Electrolyte and battery

Abstract

The present invention relates to the field of battery technology, and more particularly to an electrolyte and a battery comprising the electrolyte. The electrolyte contains one or more fluorinated benzene ring derivatives, the fluorinated benzene ring derivatives having a structure represented by formula (I), wherein D is #imgabs0# or #imgabs1#, and R1, R2, R3, R4, and R5 are independently selected from F, H, R6, -OR7, -SR8, -NR9R 10 ; R1, R2, R3 are not H at the same time; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C5 alkyl, C2-C4 alkene; and R6, R7, R8, R9 and R 10 Several H atoms in the electrolyte are replaced by F atoms. The electrolyte can cut off the self-discharge path, achieving a lower self-discharge level; the battery obtained with the electrolyte can reduce the self-discharge during storage, thus having better storage performance and higher safety performance. #imgabs2#

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrolyte and a battery comprising the electrolyte. Background Art

[0002] The storage performance of lithium-ion batteries is a very important performance indicator. The so-called storage performance of a battery refers to the changes in the battery's internal resistance, discharge capacity, rate performance, and cycle performance after charging the battery to a certain state of charge, storing it at a certain temperature, and storing it for a specific period of time.

[0003] In practical applications, lithium-ion batteries cannot remain in constant working order. After a period of storage, their storage performance degrades. For example, batteries undergo a long cycle from finished product to customer delivery. Before entering storage, the voltage and other parameters of the battery may be normal, but upon shipment, the voltage may be low or even zero. Battery storage performance degradation is also a common problem in everyday life. For example, a car may not start after being parked for too long, or a GPS may noticeably run out of charge or time after being used for a while after being left in the car during the summer. Backup batteries and mobile power supplies used in medical and military equipment are also subject to battery storage performance degradation.

[0004] Through experimental research, domestic and international scholars have concluded that the primary cause of lithium-ion battery storage performance degradation is excessive self-discharge, with chemical self-discharge being particularly severe. During storage, especially at high temperatures, the fully charged battery system is thermodynamically unstable and constantly shifts toward equilibrium. When these shifts accumulate to a certain level, they can cause changes in the battery's discharge capacity, impacting its rate capability and safety characteristics. Therefore, the degree of self-discharge of lithium-ion batteries under certain conditions is crucial, even becoming a key factor restricting battery performance.

[0005] Therefore, it is very important to invent a battery with low self-discharge, thus better storage performance and higher safety performance. Summary of the Invention

[0006] The present invention aims to overcome the aforementioned problems of the prior art and provides an electrolyte and a battery comprising the electrolyte. The electrolyte of the present invention can cut off the self-discharge path, achieving a lower self-discharge level; and the battery obtained using the electrolyte of the present invention can reduce self-discharge during storage, thereby having better storage performance and higher safety performance.

[0007] During the storage of the battery, the electrolyte is oxidized on the positive electrode side to produce CO2. Under the action of the electric field and diffusion, CO2 reaches the negative electrode along with the electrolyte, and CO2 interacts with the intercalated Li +The reaction causes CO2 to be almost completely consumed by the lithiated graphite and reduced to oxalate and formate at the negative electrode. Oxalate and formate diffuse back to the positive electrode and are oxidized to CO2 again at the positive electrode. + Inserting it into the positive pole again forms an interaction between the positive and negative poles, which in turn causes self-discharge.

[0008] The inventors of the present invention have discovered that by cutting off the above-mentioned self-discharge path, the degree of self-discharge during battery storage can be reduced.

[0009] After further research, the inventors discovered that, in order to block the self-discharge pathway, specific substances can be added to the electrolyte to modify the properties of the SEI film. This modified SEI then blocks the self-discharge pathway, thereby reducing the degree of self-discharge. After extensive research, the inventors identified specific substances that can block the self-discharge pathway by modifying the SEI film.

