A lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device

Abstract

The present application provides a lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device, belonging to the field of battery manufacturing. The lithium-ion battery electrolyte includes an organic solvent, a lithium salt, and an additive. The additive has a structural general formula shown in Formula I: wherein, R1 to R4 are each independently selected from a hydrogen atom, a fluorine-substituted or unsubstituted C1-C6 linear alkyl group, a C3-C12 cycloalkyl group, a C2-C6 alkene group or alkyne group, a C6-C12 cyclic alkene group, a cyano group, a C1-C5 nitrile group, a methoxy group, an ethoxy group, a phenyl group, a benzene ring derivative group, and a five- or six-membered heterocyclic group. By means of this lithium-ion battery electrolyte, the problem that the electrolyte components are likely to damage the spinel structure of the material under high-voltage conditions can be solved to a certain extent, thereby improving the compatibility between the electrolyte and the spinel-structured electrode material, and further ensuring the electrical performance of the battery.

Description

Technical Field

[0001] The present application relates to the field of battery manufacturing, and more particularly, to a lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device. Background Art

[0002] In the prior art, electrode materials with a spinel structure are widely used in the manufacture of lithium-ion batteries due to their advantages such as high energy density, high voltage resistance, and good high-temperature cycle stability. However, during the charge and discharge process of the existing electrolyte under high voltage (greater than 4.5 V), there are problems such as unstable electrolyte composition and easy damage to the spinel structure of the material, resulting in poor compatibility between the electrolyte and the spinel structure electrode material, thereby affecting the electrical performance of the battery. Summary of the Invention

[0003] The purpose of the present application is to provide a lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device, which can, to a certain extent, solve the problem that the electrolyte composition is prone to damage the spinel structure of the material under high voltage conditions, thereby improving the compatibility between the electrolyte and the spinel structure electrode material, and at the same time, ensuring the electrical performance of the battery.

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

[0005] In a first aspect, an embodiment of the present application provides a lithium-ion battery electrolyte, including an organic solvent, a lithium salt, and an additive, and the additive has a structural general formula shown in Formula I:

[0006]

[0007] Wherein, R1 to R4 are each independently selected from a hydrogen atom, a fluorine-substituted or unsubstituted C1-C6 linear alkyl group, a C3-C12 cycloalkyl group, a C2-C6 alkenyl or alkynyl group, a C6-C12 cyclic alkenyl group, a cyano group, a C1-C5 nitrile group, a methoxy group, an ethoxy group, a phenyl group, a benzene ring derivative group, and a five- or six-membered heterocyclic group.

[0008] In the above technical solution, the additive component with the above structural general formula in the electrolyte, on the one hand, the additive can participate in the reaction through its own ring-opening to form a stable SEI passivation protective film on the positive and negative electrodes, thereby effectively avoiding the corrosion of the spinel-structured electrode material caused by the decomposition of the electrolyte components to produce HF, so as to play a role in protecting the electrode material; on the other hand, due to the presence of weakly basic N atoms in the additive, the weakly basic N atoms can neutralize part of the HF generated in the electrolyte, thereby reducing the acidity of the electrolyte and also playing a role in protecting the electrode material. Through the synergistic effect of the two aspects, the additive can effectively avoid the damage of the electrolyte components to the electrode material under high voltage conditions, thereby improving the compatibility between the electrolyte and the electrode material, and further ensuring the electrical performance of the battery.

[0009] In some alternative embodiments, the additive includes one or more of the following compound structures:

[0010]

[0011]

[0012] In the above technical solution, compared with using other structures, the additive with the above structural formula can play a better role in protecting the electrode material.

[0013] In some alternative embodiments, the mass percentage of the additive in the electrolyte is 0.1-10%;

[0014] Optionally, the mass percentage of the additive in the electrolyte is 1-3%.

[0015] In the above technical solution, the mass percentage of the additive is limited to the range of 0.1-10% because: if the dosage of the additive is too low, the electrode material cannot be well protected; if the dosage of the additive is too high, resource waste will be caused due to the large amount of residue of the additive in the electrolyte.

[0016] Furthermore, limiting the mass percentage of the additive to the range of 1-3% can take into account the lower economic cost while ensuring a good protection effect on the electrode material.

[0017] In some alternative embodiments, the mass percentage of the lithium salt in the electrolyte is 10-20%.

[0018] In the above technical solution, limiting the dosage of the lithium salt to the above range can make the lithium salt have an appropriate dosage ratio, thereby ensuring the charge and discharge performance of the battery.

