Electrolyte additive, electrolyte, and secondary battery

Abstract

The application relates to the technical field of secondary batteries, and provides an electrolyte additive, an electrolyte and a secondary battery. The electrolyte additive comprises a compound I: I, wherein A1 is a sulfone group-containing organic group with 2-20 carbon atoms, X1 and X2 are independently one of hydrogen, methyl and a methylene-containing organic group with 2-5 carbon atoms. The electrolyte additive provided by the application can form a stable solid electrolyte interface film on the electrode surface, inhibit the interface side reaction, improve the stability under high voltage, and thus improve the high-voltage cycle performance and high-temperature storage performance of the lithium secondary battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary batteries, and more particularly relates to an electrolyte additive, an electrolyte and a secondary battery. BACKGROUND

[0002] Spinel lithium nickel manganese oxide (LNMO) cathode material has a high working voltage of 4.75V and a high theoretical specific capacity of 146.7mAh / g, does not contain Co in the material composition, has a relatively simple preparation process, low cost and high safety, and thus has become the most potential generation of commercial high-energy-density lithium-ion battery cathode material. However, the spinel lithium nickel manganese oxide cathode material currently still has some deficiencies, for example: the strong oxidizing Ni 4+ The catalytic electrolyte is oxidized and decomposed, and the PF5 produced by the decomposition of LiPF6 of the electrolyte under high potential and high temperature conditions reacts with trace water in the electrolyte system to generate HF, which accelerates the dissolution of Mn 2+ in the structure of spinel lithium nickel manganese oxide, thereby causing the structure to be unstable, and the dissolved Mn 2+ is reduced at the negative electrode, resulting in capacity attenuation during the electrolytic cycle.

[0003] In order to overcome the defects of the spinel lithium nickel manganese oxide and other similar cathode materials with high-valence metal ions, an additive is usually added to the electrolyte, a stable solid electrolyte interface film is constructed on the surface of the lithium nickel manganese oxide by the additive, so as to avoid the oxidation between the electrode and the electrolyte and the corrosion of HF to the electrode, and the additive can also eliminate many impurities in the battery system and reduce the adverse effects of the impurities on the battery cycle.

[0004] However, the electrolyte additive in the prior art cannot maintain the stability of the electrolyte under high pressure conditions, and the main performance is that the capacity retention rate of the battery decreases seriously after multiple cycles under high pressure conditions. In order to solve this technical problem, it is necessary to consider improving the high-voltage resistance of the interface film.

[0005] In view of the problems in the above related technologies, how to provide an additive to improve the high-pressure stability of the electrolyte film formed by the additive, and at the same time make the high-voltage lithium secondary battery with the electrolyte have good high-voltage cycle performance has become a technical problem to be solved at present. SUMMARY

[0006] The purpose of the embodiments of the present application is to provide an electrolyte additive. Through the electrolyte additive, a more stable electrolyte film can be formed on the surface of the electrode of the secondary battery, which effectively blocks the direct contact between the electrode and the electrolyte. At the same time, the film has better high-pressure stability, and to some extent, the problem of poor high-pressure stability of the electrolyte film on the surface of the electrode is solved.

[0007] To achieve the above object, in a first aspect of the present application, an electrolyte additive is provided, which comprises a compound I, the general formula of the compound I being as follows:

[0008]

[0009] wherein A1 is a sulfone group-containing organic group having 2-20 carbon atoms.

[0010] In some embodiments, X1 and X2 are independently one of hydrogen, methyl, and a methylene group-containing organic group having 2-5 carbon atoms.

[0011] In some embodiments, the compound I comprises at least one of:

[0012] diprop-2-ynyl sulfone, CAS No. 14039-88-4

[0013] 1,1'-sulfonylbis(4-ethynylbenzene), CAS No. 27594-30-5

[0014] In a second aspect of the present application, an electrolyte is provided. The electrolyte of the present application comprises a non-aqueous organic solvent, and an additive and a lithium salt dissolved in the non-aqueous organic solvent, the additive comprising the electrolyte additive of the present application.

[0015] In some embodiments, the mass percentage content of the electrolyte additive in the electrolyte is 0.05-2%.

[0016] In some embodiments, the molar concentration of the lithium salt is 0.8-1.5 mol / L.

[0017] In some embodiments, the non-aqueous organic solvent comprises a fluorinated organic solvent.

[0018] In some embodiments, the fluorinated organic solvent comprises at least one of a fluorinated carbonate, a fluorinated carboxylate, and a fluorinated ether.

[0019] In some embodiments, the non-aqueous organic solvent comprises at least one of vinyl carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone.

[0020] In some embodiments, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium bis(fluoro oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluoro sulfonyl)imide.

[0021] ​In the above embodiments, the electrolyte uses

[0022] In a third aspect, the present application provides a secondary battery. The secondary battery of the present application comprises a positive electrode, a negative electrode, a separator and the electrolyte of the present application.

[0023] In some embodiments, the positive electrode contains a positive electrode material comprising at least one of spinel lithium nickel manganese oxide and lithium-rich manganese material.

[0024] In some embodiments, the negative electrode contains a negative electrode material comprising one of lithium, graphite, Si-containing composite material and lithium titanate.

[0025] In some embodiments, the separator comprises one of single-layer polyethylene, single-layer polypropylene, double-layer polyethylene / polypropylene separator, three-layer polypropylene separator, inorganic coating modified separator and polymer coating modified separator, wherein the three-layer polypropylene separator is a polyethylene / polypropylene / polyethylene three-layer separator.

[0026] In some embodiments, the positive electrode comprises spinel lithium nickel manganese oxide and lithium-rich manganese material, and the mass ratio of spinel lithium nickel manganese oxide to lithium-rich manganese material is (70-99):(1-30).

[0027] In some embodiments, the molecular formula of the spinel lithium nickel manganese oxide is LiNi 0.5-x Mn 1.5 M x O 4-y F y , LiNi 0.5 Mn 1.5- x M x O 4-y F y or LiNi 0.5-x / 2 Mn 1.5-x / 2 M x O 4-y F y , 0≤x≤0.08, 0≤y≤0.1.

[0028] In some embodiments, the molecular formula of the lithium-rich manganese material is zLiMnO2·(1-z)Li2MO3, wherein 0.1≤z≤0.7, and M comprises one of Ni, Mn and Co. The corresponding secondary battery has a charge cut-off voltage of 4.5-5V.

