An electrolyte and a battery comprising the same

Abstract

This invention provides an electrolyte and a battery containing the same. The electrolyte comprises an electrolyte salt, a solvent, and a potassium nitrile phenyl trifluoroborate compound. The potassium nitrile phenyl trifluoroborate compound contains boron-based, nitrile-based, and benzene-based functional groups. The boron-based functional groups readily coordinate with the oxygen in the positive electrode, enhancing positive electrode protection; the nitrile-based functional groups readily coordinate with the transition metal in the positive electrode, further strengthening the protection of the positive electrode; and the benzene-based functional groups facilitate the oxidation and film formation of the potassium nitrile phenyl trifluoroborate compound at the positive electrode. The potassium nitrile phenyl trifluoroborate compound added to the electrolyte of this invention significantly improves the high-temperature, high-pressure intermittent cycling and storage performance of the battery, resulting in a significant improvement in high-temperature intermittent cycling and a significant reduction in high-temperature storage expansion.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, and more specifically to an electrolyte and a battery containing the electrolyte. Background Technology

[0002] Lithium-ion batteries, as energy storage devices, have become widely used in portable electronic products and are applied on a large scale in energy storage, electric vehicles and other fields. In order to meet people's urgent requirements for improving the performance of lithium-ion batteries, it is necessary to develop lithium-ion batteries with higher energy density. However, improving energy density poses a severe challenge to the reversibility and safety of lithium-ion batteries.

[0003] To achieve the required higher energy density, higher voltages are generally used; however, increasing the voltage leads to a significant deterioration in battery life. Higher voltages increase side reactions throughout the system, including oxidation reactions on the positive electrode surface, which leads to electrolyte decomposition. These reactions also reduce electrode stability; lithium extraction results in a rock salt structure and reduced capacity; and finally, transition metal dissolution occurs, metal ions are extracted from the positive electrode, and the thickness of the solid electrolyte on the negative electrode surface increases. These side reactions are particularly pronounced at high temperatures, thus worsening the battery's high-temperature, high-pressure performance.

[0004] For electrolytes, traditional methods to improve high-voltage performance mainly involve optimizing the electrolyte formulation, including optimizing common solvent components and additives. However, with the continuous increase in voltage, traditional solvents and additives are becoming increasingly inadequate for achieving sufficiently good high-temperature and high-voltage performance. Therefore, it is necessary to continue developing novel and effective high-voltage protection additives. Summary of the Invention

[0005] In view of this, the present invention provides an electrolyte and a battery comprising the same, wherein the electrolyte includes potassium nitrilophenyl trifluoroborate additives, which have a low oxidation potential and can form a stable interfacial film at the positive electrode. Meanwhile, boron, being an electron-deficient functional group, can coordinate with oxygen, further improving the surface structural stability of the positive electrode, thereby improving the high-temperature and high-pressure performance of the battery.

[0006] To address the technical problems mentioned in the background section, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an electrolyte comprising:

[0008] Electrolyte salts, solvents, potassium nitrile trifluoroborate compounds;

[0009] The structural formula of the potassium nitrile phenyl trifluoroborate compound is shown in formula (1):

[0010]

[0011] In formula (1), at least one of R1 and R2 contains a cyano functional group.

[0012] Furthermore, R1 and R2 are independently selected from H and C, respectively. 1-10 Alkyl, -C 1-10 Alkyl-C(=O)-OC 1-10 Alkyl group, with at least one R a Replacement C 1-10 Alkyl group, with at least one R a Replacement -C 1-10 Alkyl-C(=O)-OC 1-10 Alkyl-; R a Contains cyano, halogen and C 1-10 At least one of the alkyl groups.

[0013] Furthermore, the structural formula of the potassium nitrile phenyl trifluoroborate compound is selected from at least one of formulas 1-1 to 1-6, where formulas 1-1 to 1-6 are:

[0014]

[0015] Furthermore, the amount of the potassium nitrile phenyl trifluoroborate compound added accounts for 0.05 to 1 wt.% of the total mass of the electrolyte.

