Electrolyte, lithium ion battery, formation method of lithium ion battery and electric device

Abstract

The invention relates to # imgabs 0 # electrolyte, a lithium ion battery, a formation method (100) of the lithium ion battery, and an electric device. The electrolyte comprises a film-forming additive and metal ions; wherein the reduction potential # imgabs1 # of the metal ions meets the formula # imgabs2 #, Mn < + > represents the metal ions, n represents the valence of the metal ions, R represents the ideal gas constant, T represents the temperature, C represents the molar concentration of the metal ions in the electrolyte, F represents the Faraday constant, and # imgabs3 # represents the reductive decomposition potential of the film-forming additive. When the electrolyte is applied to the lithium ion battery, the growth of lithium dendrites can be inhibited.

Description

Electrolyte, lithium-ion battery, formation method thereof, and power-consuming device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202310794171.5 filed on June 30, 2023, entitled “Lithium-ion battery and electrical device”. The entire contents of the above patent application are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and more specifically, to an electrolyte, a lithium-ion battery, a formation method thereof, and an electrical device. Background Art

[0004] In recent years, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields, and have thus achieved great development.

[0005] Lithium dendrites are a factor that affects the performance of lithium-ion batteries. Their growth can lead to reduced coulombic efficiency and poor cycling performance. In severe cases, they can puncture the separator and cause a short circuit. Therefore, inhibiting the growth of lithium dendrites is a pressing technical challenge.

[0006] Summary of the Invention

[0007] This application is made in view of the above technical problems, and its purpose is to provide an electrolyte that can effectively inhibit the growth of lithium dendrites when used in lithium-ion batteries.

[0008] In order to achieve the above-mentioned objectives, the present application provides an electrolyte, a lithium-ion battery and a formation method thereof, and an electrical device.

[0009] In a first aspect, an electrolyte is provided, which includes a film-forming additive and metal ions; the reduction potential of the metal ions is satisfy: Among them, M n+ represents the metal ion, n represents the valence of the metal ion, R represents the ideal gas constant, T represents the temperature, C represents the molar concentration of the metal ion in the electrolyte, F represents the Faraday constant, represents the reductive decomposition potential of the film-forming additive.

[0010] It should be understood that the reduction potential of the metal ions and the reduction decomposition potential of the film-forming additive are the reduction potentials of the two relative to the same standard electrode.

[0011] The electrolyte provided by the embodiment of the present application includes a film-forming additive and a metal ion. The film-forming additive helps to form a dense SEI film on the surface of the negative electrode. Since the reduction potential of the metal ion is higher than the reduction decomposition potential of the film-forming additive, when the film-forming additive begins to reduce and decompose to form the SEI film, the metal ion has been reduced and has formed a metal element on the surface of the negative electrode, so that a metal element is formed between the surface of the negative electrode plate of the lithium-ion battery after formation and the SEI film. Thus, during the cycle of the lithium-ion battery, the lithium precipitated on the surface of the negative electrode plate forms a lithium-metal alloy with the metal element and is consumed. The lithium precipitated later can be deposited on the lithium-metal alloy to form a relatively smooth deposition morphology instead of growing into a dendritic shape. In other words, the technical solution of the embodiment of the present application can not only consume the precipitated lithium in the case of lithium deposition in the battery, but also change the morphology of the precipitated lithium deposition, inhibit the formation and / or growth of lithium dendrites, and reduce the risk of battery safety problems caused by lithium deposition in the battery.

[0012] In a possible implementation, the molar concentration C of the metal ions in the electrolyte satisfies: 0.01M≤C≤0.2M.

[0013] In the embodiments of the present application, by controlling the concentration of metal ions in the electrolysis within a suitable range, it helps to form a metal element and / or lithium-metal alloy covering the surface of the negative electrode while reducing the effect of metal ions on battery self-discharge.

[0014] In a possible implementation, a mass ratio m1 / m2 of the film-forming additive to the electrolyte satisfies: 0.1%≤m1 / m2≤10%.

[0015] In the embodiments of the present application, controlling the amount of the film-forming additive in the electrolyte within a suitable range helps to form a dense SEI film.

[0016] In a possible implementation, the metal ions include: Mg 2+ 、Zn 2+ 、Sn 2+ 、Ag + 、In 3+ 、Ga 3+ 、Sb 3+ At least one of, optionally, the metal ions include Mg 2+ .

[0017] In a possible implementation, the film-forming additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl sulfite, propylene sulfite, and lithium difluorooxalatoborate.

[0018] In a possible implementation, the electrolyte includes: an inorganic salt, wherein the inorganic salt includes the metal ion and an anion;

[0019] The anions include at least one of acetate, tetrafluoroborate, perchlorate, nitrate, carbonate, acetate, bis(trifluoromethylsulfonyl)imide, trifluoromethanesulfonate, difluorooxalatoborate, dioxalatoborate, methanesulfonate, hexafluorophosphate, and halogen anions.

[0020] In one possible implementation, the electrolyte includes: a solvent; the solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate or butyl propionate.

[0021] In a possible implementation, the electrolyte includes a lithium salt; the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethylsulfonylimide), and lithium bis(oxaloyl)borate.

[0022] In a possible implementation, the molar concentration C' of the lithium salt in the electrolyte satisfies: 0.05M≤C'≤2M.

[0023] In a second aspect, a lithium-ion battery is provided, wherein the lithium-ion battery includes the electrolyte in any possible implementation of the first aspect.

[0024] In a third aspect, a lithium-ion battery is provided, comprising an electrolyte; and a negative electrode plate, wherein a composite layer is formed on a surface of the negative electrode plate close to the electrolyte, the composite layer comprising a metal layer and a solid electrolyte interface (SEI) film, the metal layer being located between the surface of the negative electrode plate and the SEI film, the metal layer comprising a metal element and / or a lithium-metal alloy.

[0025] In a possible implementation, the electrolyte includes metal ions, and the metal ions are consistent with the elements of the metal element and / or the elements of the metal in the lithium-metal alloy.

[0026] In a possible implementation, the molar concentration C1 of the metal ions in the electrolyte satisfies: 0.001M≤C1≤0.18M.

[0027] In a possible implementation, the metal ions include: Mg 2+ 、Zn 2+ 、Sn 2+ 、Ag + 、In 3+ 、Ga3+ 、Sb 3+ At least one of, optionally, the metal ions include Mg 2+ .

[0028] In a possible implementation, the electrolyte further includes a film-forming additive, and the film-forming additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl sulfite, propylene sulfite, and lithium difluorooxalatoborate.

[0029] In a fourth aspect, a formation method of the lithium-ion battery in the second aspect is provided, wherein the formation method includes a charging stage, wherein the charging stage includes: a first charging stage, charging the lithium-ion battery with a first current I1 to a first voltage U1 at a constant current; a second charging stage, charging the lithium-ion battery with a constant voltage at the first voltage U1 for a duration of T; a third charging stage, charging the lithium-ion battery with a constant current to a cut-off voltage; a fourth charging stage, charging the lithium-ion battery with a constant voltage at the cut-off voltage until the current is less than or equal to the cut-off current; wherein the reduction potential of the metal ion Higher than the reduction decomposition potential of the film-forming additive The negative electrode potential of the lithium ion battery at the first voltage U1 is higher than the reduction decomposition potential of the film-forming additive. and lower than the reduction potential of the metal ion T>0min.

