CN114975939A - Water-based cathode slurry, cathode pole piece and lithium ion battery - Google Patents

Abstract

The application discloses an aqueous cathode slurry, a cathode pole piece and a lithium ion battery. The aqueous cathode slurry comprises a cathode active material, an aqueous polymer, a conductive agent, an aqueous dispersant and water, wherein the aqueous polymer comprises a flexible group, and the flexible group is selected from at least one of an ethylene group and an acrylic group. The application discloses aqueous cathode slurry include the waterborne polymer for the cathode active layer obtained by its preparation has higher adhesion, stronger toughness and stronger electrolyte resistance ability, and then makes including the lithium ion battery of cathode active layer still has lower manufacturing cost when having good electrical property and mechanical properties, can effectively improve lithium ion battery's price/performance ratio.

Description

Aqueous cathode slurry, cathode sheet and lithium ion battery

technical field

The present application relates to the field of battery technology, and in particular, to an aqueous cathode slurry, a cathode electrode sheet prepared from the aqueous cathode electrode slurry, and a lithium ion battery including the cathode electrode sheet.

Background technique

With the wide application of consumer electronic products and electric vehicles, lithium-ion batteries with high energy density, excellent cycle performance and rapid charge and discharge performance are increasingly favored and valued by the market. The large-scale application of lithium-ion batteries not only has higher requirements on battery performance, but also has higher and higher requirements on battery manufacturing costs and green manufacturing.

At present, the cathodes of lithium ions are mostly organic solvent cathodes, that is, the cathode active layer in the cathode plate is prepared from organic solvent cathode slurry, for example, NMP (nitrogen methyl pyrrolidone) + PVDF (polyvinylidene fluoride) Cathode slurry of the system. However, the cost of NMP is high and the volatilization into the atmosphere will cause environmental pollution. In addition, NMP is a high-boiling organic solvent, which requires a lot of energy consumption during the volatilization process, which indirectly increases the process cost.

The use of aqueous cathode slurry to prepare the cathode active layer can effectively reduce costs and achieve zero pollution. However, the cathode active layer prepared by the existing aqueous cathode slurry has poor toughness, which leads to the phenomenon that the cathode electrode piece is prone to cracking or powder falling during the manufacture or use of the lithium ion battery.

SUMMARY OF THE INVENTION

In view of this, the present application provides an aqueous cathode slurry, which aims to improve the problem of poor toughness of the cathode active layer prepared from the existing aqueous cathode slurry.

The embodiments of the present application are implemented as follows: an aqueous cathode slurry, comprising a cathode active material, an aqueous polymer, a conductive agent, an aqueous dispersant, and water, wherein the aqueous polymer includes a flexible group, and the flexible group At least one selected from vinyl and propenyl.

Optionally, in some embodiments of the present application, the aqueous cathode slurry is composed of the cathode active material, the aqueous polymer, the conductive agent, the aqueous dispersant, and water.

Optionally, in some embodiments of the present application, the content of the solid component in the aqueous cathode slurry is greater than or equal to 30 wt % and less than or equal to 95 wt %; and/or

Based on the total mass of the solid components in the aqueous cathode slurry, the content of the aqueous polymer is 1-10 wt %, the content of the aqueous dispersant is 0.1-3 wt %, and the content of the conductive agent is 0.5 wt % ~10wt%, the content of the cathode active material is 77-98.4wt%.

Optionally, in some embodiments of the present application, the aqueous polymer is selected from at least one of vinyl polymers and propylene-based polymers.

Optionally, in some embodiments of the present application, the vinyl polymer is selected from at least one of copolymers of ethylene and ester, copolymers of ethylene and acrylic acid, and copolymers of ethylene and acrylate; and /or

The propylene-based polymer is selected from at least one of a copolymer of polypropylene and maleic anhydride, a copolymer of polypropylene and maleic acid, and a polypropylene maleate copolymer.

Optionally, in some embodiments of the present application, the copolymer of ethylene and ester is selected from ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-methyl acrylate copolymer. at least one; and/or

The copolymer of ethylene and acrylic acid is selected from at least one of ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer; and/or

The copolymer of ethylene and acrylate is selected from at least one of polyethylene-acrylate and polyethylene-methacrylate, wherein the polyethylene-acrylate is selected from polyethylene-acrylate sodium salt, polyethylene At least one of ethylene-acrylic acid lithium salt, polyethylene-acrylic acid potassium salt, polyethylene-acrylic acid ammonium salt, and polyethylene-acrylic acid amine salt, the polyethylene-methacrylic acid salt is selected from polyethylene-methyl acrylate At least one of acrylic acid sodium salt, polyethylene-methacrylic acid lithium salt, polyethylene-methacrylic acid potassium salt, polyethylene-methacrylic acid ammonium salt, and polyethylene-methacrylic acid amine salt; and/ or

The copolymer of polypropylene and maleic anhydride is selected from polypropylene-maleic anhydride copolymers; and/or

The copolymer of polypropylene and maleic acid is at least one selected from polypropylene-maleic acid copolymer and polypropylene-ethylene-maleic acid copolymer; and/or

The polypropylene maleate copolymer is selected from at least one of polypropylene-maleate and polypropylene-ethylene-maleate, wherein the polypropylene-maleate is selected from the group consisting of At least one of propylene-maleic acid potassium salt, polypropylene-maleic acid lithium salt, polypropylene-maleic acid sodium salt, polypropylene-maleic acid ammonium salt, and polypropylene-maleic acid amine salt , the polypropylene-ethylene-maleate is selected from polypropylene-ethylene-maleate potassium salt, polypropylene-ethylene-maleate lithium salt, polypropylene-ethylene-maleate sodium salt, polypropylene- At least one of ethylene-maleic acid ammonium salt and polypropylene-ethylene-maleic acid amine salt.

