Battery monomer, battery and electric device

Abstract

The invention discloses a battery monomer, a battery and a power utilization device, the battery monomer comprises an electrolyte, the electrolyte comprises a solvent, the solvent comprises a fluoro-ether solvent as shown in formula I, and R1 is C1-C5 alkyl; r2 is an alkylene group of C1 to C5; r3 is an H atom, an F atom, a C1-C5 alkyl group or a C1-C5 fluoroalkyl group; x is a methylene group, a monofluoromethylene group or a difluoromethylene group; y is a methylene group, a monofluoromethylene group or a difluoromethylene group; x, Y and R3 satisfy at least one of the following conditions (1) to (2): (1) at least one of X and Y is a monofluoromethylene group or a difluoromethylene group; (2) R3 represents an F atom; according to the invention, the long cycle life of the battery in normal temperature and high temperature environments can be realized while the battery has good rate capability. # imgabs0 #

Description

Technical Field

[0001] The present application relates to a battery cell, a battery and an electrical device. Background Art

[0002] With the realization of application scenarios such as long-range electric vehicles, drones, and electric aircraft, the demand for high-energy-density batteries is increasing. The energy density of traditional lithium-ion batteries with carbon-based materials as negative electrodes can no longer meet the demand, so a battery system with higher energy density is needed. Lithium metal batteries have attracted widespread attention due to their high energy density, but the high-temperature cycle stability and rate performance of lithium metal batteries need to be further improved. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0003] The present application provides a battery cell, a battery, and an electrical device, which can enable the battery to have good rate performance while achieving a long cycle life in normal and high temperature environments.

[0004] In a first aspect, the present application provides a battery cell, wherein the battery cell includes an electrolyte, the electrolyte includes a solvent, and the solvent includes a fluoroether solvent represented by Formula I.

[0005]

[0006] R1 is a C1-C5 alkyl group; R2 is a C1-C5 alkylene group; R3 is a H atom, a F atom, a C1-C5 alkyl group or a C1-C5 fluoroalkyl group; X is a methylene group, a monofluoromethylene group or a difluoromethylene group; Y is a methylene group, a monofluoromethylene group or a difluoromethylene group.

[0007] X, Y, and R3 satisfy at least one of the following conditions (1) to (2): (1) at least one of X and Y is a monofluoromethylene group or a difluoromethylene group; (2) R3 is a F atom.

[0008] The present application provides a class of specially designed fluoroether solvents, which have two ether oxygen atoms in their molecular structure, namely, the ether oxygen atom connected to X and Y, and the ether oxygen atom connected to R1 and R2. The ether oxygen atom connected to X and Y satisfies that at least one of X and Y is a fluoromethylene or difluoromethylene, and / or R3 is an F atom, that is, at least one H atom on the two adjacent alpha-C of the ether oxygen atom connected to X and Y is replaced by an F atom, that is, at least one C-H bond is converted into a C-F bond, thereby making the ether oxygen atom lose its solvating ability, but has good effects of promoting negative electrode film formation characteristics and improving positive electrode oxidation resistance. The ether oxygen atom connected to R1 and R2 satisfies that R1 is a C1-C5 alkyl group and R2 is a C1-C5 alkylene group, that is, the H atom at the C atom position adjacent to the ether oxygen atom is not replaced by an F atom, thereby making the ether oxygen atom have good solvating ability and can dissolve the electrolyte salt well.

[0009] Therefore, the fluoroether solvent provided in the embodiment of the present application can improve the film-forming properties of the negative electrode and enhance the oxidation resistance of the positive electrode while retaining good solvation ability, thereby enabling the battery cell provided in the embodiment of the present application to have good rate performance while achieving a long cycle life in normal and high temperature environments.

[0010] In some embodiments, X, Y, and R3 satisfy at least one of the following conditions (1) to (2): (1) X is a methylene group, and Y is a monofluoromethylene group or a difluoromethylene group; (2) X is a methylene group, and R3 is a F atom.

[0011] The fluorine substitution position on the two adjacent alpha-Cs of the ether oxygen atom connected by X and Y is at the terminal position, thereby enabling the fluoroether solvent to better promote the film formation characteristics of the negative electrode and improve the oxidation resistance of the positive electrode. It can also enable the fluoroether solvent to better dissolve the electrolyte salt, thereby enabling the battery monomer to have better rate performance and longer cycle life.

[0012] In some embodiments, X is monofluoromethylene or difluoromethylene, Y is monofluoromethylene or difluoromethylene, and R3 is a H atom, a F atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group.

[0013] In some embodiments, X is monofluoromethylene or difluoromethylene, Y is monofluoromethylene or difluoromethylene, and R3 is an H atom, an F atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group.

[0014] In some embodiments, X is monofluoromethylene or difluoromethylene, Y is monofluoromethylene or difluoromethylene, and R3 is an F atom.

[0015] In some embodiments, X is a monofluoromethylene group or a difluoromethylene group, Y is a methylene group, and R3 is a H atom, a F atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group.

[0016] In some embodiments, X is monofluoromethylene or difluoromethylene, Y is methylene, and R3 is a H atom, an F atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group.

[0017] In some embodiments, X is monofluoromethylene or difluoromethylene, Y is methylene, and R3 is an F atom.

[0018] In some embodiments, X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is a H atom, a F atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group.

[0019] In some embodiments, X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is a H atom, an F atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group.

[0020] In some embodiments, X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is a F atom.

[0021] In some embodiments, X is a methylene group, Y is a methylene group, and R3 is a F atom.

[0022] In some embodiments, R1 is a C1-C3 alkyl group, and / or R2 is a C1-C3 alkylene group. Fluoroether solvents have a small molecular structure and are better at dissolving electrolyte salts.

