Battery cell and method of manufacturing the same, battery device and electric device, and electrolyte combination

Abstract

The application discloses a battery monomer, a manufacturing method thereof, a battery device, a power utilization device and an electrolyte combination. The manufacturing method comprises the following steps: injecting a first electrolyte into a battery shell to obtain an initial battery monomer, the first electrolyte comprising a first organic solvent containing a fluorine-containing ester solvent, and an electric core is arranged in the battery shell; performing formation treatment on the initial battery monomer to obtain a formed battery monomer; and injecting a second electrolyte into the shell of the formed battery monomer to obtain the battery monomer, wherein the second electrolyte comprises a second organic solvent, and the donor number Dn of the second organic solvent is greater than the donor number Dn of the fluorine-containing ester solvent 1 The donor number Dn of the second organic solvent is greater than the donor number Dn of the fluorine-containing ester solvent 2 The battery monomer has good cycle performance on the basis of good kinetic performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a battery cell and its manufacturing method, a battery device and an electrical device, and an electrolyte combination. Background Technology

[0002] In the development of battery technology, attention needs to be paid to both the electrical performance of the battery, such as charging and discharging, and its manufacturing performance. Taking a single battery cell as an example, in the manufacturing process of a single battery cell, after the bare cell is placed into the casing, there is a battery electrolyte injection process, which is crucial to the overall performance of the battery.

[0003] In related technologies, single-stage or batch-stage liquid injection methods are commonly used, resulting in battery cells with poor cycle performance and kinetic properties. Therefore, improving these properties of battery cells is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application provides a battery cell and its manufacturing method, which, while maintaining good kinetic performance, also exhibits excellent cycle performance. The battery device and power-consuming device provided in this application also possess the beneficial effects of the battery cell. The electrolyte combination provided in this application, when used in the battery cell, can improve the kinetic and cycle performance of the battery cell.

[0005] In a first aspect, an embodiment of this application provides a method for manufacturing a battery cell, comprising: injecting a first electrolyte into a battery casing to obtain an initial battery cell, the first electrolyte comprising a first organic solvent containing a fluorinated ester solvent, and a battery cell disposed within the battery casing; performing a formation treatment on the initial battery cell to obtain a formed battery cell; and injecting a second electrolyte into the casing of the formed battery cell to obtain a battery cell, wherein the second electrolyte comprises a second organic solvent, and wherein the number of donors of the second organic solvent is Dn. 1 The number of donors Dn is greater than that of fluorinated ester solvents. 2 .

[0006] The first organic solvent in the first electrolyte of this application embodiment includes a fluorinated ester solvent. The number of donors in the second organic solvent is greater than the number of donors in the fluorinated ester solvent. The fluorinated ester solvent has a lower number of donors than the second organic solvent in the second electrolyte. In the formation step, this is beneficial for the fluorinated ester solvent to form a more stable and uniform solid electrolyte film during the formation of the battery cell, thereby improving the low-temperature cycle performance of the battery cell.

[0007] The fact that the number of donors for the second organic solvent is greater than that for the fluorinated ester solvent indicates that the second electrolyte has better ionic conductivity, which can enable the battery cell to have good cycle performance and rate capability.

[0008] In some optional embodiments, the number of fluorinated ester solvent donors Dn 2 The range is 4 to 10.

[0009] Number of donors Dn 2 It can reflect the solvation ability of the electrolyte, the number of donors Dn 2 Within the aforementioned range, it exhibits good stability, which is beneficial for improving the stability of the solid electrolyte membrane and enabling the battery cell to have good cycle performance in low-temperature environments.

[0010] In some optional embodiments, the fluorinated ester solvent includes one or more of methyl difluoroacetate and methyl fluorosulfonyl difluoroacetate, ethyl difluoroacetate, methyl 2,3,3,3-tetrafluoropropionate, and methyl trifluoropropionate.

[0011] The aforementioned fluorinated ester solvents have low binding energy between active ions and organic solvents, high ionic conductivity and electrochemical stability, and their low freezing point and high boiling point are beneficial for broadening the temperature range of battery cells.

[0012] In some optional embodiments, the fluorinated ester solvent has a mass fraction of 80% to 90%, optionally 84% to 88%, in the first electrolyte. This facilitates the formation of a stable solid electrolyte membrane by the fluorinated ester solvent during the formation step, further improving the low-temperature cycling performance of the battery cell.

[0013] In some optional embodiments, the first organic solvent is a fluorinated ester solvent. This allows the fluorinated ester solvent to participate first in the formation of the solid electrolyte membrane, improving the stability of the solid electrolyte membrane and reducing the probability of other organic solvents in the first organic solvent participating in the formation of the solid electrolyte membrane. This enables the battery cell to have good cycle performance while also possessing good rate capability.

[0014] In some optional embodiments, the first electrolyte further includes fluorinated additives, including one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, m-fluorotoluene, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether. These types of fluorinated additives can further reduce the number of donors of the first organic solvent in the first electrolyte, enabling the battery cell to operate stably at lower temperatures. They can also participate in the formation of the SEI film, improving the stability of the SEI film and enhancing the low-temperature cycling performance of the battery cell.

