Electrolyte for improving wettability of dry electrolyte and lithium ion battery

Abstract

The invention relates to an electrolyte for improving wettability of a dry-method electrode and a lithium ion battery in the technical field of lithium battery production. The electrolyte comprises a wettability additive, and the wettability additive comprises ethyl perfluoroethyl ether; the mass ratio of the wettability additive is 0.01%-5%. Ethyl perfluoroethyl ether has a certain polarity and a proper dielectric constant, and can greatly reduce the surface tension of the electrolyte, thereby improving the infiltration capacity of the electrolyte to an electrode and a diaphragm. And the contact area between the electrolyte and the electrode is increased due to the enhanced infiltration capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery production, and particularly relates to an electrolyte and a lithium ion battery for improving the wettability of dry electrolytes. Background Art

[0002] Lithium ion batteries are widely used in fields such as consumer electronics, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and good safety. In the composition of lithium batteries, the electrolyte is a crucial component. It is not only responsible for the conduction of lithium ions but also directly affects the overall performance and stability of the battery. The selection and characteristics of the electrolyte have a profound impact on the efficiency, life, and safety of the battery. In recent years, with the development of dry electrode preparation technology, dry electrodes have received increasing attention due to their simple process, environmental friendliness, and high material utilization rate. However, dry electrodes pose certain challenges in terms of wettability. Compared with traditional wet electrodes, the pore structure and surface characteristics of dry electrodes may result in poor wettability of the electrolyte. This insufficient wettability not only affects the conduction efficiency of lithium ions but may also lead to poor contact between the electrode and the electrolyte, thereby affecting the charge and discharge performance of the battery. Therefore, developing electrolytes with better wetting properties has become an important research direction for improving the performance of lithium batteries. In summary, the role of the electrolyte in lithium batteries cannot be ignored, especially in the application of dry electrodes. Improving the wettability of the electrolyte will be one of the key factors for enhancing battery performance. Summary of the Invention

[0003] In order to solve the problem that dry electrodes are prone to insufficient wettability of the electrolyte, a technical solution is disclosed in the present invention. The technical solution of the present invention is implemented as follows:

[0004] The first aspect of the present invention discloses an electrolyte for improving the wettability of dry electrodes. The electrolyte includes a wetting additive, and the wetting additive includes a component with the following structural formula:

[0005]

[0006] Preferably, based on the total mass of the electrolyte being 100%, the mass ratio of the wetting additive is 0.01% - 5% 。

[0007] Preferably, the electrolyte further includes a lithium salt, a solvent, and a film-forming additive.

[0008] Preferably, the lithium salt includes lithium hexafluorophosphate (LiPF 6 )、lithium perchlorate (LiClO 4 )、lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide salt (LiFSI), lithium tetrafluoroborate (LiBF4 )、Lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorophosphate (LiPO 2 F 2 ), or at least one of them.

[0009] Preferably, the concentration of the lithium salt in the electrolyte is 0.5 mol / L to 1.5 mol / L.

[0010] Preferably, the solvent includes non-aqueous organic solvents; the non-aqueous organic solvents include carbonates and / or carboxylates.

[0011] Preferably, the carbonate includes at least one of dimethyl carbonate, fluoroethylene carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, difluoropropylene carbonate, trichloroethyl methyl carbonate, 4-trichloromethyl ethylene carbonate, trifluoromethyl carbonate, chloroethylene carbonate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, bis(2,2,2-trifluoroethyl) carbonate.

[0012] Preferably, the carboxylate includes at least one of propyl fluorobutyrate, propyl chloroacetate, ethyl fluoroacetate, methyl fluoropropionate, ethyl fluoropropionate, isopropyl acetate, methyl propionate, isopropyl propionate, propyl fluoropropionate, isopropyl fluoroacetate, butyl fluoropropionate, propyl acetate, ethyl acetate, methyl acetate, propyl butyrate, isopropyl fluoropropionate, ethyl chloro-butyrate, butyl propionate, ethyl butyrate, ethyl propionate, propyl propionate.

[0013] Preferably, the film-forming additive includes at least one of cyclic sulfates, phosphates, sultones, borates, and silane compounds.

[0014] Preferably, based on the total mass of the electrolyte being 100%, the mass ratio of the lithium salt is 0.5% to 20%; the mass ratio of the solvent is 1% to 90%; the mass ratio of the film-forming additive is 0.01% to 5%.

[0015] Preferably, the film-forming additive participates in forming a CEI or SEI film.