[0029] Compared with the prior art, the present application has the following technical effects:

[0030] The electrolyte additive has two carbon-carbon triple bond structures. The carbon-carbon triple bond as a strong ligand is more easily combined with high-valence metal ions on the surface of the battery electrode and other strong oxidizing structures. The carbon-carbon triple bond structure has stronger reducibility and is more easily oxidized at the initial stage of electrochemical reaction, and thus is preferentially deposited on the electrode surface. The electrolyte film obtained after deposition has high stability, and can effectively maintain the stability of the film structure under high temperature conditions. The A1 group in the additive contains a sulfone group, which is located between the two carbon-carbon triple bonds. When the two carbon-carbon triple bonds are combined with the active sites on the electrode surface, the sulfone group is located on the side away from the electrode surface due to the steric hindrance effect. At this time, the sulfone group can be used to coordinate with lithium ions to form a cluster structure, which has a good promoting effect on the formation of a stable solid electrolyte interface film. At the same time, the cluster structure is not easily damaged even under high voltage due to the support of the two end triple bonds, thereby effectively improving the high-voltage stability of the formed solid electrolyte film.

[0031] The electrolyte of the application includes an electrolyte additive with two carbon-carbon triple bonds. After the additive forms a solid electrolyte film through electrochemical reaction, the electrode and the electrolyte can be effectively isolated, and the electrolyte film has good high-voltage stability. The lithium ion solvent component in the electrolyte can be effectively isolated to avoid co-intercalation into the electrode to cause consumption. At the same time, the corresponding electrolyte can effectively avoid the oxidation and decomposition of other effective components in the electrolyte by high-valence metal ions on the electrode surface, thereby improving the high-temperature stability of the electrolyte.

[0032] The secondary battery of the application includes an electrolyte with an electrolyte additive having two carbon-carbon triple bonds. The carbon-carbon triple bond in the electrolyte additive has stronger reactivity than other components in the electrolyte, and can preferentially react with active sites on the electrode surface to form an electrolyte film, thereby inhibiting the oxidation and decomposition of other components in the electrolyte by high-valence metal ions to some extent. The group connected to the carbon-carbon triple bond can be optimized to improve the morphology of the film after film formation, so that it has relatively lower impedance. The A1 group can trap the lithium ion solvent component to prevent it from directly contacting the electrode under high voltage conditions to cause irreversible electrochemical reaction. At the same time, the corresponding film formed has good high-temperature stability, can maintain good stability under high-temperature storage and cycling conditions, and is beneficial to improving the high-temperature storage performance and cycling performance of the secondary battery, thereby improving the storage performance and cycling performance of the secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0034] Figure 1 Charge-discharge curves of the secondary battery of Example B1 at different cycle periods.

[0035] Figure 2 Cycle retention rate graph of the secondary battery of Example B1.

[0036] Figure 3 LSV curves of the electrolyte of Example B1, Example B2 and Comparative Example B1.

[0037] Figure 4 Charge-discharge curves of the secondary battery of Example B1 and Example B8. DETAILED DESCRIPTION

[0038] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not intended to limit the present application.

[0039] It should be noted that in the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the following three cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0040] It should be understood that "at least one" in the present application means one or more, and "multiple" means two or more than two.

[0041] It should be understood that in various embodiments of the present application, the size of the serial number of each process does not mean the execution order, and part or all of the steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0042] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0043] The weight of the related components mentioned in the embodiment specification of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component. Therefore, as long as the content of the related components in the embodiment specification of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the embodiment specification of the present application. Specifically, the mass in the embodiment specification of the present application can be μg, mg, g, kg, etc. mass units commonly known in the chemical industry.

[0044] The first aspect of the embodiment of the present application provides an electrolyte additive, which comprises compound I, and the structural general formula of compound I is as follows:

[0045]

[0046] In compound I, A1 is a sulfone-containing organic group with 2-20 carbon atoms, and X1 and X2 are independently one of hydrogen, methyl, and a methylene-containing organic group with 2-5 carbon atoms.

[0047] The electrolyte additive of the above embodiment comprises compound I, which has at least two carbon-carbon triple bonds in its molecular structure. The carbon-carbon triple bond structure as a strong ligand has stronger stability after reaction to form a film. Therefore, compared with a conventional electrolyte film, the electrolyte film structure formed by the electrolyte additive of the present application can withstand higher temperatures and maintain long-term stability in a high-temperature environment, effectively preventing direct contact reaction between the electrode and the electrolyte. When A1, X1 and X2 are selected as specific groups, the reactivity of compound I molecules on the electrode surface will be affected. During the first charging process, the compound I structure can preferentially form a stable electrolyte film on the electrode surface, improving the stability of the lithium secondary battery. Under the effect of steric hindrance, the sulfone group will move away from the carbon-carbon triple bond, that is, the sulfone group will move away from the electrode surface. As a good ligand for lithium ions, the sulfone group can form a cluster structure with solvent molecules and lithium hexafluorophosphate. The ionic state of hexafluorophosphate and lithium ions is wrapped inside the cluster structure, thereby effectively preventing the direct contact of lithium hexafluorophosphate with the electrode to produce an oxidation-reduction reaction, and effectively reducing the consumption of lithium hexafluorophosphate. Secondly, as a strong ligand, the carbon-carbon triple bond is easily complexed with high-valent metal ions in the positive electrode material, thereby consuming the active reaction sites on the surface of the positive electrode material. Two carbon-carbon triple bonds form a support structure, making the cluster structure formed by the A1 group and the solvent molecules more stable, inhibiting the oxidative decomposition of the electrolyte by the positive electrode, and improving the cycle performance of the lithium ion battery.

[0048] In some embodiments, A1 is a sulfone-containing alkyl group with 2-20 carbon atoms. In an exemplary embodiment, it can be a dimethyl sulfone group.

[0049] In some embodiments, A1 is a phenyl ring substituted with a sulfone-containing substituent having a carbon number of 2-20. In exemplary embodiments, it can be a diphenyl sulfone group.

[0050] In the above embodiments, the spatial structure of the A1 group is kept at a relatively appropriate size, so it has good reactivity with both the positive and negative electrodes, which is conducive to the formation of a low-impedance film on the surface of the electrode. At the same time, the preferred A1 group can maintain good stability when the film is in a high-temperature condition due to its own double carbon-carbon triple bond structure, avoiding the dissolution of the film at high temperature and the consumption of the electrode active material, thereby improving the high-temperature and power characteristics of the lithium ion battery, inhibiting the oxidative decomposition of the electrolyte at the positive electrode, and improving the high-temperature storage performance of the lithium ion battery.

[0051] In some embodiments, the compound I can include at least one of the following specific compounds:

[0052] Diprop-2-ynyl sulfone, CAS No.: 14039-88-4 The preparation process can refer to: https: / / baike.molbase.cn / cidian / 17511533_xianlu_6319377 / , and

[0053] 1,1'-sulfonyl bis(4-ethynylbenzene), CAS No.: 27594-30-5 one of the following.