[0019] In some alternative embodiments, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium hexafluoroaluminate, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluoroarsenate, and lithium perfluoroalkylsulfonylmethylide.

[0020] In the above technical solution, the solution of the present application can be well applied to the above-mentioned various lithium salt systems, providing more alternative embodiments, thus facilitating popularization and application.

[0021] In some alternative embodiments, the organic solvent includes a fluorinated solvent;

[0022] Optionally, the mass percentage of the fluorinated solvent in the organic solvent is 70-100%.

[0023] In the above technical solution, a fluorinated solvent is added to the organic solvent. Compared with the use of a conventional organic solvent (conventional solvents will decompose and generate gas under high pressure), the fluorinated solvent is relatively stable under high pressure, enabling the electrolyte to be relatively stable under high pressure.

[0024] Furthermore, limiting the amount of the fluorinated solvent within the above range can enable the fluorinated solvent to have an appropriate mass ratio in the organic solvent, thereby ensuring better high-pressure stability of the electrolyte.

[0025] In some alternative embodiments, the fluorinated solvent includes one or more of fluorinated ethylene carbonate, difluorinated ethylene 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.

[0026] In the above technical solution, the solution of the present application can be well applied to the above-mentioned various fluorinated solvent systems, providing more alternative embodiments, thus facilitating popularization and application.

[0027] In a second aspect, an embodiment of the present application provides a lithium-ion battery, including a housing, an electrode assembly, and a lithium-ion battery electrolyte provided as in the embodiment of the first aspect. The electrode assembly is accommodated in the housing; the lithium-ion battery electrolyte is accommodated in the housing.

[0028] In the above technical solution, the lithium-ion battery includes the lithium-ion battery electrolyte provided as in the embodiment of the first aspect, which can effectively avoid damage to the electrode material by the electrolyte during the charge and discharge process under high pressure, thereby ensuring the electrical performance of the battery.

[0029] In some alternative embodiments, in the electrode assembly, the following conditions (a) and / or (b) are satisfied;

[0030] (a) The active material of the battery positive electrode includes LiNi x Co y Mn z L (1-x-y-z) O2, where L is one or more of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, and Fe, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1;

[0031] (b) The active material of the battery negative electrode includes one or more of graphite, soft carbon, hard carbon, silicon, silicon oxide, and silicon-carbon composite.

[0032] In the above technical solutions, the solution of the present application can be well applied to the active material systems of the above-mentioned various battery positive electrodes and the active material systems of battery negative electrodes, providing more implementable solutions, thus facilitating popularization and application.

[0033] In a third aspect, an embodiment of the present application provides an electrical device, including the lithium-ion battery provided in the embodiment of the second aspect. Detailed implementation manners

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0035] It should be noted that the "and / or" in the present application, such as "feature 1 and / or feature 2", all refer to the three cases where it can be "feature 1" alone, "feature 2" alone, or "feature 1" plus "feature 2".

[0036] In addition, in the description of the present application, unless otherwise specified, the "multiple" in "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two end values "a" and "b", and the "measurement unit" in "numerical value a to numerical value b + measurement unit" represents the "measurement unit" of both "numerical value a" and "numerical value b".

[0037] In the prior art, the lithium salt in the lithium-ion battery electrolyte usually contains lithium hexafluorophosphate (LiPF6), which will decompose into HF under high-pressure conditions, and HF will damage the structure of the spinel-structured electrode material. Coupled with the fact that the organic solvent in the electrolyte will also decompose and generate gas under high pressure, the electrical performance of the battery with this type of electrode material is affected.

[0038] Based on this, the inventors provide an electrolyte containing an additive with a specific structure. Among them, the additive in the electrolyte can form an SEI passivation protective film on the electrode surface. At the same time, it can also neutralize part of the HF in the electrolyte, thereby playing a role in protecting the electrode material.

[0039] Next, a lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device according to an embodiment of the present application will be specifically described.

[0040] In a first aspect, an embodiment of the present application provides a lithium-ion battery electrolyte, including an organic solvent, a lithium salt, and an additive. The additive has a structural general formula as shown in Formula I:

[0041]

[0042] Wherein, R1 to R4 are each independently selected from a hydrogen atom, a fluorine-substituted or unsubstituted C1-C6 linear alkyl group, a C3-C12 cycloalkyl group, a C2-C6 alkene group or alkyne group, a C6-C12 cyclic alkene group, a cyano group, a C1-C5 nitrile group, a methoxy group, an ethoxy group, a phenyl group, a benzene ring derivative group, and a five-membered or six-membered heterocyclic group.