[0016] Furthermore, the electrolyte further includes a fluorinated compound, which includes at least one selected from fluoroethylene carbonate, methyl trifluoroethyl carbonate, diethyl fluorocarbonate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, ethyl 2,2,2-trifluoroacetate, ethyl 2,2-difluoroacetate, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

[0017] Furthermore, the amount of the fluorinated compound added accounts for 5 to 20 wt% of the total mass of the electrolyte.

[0018] Furthermore, the electrolyte further includes sulfonic acid additives, wherein the sulfonic acid additives include at least one of 1,3-propanesulfonyl lactone, 1-propene-1,3-sulfonyl lactone, 5-methyloxathiapentane 2,2-dioxide, 1,3-propenesulfonyl lactone, 2,4-butanesulfonyl lactone, and 1,4-butanesulfonyl lactone.

[0019] Furthermore, the solvent includes carbonates and / or carboxylic acid esters;

[0020] The carbonate includes at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; the carboxylic acid ester includes at least one selected from propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate, ethyl propionate, methyl butyrate, and n-ethyl butyrate; and / or

[0021] The electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalate) phosphate, lithium tetrafluoroborate, lithium bis(oxalate) borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(trifluoromethylsulfonyl)imide, lithium di(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethylsulfonyl)methyl, and lithium di(trifluoromethylsulfonyl)imide.

[0022] Furthermore, the electrolyte also includes nitrile compounds; the nitrile compounds include at least one of adiponitrile, succinate, and 1,3,6-hexanetrionitrile.

[0023] In a second aspect, the present invention provides a battery comprising:

[0024] The electrolyte as described above;

[0025] Positive electrode sheet containing positive active material;

[0026] Anode sheet and separator containing negative electrode active material.

[0027] The beneficial effects of the above-described technical solution of the present invention are as follows:

[0028] This invention provides an electrolyte and a battery containing the same, wherein the electrolyte comprises: an electrolyte salt, a solvent, and a potassium nitrile phenyl trifluoroborate compound; wherein the structural formula of the potassium nitrile phenyl trifluoroborate compound is shown in formula (1):

[0029]

[0030] In formula (1), at least one of R1 and R2 contains a cyano functional group.

[0031] The electrolyte of this invention includes a potassium nitrile phenyl trifluoroborate compound, which contains boron, nitrile, and benzene functional groups. The boron functional groups readily coordinate with the oxygen in the positive electrode, enhancing its protection; the nitrile functional groups readily coordinate with the transition metal in the positive electrode, further strengthening its protection; and the benzene functional groups facilitate the oxidation and film formation of the potassium nitrile phenyl trifluoroborate compound at the positive electrode. Therefore, under the influence of the potassium nitrile phenyl trifluoroborate compound in the electrolyte, the positive electrode exhibits highly stable interface protection, significantly improving the stability of the electrolyte and its interface, reducing electrolyte consumption during battery cycling, and minimizing damage to the positive electrode structure. The potassium nitrile phenyl trifluoroborate compound added to the electrolyte of this invention can significantly improve the battery's high-temperature, high-pressure intermittent cycling and storage performance, significantly enhancing high-temperature intermittent cycling performance and significantly reducing high-temperature storage expansion.

[0032] Furthermore, sulfonic acid additives in the electrolyte can help form a film on the negative electrode, thus significantly affecting gas generation on the negative electrode surface. During high-temperature storage, residual sulfonic acid additives in the electrolyte can also effectively suppress gas generation. Overall, sulfonic acid additives contribute to film formation on the negative electrode, reducing gas generation issues during battery cycling and storage. Nitriles have high carbon-nitrogen triple bonds, making them resistant to oxidation. Therefore, nitriles exhibit excellent stability and strong oxidation resistance on the positive electrode. Simultaneously, the cyano group has strong coordination ability, allowing it to bind to active sites on the electrode surface, masking these active ions and reducing the decomposition of the electrolyte by the electrode. On the positive electrode, nitriles are stable on their own and can complex with some active ions, thus enhancing the electrolyte's resistance to positive electrode oxidation and improving the battery's cycle life under high voltage.