[0054] The compound I provided in the above embodiments as an additive for the electrolyte of the lithium ion battery has more excellent technical effects in improving the high-voltage cycle performance, high-temperature storage performance, and high-temperature cycle performance of the lithium ion battery.

[0055] The second aspect of the embodiments of the present application provides an electrolyte, which includes an additive, a non-aqueous organic solvent, and a lithium salt, the additive includes the compound I, and the additive and the lithium salt are dissolved in the non-aqueous organic solvent to form the electrolyte.

[0056] The electrolyte provided by the above embodiments adopts an electrolyte additive including compound I, compound I has at least two carbon-carbon triple bonds, the two carbon-carbon triple bonds are located at two ends of the A1 group, and the X1 group and the X2 group are located at the ends of the two carbon-carbon triple bonds, respectively. By selecting specific A1 groups, X1 groups and X2 groups, the overall electron cloud distribution of compound I will be directly affected, thereby changing the electronic effect and causing the reaction activity on the electrode surface to change. At the same time, the selection of the A1 group will directly affect the film-forming performance of the additive on the electrode surface and the impedance effect brought by the film after forming. When the steric hindrance of the A1 group is too small, the film-forming effect is improved, and the impedance of the protective film formed is increased, which is not conducive to the improvement of the battery performance. When the steric hindance of the A1 group is too large, the film-forming effect is poor, and the impedance of the protective film formed is reduced. The selection of the above A1 group can simultaneously bring relatively better film-forming performance and impedance performance. The A1 group can also cooperate with the two carbon-carbon triple bonds. By using reasonable steric hindance effect and the coordination of the A1 group with the solvents and lithium hexafluorophosphate in the electrolyte, the cycle stability and capacity retention rate of the battery under high voltage conditions can be effectively improved. The principle of the analysis may be that under the support of the steric hindance effect, the effective components such as lithium hexafluorophosphate can effectively resist high voltage and avoid direct contact with the electrode to occur electrochemical reaction.

[0057] In some embodiments, the mass percentage content of the electrolyte additive is 0.05-2%. If the percentage content of the electrolyte additive is less than 0.05%, a stable protective film cannot be formed on the electrode surface, and the technical effects of "inhibiting the side reaction of the electrode and the electrolyte, reducing the interface impedance, and comprehensively improving the output performance of the battery" cannot be achieved. If the mass percentage content of the electrolyte additive is higher than 2%, after the electrolyte additive forms a protective film on the electrode surface, the polarization of the battery increases, which deteriorates the battery performance.

[0058] In some embodiments, the non-aqueous organic solvent includes a fluorinated organic solvent. In an exemplary embodiment, the fluorinated organic solvent includes at least one of a fluorinated carbonate, a fluorinated carboxylate, and a fluorinated ether. The addition of the fluorinated organic solvent can form a solid electrolyte of LiF on the electrode surface, which helps to form a stable protective film, effectively inhibits the formation of lithium dendrites, and also improves the oxidation stability of the electrolyte, the adaptability of the high-voltage positive electrode, and the cycle stability of the lithium secondary battery.

[0059] In some embodiments, the non-aqueous organic solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone.

[0060] With these non-aqueous organic solvents, the stability of water to the positive electrode material of the lithium ion battery can cause an impact, which is specifically manifested as smaller battery capacity, shorter discharge time, increased internal resistance, cyclic capacity attenuation, battery expansion, etc. Therefore, the use of non-aqueous organic solvents can effectively avoid the addition of water and improve the comprehensive performance of the lithium ion secondary battery.

[0061] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium bis(fluoro oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0062] The third aspect of the embodiments of the present application provides a secondary battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte including the compound I in the above-mentioned solution.

[0063] In some embodiments, the positive electrode material contained in the positive electrode includes at least one of spinel lithium nickel manganese oxide and lithium-rich manganese material. The spinel lithium nickel manganese oxide and the lithium-rich manganese material have a higher working voltage, and thus, these two positive electrode materials are relatively optimal choices for high theoretical specific capacity.

[0064] In some embodiments, the positive electrode material contained in the positive electrode includes spinel lithium nickel manganese oxide and lithium-rich manganese material, and the mass ratio of the spinel lithium nickel manganese oxide to the lithium-rich manganese material is (70-99):(1-30). In an exemplary embodiment, the molecular formula of the spinel lithium nickel manganese oxide is LiNi 0.5-x Mn 1.5 M x O 4-y F y , LiNi 0.5 Mn 1.5-x M x O 4-y F y or LiNi 0.5-x / 2 Mn 1.5-x / 2 M x O 4-y F y , 0≤x≤0.08, 0≤y≤0.1. The molecular formula of the lithium-rich manganese material is zLiMnO2·(1-z)Li2MO3, where 0.1≤z≤0.7, and M includes one of Ni, Mn, and Co.

[0065] The spinel lithium nickel manganese oxide (LNMO) has a stable material structure, a high voltage platform, a high specific energy density, and good cycle performance. It obtains the characteristics of high working voltage by replacing one-fourth of the Mn elements with Ni. This high voltage characteristic can meet the demand for high specific energy density and high specific power density of lithium batteries, and the partially replaced Co can further stabilize the structure. However, the market price of Co is relatively high, and thus, a small amount of Co ions can be doped.

[0066] The specific capacity of the lithium-rich manganese material is relatively high and the cost is low, but the structure is unstable during the cycle process and the voltage platform attenuates, causing irreversible loss of capacity. In the present application, a film can be formed on the electrode surface under the condition of using an improved electrolyte additive, which effectively prevents the irreversible extraction of lithium ions, thereby serving as a positive electrode material for further improving the specific capacity.

[0067] In some embodiments, the negative electrode contains a negative electrode material including one of lithium, graphite, a Si-containing composite material, and lithium titanate.

[0068] In some embodiments, the separator includes one of a single-layer polyethylene, a single-layer polypropylene, a double-layer polyethylene / polypropylene separator, a three-layer polypropylene separator, an inorganic coating modified separator, and a polymer coating modified separator.

[0069] In order to enable the above-mentioned implementation details and operations of the present application to be clearly understood by those skilled in the art, and the progress of the electrolyte additive, electrolyte and secondary battery of the embodiments of the present application to be significantly embodied, the above technical solutions are described below through multiple embodiments.