[0010] In order to achieve the above object, the first aspect of the present invention provides an electrolyte, wherein the electrolyte contains one or more fluorinated benzene ring derivatives, wherein the fluorinated benzene ring derivatives have a structure shown in formula (I),

[0011]

[0012] Where D is R1, R2, R3, R4 and R5 are each independently selected from F, H, R6, -OR7, -SR8, -NR9R 10 ; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C5 alkyl, C2-C4 alkene; and said R6, R7, R8, R9 and R 10 Several H atoms are replaced by F atoms.

[0013] A second aspect of the present invention provides a battery, wherein the electrolyte of the battery is the electrolyte described in the first aspect of the present invention.

[0014] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0015] (1) The storage self-discharge degree of the battery of the present invention is low, and the percentage of self-discharge capacity loss is low;

[0016] (2) The battery of the present invention has good safety performance;

[0017] (3) The battery of the present invention has good storage performance.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0019] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0020] The first aspect of the present invention provides an electrolyte, wherein the electrolyte contains one or more fluorinated benzene ring derivatives, and the fluorinated benzene ring derivatives have a structure shown in formula (I),

[0021]

[0022] Where D is R1, R2, R3, R4 and R5 are each independently selected from F, H, R6, -OR7, -SR8, -NR9R 10 ; R1, R2, R3 are not H at the same time; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C5 alkyl, C2-C4 alkene; and said R6, R7, R8, R9 and R 10 Several H atoms are replaced by F atoms.

[0023] By adding one or more fluorinated benzene ring derivatives of the above-mentioned specific structure to the electrolyte, the electrolyte can achieve a lower self-discharge level than the existing technology. To further improve the effect, one or more of the technical features can be further optimized.

[0024] R1, R2, R3, R4 and R5 are the same or different and are independently selected from F, H, R6, -OR7, -SR8, -NR9R 10 .

[0025] The R1, R2, and R3 cannot be H at the same time.

[0026] In one embodiment, R6, R7, R8, R9 and R 10 The same or different, each independently selected from C1-C5 alkyl (such as methyl, ethyl, propyl, butyl, pentyl), C2-C4 olefin (such as vinyl, propenyl, butenyl), and the R6, R7, R8, R9 and R 10 Several H atoms are replaced by F atoms.

[0027] In one embodiment, R6, R7, R8, R9 and R 10 The same or different, each independently selected from C1-C3 alkyl (such as methyl, ethyl, propyl), -CH=CH-CH3.

[0028] In the present invention, R6, R7, R8, R9 and R 10Some H atoms in are replaced by F atoms so that the number of H atoms in each of R1, R2, R3, R4 and R5 is an integer not greater than 4 (such as 0, 1, 2, 3, 4), preferably an integer not greater than 2 (such as 0, 1, 2).

[0029] In one embodiment, R1, R2, R3, R4 and R5 each contain no H atoms.

[0030] In the present invention, there are many different combinations of R1, R2, R3, R4 and R5.

[0031] According to a first embodiment, R1 is selected from H or F; R4 and R5 are each independently selected from F or R6; R2 and R3 are each independently selected from R6, -OR7, -SR8, -NR9R 10 ; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C5 alkyl, C2-C4 alkene; and said R6, R7, R8, R9 and R 10 Several H atoms are replaced by F atoms.

[0032] Optionally, R1 is selected from H or F; R4 and R5 are each independently selected from F or R6; R2 and R3 are each independently selected from R6, -OR7, -SR8, -NR9R 10 ; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C3 alkyl, -CH=CH-CH3; and said R6, R7, R8, R9 and R 10 Several H atoms are replaced by F atoms.

[0033] According to a second embodiment, R1 is selected from R6, -OR7, -SR8, -NR9R 10 ; R2, R3, R4 and R5 are each independently selected from H or F; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C5 alkyl, C2-C4 alkene; and said R6, R7, R8, R9 and R 10 Several H atoms are replaced by F atoms.