[0033] In this invention, when potassium nitrile phenyl trifluoroborate compounds are used in conjunction with sulfonic acid additives and nitrile compounds, they can compensate for shortcomings and synergistically enhance battery performance. Specifically, sulfonic acid additives can supplement the electrolyte's role in forming a film on the negative electrode and protecting it; nitrile compounds and potassium nitrile phenyl trifluoroborate compounds can work together on the positive electrode, resulting in a synergistic effect from multiple aspects, forming a more stable interface protection for the positive electrode, reducing electrolyte consumption during battery cycling, and improving the battery's cycle life under high temperature and high pressure. Attached Figure Description

[0034] Figure 1 The structural formula is given for potassium nitrilophenyl trifluoroborate compounds in the electrolyte. Detailed Implementation

[0035] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0036] The electrolyte and the battery containing the electrolyte in this invention will be further explained and described below with reference to specific embodiments.

[0037] In a first aspect, the present invention provides an electrolyte comprising: an electrolyte salt, a solvent, and a potassium nitrile phenyl trifluoroborate compound; wherein the structural formula of the potassium nitrile phenyl trifluoroborate compound is shown in formula (1):

[0038]

[0039] In formula (1), at least one of R1 and R2 contains a cyano functional group.

[0040] To address the problems of large side reactions in the electrolyte and interface of existing batteries under high voltage and significant performance degradation under high temperature and pressure, this invention provides an electrolyte comprising a potassium nitrile phenyl trifluoroborate compound. This potassium nitrile phenyl trifluoroborate compound contains boron, nitrile, and benzene functional groups. The boron functional groups readily coordinate with oxygen at the positive electrode, enhancing positive electrode protection; the nitrile functional groups readily coordinate with the transition metal at the positive electrode, further strengthening protection; and the benzene functional groups, due to their unsaturated structure, make benzonitrile substances more easily oxidized than nitrile substances, thus facilitating the oxidation and film formation of the potassium nitrile phenyl trifluoroborate compound at the positive electrode. Therefore, under the influence of the potassium nitrile phenyl trifluoroborate compound in the electrolyte, the positive electrode exhibits very stable interface protection, significantly improving the stability of the electrolyte and its interface, reducing electrolyte consumption during battery cycling, and minimizing damage to the positive electrode structure. The potassium nitrile phenyl trifluoroborate compound added to the electrolyte of this invention can significantly improve the high-temperature and high-pressure intermittent cycling and storage performance of the battery, resulting in a significant improvement in high-temperature intermittent cycling and a significant reduction in high-temperature storage expansion.

[0041] According to some embodiments of the present invention, R1 and R2 are each independently selected from C. 1-10 Alkyl, -C 1-10 Alkyl-C(=O)-OC 1-10 Alkyl group, with at least one R a Replacement C 1-10 Alkyl group, with at least one R a Replacement -C 1-10 Alkyl-C(=O)-OC 1-10 Alkyl-; R a Contains cyano, halogen and C 1-10At least one of alkyl groups. Further, R1 and R2 are each independently selected from C1. 1-6 Alkyl, -C 1-6 Alkyl-C(=O)-OC 1-6 Alkyl group, with at least one R a Replacement C 1-6 Alkyl group, with at least one R a Replacement -C 1-6 Alkyl-C(=O)-OC 1-6 Alkyl-; R a Contains cyano, halogen and C 1-6 At least one of alkyl groups. Further, R1 and R2 are each independently selected from C1. 1-3 Alkyl, -C 1-3 Alkyl-C(=O)-OC 1-3 Alkyl group, with at least one R a Replacement C 1-3 Alkyl group, with at least one R a Replacement -C 1-3 Alkyl-C(=O)-OC 1-3 Alkyl-; R a Contains cyano, halogen and C 1-3 At least one of the alkyl groups.

[0042] Furthermore, the R a It is selected from any one of -CN, -F, -CH3, -CH2CH3, -CH2CH2CH3 and -CH(CH3)CH3.

[0043] According to some embodiments of the present invention, the structural formula of the potassium nitrile phenyl trifluoroborate compound is selected from...