[0016] The second aspect of the present invention discloses a lithium-ion battery, which includes the electrolyte disclosed in the first aspect of the present invention.

[0017] Preferably, the lithium-ion battery further includes a positive electrode, a separator, and a negative electrode, and at least one of the positive electrode and the negative electrode is prepared by a dry process. The positive electrode and / or negative electrode prepared by the dry process is mainly obtained by grinding dry fibrillated carbon and a dry binder to obtain a dry mixture, compressing it to obtain a self-supporting dry film, and then bonding the above dry film to a current collector to form an electrode. The dry process electrode realizes the adhesion of active substances by the fibrillation of the binder. After the powder materials are mixed, a self-supporting film is directly prepared, and it is rolled with the current collector to prepare an electrode. This method eliminates processes such as slurry preparation, coating, drying, and solvent recovery, and adds a dry film-forming process. Common film-forming methods include the binder fibrillation method and electrostatic spraying method, with the binder fibrillation method being the main one.

[0018] Preferably, the positive electrode includes a positive electrode active material;

[0019] In the present invention, the specific types of the positive electrode active materials are not specifically limited and can be selected according to requirements. Specifically, the positive electrode active material can be selected from at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium-rich manganese-based materials, and lithium vanadium phosphate;

[0020] Preferably, the negative electrode includes a negative electrode active material;

[0021] In the present invention, the specific types of the negative electrode active materials are not specifically limited and can be selected according to requirements. Specifically, the negative electrode active material can be selected from at least one of lithium metal, hard carbon, soft carbon, artificial graphite, natural graphite, a composite material of single crystal silicon and graphite, a composite material of silicon monoxide and graphite, and lithium titanate.

[0022] Preferably, a separator is provided between the positive electrode and the negative electrode of the lithium battery of the present invention to prevent short circuit. The material and shape of the separator used in the present invention are not particularly limited, and it can be any technology disclosed in the prior art.

[0023] Preferably, the separator may include a polyolefin-based separator or a glass fiber-based separator.

[0024] The advantages of the present invention are as follows:

[0025] The present invention provides an electrolyte for improving the wettability of a dry process electrolyte. The electrolyte includes an additive, ethyl perfluoroethyl ether. Ethyl perfluoroethyl ether has a certain polarity and a suitable dielectric constant, and can greatly reduce the surface tension of the electrolyte, thereby improving the wetting ability of the electrolyte for the electrode and the separator. The enhanced wetting ability increases the contact area between the electrolyte and the electrode, and further improves the performance of the lithium-ion battery. Detailed implementation manners

[0026] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs; the terms used in the specific embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusion.

[0028] In the description of the specific embodiments of the present invention, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0029] Referring to "embodiments" in the present invention means that specific features, structures or characteristics described in combination with the embodiments can be included in at least one embodiment of the present invention. The phrase appearing in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present invention can be combined with other embodiments.

[0030] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present invention generally represents an "or" relationship between the associated objects before and after.

[0031] Throughout the present invention, numerical values represent approximate measures or limits of ranges, covering minor deviations from a given value, as well as embodiments having approximately the mentioned value and embodiments having the exact value mentioned. Except for the working examples provided at the end of the detailed description, all numerical values of parameters (e.g., amounts or conditions) in this specification (including the appended claims) should be understood to be modified in all cases by the term "about", whether or not "about" actually appears before the numerical value. "About" indicates that there is some minor inaccuracy in the stated numerical value (somewhat close to the exact value of the stated value; approximately or reasonably close to the stated value; nearly). If the inaccuracy provided by "about" is not otherwise understood in the art in this ordinary meaning, then "about" as used in the present invention indicates at least the variations that can be produced by ordinary methods of measuring and using such parameters. For example, "about" may include variations of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%.

[0032] In addition, the disclosure of a range includes the disclosure of all values within the entire range and further divided ranges, including the endpoints and sub-ranges given for these ranges.

[0033] The pore structure and surface properties of the dry electrode may result in poor wettability of the electrolyte. This insufficient wettability not only affects the conduction efficiency of lithium ions but also may lead to poor contact between the electrode and the electrolyte, thus affecting the charge and discharge performance of the battery.

[0034] To address the above deficiencies, the present invention proposes a technical solution.

