Battery cell and preparation method therefor, battery device and electric device

Abstract

A battery cell and a preparation method therefor, a battery device and an electric device. The battery cell comprises an electrode assembly and an electrolyte solution, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, with the separator being located between the positive electrode sheet and the negative electrode sheet; and the electrolyte solution comprises an organic solvent, an electrolyte salt and a phosphate compound having an unsaturated bond. The battery cell has a long cycle life, a long storage life and a low impedance.

Description

Battery cells and their preparation methods, battery devices and electrical devices

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510188949.7, filed on February 20, 2025, entitled “Battery cell and method of preparation thereof, battery device and power consumption device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a battery cell and its preparation method, a battery device, and an electrical device. Background Technology

[0004] Long cycle life and long storage life are common goals for battery cells. However, during the use of a battery cell, side reactions usually occur continuously at the electrode and electrolyte interface, which affects the cycle life and storage life of the battery cell. Summary of the Invention

[0005] This disclosure provides a battery cell and its preparation method, a battery device, and an electrical device. The battery cell has the advantages of long cycle life, long storage life, and low impedance.

[0006] In a first aspect, this disclosure provides a battery cell, including an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode.

[0007] The electrolyte comprises an organic solvent, an electrolyte salt, and a phosphate ester compound with unsaturated bonds, including compounds represented by Formula I.

[0008] R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, C2-C6 alkenyl or haloalkenyl, C2-C6 ynyl or haloynyl, C1-C6 alkyl or haloalkyl, R a R b Each of the following groups is independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkyne or haloalkyne, Me is an alkali metal, and at least one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe.

[0009] The electrolyte disclosed herein uses a phosphate ester compound with unsaturated bonds, which can form a dense, stable and low-impedance interfacial film in situ on the negative electrode surface. This can reduce side reactions at the negative electrode-electrolyte interface, reduce irreversible capacity loss and electrolyte loss during the use of the battery cell, improve the initial coulombic efficiency, cycle life and storage life of the battery cell, and enable the battery cell to have low impedance and good kinetic performance during use.

[0010] In some embodiments, R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, C3-C4 alkenyl or haloalkenyl, C3-C4 ynyl or haloalkynyl, R a R b Each is independently selected from C3-C4 alkenyl or haloalkenyl, C3-C4 alynyl or haloalynyl.

[0011] In some embodiments, R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, allyl, haloallyl, propargyl, halopropargyl, R a R b Each is independently selected from allylene, haloallylene, propynylene, and halopropynylene.

[0012] In some embodiments, Me is Li.

[0013] In some embodiments, the phosphate ester compound having unsaturated bonds includes at least one of the following compounds and its halogenated derivatives:

[0014] In some embodiments, based on the total mass of the electrolyte, the mass content of the phosphate ester compound with unsaturated bonds is greater than 0 and less than 2 wt%, optionally greater than 0 and less than 1 wt%. This facilitates the formation of a high-performance interface film on the negative electrode surface during charging and discharging, thereby contributing to a battery cell that combines long cycle life, long storage life, and low impedance.

[0015] In some embodiments, the electrolyte further includes film-forming additives, including one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate. These film-forming additives help form a high-performance interfacial film on the negative electrode surface, thereby contributing to long cycle life, long storage life, and low impedance in the battery cell.

[0016] In some embodiments, the mass content of the film-forming additive is greater than 0 and less than 8 wt% based on the total mass of the electrolyte.

[0017] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorophosphate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0018] In some embodiments, the organic solvent includes one or more of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

[0019] In a second aspect, this disclosure provides a battery device comprising a plurality of battery cells as described in the first aspect.

[0020] Thirdly, this disclosure provides an electrical device that includes a battery cell as described in the first aspect or a battery device as described in the second aspect.

[0021] Fourthly, this disclosure provides a method for preparing a single battery cell, comprising the following steps:

[0022] An electrode assembly is provided, which includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode.

[0023] An electrolyte is obtained by stirring and mixing an organic solvent, an electrolyte salt, and a phosphate ester compound with unsaturated bonds until homogeneous. The phosphate ester compound with unsaturated bonds includes the compound shown in Formula I, where R1, R2, and R3 are independently selected from -R a -OMe、-R b -COOMe, C2-C6 alkenyl or haloalkenyl, C2-C6 ynyl or haloynyl, C1-C6 alkyl or haloalkyl, R a R b Each of the following groups is independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkyne or haloalkyne, Me is an alkali metal, and at least one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe,

[0024] The electrode assembly is placed in an outer package with a receiving cavity, the electrolyte is injected into the receiving cavity, and after encapsulation and formation, a battery cell is obtained.

[0025] In some embodiments, the amount of phosphate ester compound with unsaturated bonds added is 0.1 wt% to 2 wt% based on the total mass of the electrolyte.

[0026] In some embodiments, the electrolyte also contains film-forming additives, including one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

[0027] In some embodiments, the amount of film-forming additive added is 0.1 wt% to 8 wt% based on the total mass of the electrolyte. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0029] Figure 1 shows a schematic diagram of a battery cell provided in some embodiments of this disclosure.

[0030] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this disclosure.

[0031] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0032] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, its preparation method, battery device, and power-consuming device of this disclosure. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0033] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this disclosure may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this disclosure.