[0070] 1. Electrolyte additive and electrolyte embodiments

[0071] Embodiment A1

[0072] The present embodiment provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0073] diprop-2-ynyl sulfone,

[0074] The electrolyte includes lithium hexafluorophosphate, a diprop-2-ynyl sulfone electrolyte additive dissolved in a non-aqueous organic solvent, wherein the concentration of the electrolyte lithium salt is 1 mol / L, and the mass concentration of the diprop-2-ynyl sulfone electrolyte additive is 1%; the non-aqueous organic solvent includes a mixed solvent of fluoroethylene carbonate, fluoroethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0075] Method for configuring the electrolyte:

[0076] Fluoroethylene carbonate, fluoroethyl methyl carbonate and dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a non-aqueous organic solvent. Lithium hexafluorophosphate is added to the non-aqueous organic solvent to make the electrolyte lithium salt concentration 1 mol / L, to obtain a basic electrolyte. Then, diprop-2-ynyl sulfone equivalent to 1% (mass) of the electrolyte is added to the basic electrolyte, to obtain the electrolyte.

[0077] Embodiment A2

[0078] The embodiment provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0079] 1,1'-sulfonylbis(4-ethynylphenyl),

[0080] The electrolyte comprises lithium hexafluorophosphate, 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additives and 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additives dissolved in a non-aqueous organic solvent, wherein the concentration of electrolyte lithium salt is 1 mol / L, the mass concentration of 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additives is 1%, and the non-aqueous organic solvent comprises a mixed solvent of fluoroethylene carbonate, fluoroethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0081] The configuration method of the electrolyte comprises the following steps:

[0082] The fluoroethylene carbonate, the fluoroethyl methyl carbonate and the dimethyl carbonate are mixed according to a mass ratio of 2:1:7 to obtain a non-aqueous organic solvent, lithium hexafluorophosphate is added into the non-aqueous organic solvent to make the concentration of electrolyte lithium salt be 1 mol / L, a basic electrolyte is obtained, and 1,1'-sulfonylbis(4-ethynylphenyl) corresponding to 1% (mass) of the electrolyte is added into the basic electrolyte, to obtain the electrolyte.

[0083] Embodiment A3

[0084] The embodiment provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0085] The electrolyte additive comprises diprop-2-ynyl sulfone, and 1,1'-sulfonylbis(4-ethynylphenyl),

[0086] The electrolyte comprises lithium hexafluorophosphate, diprop-2-ynyl sulfone electrolyte additives and 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additives dissolved in a non-aqueous organic solvent, wherein the concentration of electrolyte lithium salt is 1 mol / L, the mass concentration of 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additives is 0.5%, and the mass concentration of diprop-2-ynyl sulfone electrolyte additives is 0.5%; the non-aqueous organic solvent comprises a mixed solvent of fluoroethylene carbonate, fluoroethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0087] The configuration method of the electrolyte comprises the following steps:

[0088] Fluoroethylene carbonate, difluoroethylene carbonate, and dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a nonaqueous organic solvent, lithium hexafluorophosphate is added to the nonaqueous organic solvent to make the concentration of electrolyte lithium salt 1 mol / L to obtain a base electrolyte, and then diprop-2-ynyl sulfone equivalent to 0.5 (mass) % of the electrolyte and 1,1'-sulfonylbis(4-ethynylbenzene) equivalent to 0.5 (mass) % of the electrolyte are added to the base electrolyte to obtain an electrolyte. and 1,1'-sulfonylbis(4-ethynylbenzene) equivalent to 0.5 (mass) % of the electrolyte, to obtain an electrolyte.

[0089] Example A4

[0090] The present example provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0091] The electrolyte additive includes diprop-2-ynyl sulfone, and 1,1'-sulfonylbis(4-ethynylbenzene),

[0092] The electrolyte includes lithium hexafluorophosphate, diprop-2-ynyl sulfone electrolyte additive, and 1,1'-sulfonylbis(4-ethynylbenzene) electrolyte additive dissolved in a nonaqueous organic solvent, wherein the concentration of electrolyte lithium salt is 1 mol / L, the mass concentration of diprop-2-ynyl sulfone electrolyte additive is 0.5%, and the mass concentration of 1,1'-sulfonylbis(4-ethynylbenzene) electrolyte additive is 0.5%; the nonaqueous organic solvent includes a mixed solvent of fluoroethylene carbonate, difluoroethylene carbonate, and dimethyl carbonate in a mass ratio of 2:1:7.

[0093] Method for configuring the electrolyte:

[0094] Fluoroethylene carbonate, difluoroethylene carbonate, and dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a nonaqueous organic solvent, lithium hexafluorophosphate is added to the nonaqueous organic solvent to make the concentration of electrolyte lithium salt 1 mol / L to obtain a base electrolyte, and then diprop-2-ynyl sulfone equivalent to 0.5 (mass) % of the electrolyte and 1,1'-sulfonylbis(4-ethynylbenzene) equivalent to 0.5 (mass) % of the electrolyte are added to the base electrolyte to obtain an electrolyte. and 1,1'-sulfonylbis(4-ethynylbenzene) equivalent to 0.5 (mass) % of the electrolyte, to obtain an electrolyte.

[0095] Example A5

[0096] The present example provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0097] The electrolyte additive includes diprop-2-ynyl sulfone, and 1,1'-sulfonylbis(4-ethynylbenzene),

[0098] The electrolyte comprises lithium hexafluorophosphate, lithium bisfluorosulfonimide, dipropargyl sulfone electrolyte additive and 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additive dissolved in a non-aqueous organic solvent, wherein the concentration of the electrolyte lithium salt is 1.25 mol / L, the mass concentration of the dipropargyl sulfone electrolyte additive is 0.5%, and the mass concentration of the 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additive is 0.5%; the non-aqueous organic solvent comprises a mixed solvent of fluoroethylene carbonate, difluoroethylene carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0099] The configuration method of the electrolyte is as follows:

[0100] The fluoroethylene carbonate, difluoroethylene carbonate and dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a non-aqueous organic solvent, lithium hexafluorophosphate and lithium bisfluorosulfonimide are added to the non-aqueous organic solvent in a molar ratio of 1:0.25 to make the concentration of the electrolyte lithium salt 1.25 mol / L, thereby obtaining a basic electrolyte, and then dipropargyl sulfone and 1,1'-sulfonylbis(4-ethynylphenyl) are added to the basic electrolyte, wherein the amount of the dipropargyl sulfone is equivalent to 0.5% (mass) of the electrolyte, and the amount of the 1,1'-sulfonylbis(4-ethynylphenyl) is equivalent to 0.5% (mass) of the electrolyte. The configuration method of the electrolyte is as follows:

[0101] Embodiment A6

[0102] The embodiment provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0103] The electrolyte additive comprises dipropargyl sulfone, and 1,1'-sulfonylbis(4-ethynylphenyl),

[0104] The electrolyte comprises lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, dipropargyl sulfone electrolyte additive and 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additive dissolved in a non-aqueous organic solvent, wherein the concentration of the electrolyte lithium salt is 1.5 mol / L, the mass concentration of the dipropargyl sulfone electrolyte additive is 0.5%, and the mass concentration of the 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additive is 0.5%; the non-aqueous organic solvent comprises a mixed solvent of fluoroethylene carbonate, difluoroethylene carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0105] The configuration method of the electrolyte is as follows:

[0106] ​The fluorinated ethylene carbonate, the difluorinated ethylene carbonate and the dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a non-aqueous organic solvent, lithium hexafluorophosphate and lithium bis(trifluoromethylsulfonyl)imide are added in the non-aqueous organic solvent in a molar ratio of 1:0.5 to make the electrolyte lithium salt concentration 1.5 mol / L to obtain a basic electrolyte, and then 0.5 (mass) % of diprop-2-ynyl sulfone relative to the electrolyte is added to the basic electrolyte, and 1,1'-sulfonylbis(4-ethynylphenyl) relative to the electrolyte 0.5 (mass) %, to obtain an electrolyte.