[0015] In some optional embodiments, the fluorinated additive is present in a mass fraction of 1% to 5% in the first electrolyte. This is beneficial for further reducing the number of donors of the first organic solvent in the first electrolyte and improving the cycle performance of the battery cell.

[0016] In some optional embodiments, the ionic conductivity of the first electrolyte is from 0.5 ms / cm to 2 ms / cm; optionally, it is from 0.55 ms / cm to 0.65 ms / cm. This indicates that the donor number Dn in the first electrolyte is low, and the first organic solvent therein has good stability, which can form a stable SEI film and broaden the operating temperature range of the battery cell.

[0017] In some optional embodiments, the molar concentration of lithium salt in the first electrolyte is from 0.5 mol / L to 3 mol / L. This can improve the low-temperature cycling performance of the battery cell.

[0018] In some optional embodiments, the first electrolyte comprises a lithium salt, including 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 hexafluorophosphate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. The above-mentioned lithium salts can be used in battery cells to enable the battery cells to operate normally.

[0019] In some optional embodiments, the first electrolyte comprises a lithium salt and a first organic solvent, wherein the first organic solvent is methyl difluoroacetate and / or methyl fluorosulfonyl difluoroacetate, and the molar concentration of the lithium salt in the first electrolyte is 1–2 mol / L. Therefore, the low-temperature cycling performance and kinetic performance of the battery cell are further improved.

[0020] In some optional embodiments, the mass of the first electrolyte accounts for 60% to 90% of the total injected electrolyte volume; optionally, it is 80% to 85%. Therefore, a portion of the first electrolyte participates in the formation of the SEI film, which is beneficial to improving the stability and uniformity of the SEI film; the remaining portion is mixed with the second electrolyte to form the second electrolyte in the solid-state cell working state, which is beneficial to improving the ion conduction performance of the electrolyte and improving the kinetic performance of the battery cell.

[0021] The mass of the first electrolyte as a percentage of the total electrolyte volume can be determined based on the volume, model, and specifications of the battery cell.

[0022] In some optional embodiments, the second electrolyte accounts for 10% to 40% of the total injected electrolyte mass; optionally, it is 15% to 20%. Therefore, the second electrolyte has good ion-conducting properties, and when mixed with the remaining portion of the first electrolyte, it can improve the kinetic performance of the battery cell and also improve the electrochemical performance of the battery cell at low temperatures.

[0023] In some optional embodiments, the molar concentration of lithium salt in the second electrolyte is from 0.5 mol / L to 3 mol / L. This can improve the low-temperature cycling performance of the battery cell.

[0024] In some optional embodiments, the second electrolyte comprises a lithium salt, including 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 hexafluorophosphate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. The above-mentioned lithium salts can be used in battery cells to enable the battery cells to operate normally.

[0025] In some optional embodiments, the second organic solvent includes a second ester solvent, which includes one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, and 1,4-butyrolactone. This can improve the ion conductivity of the second electrolyte and enhance the kinetic performance of the battery cell.

[0026] In some optional embodiments, the second organic solvent has a mass fraction of 80% to 90% in the second electrolyte. This allows for the formation of a second electrolyte with suitable ion-conducting properties, improving the kinetic performance of the battery cell.

[0027] In some optional embodiments, the ionic conductivity of the second electrolyte is from 5 ms / cm to 10 ms / cm; optionally, it is from 5.7 ms / cm to 8.5 ms / cm. This can improve the kinetic performance of the battery cell.

[0028] In some optional embodiments, the number of donors Dn of the second organic solvent 1 The number of donors for the second organic solvent is 5 to 20, and can be selected as 16 to 18. 1 Within the aforementioned range, the binding capacity between organic solvents and active ions in the electrolyte can be reduced, which is beneficial for the desolvation of active ions and improves the kinetic performance of the battery cell.

[0029] Secondly, embodiments of this application provide a single battery cell, manufactured using the method described in the first aspect. The battery cell of this application embodiment exhibits good cycle performance while maintaining good kinetic performance.

[0030] Thirdly, embodiments of this application provide a battery device, including a battery cell manufactured by the method of the first aspect or a battery cell of the second aspect. The battery device provided by embodiments of this application at least has the beneficial effects of a battery cell.

[0031] Fourthly, embodiments of this application provide an electrical device, including the battery device of the third aspect. The electrical device provided by embodiments of this application has at least the beneficial effects of a single battery cell or a battery device.

[0032] Fifthly, embodiments of this application provide an electrolyte combination comprising: a first electrolyte for primary electrolyte injection into a battery cell, wherein the first organic solvent in the first electrolyte is a fluorinated ester solvent; and a second electrolyte for secondary electrolyte injection into the battery cell, wherein the second electrolyte includes a second organic solvent, wherein the number of donors of the second organic solvent is Dn. 1 The number of donors Dn is greater than that of fluorinated ester solvents. 2 This electrolyte combination, when used in battery cells, enables the cells to achieve good cycle performance while maintaining good kinetic performance. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0034] Figure 1 A schematic diagram of a battery cell according to an embodiment of this application is shown.

