the advantages of the nitrile solvent itself, such as high dielectric constant, low viscosity and high flash point, but also reduce the influence of the incompatibility of the nitrile solvent with the battery negative electrode on the battery performance.

In some embodiments, the volume percentage of the nitrile solvent in the organic solvent is greater than 5%; optionally, the volume percentage of the nitrile solvent in the organic solvent is 10% to 99%.

In some embodiments, the nitrile solvent includes at least one of a mononitrile solvent, a dinitrile solvent or a trinitrile solvent; optionally, the nitrile solvent includes a mononitrile solvent.

In some embodiments, the nitrile solvent includes a compound as shown in Formula I,

Here, R ₁ , R ₂ , and R ₃ each independently represent a substituent other than H.

In some embodiments, R ₁ , R ₂ , and R ₃ are each independently represented by at least one of a C1-C10 substituted or unsubstituted alkyl group, a C6-C30 substituted or unsubstituted aromatic group, or a halogen atom; alternatively, R ₁ , R ₂ , and R ₃ are each independently represented by a C1-C10 substituted or unsubstituted alkyl group; alternatively, R ₁ , R ₂ , and R ₃ are each independently represented by a C1-C5 unsubstituted alkyl group.

In some embodiments, R ₁ , R ₂ , and R ₃ are all methyl groups.

In some embodiments, the organic solvent also includes at least one of linear carbonates, cyclic carbonates, and ether solvents; optionally, the organic solvent also includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, fluoroethylene carbonate, and vinylene carbonate.

In some embodiments, the concentration of the electrolyte salt in the electrolyte is no greater than 2 mol/L; optionally, the concentration of the electrolyte salt in the electrolyte is no greater than 1 mol/L.

In a second aspect, the present application provides a secondary battery, comprising the electrolyte described in any embodiment of the first aspect.

In a third aspect, the present application provides an electronic device comprising the secondary battery described in any embodiment of the second aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

FIG1 is a diagram of the coulombic efficiency of a lithium-copper half-cell tested with the electrolyte configured in Example 1.

FIG2 is a diagram of the coulombic efficiency of a lithium-copper half-cell tested with the electrolyte configured in Comparative Example 1.

The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments.

Detailed ways

The various embodiments or implementation schemes in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the implementation or examples are included in at least one implementation or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more implementations or examples in a suitable manner.

In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

The term "alkyl" encompasses straight and branched alkyl groups. For example, the alkyl group may be a C5-C500 alkyl group, a C20-C400 alkyl group, a C1-C50 alkyl group, a C1-C40 alkyl group, a C1-C30 alkyl group, a C1-C20 alkyl group, a C1-C12 alkyl group, a C1-C10 alkyl group, a C1-C6 alkyl group, a C1-C4 alkyl group. In some embodiments, the alkyl group includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, a pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a heptyl group, a cycloheptyl group, an octyl group, a cyclooctyl group, a nonyl group, and a decyl group. In addition, the alkyl group may be optionally substituted. The term "substituted alkyl group" refers to an alkyl group in which a hydrogen atom is partially or completely replaced by a substituent, and the term "unsubstituted alkyl group" refers to an alkyl group in which a hydrogen atom is not completely replaced by a substituent. The term "halogen atom" means a fluorine atom, a chlorine atom, a bromine atom, an iodine atom or the like.

The term "quaternary carbon atom" refers to a carbon atom that is not directly bonded to a hydrogen atom.

The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D) or 3H (tritium, T). In various embodiments, "hydrogen" may be 1H (protium, H).

At various places in this specification, substituents of compounds are disclosed in groups or ranges. It is expressly intended that such descriptions include every individual subcombination of the members of these groups and ranges. For example, it is expressly intended that the term "C1 to C10 substituted or unsubstituted alkyl" individually discloses C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C1 to C10, C1 to C9, C1 to C8, C1 to C7, C1 to C6, C1 to C5, C1 to C4, C1 to C3, C1 to C2, C2 to C10, C2 to C9, C2 to C8, C2 to C7, C2 to C6, C2 to C5, C2 to C4, C2 to C3, C3 to C10, C C3-C9, C3-C8, C3-C7, C3-C6, C3-C5, C3-C4, C4-C10, C4-C9, C4-C8, C4-C7, C4-C6, C4-C5, C5-C10, C5-C9, C5-C8, C5-C7, C5-C6, C6-C10, C6-C9, C6-C8, C6-C7, C7-C10, C7-C9, C7-C8, C8-C10, C8-C9 and C9-C10 substituted or unsubstituted alkyl.