[0035] The first aspect of the present invention discloses an electrolyte for improving the wettability of a dry electrode, the electrolyte comprising a wetting additive, and the wetting additive comprising a component having the following structural formula:

[0036]

[0037] Ethyl perfluoroethyl ether has a certain polarity and a suitable dielectric constant, and can significantly reduce the surface tension of the electrolyte, thereby improving the wetting ability of the electrolyte to the electrode and the separator. The enhanced wetting ability increases the contact area between the electrolyte and the electrode.

[0038] In some embodiments, based on the total mass of the electrolyte being 100%, the mass percentage of the wetting additive is 0.01% - 5% 。

[0039] In specific applications, the mass percentage of the wettability additive in the electrolyte can be selected as 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. The percentage values listed above are only examples and are not limiting.

[0040] In some embodiments, the electrolyte further includes a lithium salt, a solvent, and a film-forming additive.

[0041] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide salt (LiFSI), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), and lithium difluorophosphate (LiPO 2 F 2 ).

[0042] As used herein, "at least one" means selecting one or two or more from the listed components, structures, or compositions as a preference of the technical solution, and the combinations of these selections will not exceed the understanding scope of those skilled in the art. Those skilled in the art can freely implement them without obstacles based on common general knowledge and well-known technologies in the art. The same applies hereinafter.

[0043] Those skilled in the art should be aware that in the electrolyte, the above lithium salts do not react with each other. Therefore, without exceeding the understanding scope of those skilled in the art, in specific applications, those skilled in the art can select any one or a combination of two or more of them as needed, and the present invention does not impose any restrictions on this.

[0044] In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5 mol / L to 1.5 mol / L.

[0045] In specific applications, the concentration of the lithium salt in the electrolyte can be selected as 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.5 mol / L, etc. The values listed above are only examples and are not limiting.

[0046] In some embodiments, the solvent includes a non-aqueous organic solvent; the non-aqueous organic solvent includes a carbonate and / or a carboxylate.

[0047] As used in the present invention, "and / or" means that among the two components listed above, either one can be selected or they can be used in combination. Without exceeding the understanding of those skilled in the art, the present invention can be freely implemented.

[0048] In some embodiments, the carbonate includes at least one of dimethyl carbonate, fluoroethylene carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, bisfluoropropylene carbonate, trichloroethyl methyl carbonate, 4-trichloromethyl ethylene carbonate, trifluoromethyl ethylene carbonate, chloroethylene carbonate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, bis(2,2,2-trifluoroethyl) carbonate.

[0049] In some embodiments, the carboxylate includes at least one of propyl fluorobutyrate, propyl chloroacetate, ethyl fluoroacetate, methyl fluoropropionate, ethyl fluoropropionate, isopropyl acetate, methyl propionate, isopropyl propionate, propyl fluoropropionate, isopropyl fluoroacetate, butyl fluoropropionate, propyl acetate, ethyl acetate, methyl acetate, propyl butyrate, isopropyl fluoropropionate, ethyl chlorobutyrate, butyl propionate, ethyl butyrate, ethyl propionate, propyl propionate.

[0050] In some preferred embodiments, the solvent includes ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0051] When the non-aqueous organic solvent includes the above three, the performance of the electrolyte is the best, and thus the performance of the prepared lithium-ion battery is optimal.

[0052] Based on the total mass of the electrolyte being 100%, the mass ratio of EC is 15% - 25%; the mass ratio of DEC is 15% - 25%; the mass ratio of EMC is 35% - 55%.

[0053] In specific applications, the mass ratio of EC in the electrolyte can be selected as 15%, 18%, 20%, 23%, 25%, etc.; the mass ratio of DEC in the electrolyte can be selected as 15%, 18%, 20%, 23%, 25%, etc.; the mass ratio of EMC in the electrolyte can be selected as 35%, 38%, 40%, 43%, 45%, 48%, 50%, 55%, etc. The percentage values listed above are only examples and not limitations.

[0054] In some embodiments, the film-forming additive includes at least one of cyclic sulfate, phosphate, sulfonic acid lactone, borate, and silane compound.

[0055] In some embodiments, based on the total mass of the electrolyte being 100%, the mass percentage of the lithium salt is 0.5% to 20%; the mass percentage of the solvent is 1% to 90%; the mass percentage of the film-forming additive is 0.01% to 5%.

[0056] In specific applications, the mass percentage of the lithium salt in the electrolyte can be selected as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 8%, 10%, 12%, 15%, 20%, etc.; the mass percentage of the solvent in the electrolyte can be selected as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 8%, 10%, 12%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc.; the mass percentage of the film-forming additive in the electrolyte can be selected as 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. The percentage values listed above are only examples and not limitations.