[0043] In the present application, for the additive component in the electrolyte having the above structural general formula, on the one hand, the additive can participate in the reaction through ring opening to form a stable SEI passivation protective film on the positive and negative electrode surfaces, thereby effectively avoiding the corrosion of the spinel-structured electrode material caused by the decomposition of the electrolyte components to play a role in protecting the electrode material; on the other hand, due to the presence of weakly basic N atoms in the additive, the weakly basic N atoms can neutralize part of the HF generated in the electrolyte, thereby reducing the acidity of the electrolyte and also playing a role in protecting the electrode material. Through the synergistic effect of the two aspects, the additive can effectively avoid damage to the electrode material caused by the electrolyte components under high voltage conditions, thereby improving the compatibility between the electrolyte and the electrode material, and further ensuring the electrical performance of the battery.

[0044] It should be noted that the structure of the additive is not limited and can be adjusted according to actual needs.

[0045] As an example, the additive includes one or more of the following compound structures:

[0046]

[0047] In this embodiment, using the additive with the above structural formula can play a better role in protecting the electrode material compared to using other structures.

[0048] In other possible embodiments, the additive includes one or more of the following compound structures:

[0049]

[0050]

[0051] It should be noted that the dosage of the additive is not limited and can be adjusted according to actual needs.

[0052] As an example, the mass percentage of the additive in the electrolyte is 0.1 - 10%, such as but not limited to any one of the point values of 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% and 10% or the range value between any two of them.

[0053] Optionally, the mass percentage of the additive in the electrolyte is 1 - 3%, such as but not limited to any one of the point values of 1%, 1.5%, 2%, 2.5% and 3% or the range value between any two of them.

[0054] In this embodiment, the mass percentage of the additive is limited to the range of 0.1 - 10% because: if the dosage of the additive is too low, the electrode material cannot be well protected; if the dosage of the additive is too high, resource waste will be caused due to more residues of the additive in the electrolyte.

[0055] Furthermore, limiting the mass percentage of the additive to the range of 1 - 3% can take into account the lower economic cost while ensuring a good protection effect on the electrode material.

[0056] It should be noted that the dosage of the lithium salt is not limited and can be adjusted according to actual needs.

[0057] As an example, the mass percentage of the lithium salt in the electrolyte is 10 - 20%, such as but not limited to any one of the point values of 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% and 20% or the range value between any two of them.

[0058] In this embodiment, limiting the dosage of the lithium salt to the above range can make the lithium salt have an appropriate dosage, thus ensuring the charge and discharge performance of the battery.

[0059] It should be noted that the type of the lithium salt is not limited and can be adjusted according to actual needs.

[0060] As an example, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium hexafluoroaluminate, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluoroarsenate and lithium perfluoroalkylsulfonylmethyl.

[0061] In this embodiment, the solution of the present application can be well applied to the above-mentioned various lithium salt systems, providing more implementable solutions, thus facilitating popularization and application.

[0062] It should be noted that since existing organic solvents are difficult to exist stably under high-pressure conditions, considering the overall stability of the electrolyte, the composition of the organic solvent in the electrolyte can be adjusted.

[0063] As an example, the organic solvent includes fluorinated solvents;

[0064] Optionally, the mass percentage of the fluorinated solvent in the organic solvent is 70-100%.

[0065] In this embodiment, a fluorinated solvent is added to the organic solvent. Compared with using a conventional organic solvent (conventional solvents will decompose and generate gas under high pressure), the fluorinated solvent is relatively stable under high pressure, enabling the electrolyte to be relatively stable under high pressure.

[0066] Furthermore, limiting the amount of the fluorinated solvent within the above range can make the fluorinated solvent have an appropriate mass ratio in the organic solvent, thereby ensuring better high-pressure stability of the electrolyte.

[0067] It should be noted that the type of the fluorinated solvent is not limited and can be adjusted according to actual needs.

[0068] As an example, the fluorinated solvent includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, fluoropropylene carbonate, fluoromethyl ethyl carbonate, fluorodimethyl carbonate, fluorodiethyl carbonate, fluoroethyl acetate, fluoropropyl acetate, fluoroethyl propionate, and fluoropropyl propionate.

[0069] In this embodiment, the solution of the present application can be well applied to the above-mentioned various fluorinated solvent systems, providing more implementable solutions, thus facilitating popularization and application.