Optionally, in some embodiments of the present application, the molecular weight of the aqueous polymer is 1×10 ⁴ to 1000×10 ⁴ .

Optionally, in some embodiments of the present application, the cathode active material is selected from at least one of lithium iron phosphate, lithium manganate, lithium iron manganese phosphate, nickel-cobalt-manganese ternary material and nickel-cobalt-aluminum ternary material. species; and/or

The conductive agent is selected from at least one of carbon black, graphite, carbon fiber, and carbon nanotubes; and/or

The aqueous dispersant is selected from sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyvinyl pyrrolidone, hydroxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyacrylic acid , polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyacrylic acid-acrylonitrile copolymer, polyacrylic acid-acrylate-acrylonitrile copolymer, methacrylic acid-acrylonitrile copolymer, acrylate - at least one of acrylonitrile copolymer, methacrylate-acrylonitrile copolymer, polyacrylate-acrylate-acrylonitrile copolymer, and polymethacrylate-acrylate-acrylonitrile copolymer.

Correspondingly, the embodiments of the present application also provide a cathode electrode sheet, which includes a cathode current collector and a cathode active layer combined on at least one surface of the cathode current collector, and the cathode active layer is prepared from the above-mentioned aqueous cathode slurry. to make.

Optionally, in some embodiments of the present application, in the cracked product after the cathode active layer is cracked by thermogravimetric mass spectrometry, ethylene monomer and/or propylene monomer account for 5% of the total weight of the monomers in the cracked product. ~95%.

Optionally, in some embodiments of the present application, the cathode active layer includes a cathode active material, an aqueous polymer, an aqueous dispersant and a conductive agent, and in the cathode active layer, the content of the aqueous polymer is 1-10wt%, the content of the aqueous dispersant is 0.1-3wt%, the content of the conductive agent is 0.5-10wt%, and the content of the cathode active material is 77-98.4wt%.

Correspondingly, an embodiment of the present application further provides a lithium ion battery, and the lithium ion battery includes the above-mentioned cathode electrode piece.

The aqueous cathode slurry described in the present application includes the aqueous polymer, so that the cathode active layer prepared therefrom has higher adhesive force, stronger toughness and stronger resistance to electrolyte solution, so as to include The lithium ion battery of the cathode active layer can have excellent electrical properties and mechanical properties, and at the same time have lower manufacturing cost, and can effectively improve the cost performance of the lithium ion battery.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, but not to limit the present application.

In the description of this application, the term "including" means "including but not limited to". Various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation to the scope of the present application; therefore, the described range should be considered The description has specifically disclosed all possible subranges as well as individual numerical values within that range. For example, a description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and Single numbers within the stated range, such as 1, 2, 3, 4, 5, and 6, apply regardless of the range. Additionally, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

An embodiment of the present application provides an aqueous cathode slurry, which includes a cathode active material, an aqueous polymer, a conductive agent, an aqueous dispersant, and water. Wherein, the aqueous polymer includes a flexible group, and the flexible group may be selected from, but not limited to, at least one of vinyl and acryl.

In some embodiments, the content (solid content) of the solid component of the aqueous cathode slurry is greater than or equal to 30 wt % and less than or equal to 95 wt %. Within the range of the solid content, the aqueous cathode slurry can have a suitable viscosity, which is favorable for uniform dispersion of solid components, and is easy to dry when preparing the cathode active layer, which is beneficial to the preparation of the cathode active layer. It can be understood that the solid components of the aqueous cathode slurry include cathode active material, aqueous polymer, conductive agent and aqueous dispersant.

In some embodiments, based on the total mass of the solid components in the aqueous cathode slurry, the content of the aqueous polymer is 1-10 wt %, the content of the aqueous dispersant is 0.1-3 wt %, and the The content of the conductive agent is 0.5-10 wt %, and the content of the cathode active material is 77-98.4 wt %.

The aqueous polymer may be selected from, but not limited to, at least one of vinyl polymers and propylene-based polymers. The vinyl polymer has a flexible group vinyl group, and the propylene-based polymer has a flexible group acryl group. The water-based polymer is used to improve the toughness of the cathode electrode sheet, and to provide the adhesion between the cathode active layer and the metal foil (current collector) and the resistance to electrolyte (ie, electrolyte resistance).

The vinyl polymer may be selected from, but not limited to, at least one of copolymers of ethylene and ester, copolymers of ethylene and acrylic acid, and copolymers of ethylene and acrylate.

In some embodiments, the copolymer of ethylene and ester may be selected from, but not limited to, at least one of ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-methyl acrylate copolymer .

In some embodiments, the copolymer of ethylene and acrylic acid may be selected from, but not limited to, at least one of ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers.

In some embodiments, the copolymer of ethylene and acrylate may be selected from, but not limited to, at least one of polyethylene-acrylate and polyethylene-methacrylate. Further, the polyethylene-acrylic acid salt can be selected from but not limited to polyethylene-acrylic acid sodium salt, polyethylene-acrylic acid lithium salt, polyethylene-acrylic acid potassium salt, polyethylene-acrylic acid ammonia salt, and polyethylene-acrylic acid at least one of the amine salts. The polyethylene-methacrylate can be selected from but not limited to polyethylene-methacrylic acid sodium salt, polyethylene-methacrylic acid lithium salt, polyethylene-methacrylic acid potassium salt, polyethylene-methacrylic acid ammonia salt, and at least one of polyethylene-methacrylate amine salt.