[0034] In one embodiment, R1 is selected from R6, -OR7, -SR8, -NR9R 10 ; R2, R3, R4 and R5 are each independently selected from H or F; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C3 alkyl, -CH=CH-CH3; and said R6, R7, R8, R9 and R 10 Several H atoms are replaced by F atoms.

[0035] In the first embodiment, the formula (I) presents a meta structure as a whole, that is, the meta positions R2 and R3 of D are selected from relatively large groups (such as R6, -OR7, -SR8, -NR9R 10 ), the para-position R1 of D is selected from a relatively small group (such as H or F). For the convenience of description, it is hereinafter referred to as the "meta-form".

[0036] In the second embodiment, the formula (I) presents a para structure as a whole, that is, the para position R1 of D is selected from a relatively large group (such as R6, -OR7, -SR8, -NR9R 10 ), the meta-position R2 and R3 of D are selected from relatively small groups (such as H or F). For the convenience of description, it is hereinafter referred to as the "para-position formula".

[0037] According to a specific embodiment, the meta-type fluorinated benzene ring derivative and the para-type fluorinated benzene ring derivative exist together.

[0038] In one embodiment, the fluorinated benzene ring derivative having a meta-structure is selected from One or more of .

[0039] In one embodiment, the fluorinated benzene ring derivative having a para-type structure is selected from

[0040] For example, R1, R2, R3, R4 and R5 include but are not limited to the following structures:

[0041]

[0042] In one embodiment, R1 is selected from

[0043] In one embodiment, R2 is selected from

[0044] In one embodiment, R3 is selected from

[0045] In one embodiment, R4 is selected from

[0046] In one embodiment, R5 is selected from

[0047] The electrolyte may contain only one type of the fluorinated benzene ring derivative, or may contain multiple types of the fluorinated benzene ring derivatives.

[0048] The fluorinated benzene ring derivative has a structure of formula (I). As can be seen from the structure, the fluorinated benzene ring derivative has a benzene ring.

[0049] D is In the present invention, the fluorinated benzene ring derivative has the following structure:

[0050]

[0051] In one embodiment, the electrolyte contains a fluorinated benzene ring derivative of formula (II), for example, selected from:

[0052] One or more of .

[0053] In one embodiment, the electrolyte contains a fluorinated benzene ring derivative of formula (III), for example, selected from:

[0054] One or more of .

[0055] In a specific embodiment, the electrolyte contains one or more fluorinated benzene ring derivatives having the structure shown in formula (II) and one or more fluorinated benzene ring derivatives having the structure shown in formula (III).

[0056]

[0057] In the present invention, the weight ratio of the fluorinated benzene ring derivative having the structure represented by formula (II) to the fluorinated benzene ring derivative having the structure represented by formula (III) is (0.5-2):1, preferably (1-1.5):1.

[0058] For example, the fluorinated benzene ring derivatives include but are not limited to the following structures:

[0059]

[0060] In one embodiment, the fluorinated benzene ring derivative includes a combination of a meta-form compound of formula (II) (e.g., formulas (II-1) and (II-2)) and a para-form compound of formula (III) (e.g., formula (III-1)).

[0061] In one embodiment, the fluorinated benzene ring derivative includes a combination of a para-form compound of formula (II) (e.g., formula (II-3)) and a meta-form compound of formula (III) (e.g., formulas (III-2) and (III-3)).

[0062] In the present invention, based on the total weight of the electrolyte, the content of the fluorinated benzene ring derivative is 0.1-15 wt %, preferably 8-10 wt %.

[0063] The present invention also provides an electrolyte, which further comprises an organic solvent and a conductive lithium salt.

[0064] In a specific embodiment, the organic solvent is selected from ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate (EA), propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, butyl One or more of ethyl butyrate, propyl butyrate, butyl butyrate, γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone, ethylene glycol dimethyl ether (DME), triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, fluoroether F-EPE, tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxolane (DOL), 1,4-dioxane (DOX), cyclopentane, dimethyl sulfoxide (DMSO), dichloromethane, and dichloroethane.