[0035] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0036] Unless otherwise specified, all steps in this disclosure 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0038] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0039] In the description of the embodiments of this disclosure, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0040] In this disclosure, the term "alkyl" refers to a saturated hydrocarbon group, including both straight-chain and branched structures. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, and n-hexyl. C1-C6 alkyl groups, i.e., alkyl groups, may contain 1 to 6 carbon atoms.

[0041] In this disclosure, the term "alkenyl" includes both straight-chain and branched structures. The number of carbon-carbon double bonds in an alkenyl group can be one or more, and C2-C6 alkenyl groups, i.e., alkenyl groups, can contain 2 to 6 carbon atoms.

[0042] In this disclosure, the term "alkynyl" includes both straight-chain and branched structures. The number of carbon-carbon triple bonds in an alkynyl group can be one or more, and a C2-C6 alkynyl group can contain 2 to 6 carbon atoms.

[0043] In this disclosure, "sub" indicates that the group is an organic divalent functional group, that is, the group remaining after the corresponding organic compound loses two hydrogen atoms.

[0044] In this disclosure, a "halogenated" group of a group (e.g., alkyl, alkenyl, alkynyl, alkenylyl, alkynyl, etc.) refers to a group obtained by replacing at least one hydrogen atom of the group (e.g., alkyl, alkenyl, alkynyl, etc.) with a halogen atom. The number of halogen atoms in the halogenated group can be one or more; when multiple halogen atoms are present in the halogenated group, the multiple halogen atoms can be the same or different.

[0045] In this disclosure, a halogen atom refers to a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. Optionally, a halogen atom may be a fluorine atom.

[0046] Throughout this specification, substituents of compounds are disclosed by groups or ranges. It is expressly intended that such description include each individual sub-combination of members of these groups and ranges. For example, it is expressly intended that the term "C1-C6 alkyl" individually discloses alkyl groups of C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5, and C5-C6.

[0047] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0048] The battery cells mentioned in the embodiments of this disclosure are capable of charging and discharging independently. The battery cells may be cylindrical, cuboid, or other shapes, and this disclosure does not limit this. Figure 1 shows a cuboid battery cell 5 as an example.

[0049] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0050] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0051] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0052] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0053] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be housed in the housing by fixing the battery module in the housing.

[0054] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0055] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0056] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0057] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0058] The technical solutions described in this disclosure are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., 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. Battery cells and battery devices are used to store or provide electrical energy.

[0059] Figure 2 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0060] The battery cells provided in the embodiments of this disclosure can be lithium-ion battery cells, lithium metal battery cells, or negative electrode-free lithium metal batteries, etc. Negative electrode-free lithium metal battery cells typically refer to battery cells in which a negative electrode active material layer is not actively formed on the negative electrode side during the battery cell manufacturing process. For example, during the battery cell manufacturing process, a negative electrode active material layer formed from carbonaceous materials is not formed at the negative electrode through processes such as coating or deposition. 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 lithium metal. During discharge, the lithium metal can be converted into lithium ions and return to the positive electrode, achieving cyclic charging and discharging. Compared to other battery cells, negative electrode-free lithium metal battery cells can achieve higher energy density because they lack a negative electrode active material layer.

[0061] The electrolyte acts as a conductor of ions between the positive and negative electrodes, and the electrode-electrolyte interface characteristics significantly influence the electrochemical performance of a single battery cell. During the initial charging process, the electrolyte undergoes a reduction reaction at the negative electrode, forming a solid electrolyte interphase (SEI) film on its surface. A high-performance SEI film helps reduce side reactions at the negative electrode-electrolyte interface, minimizing irreversible capacity and electrolyte loss during battery cell use, thus significantly impacting the cycle life and storage life of the battery cell. This is particularly important for energy storage batteries, which typically require longer cycle and storage life. However, during battery cell use, side reactions usually continue to occur at the negative electrode and electrolyte interface, affecting the cycle and storage life of the battery cell.

[0062] Existing technologies typically adjust the composition of the interfacial film by introducing additives into the electrolyte. However, existing additives often result in poor interfacial film quality or high impedance after film formation.

[0063] Based on this, the present disclosure provides a battery cell and a battery device and an electrical device containing the same, wherein by adjusting the composition of the electrolyte, the battery cell can have a long cycle life, a long storage life and low impedance.

[0064] The battery cell provided in this embodiment includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode.

[0065] The battery cell also includes an outer packaging for housing the electrode assembly and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The flexible package can be made of plastic, such as aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0066] Electrolytes include organic solvents, electrolyte salts, and phosphate ester compounds with unsaturated bonds.

[0067] Phosphate ester compounds with unsaturated bonds include those shown in Formula I.

[0068] R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, C2-C6 alkenyl or haloalkenyl, C2-C6 ynyl or haloynyl, C1-C6 alkyl or haloalkyl, R a R bEach of the following groups is independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkyne or haloalkyne, Me is an alkali metal, and at least one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe.