As other examples, the integers in the range of 5-40 are specifically intended to disclose individually 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40; the integers in the range of 1-20 are specifically intended to disclose individually 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. Accordingly, other groups or ranges are specifically contemplated.

In the present application, "nitrile solvents" refer to a class of organic compounds containing an organic group cyano and being liquid at room temperature.

As described in the background technology above, nitrile solvents are incompatible with the battery negative electrode, which makes it impossible to use nitrile solvents as the main solvent of the electrolyte, and also affects the application of nitrile solvents in the electrolyte. Therefore, it is necessary to improve the incompatibility between the battery negative electrode and the nitrile solvent.

For the above problems, the related art generally adopts the method of increasing the concentration of electrolyte salt in the electrolyte and adding a large amount of components that are conducive to forming a solid electrolyte membrane, thereby forming a more stable solid electrolyte membrane, improving the stability of the electrolyte and the negative electrode interface, slowing down the corrosion of nitrile solvents on the negative electrode, and thus improving the problem of incompatibility between the battery negative electrode and nitrile solvents. However, the problem with the above method is that the high electrolyte salt concentration and the large amount of film-forming agent added will increase the viscosity of the electrolyte, resulting in a decrease in the ionic conductivity of the electrolyte, and will also lead to a significant increase in the cost of the electrolyte, which also limits the application of nitrile solvents in the electrolyte.

Based on this, the present application provides an electrolyte solution, which can effectively improve the incompatibility problem between the battery negative electrode and the nitrile solvent by selecting a nitrile solvent with a specific structure, thereby reducing the adverse effects of the nitrile solvent on the battery performance. The embodiments of the present application are described in detail below.

Electrolyte

In a first aspect, the present application provides an electrolyte solution, comprising: an organic solvent and an electrolyte salt, wherein the organic solvent comprises a nitrile solvent, wherein the ortho-carbon atom of the cyano group in the nitrile solvent is a quaternary carbon atom.

According to the present application, the ortho-position carbon atom of the cyano group in the nitrile solvent in the electrolyte is a quaternary carbon atom, and the nitrile solvent has higher stability relative to the negative electrode of the battery. Therefore, the electrolyte can not only utilize the advantages of the nitrile solvent itself, such as high dielectric constant, low viscosity and high flash point, but also reduce the influence of the incompatibility of the nitrile solvent with the negative electrode of the battery on the battery performance.

Specifically, after analysis, the inventors found that the main reason for the incompatibility of the battery negative electrode with nitrile solvents in the electrolyte is that the negative electrode of the battery exhibits strong reducing properties during use, mainly due to the presence of substances such as lithium, sodium, and lithium/sodium-carbon compounds, and the cyanide group in the nitrile solvent is a strong electron-withdrawing group. The strong electron-withdrawing effect of the cyanide group on adjacent carbon atoms will increase the activity of the hydrogen atoms connected to the adjacent carbon atoms, and therefore it is easier to react with the reducing substances on the negative electrode of the battery, resulting in the removal of hydrogen atoms on the adjacent carbon atoms of the cyanide group in the nitrile solvent, and then leading to the generation of gas (mainly hydrogen). In this process, the active material is also consumed, resulting in reduced cycle performance and charging performance of the battery. Further, if the content of the nitrile solvent in the electrolyte is too large and too much gas is generated, it may cause safety accidents such as battery explosion.

Therefore, based on the above findings, by selecting a nitrile solvent in which the ortho-carbon atom of the cyano group is a quaternary carbon atom, since the quaternary carbon atom is not connected to the hydrogen atom, the nitrile solvent does not contain hydrogen atoms activated by the cyano group, and exhibits strong stability to the battery negative electrode, making the above reaction less likely to occur. This can effectively improve the compatibility of the nitrile solvent with the battery negative electrode and reduce the adverse effects of the nitrile solvent on the battery performance.

It should be noted that, generally speaking, the role of nitrile solvents in electrolytes is not only to dissolve and ionize electrolyte salts, but also to participate in the formation of solid electrolyte membranes, etc. The electrolyte provided in this application does not make further requirements for the above-mentioned roles. The main problem solved by this application is to improve the incompatibility of nitrile solvents in electrolytes with the negative electrode of the battery.

In some embodiments, the volume percentage of the nitrile solvent in the organic solvent is greater than 5%; optionally, the volume percentage of the nitrile solvent in the organic solvent is 10% to 99%.