[0065] In a specific embodiment, the conductive lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium fluoroantimonate (LiSbF6), lithium difluorophosphate (LiPF2O2), 4,5-dicyano-2-trifluoromethylimidazolium lithium (LiDTI), lithium bis(oxalato)borate (LiBOB), lithium bis(malonate)borate (LiBMB), lithium difluorooxalatoborate (LiDFOB), lithium bis(difluoromalonate)borate (LiBDFMB), (malonate) borate Lithium phosphate (LiMOB), lithium (difluoromalonate oxalate) borate (LiDFMOB), lithium tris(oxalato)phosphate (LiTOP), lithium tris(difluoromalonate)phosphate (LiTDFMP), lithium tetrafluorooxalatophosphate (LiTFOP), lithium difluorobis(oxalato)phosphate (LiDFOP), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (LiN(SO2F)(SO2CF3)), lithium nitrate (LiNO3), lithium fluoride (LiF), LiN(SO2CnF 2n+1 )2、LiN(SO2F)(SO2CnF 2n+1 ) in one or more, wherein LiN(SO2CnF 2n+1 )2 and LiN(SO2F)(SO2CnF 2n+1), n can be any one of 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0066] A second aspect of the present invention provides a battery, wherein the electrolyte of the battery is the electrolyte described in the first aspect of the present invention.

[0067] The materials and preparation methods of the battery other than the electrolyte can be carried out according to the methods in the art, and can achieve the effects of low self-discharge, good storage performance and high safety performance.

[0068] The battery is preferably a lithium-ion battery.

[0069] Since the battery of the present invention contains the electrolyte of the present invention, the self-discharge degree of the battery is low, thereby improving the storage performance and the safety performance.

[0070] The present invention will be described in detail below through examples. The examples described in the present invention are only some examples of the present invention, not all examples. All other examples obtained by persons of ordinary skill in the art based on the examples of the present invention without creative work are within the scope of protection of the present invention.

[0071] Example 1

[0072] In an inert atmosphere, a solution of diethyl carbonate (DEC): ethylene carbonate (EC): ethyl methyl carbonate (EMC) in a volume ratio of 2:3:5 was added to 1 mol / L LiPF6. A fluorobenzene derivative having the structure of formula (II-1) was added, wherein the weight of the fluorobenzene derivative having the structure of formula (II-1) accounted for 10% of the total weight of the electrolyte. The mixture was mixed uniformly to prepare an electrolyte. This electrolyte was then assembled into a lithium-ion battery using a LiCoO2 positive electrode sheet, a graphite negative electrode sheet, and a PE separator.

[0073] Comparative Example 1

[0074] In an inert atmosphere, a solution of diethyl carbonate (DEC): ethylene carbonate (EC): ethyl methyl carbonate (EMC) in a volume ratio of 2:3:5 is added to 1 mol / L LiPF6 and mixed thoroughly to prepare the electrolyte. This electrolyte is then assembled into a lithium-ion battery using a LiCoO2 positive electrode sheet, a graphite negative electrode sheet, and a PE separator.

[0075] Other embodiments

[0076] Each example was carried out with reference to Example 1, except that the structure of the fluorinated benzene ring derivative in the electrolyte, the weight ratio between the structures, and the percentage of the sum of the weights of all fluorinated benzene ring derivatives to the total weight of the electrolyte are shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] Test Case

[0081] The batteries obtained in the examples were subjected to the following tests:

[0082] After fully charging the batteries produced in the Examples and Comparative Examples, they were transferred to a glove box, cut open, and the positive and negative electrode sheets were obtained. The sheets were then resealed under vacuum. The fully charged batteries, positive electrode sheets, and negative electrode sheets were tested for storage performance after 35 days at 60°C. The post-storage gas composition, residual capacity, and recovered capacity were also measured.

[0083] The obtained results are recorded in Table 2.