[0044] At least one of Equations 1-1 to 1-6, wherein Equations 1-1 to 1-6 are:

[0045]

[0046] According to some embodiments of the present invention, the amount of potassium nitrile phenyl trifluoroborate compound added accounts for 0.05 to 1 wt.% of the total mass of the electrolyte. In the electrolyte, a suitable content of potassium nitrile phenyl trifluoroborate compound can achieve coordination protection of oxygen at the positive electrode and protection of interfacial film formation. If the content of potassium nitrile phenyl trifluoroborate compound is too low, its protective effect is insufficient, while if the content is too high, it may become insoluble. Undissolved particulate foreign matter may cause the battery separator to rupture, leading to abnormal problems such as short circuits.

[0047] According to some embodiments of the present invention, the electrolyte further includes a fluorinated compound, said fluorinated compound including at least one selected from fluoroethylene carbonate (FEC), methyl trifluoroethyl carbonate (FEMC), diethyl fluorocarbonate (FDEC), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), ethyl 2,2,2-trifluoroacetate (FEA), ethyl 2,2-difluoroacetate, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE).

[0048] According to some embodiments of the present invention, the amount of the fluorinated compound added accounts for 5 to 20 wt% of the total mass of the electrolyte, exemplarily 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, or any range of values ​​formed by any pair of the aforementioned values ​​and any point within the range.

[0049] According to some embodiments of the present invention, the electrolyte further includes a sulfonic acid additive, wherein the sulfonic acid additive includes at least one selected from 1,3-propanesulfonyl lactone, 1-propene-1,3-sulfonyl lactone, 5-methyloxathiapentane 2,2-dioxide, 1,3-propenesulfonyl lactone, 2,4-butanesulfonyl lactone, and 1,4-butanesulfonyl lactone. In this invention, adding sulfonic acid additives to the electrolyte helps in film formation at the negative electrode, thereby significantly affecting gas generation on the negative electrode surface. During high-temperature storage, residual sulfonic acid additives in the electrolyte can also effectively suppress gas generation. Overall, the sulfonic acid additives effectively promote film formation at the negative electrode and reduce gas generation during battery cycling and storage.

[0050] Further, the sulfonic acid additive has a mass percentage content of 0–10 wt% in the electrolyte. Exemplary examples include 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt%, or any range of values ​​formed by any pair of the aforementioned values ​​and any point within that range. Preferably, the sulfonic acid additive has a mass percentage content of 0–5 wt% in the electrolyte.

[0051] According to some embodiments of the present invention, the solvent comprises carbonates and / or carboxylic esters; the carbonates comprise at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; the carboxylic esters comprise at least one of propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0052] According to some embodiments of the present invention, the electrolyte salt includes at least one selected from lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(oxalate) phosphate, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(trifluoromethanesulfonyl)imide, lithium di(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethanesulfonyl)methyl, and lithium di(trifluoromethanesulfonyl)imide.

[0053] Further, the mass percentage of the electrolyte salt in the electrolyte is 10wt% to 20wt%. Examples include 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, and 20wt%, or any range of values ​​formed by any pair of the aforementioned values ​​and any point within that range.

[0054] According to some embodiments of the present invention, the electrolyte further includes nitrile compounds; the nitrile compounds include at least one selected from adiponitrile, butadionitrile, and 1,3,6-hexanetrionitrile. Nitrile compounds are a class of organic compounds containing a cyano group in their molecular structure. Due to the high bond energy of the carbon-nitrogen triple bond in the cyano group, they are not easily oxidized. Therefore, nitrile compounds exhibit excellent stability and strong oxidation resistance at the positive electrode. Simultaneously, the cyano group has a strong coordinating ability, which can bind to active sites on the electrode surface, masking these active ions and reducing the decomposition of the electrolyte by the electrode. At the positive electrode, they are stable on their own and can complex with some active ions; therefore, nitrile compounds can enhance the electrolyte's resistance to oxidation at the positive electrode, thereby improving the cycle life of the battery under high voltage.

[0055] Stepwise, the nitrile additive has a mass percentage content of 0-8 wt% in the electrolyte. Examples include 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, and 8 wt%, or any range of values ​​formed by any pair of the aforementioned values ​​and any point within that range.