In some of the above embodiments, since the nitrile solvent has good compatibility with the negative electrode of the battery, the amount of the nitrile solvent added in the electrolyte can be unrestricted, thereby increasing the content of the nitrile solvent in the electrolyte. When the volume percentage of the nitrile solvent in the organic solvent can be above 5%, the advantages of the high dielectric constant, low viscosity and high flash point of the nitrile solvent itself can be fully utilized to further improve the ionic conductivity and safety performance of the electrolyte. For example, the volume percentage of the nitrile solvent in the organic solvent can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, 100%, or within the range of any of the above values. Preferably, the volume percentage of the nitrile solvent in the organic solvent is 10% to 99%, so the electrolyte has better ionic conductivity and safety performance.

In some embodiments, the nitrile solvent includes at least one of a mononitrile solvent, a dinitrile solvent, or a trinitrile solvent.

In some of the above embodiments, the nitrile solvent may include but is not limited to containing one cyano group, and may also contain two or three cyano groups at the same time. Since the adjacent carbon atoms of each cyano group are quaternary carbon atoms, mononitrile solvents, dinitrile solvents or trinitrile solvents have good compatibility with the battery negative electrode, and can effectively reduce the impact of nitrile solvents on battery performance.

Further, nitrile solvents include mononitrile solvents. Mononitrile solvents are generally simpler in structure and have relatively smaller molecular weights than dinitrile solvents or trinitrile solvents, so their viscosity is relatively smaller and their molecular polarity is relatively larger, thereby having better dissolution and ionization properties for electrolyte salts, and are more conducive to improving the ionic conductivity of the electrolyte, thereby further improving the performance of the battery. At the same time, the cost of mononitrile solvents is relatively low, which is conducive to reducing the cost of the electrolyte.

In some embodiments, the nitrile solvent includes a compound as shown in Formula I,

Here, R ₁ , R ₂ , and R ₃ each independently represent a substituent other than H.

In some of the above embodiments, the compound shown in Formula I belongs to a mononitrile solvent, and the carbon atom adjacent to the cyano group is not connected to a hydrogen atom and does not contain an unsaturated carbon-carbon bond. The compound has a relatively larger polarity and has a better dissolution and ionization effect on the electrolyte salt, which can further improve the ionic conductivity of the electrolyte.

Furthermore, _R1 , _R2 , and _R3 are independently represented by at least one of C1-C10 substituted or unsubstituted alkyl, C6-C30 substituted or unsubstituted aromatic group, or halogen atom. In this case, the molecular weight and viscosity of the nitrile solvent are relatively smaller, and the dissolution and ionization effect of the electrolyte salt is better, which can further improve the ionic conductivity of the electrolyte.

For example, the C1-C10 unsubstituted alkyl group may include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,3-dimethylpentyl, 2,2-dimethylpentyl, n-heptyl, 2-methylhexyl, 3-methylhexyl, 3,3-dimethylpentyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 3-ethylpentyl, 2,2,3-trimethylbutyl, etc.; the C1-C10 substituted The alkyl group may include a C1~C10 fluoroalkyl group, which may include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a 1-fluoroethyl group, a 1,1-difluoroethyl group, a 1,1,1-trifluoroethyl group, a perfluoroethyl group, and the like; the C6~C30 substituted or unsubstituted aryl group includes an aromatic compound containing one or more benzene rings, the C6~C30 substituted aryl group may include a C6~C30 fluoroaryl group, and the C6~C30 fluoroaryl group may be a fluorobenzene, a difluorobenzene, a trifluorobenzene, a tetrafluorobenzene, a pentafluorobenzene, and the like.

Furthermore, R ₁ , R ₂ , and R ₃ are independently represented by C1-C10 substituted or unsubstituted alkyl groups. In this case, the nitrile solvent has a relatively smaller molecular weight and a relatively smaller viscosity, and has a better dissolution and ionization effect on the electrolyte salt, which can further improve the ionic conductivity of the electrolyte.

Further, R ₁ , R ₂ , and R ₃ are independently represented by C1-C5 unsubstituted alkyl groups. Since unsubstituted alkyl groups are electron-donating groups, when the hydrogen atoms on the carbon atoms adjacent to the cyano group are completely replaced by unsubstituted alkyl groups, the polarity of the nitrile solvent is greater, and when R ₁ , R ₂ , and R ₃ are independently represented by C1-C5 unsubstituted alkyl groups, the molecular weight and viscosity of the nitrile solvent are smaller, and the dissolution and ionization effect of the electrolyte salt is better, which can further improve the ionic conductivity of the electrolyte.

In some embodiments, R ₁ , R ₂ , and R ₃ are all methyl groups. In this case, the nitrile solvent has a large polarity, a small molecular weight and a small viscosity, and has a better dissolution and ionization effect on the electrolyte salt, which can further improve the ionic conductivity of the electrolyte.

In some embodiments, the organic solvent further includes at least one of a linear carbonate, a cyclic carbonate, and an ether solvent.