Further, in some embodiments, the polyethylene-acrylic acid ammonia salt can be selected from, but not limited to, polyethylene-acrylic acid ammonia.

Further, in some embodiments, the polyethylene-acrylic acid amine salt may be selected from, but not limited to, polyethylene-acrylic acid methylamine, polyethylene-acrylic acid dimethylamine, polyethylene-acrylic acid trimethylamine, polyethylene-acrylic acid ethylamine Amine, Polyethylene-Acrylic Diethylamine, Polyethylene-Acrylic Triethylamine Salt, Polyethylene-Acrylic N-Propylamine, Polyethylene-Acrylic N-Butylamine, Polyethylene-Acrylic Cyclohexylamine, Polyethylene-Acrylic Ethylene Diamine, Polyethylene-acrylic acid benzylamine, polyethylene-acrylic acid aniline, polyethylene-acrylic acid N-toluidine, polyethylene-acrylic acid N,N-xylidine, polyethylene-acrylic acid diphenylamine, polyethylene-acrylic acid triphenylamine, poly Ethylene-acrylic acid-o-toluidine, polyethylene-acrylic acid-m-toluidine, polyethylene-acrylic acid-p-toluidine, polyethylene-acrylic acid nitroaniline, polyethylene-acrylic acid diethanolamine, polyethylene-acrylic acid triethanolamine, and polyethylene-acrylic acid At least one of ethanolamine.

Further, in some embodiments, the polyethylene-methacrylic acid ammonia salt can be selected from, but not limited to, polyethylene-methacrylic acid ammonia.

Further, in some embodiments, the polyethylene-methacrylic acid amine salt can be selected from, but not limited to, polyethylene-methacrylic acid methylamine, polyethylene-methacrylic acid dimethylamine, polyethylene-methacrylic acid Trimethylamine, polyethylene-ethylamine methacrylate, polyethylene-diethylamine methacrylate, polyethylene-triethylamine methacrylate, polyethylene-n-propylamine methacrylate, polyethylene-n-butylamine methacrylate , polyethylene-cyclohexylamine methacrylate, polyethylene-ethylenediamine methacrylate, polyethylene-benzylamine methacrylate, polyethylene-methacrylate aniline, polyethylene-methacrylate N-toluidine, Polyethylene-methacrylic acid N,N-xylidine, polyethylene-methacrylic acid diphenylamine, polyethylene-methacrylic acid triphenylamine, polyethylene-methacrylic acid o-toluidine, polyethylene-methacrylic acid m-methyl Aniline, polyethylene-methacrylic acid-p-toluidine, polyethylene-methacrylic acid nitroaniline, polyethylene-methacrylic acid diethanolamine, polyethylene-methacrylic acid triethanolamine, and polyethylene-methacrylic acid ethanolamine at least one.

The propylene-based polymer may be selected from, but not limited to, at least one of copolymers of polypropylene and maleic anhydride, copolymers of polypropylene and maleic acid, and polypropylene maleate copolymers. It can be understood that the polypropylene maleate copolymer is the salt formed by the further reaction of the copolymer of polypropylene and maleic acid formed after the copolymerization of polypropylene and maleic acid. For example, in at least one embodiment, the The polypropylene maleate copolymer is a salt formed by reacting a copolymer of polypropylene and maleic acid with an alkali (eg, sodium hydroxide, etc.).

In some embodiments, the copolymer of polypropylene and maleic anhydride may be selected from polypropylene-maleic anhydride copolymers.

In some embodiments, the copolymer of polypropylene and maleic acid may be selected from, but not limited to, at least one of polypropylene-maleic acid copolymer and polypropylene-ethylene-maleic acid copolymer.

In some embodiments, the polypropylene maleate copolymer may be selected from, but not limited to, at least one of polypropylene-maleate, and polypropylene-ethylene-maleate. Wherein, the polypropylene-maleate can be selected from but not limited to polypropylene-maleate potassium salt, polypropylene-maleate lithium salt, polypropylene-maleate sodium salt, polypropylene-maleic acid At least one of ammonia salt and polypropylene-maleic acid amine salt; the polypropylene-ethylene-maleic acid salt can be selected from but not limited to polypropylene-ethylene-maleic acid potassium salt, polypropylene- At least one of ethylene-maleic acid lithium salt, polypropylene-ethylene-maleic acid sodium salt, polypropylene-ethylene-maleic acid ammonium salt, and polypropylene-ethylene-maleic acid amine salt.

Further, in some embodiments, the polypropylene-ammonium maleate salt can be selected from, but not limited to, polypropylene-ammonium maleate.