[0035] Figure 2 A schematic diagram of an electrical device according to an embodiment of this application is shown.

[0036] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0037] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, its manufacturing method, battery device, power supply device, and electrolyte combination of this application. 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 application and are not intended to limit the subject matter of the claims.

[0038] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a 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 included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 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 application, 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.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application 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 application.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0041] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0042] Unless otherwise specified, in this application, the term "active ion" refers to an ion that can be inserted and extracted back and forth between the positive and negative electrodes of a battery cell.

[0043] In this application, "multiple" refers to two or more (including two). "Multiple types" or "several kinds" refers to two or more (including two). "Number of items" or "several items" refers to two or more (including two).

[0044] In this application embodiment, the battery cell may include a lithium-ion secondary battery cell, a lithium-ion primary battery cell, a lithium-sulfur battery cell, a sodium-lithium-ion battery cell, a sodium-ion battery cell, or a magnesium-ion battery cell, etc., and this application embodiment is not limited in this regard. The battery cell may be cylindrical, flat, cuboid, or other shapes, etc., and this application embodiment is not limited in this regard either. Battery cells are generally divided into three types according to their packaging method: cylindrical battery cells, cuboid / square battery cells, and pouch battery cells, and this application embodiment is not limited in this regard either.

[0045] The battery mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may include a battery module or a battery pack. A battery generally includes a housing for encapsulating one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0046] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0047] The solid-state battery cell mentioned in the embodiments of this disclosure is capable of charging and discharging independently. After discharging, it can be recharged to activate the active materials and continue to be used. The battery cell can be cylindrical, cuboid, or other shapes, etc., and the embodiments of this disclosure are not limited in this respect. Figure 1 The example shown is a rectangular battery cell 5.

[0048] 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.

[0049] In some alternative embodiments, the battery cell assembly is typically formed by arranging multiple battery cells.

[0050] 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.

[0051] In some alternative embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0052] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0053] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0054] 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.

[0055] 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.

[0056] In some alternative 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.

[0057] 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.

[0058] Figure 2 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0059] In some embodiments, the battery cell may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0060] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0061] A single battery cell includes a casing, electrode assembly, and electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of active ions between the positive and negative electrodes through the electrolyte.

[0062] The manufacturing process of a battery cell includes electrode fabrication, assembly, electrolyte injection, and formation. The assembly process involves fitting the positive electrode, negative electrode, and separator into the casing. The electrolyte injection process involves injecting the electrolyte into the casing; the type, amount, and efficiency of the injected electrolyte significantly affect production efficiency. Electrolyte injection typically employs single-stage or double-stage injection methods, but these conventional methods result in battery cells with poor cycle performance and kinetic performance.

[0063] Given the poor cycle performance and kinetic performance of individual battery cells in related technologies, which require further improvement, this application provides an electrolyte combination comprising: a first electrolyte for primary filling of the battery cell, wherein a first organic solvent in the first electrolyte includes a fluorinated ester solvent; and a second electrolyte for secondary filling of the battery cell, wherein the second electrolyte includes a second organic solvent, wherein the number of donors of the second organic solvent is greater than the number of donors of the fluorinated ester solvent. This electrolyte combination, when used in a battery cell, enables the battery cell to achieve good cycle performance while maintaining good kinetic performance.

[0064] In this application embodiment, a method for manufacturing a battery cell is provided, including an electrolyte injection process and a formation process. Specifically, formation is performed by injecting a first electrolyte, which includes a first organic solvent containing a fluorinated ester solvent, and then injecting a second electrolyte to improve the stability and uniformity of the solid electrolyte film on the negative electrode side, thereby improving the low-temperature cycle performance and rate capability of the battery cell.

[0065] In some optional embodiments, the battery cell includes an electrolyte, which comprises a first electrolyte and a second electrolyte. In some optional embodiments, the ionic conductivity of the electrolyte is from 0.2 ms / cm to 10 ms / cm, optionally from 0.5 ms / cm to 0.8 ms / cm, and further optionally from 0.65 ms / cm to 0.65 ms / cm. The first electrolyte undergoes formation to partially form a solid electrolyte membrane, and the remaining portion, together with the injected second electrolyte, constitutes the electrolyte of the battery cell.

[0066] The method for detecting the ionic conductivity of the electrolyte is the same as that for the first or second electrolyte described below.

[0067] This application provides a method for manufacturing a single battery cell, including steps 100, 200, and 300.

[0068] Step 100: Inject a first electrolyte into the battery casing to obtain an initial battery cell. The first electrolyte includes a first organic solvent containing a fluorinated ester solvent. The battery cell is disposed inside the battery casing.

[0069] In this step, a first electrolyte, including a fluorinated ester solvent, is injected into the shell first. The fluorinated ester solvent has good stability, which is beneficial for the subsequent formation process to prioritize the participation of the fluorinated ester solvent in the formation of the solid electrolyte membrane (SEI membrane).

[0070] Step 200: Perform formation treatment on the initial battery cell to obtain a formed battery cell.

