A battery electrolyte, a secondary battery, and an electrical device.

Abstract

This application provides a battery electrolyte, a secondary battery, and an electrical device, belonging to the field of ion battery manufacturing. The organic solvent in the battery electrolyte includes a fluorinated dimethoxyalkane derivative having a general structural formula as shown in Formula I: wherein R1 and R2 are each independently selected from one of hydrogen-based, methoxy-based, ethoxy-based, C1-C6 chain alkyl, C3-C12 cycloalkyl, C2-C6 chain olefin, C2-C6 alkyne, and C6-C12 cycloolefin. This battery electrolyte can improve the cycle performance of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of secondary battery manufacturing, and more specifically, to a battery electrolyte, a secondary battery, and an electrical device. Background Technology

[0002] Current rechargeable batteries, such as lithium-ion batteries, typically suffer from poor cycle performance. Summary of the Invention

[0003] The purpose of this application is to provide a battery electrolyte, a secondary battery, and an electrical device that can improve the cycle performance of the secondary battery.

[0004] The embodiments of this application are implemented as follows:

[0005] In a first aspect, embodiments of this application provide a battery electrolyte, wherein the organic solvent in the battery electrolyte includes fluorinated dimethoxyalkane derivatives having a general structural formula as shown in Formula I:

[0006]

[0007] R1 and R2 are each independently selected from one of the following: hydrogen group, methoxy group, ethoxy group, C1-C6 chain alkyl group, C3-C12 cycloalkyl group, C2-C6 chain alkenyl group, C2-C6 alkyne group, and C6-C12 cycloalkenyl group.

[0008] In the above technical solution, the organic solvent has a fluorinated dimethoxyalkane derivative with the above-mentioned general structural formula. On the one hand, the fluorinated dimethoxyalkane derivative contains ether functional groups, which enables the electrolyte containing this component to form a stable solid electrolyte interface film on the surface of the metal anode (e.g., lithium metal anode). The formation of the interface film greatly reduces the contact area between the metal anode and the electrolyte, and achieves uniform deposition of metal ions at the interface, thereby effectively avoiding the formation of dendrites and improving the cycle performance of the secondary battery. On the other hand, the fluorinated dimethoxyalkane derivative also contains halogen fluorine atoms. Due to the high electronegativity and small atomic radius of fluorine atoms, and the high matching between the 2S and 2P orbitals of fluorine atoms and the corresponding orbitals of carbon atoms, the CF bond structure formed by the fluorinated dimethoxyalkane derivative is relatively stable, thereby improving the voltage resistance of the electrolyte containing this component and enabling it to exist stably at voltages higher than 4.5V.

[0009] In some alternative embodiments, the fluorinated dimethoxyalkane derivatives include one or more of 2,2,3,3-tetrafluoro-1,4-dimethoxybutane, 2,2,3,3-tetrafluoro-1,4-bis(prop-2-yn-1-oxy)butane, and 6,6,7,7-tetrafluoro-2,4,9,11-tetraoxodecane.

[0010] In the above technical solution, the fluorinated dimethoxyalkane derivatives are limited to the above range, which enables the secondary battery to have better cycle performance and high voltage resistance compared with other structures.

[0011] In some alternative implementations, the fluorinated dimethoxyalkane derivative in the organic solvent is not less than 70% by mass.

[0012] In the above technical solution, limiting the amount of fluorinated dimethoxyalkane derivatives within the above range enables the fluorinated dimethoxyalkane derivatives to have an appropriate amount, thereby more effectively improving the cycle performance and high voltage resistance of the secondary battery.

[0013] In some alternative embodiments, the remaining components in the organic solvent include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, fluoroethylene carbonate, difluoroethylene carbonate, fluoropropylene carbonate, methyl ethyl fluorocarbonate, dimethyl fluorocarbonate, diethyl fluorocarbonate, ethyl fluorocarbonate, propyl fluoroacetate, ethyl fluoropropionate, and propyl fluoropropionate.

[0014] Of the above technical solutions, the solution of this application is well applicable to the above-mentioned various organic solvent systems, and provides a number of feasible solutions, thereby facilitating the promotion and application of the solution of this application.