[0056] Secondly, the present invention provides a battery comprising: an electrolyte as described above; a positive electrode containing a positive active material; a negative electrode containing a negative active material; and a separator.

[0057] According to other embodiments of the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer coated on one or both surfaces of the positive current collector, wherein the positive active material layer includes a positive active material, a conductive agent, and a binder. Further, the mass percentage of each component in the positive active material layer is: 80 wt% to 99.8 wt% of the positive active material, 0.1 wt% to 10 wt% of the conductive agent, and 0.1 wt% to 10 wt% of the binder. Preferably, the mass percentage of each component in the positive active material layer is: 90 wt% to 99.6 wt% of the positive active material, 0.2 wt% to 5 wt% of the conductive agent, and 0.2 wt% to 5 wt% of the binder.

[0058] According to other embodiments of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. Further, the mass percentage of each component in the negative electrode active material layer is: 80 wt% to 99.8 wt% of the negative electrode active material, 0.1 wt% to 10 wt% of the conductive agent, and 0.1 wt% to 10 wt% of the binder. Preferably, the mass percentage of each component in the negative electrode active material layer is: 90 wt% to 99.6 wt% of the negative electrode active material, 0.2 wt% to 5 wt% of the conductive agent, and 0.2 wt% to 5 wt% of the binder.

[0059] According to other embodiments of the present invention, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0060] According to other embodiments of the present invention, the adhesive is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0061] According to other embodiments of the present invention, the positive electrode active material is selected from one or more of transition metal lithium oxides, lithium iron phosphate, and lithium-rich manganese-based materials; the chemical formula of the transition metal lithium oxide is Li. 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0062] According to other embodiments of the present invention, the negative electrode active material includes at least one of a carbon-based negative electrode material and a silicon-based negative electrode material. Further, the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon. The silicon-based negative electrode material is selected from at least one of nano-silicon, silicon oxide negative electrode material (SiOx, 0 < x < 2), or silicon-carbon negative electrode material. Specifically, in the negative electrode active material, the mass ratio of the carbon-based negative electrode material to the silicon-based negative electrode material is (10:0) to (1:19).

[0063] The following further illustrates the present invention through some specific embodiments.

[0064] Example 1

[0065] 1.1 The electrolyte includes the following components:

[0066] Organic solvents: ethylene carbonate (EC) 7wt%, propylene carbonate (PC) 14wt%, diethyl carbonate (DEC) 28wt%, propyl propionate (PP) 25.45wt%, totaling 74.45wt%;

[0067] Electrolyte salt: lithium hexafluorophosphate (LiPF6), 12wt%;

[0068] Fluorinated compound: fluoroethylene carbonate, 12wt%;

[0069] Potassium nitrile phenyltrifluoroborate compound: with the structural formula shown in Formula 1-1, 0.05wt%;

[0070] Nitrile compound: adiponitrile, 1.5wt%.

[0071] 1.2 Preparation method: In a glove box filled with argon (H2O < 0.1 ppm, O2 < 0.1 ppm), first add and mix the organic solvents according to the ratio. After mixing evenly, quickly add 1 mol / L of fully dried lithium hexafluorophosphate (LiPF6) and mix well and shake. After shaking, add fluoroethylene carbonate, the potassium nitrile phenyltrifluoroborate compound shown in Formula 1-1, and the nitrile compound, and stir evenly to obtain the required electrolyte.

[0072] Example 2

[0073] 1.1 The electrolyte includes the following components:

[0074] The difference from the components in Example 1 is that: the addition amount of the potassium nitrile phenyltrifluoroborate compound shown in Formula 1-1 is 0.2wt%; propyl propionate (PP) 25.3wt%.

[0075] 1.2 Preparation method: The same as the preparation method in Example 1.

[0076] Example 3

[0077] 1.1 The electrolyte contains the following components:

[0078] The difference from the components in Example 1 is that the amount of potassium nitrile phenyl trifluoroborate compound as shown in Formula 1-1 is 0.4 wt%; and propyl propionate (PP) is 25.1 wt%.