[0023] In some embodiments, R1 is a methyl group, and / or R2 is a methylene group. Fluoroether solvents have a small molecular structure and are better at dissolving electrolyte salts.

[0024] In some embodiments, the fluoroether solvent comprises one or more of the following,

[0025]

[0026]

[0027] In some embodiments, the fluoroether solvent includes one or more of A-1 to A-3, A-6 to A-10, A-14 to A-16, and A-20 to A-26. These fluoroether solvents have smaller molecular structures, which facilitate dissolving electrolyte salts, thereby enabling the battery cells to have better rate performance and longer cycle life.

[0028] In some embodiments, the fluoroether solvent includes one or more of A-2 and A-3. In this case, the molecular structure of these fluoroether solvents is relatively small, which is conducive to dissolving the electrolyte salt. At the same time, the position and amount of fluorine substitution are appropriate. This can completely deprive one of the ether oxygen atoms of its coordination ability while leaving the coordination ability of the other ether oxygen atom almost unaffected. Therefore, the negative electrode film-forming performance and positive electrode oxidation resistance of the fluoroether solvent can be significantly improved, and the electrolyte can also have good ion conductivity, thereby achieving good rate performance and cycle performance.

[0029] In some embodiments, the mass percentage of the fluoroether solvent in the solvent is 100%.

[0030] In some embodiments, the mass proportion of the fluoroether solvent in the solvent is greater than or equal to 30% and less than 100%, and can be optionally greater than 50% and less than or equal to 80%.

[0031] In some embodiments, the solvent further comprises an inert solvent, and the inert solvent comprises benzene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-dimethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(difluoromethoxy)ethane, 1,2-bis(trifluoromethoxy)ethane, 1,2-diethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl)ether, bis(2,2- One or more of trifluoromethyl ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl-2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, and bis(1,1,2,2-tetrafluoroethyl) ether. These inert solvents can not only further reduce the viscosity of the electrolyte, but also improve the film forming properties and oxidation resistance of the positive and negative electrodes of the electrolyte, thereby making the battery monomer have better overall performance.

[0032] In some embodiments, the mass proportion of the inert solvent in the solvent is greater than 0 and less than or equal to 70%, and can be 20%-50%. An appropriate amount of inert solvent can further reduce the viscosity of the electrolyte, but due to the poor ability of inert solvent to dissolve electrolyte salts, its content should not be too high.

[0033] In some embodiments, the electrolyte includes an electrolyte salt, and the electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0034] In some embodiments, the concentration of the electrolyte salt in the electrolyte solution is 0.5 mol / L-4 mol / L.

[0035] In some embodiments, the battery cell comprises a lithium metal battery cell or a negative electrode-free lithium metal battery cell.

[0036] In a second aspect, the present application provides a battery comprising the battery cell of the first aspect of the present application.

[0037] In a third aspect, the present application provides an electrical device comprising the battery according to the second aspect of the present application.

[0038] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces 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 those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0040] Figure 1 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0041] Figure 2 It is an exploded schematic diagram of an embodiment of a battery cell of the present application.

[0042] Figure 3 It is a schematic diagram of an embodiment of a battery module of the present application.

[0043] Figure 4 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0044] Figure 5 yes Figure 4 An exploded schematic diagram of an embodiment of a battery pack is shown.

[0045] Figure 6 It is a schematic diagram of an embodiment of an electric device including the battery of the present application as a power source.

[0046] In the accompanying drawings, which are not necessarily drawn to scale, reference numerals are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0047] Below, the embodiments of the battery cell, battery, 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 structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of 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.

[0048] " 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.

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0050] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0051] 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.

[0052] Unless otherwise specified, in this application, the terms "first", "second", "third", etc. are used to distinguish different objects rather than to describe a specific order or a primary-secondary relationship.

[0053] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0054] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0055] The battery mentioned in the embodiments of the present application may include one or more battery cells to provide a single physical module with higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack.

[0056] A battery cell is the smallest unit that makes up a battery and can independently realize the function of charging and discharging. A battery cell can be cylindrical, rectangular or other shapes, etc., which is not limited in the embodiments of the present application. Figure 1 As an example, a battery cell 5 having a rectangular parallelepiped structure is shown.

[0057] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0058] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0059] The battery cell includes an electrode assembly, which may be a wound structure or a laminated structure, and the present invention is not limited thereto.

[0060] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging can also be a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as one or more of aluminum-plastic film, polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0061] In some embodiments, as Figure 2 As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate. The base plate and side plates together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity. The cover plate 53 is used to cover the opening, thereby sealing the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and can be adjusted according to needs.

[0062] In some embodiments, battery cells may be assembled into a battery module. A battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0063] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0064] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0065] Figure 4 and Figure 5 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, a battery pack 1 may include a housing and multiple battery modules 4 disposed therein. The housing comprises an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the housing.

[0066] Unlike lithium-ion battery cells, the electrolytes of lithium metal battery cells and negative electrode-free lithium metal battery cells usually do not use a large amount of ester solvents, but rather a large amount of ether solvents. However, the ether solvents currently used, such as ethylene glycol dimethyl ether, have problems such as decomposition and gas production at the negative electrode and oxidative decomposition at the positive electrode, which makes it impossible to achieve a longer cycle life for the battery cells. By replacing fluorine in ether solvents, defluorination can be promoted on the negative electrode side to generate fluorine-rich components such as lithium fluoride, thereby improving the negative electrode film formation. At the same time, the oxidation resistance of the ether solvent structure can be significantly improved, which is beneficial to improving the stability of the battery cells to the positive electrode during long cycles.