[0071] In this step, formation processing can be carried out according to conventional procedures to form an SEI film on the negative electrode side of the battery cell.

[0072] Step 300: Inject a second electrolyte into the casing of the formed battery cell to obtain the battery cell. The second electrolyte includes a second organic solvent, wherein the number of donors Dn of the second organic solvent is... 1 The number of donors Dn is greater than that of fluorinated ester solvents. 2 .

[0073] In this step, a second electrolyte is injected. This can be a conventional electrolyte or an electrolyte with good ion conductivity, which helps maintain the normal electrochemical performance of the battery cell.

[0074] The first organic solvent in the first electrolyte of this application embodiment includes a fluorinated ester solvent, and the number of donors Dn of the second organic solvent is... 1 The number of donors Dn is greater than that of fluorinated ester solvents. 2 In the formation step, the first organic solvent in the first electrolyte includes a fluorinated ester solvent, which is beneficial for the fluorinated ester solvent to form a stable solid electrolyte membrane in the formation step, thereby improving the stability of the SEI membrane and the low-temperature cycle performance of the battery cell.

[0075] The fact that the number of donors for the second organic solvent is greater than that for the fluorinated ester solvent indicates that the second electrolyte has better ionic conductivity than the first electrolyte, which is beneficial to the performance of the battery cell at low temperatures, especially enabling the battery cell to have good cycle performance and good kinetic performance.

[0076] Compared to other commonly used organic solvents, such as ethers and non-fluorinated esters, fluorinated ester solvents have a wider electrochemical stability window, higher thermal stability, and an extremely low freezing point, which is beneficial for improving the electrochemical performance of battery cells at low temperatures.

[0077] The donor number Dn is generally used to quantitatively represent the electron-donating ability of a solvent or ligand by measuring the heat released when the solvent or ligand forms a complex (i.e., coordination heat). The more heat released, the greater the donor number of the solvent or ligand, and the stronger its electron-donating ability. Here, the donor number Dn represents the binding ability of the aforementioned organic solvent to active ions. The larger the donor number Dn, the stronger the organic solvent's ability to desolvate active ions.

[0078] In some optional embodiments, in step 100, the first organic solvent is a fluorinated ester solvent.

[0079] Number of donors Dn for fluorinated ester solvents 2 The first organic solvent is only a fluorinated ester solvent, which is lower than other commonly used organic solvents. This can prevent other organic solvents from forming a solid electrolyte membrane with the fluorinated ester solvent first or simultaneously, and further improve the low-temperature cycle performance of the battery cell. The reason for this is that the composition or thickness of the solid electrolyte membrane is more uniform.

[0080] In some optional embodiments, step 100 involves the number of fluorinated ester solvent donors, Dn. 2 The range is 4 to 10.

[0081] Optionally, the number of donors Dn of the fluorinated ester solvent can be any value among 4, 5, 6, 7, 8, 9, and 10 to obtain a range of compositions.

[0082] The number of donors, Dn, can reflect the solvation capability of the electrolyte. When the number of donors, Dn, is within the above range, it has good stability, which is beneficial to improving the stability of the solid electrolyte membrane and enabling the battery cell to have good performance in low-temperature environments.

[0083] In some optional embodiments, step 100, the fluorinated ester solvent includes one or more of methyl difluoroacetate and methyl fluorosulfonyl difluoroacetate, ethyl difluoroacetate, methyl 2,3,3,3-tetrafluoropropionate, and methyl trifluoropropionate.

[0084] The aforementioned fluorinated ester solvents have low binding energy between active ions and organic solvents, high ionic conductivity and electrochemical stability, and their low freezing point and high boiling point are beneficial for improving the temperature range of battery cells.

[0085] In some optional embodiments, in step 100, the mass fraction of the fluorinated ester solvent in the first electrolyte is 80% to 90%, optionally 84% to 88%. This facilitates the formation of a stable solid electrolyte membrane by the fluorinated ester solvent during the formation step, further improving the low-temperature cycling performance of the battery cell.

[0086] In some optional embodiments, step 100, the first electrolyte further includes a fluorinated additive, which includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, m-fluorotoluene, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether. The aforementioned fluorinated additives can further reduce the number of donors of the first organic solvent in the first electrolyte, enabling the battery cell to operate stably at lower temperatures. They can also participate in the formation of the SEI film, improving the stability of the SEI film and enhancing the low-temperature cycling performance of the battery cell.

[0087] In some optional embodiments, in step 100, the fluorinated additive in the first electrolyte has a mass fraction of 1% to 5%, optionally 2% to 3%.

[0088] Optionally, the mass fraction of the fluorinated additive in the first electrolyte can be any value or a range of its composition from 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, and 5.0%. This helps to further reduce the number of donors of the first organic solvent in the first electrolyte and improve the cycle performance of the battery cell.

[0089] In some optional embodiments, in step 100, the ionic conductivity of the first electrolyte is 0.5 ms / cm to 2 ms / cm; optionally, it is 0.6 ms / cm to 1 ms / cm.