[0030] In an embodiment of the present application, for a lithium-ion battery whose electrolyte includes metal ions and a film-forming additive, a second charging stage is provided during the formation process so that the metal ions in the electrolyte are already reduced when the film-forming additive begins to decompose and form an SEI film, and the metal element has already formed on the surface of the negative electrode. In this way, during the cycling of the lithium-ion battery, the lithium precipitated on the surface of the negative electrode forms a lithium-metal alloy with the metal element and is consumed. The lithium precipitated later can be deposited on the lithium-metal alloy, forming a relatively smooth deposition morphology instead of growing into a dendrite. At the same time, because the reduction decomposition potential of the film-forming additive is lower than the reduction potential of the metal ion, during the constant voltage charging stage when the metal ion is reduced, the film-forming additive will not be reduced and decomposed, or will be reduced and decomposed in a very small amount, which will not affect the reduction of the metal ions to form the metal element on the surface of the negative electrode. In the third and fourth charging stages, the film-forming additive in the electrolyte is reduced and decomposes, forming an SEI film on the metal element and / or the lithium-metal alloy coating.

[0031] In a possible implementation, the formation method includes a discharge stage, and the discharge stage includes: discharging the lithium-ion battery at a constant current to a cut-off voltage.

[0032] In a possible implementation, 0 min<T≤60 min; optionally, 10 min≤T≤20 min.

[0033] In the embodiment of the present application, by controlling the charging time of the second charging stage within an appropriate range, the metal ions are helped to be fully reduced at the negative electrode to form a metal element.

[0034] In a possible implementation, the first voltage U1 satisfies: U1=U X +U M ; Wherein, UX represents the voltage of the lithium ion battery when the metal ions begin to reduce, U M Represents a constant, 0V≤U M ≤0.3V; optionally, 0.05V≤U M ≤0.15V.

[0035] In a possible implementation, the first current I1 satisfies: 0.01C≤I1≤0.1C.

[0036] In the embodiments of the present application, the risk of a large amount of film-forming additives being reduced and decomposed during the reduction of metal ions is reduced by controlling the charging current in the first charging stage within a suitable range.

[0037] In a possible implementation, the metal ions include: Mg 2+ 、Zn 2+ 、Sn 2+ 、Ag + 、In 3+ 、Ga 3+ 、Sb 3+ At least one of, optionally, the metal ions include Mg 2+ .

[0038] In a possible implementation, the film-forming additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl sulfite, propylene sulfite, and lithium difluorooxalatoborate.

[0039] In one possible implementation, the electrolyte includes: an inorganic salt, the inorganic salt includes the metal ions and anions; the anions include: at least one of acetate, tetrafluoroborate, perchlorate, nitrate, carbonate, acetate, bistrifluoromethylsulfonyl imide, trifluoromethanesulfonate, difluorooxalatoborate, dioxalatoborate, methanesulfonate, hexafluorophosphate, and halogen anions.

[0040] In a fifth aspect, an electrical device is provided, which includes the lithium-ion battery of the second aspect, and / or the lithium-ion battery of any possible implementation of the third aspect, and / or the lithium-ion battery obtained after the formation method of any possible implementation of the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0042] FIG1 is a schematic flow chart of a formation method of a lithium-ion battery according to the present application;

[0043] FIG2 is another schematic flow chart of a formation method of a lithium-ion battery according to the present application;

[0044] FIG3 is a schematic diagram of a battery cell of a lithium-ion battery of the present application;

[0045] FIG4 is a schematic diagram of the exploded structure of a battery cell disclosed in one embodiment of the present application;

[0046] FIG5 is a schematic diagram of the exploded structure of a battery disclosed in one embodiment of the present application;

[0047] FIG6 is a schematic diagram of an electrical device disclosed in one embodiment of the present application;

[0048] FIG7 is a scanning electron microscope image of a moss-like lithium deposit disclosed in an embodiment of the present application;

[0049] FIG8 is a scanning electron microscope image of a planar lithium deposit disclosed in an embodiment of the present application;

[0050] FIG9 is a scanning electron microscope image of a dendritic lithium deposited in the present application. DETAILED DESCRIPTION

[0051] Below, the embodiments of the electrolyte, lithium-ion battery, formation method thereof, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0052] In the description of this application, it should be noted that, unless otherwise specified, "plurality" means more than two; terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are merely for the purpose of facilitating the description of this application and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this application. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0054] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0055] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0056] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0057] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their generally accepted meanings in the art.

[0058] As mentioned, "reduction potential" refers to the electrode potential of a substance relative to a standard electrode. Specifically, the reduction potential is the electrode potential of a substance measured by combining the substance with a standard electrode in a galvanic cell. The standard electrode is typically a standard hydrogen electrode, but in some other cases, it can also be a saturated calomel electrode. For example, in a lithium-ion battery, the standard electrode can be a lithium electrode. Alternatively, the reduction potential of a substance relative to a standard electrode can be calculated by measuring the reduction potentials of two substances relative to a standard hydrogen electrode.

[0059] Where mentioned, "reductive decomposition potential" refers to the electrode potential of a substance relative to a standard electrode when it decomposes.

[0060] As mentioned, "lithium dendrites" refer to the dendritic lithium metal that forms when lithium ions are reduced during the cycling process of lithium-ion batteries.

[0061] Where mentioned, the "SEI film" refers to the solid electrolyte interface (SEI) film. The SEI film is a passivation film formed on the negative electrode surface of a lithium-ion battery by lithium ions and some components of the electrolyte during charging.

[0062] Next, embodiments of the present application are introduced.

[0063] In recent years, secondary batteries have been widely used in power tools, electronic products, electric vehicles, aerospace and other fields due to their high energy density and long service life, and have thus achieved great development. Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. Among them, the electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, which allows active ions to pass through while preventing the positive and negative electrodes from short-circuiting, so that the electrochemical reaction of the secondary battery proceeds normally.

[0064] Take lithium-ion batteries, for example. They are a typical secondary battery. Because they rely on the chemical reaction of lithium ions intercalating and deintercalating between the positive and negative electrodes for charging and discharging, they are also called rocking-chair batteries. During the charging process, lithium ions are released from the positive electrode active material, transferred through the electrolyte to the negative electrode, and then embedded in the negative electrode active material. During the discharge process, lithium ions are released from the negative electrode active material, transferred through the electrolyte to the positive electrode, and then embedded in the positive electrode active material.

[0065] It should be understood that the "lithium insertion" and "intercalation" processes described in this application refer to the process in which lithium ions are embedded in the positive electrode active material or the negative electrode active material due to an electrochemical reaction, and the "de-lithiumization", "de-lithiumization" and "de-intercalation" processes described in this application refer to the process in which lithium ions are removed from the positive electrode active material or the negative electrode active material due to an electrochemical reaction.

[0066] During the charge and discharge process of lithium-ion batteries, factors such as changes in the battery's internal resistance, the balance between the electrochemical reaction speeds of the positive and negative electrodes and the speed of electron movement, and the diffusion rate of lithium ions involved in the electrochemical reactions all lead to battery polarization, causing lithium ions to precipitate from the surface of the negative electrode active material layer, a phenomenon known as lithium plating. Further lithium ion deposition can lead to the formation and growth of lithium dendrites. In severe cases, lithium dendrites can pierce the separator, causing a short circuit between the positive and negative electrodes and potentially causing battery safety issues.