[0015] In some alternative embodiments, the electrolyte salt in the battery electrolyte includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium dioxalate borate, lithium difluorooxalate borate, lithium hexafluoroaluminate, lithium bistrifluoromethanesulfonylimide, lithium hexafluoroarsenate, and lithium perfluoroalkylsulfonylmethyl.

[0016] Of the above technical solutions, the solution of this application is well applicable to the above-mentioned multiple electrolyte salt systems, and provides more feasible solutions, thereby facilitating the promotion and application of the solution of this application.

[0017] In some alternative implementations, the mass percentage of electrolyte salts in the battery electrolyte is 10-20%.

[0018] In the above technical solution, limiting the amount of electrolyte salt within the above range enables the electrolyte salt to have a suitable dosage ratio, thereby ensuring the charging and discharging performance of the battery.

[0019] In some alternative embodiments, the additives in the battery electrolyte include one or more of the following: vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, ethylene sulfate, ethylene sulfite, vinyl sulfate, propylene sulfate, 1,4-dibutanesulfonate lactone, and 1,3-dipropanesulfonate lactone.

[0020] Optionally, the mass percentage of additives in the battery electrolyte is 2-10%.

[0021] Of the above technical solutions, the solution of this application is well applicable to the above-mentioned multiple additive systems, and provides more feasible implementation schemes, thereby facilitating the promotion and application of the solution of this application.

[0022] Furthermore, limiting the amount of additives to the above range allows for an appropriate dosage, thereby better improving the electrical performance of the battery.

[0023] Secondly, embodiments of this application provide a secondary battery, including a casing, an electrode assembly, and a battery electrolyte as provided in the first aspect embodiment. The electrode assembly is housed within the casing; the battery electrolyte is housed within the casing.

[0024] In the above technical solution, the secondary battery contains the battery electrolyte provided in the first aspect embodiment, which can improve the cycle performance and high voltage resistance of the secondary battery, thereby enabling the secondary battery to have better electrical performance.

[0025] In some alternative implementations, the positive electrode active material in the electrode assembly includes LiNi. x Co y Mn z O2, where x+y+z=1.

[0026] Among the above technical solutions, the solution of this application can be well applied to the above-mentioned various positive electrode active material systems, and provides more feasible solutions, thereby facilitating the promotion and application of the solution of this application.

[0027] Thirdly, embodiments of this application provide an electrical device, which includes the secondary battery provided in the second aspect embodiment. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The graph shows the test results of the pressure resistance of the organic solvent provided in the embodiments of this application. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0031] It should be noted that, in the description of this application, unless otherwise stated, "one or more" in "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two endpoints "a" and "b"; and "unit of measurement" in "numerical value a to numerical value b + unit of measurement" represents the "unit of measurement" of both "numerical value a" and "numerical value b".

[0032] Taking lithium-ion batteries as an example, lithium metal has become the most promising anode material in existing technologies due to its low electrode potential and high theoretical specific capacity. However, in the process of practical application, lithium metal has high reactivity, which makes it easy to undergo irreversible electrochemical reactions with the electrolyte, forming an unstable solid electrolyte interface film on its surface. During subsequent charge and discharge processes, the unstable solid electrolyte interface film leads to uneven lithium-ion deposition, resulting in lithium dendrites and dead lithium. The formation of lithium dendrites and dead lithium reduces the cycle life of the battery, and the generated lithium dendrites may puncture the separator, thus causing safety hazards.

[0033] In addition, although ether solvents can form a stable solid electrolyte interface film on the surface of lithium metal anodes, their electrochemical window is narrow and they are difficult to use in high-voltage systems. Although carbonate solvents have a wider electrochemical window, common solvents of this type, such as diethyl carbonate and ethylene carbonate, have poor compatibility with lithium metal, which makes it easy to form lithium dendrites, resulting in poor cycle life of the battery.

[0034] Based on this, the inventors, through creative research, discovered that they provide an organic solvent containing a fluorinated dimethoxyalkane derivative with a specific structural formula, which can improve the cycle performance of secondary batteries. At the same time, the research found that it can also improve the high-voltage resistance of the battery.

[0035] In this application, the type of battery is not limited, such as a lithium-ion battery, sodium-ion battery, or other secondary battery.

[0036] The following will use a lithium-ion battery as an example to specifically describe a battery electrolyte, a secondary battery, and an electrical device according to an embodiment of this application.