[0079] 1.2 Preparation method: Same as the preparation method in Example 1.

[0080] Example 4

[0081] 1.1 The electrolyte contains the following components:

[0082] The difference from the components in Example 1 is that the amount of potassium nitrile phenyl trifluoroborate compound as shown in Formula 1-1 is 0.8 wt%; and propyl propionate (PP) is 24.7 wt%.

[0083] 1.2 Preparation method: Same as the preparation method in Example 1.

[0084] Example 5

[0085] 1.1 The electrolyte contains the following components:

[0086] The difference from the components in Example 1 is that the amount of potassium nitrile phenyl trifluoroborate compound as shown in Formula 1-1 is 1.0 wt%; and propyl propionate (PP) is 24.5 wt%.

[0087] 1.2 Preparation method: Same as the preparation method in Example 1.

[0088] Example 6

[0089] 1.1 The electrolyte contains the following components:

[0090] The difference from the components in Example 1 is that: the structural formula of the potassium nitrile phenyl trifluoroborate compound is shown in Formulas 1-3, and its addition amount is 0.2 wt%; propyl propionate (PP) 25.3 wt%.

[0091] 1.2 Preparation method: Same as the preparation method in Example 1.

[0092] Example 7

[0093] 1.1 The electrolyte contains the following components:

[0094] The difference from the components in Example 1 is that: the structural formula of the potassium nitrile phenyl trifluoroborate compound is shown in Formulas 1-3, and its addition amount is 1.0 wt%; propyl propionate (PP) 24.5 wt%.

[0095] 1.2 Preparation method: Same as the preparation method in Example 1.

[0096] Example 8

[0097] 1.1 The electrolyte contains the following components:

[0098] The difference from the components in Example 1 is the addition of two potassium nitrile phenyl trifluoroborate compounds with different structures: as shown in Formula 1-1, the amount added is 0.5 wt%; as shown in Formula 1-3, the amount added is 0.5 wt%; and propyl propionate (PP) 24.5 wt%.

[0099] 1.2 Preparation method: Same as the preparation method in Example 1.

[0100] Example 9

[0101] 1.1 The electrolyte contains the following components:

[0102] Organic solvents: 7 wt% ethylene carbonate (EC), 14 wt% propylene carbonate (PC), 28 wt% diethyl carbonate (DEC), 22.6 wt% propyl propionate (PP), totaling 71.6 wt%;

[0103] Electrolyte salt: Lithium hexafluorophosphate (LiPF6), 12 wt%;

[0104] Fluorinated compound: fluoroethylene carbonate, 12 wt%;

[0105] Potassium nitrile phenyl trifluoroborate compounds: structural formula as shown in Formula 1-1, 0.4 wt%;

[0106] Sulfonic acid additives: 1,3-propanesulfonyl lactone, 2 wt%;

[0107] Nitrile compounds: 1,3,6-hexanetrionitrile 2wt%.

[0108] 1.2 Preparation method: In a glove box filled with argon (H2O<0.1ppm, O2<0.1ppm), the organic solvent is first added and mixed according to the ratio. After mixing evenly, 1 mol / L of fully dried lithium hexafluorophosphate (LiPF6) is quickly added and mixed thoroughly and shaken. After shaking evenly, fluoroethylene carbonate, 1,3-propanesulfonyl lactone, 1,3,6-hexanetrionitrile and potassium nitrile phenyl trifluoroborate compound as shown in Formula 1-1 are added. After stirring evenly, the desired electrolyte is obtained.

[0109] Example 10

[0110] 1.1 The electrolyte contains the following components:

[0111] Organic solvents: 7 wt% ethylene carbonate (EC), 14 wt% propylene carbonate (PC), 28 wt% diethyl carbonate (DEC), 21.1 wt% propyl propionate (PP), totaling 70.1 wt%;

[0112] Electrolyte salt: Lithium hexafluorophosphate (LiPF6), 12 wt%;

[0113] Fluorinated compound: fluoroethylene carbonate, 12 wt%;

[0114] Potassium nitrile phenyl trifluoroborate compounds: structural formula as shown in Formula 1-1, 0.4 wt%;

[0115] Sulfonic acid additives: 1,3-propanesulfonyl lactone, 2 wt%;

[0116] Nitrile compounds: adiponitrile 1.5 wt%; 1,3,6-hexanetrionitrile 2 wt%.