[0057] In some embodiments, the film-forming additive participates in forming the CEI or SEI film.

[0058] The second aspect of the present invention discloses a lithium-ion battery, which includes the electrolyte disclosed in the first aspect of the present invention, and further includes a positive electrode, a separator, and a negative electrode. At least one of the positive electrode and the negative electrode is prepared by a dry method. The positive electrode or negative electrode prepared by the dry method is mainly obtained by grinding dry fibrillated carbon and a dry binder to obtain a dry mixture, compressing it to obtain a self-supporting dry film, and then bonding the above dry film to a current collector to form an electrode. The dry electrode uses the fibrillization of the binder to achieve the adhesion of the active substances. After the powder materials are mixed, a self-supporting film is directly prepared and then rolled with the current collector to form an electrode. This method eliminates processes such as slurry preparation, coating, drying, and solvent recovery, and adds a dry film-forming process. Common film-forming methods include the binder fibrillization method and electrostatic spraying method, with the binder fibrillization method being the main one.

[0059] In some embodiments, the positive electrode includes a positive electrode active substance;

[0060] In the present invention, the specific types of the positive electrode active materials are not specifically limited and can be selected according to requirements. Specifically, the positive electrode active substance can be selected from at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium-rich manganese-based materials, and lithium vanadium phosphate;

[0061] In some embodiments, the negative electrode includes a negative electrode active substance;

[0062] In the present invention, the specific types of the negative electrode active material are not specifically limited and can be selected according to requirements. Specifically, the negative electrode active material can be selected from at least one of lithium metal, hard carbon, soft carbon, artificial graphite, natural graphite, a composite material of single crystal silicon and graphite, a composite material of silicon suboxide and graphite, and lithium titanate.

[0063] In some embodiments, a separator is provided between the positive electrode and the negative electrode of the lithium battery of the present invention to prevent short circuit. The material and shape of the separator used in the present invention are not particularly limited, and it can be any technology disclosed in the prior art.

[0064] In some embodiments, the separator may include a polyolefin-based separator or a glass fiber-based separator.

[0065] Hereinafter, the embodiments of the present invention will be specifically described through examples and comparative examples. Among them, all the examples and comparative examples are groups of all-solid-state battery samples prepared by the same process, and the number of samples in each group is 20.

[0066] It should be noted that the embodiments of the present invention are not limited to these examples.

[0067] Example 1: A lithium ion battery includes a dry-type positive electrode, a dry-type negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0068] I. Preparation of the dry-type positive electrode:

[0069] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll them into a positive electrode active material layer.

[0070] 2. Roll and laminate the positive electrode active material layer and the current collector aluminum foil.

[0071] II. Preparation of the dry-type negative electrode:

[0072] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent acetylene black, and perform fibrillation treatment, and roll them into a negative electrode active material layer.

[0073] 2. Roll and laminate the negative electrode active material layer and the copper foil.

[0074] III. Preparation of the electrolyte

[0075] S1. The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to a non-aqueous organic solvent, and continuously stir for 30 min until completely mixed;

[0076] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 min.

[0077] S2. Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate lactone (PS), and stir for another 30 min to mix evenly, thus completing the preparation of the electrolyte.

[0078] By mass percentage, the prepared electrolyte includes 19.22% EC, 20.24% DEC, 45.53% EMC, 12% LiPF 6 , 0.01% wetting additive, and 3% film-forming additive.

[0079] IV. Preparation of lithium-ion battery

[0080] Stack the positive electrode and negative electrode prepared above and the separator in sequence, with the separator positioned between the positive and negative electrodes to obtain a bare battery cell. Place the bare battery cell in an outer packaging shell, inject the electrolyte, and perform processes such as vacuum packaging, standing, forming, and shaping to obtain a lithium-ion battery.

[0081] Example 2: A lithium-ion battery includes a dry-process positive electrode, a dry-process negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0082] I. Preparation of dry-process positive electrode:

[0083] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, then roll-press to form a positive electrode active material layer.

[0084] 2. Roll-press and compound the positive electrode active material layer and the current collector aluminum foil.

[0085] II. Preparation of dry-process negative electrode:

[0086] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, then roll-press to form a negative electrode active material layer.

[0087] 2. Roll-press and compound the negative electrode active material layer and the copper foil.

[0088] III. Preparation of electrolyte

[0089] S1. The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to the non-aqueous organic solvent, and continuously stir for 30 min until completely mixed;

[0090] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 min.