Further, in some embodiments, the polypropylene-maleic acid amine salt can be selected from but not limited to polypropylene-maleic acid methylamine, polypropylene-maleic acid dimethylamine, polypropylene-maleic acid Trimethylamine, polypropylene-ethylamine maleate, polypropylene-diethylamine maleate, polypropylene-triethylamine maleate, polypropylene-n-propylamine maleate, polypropylene-n-butyl maleate Amine, polypropylene-maleic acid cyclohexylamine, polypropylene-maleic acid ethylenediamine, polypropylene-maleic acid benzylamine, polypropylene-maleic acid aniline, polypropylene-maleic acid N-toluidine , polypropylene-maleic acid N,N-xylidine, polypropylene-maleic acid diphenylamine, polypropylene-maleic acid triphenylamine, polypropylene-maleic acid o-toluidine, polypropylene-maleic acid m-toluidine Toluidine, polypropylene-maleic acid-p-toluidine, polypropylene-maleic acid nitroaniline, polypropylene-maleic acid diethanolamine, polypropylene-maleic acid triethanolamine, and polypropylene-maleic acid ethanolamine at least one of.

Further, in some embodiments, the polypropylene-ethylene-ammonium maleate salt can be selected from, but not limited to, polypropylene-ethylene-ammonium maleate.

Further, in some embodiments, the polypropylene-ethylene-maleic acid amine salt can be selected from but not limited to polypropylene-ethylene-maleic acid methylamine, polypropylene-ethylene-maleic acid dimethylamine, Polypropylene-ethylene-maleic acid trimethylamine, polypropylene-ethylene-maleic acid ethylamine, polypropylene-ethylene-maleic acid diethylamine, polypropylene-ethylene-maleic acid triethylamine salt, polypropylene- Ethylene-n-propylamine maleate, polypropylene-ethylene-n-butylamine maleate, polypropylene-ethylene-cyclohexylamine maleate, polypropylene-ethylene-ethylenediamine maleate, polypropylene-ethylene-maleate Benzylamine to acid, polypropylene-ethylene-maleic aniline, polypropylene-ethylene-maleic acid N-toluidine, polypropylene-ethylene-maleic acid N,N-xylidine, polypropylene-ethylene- Diphenylamine maleate, polypropylene-ethylene-maleic acid triphenylamine, polypropylene-ethylene-maleic acid-o-toluidine, polypropylene-ethylene-maleic acid-m-toluidine, polypropylene-ethylene-maleic acid para- At least one of toluidine, polypropylene-ethylene-maleate nitroaniline, polypropylene-ethylene-maleate diethanolamine, polypropylene-ethylene-maleate triethanolamine, and polypropylene-ethylene-maleate ethanolamine A sort of.

In some embodiments, the molecular weight of the aqueous polymer is 1×10 ⁴ to 1000×10 ⁴ . Within the range of the molecular weight, the aqueous polymer can be uniformly dispersed in the aqueous cathode slurry, and the cathode active layer prepared from the aqueous cathode slurry can have strong electrolyte resistance and Adhesion to metal foil (current collector).

The cathode active material may be selected from, but not limited to, at least one of lithium iron phosphate, lithium manganate, lithium iron manganese phosphate, nickel-cobalt-manganese ternary material and nickel-cobalt-aluminum ternary material. Specifically, the cathode active material may be selected from, but not limited to, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li(Ni _a Co _b Mn _c )O ₂ , LiNi _a Co _b Al _c O ₂ , LiNi _y Co _1-y O ₂ , LiCo _y Mn _1-y O ₂ , LiCo _y Al _1-y O ₂ , LiCo _y B _1-y O ₂ , LiCo _y Mg _1-y O ₂ , LiCo _y Ti _1-y O ₂ , LiCo _y Mo _1-y O ₂ , LiCo _y Sn _1-y O ₂ , LiCo _y Ca _{1- y} O ₂ , LiCo _y Cu _1-y O ₂ , LiCo _y V _1-y O ₂ , LiCo _y Zr _1-y O ₂ , LiCo _y Si _1-y O ₂ , LiCo _y W _1-y O ₂ , LiCo _y Y _1-y O ₂ , LiCo _y La _{1- y} O ₂ , LiCo _y Mn _1-y O _2. At least one of LiNi _y Mn _1-y O ₂ , LiCoPO ₄ , LiFePO ₄ , and LiMn _y Fe _1-y PO ₄ . Wherein, 0<a<1, 0<b<1, a+b+c=1, 0<y<1.

The conductive agent may be selected from, but not limited to, at least one of carbon black, graphite, carbon fiber, and carbon nanotube.

The aqueous dispersant can be selected from but not limited to sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyvinyl pyrrolidone, hydroxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose At least one of polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, and polyacrylonitrile water-based polymer. The aqueous dispersant is used to promote uniform dispersion of the cathode active material, the conductive agent and the aqueous polymer in water.

In some embodiments, the polyacrylate may be selected from, but not limited to, at least one of lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, and ammonium polyacrylate.

In some embodiments, the polymethacrylate may be selected from, but not limited to, at least one of lithium polymethacrylate, sodium polymethacrylate, potassium polymethacrylate, and polyammonium methacrylate.

In some embodiments, the polyacrylonitrile water-based polymer may be selected from, but not limited to, polyacrylic acid-acrylonitrile copolymer, polyacrylic acid-acrylate-acrylonitrile copolymer, methacrylic acid-acrylonitrile copolymer, acrylic acid At least one of salt-acrylonitrile copolymer, methacrylate-acrylonitrile copolymer, polyacrylate-acrylate-acrylonitrile copolymer, and polymethacrylate-acrylate-acrylonitrile copolymer.

In some embodiments, the aqueous cathode slurry consists of the cathode active material, the aqueous polymer, the conductive agent, the aqueous dispersant, and water.