[0067] In view of this, the embodiments of the present application provide an electrolyte, a lithium-ion battery, a formation method thereof, and an electrical device. The electrolyte includes a film-forming additive and a metal ion, and the reduction potential of the metal ion is higher than the reduction decomposition potential of the film-forming additive. Since the reduction potential of the metal ion is higher than the reduction decomposition potential of the film-forming additive, when the film-forming additive begins to reduce and decompose to form the SEI film, the metal ion has been reduced and has formed a metal element on the surface of the negative electrode, so that a metal element is formed between the surface of the negative electrode of the lithium-ion battery after formation and the SEI film. Therefore, during the cycle of the lithium-ion battery, the lithium precipitated on the surface of the negative electrode forms a lithium-metal alloy with the metal element and is consumed, and the lithium precipitated later can be deposited on the lithium-metal alloy to form a relatively smooth deposition morphology, rather than growing into a dendritic shape. In the technical solution provided by the embodiments of the present application, since the reduction potential of the metal ions is higher than the reduction and decomposition potential of the film-forming additive, by the time the film-forming additive begins to reduce and decompose to form the SEI film, the metal ions have already been reduced and formed into a single metal on the surface of the negative electrode. This reduces the possibility that the SEI film formed by the film-forming additive being reduced and decomposed first will affect the formation of a single metal on the negative electrode surface. This ensures that sufficient single metal is present on the surface of the negative electrode to consume lithium deposited on the negative electrode surface during the cycling of the lithium-ion battery, or to provide sufficient areas for the deposited lithium to form a smooth deposition morphology.

[0068] First, an electrolyte is provided, which includes a film-forming additive and metal ions. The reduction potential of the metal ions is satisfy: Among them, M n+ represents the metal ion, n represents the valence of the metal ion, R represents the ideal gas constant, T represents the temperature, C represents the molar concentration of the metal ion in the electrolyte, and F represents the Faraday constant. Represents the reductive decomposition potential of the film-forming additive. Typically, R is equal to 8.314 J·K-1·mol-1, T is expressed in K, and F is equal to 96485 C·mol-1.

[0069] Specifically, the reduction potential of the metal ions is higher than the reduction and decomposition potential of the film-forming additive. This means that during battery formation, when the metal ions are reduced to elemental metal, the film-forming additive will not be reduced and decomposed, or only a very small amount of the film-forming additive will be reduced and decomposed. On the one hand, this reduces the possibility that the film-forming additive will be reduced and decomposed first to form an SEI film on the surface of the negative electrode, affecting the formation of metal ions into elemental metal on the negative electrode surface. On the other hand, in the subsequent formation, after the metal ions are fully reduced, the film-forming additive forms an SEI film on the surface of the elemental metal, preventing further decomposition of the electrolyte.

[0070] It should be understood that the reduction potential of the metal ion and the reduction decomposition potential of the film-forming additive mentioned in the embodiments of the present application are relative to the same standard electrode. For example, in one example, the reduction potential of the metal ion is the reduction potential of the metal ion relative to a lithium electrode, and the reduction decomposition potential of the film-forming additive is the reduction decomposition potential of the film-forming additive relative to a lithium electrode. In another example, the reduction potential of the metal ion is the reduction potential of the metal ion relative to a standard hydrogen electrode, and the reduction decomposition potential of the film-forming additive is the reduction decomposition potential of the film-forming additive relative to a standard hydrogen electrode.

[0071] In the embodiments of the present application, by introducing metal ions with a reduction potential higher than the reduction decomposition potential of the film-forming additive into the electrolyte of the lithium-ion battery, on the one hand, the lithium ions deposited on the surface of the negative electrode can be consumed, and on the other hand, the formation and / or growth of lithium dendrites can be effectively inhibited, thereby reducing the risk of battery safety problems caused by lithium deposition in the battery.

[0072] Typically, a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The lithium-ion battery provided in this application and its various components are described below.

[0073] [Positive electrode]

[0074] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.

[0075] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0076] In one embodiment, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. 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 base layer. 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.).

[0077] In one embodiment, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, 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 may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), 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 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0078] The battery is accompanied by Li deintercalation and consumption during the charge and discharge process. The molar content of Li in the positive electrode active material is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li will change after the charge and discharge cycle. In the list of positive electrode active materials in this application, the molar content of O is only the ideal state value. Lattice oxygen release will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0079] In one embodiment, the positive electrode active material layer further includes 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 fluorine-containing acrylate resin.

[0080] In one embodiment, the positive electrode active material layer further includes a conductive agent. As an example, 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.

[0081] In one embodiment, the positive electrode sheet can be prepared by separately forming a positive electrode slurry from the components used to prepare the positive electrode sheet. For example, the first positive electrode active material and / or the second positive electrode active material, a conductive agent, a binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated on a positive electrode current collector. After drying and rolling, the positive electrode sheet can be obtained.

[0082] [Negative electrode]

[0083] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0084] 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 either or both of the two opposite surfaces of the negative electrode current collector.

[0085] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0086] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well 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 oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. 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.

[0087] 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).

[0088] 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.

[0089] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0090] In some embodiments, the negative electrode sheet can be prepared by the following method: 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 current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0091] [Electrolyte]

[0092] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0093] The present application provides an electrolyte for a lithium ion battery, wherein the electrolyte comprises a film-forming additive and metal ions. satisfy: Among them, M n+ represents the metal ion, n represents the valence of the metal ion, R represents the ideal gas constant, T represents the temperature, C represents the molar concentration of the metal ion in the electrolyte, and F represents the Faraday constant. Represents the reductive decomposition potential of the film-forming additive.

[0094] In the embodiment of the present application, the electrolyte includes a film-forming additive and a metal ion. The film-forming additive helps to form a dense SEI film on the surface of the negative electrode. Since the reduction potential of the metal ion is higher than the reduction decomposition potential of the film-forming additive, when the film-forming additive begins to reduce and decompose to form the SEI film, the metal ion has been reduced and has formed a metal element on the surface of the negative electrode, so that a metal element is formed between the surface of the negative electrode of the lithium-ion battery after formation and the SEI film. Thus, during the cycle of the lithium-ion battery, the lithium precipitated on the surface of the negative electrode forms a lithium-metal alloy with the metal element and is consumed. The lithium precipitated later can be deposited on the lithium-metal alloy to form a relatively smooth deposition morphology instead of growing into a dendritic shape. In other words, the technical solution of the embodiment of the present application can not only consume the precipitated lithium in the case of lithium deposition in the battery, but also change the morphology of the precipitated lithium deposition, inhibit the formation and / or growth of lithium dendrites, and reduce the risk of battery safety problems caused by lithium deposition in the battery.

[0095] In one embodiment, the mass ratio m1 / m2 of the film-forming additive to the electrolyte satisfies: 0.1%≤m1 / m2≤10%.

[0096] Specifically, m1 / m2 can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or its value is within the range obtained by combining any two of the above values.

[0097] Film-forming additives decompose during the battery's formation process and participate in the formation of the SEI film, helping lithium-ion batteries build a dense SEI film on the negative electrode surface. On the one hand, if the content of film-forming additives in the electrolyte is too low, the film-forming effect will be limited. On the other hand, if the content of film-forming additives in the electrolyte is too high, it may affect the viscosity of the electrolyte, thereby affecting the ion transport speed of the lithium-ion battery.

[0098] In this embodiment, by controlling the concentration of the film-forming additive in the electrolyte within an appropriate range, a dense SEI film can be formed on the surface of the negative electrode of the lithium-ion battery while reducing the effect of the film-forming additive on the electrolyte concentration.

[0099] It should be understood that the amount of film-forming additive varies before and after formation of a lithium-ion battery, and that the film-forming additive is at least partially consumed during the formation process. The above mass ratio of film-forming additive to electrolyte refers to the mass ratio of film-forming additive to electrolyte before formation of the lithium-ion battery.

[0100] In one embodiment, the molar concentration C of the metal ions in the electrolyte satisfies: 0.01M≤C≤0.2M.

[0101] Specifically, C can be 0.01M, 0.02M, 0.03M, 0.04M, 0.05M, 0.06M, 0.07M, 0.08M, 0.09M, 0.1M, 0.11M, 0.12M, 0.13M, 0.14M, 0.15M, 0.16M, 0.17M, 0.18M, ​​0.19M, 0.2M, or its value is within the range obtained by combining any two of the above values.