[0070] It can be understood that the type of the ordinary solvent in the organic solvent is also not limited.

[0071] As an example, the ordinary solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, and propyl propionate.

[0072] In a second aspect, an embodiment of the present application provides a lithium-ion battery, including a housing, an electrode assembly, and a lithium-ion battery electrolyte provided as in the embodiment of the first aspect. The electrode assembly is accommodated in the housing; the lithium-ion battery electrolyte is accommodated in the housing.

[0073] In this embodiment, the lithium-ion battery includes the lithium-ion battery electrolyte provided by the first aspect embodiment, which can effectively avoid damage to the electrode material by the electrolyte during the charge and discharge process under high voltage conditions, thereby ensuring the electrical performance of the battery.

[0074] As an example, in the electrode assembly, the following conditions (a) and / or (b) are satisfied;

[0075] (a) The active material of the battery positive electrode includes LiNi x Co y Mn z L (1-x-y-z) O2, where L is one or more of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, and Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1;

[0076] (b) The active material of the battery negative electrode includes one or more of graphite, soft carbon, hard carbon, silicon, silicon oxide compound, and silicon-carbon composite.

[0077] In this embodiment, the solution of the present application can be well applied to the above-mentioned various active material systems of the battery positive electrode and the active material system of the battery negative electrode, providing more feasible implementation schemes, thereby facilitating popularization and application.

[0078] It should be noted that for the structures not specifically described in the lithium-ion battery, they can all be set according to the conventional selection in the art.

[0079] In the third aspect, the embodiment of the present application provides an electrical device, including the lithium-ion battery provided by the second aspect embodiment.

[0080] It should be noted that the type of the electrical device is not limited, for example, it is a mobile phone, a portable device, a laptop computer, a battery car, an electric vehicle, a ship, a spacecraft, an electric toy, an energy storage device, an electric tool, etc.

[0081] The features and performance of the present application will be further described in detail below in conjunction with embodiments.

[0082] Embodiment 1

[0083] The embodiment of the present application provides a preparation method for a lithium-ion battery electrolyte, including the following steps:

[0084] Mix a common organic solvent and a fluorinated solvent; wherein, the common organic solvent includes: 7.5% ethylene carbonate (EC) and 7.5% ethyl methyl carbonate (EMC); the fluorinated solvent includes: 64.5% fluorinated ethyl methyl carbonate (FEMC) and 5% fluorinated ethylene carbonate (FEC).

[0085] Add 0.5% of Compound 1 and 15% of lithium hexafluorophosphate (LiPF6) to the mixed solvent and mix evenly to obtain the lithium-ion battery electrolyte.

[0086] Example 2

[0087] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is different from Example 1 in that: add 1% of Compound 1 to the mixed solvent, and the change in the mass of the compound is adjusted by the dosage of fluoroethylene carbonate (FEMC).

[0088] Example 3

[0089] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is different from Example 1 in that: add 2% of Compound 1 to the mixed solvent, and the change in the mass of the compound is adjusted by the dosage of fluoroethylene carbonate (FEMC).

[0090] Example 4

[0091] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is different from Example 1 in that: add 3% of Compound 1 to the mixed solvent, and the change in the mass of the compound is adjusted by the dosage of fluoroethylene carbonate (FEMC).

[0092] Example 5

[0093] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is different from Example 1 in that: add 5% of Compound 1 to the mixed solvent, and the change in the mass of the compound is adjusted by the dosage of fluoroethylene carbonate (FEMC).

[0094] Example 6

[0095] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is different from Example 3 in that: add 2% of Compound 2 to the mixed solvent.

[0096] Example 7

[0097] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is different from Example 3 in that: add 2% of Compound 3 to the mixed solvent.

[0098] Example 8

[0099] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is different from Example 3 in that: add 2% of Compound 4 to the mixed solvent.

[0100] Example 9

[0101] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is different from Example 3 in that 1% of Compound 1 and 1% of Compound 2 are added to the mixed solvent.

[0102] Example 10

[0103] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is different from Example 3 in that 1% of Compound 1 and 1% of Compound 3 are added to the mixed solvent.

[0104] Example 11

[0105] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is different from Example 3 in that 1% of Compound 1 and 1% of Compound 4 are added to the mixed solvent.

[0106] Example 12

[0107] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is different from Example 4 in that 1% of Compound 1, 1% of Compound 2, and 1% of Compound 4 are added to the mixed solvent.