[0067] Traditional fluorination methods for ether solvents can be broadly categorized into two types. One involves replacing all adjacent alpha-C atoms with at least one fluorine atom. In this fluorinated ether structure, due to the strong electron-withdrawing effect of the fluorine atoms, all ether oxygen atoms lose their ability to coordinate with lithium ions. Consequently, these fluorinated ether solvents can be added to electrolytes as inert solvents to further promote negative electrode film formation, improve positive electrode oxidation resistance, and reduce electrolyte viscosity. However, their ability to dissolve electrolyte salts is generally poor, making them unsuitable for use as solvents. Another approach is to perform fluorine substitution on the beta-C or more distant C atom positions of all ether oxygen atoms. This fluorine substitution can also improve negative electrode film formation and enhance positive electrode oxidation resistance. Since the F atoms are far away from the ether oxygen atoms, the ether oxygen atoms can still retain some of their ability to dissolve electrolyte salts, and thus can be used as solvents for dissolving electrolyte salts. However, although these fluoroether solvents still have the ability to partially dissolve electrolyte salts, since all ether oxygen atoms are still affected by the F atoms, the ion conductivity of these fluoroether solvents is often low, affecting the rate performance of the battery cell. In addition, when an ether solvent has only one ether oxygen atom, its ability to dissolve electrolyte salts is inherently limited. At this time, if the C-H bonds at the beta-C or more distant C atom positions of the ether oxygen atom are all CF bonds, the ability of these fluoroether solvents to dissolve electrolyte salts is generally also relatively poor.

[0068] Based on this, an embodiment of the present application provides a battery cell that uses an electrolyte including a specially designed fluoroether solvent. The electrolyte can enable the battery cell to have good rate performance while achieving a long cycle life in normal and high temperature environments.

[0069] The battery cells provided in the embodiments of the present application may include lithium metal battery cells and negative electrode-free lithium metal battery cells.

[0070] The battery cell provided in the embodiments of the present application includes an electrolyte, and the electrolyte includes a solvent.

[0071] The solvent includes a fluoroether solvent represented by formula I.

[0072]

[0073] R1 is a C1-C5 alkyl group. R2 is a C1-C5 alkylene group. R3 is a hydrogen atom, a fluorine atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group. X is a methylene group, a monofluoromethylene group, or a difluoromethylene group. Y is a methylene group, a monofluoromethylene group, or a difluoromethylene group.

[0074] X, Y, and R3 satisfy at least one of the following conditions (1) to (2): (1) at least one of X and Y is a monofluoromethylene group or a difluoromethylene group; (2) R3 is a F atom.

[0075] The present application provides a class of specially designed fluoroether solvents, which have two ether oxygen atoms in their molecular structure, namely, the ether oxygen atom connected to X and Y, and the ether oxygen atom connected to R1 and R2. The ether oxygen atom connected to X and Y satisfies that at least one of X and Y is a fluoromethylene or difluoromethylene, and / or R3 is an F atom, that is, at least one H atom on the two adjacent alpha-C of the ether oxygen atom connected to X and Y is replaced by an F atom, that is, at least one C-H bond is converted into a C-F bond, thereby making the ether oxygen atom lose its solvating ability, but has good effects of promoting negative electrode film formation characteristics and improving positive electrode oxidation resistance. The ether oxygen atom connected to R1 and R2 satisfies that R1 is a C1-C5 alkyl group and R2 is a C1-C5 alkylene group, that is, the H atom at the C atom position adjacent to the ether oxygen atom is not replaced by an F atom, thereby making the ether oxygen atom have good solvating ability and can dissolve the electrolyte salt well.

[0076] Therefore, the fluoroether solvent provided in the embodiment of the present application can improve the film-forming properties of the negative electrode and enhance the oxidation resistance of the positive electrode while retaining good solvation ability, thereby enabling the battery cell provided in the embodiment of the present application to have good rate performance while achieving a long cycle life in normal and high temperature environments.

[0077] In some embodiments, X, Y, and R3 satisfy at least one of the following conditions (1) to (2): (1) X is a methylene group, and Y is a monofluoromethylene group or a difluoromethylene group; (2) X is a methylene group, and R3 is a F atom. That is, the fluorine substitution positions on the two adjacent alpha-C carbon atoms of the ether oxygen atom connected to X and Y are at the terminal positions. This can make the fluoroether solvent better in promoting the film formation characteristics of the negative electrode and improving the oxidation resistance of the positive electrode. It can also make the fluoroether solvent better in dissolving the electrolyte salt, thereby making the battery monomer have better rate performance and longer cycle life.

[0078] This is because the two ether oxygen atoms in the fluoroether solvent can chelate with lithium ions in the electrolyte to form a solvation structure, thereby enhancing the fluoroether solvent's ability to dissolve electrolyte salts. When the fluorine substitution position on the two adjacent alpha-C carbon atoms of the ether oxygen atoms connected by X and Y is between the two ether oxygen atoms, the F atom will affect the chelation between the two ether oxygen atoms and the lithium ions in the electrolyte.

[0079] In some embodiments, X is a monofluoromethylene or difluoromethylene, Y is a monofluoromethylene or difluoromethylene, and R3 is an H atom, an F atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group. Alternatively, X is a monofluoromethylene or difluoromethylene, Y is a monofluoromethylene or difluoromethylene, and R3 is an H atom, an F atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group. More preferably, X is a monofluoromethylene or difluoromethylene, Y is a monofluoromethylene or difluoromethylene, and R3 is an F atom.

[0080] In some embodiments, X is a monofluoromethylene or difluoromethylene group, Y is a methylene group, and R3 is an H atom, an F atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group. Alternatively, X is a monofluoromethylene or difluoromethylene group, Y is a methylene group, and R3 is an H atom, an F atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group. More preferably, X is a monofluoromethylene or difluoromethylene group, Y is a methylene group, and R3 is an F atom.

[0081] In some embodiments, X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is an H atom, an F atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group. Alternatively, X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is an H atom, an F atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group. More preferably, X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is an F atom.