[0102] On the one hand, if the metal ion content in the electrolyte is too low, the amount of metal ions reduced to form a single metal at the negative electrode is limited, and their role in consuming precipitated lithium ions and inhibiting the formation and / or growth of lithium dendrites is limited. On the other hand, if the metal ion content in the electrolyte is too high, it may lead to increased self-discharge of the lithium-ion battery.

[0103] Therefore, this embodiment controls the concentration of metal ions in the electrolyte within a suitable range, thereby forming a metal element covering the surface of the negative electrode, inhibiting the formation and / or growth of lithium dendrites, and reducing the impact of metal ions on battery self-discharge.

[0104] It should be understood that the amount of metal ions in a lithium-ion battery is different before and after formation, and that the metal ions are at least partially consumed during the formation process. The molar concentration of the metal ions in the electrolyte described above is the molar concentration of the metal ions in the electrolyte before formation of the lithium-ion battery.

[0105] In one embodiment, the film-forming additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl sulfite, propylene sulfite, and lithium difluorooxalatoborate.

[0106] In one embodiment, the metal ions include: Mg 2+ 、Zn 2+ 、Sn 2+ 、Ag + 、In 3+、Ga 3+ , Sb3+, optionally, the metal ions include Mg 2+ .

[0107] In one embodiment, the electrolyte includes: an inorganic salt, the inorganic salt includes a metal ion and an anion; the anion includes: at least one of acetate, tetrafluoroborate, perchlorate, nitrate, carbonate, acetate, bistrifluoromethylsulfonyl imide, trifluoromethanesulfonate, difluorooxalatoborate, dioxalatoborate, methanesulfonate, hexafluorophosphate, and a halogen anion.

[0108] Specifically, metal ions can be introduced by adding inorganic salts into the electrolyte.

[0109] In one embodiment, the electrolyte includes: a solvent; the solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate or butyl propionate.

[0110] In one embodiment, the electrolyte includes a lithium salt; the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(oxaloyl)borate.

[0111] In one embodiment, the molar concentration C' of the lithium salt in the electrolyte satisfies: 0.05M≤C'≤2M.

[0112] Specifically, C' can be 0.05M, 0.06M, 0.07M, 0.08M, 0.09M, 0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M, 0.7M, 0.8M, 0.9M, 1M, 1.1M, 1.2M, 1.3M, 1.4M, 1.5M, 1.6M, 1.7M, 1.8M, 1.9M, 2M, or its value is within the range obtained by combining any two of the above values.

[0113] In one embodiment, the electrolyte may further include 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.

[0114] [Isolator]

[0115] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous structure separator with good chemical and mechanical stability can be selected.

[0116] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0117] 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.

[0118] The present application also provides a lithium-ion battery comprising the electrolyte of any of the aforementioned embodiments. Based on similar principles, the lithium-ion battery comprising the electrolyte of the aforementioned embodiments can achieve corresponding technical effects, which will not be described in detail here.

[0119] Next, the formation method of the lithium-ion battery in the aforementioned embodiment is introduced.

[0120] [Lithium-ion battery formation method]

[0121] The present application also provides a lithium-ion battery formation method. FIG1 is a schematic flow chart of the formation method.

[0122] As shown in FIG1 , a formation method 100 for a lithium-ion battery includes a charging stage 101. Specifically, the charging stage 101 includes:

[0123] S1011, a first charging stage, constant current charging the lithium-ion battery to a first voltage U1 with a first current I1;

[0124] S1012, a second charging stage, constant voltage charging of the lithium-ion battery at a first voltage U1, lasting for a duration of T;

[0125] S1013, the third charging stage, charging the lithium-ion battery with a constant current to a cut-off voltage;

[0126] S1014, a fourth charging stage, charging the lithium-ion battery at a constant voltage at the cut-off voltage until the current is less than or equal to the cut-off current.

[0127] Among them, lithium-ion batteries include electrolytes, which include film-forming additives and metal ions. The reduction potential of the metal ions is Higher than the reduction decomposition potential of film-forming additives The negative electrode potential of the lithium-ion battery at the first voltage U1 is higher than the reduction decomposition potential of the film-forming additive. and lower than the reduction potential of metal ions T>0min.

[0128] For the lithium-ion battery mentioned in the above embodiment, multiple charging stages are set during its formation process. By controlling the lithium-ion battery to charge for a period of time T at a first voltage U1, the metal ions are reduced at the first voltage U1 to form a metal element on the surface of the negative electrode. At the same time, the film-forming additive will not be reduced and decomposed at the first voltage U1, or only a very small amount of the film-forming additive will be reduced and decomposed, which will not affect the reduction of the metal ions on the surface of the negative electrode to form a metal element. During the cycle of the lithium-ion battery, the lithium precipitated on the surface of the negative electrode is consumed by the metal element to form a lithium-metal alloy. The lithium ions subsequently precipitated can be deposited on the lithium-metal alloy to form a relatively smooth deposition morphology, rather than growing into a dendrite, thereby reducing the risk of battery safety problems caused by lithium deposition.

[0129] It should be understood that the first voltage U1 is the full battery voltage. The higher the full battery voltage, the lower the negative electrode potential and the higher the positive electrode potential. The reduction potential mentioned above refers to the electrode potential of a single electrode. For example, in a lithium-ion battery, if the negative electrode potential is less than or equal to the reduction potential of the metal ion relative to lithium, the metal ion will be reduced. At this time, the lithium-ion battery has a corresponding full battery voltage U a If the negative electrode potential is less than or equal to the reduction decomposition potential of the film-forming additive relative to lithium, the film-forming additive will decompose, and the lithium-ion battery will have a corresponding full battery voltage U b .

[0130] In the second charging stage, the negative electrode potential of the lithium-ion battery at the first voltage U1 is higher than the reduction decomposition potential of the film-forming additive relative to lithium. And lower than the reduction potential of metal ions relative to lithium Therefore, at the first voltage U1, the metal ions are reduced by the lithium ions, while the film-forming additives are not reduced and decomposed, or only a very small amount of the film-forming additives are reduced and decomposed. In other words, in the second charging stage, the first voltage U1 is greater than U a , less than U b .

[0131] FIG2 is another schematic flow chart of a formation method 100 provided in an embodiment of the present application.

[0132] In one embodiment, the formation method 100 includes a discharge phase 102, which includes:

[0133] S1021, discharge the lithium-ion battery at a constant current to a cut-off voltage.

[0134] In one embodiment, 0 min<T≤60 min; optionally, 10 min≤T≤20 min.

[0135] Specifically, T can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, 52 min, 54 min, 56 min, 58 min, 60 min, or its numerical range is within the range obtained by combining any two of the above numerical values.

[0136] In the embodiment of the present application, by controlling the charging time of the second charging stage within an appropriate range, the metal ions are helped to be fully reduced at the negative electrode to form a metal element.

[0137] In one embodiment, the first voltage U1 satisfies: U1 = U X +U M Among them, U X Represents the voltage of the lithium-ion battery when the metal ions begin to reduce, U M Represents a constant, 0V≤U M ≤0.3V; optionally, 0.05V≤U M ≤ 0.15V.

[0138] Specifically, U M It can be 0V, 0.01V, 0.02V, 0.03V, 0.04V, 0.05V, 0.06V, 0.07V, 0.08V, 0.09V, 0.10V, 0.11V, 0.12V, 0.13V, 0.14V, 0.15V, 0.15V, 0.17V, 0.18V, 0.19V, 0.20V, 0.21V, 0.22V, 0.23V, 0.24V, 0.25V, 0.26V, 0.27V, 0.28V, 0.29V, 0.30V, or its value is within the range obtained by combining any two of the above values.