[0037] In a first aspect, embodiments of this application provide a battery electrolyte, wherein the organic solvent in the battery electrolyte includes fluorinated dimethoxyalkane derivatives having a general structural formula as shown in Formula I:

[0038]

[0039] R1 and R2 are each independently selected from one of the following: hydrogen group, methoxy group, ethoxy group, C1-C6 chain alkyl group, C3-C12 cycloalkyl group, C2-C6 chain alkenyl group, C2-C6 alkyne group, and C6-C12 cycloalkenyl group.

[0040] In this application, the organic solvent is a fluorinated dimethoxyalkane derivative with the above-mentioned general structural formula. On the one hand, the fluorinated dimethoxyalkane derivative contains ether functional groups, which enables the electrolyte containing this component to form a stable solid electrolyte interface film on the surface of the lithium metal anode. The formation of the interface film greatly reduces the contact area between the lithium metal and the electrolyte, achieving uniform deposition of lithium ions at the interface, thereby effectively avoiding the formation of lithium dendrites and improving the cycle performance of lithium-ion batteries. On the other hand, the fluorinated dimethoxyalkane derivative also contains halogen groups, specifically fluorine atoms. Due to the high electronegativity and small atomic radius of fluorine atoms, coupled with the high matching between the 2S and 2P orbitals of fluorine atoms and the corresponding orbitals of carbon atoms, the CF bond structure formed by the fluorinated dimethoxyalkane derivative is relatively stable, thereby improving the voltage resistance of the electrolyte containing this component and enabling it to exist stably at voltages higher than 4.5V.

[0041] It should be noted that the specific structure of fluorinated dimethoxyalkane derivatives is not limited and can be adjusted according to actual needs.

[0042] As an example, fluorinated dimethoxyalkane derivatives include one or more of 2,2,3,3-tetrafluoro-1,4-dimethoxybutane (see Compound 1 below), 2,2,3,3-tetrafluoro-1,4-bis(prop-2-yn-1-oxy)butane (see Compound 2 below), and 6,6,7,7-tetrafluoro-2,4,9,11-tetraoxodecane (see Compound 3 below).

[0043]

[0044] In this embodiment, by limiting the fluorinated dimethoxyalkane derivatives to the above-mentioned range, the secondary battery can have better cycle performance and high voltage resistance compared to other structures.

[0045] It should be noted that there is no specific limit to the amount of fluorinated dimethoxyalkane derivatives in the organic solvent, which can be adjusted according to actual needs.

[0046] As an example, the mass percentage of the fluorinated dimethoxyalkane derivative in the organic solvent is not less than 70%, for example, but not limited to any one of 70%, 75%, 80%, 85%, 90%, 95% and 100% or any range between two.

[0047] In this embodiment, limiting the amount of fluorinated dimethoxyalkane derivatives within the above-mentioned range enables the fluorinated dimethoxyalkane derivatives to have an appropriate amount, thereby more effectively improving the cycle performance and high voltage resistance of the secondary battery.

[0048] It should be noted that the other components in the organic solvent are not limited and can be adjusted according to actual needs.

[0049] As an example, the remaining components in the organic solvent include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, fluoroethylene carbonate, difluoroethylene carbonate, fluoropropylene carbonate, methyl ethyl fluorocarbonate, dimethyl fluorocarbonate, diethyl fluorocarbonate, ethyl fluorocarbonate, propyl fluoroacetate, ethyl fluoropropionate, and propyl fluoropropionate.

[0050] In this embodiment, the solution of this application can be well applied to the above-mentioned various organic solvent systems, providing a number of feasible solutions, thereby facilitating the promotion and application of the solution of this application.

[0051] It should be noted that there are no restrictions on the types of electrolyte salts in the battery electrolyte, and adjustments can be made according to actual needs.

[0052] As an example, the electrolyte salt in the battery electrolyte includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium dioxalate borate, lithium difluorooxalate borate, lithium hexafluoroaluminate, lithium bistrifluoromethanesulfonylimide, lithium hexafluoroarsenate, and lithium perfluoroalkylsulfonylmethyl.

[0053] In this embodiment, the solution of this application can be well applied to the above-mentioned various electrolyte salt systems, providing a number of feasible implementation schemes, thereby facilitating the promotion and application of the solution of this application.