[0082] At this time, the fluorine substitution position on the two adjacent alpha-C of the ether oxygen atom connected by X and Y is at the terminal position, which can make the fluoroether solvent better have the effect of promoting the film formation characteristics of the negative electrode and improving the oxidation resistance of the positive electrode, and can also make the fluoroether solvent have a better ability to dissolve the electrolyte salt, thereby making the battery monomer have better rate performance and longer cycle life.

[0083] In some embodiments, X is a methylene group, Y is a methylene group, and R3 is a F atom.

[0084] In some embodiments, R1 is a C1-C3 alkyl group. Alternatively, R1 is a methyl group.

[0085] Fluoroether solvents have a smaller molecular structure and are better at dissolving electrolyte salts.

[0086] In some embodiments, R2 is a C1-C3 alkylene group. Alternatively, R2 is a methylene group.

[0087] Fluoroether solvents have a smaller molecular structure and are better at dissolving electrolyte salts.

[0088] In addition, when R2 is a methylene group, the two ether oxygen atoms of the fluoroether solvent can be chelated with the lithium ions in the electrolyte to form a better solvation structure, thereby better improving the ability of the fluoroether solvent to dissolve the electrolyte salt.

[0089] In some embodiments, the fluoroether solvent may include one or more of the following,

[0090]

[0091]

[0092] Alternatively, the fluoroether solvent may include one or more of A-1 to A-3, A-6 to A-26.

[0093] At this time, the fluorine substitution position on the two adjacent alpha-C of the ether oxygen atom connected by X and Y is at the terminal position, which can make the fluoroether solvent better have the effect of promoting the film formation characteristics of the negative electrode and improving the oxidation resistance of the positive electrode, and can also make the fluoroether solvent have a better ability to dissolve the electrolyte salt, thereby making the battery monomer have better rate performance and longer cycle life.

[0094] Alternatively, the fluoroether solvent may include one or more of A-1 to A-3, A-6 to A-10, A-14 to A-16, A-20 to A-26.

[0095] Alternatively, the fluoroether solvent may include one or more of A-1 to A-3, A-7 to A-10, A-14 to A-16.

[0096] At this time, the molecular structure of these fluoroether solvents is relatively small, which is conducive to dissolving the electrolyte salt, thereby enabling the battery monomer to have better rate performance and longer cycle life.

[0097] Alternatively, the fluoroether solvent may include one or more of A-2 and A-3.

[0098] At this time, the molecular structure of these fluoroether solvents is relatively small, which is conducive to dissolving electrolyte salts. At the same time, the position and amount of fluorine substitution are appropriate. Therefore, on the one hand, one of the ether oxygen atoms can completely lose its coordination ability, and on the other hand, the coordination ability of the other ether oxygen atom can be almost unaffected. Therefore, the negative electrode film-forming performance and positive electrode oxidation resistance of the fluoroether solvent can be significantly improved, and the electrolyte can also have good ion conductivity, thereby achieving good rate performance and cycle performance.

[0099] The present application embodiment illustratively provides the preparation method of compound A-3. Other compounds of the present application embodiment can be prepared with reference to this exemplary method. According to the preparation method of exemplary compound, those skilled in the art can easily obtain the specific method for realizing each synthesis step from relevant scientific literature or standard textbooks in this field. Unless otherwise specified, commercially available or known compounds in the literature are used as the raw materials for synthesis. Those skilled in the art of organic synthesis will recognize that, in order to optimize the purpose of generating the compound described in the present application, the nature and order of the proposed synthesis steps can be changed.

[0100] The processes described in the examples of the present application can be monitored by any suitable method known in the art. For example, product formation can be monitored by spectroscopic means such as nuclear magnetic resonance spectroscopy (NMR, e.g. 1 H. 13 C or 19 F), infrared spectroscopy (IR), spectrophotometry (e.g., UV-visible), mass spectrometry (MS), or by chromatography, such as high performance liquid chromatography (HPLC), gas chromatography (GC), gel permeation chromatography (GPC), or thin layer chromatography (TLC).

[0101] Illustratively, compound A-3 can be prepared as follows.

[0102] Ethylene glycol methyl ether (10 g, 0.131 mol) was added to a 500 mL two-necked flask under argon atmosphere. Then, 150 mL of anhydrous tetrahydrofuran (THF) was added to dissolve the mixture. After stirring and cooling to 0°C, sodium hydride (60%, 6.3 g, 0.158 mol) was added to the reaction flask. The mixture was incubated for 15 minutes, then heated to room temperature and stirred for 1 hour. Finally, trifluoromethyl 4-methylbenzenesulfonate (29.8 g, 0.124 mol) was added and stirred at room temperature for 2 hours. After completion of the reaction, the reaction was quenched with ice water and extracted with ether (50 mL x 3). The organic phase was washed with saturated brine, separated, and then dried over anhydrous sodium sulfate. The organic phase was filtered and the filtrate was concentrated under reduced pressure to remove the organic solvent to obtain a crude product. The crude product was finally distilled under reduced pressure to obtain 12.95 g of a colorless liquid, i.e., compound A-3. Molar yield: 68.61%.

[0103] 1H NMR (CDCl3, 400MHz), δ (ppm): 3.54 (m, 4H), 3.24 (s, 3H). 13 C NMR (CDCl3, 100MHz), δ (ppm): 120.2, 72.8, 53.9, 52.4. 19 F NMR(CDCl3,376MHz),δ(ppm):-79.2.HRMS(ESI+)m / z[M] + calcd.for C4H7F3O2:144.0398.found:144.0389.

[0104] In some embodiments, the mass percentage of the fluoroether solvent in the solvent may be 100%.