[0091] S2, Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate lactone (PS), and stir for another 30 min to mix evenly, completing the preparation of the electrolyte.

[0092] By mass percentage, the prepared electrolyte includes 19% EC, 20% DEC, 45% EMC, 12% LiPF 6 , 1% wetting additive, and 3% film-forming additive.

[0093] IV. Preparation of lithium-ion battery

[0094] Stack the above-prepared positive electrode, negative electrode, and separator in sequence, with the separator between the positive and negative electrodes to obtain a bare battery cell. Place the bare battery cell in an outer packaging shell, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0095] Example 3: A lithium-ion battery, including a dry-process positive electrode, a dry-process negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0096] I. Preparation of dry-process positive electrode:

[0097] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll them into a positive electrode active material layer.

[0098] 2. Roll and compound the positive electrode active material layer and the current collector aluminum foil.

[0099] II. Preparation of dry-process negative electrode:

[0100] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, and roll them into a negative electrode active material layer.

[0101] 2. Roll and compound the negative electrode active material layer and the copper foil.

[0102] III. Preparation of electrolyte

[0103] S1, The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to the non-aqueous organic solvent, and continuously stir for 30 min until completely mixed;

[0104] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 minutes.

[0105] S2, Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate lactone (PS), and stir for another 30 minutes to mix evenly to complete the preparation of the electrolyte.

[0106] By mass percentage, the prepared electrolyte includes 18.77% EC, 19.77% DEC, 44.46% EMC, 12% LiPF 6 , 2% wetting additive, 3% film-forming additive.

[0107] IV. Preparation of lithium-ion battery

[0108] Stack the above-prepared positive electrode, negative electrode, and separator in sequence, with the separator between the positive and negative electrodes to obtain a bare battery cell. Place the bare battery cell in an outer packaging shell, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0109] Example 4: A lithium-ion battery, including a dry-process positive electrode, a dry-process negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0110] I. Preparation of dry-process positive electrode:

[0111] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll-press it into a positive electrode active material layer.

[0112] 2. Roll-press and composite the positive electrode active material layer and the current collector aluminum foil.

[0113] II. Preparation of dry-process negative electrode:

[0114] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, and roll-press it into shape to obtain a negative electrode active material layer.

[0115] 2. Roll-press and composite the negative electrode active material layer and the copper foil.

[0116] III. Preparation of electrolyte

[0117] S1, The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to the non-aqueous organic solvent, and continuously stir for 30 minutes until completely mixed;

[0118] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 min.

[0119] S2, Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate lactone (PS), and stir for another 30 min to mix evenly to complete the preparation of the electrolyte.

[0120] By mass percentage, the prepared electrolyte includes 18.55% EC, 19.53% DEC, 43.92% EMC, 12% LiPF 6 , 3% wetting additive, 3% film-forming additive.

[0121] IV. Preparation of lithium-ion battery

[0122] Stack the positive electrode, negative electrode, and separator prepared above in sequence, with the separator between the positive and negative electrodes to obtain a bare battery cell. Place the bare battery cell in an outer packaging shell, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0123] Example 5: A lithium-ion battery includes a dry-process positive electrode, a dry-process negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0124] I. Preparation of dry-process positive electrode:

[0125] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll them into a positive electrode active material layer.

[0126] 2. Roll-compound the positive electrode active material layer and the current collector aluminum foil.

[0127] II. Preparation of dry-process negative electrode:

[0128] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, and roll them into shape to obtain a negative electrode active material layer.

[0129] 2. Roll-compound the negative electrode active material layer and the copper foil.

[0130] III. Preparation of electrolyte

[0131] S1, The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to the non-aqueous organic solvent, and continuously stir for 30 min until completely mixed;

[0132] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 min.

[0133] S2, Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate lactone (PS), and stir for another 30 min to mix evenly, completing the preparation of the electrolyte.

[0134] By mass percentage, the prepared electrolyte includes 18.32% EC, 19.29% DEC, 43.39% EMC, 12% LiPF 6 , 4% wetting additive, 3% film-forming additive.

[0135] IV. Preparation of lithium-ion battery

[0136] Stack the positive electrode and negative electrode prepared above and the separator in sequence, with the separator between the positive and negative electrodes, to obtain a bare battery cell. Place the bare battery cell in an outer packaging shell, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0137] Example 6: A lithium-ion battery, including a dry-process positive electrode, a dry-process negative electrode, a separator and an electrolyte. The preparation method is as follows:

[0138] I. Preparation of dry-process positive electrode:

[0139] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll-press it into a positive electrode active material layer.