[0069] The electrolyte disclosed herein comprises a phosphate ester compound having unsaturated bonds. The molecular structure of the phosphate ester compound having unsaturated carbon-carbon double bonds and / or carbon-carbon triple bonds makes it easy for it to gain electrons at the negative electrode to form free radical molecules and undergo polymerization reactions. This allows a dense interfacial film to be formed in situ on the negative electrode surface, thereby reducing side reactions at the negative electrode-electrolyte interface and reducing irreversible capacity loss and electrolyte loss during the use of the battery cell.

[0070] Phosphate ester compounds with unsaturated bonds also introduce -OMe and / or -COOMe into their molecular structure. The presence of these groups helps to improve the ionic conductivity of the negative electrode interface film and facilitates the introduction of inorganic components, such as phosphates, into the negative electrode interface film, thereby enabling the negative electrode interface film to have lower impedance and higher thermal stability.

[0071] Therefore, the phosphate ester compound with unsaturated bonds used in the electrolyte of this disclosure can form a dense, stable and low-impedance interfacial film in situ on the negative electrode surface. This can reduce the side reactions at the negative electrode-electrolyte interface, reduce irreversible capacity loss and electrolyte loss during the use of the battery cell, improve the initial coulombic efficiency, cycle life and storage life of the battery cell, and enable the battery cell to have low impedance and good kinetic performance during use.

[0072] In some embodiments, R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, C2-C6 alkenyl or haloalkenyl, C2-C6 ynyl or haloalkynyl, R a R b Each of the following groups is independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkyne or haloalkyne, Me is an alkali metal, and at least one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe.

[0073] In some embodiments, R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, C3-C4 alkenyl or haloalkenyl, C3-C4 ynyl or haloalkynyl, R a R bEach of the following groups is independently selected from C3-C4 alkenyl or haloalkenyl, C3-C4 alkyne or haloalkyne, Me is an alkali metal, and at least one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe.

[0074] In some embodiments, R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, allyl, haloallyl, propargyl, halopropargyl, R a R b Each is independently selected from allylene, haloallylene, propynylene, and halopropynylene.

[0075] In some embodiments, one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe, the other two are independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkynyl or haloalkynyl, C1-C6 alkyl or haloalkyl.

[0076] Optionally, one of R1, R2, and R3 can be selected from -R a -OMe、-R b -COOMe, the other two are independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkynyl or haloalkynyl.

[0077] Alternatively, one of R1, R2, and R3 may be selected from -R a -OMe、-R b -COOMe, the other two are independently selected from C3-C4 alkenyl or haloalkenyl, C3-C4 alkynyl or haloalkynyl.

[0078] In some embodiments, two of R1, R2, and R3 are independently selected from -R a -OMe、-R b -COOMe, the other one is selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkynyl or haloalkynyl, C1-C6 alkyl or haloalkyl.

[0079] Optionally, two of R1, R2, and R3 may be independently selected from -R a -OMe、-R b -COOMe, the other one is selected from an alkenyl or haloalkenyl group from C2-C6, or an alkynyl or haloalkynyl group from C2-C6.

[0080] Alternatively, two of R1, R2, and R3 may be independently selected from -R a-OMe、-R b -COOMe, the other one is selected from C3-C4 alkenyl or haloalkenyl, C3-C4 alkynyl or haloalkynyl.

[0081] In some embodiments, the haloalkenyl group may be a fluoroalkenyl group.

[0082] In some embodiments, the halogenated alkynyl group may be a fluoroalkynyl group.

[0083] In some embodiments, the haloalkyl group may be a fluoroalkyl group.

[0084] In some embodiments, the haloidene group may be a fluoroidene group.

[0085] In some embodiments, the haloynyl group can be a fluoroynyl group.

[0086] In some embodiments, R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe.

[0087] Me is an alkali metal. In some embodiments, Me can be Li, Na, or K. Optionally, Me can be Li or Na. More preferably, Me can be Li.

[0088] In some embodiments, the phosphate ester compound having unsaturated bonds may include at least one of the following compounds and halogenated derivatives of the following compounds:

[0089] Alternatively, the halogenated product can be a fluorinated product.

[0090] In some embodiments, based on the total mass of the electrolyte, the mass content of the phosphate ester compound having unsaturated bonds can be greater than 0 and less than 2 wt%, for example, it can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or any range of the above values.

[0091] The electrolyte contains an appropriate amount of phosphate ester compounds with unsaturated bonds, which is beneficial for the in-situ formation of a uniform interfacial film on the negative electrode surface during charging and discharging. This helps reduce side reactions at the negative electrode-electrolyte interface, minimizing irreversible capacity loss and electrolyte loss. It also facilitates the formation of a dense, stable, and low-resistance interfacial film on the negative electrode surface. In other words, it reduces the risk of excessive negative electrode interfacial impedance and excessive internal resistance of the battery cell caused by a high content of phosphate ester compounds with unsaturated bonds. Therefore, by ensuring that the mass content of phosphate ester compounds with unsaturated bonds in the electrolyte of the battery cell is within the above-mentioned range, it is beneficial for forming a high-performance interfacial film on the negative electrode surface during charging and discharging, thus contributing to a battery cell that combines long cycle life, long storage life, and low impedance.

[0092] Optionally, based on the total mass of the electrolyte, the mass content of the phosphate ester compound with unsaturated bonds can be greater than 0 and less than 1 wt%.