[0117] 1.2 Preparation method: In a glove box filled with argon (H2O<0.1ppm, O2<0.1ppm), the organic solvent is first added and mixed according to the ratio. After mixing evenly, 1 mol / L of fully dried lithium hexafluorophosphate (LiPF6) is quickly added and mixed thoroughly and shaken. After shaking evenly, fluoroethylene carbonate, 1,3-propanesulfonyl lactone, 1,3,6-hexanetrionitrile and potassium nitrile phenyl trifluoroborate compound as shown in Formula 1-1 are added. After stirring evenly, the desired electrolyte is obtained.

[0118] Example 11

[0119] 1.1 The electrolyte contains the following components:

[0120] The difference from the components in Example 9 is that the structural formula of the potassium nitrile phenyl trifluoroborate compound is shown in Formulas 1-2.

[0121] 1.2 Preparation method: Same as the preparation method in Example 9.

[0122] Example 12

[0123] 1.1 The electrolyte contains the following components:

[0124] The difference from the components in Example 9 is that the structural formula of the potassium nitrile phenyl trifluoroborate compound is shown in Formulas 1-5.

[0125] 1.2 Preparation method: Same as the preparation method in Example 9.

[0126] Example 13

[0127] 1.1 The electrolyte contains the following components:

[0128] The difference from the components in Example 9 is that the sulfonic acid additive is replaced with 1-propylene-1,3-sulfonyl lactone.

[0129] 1.2 Preparation method: Same as the preparation method in Example 9.

[0130] Comparative Example 1

[0131] 1.1 The electrolyte contains the following components:

[0132] The difference from the components in Example 1 is that the amount of potassium nitrile phenyl trifluoroborate compound added is 0 wt%.

[0133] 1.2 Preparation method: The preparation method is the same as that in Example 1, except that potassium nitrile phenyl trifluoroborate compound is not added.

[0134] Preparation of lithium-ion batteries

[0135] 1) Preparation of positive electrode sheet

[0136] Lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), super P (SP), and carbon nanotubes (CNT) were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until it formed a uniform and fluid positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an aluminum foil. The coated aluminum foil was dried, and then rolled and slit to obtain the desired positive electrode sheet.

[0137] 2) Preparation of negative electrode sheet

[0138] Artificial graphite, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP), and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 96:1.5:1.5:0.95:0.05, and deionized water was added. The mixture was stirred in a vacuum mixer to obtain a negative electrode active slurry. The negative electrode active slurry was uniformly coated on both surfaces of a copper foil. The coated copper foil was dried at room temperature and then transferred to an 80°C oven for 10 hours. After cold pressing and slitting, the negative electrode sheet was obtained.

[0139] 3) The positive electrode sheet, negative electrode sheet, and separator prepared above are stacked in the order of positive electrode sheet, separator sheet, and negative electrode sheet, and then wound to obtain a battery cell. The battery cell is placed in an outer packaging aluminum foil, and the electrolyte prepared in the examples and comparative examples is injected into the outer packaging respectively. After vacuum sealing, standing, formation, shaping, and sorting processes, different lithium-ion batteries are obtained. The charge / discharge range of the battery of this invention is 3.0-4.55V.

[0140] The types and amounts of potassium nitrile phenyl trifluoroborate compounds used in the examples and comparative examples are shown in Table 1.

[0141] Table 1

[0142]

[0143] Performance testing

[0144] The prepared lithium-ion batteries were subjected to 45℃ intermittent cycle performance tests and high-temperature storage tests, and the test results are shown in Table 2.