In some of the above embodiments, the combination of other organic solvents and nitrile solvents can further improve the performance of the battery. Chain carbonates can participate in the formation of solid electrolyte membranes and further improve the stability of the electrolyte and electrode interface; cyclic carbonates can further improve the solvent's dissolution and ionization of electrolyte salts and improve conductivity; ether solvents can further reduce the viscosity of the electrolyte and improve the wettability of the electrolyte.

Further, the organic solvent also includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, fluoroethylene carbonate, and vinylene carbonate. The electrolyte obtained at this time can further improve the performance of the battery. It is understandable that some of the above-mentioned organic solvents can be used as film-forming additives, that is, some additives that are liquid at room temperature can be added as organic solvents, and the organic solvent can also include other solvents known in the art, and those skilled in the art can select according to actual needs.

In some embodiments, the concentration of the electrolyte salt in the electrolyte is no greater than 2 mol/L.

In some of the above embodiments, since the nitrile solvent has good compatibility with the negative electrode of the battery in the present application, there is no need to add more electrolyte salts to participate in the formation of the solid electrolyte film to improve the interfacial stability of the electrolyte and the electrode, so the concentration of the electrolyte salt in the electrolyte can be appropriately reduced to reduce the viscosity of the electrolyte and save the cost of the electrolyte. For example, the concentration of the electrolyte salt in the electrolyte can be 2mol/L, 1.8mol/L, 1.6mol/L, 1.5mol/L, 1.4mol/L, 1.2mol/L, 1mol/L, 0.8mol/L, 0.6mol/L, 0.5mol/L, 0.4mol/L, 0.2mol/L, 0.1mol/L, or within the range of any of the above values. Further, the concentration of the electrolyte salt in the electrolyte is not more than 1mol/L, and the viscosity of the electrolyte is lower and the cost is smaller.

There is no particular restriction on the type of electrolyte salt in the present application, and the electrolyte salt may include a lithium salt or a sodium salt. As an example, the lithium salt includes, but is not limited to, LiPF ₆ (lithium hexafluorophosphate), LiBF ₄ (lithium tetrafluoroborate), LiClO ₄ (lithium perchlorate), LiFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO ₂ F ₂ (lithium difluorophosphate), LiDODFP (lithium difluorobis(oxalate phosphate)) and LiOTFP (lithium tetrafluorooxalate phosphate). The above lithium salts may be used alone or in combination of two or more. As an example, the sodium salt may be selected from at least one of NaPF ₆ , NaClO ₄ , NaBCl ₄ , NaSO ₃ CF ₃ and Na(CH ₃ )C ₆ H ₄ SO ₃ .

In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

The electrolyte can be prepared according to conventional methods in the art. For example, an organic solvent, an electrolyte salt, and an optional additive can be mixed uniformly to obtain an electrolyte. There is no particular restriction on the order of adding the materials. For example, the electrolyte salt and the optional additive are added to the organic solvent and mixed uniformly to obtain the electrolyte; or, the electrolyte salt is first added to the organic solvent, and then the optional additive is added to the organic solvent and mixed uniformly to obtain the electrolyte.

Secondary battery

In a second aspect, the present application provides a secondary battery, comprising the electrolyte of any embodiment of the first aspect.

According to the present application, since the secondary battery includes the electrolyte of any embodiment of the first aspect, it has the beneficial effects of the first aspect.

Generally, a secondary battery also includes a positive electrode sheet, a negative electrode sheet and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[Positive electrode]

The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and 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.).

In some embodiments, the positive electrode active material may be a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO ₂ ), lithium nickel oxide (such as LiNiO ₂ ), lithium manganese oxide (such as LiMnO ₂ , LiMn ₂ O ₄ ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM ₃₃₃ ), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM ₅₂₃ ), LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM ₂₁₁ ), LiNi _0.6 Co 0.2 Mn _0.2 O ₂ (also referred to as NCM ₆₂₂ ), LiNi 0.8 Co _0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), and LiNi _0.8 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM ₈₁₁ ), lithium nickel cobalt aluminum oxide (such as LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[Negative electrode]

The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and 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.).

In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode 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, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. The negative electrode active material may also be an alkali metal element, including but not limited to at least one of lithium metal and sodium metal. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[Isolation film]

In some embodiments, the present application has no particular limitation on the type of isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.

In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

In some embodiments, the secondary battery may be a lithium ion battery, a lithium metal battery, a sodium ion battery, or a sodium metal battery.

Electronic equipment

In a third aspect, the present application provides an electronic device comprising a secondary battery according to any embodiment of the second aspect.