[0139] In this embodiment, by setting the first voltage slightly higher than the voltage U of the lithium ion battery when the metal ions begin to reduce, X , so that the metal ions can be fully reduced under the first voltage U1 to form a metal element on the surface of the negative electrode.

[0140] In one embodiment, the first current I1 satisfies: 0.01C≤I1≤0.1C.

[0141] Specifically, I1 can be 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.1C, or its value is within the range obtained by combining any two of the above values.

[0142] In the embodiments of the present application, the risk of a large amount of film-forming additives being reduced and decomposed during the reduction of metal ions is reduced by controlling the charging current in the first charging stage within a suitable range.

[0143] Based on a similar principle, the lithium-ion battery formed by method 100 has metal ions in its electrolyte and can achieve the corresponding technical effects of the aforementioned lithium-ion battery, which will not be described in detail here.

[0144] An embodiment of the present application further provides a formed lithium-ion battery, comprising an electrolyte and a negative electrode plate, wherein a composite layer is formed on a surface of the negative electrode plate close to the electrolyte.

[0145] Specifically, the composite layer includes a metal layer and a SEI film, the metal layer is located between the surface of the negative electrode sheet and the SEI film, and the metal layer includes a metal element and / or a lithium-metal alloy.

[0146] It should be understood that in the embodiments of the present application, the lithium-ion battery after formation can be considered as a lithium-ion battery in which lithium deposition has not yet occurred after formation; it can also be considered as a lithium-ion battery in which lithium deposition has occurred after multiple cycles after formation, that is, a lithium-ion battery after lithium deposition. As mentioned in the aforementioned embodiments, the electrolyte of the lithium-ion battery includes a film-forming additive and metal ions. During the formation process of the lithium-ion battery, the metal ions in the electrolyte are reduced to form a metal element on the surface of the negative electrode. Thereafter, the film-forming additive is reduced and decomposed to form an SEI film. Therefore, a composite layer including a metal layer and an SEI film is formed on the surface of the negative electrode close to the electrolyte. Then, during the cycle of the lithium-ion battery, lithium is deposited on the surface of the negative electrode of the lithium-ion battery. The deposited lithium can form a lithium-metal alloy with the metal element in the metal layer. The subsequently deposited lithium can be deposited on the lithium-metal alloy to form a smooth deposition morphology instead of forming lithium dendrites.

[0147] In one embodiment, the electrolyte includes metal ions that are consistent with the element of the metal element and / or the element of the metal in the lithium-metal alloy.

[0148] In one embodiment, the molar concentration C1 of the metal ions in the electrolyte satisfies: 0.001M≤C1≤0.18M.

[0149] Specifically, the molar concentration C1 of the metal ions in the electrolyte can be 0.001M, 0.002M, 0.005M, 0.01M, 0.02M, 0.03M, 0.05M, 0.08M, 0.1M, 0.11M, 0.12M, 0.13M, 0.15M, 0.16M, 0.17M, 0.18M, ​​or its value is within the range obtained by combining any two of the above values.

[0150] It should be understood that the substances included in the electrolyte of a lithium-ion battery after formation will be different at different stages of the cycle. For example, when a lithium-ion battery has just completed formation and has not yet been recycled, or when it has completed formation and is in the early stages of the cycle, when lithium precipitation has not yet occurred, or when lithium precipitation has just begun, the metal ions in the electrolyte are not completely reduced to metal elements during the formation stage. Therefore, the electrolyte of the lithium-ion battery after formation contains metal ions. For another example, in the middle and late stages of the cycle of a lithium-ion battery, when the amount of lithium precipitation is large, the accumulated lithium will break through the SEI film, thereby contacting the electrolyte, and will react with the remaining metal ions in the electrolyte, reducing the metal ions to metal elements. At this time, the content of metal ion pairs in the electrolyte will decrease.

[0151] Accordingly, the substances included in the metal layer of a lithium-ion battery after formation will be different at different stages of the cycle. For example, when a lithium-ion battery has just been formed and has not yet been recycled, or when it has been formed and is in the early stages of the cycle before lithium deposition occurs, the metal layer includes the metal ions in the electrolyte that are reduced to a metal element during the formation process; for another example, when lithium deposition begins at the beginning of the battery, the deposited lithium forms a lithium-metal alloy with the metal element, and at this time the metal layer includes the metal element and the lithium-metal alloy; and in the middle and late stages of the lithium-ion battery cycle, when the amount of lithium deposition is large, the accumulated lithium will break through the SEI film, thereby coming into contact with the electrolyte, and will react with the remaining metal ions in the electrolyte to reduce the metal ions to a metal element, and at this time the metal layer includes the metal element and the lithium-metal alloy.

[0152] In one embodiment, the metal ions include: Mg 2+ 、Zn 2+ 、Sn 2+ 、Ag + 、In 3+ 、Ga 3+ 、Sb 3+ At least one of, optionally, the metal ions include Mg 2+ .

[0153] In one embodiment, the film-forming additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl sulfite, propylene sulfite, and lithium difluorooxalatoborate.

[0154] The battery cell, battery and electrical device of the present application are described below with reference to the accompanying drawings.

[0155] Typically, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The structure of the battery cell is similar to that of the lithium-ion battery described above, and a detailed description thereof will not be repeated here.

[0156] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0157] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0158] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG3 shows a battery cell 20 having a square structure as an example.

[0159] It should be understood that the battery cell 20 may include the lithium-ion battery in the aforementioned embodiment.

[0160] In some embodiments, referring to Figure 4, the outer packaging may include a shell 21 and a cover plate 23. The shell 21 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 21 has an opening connected to the receiving cavity, and the cover plate 23 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 22 through a winding process or a lamination process. The electrode assembly 22 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 22. The number of electrode assemblies 22 contained in the battery cell 20 can be one or more, and those skilled in the art can select according to specific actual needs.

[0161] In some embodiments, the battery 30 may include multiple battery cells 20. For example, FIG5 is a schematic diagram of the structure of a battery 30 according to one embodiment of the present application. The battery 30 may include multiple battery cells 20. The battery 30 may also include a housing 31 having a hollow interior and housing the multiple battery cells 20. For example, the multiple battery cells 20 may be connected in parallel, in series, or in a mixed combination and then placed in the housing 31.

[0162] Optionally, the battery 30 may also include other structures, which will not be described in detail here. For example, the battery 30 may also include a busbar component, which is used to achieve electrical connection between multiple battery cells 20, such as parallel connection, series connection, or mixed connection. Specifically, the busbar component can achieve electrical connection between the battery cells 20 by connecting the electrode terminals of the battery cells 20. Furthermore, the busbar component can be fixed to the electrode terminals of the battery cells 20 by welding. The electrical energy of the multiple battery cells 20 can be further led out through the box 31 through a conductive mechanism. Optionally, the conductive mechanism may also belong to the busbar component.

[0163] The number of battery cells 20 can be set to any value based on different power requirements. Multiple battery cells 20 can be connected in series, parallel, or in a hybrid manner to achieve higher capacity or power. Since each battery 30 may include a large number of battery cells 20, for ease of installation, the battery cells 20 can be grouped, with each group of battery cells 20 forming a battery module. The number of battery cells 20 included in a battery module is not limited and can be set according to requirements. A battery can include multiple battery modules, which can be connected in series, parallel, or in a hybrid manner.

[0164] In addition, the present application also provides an electric device, which includes at least one of the battery cells, battery modules or batteries provided in the present application. The battery cells, battery modules or batteries can be used as the power source of the electric device, and can also be used as the energy storage unit of the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0165] As the electrical device, a battery cell, a battery module or a battery can be selected according to its usage requirements.

[0166] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cell, a battery or battery module can be used.