[0107] Example A7

[0108] The present embodiment provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0109] The electrolyte additive includes diprop-2-ynyl sulfone, and 1,1'-sulfonylbis(4-ethynylphenyl),

[0110] The electrolyte includes lithium hexafluorophosphate, a diprop-2-ynyl sulfone electrolyte additive and a 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additive dissolved in a non-aqueous organic solvent, wherein the concentration of the electrolyte lithium salt is 0.8 mol / L, the mass concentration of the diprop-2-ynyl sulfone electrolyte additive is 0.5%, and the mass concentration of the 1,1'-sulfonylbis(4-ethynylphenyl) electrolyte additive is 0.5%; the non-aqueous organic solvent includes a mixed solvent of fluorinated ethylene carbonate, difluorinated ethylene carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0111] The configuration method of the electrolyte is as follows:

[0112] The fluorinated ethylene carbonate, the difluorinated ethylene carbonate and the dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a non-aqueous organic solvent, lithium hexafluorophosphate is added in the non-aqueous organic solvent to make the electrolyte lithium salt concentration 0.8 mol / L to obtain a basic electrolyte, and then 0.5 (mass) % of diprop-2-ynyl sulfone relative to the electrolyte is added to the basic electrolyte, and 1,1'-sulfonylbis(4-ethynylphenyl) relative to the electrolyte 0.5 (mass) %, to obtain an electrolyte.

[0113] Example A8

[0114] The present embodiment provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0115] The electrolyte additive is diprop-2-ynyl sulfone,

[0116] The electrolyte comprises lithium hexafluorophosphate and diprop-2-ynyl sulfone electrolyte additive dissolved in a non-aqueous organic solvent, wherein the concentration of the electrolyte lithium salt is 1 mol / L, and the mass concentration of the diprop-2-ynyl sulfone electrolyte additive is 1%; the non-aqueous organic solvent comprises a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0117] The configuration method of the electrolyte is as follows:

[0118] The ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a non-aqueous organic solvent, lithium hexafluorophosphate is added to the non-aqueous organic solvent to make the concentration of the electrolyte lithium salt 1 mol / L, thus obtaining a basic electrolyte, and then diprop-2-ynyl sulfone is added to the basic electrolyte to obtain the electrolyte.

[0119] Example A9

[0120] The present example provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0121] The electrolyte additive is diprop-2-ynyl sulfone,

[0122] The electrolyte comprises lithium hexafluorophosphate and diprop-2-ynyl sulfone electrolyte additive dissolved in a non-aqueous organic solvent, wherein the concentration of the electrolyte lithium salt is 1 mol / L, and the mass concentration of the diprop-2-ynyl sulfone electrolyte additive is 0.5%; the non-aqueous organic solvent comprises a mixed solvent of fluoroethylene carbonate, fluoro methyl ethyl carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0123] The configuration method of the electrolyte is as follows:

[0124] The fluoroethylene carbonate, fluoro methyl ethyl carbonate and dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a non-aqueous organic solvent, lithium hexafluorophosphate is added to the non-aqueous organic solvent to make the concentration of the electrolyte lithium salt 1 mol / L, thus obtaining a basic electrolyte, and then diprop-2-ynyl sulfone is added to the basic electrolyte to obtain the electrolyte. The configuration method of the electrolyte is as follows:

[0125] Example A10

[0126] The present example provides an electrolyte additive and an electrolyte containing the electrolyte additive.

[0127] The electrolyte additive is diprop-2-ynyl sulfone,

[0128] The electrolyte comprises lithium hexafluorophosphate dissolved in a non-aqueous organic solvent, a diprop-2-ynyl sulfone electrolyte additive, wherein the concentration of the electrolyte lithium salt is 1 mol / L, and the mass concentration of the diprop-2-ynyl sulfone electrolyte additive is 2%; the non-aqueous organic solvent comprises a mixed solvent of fluoroethylene carbonate, fluoroethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:1:7.

[0129] The configuration method of the electrolyte is as follows:

[0130] The fluoroethylene carbonate, fluoroethyl methyl carbonate and dimethyl carbonate are mixed in a mass ratio of 2:1:7 to obtain a non-aqueous organic solvent, lithium hexafluorophosphate is added to the non-aqueous organic solvent to make the concentration of the electrolyte lithium salt 1 mol / L, thereby obtaining a basic electrolyte, and then diprop-2-ynyl sulfone equivalent to 2% (mass) of the electrolyte is added to the basic electrolyte. The electrolyte is obtained.

[0131] 2. Lithium ion secondary battery embodiment

[0132] Embodiment B1

[0133] The embodiment provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode active material contained in the positive electrode is spinel lithium nickel manganese oxide; the negative electrode active material contained in the negative electrode is Li, and the preparation method of the lithium ion secondary battery comprises the following steps.

[0134] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of an aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained.

[0135] The silicon-carbon composite material, conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of a copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained.

[0136] The separator is a ceramic separator coated with Al2O3 on one side;

[0137] The electrolyte is the electrolyte in embodiment A1;

[0138] The prepared positive electrode sheet, separator and negative electrode sheet are placed on an automatic winding machine to obtain a bare battery cell; the bare battery cell is placed in a cylindrical steel shell, the negative electrode tab and the cap tab are welded, the prepared electrolyte is injected into the dried battery cell, and then the battery cell is sealed, placed, pre-charged, aged and filled to prepare a 18650 lithium ion secondary battery. Or assembled into a button cell LIR2430

[0139] Example B2

[0140] The embodiment provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode active material contained in the positive electrode is spinel lithium nickel manganese oxide; the negative electrode active material contained in the negative electrode is Li, and the preparation method of the lithium ion secondary battery comprises the following steps.

[0141] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed according to the mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the surface of an aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained.

[0142] The silicon-carbon composite material, conductive carbon black, butadiene rubber and carboxymethyl cellulose are mixed according to the mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the surface of a copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained.