[0108] Example 13

[0109] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is different from Example 1 in that a common organic solvent and a fluorinated solvent are mixed; wherein, the common organic solvent includes: 6.5% of ethylene carbonate (EC), 6.5% of ethyl methyl carbonate (EMC), and 2% of diethyl carbonate (DEC); the fluorinated solvent includes: 64.5% of fluorinated ethyl methyl carbonate (FEMC) and 5% of fluorinated diethyl carbonate (FDEC).

[0110] Example 14

[0111] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is different from Example 1 in that only the common organic solvents are mixed; wherein, the common organic solvent includes: 30.5% of ethylene carbonate (EC), 30.5% of ethyl methyl carbonate (EMC), and 23.5% of diethyl carbonate (DEC).

[0112] Comparative Example 1

[0113] The comparative example of the present application provides a method for preparing a lithium-ion battery electrolyte, which is different from Example 1 in that 0.5% of Compound 1 is not added to the mixed solvent, and the change in the mass of the compound is adjusted by the amount of fluorinated ethyl methyl carbonate (FEMC) used.

[0114] Test Example 1

[0115] Electrical Performance Test

[0116] Test Method:

[0117] The lithium-ion battery electrolytes prepared in Examples 1 to 14 and Comparative Example 1 were assembled into batteries and numbered correspondingly. Then, the capacity retention rates of the batteries after 300 cycles at 25°C and 45°C, as well as the capacity retention rate, capacity recovery rate, and thickness swelling rate after 7-day storage at 60°C were tested respectively.

[0118] Among them,

[0119] The battery assembly was carried out according to the following method:

[0120] S1 Mix LiNi 0.2 Co 0.2 Mn 0.2 Al 0.4 O2 (cathode active material), conductive carbon black (conductive agent), and polyvinylidene fluoride (binder) in a mass ratio of 96.8:2.0:1.2, disperse in N-methyl-2-pyrrolidone to obtain the cathode slurry; then, coat the cathode slurry evenly on both sides of the aluminum foil; then, successively go through drying, rolling, and vacuum drying, and weld the aluminum lead wire with an ultrasonic welder to obtain a cathode sheet with a thickness of 125μm.

[0121] S2 Mix graphite (anode active material), conductive carbon black (conductive agent), styrene-butadiene rubber, and carboxymethyl cellulose (binder) in a mass ratio of 95:1.5:1.5:2, disperse in deionized water to obtain the anode slurry; then, coat the anode slurry on both sides of the copper foil; then, successively go through drying, rolling, and vacuum drying, and weld the nickel lead wire with an ultrasonic welder to obtain an anode sheet with a thickness of 125μm.

[0122] S3 Wind the prepared cathode sheet, anode sheet, and ion separator (a 20μm thick PE ceramic separator) to prepare a bare battery cell, and then assemble the bare battery cell, the housing, and the lithium-ion battery electrolytes prepared in Examples 1 to 14 and Comparative Example 1 into a battery.

[0123] The test of the electrical parameters corresponding to the battery and the corresponding calculation formulas are as follows:

[0124] Test of the capacity retention rate of the battery after 300 cycles at 25°C: Place the lithium-ion battery at room temperature, and then perform 300 charge-discharge cycles on the lithium-ion battery at a current of 0.33C. The test voltage window is 3.0 - 4.9V, and record the discharge retention capacity of the 300th cycle.

[0125] 45°C Cycle Capacity Retention Test of the Battery: Place the lithium-ion battery in an incubator at 45°C and let it stand for 4 h. Then, perform 300 charge-discharge cycles on the lithium-ion battery at a current of 0.33C. The test voltage window is 3.0 - 4.9V, and record the discharge retention capacity of the 300th cycle.

[0126] 7-day Storage Thickness Expansion Rate, Capacity Retention, and Capacity Recovery Tests of the Battery at 60°C: Test and record the initial thickness and the initial 0.33C discharge capacity of the lithium-ion battery. Then, charge the battery at a constant current and constant voltage to 4.9V at a current of 0.33C, place it in an explosion-proof oven at 60°C, and after storing for 7 days, test the thermal measurement thickness of the battery in the oven. Then, take out the battery and cool it to room temperature, and test its discharge retention capacity and recovery capacity when discharging to 3.0V at 0.33C.