[0054] It should be noted that there is no limit to the amount of electrolyte salt used, and it can be adjusted according to actual needs.

[0055] As an example, the mass percentage of electrolyte salts in the battery electrolyte is 10-20%, for example, but not limited to any one of the mass percentages of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%, or any range between two.

[0056] In this embodiment, limiting the amount of electrolyte salt within the above-mentioned range enables the electrolyte salt to have a suitable dosage ratio, thereby ensuring the charging performance of the battery.

[0057] It should be noted that there are no restrictions on the types of additives in the battery electrolyte, and adjustments can be made according to actual needs.

[0058] As an example, additives in battery electrolytes include one or more of the following: vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, ethylene sulfate, ethylene sulfite, vinyl sulfate, propylene sulfate, 1,4-dibutanesulfonate lactone, and 1,3-dipropanesulfonate lactone.

[0059] Optionally, the mass percentage of the additive in the battery electrolyte is 2% to 10%, for example, but not limited to any one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% and 10% or any range between two.

[0060] In this embodiment, the solution of this application can be well applied to the above-mentioned multiple additive systems, providing a number of feasible implementation schemes, thereby facilitating the promotion and application of the solution of this application.

[0061] Furthermore, limiting the amount of additives to the above range allows for an appropriate dosage, thereby better improving the electrical performance of the battery.

[0062] Secondly, embodiments of this application provide a secondary battery, including a casing, an electrode assembly, and a battery electrolyte as provided in the first aspect embodiment. The electrode assembly is housed within the casing; the battery electrolyte is housed within the casing.

[0063] In this application, the secondary battery contains the battery electrolyte provided in the first aspect embodiment, which can improve the cycle performance and high voltage resistance of the secondary battery, thereby enabling the secondary battery to have superior electrical performance.

[0064] It should be noted that the electrode assembly, also known as the battery cell, includes a positive electrode, a separator, and a negative electrode arranged in sequence.

[0065] It should be noted that there are no restrictions on the type of positive electrode active material in the electrode assembly, and it can be adjusted according to actual needs.

[0066] As an example, in the electrode assembly, the positive electrode active material includes LiNi. x Co y Mn z O2, where x+y+z=1.

[0067] In this embodiment, the solution of this application can be well applied to the above-mentioned various positive electrode active material systems, providing a number of feasible implementation schemes, thereby facilitating the promotion and application of the solution of this application.

[0068] It should be noted that for structures in secondary batteries that are not specifically described, they can be configured according to conventional choices in this field.

[0069] Thirdly, embodiments of this application provide an electrical device, which includes the secondary battery provided in the second aspect embodiment.

[0070] It should be noted that there are no restrictions on the type of electrical equipment, such as mobile phones, portable devices, laptops, electric vehicles, electric cars, ships, spacecraft, electric toys, energy storage devices, and power tools.

[0071] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0072] Example 1

[0073] This application provides a method for preparing a battery electrolyte, including the following steps:

[0074] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1) and ethyl methyl carbonate were mixed in a mass ratio of 7:3 to obtain a mixed organic solvent; then, lithium bis(trifluoromethanesulfonyl)imide and fluoroethylene carbonate were added to the mixed organic solvent to obtain a battery electrolyte; wherein the mass ratio of the mixed organic solvent, lithium bis(trifluoromethanesulfonyl)imide, and fluoroethylene carbonate was 80:15:5.

[0075] Example 2

[0076] This application provides a method for preparing a battery electrolyte, including the following steps:

[0077] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1) and ethyl methyl carbonate were mixed in a mass ratio of 7:3 to obtain a mixed organic solvent; then, lithium bis(trifluoromethanesulfonyl)imide and fluoroethylene carbonate were added to the mixed organic solvent to obtain a battery electrolyte; wherein the mass ratio of the mixed organic solvent, lithium bis(trifluoromethanesulfonyl)imide, and fluoroethylene carbonate was 88:10:2.