[0105] In some embodiments, the mass proportion of the fluoroether solvent in the solvent can be greater than or equal to 30% and less than 100%, for example, it can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or a range consisting of any of the above values.

[0106] Optionally, the mass proportion of the fluoroether solvent in the solvent may be 50%-80%, more preferably 55%-80%, 60%-80%.

[0107] In some embodiments, the solvent may further include an inert solvent. An inert solvent refers to a solvent that cannot or barely dissolve the electrolyte salt.

[0108] The molecular structure of some fluoroether solvents provided in the embodiments of the present application is slightly larger, which will make the viscosity of the electrolyte slightly higher. In order to further reduce the viscosity of the electrolyte, the fluoroether solvent can be used in combination with an inert solvent, thereby further improving the rate performance of the battery cell.

[0109] Alternatively, the inert solvent may include benzene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-dimethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(difluoromethoxy)ethane, 1,2-bis(trifluoromethoxy)ethane, 1,2-diethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl)ether, bis(2,2-difluoroethyl)ether, 1 ,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, bis(1,1,2,2-tetrafluoroethyl) ether.

[0110] These inert solvents can not only further reduce the viscosity of the electrolyte, but also improve the positive and negative electrode film-forming properties and oxidation resistance of the electrolyte, thereby making the battery cells have better overall performance.

[0111] Alternatively, the inert solvent may include one or more of benzene and bis(2,2-difluoroethyl)ether.

[0112] These inert solvents have low cost, suitable viscosity, suitable boiling point, and good positive and negative electrode film forming properties and stability, thus enabling battery cells to have better overall performance.

[0113] Optionally, the mass proportion of the inert solvent in the solvent can be greater than 0 and less than or equal to 70%, for example, it can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range consisting of any of the above values.

[0114] Optionally, the mass proportion of the inert solvent in the solvent may be 20%-50%, more preferably 20%-45%, or 20%-40%.

[0115] An appropriate amount of inert solvent can further reduce the viscosity of the electrolyte, but since the inert solvent has a poor ability to dissolve electrolyte salts, its content should not be too high.

[0116] In some embodiments, the electrolyte includes an electrolyte salt, which may include but is not limited to one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiOTF), lithium difluorophosphate (LiDFP), lithium dioxalatoborate (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0117] Alternatively, the electrolyte salt may include one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0118] More alternatively, the electrolyte salt may include lithium bis(fluorosulfonyl)imide (LiFSI).

[0119] Lithium bis(fluorosulfonyl)imide can decompose on the surface of the negative electrode to form an SEI film component rich in inorganic fluorine, which is beneficial to improving the cycle life of the battery cell. At the same time, it also has good oxidation stability and can support high voltage of the battery cell, such as a long cycle life above 4.0V.

[0120] Alternatively, the concentration of the electrolyte salt in the electrolyte solution may be 0.5 mol / L-4 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, or a range consisting of any of the foregoing values. More preferably, the concentration of the electrolyte salt in the electrolyte solution may be 1 mol / L-3 mol / L.

[0121] Methods for preparing an electrolyte are well known. For example, an electrolyte salt and a solvent can be uniformly mixed to obtain an electrolyte. During the preparation process, the order in which the materials are added is not particularly limited; the materials can be added simultaneously or in batches.

[0122] The components and their contents in the electrolyte can be determined using conventional methods in the art. For example, the electrolyte in the battery cell can be extracted, and the various solvents and electrolyte salts in the electrolyte can be separated using gas chromatography. Each component can then be subjected to high-precision mass spectrometry and nuclear magnetic resonance spectroscopy to confirm its specific structure. After confirming the specific structure of each component, electrolyte salt solutions with different standard concentrations are prepared. The relationship between electrolyte salt content and peak area is fitted using the results of ion chromatography. By testing the electrolyte sample using ion chromatography, a quantitative result for the lithium salt concentration can be obtained. A mixture of solvent components with known ratios is prepared, and a solvent with known concentration is added as an internal standard. The relative correction factors for the peak area and concentration relationship of the internal standard for each component are obtained using the gas chromatography results. Gas chromatography is then performed on the electrolyte sample with the known internal standard added to obtain a quantitative result for the specific ratio of each solvent component.

[0123] The battery cell includes an electrolyte and an electrode assembly, and the electrode assembly includes a positive electrode sheet and a negative electrode sheet.

[0124] The electrolyte provided in the embodiments of the present application can enable the battery cells to have good rate performance while achieving a long cycle life in normal and high temperature environments.

[0125] [Positive electrode]

[0126] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0127] The positive electrode active material includes a material capable of extracting and inserting lithium. Optionally, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.

[0128] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0129] In some embodiments, in order to further improve the energy density of the battery cell, the positive electrode active material may include a general formula of Li a Ni b Co c M d O e A f One or more lithium transition metal oxides and modified compounds thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more of N, F, S and Cl.

[0130] In some embodiments, as examples, the positive electrode active material may include but is not limited to LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 One or more of O2, LiFePO4, LiMnPO4, and their respective modified compounds.

[0131] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0132] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0133] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0134] The positive electrode film layer can be formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional positive electrode conductive agent, an optional positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0135] [Negative electrode]

[0136] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a lithium-containing layer disposed on at least one surface of the negative electrode current collector.

[0137] In some embodiments, the material in the lithium-containing layer may include one or more of lithium element and lithium alloy.

[0138] A lithium alloy may be an alloy of metallic lithium and other metallic elements or non-metallic elements. For example, the other metallic elements in the lithium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, and the non-metallic elements in the lithium alloy may include one or more of boron, carbon, and silicon.

[0139] In some embodiments, the negative electrode sheet may include a negative electrode current collector but not a lithium-containing layer, thereby assembling to form a negative electrode-free lithium metal battery cell.