[0090] Optionally, the ionic conductivity of the first electrolyte can be any value or a range thereof from 0.5 ms / cm, 0.6 ms / cm, 0.7 ms / cm, 0.8 ms / cm, 0.9 ms / cm, 1.0 ms / cm, 1.1 ms / cm, 1.2 ms / cm, 1.3 ms / cm, 1.4 ms / cm, 1.5 ms / cm, 1.6 ms / cm, 1.7 ms / cm, 1.8 ms / cm, 1.9 ms / cm, and 2.0 ms / cm. This indicates that the donor number Dn in the first electrolyte is relatively low, and the first organic solvent has good stability, enabling the formation of a stable SEI film and broadening the operating temperature range of the battery cell.

[0091] In some optional embodiments, in step 100, the molar concentration of lithium salt in the first electrolyte is from 0.5 mol / L to 3 mol / L; optionally, it is from 1 mol / L to 2.5 mol / L. This can improve the low-temperature cycling performance of the battery cell.

[0092] In some optional embodiments, in step 100, the first electrolyte comprises a lithium salt, which 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 hexafluorophosphate, lithium difluorodiooxalate phosphate, and lithium tetrafluorooxalate phosphate. The above-mentioned lithium salts can be used in battery cells to enable the battery cells to operate normally.

[0093] In some optional embodiments, in step 100, the first electrolyte comprises a lithium salt and a first organic solvent, wherein the first organic solvent is methyl difluoroacetate and / or methyl fluorosulfonyl difluoroacetate, and the molar concentration of the lithium salt in the first electrolyte is 1–2 mol / L. Therefore, the low-temperature cycling performance and kinetic performance of the battery cell are further improved.

[0094] In some optional embodiments, in step 100, the mass of the first electrolyte accounts for 60% to 90% of the total injected electrolyte mass; optionally, it is 80% to 85%. Exemplarily, the mass of the first electrolyte accounts for 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. of the total injected electrolyte mass. Therefore, a portion of the first electrolyte participates in the formation of the SEI film, which is beneficial to improving the stability and uniformity of the SEI film; the remaining portion is mixed with the second electrolyte to form the second electrolyte in the solid-state cell working state, which is beneficial to improving the ion-conducting performance of the electrolyte and improving the kinetic performance of the battery cell.

[0095] The mass of the first electrolyte as a percentage of the total electrolyte volume can be determined based on the volume, model, and specifications of the battery cell.

[0096] In some optional embodiments, in step 100, the first organic solvent is a fluorinated ester solvent. This allows the fluorinated ester solvent to participate first in the formation of the solid electrolyte membrane, improving the stability of the solid electrolyte membrane and reducing the probability of other organic solvents in the first organic solvent participating in the formation of the solid electrolyte membrane. This enables the battery cell to have good cycle performance while also possessing rate capability.

[0097] In some optional embodiments, in step 100, the first organic solvent may include the fluorinated ester solvent described above and / or the second organic solvent.

[0098] In some optional embodiments, the second electrolyte accounts for 10% to 40% of the total injected electrolyte mass; optionally, it is 15% to 20%. Exemplarily, the second electrolyte accounts for 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc., of the total injected electrolyte mass. Therefore, the second electrolyte has good ion-conducting properties, and when mixed with the remaining portion of the first electrolyte, it can improve the kinetic performance of the battery cell and also improve the electrochemical performance of the battery cell at low temperatures.

[0099] In some optional embodiments, in step 300, the second organic solvent has a mass fraction of 80% to 90% in the second electrolyte. This allows for the formation of a second electrolyte with suitable ion-conductivity, improving the kinetic performance of the battery cell.

[0100] In some optional embodiments, step 300, the number of donors Dn of the second organic solvent. 1 The number of donors, Dn, is 5 to 20, optionally 16 to 18. Exemplarily, the number of donors, Dn, of the second organic solvent... 1 It can be any value or a range of combinations thereof from 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. Therefore, it can reduce the binding capacity between organic solvents and active ions in the electrolyte, which is beneficial for the desolvation of active ions and improves the kinetic performance of the battery cell.

[0101] In some optional embodiments, in step 300, the second organic solvent includes a second ester solvent, which includes one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, and 1,4-butyrolactone. This can improve the ion conductivity of the second electrolyte and enhance the kinetic performance of the battery cell.

[0102] In some optional embodiments, in step 300, the molar concentration of lithium salt in the second electrolyte is from 0.5 mol / L to 3 mol / L; optionally, it is from 1 mol / L to 2.5 mol / L. This can improve the low-temperature cycling performance of the battery cell.

[0103] In some optional embodiments, in step 300, the second electrolyte comprises a lithium salt, which 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 hexafluorophosphate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. The above-mentioned lithium salts can be used in battery cells to enable the battery cells to operate normally.