[0167] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0168] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0169] 1. Preparation of electrolyte

[0170] Electrolyte 1: A 1M lithium hexafluorophosphate (LiPF6) electrolyte and a 0.05M magnesium bis(trifluoromethylsulfonyl)imide electrolyte were uniformly mixed, and then a film-forming additive VC was added thereto. After stirring, an electrolyte 1 including the film-forming additive and metal ions was obtained. The solvent for the 0.05M magnesium bis(trifluoromethylsulfonyl)imide was ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) (the volume ratio of EC, DMC, and DEC was 1:1:1). In electrolyte 1, the mass ratio m1 / m2 of the film-forming additive VC to the electrolyte was 4%, and the metal ion was Mg. 2+ , Mg 2+ The molar concentration C in the electrolyte is 0.05M.

[0171] Electrolyte 2: The preparation of electrolyte 2 is similar to that of electrolyte 1, except that in electrolyte 2, the metal ion Mg 2+ The molar concentration C in the electrolyte is 0.01M.

[0172] Electrolyte 3: The preparation of electrolyte 3 is similar to that of electrolyte 1, except that in electrolyte 3, the metal ion Mg 2+ The molar concentration C in the electrolyte is 0.2M.

[0173] Electrolyte 4: The preparation of electrolyte 4 is similar to that of electrolyte 1, except that 0.05M bis(trifluoromethylsulfonyl)imide tin is added instead of magnesium bis(trifluoromethylsulfonyl)imide during the preparation of electrolyte 4. In electrolyte 4, the metal ion is Sn. 2+ , Sn 2+ The molar concentration C in the electrolyte is 0.05M.

[0174] Electrolyte 5: The preparation of electrolyte 5 is similar to that of electrolyte 1, except that in electrolyte 5, the film-forming additive is DTD, and the mass ratio m1 / m2 of the film-forming additive DTD to the electrolyte is 1%.

[0175] Electrolyte 6: The preparation of electrolyte 6 is similar to that of electrolyte 1, except that in electrolyte 6, the mass ratio m1 / m2 of the film-forming additive VC to the electrolyte is 10%.

[0176] Electrolyte 7: The preparation of electrolyte 7 is similar to that of electrolyte 1, except that in electrolyte 7, the mass ratio m1 / m2 of the film-forming additive VC to the electrolyte is 0.1%.

[0177] Electrolyte 8: A commercially available LiPF6 electrolyte solution with a concentration of 1 M was prepared as the electrolyte 8. The electrolyte 8 did not contain film-forming additives and metal ions.

[0178] Electrolyte 9: Add the film-forming additive VC to the above-mentioned LiPF6 electrolyte with a concentration of 1M. The mass ratio m1 / m2 of the film-forming additive VC to the electrolyte is 4%.

[0179] Electrolyte 10: The preparation of electrolyte 10 is similar to that of electrolyte 1, except that 0.05M sodium trifluoromethylsulfonyl imide is added instead of magnesium bis(trifluoromethylsulfonyl imide) in the preparation of electrolyte 10. + , Na + The molar concentration C in the electrolyte is 0.05M.

[0180] Electrolyte 11: Add the film-forming additive VC to the above-mentioned LiPF6 electrolyte with a concentration of 1M. The mass ratio m1 / m2 of the film-forming additive VC to the electrolyte is 0.1%.

[0181] 2. Preparation of lithium-ion batteries

[0182] [Example 1]

[0183] (1) Preparation of positive electrode sheet

[0184] 1 kg of the positive electrode active material (LiNi5Co2Mn3O2), 20 g of the conductive agent (carbon nanotubes), and 20 g of the binder (polyvinylidene fluoride (PVDF)) were dissolved in 1 kg of the solvent (N-methylpyrrolidone (NMP)) and mixed thoroughly to create a positive electrode slurry. The slurry was then evenly coated onto the positive electrode current collector (aluminum foil). The positive electrode sheets were then cold pressed and cut.

[0185] (2) Preparation of negative electrode sheet

[0186] Dissolve 1 kg of artificial graphite (the negative electrode active material), 10 g of acetylene black (the conductive agent), 30 g of styrene-butadiene rubber (SBR) (the binder), and 20 g of sodium carboxymethyl cellulose (CMC) (the thickener) in 1 kg of deionized water. Mix thoroughly to create the negative electrode slurry. The slurry is then evenly coated onto the negative electrode current collector copper foil. The negative electrode sheets are then cold-pressed and slit.

[0187] (3) Electrolyte

[0188] The electrolyte used was the electrolyte 1 prepared above.

[0189] (4) Preparation of isolation membrane

[0190] Conventional polypropylene film was used as the separator.

[0191] (5) Assembly of a lithium-ion battery: stack the positive electrode sheet, the separator, and the negative electrode sheet in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, and then wind to obtain an electrode assembly; place the electrode assembly in a battery case, dry it, inject the electrolyte 1, and package it to obtain a lithium-ion battery 1, which is Example 1.

[0192] [Examples 2-7, Comparative Examples 1-4]

[0193] The preparation methods of the lithium-ion batteries of Examples 2-7 and Comparative Examples 1-4 are similar to those of the lithium-ion battery of Example 1, except that different electrolytes are used (Examples 1-7 respectively use electrolytes 1-7, and Comparative Examples 1-4 respectively use electrolytes 8-11). See Tables 1 and 2 for details.

[0194] The lithium-ion battery obtained after packaging is formed according to the following process, and the specific formation process is:

[0195] After standing for 1 minute, the battery was charged at a constant current of 8 mA to 2 V (first charging stage); constant voltage charging was performed at 2 V for 15 minutes (second charging stage); constant current charging was performed at 8 mA to 4.2 V (third charging stage); constant voltage charging was performed at 4.2 V with a cut-off current of 2 mA (fourth charging stage); after standing for 10 minutes, the battery was discharged at a constant current of 8 mA with a cut-off voltage of 2.5 V (discharging stage); after standing for 50 hours, the battery was discharged at a constant current of 8 mA with a cut-off voltage of 2.5 V (discharging stage).

[0196] Table 1: Products and performance parameters of Examples 1-6 and Comparative Examples 1-3

[0197] In Table 1, "m1 / m2" represents the mass ratio of the film-forming additive to the electrolyte before the lithium-ion battery is formed, "C" represents the molar concentration of the metal ions in the electrolyte before the lithium-ion battery is formed, "C1" represents the molar concentration of the metal ions in the electrolyte after the lithium-ion battery is formed, when the metal layer on the surface of the negative electrode plate includes a metal element, "200-cycle capacity retention rate" represents the capacity retention rate of the lithium-ion battery after 200 cycles, and "whether lithium is deposited in the corner area" represents whether lithium is deposited in the negative electrode plate in the bending area of ​​the electrode assembly after the lithium-ion battery is cycled. For the specific test process, please refer to the physical and chemical parameter test section below.

[0198] From the comparison of the results of Examples 1-6 and Comparative Examples 1-3, it can be seen that the electrolyte includes metal ions whose reduction potential is higher than the reduction decomposition potential of the film-forming additive. In the case of lithium precipitation in the corresponding lithium-ion battery, the morphology of the precipitated lithium deposit is relatively smooth (for example, a planar shape as shown in FIG8 ), rather than growing into a dendrite (as shown in FIG9 ). At the same time, the capacity retention rate of the lithium-ion battery is significantly improved, thereby improving the cycle performance of the lithium-ion battery. Furthermore, even if the electrolyte contains metal ions (Comparative Example 3), if the reduction potential of the metal ions is lower than the reduction decomposition potential of the film-forming additive, they cannot be reduced to form a metal layer before forming the SEI film, and the morphology of the precipitated lithium cannot be changed. The capacity retention rate of the battery is low, and the cycle performance is poor.