The aqueous cathode slurry described in this application includes the aqueous polymer and has specific components and proportions, so that the cathode active layer prepared from the aqueous cathode slurry has higher adhesion, stronger Toughness and strong electrolyte resistance.

The embodiment of the present application also provides a method for preparing the aqueous cathode slurry, comprising the following steps:

Step S11: providing the cathode active material, the aqueous polymer, the conductive agent, the aqueous dispersant and water;

Step S12: Mix the cathode active material, the aqueous polymer, the conductive agent, the aqueous dispersant and water in proportion to obtain the aqueous cathode slurry.

It can be understood that the mixing can be a method known in the art for mixing, such as stirring mixing, ultrasonic mixing and the like.

The present application also provides a cathode electrode sheet, the cathode electrode sheet includes a cathode current collector and a cathode active layer combined on at least one surface of the cathode current collector. The cathode active layer is prepared from the aqueous cathode slurry.

In some embodiments, in the cathode active layer, the content of the aqueous polymer is 1-10 wt %, the content of the aqueous dispersant is 0.1-3 wt %, and the content of the conductive agent is 0.5-10 wt % , the content of the cathode active material is 77-98.4 wt %.

The cathode active layer is cracked by thermogravimetric mass spectrometry (TG-MS), and the cracked product contains flexible monomers such as ethylene monomer and propylene monomer (that is, the monomer corresponding to the flexible group, such as the corresponding vinyl group). The monomer is at least one of ethylene monomer). In some embodiments, in the cracked product after the cathode active layer is cracked by thermogravimetric mass spectrometry, ethylene monomer and/or propylene monomer (ie, the total amount of flexible monomers in the cracked product) accounts for the proportion of the cracked product in the cracked product. 5 to 95% of the total monomer weight, such as 10 to 90%, or 15 to 85%, or 20 to 80%, or 25 to 75%, or 30 to 70%, or 35 to 65%, or 40 to 60% %, or 45 to 90%, or 50 to 95%. Within the range, the cathode active layer can have higher adhesive force and stronger toughness.

The material of the cathode current collector may be selected from, but not limited to, at least one material known in the art to be used in cathode current collectors, such as aluminum and nickel.

The cathode active layer of the cathode electrode sheet described in the present application is prepared from the above-mentioned aqueous cathode slurry, so that it has higher adhesive force, stronger toughness and stronger electrolyte resistance.

An embodiment of the present application also provides a method for preparing the cathode electrode sheet, comprising the following steps:

Step S21: providing the aqueous cathode slurry and the cathode current collector;

Step S22 : disposing the aqueous cathode slurry on the cathode current collector and drying to obtain a cathode active layer combined with the cathode current collector to obtain a cathode electrode sheet.

It can be understood that the method for disposing the aqueous cathode slurry on the cathode current collector may be a solution method. The solution method can be spin coating method, printing method, ink jet printing method, blade coating method, printing method, dip-pulling method, soaking method, spraying method, roller coating method, casting method, slot coating method and the like. Strip coating method, etc.

The drying may be at least one of heating drying, cooling drying and reduced pressure drying.

It can be understood that the steps of cold pressing and slitting may also be included after the drying.

The cathode electrode sheet is prepared from the aqueous cathode slurry, which can make the cathode electrode sheet have excellent electrical properties and mechanical properties, and also have the characteristics of low manufacturing cost and environmental protection.

Embodiments of the present application further provide an electrochemical device, including the cathode electrode sheet. The electrochemical device may be a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor. In some embodiments, the primary battery may be a primary lithium ion battery, and the secondary lithium ion battery may be a lithium secondary battery. The lithium ion secondary battery may be, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer battery, or a lithium ion polymer secondary battery.

The embodiment of the present application further provides a lithium ion battery, including the cathode electrode sheet, the anode electrode sheet, the electrolyte and the separator described above. Wherein, the diaphragm is located between the cathode and the anode, and the electrolyte is filled in the gap between the cathode and the diaphragm, and between the anode and the diaphragm middle.

The anode electrode sheet includes an anode current collector and an anode active material bound on the surface of the anode current collector.

The material of the anode current collector may be selected from, but not limited to, at least one of materials known in the art for anode current collectors, such as copper, nickel, stainless steel, and titanium.

The anode active material may be selected from, but not limited to, at least one of graphite-based carbon materials, non-graphite-based carbon materials, metallic lithium, alloy lithium, silicon-based alloys, tin-based alloys, conductive oxides, and conductive polymers. Wherein, the conductive oxide can be selected from but not limited to Li _x Fe ₂ O ₃ , Li _x WO ₂ , SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , At least one of Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ and Bi ₂ O ₅ , wherein 0<x<1; the conductive polymer can be selected from From but not limited to at least one of polyacetylene, polyaniline and polythiophene.

The electrolyte solution includes solvent, cation and anion. The solvent can be selected from, but not limited to, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, dimethyl sulfoxide, acetonitrile, tetrahydrofuran, N-methylpyrrolidone, ethyl methyl carbonate and γ - at least one of butyrolactone. The cation may be selected from, but not limited to, at least one of Li ⁺ , Na ⁺ and K ⁺ . The anion can be selected from but not limited to PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N(CF ₃ At least one of SO ₂ ) ₂ ^- and C(CF ₂ SO ₂ ) ₃ ^- .

The lithium ion battery can be, but is not limited to, a primary lithium ion battery, a secondary lithium ion battery, a fuel lithium ion battery, and a solar lithium ion battery.

It can be understood that the lithium ion battery may have a rolled structure, a laminated structure or a folded structure.