[0140] 2. Roll-press and compound the positive electrode active material layer and the current collector aluminum foil.

[0141] II. Preparation of dry-process negative electrode:

[0142] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, and roll-press it into shape to obtain a negative electrode active material layer.

[0143] 2. Roll-press and compound the negative electrode active material layer and the copper foil.

[0144] III. Preparation of electrolyte

[0145] S1, The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to the non-aqueous organic solvent, and continuously stir for 30 min until completely mixed;

[0146] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 minutes.

[0147] S2. Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate lactone (PS), and stir for another 30 minutes until evenly mixed to complete the preparation of the electrolyte.

[0148] By mass percentage, the prepared electrolyte includes 18.10% EC, 19.04% DEC, 42.86% EMC, 12% LiPF 6 , 5% wetting additive, and 3% film-forming additive.

[0149] IV. Preparation of lithium-ion battery

[0150] Stack the positive electrode and negative electrode prepared above and the separator in sequence, with the separator positioned between the positive and negative electrodes to obtain a bare cell. Place the bare cell in an outer packaging shell, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0151] Example 7: A lithium-ion battery, including a dry-process positive electrode, a dry-process negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0152] I. Preparation of dry-process positive electrode:

[0153] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll them into a positive electrode active material layer.

[0154] 2. Roll and compound the positive electrode active material layer and the current collector aluminum foil.

[0155] II. Preparation of dry-process negative electrode:

[0156] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, and roll them into a negative electrode active material layer.

[0157] 2. Roll and compound the negative electrode active material layer and the copper foil.

[0158] III. Preparation of electrolyte

[0159] S1. The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salts LiPF 6 and LiFSI to the non-aqueous organic solvent, and continuously stir for 30 minutes until completely mixed;

[0160] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 min.

[0161] S2. Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate lactone (PS), and stir for another 30 min to mix evenly, thus completing the preparation of the electrolyte.

[0162] By mass percentage, the prepared electrolyte includes 19% EC, 20% DEC, 45% EMC, 3% LiPF 6 , 9% LiFSI, 1% wetting additive, and 3% film-forming additive.

[0163] IV. Preparation of lithium-ion battery

[0164] Stack the positive electrode and negative electrode prepared above and the separator in sequence, with the separator placed between the positive and negative electrodes to obtain a bare battery cell. Place the bare battery cell in an outer packaging shell, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0165] Comparative Example 1: A lithium-ion battery includes a dry-process positive electrode, a dry-process negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0166] I. Preparation of dry-process positive electrode:

[0167] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll them into a positive electrode active material layer.

[0168] 2. Roll and compound the positive electrode active material layer and the current collector aluminum foil.

[0169] II. Preparation of dry-process negative electrode:

[0170] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, and roll them into shape to obtain a negative electrode active material layer.

[0171] 2. Roll and compound the negative electrode active material layer and the copper foil.

[0172] III. Preparation of electrolyte

[0173] S1. The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to the non-aqueous organic solvent, and continuously stir for 30 min until completely mixed;

[0174] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 minutes.

[0175] S2, Add the film-forming additive 3-propenyl carbonate lactone (PS) and stir again for 30 minutes until evenly mixed to complete the preparation of the electrolyte.

[0176] By mass percentage, the prepared electrolyte includes 19.23% EC, 20.23% DEC, 45.54% EMC, 12% LiPF 6 , 3% additive B.

[0177] IV. Preparation of lithium-ion battery

[0178] Stack the prepared positive electrode and negative electrode with the separator in sequence, with the separator between the positive and negative electrodes, to obtain a bare battery cell. Place the bare battery cell in an outer packaging shell, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0179] Comparative Example 2: A lithium-ion battery includes a dry-process positive electrode, a dry-process negative electrode, a separator and an electrolyte. The preparation method is as follows:

[0180] I. Preparation of dry-process positive electrode:

[0181] 1. Mix the positive electrode active material lithium manganate, conductive agent Super-P, and binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll-press it into a positive electrode active material layer.

[0182] 2. Roll-press and compound the positive electrode active material layer and the current collector aluminum foil.

[0183] II. Preparation of dry-process negative electrode:

[0184] 1. Mix the negative electrode active material graphite, binder polytetrafluoroethylene (PTFE), and conductive agent Super-P, and perform fibrillation treatment, and roll-press it into shape to obtain a negative electrode active material layer.