[0140] A negative electrode-free lithium metal battery cell generally refers to a battery cell in which a negative electrode active material layer is not actively provided on the negative electrode side during the manufacturing process of the battery cell. For example, a negative electrode active material layer is not formed by coating or deposition of a carbonaceous active material layer at the negative electrode during the manufacturing process of the battery cell. During the first charge, ions gain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metal phase. During discharge, the metal can be converted into metal ions and return to the positive electrode, realizing cyclic charge and discharge. Compared with other battery cells, negative electrode-free lithium metal battery cells can achieve higher energy density because they do not have a negative electrode active material layer.

[0141] In some embodiments, to improve battery cell performance, the negative electrode side of the negative electrode-free lithium metal battery cell may also be provided with some conventional substances that can be used as negative electrode active materials, such as carbon materials. Although these substances have a certain capacity, due to their low content and their non-use as the primary negative electrode active material in the battery cell, the battery cell thus constructed can still be considered a negative electrode-free lithium metal battery cell.

[0142] The CB value of a negative electrode-free lithium metal battery cell is typically very small. For example, in some embodiments, the CB value of a negative electrode-free lithium metal battery cell can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery cell divided by the unit area capacity of the positive electrode. Because a negative electrode-free lithium metal battery cell contains no or only a small amount of negative electrode active material, the unit area capacity of the negative electrode is small, and thus the CB value is very small, for example, typically less than or equal to 0.1.

[0143] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. As examples of metal foils, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil may be used. As examples of three-dimensional porous current collectors, copper mesh, nickel mesh, aluminum mesh, foam copper, foam nickel, and foam aluminum may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0144] [Isolation film]

[0145] The battery assembly may also include a separator. This separator can be positioned between the positive and negative electrode sheets, primarily to prevent internal short circuits. This application does not specifically limit the type of separator; any known porous membrane with good chemical and mechanical stability may be used.

[0146] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of fiberglass, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and polyimide. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0147] The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, separator, negative electrode sheet and electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process. The electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging and standing, a battery cell is obtained. Multiple battery cells can be further connected in series, in parallel, or in a mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel, or in a mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0148] Electrical devices

[0149] The present application also provides an electrical device, which includes a battery provided in the present application. The battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0150] The electric device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0151] Figure 6 The diagram is a schematic diagram of an exemplary 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 this device, a battery pack or battery module can be used.

[0152] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0153] Example

[0154] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0155] Example 1

[0156] (1) Preparation of electrolyte

[0157] Solvent A-3 (structure shown above) and the inert solvent bis(2,2-difluoroethyl) ether were mixed in a mass ratio of 6:4 to form a solvent mother liquor. 1.87 g of lithium bis(fluorosulfonyl)imide (LiFSI) was added to 5 ml of the solvent mother liquor and stirred thoroughly to form a colorless, transparent electrolyte solution.

[0158] (2) Preparation of positive electrode sheet

[0159] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent acetylene black, and binder PVDF were mixed in a mass ratio of 98:1:1, added to the solvent N-methylpyrrolidone (NMP), and stirred until the system became uniform to obtain a positive electrode slurry with a solid content of approximately 70%. The positive electrode slurry was evenly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. It was then cut into 40mm×50mm rectangles as positive electrode sheets for later use. The coating amount was 12.5mg / cm 2 .

[0160] (3) Preparation of negative electrode sheet

[0161] A 50 μm thick lithium foil was laminated to a 12 μm thick copper foil by roller pressing, and then cut into a 41 mm × 51 mm rectangle as a negative electrode sheet for later use.

[0162] (4) Preparation of isolation membrane

[0163] The polyethylene porous film was cut into a rectangle of 45 mm × 55 mm and used as a separator for later use.

[0164] (5) Preparation of batteries

[0165] A cut positive electrode sheet and two cut negative electrode sheets were stacked together, separated by a separator to form an electrode assembly. The electrode assembly was placed in an aluminum-plastic film bag, and 0.30g of the prepared electrolyte was injected. After vacuum hot pressing and resting for at least 6 hours, a lithium metal battery cell was obtained. The rated capacity of the battery cell was 70mAh.

[0166] Normal temperature cycle performance test

[0167] At 25°C, the battery cell prepared above was charged at a constant current of 0.2C (14mA) to 4.3V. It was then charged at a constant voltage until the current reached 0.1C (7mA). At this point, the battery cell was fully charged, and the charge capacity at this point was recorded as the first cycle charge capacity. After the battery cell was allowed to rest for 5 minutes, it was discharged at a constant current of 1C (70mA) to 2.8V. This constituted a cycle charge and discharge process, and the discharge capacity at this point was recorded as the first cycle discharge capacity. The battery cell was subjected to a cyclic charge and discharge test according to the above method, and the discharge capacity after each cycle was recorded until the discharge capacity of the battery cell decayed to 80% of the first cycle discharge capacity. This indicated the end of the battery cell's lifespan, and the number of cycles at this point was used to characterize the battery cell's room-temperature cycle performance.

[0168] High temperature cycle performance test

[0169] At 60°C, the battery cell prepared above was charged at a constant current of 0.2C (14mA) to 4.3V. It was then charged at a constant voltage until the current reached 0.1C (7mA). At this point, the battery cell was fully charged, and the charge capacity at this point was recorded as the first cycle charge capacity. After the battery cell was allowed to rest for 5 minutes, it was discharged at a constant current of 1C (70mA) to 2.8V. This constituted a cycle charge and discharge process, and the discharge capacity at this point was recorded as the first cycle discharge capacity. The battery cell was subjected to a cyclic charge and discharge test according to the above method, and the discharge capacity after each cycle was recorded until the discharge capacity of the battery cell decayed to 80% of the first cycle discharge capacity. This indicated the end of the battery cell's lifespan, and the number of cycles at this point was used to characterize the high-temperature cycle performance of the battery cell.