The cathode active layer in the cathode pole piece of the lithium ion battery described in the present application is prepared from the above-mentioned aqueous cathode slurry, which can ensure that the lithium ion battery has excellent electrical and mechanical properties, and at the same time, It also has lower manufacturing costs, which can effectively improve the cost performance of lithium-ion batteries.

The present application will be specifically described below through specific examples, and the following examples are only some examples of the present application, and are not intended to limit the present application.

Example 1

Preparation of cathode electrode

Add 94.5g lithium iron phosphate (cathode active material), 3g conductive carbon, 2g polyethylene-acrylate lithium salt (aqueous polymer), 0.5g sodium carboxymethyl cellulose (aqueous dispersant) to 100g water, fully After stirring and mixing evenly, an aqueous cathode slurry is obtained;

The aqueous cathode slurry is coated on the Al foil, dried and cold-pressed to obtain a cathode active layer combined on the surface of the Al foil, which is divided into strips to obtain a cathode electrode sheet.

The thickness of the cathode active layer in this embodiment is 200um.

Preparation of Anode Pieces

Add 97.5g of active material artificial graphite, 1.5g of binder styrene-butadiene rubber (SBR), and 1g of thickener sodium carboxymethylcellulose (CMC) into deionized water, and stir and mix well to obtain anode slurry;

The anode slurry is coated on Cu foil, dried, and cold-pressed to obtain an anode active layer, which is divided into strips to obtain an anode pole piece.

Preparation of the diaphragm

90g of ceramic particles and 10g of acrylate binder were added into deionized water and mixed uniformly to make a slurry, and then the slurry was uniformly coated to a wet-process polyethylene base with a thickness of 9um and a porosity of 45% by microgravure coating. The membrane is dried in an oven to obtain a composite porous membrane, and a PVDF adhesive coating is sprayed on the surface of the composite porous membrane to obtain a diaphragm.

Preparation of Lithium Ion Batteries

Stack the cathode pole piece, the diaphragm and the anode pole piece in order, so that the diaphragm is in the middle of the cathode pole piece and the anode pole piece to play a role of isolation, and roll it to obtain a bare cell; put the bare cell in the outer package, inject it into The electrolyte solution is packaged, and the lithium ion battery is prepared after chemical formation.

Example 2

This example is basically the same as Example 1, except that the lithium manganate is used to replace the lithium iron phosphate in Example 1 in the preparation of the cathode electrode piece of this example.

Example 3

This example is basically the same as Example 1, except that the lithium iron phosphate in Example 1 is replaced with lithium iron manganese phosphate during the preparation of the cathode electrode piece in this example.

Example 4

This example is basically the same as Example 1, except that 47.25g of lithium iron phosphate and 47.25g of lithium manganate are used to replace 94.5g of lithium iron phosphate in Example 1 during the preparation of the cathode electrode piece of this example.

Example 5

This example is basically the same as Example 1, except that the nickel-cobalt-manganese ternary material is used to replace the lithium iron phosphate in Example 1 in the preparation of the cathode electrode piece of this example.

Example 6

This example is basically the same as Example 1, the difference is that the nickel-cobalt-aluminum ternary material is used to replace the lithium iron phosphate in Example 1 in the preparation of the cathode electrode piece of this example.

Example 7

This example is basically the same as Example 1, except that the addition amount of the water-based flexible polymer in this example is 1 g, and the addition amount of lithium iron phosphate is 95.5 g.

Example 8

This example is basically the same as Example 1, except that in this example, the addition amount of the water-based flexible polymer is 1.5 g, and the addition amount of the cathode active material lithium iron phosphate is 95 g.

Example 9

This example is basically the same as Example 1, except that in this example, the addition amount of the water-based flexible polymer is 2.5 g, and the addition amount of the cathode active material lithium iron phosphate is 94 g.

Example 10

This example is basically the same as Example 1, except that in this example, the addition amount of the water-based flexible polymer is 3g, and the addition amount of the cathode active material lithium iron phosphate is 93.5g.

Example 11

This example is basically the same as Example 1, except that in this example, the addition amount of the water-based flexible polymer is 5g, and the addition amount of the cathode active material lithium iron phosphate is 91.5g.

Example 12

This example is basically the same as Example 1, except that in this example, the addition amount of the water-based flexible polymer is 10 g, and the addition amount of the cathode active material lithium iron phosphate is 86.5 g.

Example 13

This example is basically the same as Example 1, except that in this example, the addition amount of the water-based flexible polymer is 0.5 g, and the addition amount of the cathode active material lithium iron phosphate is 96 g.

Example 14

This example is basically the same as Example 1, except that in this example, the addition amount of the water-based flexible polymer is 0.9 g, and the addition amount of the cathode active material lithium iron phosphate is 95.6 g.

Example 15

This embodiment is basically the same as Embodiment 1, except that the thickness of the cathode active layer in this embodiment is 100 μm.

Example 16

This embodiment is basically the same as Embodiment 1, except that the thickness of the cathode active layer in this embodiment is 300um.

Example 17

This embodiment is basically the same as Embodiment 1, except that the thickness of the cathode active layer in this embodiment is 500 μm.

Example 18

This embodiment is basically the same as Embodiment 1, except that the thickness of the cathode active layer in this embodiment is 1000 μm.

Example 19

This embodiment is basically the same as Embodiment 1, except that this embodiment uses polyethylene-triethylamine acrylate to replace the polyethylene-lithium acrylate in Example 1.