[0185] 2. Roll-press and compound the negative electrode active material layer and the copper foil.

[0186] III. Preparation of electrolyte

[0187] S1, The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to the non-aqueous organic solvent and continuously stir for 30 minutes until completely mixed;

[0188] Preparation method of non-aqueous organic solvent: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are put into a container and mixed for 30 minutes.

[0189] S2. Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate (PS), and stir for another 30 min to mix evenly, thus completing the preparation of the electrolyte.

[0190] By mass percentage, the prepared electrolyte includes 19.23% EC, 20.229% DEC, 45.54% EMC, 12% LiPF 6 , 0.001% wetting additive, and 3% film-forming additive.

[0191] IV. Preparation of Lithium-Ion Battery

[0192] Stack the above-prepared positive electrode, negative electrode, and separator in sequence, with the separator placed between the positive and negative electrodes to obtain a bare battery cell. Place the bare battery cell in an outer packaging case, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0193] Comparative Example 3: A lithium-ion battery includes a dry-process positive electrode, a dry-process negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0194] I. Preparation of Dry-Process Positive Electrode:

[0195] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll them into a positive electrode active material layer.

[0196] 2. Roll and compound the positive electrode active material layer and the current collector aluminum foil.

[0197] II. Preparation of Dry-Process Negative Electrode:

[0198] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, and roll them into shape to obtain a negative electrode active material layer.

[0199] 2. Roll and compound the negative electrode active material layer and the copper foil.

[0200] III. Preparation of Electrolyte

[0201] S1. The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salt LiPF 6 to the non-aqueous organic solvent, and continuously stir for 30 min until completely mixed;

[0202] Preparation method of non-aqueous organic solvent: Put ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) together in a container and mix for 30 min.

[0203] S2. Add the wetting additive ethyl perfluoroethyl ether and the film-forming additive 3-propenyl carbonate (PS), and stir for another 30 min until evenly mixed to complete the preparation of the electrolyte.

[0204] By mass percentage, the prepared electrolyte includes 17.64% EC, 18.57% DEC, 41.79% EMC, 12% LiPF 6 , 7% wetting additive, and 3% film-forming additive.

[0205] IV. Preparation of Lithium-Ion Batteries

[0206] Stack the above-prepared positive electrode, negative electrode, and separator in sequence, with the separator between the positive and negative electrodes to obtain a bare battery cell. Place the bare battery cell in an outer packaging case, inject the electrolyte, and perform processes such as vacuum packaging, standing, forming, and shaping to obtain a lithium-ion battery.

[0207] Comparative Example 4: A lithium-ion battery includes a dry-process positive electrode, a dry-process negative electrode, a separator, and an electrolyte. The preparation method is as follows:

[0208] I. Preparation of the dry-process positive electrode:

[0209] 1. Mix the positive electrode active material lithium manganate, the conductive agent Super-P, and the binder polyvinylidene fluoride (PVDF), and perform fibrillation treatment, and roll them into a positive electrode active material layer.

[0210] 2. Roll and compound the positive electrode active material layer and the current collector aluminum foil.

[0211] II. Preparation of the dry-process negative electrode:

[0212] 1. Mix the negative electrode active material graphite, the binder polytetrafluoroethylene (PTFE), and the conductive agent Super-P, and perform fibrillation treatment, and roll them into a negative electrode active material layer.

[0213] 2. Roll and compound the negative electrode active material layer and the copper foil.

[0214] III. Preparation of the electrolyte

[0215] S1. The concentration of the lithium salt in the electrolyte is 1 mol / L. Add the lithium salts LiPF 6 and LiFSI to the non-aqueous organic solvent, and continuously stir for 30 min until completely mixed;

[0216] Preparation method of the non-aqueous organic solvent: Put ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) into a container and mix for 30 min.

[0217] S2. Add the film-forming additive 3-propenyl carbonate (PS) and stir for another 30 min to mix evenly, thus completing the preparation of the electrolyte.

[0218] By mass percentage, the prepared electrolyte includes 19.23% EC, 20.23% DEC, 45.54% EMC, 3% LiPF 6 , 9% LiFSI, and 3% film-forming additive.