[0093] This helps individual battery cells to better combine long cycle life, long storage life, and low impedance.

[0094] The mass content of the phosphate ester compounds with unsaturated bonds mentioned above refers to the mass content of phosphate ester compounds with unsaturated bonds obtained by testing the free electrolyte after disassembling the battery cell.

[0095] The mass content of unsaturated phosphate ester compounds in the electrolyte of a battery cell can be obtained by the following method: After disassembling the battery cell, take a sample of the free electrolyte in the residual space. Separate the components such as organic solvents and unsaturated phosphate ester compounds from the electrolyte salt components by gas chromatography. Then, the specific structure of each component can be confirmed by high-precision mass spectrometry and nuclear magnetic resonance spectroscopy. Finally, the content of each component is quantitatively analyzed by ion chromatography.

[0096] In the above tests, a battery cell refers to a fresh battery cell, such as a factory-issued battery cell (e.g., one that has not been charged and discharged after formation) or a battery cell that has been assembled on an electrical device and has less than 10 cycles.

[0097] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0098] Optionally, the electrolyte salt may include one or both of lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI).

[0099] In some embodiments, the organic solvent may include one or more of cyclic carbonate solvents, chain carbonate solvents, carboxylic acid ester solvents, ether solvents, nitrile solvents, and sulfone solvents.

[0100] As an example, the organic solvent may include, but is not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

[0101] In some embodiments, the concentration of the electrolyte salt can be between 0.6 mol / L and 4 mol / L, for example, it can be 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.4 mol / L, 3.6 mol / L, 3.8 mol / L, 4 mol / L, or any range of the above values. Those skilled in the art can adjust the concentration of the electrolyte salt according to the type of battery cell.

[0102] In some embodiments, the electrolyte may also include film-forming additives.

[0103] Optionally, the film-forming additive may include one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propanesulfonate lactone (PS), and vinyl sulfate (DTD).

[0104] These film-forming additives help form a high-performance interface film on the negative electrode surface, which in turn helps the battery cell to have both long cycle life, long storage life and low impedance.

[0105] In some embodiments, based on the total mass of the electrolyte, the mass content of the film-forming additive can be greater than 0 and less than 8 wt%, for example, it can be 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 7.8 wt%, or any range of the above values.

[0106] The mass content of the aforementioned film-forming additives refers to the mass content of the film-forming additives obtained by testing the free electrolyte after disassembling the battery cell.

[0107] The electrode assembly can be a wound structure or a stacked structure, and the embodiments disclosed herein are not limited to this.

[0108] The number of electrode components contained in a single battery cell can be one or more, and this disclosure does not limit this.

[0109] The electrode assembly includes a positive electrode, a negative electrode, and a separator, which will be described in detail below.

[0110] [Positive electrode plate]

[0111] In some embodiments, the positive electrode sheet may include a positive current collector and a positive active material layer located on at least one surface of the positive current collector, the positive active material layer comprising a positive active material. The positive current collector has two surfaces opposite each other in its thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0112] In some embodiments, the positive electrode active material may include one or more of lithium transition metal oxides and their modified forms, lithium phosphates and their modified forms.

[0113] Optionally, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and lithium-rich manganese-based materials.

[0114] Optionally, examples of lithium phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0115] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e A f One or more of lithium transition metal oxides and their modified materials. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A may include one or more of N, F, S and Cl.

[0116] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and 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 0.83 Mn 0.08 Co 0.07 O2 (abbreviated as Ni83), LiNi 0.90 Mn 0.05 Co 0.05 O2 (abbreviated as Ni90), LiNi 0.94 Mn 0.03 Co 0.03 O2 (abbreviated as Ni94), 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 materials.

[0117] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single battery cell, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar Li content represents the initial state of the material, i.e., the state before material addition. As the positive electrode active material is applied to the battery cell, the molar Li content changes after charge-discharge cycles. Similarly, the molar O content in the examples of positive electrode active materials in this disclosure is only a theoretical value. Oxygen release from the crystal lattice causes changes in the molar O content, leading to fluctuations in the actual molar O content.

[0118] The modified materials for the above-mentioned positive electrode active materials can be doped and / or surface coated.

[0119] In some embodiments, the positive electrode active material layer may further include a positive electrode binder, which may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0120] In some embodiments, the positive electrode active material layer may further include a positive electrode conductive agent, which may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0121] In some embodiments, the positive current collector can be a metal foil or a composite current collector. The metal foil can be a pure metal, an alloy, or a surface-treated metal. For example, the metal foil can be carbon-coated aluminum foil, aluminum foil, nickel foil, or titanium foil. The composite current collector can include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. For example, the metal material can be one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer substrate can be one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0122] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, positive electrode conductive agent, positive electrode binder, and any other components in a solvent and mixing them thoroughly. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0123] [Negative electrode plate]

[0124] In some embodiments, the negative electrode sheet may include a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer comprising a negative active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative active material layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0125] The negative electrode active material may be any material known in the art that can be used in battery cells. As an example, the negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include, but are not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include, but are not limited to, one or more of elemental tin, tin oxide, and tin alloys.

[0126] In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent. As an example, the negative 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.