[0084] Table 2

[0085]

[0086] As can be seen from Table 2, the comparative examples and examples show that the percentage of self-discharge capacity of the battery of the example after storage is significantly reduced, indicating that the introduction of the fluorinated benzene ring derivative of the present invention cuts off the self-discharge path, achieves a lower self-discharge degree, improves the storage performance of the battery, and improves the safety of the battery.

[0087] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. An electrolyte, characterized in that: The electrolyte contains a fluorinated benzene ring derivative having a structure shown in formula (II) and a fluorinated benzene ring derivative having a structure shown in formula (III). （Ⅱ）， （Ⅲ）， Wherein, in formula (II), R1 is selected from H or F; R4 is selected from F or R6; R2 and R3 are each independently selected from R6, -OR7, -SR8, -NR9R 10 ; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C3 alkyl, -CH=CH-CH3, and said R6, R7, R8, R9 and R 10 Several H atoms in the formula are replaced by F atoms; in formula (III), R1, R2 and R3 are independently selected from F, H, R6, -OR7, -SR8, -NR9R 10 , R5 is selected from F, H, R6; R1, R2, R3 are not H at the same time; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C5 alkyl, C2-C4 alkene; and said R6, R7, R8, R9 and R 10 Some H atoms in are replaced by F atoms; The weight ratio of the fluorinated benzene ring derivative having the structure represented by formula (II) to the fluorinated benzene ring derivative having the structure represented by formula (III) is (1-1.5):

1. Based on the total weight of the electrolyte, the content of the fluorinated benzene ring derivative is 8-10 weight %.

2. The electrolyte according to claim 1, wherein R6, R7, R8, R9 and R in formula (II) 10 Some of the H atoms in the formula (III) are replaced by F atoms so that the number of H atoms in each of R1, R2, R3 and R4 is not greater than 4; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C3 alkyl, -CH=CH-CH3; and said R6, R7, R8, R9 and R 10 Some H atoms in R1, R2, R3 and R5 are replaced by F atoms so that the number of H atoms in each of R1, R2, R3 and R5 is not greater than 4.

3. The electrolyte according to claim 1, wherein (III) wherein R1 is selected from H or F; R5 is selected from F or R6; R2 and R3 are each independently selected from R6, -OR7, -SR8, -NR9R 10 ; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C5 alkyl and C2-C4 alkene.

4. The electrolyte according to claim 3, wherein (III) wherein R1 is selected from H or F; R5 is selected from F or R6; R2 and R3 are each independently selected from R6, -OR7, -SR8, -NR9R 10 ; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C3 alkyl, -CH=CH-CH3.

5. The electrolyte according to claim 1, wherein (III) wherein R1 is selected from R6, -OR7, -SR8, -NR9R 10 ; R2, R3 and R5 are each independently selected from H or F; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C5 alkyl and C2-C4 alkene.

6. The electrolyte according to claim 5, wherein (III) wherein R1 is selected from R6, -OR7, -SR8, -NR9R 10 ; R2, R3 and R5 are each independently selected from H or F; R6, R7, R8, R9 and R 10 Each is independently selected from C1-C3 alkyl, -CH=CH-CH3.

7. The electrolyte according to claim 1, wherein In formula (II), R1 is selected from 、 , R4 is selected from 、 、 、 、 、 , R2 and R3 are each independently selected from 、 、 、 、 、 、 、 、 、 、 、 、 、 、 and ; In formula (III), R1, R2 and R3 are each independently selected from the following structures: 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 and ; R5 is selected from the following structures 、 、 、 、 、 、 .

8. The electrolyte according to claim 1, wherein The fluorinated benzene ring derivative is selected from one or more of the following structures: （Ⅱ-1）、 （Ⅱ-2）、 （Ⅲ-1）、 （Ⅲ-2）、 （Ⅲ-3）。 9. The electrolyte according to claim 1, wherein The electrolyte further includes an organic solvent and a conductive lithium salt.

10. A battery, characterized in that: The battery comprises the electrolyte according to any one of claims 1 to 9.

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