[0104] In some optional embodiments, in step 300, the ionic conductivity of the second electrolyte is from 5 ms / cm to 10 ms / cm; optionally, it is from 5.7 ms / cm to 8.5 ms / cm. Optionally, the ionic conductivity of the second electrolyte can be any value or a range thereof from 5.0 ms / cm, 5.5 ms / cm, 6.0 ms / cm, 6.5 ms / cm, 7.0 ms / cm, 7.5 ms / cm, 8.0 ms / cm, 8.5 ms / cm, 9.0 ms / cm, 9.5 ms / cm, and 10.0 ms / cm. This can improve the kinetic performance of the battery cell.

[0105] In some embodiments, the first electrolyte and the second electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature power performance, etc.

[0106] The manufacturing method of the battery cell in this application also includes an assembly process. In some embodiments, the assembly process includes assembling a positive electrode sheet, a separator, and a negative electrode sheet to form a cell or electrode assembly. 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 stacking process, and the electrode assembly is placed in an outer packaging and dried. Then, an electrolyte injection process is performed, followed by encapsulation, settling, formation, and shaping processes to obtain the battery cell.

[0107] In some alternative embodiments, the battery cell includes a positive electrode, a separator, and a negative electrode.

[0108] [Negative electrode plate]

[0109] The specific composition and structure of the negative electrode sheet can be selected according to the type of battery cell, and the embodiments of this application are not limited in this regard.

[0110] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0111] The negative electrode active material is a material capable of extracting and inserting active ions, and can be any material known in the art. As examples, negative electrode active materials include, but are 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 one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide, and tin alloys. This application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials may also be used.

[0112] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0113] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: 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).

[0114] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0115] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0116] The negative electrode film 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, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0117] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application may also include a conductive undercoating layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet of this application may also include a protective layer covering the surface of the negative electrode film layer.

[0118] When the battery cell is a sodium metal battery cell, the negative electrode sheet may not include a negative electrode active material capable of releasing and embedding active ions. For example, in some embodiments, the negative electrode sheet may include a sodium sheet or a sodium alloy sheet; in other embodiments, the negative electrode sheet includes a mesh or foam-like three-dimensional framework layer, such as foamed copper or copper alloy, foamed nickel or nickel alloy, foamed aluminum or aluminum alloy, copper or copper alloy mesh, nickel or nickel alloy mesh, aluminum or aluminum alloy mesh, etc.

[0119] [Isolation membrane]

[0120] The separator is positioned between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes. This application does not impose any particular restriction on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0121] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. 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.

[0122] [Positive electrode plate]

[0123] In some embodiments, the positive electrode may include a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, the positive electrode film layer including a positive active material. The positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] In some embodiments, to further improve the energy density of a lithium-ion battery cell, the positive electrode active material may include materials with 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.

[0128] 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 0.2O2 (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.

[0129] During the charging and discharging process, lithium-ion battery cells undergo lithium intercalation and deintercalation, resulting in varying Li molar content at different discharge states. In this disclosure, the molar content of Li in the positive electrode active materials refers to the initial state of the material, i.e., before feeding. As the positive electrode active material is applied to a lithium-ion battery cell, the Li molar content changes after charge-discharge cycles. Similarly, the molar content of O in the positive electrode active materials listed in this disclosure is only a theoretical value. Oxygen release from the crystal lattice causes changes in the O molar content, leading to fluctuations in the actual O molar content.

[0130] The modified materials for the above-mentioned positive electrode active materials can be doped and / or surface coated.

[0131] In some embodiments, the positive electrode film 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.

[0132] In some embodiments, the positive electrode film 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).

[0133] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include carbon-coated aluminum foil, aluminum foil, nickel foil, and titanium foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer substrates include, but are not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0134] The positive electrode film 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 positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0135] Example

[0136] The following embodiments describe the disclosure of this application 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 the disclosure of this application. 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.

[0137] Example 1

[0138] Preparation of the positive electrode: The prepared NCM811 (LiNi) electrode was used. 0.8 Co 0.1 Mn 0.1 The positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 80:10:10. The positive electrode slurry was then prepared at a concentration of 13.6 mg / cm³. 2 The coating density was uniformly applied to an aluminum foil with a thickness of 12 μm; then dried, cold-pressed, and slit to obtain the positive electrode sheet of Example 1.

[0139] Preparation of negative electrode sheet: Artificial graphite (active material), carbon black (conductive agent), styrene-butadiene rubber (SBR, binder), and sodium carboxymethyl cellulose (CMC-Na, thickener) are mixed in a weight ratio of 97.2:0.8:0.8:1.2 and dissolved in deionized water (DI). After thorough stirring, a negative electrode slurry is obtained. This negative electrode slurry is uniformly coated onto a copper foil (negative electrode current collector) with a thickness of 6 μm using a coating device. After drying, cold pressing, die cutting, and slitting, the negative electrode sheet is obtained.

[0140] Separator: The separator is a commercial ceramic separator with a PE substrate and an alumina coating with a thickness of 7μm.

[0141] Preparation of the first electrolyte: The primary electrolyte A includes a first organic solvent and an electrolyte lithium salt A. The first organic solvent is a fluorinated ester solvent, which is a mixture of methyl difluoroacetate (MDFA, CAS No.: 433-53-4) and methyl fluorosulfonyl difluoroacetate (MDFSA, CAS No.: 680-15-9) in a mass ratio of 2:1. The number of donors for methyl difluoroacetate and methyl fluorosulfonyl difluoroacetate is 6 each. The electrolyte lithium salt A is LiTFSI with a concentration of 1 mol / L.