[0219] IV. Preparation of Lithium-Ion Batteries

[0220] Stack the above-prepared positive electrode and negative electrode with the separator in sequence, with the separator placed between the positive and negative electrodes to obtain a bare battery cell. Place the bare battery cell in an outer packaging case, inject the electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0221] Comparative Experiments

[0222] Take a total of 11 groups of samples from Examples 1-7 and Comparative Examples 1-4 above, and conduct the following tests respectively. All test data are averaged, and some values are rounded off.

[0223] 1. Contact Angle Test:

[0224] Using the electrolyte as the liquid to be measured, use the dry-type positive electrode and dry-type negative electrode in each group of samples as the substrates respectively. Use a micro syringe to apply 5 μL of liquid on the substrate surface. After applying the liquid droplet, use a high-resolution camera to take an image of the liquid droplet. Ensure that the liquid droplet remains stationary during shooting to obtain an accurate contact angle. A contact angle measuring instrument can automatically identify the liquid droplet and calculate the contact angle.

[0225] 2. Capacity Retention Rate Test (the number of cycles when the capacity retention rate of the test sample decays to 80%):

[0226] After charging the samples in each group at a rate of 0.01C for the first cycle and discharging at a rate of 0.1C for the first cycle, conduct charge and discharge tests on the samples at a rate of 1C. Then, take the number of cycles when the discharge capacity of the samples decays to 80% of the discharge capacity in the first cycle of charge and discharge at 1C as the standard, and thus record the number of cycles of each group of samples.

[0227] The test results are shown in the following table:

[0228]

[0229] As can be seen from the above table:

[0230] Comparative Examples 1 to 6: When the addition amount of the wetting additive increases, the contact angle becomes smaller, and its wetting performance becomes better, but the capacity retention performance (number of cycles) will be affected. This may be because too much addition amount will generate gas and has a low boiling point. After comprehensive analysis, when Example 2 with an addition amount of 1% is selected, it is used as its optimal parameter.

[0231] In Example 7, the composition of the lithium salt in the electrolyte was changed. Compared with Example 2, its contact angle decreased significantly, and the wetting performance became better, but the capacity retention performance (number of cycles) decreased significantly. This may be due to the corrosion of the current collector by LiFSI.

[0232] Analysis of the results of Comparative Examples 1, 2, and 3, which are without wetting additive, with too low an addition amount of wetting additive, and with too high an addition amount of wetting additive respectively:

[0233] Comparing Comparative Examples 2 and 3 with Comparative Example 1, when the amount of wetting additive is too small, the change in the contact angle is not significant. When the amount of wetting additive is too large, the contact angle decreases significantly. At this time, the wetting performance is excellent, but the capacity retention rate (number of cycles) will be greatly affected. Especially when the addition amount is too large, the battery capacity retention performance drops significantly.

[0234] Comparing Comparative Example 4 with Example 7: Without adding a wetting additive, it can be clearly seen that although its capacity retention performance (number of cycles) increases, the contact angle is large and the wetting performance is significantly poor.

[0235] It should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electrolyte for improving the wettability of a dry electrode, characterized in that: Including a wettability additive, the wettability additive includes a component of the following structural formula:

2. The electrolyte according to claim 1, wherein the mass of the wettability additive accounts for 0.01% to 5% based on the total mass of the electrolyte being 100%. 。 3. The electrolyte according to claim 1, characterized in that Also included are lithium salts, solvents and film-forming additives.

4. The electrolyte according to claim 3, characterized in that The lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI), lithium bis(fluorosulfonyl imide) salt (LiFSI), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiDFOB), and lithium difluorophosphate (LiPO2F2).

5. The electrolyte according to claim 3, characterized in that The concentration of the lithium salt in the electrolyte is 0.5 mol / L to 1.5 mol / L.

6. The electrolyte according to claim 3, characterized in that The solvent includes a non-aqueous organic solvent; the non-aqueous organic solvent includes a carbonate and / or a carboxylate.

7. The electrolyte according to claim 3, characterized in that The film-forming additive includes at least one of cyclic sulfate, phosphate, sultone, borate, and silane compounds.

8. The electrolyte according to claim 3, characterized in that Taking the total mass of the electrolyte as 100%, the mass of the lithium salt accounts for 0.5% to 20%; the mass of the solvent accounts for 1% to 90%; and the mass of the film-forming additive accounts for 0.01% to 5%.

9. A lithium ion battery comprising the electrolyte according to any one of claims 1 to 8.

10. The lithium ion battery according to claim 9, characterized in that The invention also includes a positive electrode, a separator and a negative electrode, wherein at least one of the positive electrode and the negative electrode is prepared by a dry method.

Images