[0170] Rate performance test

[0171] At 25°C, the prepared battery cell was charged at a constant current of 0.2C (14mA) to 4.3V, then continued to be charged at a constant voltage to a current of 0.1C (7mA). After standing for 5 minutes, it was discharged at a constant current of 1C (70mA) to 2.8V.

[0172] After cycling the battery cell for three cycles according to the above method, charge it at a constant current of 0.2C (14mA) to 4.3V, continue constant voltage charging to a current of 0.1C (7mA), let it rest for 5 minutes, and then discharge it at a constant current of 4C (280mA) to 2.8V. Cycle the battery cell for three cycles according to the above method (i.e., 4C rate discharge), and take the average value of the discharge capacity of the three cycles at 4C rate discharge as the discharge capacity of the battery cell at 4C, which can be used to evaluate the rate performance of the electrolyte in the lithium metal battery cell. The higher the value, the better the rate performance of the battery cell.

[0173] Comparative Example 1

[0174] The preparation and testing methods of the battery cells are similar to those in Example 1, except that the composition of the electrolyte is different.

[0175] Take 0.76g of lithium hexafluorophosphate and add it to 5ml of a solvent mother solution of ethylene carbonate and ethyl methyl carbonate in a mass ratio of 3:7, stir thoroughly to form a colorless and transparent electrolyte.

[0176] Comparative Example 2

[0177] The preparation and testing methods of the battery cells are similar to those in Example 1, except that the composition of the electrolyte is different.

[0178] 1.87 g of lithium bis(fluorosulfonyl)imide (LiFSI) was added to 5 ml of bis(2,2-difluoroethyl) ether solvent and stirred thoroughly. However, it was found that it did not dissolve and subsequent performance testing could not be performed.

[0179] Comparative Example 3

[0180] The preparation and testing methods of the battery cells are similar to those in Example 1, except that the composition of the electrolyte is different.

[0181] Take 1.87g of lithium bis(fluorosulfonyl)imide (LiFSI) and add 5ml of a solvent mother liquor prepared by mixing ethylene glycol dimethyl ether and bis(2,2-difluoroethyl) ether in a mass ratio of 6:4, and stir thoroughly to form a colorless and transparent electrolyte.

[0182] Comparative Example 4

[0183] The preparation and testing methods of the battery cells are similar to those in Example 1, except that the composition of the electrolyte is different.

[0184] Take 1.87g of lithium bis(fluorosulfonyl)imide (LiFSI) and add 5ml of a solvent mother liquor prepared by mixing 1,2-bis(2,2-difluoroethoxy)ethane and bis(2,2-difluoroethyl) ether in a mass ratio of 6:4, and stir thoroughly to form a colorless and transparent electrolyte.

[0185] Table 1

[0186]

[0187] The test results of Example 1 and Comparative Examples 1 to 4 show that lithium metal battery cells using the electrolyte comprising the specially designed fluoroether solvent of the present application have significantly improved cycle life at both room temperature and high temperature compared to lithium metal battery cells using conventional electrolytes for lithium-ion batteries. The electrolyte comprising the specially designed fluoroether solvent of the present application can provide lithium metal battery cells with long cycle life and good rate performance.

[0188] The electrolyte of Comparative Example 1 is an electrolyte used in lithium-ion battery cells. When used in lithium metal battery cells, this electrolyte cannot effectively improve the cycle performance of the lithium metal battery cells.

[0189] From the test results of Example 1 and Comparative Example 3, it can be seen that when the electrolyte includes a non-fluorinated ether solvent, the rate performance of the lithium metal battery monomer is good, but the stability is insufficient, resulting in an insufficient cycle life of the lithium metal battery monomer.

[0190] It can be seen from the test results of Example 1 and Comparative Example 4 that the electrolyte includes a fluoroether solvent in which the ether oxygen atom is substituted with fluorine at beta-C. Since the solvating ability of the fluoroether solvent is significantly reduced, the rate performance of the lithium metal battery monomer deteriorates, and the cycle life of the lithium metal battery monomer is not excellent enough.

[0191] Examples 2 to 6

[0192] The preparation and testing methods of the battery cells are similar to those of Example 1, except that the type of fluoroether solvent in the electrolyte is different, as detailed in Table 2. The specific structure of the fluoroether solvent is described above.

[0193] Table 2

[0194]

[0195] It can be seen from the test results of Examples 1 to 6 that the comprehensive performance of the battery cell can be further improved by further adjusting the structure of the fluoroether solvent.

[0196] Examples 7 to 10

[0197] The preparation and testing methods of the battery cells are similar to those in Example 1, except that the types of inert solvents in the electrolyte are different. See Table 3 for details.

[0198] Table 3

[0199]

[0200]

[0201] It can be seen from the test results of Example 1 and Examples 7 to 10 that the comprehensive performance of the battery cell can be further improved by further selecting a suitable inert solvent.

[0202] Examples 11 to 14

[0203] The preparation method and testing method of the battery cell are similar to those in Example 1, except that the mass proportions of the fluoroether solvent and the inert solvent in the electrolyte solvent are different. See Table 4 for details.

[0204] Table 4

[0205]

[0206] Examples 15 to 18

[0207] The preparation method and testing method of the battery cell are similar to those of Example 6, except that the mass proportions of the fluoroether solvent and the inert solvent in the electrolyte solvent are different. See Table 5 for details.

[0208] Table 5

[0209]

[0210] From the test results of Example 1 and Examples 11 to 14, it can be seen that by further adjusting the mass ratio of the fluoroether solvent to the inert solvent in the solvent, the overall performance of the battery cell can be further improved.