Example 20

This embodiment is basically the same as Embodiment 1, except that this embodiment uses polypropylene-lithium maleate to replace the polyethylene-lithium acrylate in Example 1.

Comparative Example 1

This comparative example is basically the same as Example 1, the difference is that, in the preparation of the cathode electrode piece of this comparative example, polyvinylidene fluoride (PVDF, water-insoluble polymer) is used to replace the polyethylene-lithium acrylate salt in Example 1, The water in Example 1 was replaced with N-methylpyrrolidone, and the thickness of the cathode active layer of this comparative example was 100 um.

Comparative Example 2

This comparative example is basically the same as the comparative example 1, the difference is that the thickness of the cathode active layer of this comparative example is 200um.

Comparative Example 3

This comparative example is basically the same as the comparative example 1, the difference is that the thickness of the cathode active layer of this comparative example is 300um.

Comparative Example 4

This comparative example is basically the same as the comparative example 1, the difference is that the thickness of the cathode active layer of this comparative example is 500um.

Comparative Example 5

This comparative example is basically the same as Example 1, the difference is that, in the preparation of the cathode electrode piece of this comparative example, polyacrylic acid-propylene cyanoacrylate copolymer (a water-based polymer known to be used in the art) is used to replace the Polyethylene-Lithium Acrylate.

Comparative Example 6

This comparative example is basically the same as Example 1, the difference is that the polybutadiene-styrene copolymer (a water-based polymer known to be used in the art) is used to replace the polyethylene in Example 1 during the preparation of the cathode plate of this comparative example. - Lithium acrylate.

The cathode electrode sheets of Examples 1-20 and Comparative Examples 1-6 were subjected to cathode active layer thickness test, cathode active layer adhesion test, cathode active layer TG-MS test and cathode active layer fold-off powder test. The test results are shown in Table 1.

The lithium ion batteries of Examples 1-20 and Comparative Examples 1-6 were subjected to a discharge rate test and a 25°C cycle performance test. The test results are shown in Table 1.

The test method is as follows:

Cathode active layer thickness test: measure the thickness of aluminum foil, take 3 pieces of aluminum foil with a size of 100*100mm, use a micrometer to test the thickness of each piece of aluminum foil, and test 10 points evenly for each pole piece, and take the average value of the thickness as the thickness of the aluminum foil; For thickness measurement, take 3 pole pieces (including aluminum foil) with a size of 100*100mm, measure the thickness of each pole piece with a micrometer, test 10 points evenly for each pole piece, and take the average value of the thickness as the thickness of the pole piece; For the thickness of the cathode active layer, the thickness of the cathode active layer is obtained by subtracting the thickness of the aluminum foil from the thickness of the above-mentioned pole piece.

Adhesion test of the cathode active layer: Cut the coated cathode pole piece into a spline with a length and width of 100mm*10mm, compound the green glue with one side of the cathode active layer, and then use a tensile machine to peel off the green glue and aluminum foil. , the peeling angle is 180 degrees, the test speed is 50 mm/min, 5 samples are tested in parallel, and the average value is taken as the adhesive force of the cathode active layer.

Cathode active layer TG-MS test: scrape the coated cathode active layer from the cathode pole piece with a blade, carry out TG-MS test, the test temperature is 25 ~ 500 ℃, and then use mass spectrometer to analyze the main components of the generated gas, The ratio of the main flexible monomers (ethylene monomer and/or propylene monomer) in the cracked product to the total weight of the monomers in the cracked product is obtained.

Cathode active layer folded powder test: fold the coated cathode electrode piece along one side of the cathode active layer at 180 degrees, visually observe the detachment of the cathode active layer from the aluminum foil, and classify the detachment of the cathode active layer into no powder, Flaking and severe flaking.

Lithium-ion battery discharge rate test: Take three lithium-ion batteries of Examples 1-20 and Comparative Examples 1-6, charge them to a preset voltage at a constant current rate of 0.5C at room temperature, and then keep them at the preset voltage with constant current. It is charged to 0.05C, and then discharged with a discharge current of 2C to test its discharge capacity, and the ratio of the discharge capacity to the capacity obtained by a discharge current of 0.5C is recorded as its 2C discharge rate.

Lithium-ion battery cycle performance (capacity retention rate) test at 25°C: Take 3 lithium-ion batteries of Example 1-20 and Comparative Example 1-6, and charge them to a preset value at a constant current rate of 0.5C at 25°C voltage, and then constant voltage charging to 0.05C under the preset voltage to obtain the initial capacity of the cell. The cycle process is as follows: discharge at a discharge current of 0.5C to 2.5V, then charge at a constant current rate of 0.5C to a preset voltage, and then charge at a constant voltage to 0.05C at a preset voltage, and then repeat the above process 1000 times, the The remaining capacity of the three lithium-ion batteries is averaged to obtain the final capacity, and then divided by the initial capacity to obtain the capacity retention rate.

Among them, in the lithium ion battery discharge rate test and the 25 ℃ cycle performance test, the charging cut-off voltage used in the test of the lithium ion battery (lithium iron phosphate battery) in Examples 1 and 7-20 was 3.65V, and in Examples 2 and 4 The charging cut-off voltage adopted during the test of the lithium ion battery (lithium manganate battery, lithium manganate+lithium iron phosphate battery) was 4.25V, and the charging cut-off voltage adopted during the test of the lithium ion battery (lithium manganese iron phosphate battery) of Example 3 The voltage is 4.5V, and the charging cut-off voltage used in the test of the lithium ion batteries (nickel-cobalt-manganese ternary battery, nickel-cobalt-aluminum ternary battery) of Examples 5-6 is 4.35V.