According to the present application, since the electronic device includes the secondary battery of any embodiment of the second aspect, the electronic device has the beneficial effects of the second aspect.

The electronic device of the present application is not particularly limited, and it can be used for any electronic device known in the prior art. In some embodiments, the electronic device can include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be obtained commercially.

Electrolyte performance test:

Using a 2032 button battery configuration and accessories, the positive electrode shell, 19 μm diameter copper foil, electrolyte, diaphragm, 16 μm lithium sheet, gasket, and spring are placed in order and assembled into a button battery; and the battery is tested at a current density of 1 mA/ ^cm2 and a deposition capacity of 0.5 mAh/ ^cm2 , and the coulombic efficiency of the lithium-copper battery of the electrolyte configured in the embodiment and the comparative example is calculated.

Example 1

Preparation of electrolyte: LiFSI was added into a TMAN (trimethylacetonitrile) and FEC (fluoroethylene carbonate) solvent in a volume ratio of 9:1 according to a lithium salt concentration of 1 mol/L (taking the preparation of 1 mL of solvent as an example, the volumes of TMEA and FEC added were 0.9 mL:0.1 mL, respectively), and the mixed electrolyte was prepared after stirring evenly to obtain an electrolyte.

The electrolyte performance test was performed on the above electrolyte. The coulombic efficiency of the lithium-copper half-cell tested using the electrolyte configured in Example 1 is shown in FIG. 1 .

Comparative Example 1

Preparation of electrolyte: Lithium hexafluorophosphate (LiPF ₆ ) lithium salt is slowly dissolved in an organic carbonate solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a mass ratio of 3:7, so that the LiPF ₆ lithium salt concentration of the electrolyte is 1 mol/L, and the electrolyte is obtained after stirring evenly.

The electrolyte performance test was performed on the above electrolyte. The coulombic efficiency of the lithium-copper half-cell tested using the electrolyte configured in Comparative Example 1 is shown in FIG. 2 .

According to Figures 1 and 2, under the same test conditions and battery configuration, it can be seen that conventional lithium-ion battery carbonate electrolytes are not compatible with lithium metal batteries. The coulombic efficiency of the lithium-copper half-cell is only about 90%, and the battery performance drops sharply after 20 cycles. However, the electrolyte configured with TMAN as the main solvent has good compatibility and cycle stability with metallic lithium. In 50 battery cycles, the battery coulombic efficiency is around 95%, and the performance far exceeds that of conventional carbonate electrolytes.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims (10)

1. An electrolyte, characterized in that it comprises: an organic solvent and an electrolyte salt, wherein the organic solvent comprises a nitrile solvent, and the adjacent carbon atom of the cyano group in the nitrile solvent is a quaternary carbon atom. 2. The electrolyte according to claim 1, characterized in that the volume percentage of the nitrile solvent in the organic solvent is greater than 5%; Optionally, the volume percentage of the nitrile solvent in the organic solvent is 10% to 99%. 3. The electrolyte according to claim 1, characterized in that the nitrile solvent comprises at least one of a mononitrile solvent, a dinitrile solvent or a trinitrile solvent; Optionally, the nitrile solvent includes a mononitrile solvent. 4. The electrolyte according to claim 3, characterized in that the nitrile solvent comprises a compound as shown in Formula I, Here, R ₁ , R ₂ , and R ₃ each independently represent a substituent other than H. 5. The electrolyte according to claim 4, characterized in that R ₁ , R ₂ , and R ₃ are independently represented by at least one of a C1-C10 substituted or unsubstituted alkyl group, a C6-C30 substituted or unsubstituted aromatic group, or a halogen atom; Optionally, R ₁ , R ₂ , and R ₃ are independently represented by C1-C10 substituted or unsubstituted alkyl groups; Optionally, R ₁ , R ₂ , and R ₃ are each independently a C1-C5 unsubstituted alkyl group. The electrolyte according to claim 5, characterized in that R ₁ , R ₂ and R ₃ are all methyl groups. 7. The electrolyte according to any one of claims 1 to 6, characterized in that the organic solvent further comprises at least one of a chain carbonate, a cyclic carbonate, and an ether solvent; Optionally, the organic solvent further includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, fluoroethylene carbonate, and vinylene carbonate. 8. The electrolyte according to any one of claims 1 to 6, characterized in that the concentration of the electrolyte salt in the electrolyte is not greater than 2 mol/L; Optionally, the concentration of the electrolyte salt in the electrolyte is not greater than 1 mol/L. 9. A secondary battery, comprising the electrolyte according to any one of claims 1 to 8. 10 . An electronic device, comprising the secondary battery according to claim 9 .