[0078] Example 3

[0079] This application provides a method for preparing a battery electrolyte, including the following steps:

[0080] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1) and ethyl methyl carbonate were mixed in a mass ratio of 9.9:0.1 to obtain a mixed organic solvent; then, lithium bis(trifluoromethanesulfonyl)imide and fluoroethylene carbonate were added to the mixed organic solvent to obtain a battery electrolyte; wherein the mass ratio of the mixed organic solvent, lithium bis(trifluoromethanesulfonyl)imide, and fluoroethylene carbonate was 70:20:10.

[0081] Example 4

[0082] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0083] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1) and ethyl methyl carbonate were mixed at a mass ratio of 8:2.

[0084] Example 5

[0085] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0086] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1) and ethyl methyl carbonate were mixed at a mass ratio of 9:1.

[0087] Example 6

[0088] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0089] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1) and ethyl methyl carbonate were mixed at a mass ratio of 10:0.

[0090] Example 7

[0091] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0092] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1) and ethyl methyl carbonate were mixed in a mass ratio of 5:5.

[0093] Example 8

[0094] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0095] 2,2,3,3-Tetrafluoro-1,4-bis(prop-2-yyn-1-oxy)butane (compound 2) and ethyl methyl carbonate were mixed in a mass ratio of 7:3.

[0096] Example 9

[0097] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0098] 6,6,7,7-tetrafluoro-2,4,9,11-tetraoxodecane (compound 3) and methyl ethyl carbonate were mixed in a mass ratio of 7:3.

[0099] Example 10

[0100] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0101] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1), 2,2,3,3-tetrafluoro-1,4-di(prop-2-yn-1-oxy)butane (compound 2) and ethyl methyl carbonate were mixed in a mass ratio of 3.5:3.5:3.

[0102] Example 11

[0103] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0104] 2,2,3,3-Tetrafluoro-1,4-bis(prop-2-yne-1-oxy)butane (compound 2), 6,6,7,7-tetrafluoro-2,4,9,11-tetraoxodecane (compound 3) and methyl ethyl carbonate were mixed in a mass ratio of 3.5:3.5:3.

[0105] Example 12

[0106] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0107] 2,2,3,3-tetrafluoro-1,4-dimethoxybutane (compound 1), 6,6,7,7-tetrafluoro-2,4,9,11-tetraoxodecane (compound 3) and methyl ethyl carbonate were mixed in a mass ratio of 3.5:3.5:3.

[0108] Example 13

[0109] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0110] The mass ratio of the mixed organic solvent, lithium bis(trifluoromethanesulfonyl)imide, and fluoroethylene carbonate is 90:5:5.

[0111] Example 14

[0112] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0113] The mass ratio of the mixed organic solvent, lithium bis(trifluoromethanesulfonyl)imide, and fluoroethylene carbonate is 70:25:5.

[0114] Example 15

[0115] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0116] The mass ratio of the mixed organic solvent, lithium bis(trifluoromethanesulfonyl)imide, and fluoroethylene carbonate is 84:15:1.

[0117] Example 16

[0118] This application provides a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0119] The mass ratio of the mixed organic solvent, lithium bis(trifluoromethanesulfonyl)imide, and fluoroethylene carbonate is 73:15:12.

[0120] Comparative Example 1

[0121] This application provides a comparative example of a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0122] The only organic solvent is ethylene glycol dimethyl ether.

[0123] Comparative Example 2

[0124] This application provides a comparative example of a method for preparing a battery electrolyte, which differs from Example 1 only in that:

[0125] The only organic solvent is ethyl methyl carbonate.

[0126] To facilitate understanding of the composition and ratio of electrolytes in various batteries, the following table 1 provides a summary.

[0127] It should be noted that the amount of organic solvent used is the balance after deducting the amounts recorded in Table 1 below.

[0128] Table 1. Electrolyte composition of the examples and comparative examples.

[0129]

[0130] It should be noted that EMC is an abbreviation for ethyl methyl carbonate.

[0131] Experimental Example 1

[0132] Electrical performance testing

[0133] Test method:

[0134] The battery electrolytes prepared in Examples 1-16 and Comparative Examples 1-2 were assembled into secondary batteries and numbered accordingly. Then, the capacity retention rate of the secondary batteries after 300 cycles at 25°C and 45°C, as well as the capacity retention rate, capacity recovery rate, and thickness expansion rate after 30 days of storage at 60°C, were tested.