[0145] (1) 45℃ intermittent cycle performance test

[0146] The prepared lithium-ion battery was charged and discharged at 45°C at a rate of 1C within the charge-discharge cutoff voltage range. The charging cutoff voltage was 4.5V, and the cutoff current was 0.05C. After each charge, the battery was left to rest at 45°C for 22 hours, and then discharged again at a discharge cutoff voltage of 3V. The discharge capacity of the first week was measured as x mAh, and the discharge capacity of the Nth week was measured as y mAh. The capacity of the Nth week was divided by the capacity of the first week to obtain the cycle capacity retention rate R = y / x. The cycle number corresponding to a cycle capacity retention rate R of 70% was recorded.

[0147] (2) Storage performance test at 60℃

[0148] The prepared lithium-ion battery was charged at 25℃ at a rate of 1C to the cutoff voltage, with a cutoff current of 0.025C. After standing for 5 minutes, the thickness of the lithium-ion battery was measured (this thickness was taken as the thickness before storage). The fully charged cell / battery was left open-circuit at (60±2)℃ for 35 days. After 35 days of storage, it was left open-circuit at room temperature for 2 hours, and the thickness after storage was measured. The thickness expansion rate of the lithium-ion battery was calculated.

[0149] Thickness expansion rate = [(thickness after storage - thickness before storage) / thickness before storage] × 100%.

[0150] Table 2

[0151]

[0152] As can be seen from the data in Examples 1 to 7 in Table 2, the battery exhibits the best intermittent cycle performance and high-temperature storage performance when the amount of potassium nitrile phenyl trifluoroborate compound added is 1.0 wt.%, showing a significant improvement in performance compared to Comparative Example 1, which did not contain potassium nitrile phenyl trifluoroborate compound. Furthermore, the intermittent cycle performance and high-temperature storage performance of the battery can also be improved by adding sulfonic acid additives or appropriately increasing the amount and type of nitrile compounds.

[0153] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0154] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A battery, characterized in that, The battery includes: Electrolyte and positive electrode sheet containing positive electrode active material, the positive electrode active material being lithium cobalt oxide; The electrolyte includes: electrolyte salt, solvent, and potassium nitrile phenyl trifluoroborate compound; The structural formula of the potassium trifluoroborate nitrile phenyl trifluoroborate compound is selected from at least one of formulas 1-2 to 1-6, where formulas 1-2 to 1-6 are: ； The electrolyte also includes: Nitrile compounds, said nitrile compounds including at least one selected from adiponitrile and 1,3,6-hexanetrionitrile; Fluorinated compounds, including fluoroethylene carbonate; The amount of the potassium nitrile phenyl trifluoroborate compound added is 0.05~1 wt.% of the total mass of the electrolyte. The amount of the fluorinated compound added is 5-20 wt.% of the total mass of the electrolyte. The electrolyte further includes: sulfonic acid additives, wherein the sulfonic acid additives include at least one of 1,3-propanesulfonyl lactone, 1-propene-1,3-sulfonyl lactone, 5-methyloxathiapentane 2,2-dioxide, 1,3-propenesulfonyl lactone, 2,4-butanesulfonyl lactone, and 1,4-butanesulfonyl lactone. The sulfonic acid additive has a mass percentage of 0.5-10 wt% in the electrolyte. The nitrile compound has a mass percentage of 0.5 to 8 wt% in the electrolyte.

2. The battery according to claim 1, characterized in that, The fluorinated compound includes at least one selected from methyl trifluoroethyl carbonate, diethyl fluorocarbonate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, ethyl 2,2,2-trifluoroethyl ether, ethyl 2,2-difluoroethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

3. The battery according to claim 1, characterized in that, The solvent includes carbonates and / or carboxylic esters; The carbonate includes at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; the carboxylic acid ester includes at least one selected from propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate, ethyl propionate, methyl butyrate, and n-ethyl butyrate; and / or The electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalate) phosphate, lithium tetrafluoroborate, lithium bis(oxalate) borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(trifluoromethylsulfonyl)imide, lithium di(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethylsulfonyl)methyl, and lithium di(trifluoromethylsulfonyl)imide.

4. The battery according to claim 1, characterized in that, The nitrile compounds include succinic anionyl nitrile.

5. The battery according to claim 1, characterized in that, The battery also includes: Anode sheet and separator containing negative electrode active material.

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