[0143] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0144] The electrolyte is the electrolyte in Example A2;

[0145] The prepared positive electrode sheet, the separator and the negative electrode sheet are placed on an automatic winding machine to obtain a bare battery cell; the bare battery cell is placed in a cylindrical steel shell, the negative electrode tab and the cap tab are welded, the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged and filled to prepare a 18650 lithium ion secondary battery.

[0146] Example B3

[0147] The embodiment provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode active material contained in the positive electrode is spinel lithium nickel manganese oxide; the negative electrode active material contained in the negative electrode is Li, and the preparation method of the lithium ion secondary battery comprises the following steps.

[0148] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed according to the mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the surface of an aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained.

[0149] The silicon-carbon composite material, conductive carbon black, butadiene rubber and carboxymethyl cellulose are mixed according to the mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the surface of a copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained.

[0150] The separator is a ceramic separator coated with Al2O3 on one side;

[0151] The electrolyte is the electrolyte in Example A3.

[0152] The prepared positive electrode sheet, separator, and negative electrode sheet are placed on an automatic winding machine to obtain a bare battery cell by winding. The bare battery cell is placed in a cylindrical steel shell, and the negative electrode tab and the cap tab are welded. The prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged, and filled to prepare a 18650 lithium ion secondary battery.

[0153] Example B4

[0154] The present embodiment provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode active material contained in the positive electrode is spinel lithium nickel manganese oxide; the negative electrode active material contained in the negative electrode is Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0155] The spinel positive electrode active material, conductive carbon black, and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, and the positive electrode slurry is coated on both sides of the aluminum foil. After drying, calendering, and vacuum drying, a positive electrode sheet is obtained.

[0156] The silicon-carbon composite material, conductive carbon black, butadiene rubber, and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, and the negative electrode slurry is coated on both sides of the copper foil. After drying, calendering, and vacuum drying, a negative electrode sheet is obtained.

[0157] The separator is a ceramic separator coated with Al2O3 on one side;

[0158] The electrolyte is the electrolyte in Example A4.

[0159] The prepared positive electrode sheet, separator, and negative electrode sheet are placed on an automatic winding machine to obtain a bare battery cell by winding. The bare battery cell is placed in a cylindrical steel shell, and the negative electrode tab and the cap tab are welded. The prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged, and filled to prepare a 18650 lithium ion secondary battery.

[0160] Example B5

[0161] The present embodiment provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode active material contained in the positive electrode is spinel lithium nickel manganese oxide; the negative electrode active material contained in the negative electrode is Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0162] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the surface of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0163] The silicon-carbon composite material, conductive carbon black, butadiene-styrene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the surface of the copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained;

[0164] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0165] The electrolyte is the electrolyte in Example A5;

[0166] The prepared positive electrode sheet, separator and negative electrode sheet are placed on an automatic winding machine to obtain a bare battery cell; the bare battery cell is placed in a cylindrical steel shell, the negative electrode tab and the cap tab are welded, the prepared electrolyte is injected into the dried battery cell, and then sealing, standing, pre-charging, aging and capacity distribution are performed to prepare a 18650 lithium ion secondary battery.

[0167] Example B6

[0168] The present embodiment provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode active material contained in the positive electrode is spinel lithium nickel manganese oxide; the negative electrode active material contained in the negative electrode is Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0169] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the surface of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0170] The silicon-carbon composite material, conductive carbon black, butadiene-styrene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the surface of the copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained;

[0171] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0172] The electrolyte is the electrolyte in Example A6;

[0173] The prepared positive plate, the separator, and the negative plate are placed on an automatic winding machine to obtain a bare battery cell by winding; the bare battery cell is placed in a cylindrical steel shell, and the negative electrode tab and the cap tab are welded; the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged, and divided to obtain a 18650 lithium ion secondary battery.

[0174] Example B7

[0175] The present embodiment provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode contains a positive electrode active material of spinel lithium nickel manganese oxide; the negative electrode contains a negative electrode active material of Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0176] The spinel positive electrode active material, conductive carbon black, and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the aluminum foil, and after drying, calendering, and vacuum drying, a positive electrode sheet is obtained;

[0177] The silicon-carbon composite material, conductive carbon black, butadiene rubber, and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the copper foil, and after drying, calendering, and vacuum drying, a negative electrode sheet is obtained;

[0178] The separator is a ceramic separator coated with Al2O3 on one side;

[0179] The electrolyte is the electrolyte in Example A7;

[0180] The prepared positive plate, the separator, and the negative plate are placed on an automatic winding machine to obtain a bare battery cell by winding; the bare battery cell is placed in a cylindrical steel shell, and the negative electrode tab and the cap tab are welded; the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged, and divided to obtain a 18650 lithium ion secondary battery.

[0181] Example B8

[0182] The present embodiment provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode contains a positive electrode active material of a mixture of spinel lithium nickel manganese oxide and lithium-rich manganese material, and the mass ratio of spinel lithium nickel manganese oxide and lithium-rich manganese material is 99:1; the negative electrode contains a negative electrode active material of Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0183] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the surface of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0184] The silicon-carbon composite material, conductive carbon black, butadiene-styrene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the surface of the copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained;

[0185] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0186] The electrolyte is the electrolyte in Example A1;

[0187] The prepared positive electrode sheet, separator and negative electrode sheet are placed on an automatic winding machine to obtain a bare battery cell; the bare battery cell is placed in a cylindrical steel shell, the negative electrode tab and the cap tab are welded, the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged and filled to prepare a 18650 lithium ion secondary battery.

[0188] Example B9

[0189] The present embodiment provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode active material contained in the positive electrode is a mixture of spinel lithium nickel manganese oxide and lithium-rich manganese material, and the mass ratio of spinel lithium nickel manganese oxide and lithium-rich manganese material is 95:5; the negative electrode active material contained in the negative electrode is Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0190] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the surface of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0191] The silicon-carbon composite material, conductive carbon black, butadiene-styrene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the surface of the copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained;

[0192] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0193] The electrolyte is the electrolyte in Example A1;

[0194] The prepared positive plate, the separator, and the negative plate are placed on an automatic winding machine to obtain a bare battery cell by winding; the bare battery cell is placed in a cylindrical steel shell, the negative tab and the cap tab are welded, the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged, and divided to obtain a 18650 lithium ion secondary battery.