[0142] Preparation of the second electrolyte: The second electrolyte B includes a second organic solvent and an electrolyte lithium salt B. The second organic solvent is composed of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 3:5:2. The donor numbers of ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate are 10, 17.2, and 16, respectively. The electrolyte lithium salt B is lithium hexafluorophosphate with a concentration of 1 mol / L.

[0143] Assembly: The positive electrode, separator, and negative electrode prepared above are stacked in sequence, with the separator serving to completely isolate the positive and negative electrodes. Then, a bare cell is prepared and tabs are welded on. The cell is placed in an 80°C vacuum drying oven to remove moisture. The cell is then placed in a casing, allowed to stand at high temperature, and then 160g of the first electrolyte is injected for formation. Then, 40g of the second electrolyte is injected, and the cell is sealed to obtain a single battery cell.

[0144] Examples 2 to 6

[0145] The difference between this embodiment and Example 1 is that the type or mass content of the fluorinated ester solvent in the first electrolyte is different. In Example 6, the number of methyl trifluoropropionate (CAS No.: 18830-44-9) donors is 7, as shown in Table 1.

[0146] Examples 7 to 8

[0147] The difference between this embodiment and Embodiment 1 is that the types of lithium salts in the first electrolyte or the second electrolyte are different, as shown in Table 1.

[0148] Examples 9 to 10

[0149] The difference between this embodiment and Embodiment 1 is that the type or mass content of the second organic solvent in the second electrolyte is different, as shown in Table 1.

[0150] Examples 11 to 14

[0151] The difference between this embodiment and Embodiment 1 is that the mass content of the first electrolyte and the second electrolyte injected is different, as shown in Table 1.

[0152] Examples 15 to 16

[0153] The difference between this embodiment and Example 1 is that a fluorinated additive was added to the first electrolyte. In Examples 15 and 16, the additives were 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), with a mass content of 3% respectively. The molar concentration of lithium salt in the first electrolyte remained unchanged, as did the types of fluorinated ester solvents in the first electrolyte. The mass ratio of methyl difluoroacetate (MDFA) and methyl fluorosulfonyl difluoroacetate (MDFSA) in the fluorinated ester solvents remained unchanged, as shown in Table 1.

[0154] Comparative Example 1

[0155] The difference between this comparative example and Example 1 is that a single injection method is used. The first electrolyte and the second electrolyte from Example 1 are mixed at a mass of 160g and 40g respectively to obtain a mixed electrolyte. This mixed electrolyte is injected into the battery casing in one go, and then formation is performed. Other aspects are the same as in Example 1.

[0156] Comparative Example 2

[0157] The difference between this comparative example and Example 1 is that the two-stage electrolyte injection method of Example 1 is used, the first electrolyte in Example 1 is replaced with the second electrolyte in Example 1, formation is performed, and then the second electrolyte in Example 1 is injected. The rest is the same as in Example 1.

[0158] Comparative Example 3

[0159] The difference between this comparative example and Example 1 is that the two-stage electrolyte injection method of Example 1 is used, and the second electrolyte in Example 1 is replaced with the first electrolyte in Example 1. Specifically, the first electrolyte in Example 1 is injected first, followed by formation, and then the first electrolyte in Example 1 is injected again. The rest is the same as in Example 1.

[0160] Comparative Example 4

[0161] The difference between this comparative example and Example 1 is that the two-stage electrolyte injection method of Example 1 is used, the second electrolyte in Example 1 is replaced with the first electrolyte in Example 1; the first electrolyte in Example 1 is replaced with the second electrolyte in Example 1; specifically, the second electrolyte in Example 1 is injected first, followed by formation, and then the first electrolyte in Example 1 is injected, and the rest is the same as in Example 1.

[0162] Test section

[0163] (1) Low-temperature cycle performance test of battery cells: The battery cells prepared above were charged at -10℃ using a constant current rate of 1C to the charging cutoff voltage of 4.3V. After resting for 5 minutes, they were discharged at a constant current rate of 1C to the cutoff voltage of 2.8V. The discharge capacity was recorded, and then the cells were rested for another 5 minutes. After 500 charge-discharge cycles using the above method, the cycle capacity retention rate of the battery cells was calculated (cycle capacity retention rate = discharge capacity of the nth cycle / discharge capacity of the first cycle × 100%).

[0164] (2) Low-temperature DC internal resistance test of battery cell: In a constant temperature chamber at 25℃, the battery cell is charged to 50% SOC, and then placed at -20℃ for 2 hours. It is then discharged at 1C rate for 10 seconds. After the test is completed, the low-temperature internal resistance is calculated according to R2=△U / I.

[0165] (3) Detection of electrolyte ionic conductivity: The conductivity was calculated by measuring the current and voltage in the solution using a Mettler Toledo S470-Basic conductivity meter, which is suitable for rapid measurement of electrolyte conductivity.