[0127] In some embodiments, the negative electrode active material layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0128] In some embodiments, the negative electrode active material layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0129] The negative electrode active material layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and mixing them thoroughly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0130] In some embodiments, the negative electrode may include a negative current collector and a lithium metal layer disposed on at least one surface of the negative current collector. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the lithium metal layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0131] In some embodiments, the negative electrode may be a negative current collector.

[0132] In some embodiments, the negative electrode sheet may include a negative current collector and a lithiophilic layer disposed on at least one surface of the negative current collector. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the lithiophilic layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0133] Optionally, the lithiophilic layer may include one or more of a lithiophilic metal element, a lithiophilic metal alloy, and a lithiophilic oxide.

[0134] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. The metal foil may be a pure metal, an alloy, or a surface-treated metal. For example, the metal foil may be copper foil. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. For example, the metal material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0135] In some embodiments, the negative electrode sheet can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0136] [Isolation membrane]

[0137] The separator is located between the positive and negative electrodes and primarily serves to prevent internal short circuits. This disclosure does not impose any particular limitation on the type of separator; any known porous membrane with good chemical and mechanical stability can be selected.

[0138] In some embodiments, the material of the separator may include, but is not limited to, one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and polyimide. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0139] Alternatively, an inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating may be applied to the surface of the separator.

[0140] This disclosure also provides a method for preparing a battery cell, which can prepare the battery cell provided in this disclosure.

[0141] The preparation method of a single battery cell includes the following steps:

[0142] An electrode assembly is provided, which includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode.

[0143] An electrolyte is obtained by stirring and mixing an organic solvent, an electrolyte salt, and a phosphate ester compound with unsaturated bonds until homogeneous. The phosphate ester compound with unsaturated bonds includes the compound shown in Formula I, where R1, R2, and R3 are independently selected from -R a -OMe、-R b -COOMe, C2-C6 alkenyl or haloalkenyl, C2-C6 ynyl or haloynyl, C1-C6 alkyl or haloalkyl, R a R b Each of the following groups is independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkyne or haloalkyne, Me is an alkali metal, and at least one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe,

[0144] The electrode assembly is placed in an outer package with a receiving cavity, the electrolyte is injected into the receiving cavity, and after encapsulation and formation, a battery cell is obtained.

[0145] Before leaving the factory, battery cells need to undergo formation treatment. During this process, unsaturated phosphate ester compounds in the electrolyte typically form a film on the negative electrode surface. This can result in a lower mass content of unsaturated phosphate ester compounds in the electrolyte obtained from the residual space within the battery cell compared to the mass content of unsaturated phosphate ester compounds in the prepared electrolyte. Therefore, the mass content of unsaturated phosphate ester compounds can be adjusted during electrolyte preparation according to specific conditions.

[0146] In some embodiments, the amount of phosphate ester compound with unsaturated bonds added may be 0.1 wt% to 2 wt% based on the total mass of the electrolyte.

[0147] Optionally, based on the total mass of the electrolyte, the amount of phosphate ester compound with unsaturated bonds added can be 0.5wt%-1wt%.

[0148] The amount of phosphate ester compound with unsaturated bonds added mentioned above refers to the mass content of the phosphate ester compound with unsaturated bonds added in the electrolyte during the preparation of the electrolyte.

[0149] In some embodiments, the electrolyte also contains film-forming additives, including one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

[0150] Optionally, the amount of film-forming additive added can be 0.1wt%-8wt% based on the total mass of the electrolyte.

[0151] The amount of film-forming additives mentioned above refers to the mass content of the film-forming additives added during the preparation of the electrolyte in the electrolyte.

[0152] Example

[0153] The following embodiments describe the disclosure of this disclosure in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0154] This disclosure provides, by way of example, two methods for preparing phosphate ester compounds having unsaturated bonds. Other phosphate ester compounds having unsaturated bonds can be prepared by reference to these exemplary methods. Based on these exemplary preparation methods, those skilled in the art can readily obtain specific methods for implementing each synthetic step from relevant scientific literature or standard textbooks in the art. Unless specifically indicated, commercially available or literature-known compounds are used herein as starting materials for synthesis. Those skilled in organic synthesis will recognize that the nature and sequence of the proposed synthetic steps can be modified for the purpose of optimizing the formation of the compounds described in this disclosure. The processes described in the embodiments of this disclosure can be monitored according to any suitable method known in the art. For example, product formation can be achieved by spectroscopic means such as nuclear magnetic resonance spectroscopy (NMR, e.g.) 1 H, 13 C or 19 F) Infrared spectroscopy (IR), mass spectrometry (MS), and X-ray photoelectron spectroscopy (XPS) are used for monitoring.

[0155] Tripropyne phosphate (CAS: 1779-34-6) was halogenated with halomethane to obtain a methylated product, which was then halogenated to obtain a halomethylated product. After hydrolysis and oxidation, a formic acid product was obtained, which was then reacted with methyllithium to obtain a phosphate ester compound with unsaturated bonds as shown below.

[0156] Propryne phosphate (CAS: 1779-34-6) was reacted with formic acid at 100 °C, then cooled to room temperature in an ice-water bath and a catalyst was added. The product was then reacted with methyllithium, followed by halogenation of the product with Cl2. Finally, the product was subjected to an elimination reaction catalyzed by an alkali metal hydroxide to obtain the phosphate compound with unsaturated bonds shown below.