[0127] The calculation formulas are as follows:

[0128] Capacity retention rate after 300 cycles (%) = (Discharge retention capacity of the 300th cycle / Discharge capacity of the 1st cycle) × 100%;

[0129] Storage capacity retention rate (%) = Retention capacity / Initial capacity × 100%;

[0130] Capacity recovery rate (%) = Recovery capacity / Initial capacity × 100%;

[0131] Thickness expansion rate (%) = (Thermal measurement thickness - Initial thickness) / Initial thickness × 100%.

[0132] Table 1 Test Results of Electrical Properties

[0133]

[0134]

[0135] Referring to Table 1, from the test results of the electrical properties of Examples 1 - 14 and Comparative Example 1, it can be seen that when the electrolyte contains the additive provided in this application, the capacity retention rates of the prepared battery at 25°C and 45°C after 300 cycles, as well as the capacity retention rate, capacity recovery rate, and thickness expansion rate during storage at 60°C for 7 days, are all significantly improved.

[0136] From the test results of the electrical properties of Examples 1 - 5, it can be seen that when the mass ratio of the additive is in the range of 1% - 3%, compared with other ranges of mass ratio, the test results of the electrical properties of the battery are better.

[0137] From the test results of the electrical properties of Example 3 and Examples 6 - 12, and Example 4 and Example 12, it can be seen that when the dosage of the additive is certain, different types of additives can also cause similar improvements in electrical properties.

[0138] As can be seen from the electrical property test results of Example 1 and Example 13, when the dosage of the fluorinated solvent is fixed, changing the types of the common solvent and the fluorinated solvent can also approximately improve the electrical properties.

[0139] As can be seen from the electrical property test results of Example 1 and Example 14, when a fluorinated solvent is added to the organic solution, the capacity retention rates 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 swelling rate after storage at 60°C for 7 days are all significantly improved.

[0140] The embodiments described above are some, but not all, of the embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without making creative efforts fall within the scope of protection of the present application.

Claims

1. A lithium-ion battery electrolyte, characterized in that, It includes an organic solvent, a lithium salt and an additive, and the additive has a structural general formula shown in Formula I: Formula I Wherein, R1 to R4 are each independently selected from a hydrogen atom, a fluorine-substituted or unsubstituted C1-C6 linear alkyl group, a C3-C12 cycloalkyl group, a C2-C6 alkenyl group or alkynyl group, a C6-C12 cyclic alkenyl group, a cyano group, a C1-C5 nitrile group, a methoxy group, an ethoxy group, a phenyl group, a benzene ring derivative group, and a five- or six-membered heterocyclic group; The mass percentage of the additive in the electrolyte is 0.1-10%.

2. The lithium-ion battery electrolyte according to claim 1, characterized in that, The additive includes one or more of the following compound structures: Compound 1 Compound 2 Compound 3 Compound 4.

3. The electrolyte for a lithium-ion battery according to claim 1, characterized in that, The mass percentage of the additive in the electrolyte is 1-3%.

4. The lithium-ion battery electrolyte according to any one of claims 1 to 3, characterized in that, The mass percentage of the lithium salt in the electrolyte is 10-20%.

5. The electrolyte for a lithium-ion battery according to claim 4, wherein The lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium hexafluoroaluminate, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluoroarsenate, and lithium perfluoroalkylsulfonylmethyl.

6. The lithium-ion battery electrolyte according to any one of claims 1 to 3, characterized in that, The organic solvent includes a fluorinated solvent.

7. The electrolyte for a lithium-ion battery according to claim 6, wherein The mass percentage of the fluorinated solvent in the organic solvent is 70-100%.

8. The electrolyte for a lithium-ion battery according to claim 6, characterized in that, The fluorinated solvent includes one or more of fluorinated ethylene carbonate, difluorinated ethylene 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.

9. A lithium-ion battery, characterized in that, It includes: A housing; An electrode assembly, which is accommodated in the housing; And The lithium-ion battery electrolyte according to any one of claims 1-8, and the lithium-ion battery electrolyte is accommodated in the housing.

10. The lithium ion battery according to claim 9, characterized in that, In the electrode assembly, the following conditions (a) and / or (b) are satisfied; (a) The active material of the battery positive electrode includes LiNi x Co y Mn z L (1-x-y-z) O2, where L is one or more of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, and Fe, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1; (b) The active material of the battery negative electrode includes one or more of graphite, soft carbon, hard carbon, silicon, silicon oxide, and silicon-carbon composite.

11. An electrical device, characterized in that, The electrical device includes the lithium-ion battery according to claim 9 or 10.

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