[0199] From the comparison of the results of Examples 1-3, it can be seen that an increase in the concentration of metal ions is beneficial to improving the cycle performance of the lithium-ion battery; however, by comparing the capacity retention rates of the lithium-ion batteries of Examples 2 and 3, it can be seen that when the metal ion concentration in the electrolyte increases from 0.05M to 0.2M, the increase in the capacity retention rate of the corresponding lithium-ion battery is significantly less than the increase in the capacity retention rate of the lithium-ion battery when the metal ion concentration increases from 0.01M to 0.05M, indicating that when the concentration of metal ions increases to a certain extent, the improvement in the capacity retention rate of the lithium-ion battery is not obvious as its concentration increases. In the embodiments of the present application, under the same other conditions, the molar concentration C of the metal ions in the electrolyte is in the range of 0.01M to 0.2M, the capacity retention rate of the lithium-ion battery is improved better and the cycle performance is better.

[0200] Table 2 Product and performance parameters of Example 7 and Comparative Example 4

[0201] The meanings of the terms in Table 2 are the same as those in Table 1 and are not repeated here.

[0202] Comparison of the results in Example 7 and Comparative Example 4 demonstrates that, even when the content of the film-forming additive in the electrolyte is low, the inclusion of metal ions with a reduction potential higher than the reduction decomposition potential of the film-forming additive can improve the morphology of lithium deposits produced by lithium-ion batteries. Furthermore, the cycle capacity retention of the lithium-ion battery is significantly improved.

[0203] It should be understood that the lithium-ion battery provided herein can be formed according to the formation method provided herein or according to other formation methods. For example, the above Examples 1-7 and Comparative Examples 1-4 can also be formed according to the following method, wherein the formation process is as follows: standing for 1 minute, constant current charging at 8 mA to 4.2 V; constant voltage charging at 4.2 V with a cutoff current of 2 mA; standing for 10 minutes, discharging at 8 mA constant current to a cutoff voltage of 2.5 V, and standing for 50 hours.

[0204] Above, the embodiments and comparative examples related to the lithium-ion battery provided in the present application are introduced. Next, the embodiments and comparative examples related to the formation method provided in the present application are introduced.

[0205] [Examples 8-17 and Comparative Examples 5-7]

[0206] Example 8: Example 8 uses the same preparation process as Example 1 to prepare a lithium ion battery. The lithium ion battery is formed according to the following formation method, which is as follows: standing for 1 minute, constant current charging at 8mA to 2V (first charging stage); constant voltage charging at 2V for 15 minutes (second charging stage); constant current charging at 8mA to 4.2V (third charging stage); constant voltage charging at 4.2V with a cutoff current of 2mA (fourth charging stage); standing for 10 minutes, discharging at 8mA constant current to a cutoff voltage of 2.5V (discharging stage); standing for 50 hours. Wherein, the first current I1=8mA, i.e., I1=0.05C, the first voltage U1=2V, and T=15min.

[0207] Example 9: The formation method of Example 9 is similar to that of Example 8, except that the duration T of the second charging stage in Example 9 is 10 minutes.

[0208] Example 10: The formation method of Example 10 is similar to that of Example 8, except that the duration T of the second charging stage in Example 10 is 20 minutes.

[0209] Example 11: The formation method of Example 11 is similar to that of Example 8, except that the duration T of the second charging stage in Example 11 is 60 minutes.

[0210] Example 12: The formation method of Example 12 is similar to that of Example 8, except that the first voltage U1 in the first charging stage in Example 12 is 2.05V.

[0211] Example 13: The formation method of Example 13 is similar to that of Example 8, except that the first voltage U1 in the first charging stage in Example 13 is 2.15V.

[0212] Example 14: The formation method of Example 14 is similar to that of Example 8, except that the first voltage U1 in the first charging stage in Example 14 is 2.3V.

[0213] Example 15: The formation method of Example 15 is similar to that of Example 8, except that the first current I1 of the first charging stage in Example 15 is 0.01C.

[0214] Example 16: The formation method of Example 16 is similar to that of Example 8, except that the first current I1 of the first charging stage in Example 16 is 0.1C.

[0215] Comparative Example 5: The lithium-ion battery in Comparative Example 3 is a lithium-ion battery obtained by converting the lithium-ion battery in Example 1 into a conventional formation method.

[0216] Comparative Example 6: Compared with Example 8, the lithium ion battery of Comparative Example 6 is charged to 1.8V at a constant current of 8mA in the first charging stage. That is, the lithium ion battery of Comparative Example 6 is charged to a voltage less than U1 in the first charging stage.

[0217] Comparative Example 7: Compared with Example 8, the lithium ion battery of Comparative Example 7 is charged to 2.7V at a constant current of 8mA in the first charging stage. That is, the lithium ion battery of Comparative Example 7 is charged to a voltage greater than U1 in the first charging stage.

[0218] The products and performance parameters of Examples 8-16 and Comparative Examples 5-7 are detailed in Table 3.

[0219] Table 3: Products and performance parameters of Examples 8-16 and Comparative Examples 5-7

[0220] In Table 3, "I1" represents the first current, "U1" represents the first voltage, "T" represents the duration of the second charging stage, "500-cycle capacity retention rate" represents the capacity retention rate of the lithium-ion battery after 500 cycles after formation, and "whether lithium is deposited in the corner area" represents whether lithium is deposited in the negative electrode sheet in the bending area of ​​the electrode assembly after the lithium-ion battery is cycled.

[0221] The lithium ion batteries of the embodiments and comparative examples in Table 3 all use the electrolyte provided by the embodiments of the present application. Regardless of whether it is the embodiment after formation using the formation method of the embodiments of the present application or the comparative example after formation without the formation method of the embodiments of the present application, the lithium precipitated in the corner area is not deposited into a dendritic shape. For example, in Example 8, the deposition morphology of the lithium precipitated in the corner area is planar, and in Comparative Example 5, the deposition morphology of the lithium precipitated in the corner area is moss-like, which once again verifies the inhibitory effect of the electrolyte provided by the present application on the formation and / or growth of lithium dendrites in lithium ion batteries. In addition, the comparative examples in Table 3 all use the lithium ion batteries provided by the present application including the aforementioned electrolyte. Although the formation method provided by the present application is not used, good cycle performance is still exhibited, which proves that the lithium ion batteries provided by the present application also have good cycle performance using other formation methods.

[0222] From the comparison of the results of Examples 8-16 and Comparative Examples 5-7, it can be seen that on the basis of using the lithium-ion battery provided by the present application, combined with the formation method provided in the embodiments of the present application, the capacity retention rate of the lithium-ion battery can be further improved and the cycle performance of the lithium-ion battery can be improved.

[0223] The following is a brief introduction to the test methods for the physical and chemical parameters and performance parameters involved in the embodiments of this application. It should be understood that the following test methods are only examples, and other test methods known in the art can also be used for testing.

[0224] 1. Test method for reduction potential of metal ions

[0225] According to the electrolyte M n+ Metal ion concentration C and equation Obtained by calculation.

[0226] 2. Test method for reduction decomposition potential of film-forming additives

[0227] Before formation, batteries with a lithium metal reference electrode were subjected to cyclic voltammetry (CV) at a scan rate of 0.1 mV / s over a voltage range from the initial cell voltage to the upper cell voltage limit. The peak value of the CV curve was used to monitor the lithium reduction potential of the additive decomposition and the corresponding full cell potential.

[0228] 3. Test method for capacity retention of lithium-ion N-cycle batteries (N is a positive integer)

[0229] Using the Blue Electric test system, the formed lithium-ion battery is first charged and discharged for the first time.