[0157] Example 1

[0158] Preparation of electrolyte

[0159] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. Then, LiFSI, vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate lactone (PS), and the unsaturated phosphate compounds shown in Table 1 were added, and the mixture was stirred until homogeneous to obtain the electrolyte. The concentration of LiFSI was 1 mol / L, the amount of VC added was 5 wt%, the amount of DTD added was 1 wt%, the amount of PS added was 1 wt%, and the amount of the unsaturated phosphate compounds added was 0.5 wt%, all calculated based on the total mass of the electrolyte.

[0160] Preparation of positive electrode sheet

[0161] Lithium iron phosphate (specific capacity 139 mAh / g), acetylene black, and polyvinylidene fluoride (PVDF) were mixed at a solid mass ratio of 94:4:2. N-methylpyrrolidone was added as a solvent, and the mixture was thoroughly stirred to obtain a homogeneous positive electrode slurry. This slurry was then coated onto both surfaces of the positive electrode current collector aluminum foil. The coating weight of the positive electrode slurry was 0.250 g / 1540.25 mm. 2 (Based on weight excluding solvent), then dried and cold-pressed to obtain the positive electrode sheet.

[0162] Preparation of negative electrode sheet

[0163] Artificial graphite (specific capacity 340 mAh / g), acetylene black (negative electrode conductive agent), styrene-butadiene rubber (SBR) (negative electrode binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed in a solid mass ratio of 95:1.5:3.1:0.4. Deionized water was added as a solvent, and the mixture was stirred thoroughly to obtain a uniform negative electrode slurry. This slurry was then coated onto both surfaces of the copper foil used as the negative electrode current collector. The coating weight of the negative electrode slurry was 0.112 g / 1540.25 mm. 2 (Based on weight excluding solvent), then dried and cold-pressed to obtain the negative electrode sheet.

[0164] Separating membrane

[0165] Polyethylene porous membrane is used as the separation membrane.

[0166] Preparation of battery cells

[0167] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound up to form an electrode assembly. The electrode assembly is placed in an outer packaging with a receiving cavity, and the prepared electrolyte is injected into the receiving cavity. The assembly is then sealed and formed to obtain a lithium-ion battery cell.

[0168] Examples 2 to 7

[0169] Except for using the phosphate ester compounds with unsaturated bonds shown in Table 1, the preparation method of the battery cells is the same as in Example 1.

[0170] Comparative Example 1

[0171] Except for the following differences, the preparation method of the battery cell is the same as that in Example 1.

[0172] Preparation of electrolyte

[0173] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. LiFSI, ethylene carbonate (VC), ethylene sulfate (DTD), and 1,3-propanesulfonate lactone (PS) were then added, and the mixture was stirred until homogeneous to obtain the electrolyte. The concentration of LiFSI was 1 mol / L, the amount of VC added was 5 wt%, the amount of DTD added was 1 wt%, and the amount of PS added was 1 wt%, all calculated based on the total mass of the electrolyte.

[0174] Comparative Example 2

[0175] Except for the following differences, the preparation method of the battery cell is the same as that in Example 1.

[0176] Preparation of electrolyte

[0177] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. Then, LiFSI, ethylene carbonate (VC), ethylene sulfate (DTD), 1,3-propanesulfonyl lactone (PS), and propargyl phosphate were added, and the mixture was stirred until homogeneous to obtain the electrolyte. The concentration of LiFSI was 1 mol / L, the amount of VC added was 5 wt%, the amount of DTD added was 1 wt%, the amount of PS added was 1 wt%, and the amount of propargyl phosphate added was 0.5 wt%, all calculated based on the total mass of the electrolyte.

[0178] Comparative Example 3

[0179] Except for the following differences, the preparation method of the battery cell is the same as that in Example 1.

[0180] Preparation of electrolyte

[0181] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. Then, LiFSI, ethylene carbonate (VC), ethylene sulfate (DTD), 1,3-propanesulfonate lactone (PS), and triallyl phosphate were added, and the mixture was stirred until homogeneous to obtain the electrolyte. The concentration of LiFSI was 1 mol / L, the amount of VC added was 5 wt%, the amount of DTD added was 1 wt%, the amount of PS added was 1 wt%, and the amount of triallyl phosphate added was 0.5 wt%, all calculated based on the total mass of the electrolyte.

[0182] Comparative Example 4

[0183] Except for the following differences, the preparation method of the battery cell is the same as that in Example 1.

[0184] Synthesis of phosphate ester compounds with unsaturated bonds

[0185] Lithium diethyl phosphate, propargyl acetate, N,N-dimethylformamide, and tetramethylurea were added to a dry, eggplant-shaped flask equipped with a distillation apparatus and a stirring device. Under stirring, the reaction temperature was controlled at 105°C, and the temperature of the distillation tube was controlled at 80°C. The reaction was carried out at a constant temperature for 9 hours. After the reaction was completed, the solid was evaporated to dryness, and the solid was pulped with dimethyl sulfoxide, filtered, washed with dichloromethane, and evaporated to dryness to obtain lithium diethyl propargyl phosphate.