[0195] Example B10

[0196] The present embodiment provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode contains a mixture of spinel lithium nickel manganese oxide and lithium-rich manganese material as the positive electrode active material, and the mass ratio of spinel lithium nickel manganese oxide and lithium-rich manganese material is 90:10; the negative electrode contains Li as the negative electrode active material, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0197] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0198] The silicon-carbon composite material, conductive carbon black, butadiene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained;

[0199] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0200] The electrolyte is the electrolyte in Example A1;

[0201] The prepared positive plate, the separator, and the negative plate are placed on an automatic winding machine to obtain a bare battery cell by winding; the bare battery cell is placed in a cylindrical steel shell, the negative tab and the cap tab are welded, the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged, and divided to obtain a 18650 lithium ion secondary battery.

[0202] Example B11

[0203] The present embodiment provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode contains a mixture of spinel lithium nickel manganese oxide and lithium-rich manganese material as the positive electrode active material, and the mass ratio of spinel lithium nickel manganese oxide and lithium-rich manganese material is 80:20; the negative electrode contains Li as the negative electrode active material, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0204] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the surface of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0205] The silicon-carbon composite material, conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the surface of the copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained;

[0206] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0207] The electrolyte is the electrolyte in Example A1;

[0208] The prepared positive electrode sheet, separator and negative electrode sheet are placed on an automatic winding machine to obtain a bare battery cell; the bare battery cell is placed in a cylindrical steel shell, the negative electrode tab and the cap tab are welded, the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged and filled to prepare a 18650 lithium ion secondary battery.

[0209] Example B12

[0210] The present embodiment provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode active material contained in the positive electrode is a mixture of spinel lithium nickel manganese oxide and lithium-rich manganese material, and the mass ratio of spinel lithium nickel manganese oxide and lithium-rich manganese material is 70:30; the negative electrode active material contained in the negative electrode is Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0211] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the surface of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0212] The silicon-carbon composite material, conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the surface of the copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained;

[0213] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0214] The electrolyte is the electrolyte in Example A1;

[0215] The prepared positive plate, the separator, and the negative plate are placed on an automatic winding machine to obtain a bare battery cell by winding; the bare battery cell is placed in a cylindrical steel shell, and the negative tab and the cap tab are welded; the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged, and divided to obtain a 18650 lithium ion secondary battery.

[0216] Example B13

[0217] The present embodiment provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode contains a positive electrode active material of spinel lithium nickel manganese oxide, the negative electrode contains a negative electrode active material of Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0218] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0219] The silicon-carbon composite material, conductive carbon black, butadiene rubber and carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of the copper foil, and after drying, calendering and vacuum drying, a negative electrode sheet is obtained;

[0220] The separator is a ceramic separator prepared by coating Al2O3 on one side;

[0221] The electrolyte is the electrolyte in Example A8;

[0222] The prepared positive plate, the separator, and the negative plate are placed on an automatic winding machine to obtain a bare battery cell by winding; the bare battery cell is placed in a cylindrical steel shell, and the negative tab and the cap tab are welded; the prepared electrolyte is injected into the dried battery cell, and the battery cell is sealed, placed, pre-charged, aged, and divided to obtain a 18650 lithium ion secondary battery.

[0223] Example B14

[0224] The present embodiment provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode contains a positive electrode active material of spinel lithium nickel manganese oxide, the negative electrode contains a negative electrode active material of Li, and the preparation method of the lithium ion secondary battery comprises the following steps:

[0225] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, the positive electrode slurry is coated on both sides of the aluminum foil, and after drying, calendering and vacuum drying, a positive electrode sheet is obtained;

[0226] The silicon-carbon composite material, conductive carbon black, butadiene-styrene rubber and carboxymethyl cellulose were mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, and the negative electrode slurry was coated on both sides of the copper foil. After drying, calendering and vacuum drying, a negative electrode sheet was obtained.

[0227] The separator was a ceramic separator coated with Al2O3 on one side.

[0228] The electrolyte was the electrolyte in Example A9.

[0229] The prepared positive electrode sheet, separator and negative electrode sheet were placed on an automatic winding machine to obtain a bare battery cell. The bare battery cell was placed in a cylindrical steel shell, and the negative electrode tab and the cap tab were welded. The prepared electrolyte was injected into the dried battery cell, sealed, allowed to stand, pre-charged, aged and divided to prepare a 18650 lithium ion secondary battery.

[0230] Example B15

[0231] The present embodiment provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode active material contained in the positive electrode is spinel lithium nickel manganese oxide, and the negative electrode active material contained in the negative electrode is Li. The preparation method of the lithium ion secondary battery comprises the following steps:

[0232] The spinel positive electrode active material, conductive carbon black and polyvinylidene fluoride were mixed in a mass ratio of 97.3:1.2:1.5, dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry, and the positive electrode slurry was coated on both sides of the aluminum foil. After drying, calendering and vacuum drying, a positive electrode sheet was obtained.

[0233] The silicon-carbon composite material, conductive carbon black, butadiene-styrene rubber and carboxymethyl cellulose were mixed in a mass ratio of 96:1:1.2:1.8, dispersed in deionized water to obtain a negative electrode slurry, and the negative electrode slurry was coated on both sides of the copper foil. After drying, calendering and vacuum drying, a negative electrode sheet was obtained.

[0234] The separator was a ceramic separator coated with Al2O3 on one side.

[0235] The electrolyte was the electrolyte in Example A10.

[0236] The prepared positive electrode sheet, separator and negative electrode sheet were placed on an automatic winding machine to obtain a bare battery cell. The bare battery cell was placed in a cylindrical steel shell, and the negative electrode tab and the cap tab were welded. The prepared electrolyte was injected into the dried battery cell, sealed, allowed to stand, pre-charged, aged and divided to prepare a 18650 lithium ion secondary battery.

[0237] Comparative Example B1

[0238] The difference from Example B1 is that the non-aqueous organic solvent is mixed by mass ratio of 2:1:7 of ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate to obtain a non-aqueous organic solvent;

[0239] 1 (mass) % of diprop-2-ynyl sulfone is not added in the electrolyte,

[0240] Comparative Example B2

[0241] The difference from Example B1 is that the non-aqueous organic solvent is mixed by mass ratio of 2:1:7 of ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate to obtain a non-aqueous organic solvent;

[0242] 1 (mass) % of diprop-2-ynyl sulfone is not added in the electrolyte,

[0243] The lithium ion secondary batteries prepared in the above Examples B1-B15, Comparative Example B1 and Comparative Example B2 are subjected to performance tests, and the test methods are as follows:

[0244] (1) Linear sweep voltammetry (LSV)

[0245] A three-electrode device is assembled with Pt as the working electrode, Li as the counter electrode and reference electrode, and linear scanning is carried out on an electrochemical workstation.