[0135] in,

[0136] The assembly of secondary batteries shall be carried out as follows:

[0137] S1 is mixed with LiNi at a mass ratio of 96.8:2.0:1.2 0.8 Co 0.1 Mn 0.1 O2 (positive electrode active material), conductive carbon black (conductive agent), and polyvinylidene fluoride (binder) are dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry. Then, the positive electrode slurry is uniformly coated on both sides of an aluminum foil. After drying, rolling, and vacuum drying, aluminum leads are welded on using an ultrasonic welding machine to obtain a positive electrode sheet with a thickness of 125 μm.

[0138] S2 is mixed with lithium metal powder (negative electrode active material), conductive carbon black (conductive agent), and polyvinylidene fluoride (binder) in a mass ratio of 96.8:2.0:1.2 and dispersed in N-methyl-2-pyrrolidone to obtain a negative electrode slurry. Then, the negative electrode slurry is coated on both sides of a copper foil. Then, it is dried, rolled and vacuum dried in sequence, and nickel leads are welded on using an ultrasonic welding machine to obtain a negative electrode sheet with a thickness of 75μm.

[0139] S3 prepares a bare cell by winding the prepared positive electrode, negative electrode and separator (PE-coated ceramic separator, 20μm thick). Then, the bare cell, the shell and the battery electrolyte group prepared in Examples 1-16 and Comparative Examples 1-2 are injected into the dried battery. After encapsulation, standing, formation, shaping and capacity testing, the secondary battery is assembled.

[0140] The electrical parameters of a secondary battery and the corresponding calculation formulas are as follows:

[0141] Battery capacity retention test at 25°C for 300 cycles: The battery was placed at 25°C, and the initial 1C discharge capacity was tested and recorded. Then, the battery was charged and discharged at 1C current within the charge and discharge voltage range of 3.0 to 4.4V, and the discharge retention capacity after the 300th cycle was recorded.

[0142] Battery capacity retention test at 45°C for 300 cycles: The battery was placed at 45°C, and the initial 1C discharge capacity was tested and recorded. Then, the battery was charged and discharged at 1C current within the charge and discharge voltage range of 3.0 to 4.4V, and the discharge retention capacity after the 300th cycle was recorded.

[0143] Battery thickness expansion rate, capacity retention rate, and capacity recovery rate tests after 30 days of storage at 60℃: The initial thickness and initial capacity of the battery at 1C discharge were tested and recorded. Then, the battery was charged to 4.4V at a constant current and constant voltage at 1C and placed in a 60℃ explosion-proof oven. After 30 days of storage, the thermal thickness of the battery was tested in the oven. After that, the battery was taken out and cooled to room temperature. Then, its discharge retention capacity and recovery capacity at 3.0V were tested using a 1C current.

[0144] It should be noted that process parameters and steps not involved in the testing process can be set according to the conventional requirements in this field.

[0145] The calculation formula is as follows:

[0146] 300-cycle capacity retention rate (%) = (capacity retained after 300 discharges / capacity discharged after 1st cycle) × 100%;

[0147] Capacity recovery rate (%) = Recovered capacity / Initial capacity × 100%;

[0148] Thickness expansion rate (%) = (thermal thickness - initial thickness) / initial thickness × 100%.

[0149] Table 2 Electrical Performance Test Results

[0150]

[0151]

[0152] Referring to Table 2, the electrical performance test results of Examples 1-16 and Comparative Example 2 show that the electrolyte contains at least one fluorinated dimethoxyalkane derivative provided in this application. The capacity retention rate of the prepared battery after 300 cycles at 25°C and 45°C, as well as the capacity retention rate, capacity recovery rate, and thickness expansion rate after 30 days of storage at 60°C, are all significantly improved.

[0153] As can be seen from the electrical performance test results of Example 1 and Comparative Example 1, compared with the use of conventional ether organic solvents, the electrolyte containing at least one fluorinated dimethoxyalkane derivative provided in this application significantly improves the capacity retention rate of the battery after 300 cycles at 25°C and 45°C, as well as the capacity retention rate, capacity recovery rate, and thickness expansion rate after 30 days of storage at 60°C.