[0186] Preparation of electrolyte

[0187] In an argon-atmosphere glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. Then, LiFSI, ethylene carbonate (VC), ethylene sulfate (DTD), 1,3-propanesulfonyl lactone (PS), and lithium diacetyl phosphate were added, and the mixture was stirred until homogeneous to obtain the electrolyte. The concentration of LiFSI was 1 mol / L, the addition amount of VC was 5 wt%, the addition amount of DTD was 1 wt%, the addition amount of PS was 1 wt%, and the addition amount of lithium diacetyl phosphate was 0.5 wt%, all calculated based on the total mass of the electrolyte.

[0188] Comparative Example 5

[0189] Except for the following differences, the preparation method of the battery cell is the same as that in Example 1.

[0190] Synthesis of phosphate ester compounds with unsaturated bonds

[0191] Lithium diallyl phosphate, allyl acetate, N,N-diethylformamide, and 1,3-dimethylurea were added to a dry, round-bottomed flask equipped with a distillation apparatus and a stirring device. Under stirring, the reaction temperature was controlled at 90°C, and the temperature of the distillation tube was controlled at 60°C. The reaction was carried out at a constant temperature for 8 hours. After the reaction was completed, the solid was evaporated to dryness, and the solid was slurried with dimethyl sulfoxide, filtered, washed with dichloromethane, and evaporated to dryness to obtain lithium diallyl phosphate.

[0192] Preparation of electrolyte

[0193] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. Then, LiFSI, ethylene carbonate (VC), ethylene sulfate (DTD), 1,3-propanesulfonate lactone (PS), and diallyl phosphate lithium salt were added, and the mixture was stirred until homogeneous to obtain the electrolyte. The concentration of LiFSI was 1 mol / L, the addition amount of VC was 5 wt%, the addition amount of DTD was 1 wt%, the addition amount of PS was 1 wt%, and the addition amount of diallyl phosphate lithium salt was 0.5 wt%, all calculated based on the total mass of the electrolyte.

[0194] Performance testing

[0195] (1) Cyclic performance test

[0196] The battery cell was placed in a 60℃ constant temperature chamber and charged at a constant current of 1C to 3.65V. Then, it was charged at a constant voltage until the current reached 0.05C. At this point, the battery cell was fully charged, and the charging capacity was recorded; this is the first charge capacity. After allowing the battery cell to rest for 5 minutes, it was discharged at a constant current of 1C to 2.5V. This completes one charge-discharge cycle, and the discharge capacity was recorded; this is the first discharge capacity. The battery cells were subjected to cyclic charge-discharge tests using the above method. The capacity retention rate of the battery cell after 500 cycles at 60℃ = (500-cycle discharge capacity / first-cycle discharge capacity) * 100%.

[0197] (2) Storage performance test

[0198] At 25℃, the battery cell is charged at a constant current of 1C to 3.65V, and then charged at a constant voltage until the current reaches 0.05C. After the battery cell is left to stand for 5 minutes, it is discharged at a constant current of 1C to 2.5V, and the discharge capacity at this point is recorded; this is the capacity before storage. Then, the battery cell is charged at a constant current of 1C to 3.65V, and then charged at a constant voltage until the current reaches 0.05C; at this point, the battery cell is at 100% SOC. The 100% SOC battery cell is then placed in a 60℃ constant temperature chamber and stored for 90 days. After the battery cell is removed and its temperature drops to 25℃, it is discharged at a constant current of 1C to 2.5V, and the discharge capacity at this point is recorded; this is the capacity after storage. The capacity retention rate of the battery cell after 90 days of storage at 60℃ = (Capacity after storage / Capacity before storage) * 100%.

[0199] (3) Initial DCR test

[0200] At 25℃, the battery cell is charged at a constant current of 0.5C to 3.65V, and then charged at a constant voltage until the current reaches 0.05C. The battery cell is then discharged at a constant current of 0.5C for 60 minutes to adjust the battery cell to 50% SOC. The voltage of the battery cell at this point is recorded as U1. The battery cell is then discharged at a constant current of 4C I for 30 seconds, with a sampling time of 0.1 seconds. The voltage at the end of the discharge is recorded as U2. The initial DCR of the battery cell is represented by the discharge DCR at 50% SOC. The initial DCR of the battery cell is calculated as (U1 - U2) / I.

[0201] Table 1

[0202] The test results of Comparative Examples 1 to 5 show that adding lithium triargyl phosphate, lithium triallyl phosphate, lithium diallyl phosphate, or lithium diallyl phosphate to the electrolyte can improve the high-temperature cycle capacity retention rate and high-temperature storage capacity retention rate of the battery cells, but the initial DCR of the battery cells increases significantly.

[0203] As can be seen from the test results of Examples 1 to 7, by adding the phosphate ester compound with unsaturated bonds disclosed herein to the electrolyte, both the high-temperature cycle capacity retention rate and high-temperature storage capacity retention rate of the battery cell can be improved, and the battery cell can also have a lower initial DCR. This is because the phosphate ester compound with unsaturated bonds used in the electrolyte of this disclosure can form a dense, stable and low-resistance interface film in situ on the negative electrode surface.

[0204] Example 2-1

[0205] Except for the following differences, the preparation method of the battery cell is the same as that in Example 2.