[0166] Fill the test container with electrolyte, ensuring the amount is sufficient to cover the electrode. Ensure the electrode surface is smooth, free of oxides and contaminants. Calibrate the conductivity meter using a standard solution with known conductivity. Immerse the calibrated electrode in the electrolyte to be tested at 25°C. The conductivity meter will display the electrolyte's conductivity value. Record the measurement results to obtain the electrolyte's conductivity.

[0167] The test results are shown in Table 1.

[0168]

[0169]

Claims

1. A method for manufacturing a single battery cell, characterized in that, include: An initial battery cell is obtained by injecting a first electrolyte into the battery casing. The first electrolyte includes a first organic solvent containing a fluorinated ester solvent. The battery cell is disposed inside the battery casing. The initial battery cell is subjected to formation treatment to obtain a formed battery cell; injecting a second electrolyte into the casing of the formation battery cell, to obtain a battery cell, wherein the second electrolyte comprises a second organic solvent, the second organic solvent having a donor number Dn 1 greater than the donor number Dn of the fluorine-containing ester solvent 2 .

2. The manufacturing method according to claim 1, characterized in that, The fluorinated ester solvent or the first organic solvent satisfies one or more of the following conditions: (1) the donor number Dnof the fluorine-containing ester solvent is 4 to 10 2 is 4 to 10; (2) The fluorinated ester solvents include one or more of the following: methyl difluoroacetate, methyl fluorosulfonyl difluoroacetate, ethyl difluoroacetate, methyl 2,3,3,3-tetrafluoropropionate, and methyl trifluoropropionate. (3) The mass fraction of the fluorinated ester solvent in the first electrolyte is 80% to 90%; (4) The first organic solvent is a fluorinated ester solvent.

3. The manufacturing method according to claim 1 or 2, characterized in that, The fluorinated ester solvent satisfies one or more of the following conditions: (1) The second organic solvent includes a second ester solvent, which 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, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, and 1,4-butyrolactone; (2) The mass fraction of the second organic solvent in the second electrolyte is 80% to 90%; (3) the donor number Dnof the second organic solvent 1 is 5 to 20.

4. The manufacturing method according to any one of claims 1 to 3, characterized in that, The first electrolyte further includes fluorinated additives, which include one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, m-fluorotoluene, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

5. The manufacturing method according to claim 4, characterized in that, The fluorine-containing additive has a mass fraction of 1% to 5% in the first electrolyte.

6. The manufacturing method according to any one of claims 1 to 5, characterized in that, The first electrolyte and the second electrolyte each comprise a lithium salt, which 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 hexafluorophosphate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

7. The manufacturing method according to claim 6, characterized in that, The manufacturing method satisfies one or more of the following conditions: (1) The molar concentration of the lithium salt in the first electrolyte is 0.5 mol / L to 3 mol / L; (2) The molar concentration of the lithium salt in the second electrolyte is 0.5 mol / L to 3 mol / L.

8. The manufacturing method according to any one of claims 1 to 7, characterized in that, The manufacturing method satisfies one or more of the following conditions: (1) The ionic conductivity of the first electrolyte is 0.5 ms / cm to 2 ms / cm; (2) The ionic conductivity of the second electrolyte is 5 ms / cm to 10 ms / cm; (3) The mass of the first electrolyte accounts for 60% to 90% of the total injected volume; (4) The mass of the second electrolyte accounts for 10% to 40% of the total injected volume.

9. The manufacturing method according to any one of claims 1 to 8, characterized in that, The manufacturing method satisfies one or more of the following conditions: (1) The ionic conductivity of the first electrolyte is 0.55 ms / cm to 0.65 ms / cm; (2) The ionic conductivity of the second electrolyte is 5.7 ms / cm to 8.5 ms / cm; (3) The mass of the first electrolyte accounts for 80% to 85% of the total injected volume; (4) The mass of the second electrolyte accounts for 15% to 20% of the total injected volume.

10. The manufacturing method according to any one of claims 1 to 9, characterized in that, The first electrolyte comprises a lithium salt and a first organic solvent, wherein the first organic solvent is methyl difluoroacetate and / or methyl fluorosulfonyl difluoroacetate, and the mass molar concentration of the lithium salt in the first electrolyte is 1 to 2 mol / L.

11. A single battery cell, characterized in that, It is prepared by the manufacturing method of any one of claims 1 to 10.

12. A battery device, characterized in that, The battery cell is manufactured by the manufacturing method of any one of claims 1 to 10 or the battery cell described in claim 11.

13. An electrical appliance, characterized in that, Includes the battery device as described in claim 12.

14. An electrolyte combination, characterized in that, The electrolyte assembly includes: The first electrolyte is used for the initial filling of the battery cell. The first electrolyte includes a first organic solvent, which includes a fluorinated ester solvent. A second electrolyte for secondary injection of a battery cell, the second electrolyte including a second organic solvent, wherein the second organic solvent has a donor number Dn 1 greater than a donor number Dn of the fluorine-containing ester-based solvent 2 .

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