[0211] From the test results of Example 6 and Examples 15 to 18, it can be seen that by further adjusting the mass ratio of the fluoroether solvent to the inert solvent in the solvent, the overall performance of the battery cell can be further improved.

[0212] It can also be seen from the test results in Tables 4 and 5 that the inert solvent has a better improvement effect on the fluoroether solvent with a larger structural design, and the improvement on the cycle life and rate performance of the battery cell is also more obvious.

[0213] Examples 19 to 22

[0214] The preparation method and testing method of the battery cell are similar to those in Example 1, except that the molar concentration of the electrolyte salt in the electrolyte is different. See Table 6 for details.

[0215] Table 6

[0216]

[0217] It can be seen from the test results of Example 1 and Examples 19 to 22 that the overall performance of the battery cell can be further improved by further adjusting the molar concentration of the electrolyte salt.

[0218] Examples 23 to 24

[0219] The preparation method and testing method of the battery cell are similar to those in Example 1, except that the type of electrolyte salt in the electrolyte is different. See Table 7 for details.

[0220] Table 7

[0221]

[0222] From the test results in Table 7, it can be seen that the comprehensive performance of the battery cell can be further improved by further adjusting the type of electrolyte salt.

[0223] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical idea and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell comprising an electrolyte, wherein the electrolyte comprises a solvent, wherein: The solvent includes a fluoroether solvent represented by formula I, R1 is a C1-C5 alkyl group; R2 is a C1-C5 alkylene group; R3 is a H atom, a F atom, a C1-C5 alkyl group or a C1-C5 fluoroalkyl group; X is methylene, monofluoromethylene or difluoromethylene; Y is methylene, monofluoromethylene or difluoromethylene; X, Y, and R3 satisfy at least one of the following conditions (1) to (2): (1) At least one of X and Y is a monofluoromethylene or a difluoromethylene; (2) R3 is a F atom.

2. The battery cell according to claim 1, wherein: X, Y, and R3 satisfy at least one of the following conditions (1) to (2): (1) X is methylene, and Y is monofluoromethylene or difluoromethylene; (2) X is a methylene group, and R3 is a F atom.

3. The battery cell according to claim 1, wherein: The fluoroether solvent satisfies any one of the following conditions (1) to (6), (1) X is a monofluoromethylene group or a difluoromethylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is a hydrogen atom, a fluorine atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group; (2) X is a monofluoromethylene group or a difluoromethylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is a hydrogen atom, a fluorine atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; (3) X is a monofluoromethylene or difluoromethylene group, Y is a monofluoromethylene or difluoromethylene group, and R3 is a F atom; (4) X is a monofluoromethylene group or a difluoromethylene group, Y is a methylene group, and R3 is a hydrogen atom, a fluorine atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group; (5) X is a monofluoromethylene group or a difluoromethylene group, Y is a methylene group, and R3 is a hydrogen atom, a fluorine atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; (6) X is a monofluoromethylene or difluoromethylene, Y is a methylene, and R3 is a F atom.

4. The battery cell according to claim 1, wherein: The fluoroether solvent satisfies any one of the following conditions (1) to (3), (1) X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is a hydrogen atom, a fluorine atom, a C1-C5 alkyl group, or a C1-C5 fluoroalkyl group; (2) X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is a hydrogen atom, a fluorine atom, a methyl group, a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; (3) X is a methylene group, Y is a monofluoromethylene group or a difluoromethylene group, and R3 is a F atom.

5. The battery cell according to claim 1, characterized in that X is a methylene group, Y is a methylene group, and R3 is a F atom.

6. The battery cell according to claim 1, characterized in that R1 is a C1-C3 alkyl group, and / or R2 is a C1-C3 alkylene group.

7. The battery cell according to claim 6, characterized in that R1 is a methyl group, and / or R2 is a methylene group.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The fluoroether solvent includes one or more of the following, 9. The battery cell according to claim 8, characterized in that The fluoroether solvent includes one or more of A-1 to A-3, A-6 to A-10, A-14 to A-16, and A-20 to A-26.

10. The battery cell according to claim 9, characterized in that The fluoroether solvent includes one or more of A-2 and A-3.

11. The battery cell according to any one of claims 1 to 10, characterized in that: The mass proportion of the fluoroether solvent in the solvent is greater than or equal to 30% and less than 100%.

12. The battery cell according to claim 11, characterized in that The mass percentage of the fluoroether solvent in the solvent is greater than 50% and less than or equal to 80%.

13. The battery cell according to any one of claims 1 to 10, characterized in that: The mass percentage of the fluoroether solvent in the solvent is 100%.

14. The battery cell according to any one of claims 1 to 12, characterized in that: The solvent also includes an inert solvent, which includes benzene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-dimethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(difluoromethoxy)ethane, 1,2-bis(trifluoromethoxy)ethane, 1,2-diethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl)ether, bis(2,2-difluoroethyl) ) ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, bis(1,1,2,2-tetrafluoroethyl) ether.

15. The battery cell according to claim 14, characterized in that The mass proportion of the inert solvent in the solvent is greater than 0 and less than or equal to 70%.

16. The battery cell according to claim 15, characterized in that The mass proportion of the inert solvent in the solvent is 20%-50%.

17. The battery cell according to any one of claims 1 to 16, characterized in that: The electrolyte includes an electrolyte salt, and the electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorobis(oxalatophosphate), and lithium tetrafluorooxalatophosphate.

18. The battery cell according to claim 17, characterized in that The concentration of the electrolyte salt in the electrolyte solution is 0.5 mol / L-4 mol / L.

19. The battery cell according to any one of claims 1 to 18, characterized in that: The battery cell includes one of a lithium metal battery cell and a negative electrode-free lithium metal battery cell.

20. A battery, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 19.

21. An electrical device, characterized in that: Comprising the battery of claim 20.

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