[0246] (2) Cycle performance test:

[0247] At 25±2℃ / 45±2℃, the 18650 battery is charged with 0.5C cross-flow constant voltage to 4.9V (cut-off current is 0.01C), and then discharged with 1C constant current to 3.5V. The capacity retention rate of the Nth cycle is calculated after N cycles of charge / discharge, and the calculation formula is as follows:

[0248] The Nth cycle capacity retention rate (%) = (Nth cycle discharge capacity / 1st cycle discharge capacity) x 100%;

[0249] (3) High temperature storage performance:

[0250] The battery after the distribution is charged with 0.5C constant current and constant voltage to 4.8V (cut-off current is 0.01C) at room temperature, and the initial discharge capacity of the battery is measured. After 7 days of storage at 60℃, the battery is discharged to 3.5V at 0.5C to measure the retention capacity and recovery capacity of the battery. The calculation formula is as follows:

[0251] Battery capacity retention rate (%) = retention capacity / initial capacity x 100%;

[0252] Battery capacity recovery rate (%) = recovery capacity / initial capacity x 100%.

[0253] The results of the above Test (1) and Test (2) are shown in the following table:

[0254]

[0255] As can be seen from the above Examples B1-B15 and Comparative Example B2, the high-voltage cycle performance of the lithium secondary battery is significantly improved after using the electrolyte additive of the present application compared to not using the corresponding electrolyte additive, and thus the electrolyte additive of the present application and the electrolyte having the corresponding electrolyte additive can effectively improve the high-voltage cycle performance of the battery.

[0256] Among them, the retention rate of the secondary battery prepared by Example B1 is still above 80% after 500 cycles, as shown in Table 1 and Table 2. Figure 1 Figure 2

[0257] When the secondary batteries prepared by Examples B1, B2 and Comparative Example B1 are subjected to LSV evaluation analysis, the results are shown in Table 3. Figure 3 As can be seen from the figure, the secondary battery containing the diprop-2-ynyl sulfone or 1,1'-sulfonyl bis(4-ethynylphenyl) electrolyte additive widens the electrochemical window, and it is speculated that because the two additives contain carbon-carbon triple bond structures, they are easily adsorbed on the surface of the Pt electrode, inhibiting the oxidation and decomposition of the electrolyte components at the Pt electrode, thereby widening the electrochemical window.

[0258] As can be seen from the data comparison of Examples B1 and B13, the cycle performance is significantly improved when the non-aqueous organic solvent includes a fluorinated organic solvent, and it is speculated that the addition of the fluorinated organic solvent can form a solid electrolyte of LiF on the surface of the electrode, effectively inhibiting the formation of lithium dendrites, and also improving the oxidation stability of the electrolyte, the adaptability of the high-voltage cathode, and the cycle stability of the lithium secondary battery.

[0259] As can be seen from the data comparison of Examples B1-12, when the positive active ingredient of the secondary battery uses spinel lithium nickel manganese oxide and lithium-rich manganese material, the capacity of the battery is significantly improved, as shown in Table 4, but at the same time, as the proportion of the amount of lithium-rich manganese material increases, the cycle performance gradually decreases. Figure 4

[0260] As can be seen from the data of Examples B14 and B15, when the amount of electrolyte additive is within the range of 0.5-2%, the cycle performance of the battery can be improved.

[0261] The results of the above Test (3) are shown in the following table:

[0262] ​​​

[0263]

[0264] From the comparison of the data of the above examples B1-B15 and comparative examples B1, B2, it can be seen that the lithium secondary battery using the electrolyte additive of the present application has good stability at high temperature, while the retention rate and recovery rate of the secondary battery without the additive of the present application after high-temperature storage are significantly reduced, thus it can be seen that the electrolyte film formed on the electrode surface by the electrolyte additive of the present application has good high-temperature stability, thereby effectively avoiding the decomposition of electrolyte to produce gas, and to some extent, effectively preventing the electrode and electrolyte interface reaction. From the data of examples B13-B15, it can be seen that whether fluorinated organic solvent is used in the solvent also has a certain influence on the high-temperature stability.

[0265] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An electrolyte additive characterized by: The compound I has the general formula as follows: ，I； A1 is a dimethyl sulfone group or a diphenyl sulfone group, and X1 and X2 are independently hydrogen, methyl, or a methylene-containing organic group having 2-5 carbon atoms.

2. The electrolyte additive of claim 1, wherein: The compounds I include at least one of: and at least one of.

3. An electrolyte, characterized by: The electrolyte comprises a non-aqueous organic solvent and a lithium salt and an additive dissolved in the non-aqueous organic solvent, and the additive comprises the electrolyte additive of claim 1 or 2.

4. The electrolyte of claim 3, wherein: The mass percentage content of the electrolyte additive in the electrolyte is 0.05-2%; and / or The molar concentration of the lithium salt is 0.8-1.5 mol / L.

5. The electrolyte according to claim 3 or 4, characterized in that: The non-aqueous organic solvent comprises a fluorinated organic solvent.

6. The electrolyte of claim 5, wherein: The fluorinated organic solvent comprises at least one of a fluorinated carbonate, a fluorinated carboxylate, and a fluorinated ether.

7. The electrolyte of claim 3, 4 or 6, wherein: The non-aqueous organic solvent comprises at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone.

8. The electrolyte of claim 3, 4 or 6, wherein: The lithium salt comprises at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium bis(fluoro-oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

9. A secondary battery characterized by comprising: The electrolyte comprises a non-aqueous organic solvent and a lithium salt and an additive dissolved in the non-aqueous organic solvent, and the additive comprises the electrolyte additive of claim 1 or 2.

10. The secondary battery according to claim 9, wherein: The positive electrode material comprises at least one of spinel lithium nickel manganese oxide and lithium-rich manganese material; and / or The negative electrode material comprises at least one of lithium, graphite, Si-containing composite material, and lithium titanate; and / or The separator comprises at least one of single-layer polyethylene, single-layer polypropylene, double-layer polyethylene / polypropylene separator, three-layer polypropylene separator, inorganic coating modified separator, and polymer coating modified separator.

11. The secondary battery of claim 10, wherein: The positive electrode comprises spinel lithium nickel manganese oxide and lithium-rich manganese material, and the mass ratio of the spinel lithium nickel manganese oxide to the lithium-rich manganese material is (70-99):(1-30); and / or The spinel lithium nickel manganese oxide has a molecular formula of LiNi 0.5-x Mn 1.5 M x O 4-y F y , LiNi 0.5 Mn 1.5-x M x O 4-y F y or LiNi 0.5-x / 2 Mn 1.5-x / 2 M x O 4-y F y , 0≤x≤0.08, 0≤y≤0.1; and / or The molecular formula of the lithium-rich manganese material is zLiMnO2·(1-z)Li2MO3, wherein 0.1≤z≤0.7, and M comprises at least one of Ni, Mn, and Co.

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