[0230] The first cycle charge refers to the battery being left to stand for 10 minutes after formation, first charged at a constant current of 60mA to a cut-off voltage of 4.2V, and then charged at a constant voltage at 4.2V to a cut-off current of 2mA; the first cycle discharge capacity refers to the capacity W1 released by the battery when it is discharged at a constant current of 60mA to a voltage of 2.5V after formation.

[0231] The battery is then subjected to charge and discharge tests. The test process is: charging at a constant current of 60mA with a cut-off voltage of 4.2V; constant voltage charging at 4.2V with a cut-off current of 2mA; after standing for 10 minutes, discharging at a constant current of 60mA with a cut-off voltage of 2.5V, and then charging to 4.2V after N cycles before the test stops. The discharge capacity after N cycles is W2. The capacity retention rate of lithium-ion batteries over N cycles is W2 / W1×100%. For example, the discharge capacity after 200 cycles is W2', and the capacity retention rate of lithium-ion batteries over 200 cycles is W2' / W1×100%. For another example, the discharge capacity after 500 cycles is W2", and the capacity retention rate of lithium-ion batteries over 500 cycles is W2" / W1×100%.

[0232] 4. Test method for whether lithium is deposited in the corner area of ​​lithium-ion batteries and the morphology of deposited lithium

[0233] (1) The cycled lithium-ion battery is disassembled to obtain the cycled negative electrode sheet, and whether lithium deposition occurs in the corner area of ​​the negative electrode sheet can be directly observed.

[0234] (2) The negative electrode sheet obtained by the above disassembly was tested using a scanning electron microscope. Specifically, a sample was prepared from the corner area of ​​the negative electrode sheet under the protection of an inert atmosphere, and the lithium deposition morphology was observed using a scanning electron microscope. The shooting voltage was 5kV and the magnification was 5000 times. For example, as shown in Figure 7, the lithium deposition morphology was mossy; as shown in Figure 8, the lithium deposition morphology was planar; and as shown in Figure 9, the lithium deposition morphology was dendritic, that is, lithium dendrites were formed.

[0235] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte, characterized in that: The electrolyte includes a film-forming additive and metal ions; The reduction potential of the metal ion satisfy: Among them, M n+ represents the metal ion, n represents the valence of the metal ion, R represents the ideal gas constant, T represents the temperature, C represents the molar concentration of the metal ion in the electrolyte, F represents the Faraday constant, represents the reductive decomposition potential of the film-forming additive.

2. The electrolyte according to claim 1, characterized in that The molar concentration C of the metal ions in the electrolyte satisfies: 0.01M≤C≤0.2M.

3. The electrolyte according to claim 1 or 2, characterized in that The mass ratio m1 / m2 of the film-forming additive to the electrolyte satisfies: 0.1%≤m1 / m2≤10%.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The metal ions include: Mg 2+ 、Zn 2+ Sn 2+ 、Ag + 、In 3+ , Ga 3+ , Sb 3+ At least one of, optionally, the metal ions include Mg 2+ .

5. The electrolyte according to any one of claims 1 to 4, characterized in that The film-forming additive comprises at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl sulfite, propylene sulfite, and lithium difluorooxalatoborate.

6. The electrolyte according to any one of claims 1 to 5, characterized in that The electrolyte includes: an inorganic salt, wherein the inorganic salt includes the metal ion and an anion; The anions include at least one of acetate, tetrafluoroborate, perchlorate, nitrate, carbonate, acetate, bistrifluoromethylsulfonyl imide, trifluoromethanesulfonate, difluorooxalatoborate, dioxalatoborate, methanesulfonate, hexafluorophosphate, and halogen anions.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The electrolyte includes: a solvent; the solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate or butyl propionate.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The electrolyte includes a lithium salt; the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(oxalyl)borate.

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

10. A lithium ion battery, characterized in that: include: Electrolyte; A negative electrode plate, wherein a composite layer is formed on the surface of the negative electrode plate close to the electrolyte, the composite layer includes a metal layer and a solid electrolyte interface film, the metal layer is located between the surface of the negative electrode plate and the solid electrolyte interface film, and the metal layer includes a metal element and / or a lithium-metal alloy.

11. The lithium ion battery according to claim 10, characterized in that: The electrolyte includes metal ions, which are consistent with the element of the metal element and / or the element of the metal in the lithium-metal alloy.

12. The lithium ion battery according to claim 11, characterized in that: The molar concentration C1 of the metal ions in the electrolyte satisfies: 0.001M≤C1≤0.18M.

13. The lithium ion battery according to claim 11 or 12, characterized in that: The metal ions include: Mg 2+ 、Zn 2+ Sn 2+ 、Ag + 、In 3+ , Ga 3+ , Sb 3+ At least one of, optionally, the metal ions include Mg 2+ .

14. The lithium ion battery according to any one of claims 10 to 13, characterized in that: The electrolyte further includes a film-forming additive, and the film-forming additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl sulfite, propylene sulfite, and lithium difluorooxalatoborate.

15. A formation method for a lithium ion battery as claimed in claim 9, characterized in that: The formation method includes a charging stage, and the charging stage includes: In the first charging stage, the lithium-ion battery is charged with a first current I1 to a first voltage U1 at a constant current; In the second charging stage, the lithium-ion battery is charged at a constant voltage under the first voltage U1 for a duration of T; In the third charging stage, the lithium-ion battery is charged with a constant current to a cut-off voltage; In the fourth charging stage, the lithium-ion battery is charged at a constant voltage under the cut-off voltage until the current is less than or equal to the cut-off current; Wherein, the reduction potential of the metal ion Higher than the reduction decomposition potential of the film-forming additive The negative electrode potential of the lithium ion battery at the first voltage U1 is higher than the reduction decomposition potential of the film-forming additive. and lower than the reduction potential of the metal ion T>0min.

16. The chemical formation method according to claim 15, characterized in that: The formation method includes a discharge stage, and the discharge stage includes: The lithium ion battery is discharged at a constant current to a cut-off voltage.

17. The chemical formation method according to claim 15 or 16, characterized in that: 0min<T≤60min; optionally, 10min≤T≤20min.

18. The chemical formation method according to any one of claims 15 to 17, characterized in that: The first voltage U1 satisfies: U1=U X +U M ; Among them, U X represents the voltage of the lithium-ion battery when the metal ions begin to be reduced, U M Represents a constant, 0V≤U M ≤0.3V; Optionally, 0.05V≤U M ≤0.15V.

19. The chemical formation method according to any one of claims 15 to 18, characterized in that: The first current I1 satisfies: 0.01C≤I1≤0.1C.

20. The chemical formation method according to any one of claims 15 to 19, characterized in that: The metal ions include: Mg 2+ 、Zn 2+ Sn 2+ 、Ag + 、In 3+ , Ga 3+ , Sb 3+ At least one of, optionally, the metal ions include Mg 2+ .

21. The chemical formation method according to any one of claims 15 to 20, characterized in that: The film-forming additive comprises at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl sulfite, propylene sulfite, and lithium difluorooxalatoborate.

22. The chemical formation method according to any one of claims 15 to 21, characterized in that: The electrolyte includes: an inorganic salt, wherein the inorganic salt includes the metal ion and an anion; The anions include at least one of acetate, tetrafluoroborate, perchlorate, nitrate, carbonate, acetate, bistrifluoromethylsulfonyl imide, trifluoromethanesulfonate, difluorooxalatoborate, dioxalatoborate, methanesulfonate, hexafluorophosphate, and halogen anions.

23. An electrical device, characterized in that: The electrical device comprises the lithium ion battery as claimed in claim 9, and / or the lithium ion battery as claimed in any one of claims 10-14, and / or the lithium ion battery formed by the formation method as claimed in any one of claims 15-22.

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