[0206] Preparation of electrolyte

[0207] The amount of phosphate ester compound with unsaturated bonds added was 0.8 wt%, calculated based on the total mass of the electrolyte.

[0208] Example 2-2

[0209] Except for the following differences, the preparation method of the battery cell is the same as that in Example 2.

[0210] Preparation of electrolyte

[0211] The amount of phosphate ester compound with unsaturated bonds added is 1 wt%, calculated based on the total mass of the electrolyte.

[0212] Example 2-3

[0213] Except for the following differences, the preparation method of the battery cell is the same as that in Example 2.

[0214] Preparation of electrolyte

[0215] The amount of phosphate ester compound with unsaturated bonds added is 2 wt%, calculated based on the total mass of the electrolyte.

[0216] Examples 2-4

[0217] Except for the following differences, the preparation method of the battery cell is the same as that in Example 2.

[0218] Preparation of electrolyte

[0219] The amount of phosphate ester compound with unsaturated bonds added is 0.1 wt%, calculated based on the total mass of the electrolyte.

[0220] Table 2

[0221] The test results above show that further adjusting the amount of phosphate ester compounds with unsaturated bonds can further improve the performance of battery cells, enabling them to have high high-temperature cycle capacity retention, high high-temperature storage capacity retention, and low initial DCR.

[0222] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in the technical scope of this disclosure. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A battery cell, comprising an electrode assembly and an electrolyte, wherein the electrode assembly includes a positive electrode, a negative electrode, and a separator, the separator being located between the positive electrode and the negative electrode, wherein, The electrolyte comprises an organic solvent, an electrolyte salt, and a phosphate ester compound having unsaturated bonds, wherein the phosphate ester compound having unsaturated bonds includes compounds represented by Formula I. R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, C2-C6 alkenyl or haloalkenyl, C2-C6 ynyl or haloynyl, C1-C6 alkyl or haloalkyl, R a R b Each of the following groups is independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkyne or haloalkyne, Me is an alkali metal, and at least one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe.

2. The battery cell according to claim 1, wherein, R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, C3-C4 alkenyl or haloalkenyl, C3-C4 ynyl or haloalkynyl, R a R b Each is independently selected from C3-C4 alkenyl or haloalkenyl, C3-C4 alynyl or haloalynyl.

3. The battery cell according to claim 1 or 2, wherein, R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, allyl, haloallyl, propargyl, halopropargyl, R a R b Each is independently selected from allylene, haloallylene, propynylene, and halopropynylene.

4. The battery cell according to any one of claims 1-3, wherein, Me is Li.

5. The battery cell according to any one of claims 1-4, wherein, The phosphate ester compound having unsaturated bonds includes at least one of the following compounds and its halogenated derivatives:

6. The battery cell according to any one of claims 1-5, wherein, Based on the total mass of the electrolyte, the mass content of the phosphate ester compound with unsaturated bonds is greater than 0 and less than 2 wt%.

7. The battery cell according to claim 6, wherein, Based on the total mass of the electrolyte, the mass content of the phosphate ester compound with unsaturated bonds is greater than 0 and less than 1 wt%.

8. The battery cell according to any one of claims 1-7, wherein, The electrolyte also includes film-forming additives, which include one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

9. The battery cell according to claim 8, wherein, Based on the total mass of the electrolyte, the mass content of the film-forming additive is greater than 0 and less than 8 wt%.

10. The battery cell according to any one of claims 1-9, wherein, The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorophosphate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate; and / or, The organic solvent includes one or more of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

11. A battery device comprising a plurality of battery cells as described in any one of claims 1-10.

12. An electrical device comprising a battery cell as described in any one of claims 1-10 or a battery device as described in claim 11.

13. A method for preparing a single battery cell, wherein, Includes the following steps: An electrode assembly is provided, the electrode assembly including a positive electrode, a negative electrode, and a separator, the separator being located between the positive electrode and the negative electrode; An electrolyte is obtained by stirring and mixing an organic solvent, an electrolyte salt, and a phosphate ester compound with unsaturated bonds until homogeneous. The phosphate ester compound with unsaturated bonds includes the compound shown in Formula I, where R1, R2, and R3 are each independently selected from -R a -OMe、-R b -COOMe, C2-C6 alkenyl or haloalkenyl, C2-C6 ynyl or haloynyl, C1-C6 alkyl or haloalkyl, R a R b Each of the following groups is independently selected from C2-C6 alkenyl or haloalkenyl, C2-C6 alkyne or haloalkyne, Me is an alkali metal, and at least one of R1, R2, and R3 is selected from -R a -OMe、-R b -COOMe, The electrode assembly is placed in an outer packaging with a receiving cavity, the electrolyte is injected into the receiving cavity, and after encapsulation and formation, a battery cell is obtained.

14. The preparation method according to claim 13, wherein, Based on the total mass of the electrolyte, the amount of the phosphate ester compound with unsaturated bonds added is 0.1 wt% to 2 wt%.

15. The preparation method according to claim 13 or 14, wherein, The electrolyte also contains film-forming additives, which include one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

16. The preparation method according to claim 15, wherein, Based on the total mass of the electrolyte, the amount of the film-forming additive added is 0.1 wt% to 8 wt%.

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