[0154] The electrical performance test results of Examples 1 and 4-6 show that the higher the mass percentage of fluorinated dimethoxyalkane derivatives in the organic solvent, the more significantly the capacity retention rate of the prepared battery after 300 cycles at 25°C and 45°C, as well as the capacity retention rate, capacity recovery rate, and thickness expansion rate after 30 days of storage at 60°C are improved.

[0155] The electrical performance test results of Examples 1-6 and Example 7 show that when the mass ratio of fluorinated dimethoxyalkane derivatives in the organic solvent is within the set range, the capacity retention rate of the prepared battery after 300 cycles at 25°C and 45°C, as well as the capacity retention rate, capacity recovery rate, and thickness expansion rate after 30 days of storage at 60°C, are significantly improved.

[0156] The electrical performance test results of Examples 1-3 and Examples 13-14 show that when the mass ratio of electrolyte salt in the electrolyte is within the set range, the capacity retention rate of the prepared battery after 300 cycles at 25°C and 45°C, as well as the capacity retention rate, capacity recovery rate, and thickness expansion rate after 30 days of storage at 60°C, are significantly improved.

[0157] The electrical performance test results of Examples 1-3 and Examples 15-16 show that when the mass ratio of the additive in the electrolyte is within the set range, the capacity retention rate of the prepared battery after 300 cycles at 25°C and 45°C, as well as the capacity retention rate after 30 days of storage at 60°C, are all improved to a certain extent.

[0158] Experimental Example 2

[0159] Pressure resistance test of organic solvents

[0160] Test method:

[0161] 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane (compound 1) was used as the experimental group, and a conventional ether solvent (ethylene glycol dimethyl ether) was used as the control group. Under the same test conditions, the withstand voltage performance curves of the experimental group and the control group at different voltages were tested.

[0162] It should be noted that A in the figure represents compound 1, and B in the figure represents ethylene glycol dimethyl ether.

[0163] See Figure 1It can be seen that when the voltage reaches 4V, ethylene glycol dimethyl ether is basically completely decomposed, while compound 1 is basically unaffected, indicating that the fluorinated dimethoxyalkane derivatives provided in this application have excellent high voltage resistance.

[0164] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A battery electrolyte, characterized by, The organic solvent in the battery electrolyte includes a fluorine-substituted dimethoxyalkane derivative having a structure as shown in compound 2 or / and compound 3: Compound 2; Compound 3.

2. The battery electrolyte of claim 1, wherein, The mass percentage of the fluorine-substituted dimethoxyalkane derivative in the organic solvent is not less than 70%.

3. The battery electrolyte of claim 1, wherein, The remaining components in the organic solvent include one or more of vinylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, fluorinated vinylene carbonate, difluorinated vinylene carbonate, fluorinated propylene carbonate, fluorinated ethyl methyl carbonate, fluorinated dimethyl carbonate, fluorinated diethyl carbonate, fluorinated ethyl acetate, fluorinated propyl acetate, fluorinated ethyl propionate, and fluorinated propyl propionate.

4. The battery electrolyte of claim 1, wherein, The electrolyte salt in the battery electrolyte includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethylsulfonate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium hexafluoroaluminate, lithium bis-trifluoromethylsulfonylimide, lithium hexafluoroarsenate, and lithium perfluoroalkylsulfonylmethide.

5. The battery electrolyte of claim 4, wherein, The mass percentage of the electrolyte salt in the battery electrolyte is 10-20%.

6. The battery electrolyte of claim 1, wherein, The additive in the battery electrolyte includes one or more of vinylene carbonate, vinyl ethylene carbonate, fluorinated vinylene carbonate, vinyl vinylene carbonate, ethylene sulfate, ethylene sulfite, propylene sulfite, 1,4-dibutane sulfone lactone, and 1,3-dipropyl sulfone lactone.

7. The battery electrolyte of claim 6, wherein, The mass percentage of the additive in the battery electrolyte is 2-10%.

8. A secondary battery characterized by comprising: It includes: a housing; an electrode assembly accommodated in the housing; and a battery electrolyte as claimed in any one of claims 1-7, which is accommodated in the housing. The battery includes a secondary battery as claimed in claim 8 or 9.

9. The secondary battery according to claim 8, characterized by In the electrode assembly, the positive active material includes LiNi x Co y Mn z O2, wherein x+y+z=1.

10. An electric device, characterized by ​

Images