Table I:

It can be seen from Table 1 that:

The aqueous cathode active layers of Examples 1-12 and 15-20 can achieve the same or even better adhesion than the oily cathode active layers of Comparative Examples 1-4, and the powder cannot be folded in half.

The lithium-ion batteries of Examples 1-12 and 15-20 can achieve the same or even better discharge rate test and 25°C cycle performance than the lithium-ion batteries of Comparative Examples 1-4.

Compared with the water-based cathode active layers of Examples 1 and 7-12, the water-based cathode active layers of Examples 13-14 had poor adhesion, and the powder fell off even after being folded in half. The reason may be that Example 13 The addition amount of the water-based flexible polymer of -14 is too small, so that the adhesive force and toughness of the cathode active layer are insufficient.

Compared with the aqueous cathode active layers of Comparative Examples 5-6, the aqueous cathode active layers of Examples 1-12 and 15-20 had better adhesion, and did not drop powder after folding in half. The fact that no powder falls off after folding in half proves that the cathode active layer prepared from the aqueous cathode slurry of the present application has good toughness.

The water-based cathode slurry, cathode electrode sheet and lithium ion battery provided by the embodiments of the present application have been described in detail above. The principles and implementations of the present application are described with specific examples. The descriptions of the above embodiments are only used for In order to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation and application scope. In summary, the content of this specification It should not be construed as a limitation of this application.

Claims (12)

1. an aqueous cathode slurry, it is characterized in that: comprise cathode active material, aqueous polymer, conductive agent, aqueous dispersion agent and water, comprise flexible group in described aqueous polymer, and described flexible group is selected from ethylene at least one of a group and a propenyl group. 2 . The aqueous cathode slurry according to claim 1 , wherein the aqueous cathode slurry is composed of the cathode active material, the aqueous polymer, the conductive agent, the aqueous dispersant and water. 3 . . 3. The aqueous cathode slurry according to claim 1 or 2, characterized in that: The content of the solid component in the aqueous cathode slurry is greater than or equal to 30 wt % and less than or equal to 95 wt %; and/or Based on the total mass of the solid components in the aqueous cathode slurry, the content of the aqueous polymer is 1-10 wt %, the content of the aqueous dispersant is 0.1-3 wt %, and the content of the conductive agent is 0.5 wt % ~10wt%, the content of the cathode active material is 77-98.4wt%. 4. The aqueous cathode slurry according to claim 1 or 2, wherein the aqueous polymer is selected from at least one of vinyl polymers and propylene-based polymers. 5. The aqueous cathode slurry of claim 4, wherein: The vinyl polymer is at least one selected from the group consisting of copolymers of ethylene and esters, copolymers of ethylene and acrylic acid, and copolymers of ethylene and acrylates; and/or The propylene-based polymer is selected from at least one of a copolymer of polypropylene and maleic anhydride, a copolymer of polypropylene and maleic acid, and a polypropylene maleate copolymer. 6. The aqueous cathode slurry of claim 5, wherein: The copolymer of ethylene and ester is selected from at least one of ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-methyl acrylate copolymer; and/or The copolymer of ethylene and acrylic acid is selected from at least one of ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer; and/or The copolymer of ethylene and acrylate is selected from at least one of polyethylene-acrylate and polyethylene-methacrylate, wherein the polyethylene-acrylate is selected from polyethylene-acrylate sodium salt, polyethylene At least one of ethylene-acrylic acid lithium salt, polyethylene-acrylic acid potassium salt, polyethylene-acrylic acid ammonium salt, and polyethylene-acrylic acid amine salt, the polyethylene-methacrylic acid salt is selected from polyethylene-methyl acrylate At least one of acrylic acid sodium salt, polyethylene-methacrylic acid lithium salt, polyethylene-methacrylic acid potassium salt, and polyethylene-methacrylic acid ammonium salt, polyethylene-methacrylic acid amine salt; and/or The copolymer of polypropylene and maleic anhydride is selected from polypropylene-maleic anhydride copolymers; and/or The copolymer of polypropylene and maleic acid is at least one selected from polypropylene-maleic acid copolymer and polypropylene-ethylene-maleic acid copolymer; and/or The polypropylene maleate copolymer is selected from at least one of polypropylene-maleate and polypropylene-ethylene-maleate, wherein the polypropylene-maleate is selected from the group consisting of At least one of propylene-maleic acid potassium salt, polypropylene-maleic acid lithium salt, polypropylene-maleic acid sodium salt, polypropylene-maleic acid ammonium salt, and polypropylene-maleic acid amine salt , the polypropylene-ethylene-maleate is selected from polypropylene-ethylene-maleate potassium salt, polypropylene-ethylene-maleate lithium salt, polypropylene-ethylene-maleate sodium salt, polypropylene- At least one of ethylene-maleic acid ammonium salt and polypropylene-ethylene-maleic acid amine salt. 7 . The aqueous cathode slurry according to claim 1 or 2 , wherein the molecular weight of the aqueous polymer is 1×10 ⁴ to 1000×10 ⁴ . 8. The aqueous cathode slurry according to claim 1 or 2, wherein: The cathode active material is selected from at least one of lithium iron phosphate, lithium manganate, lithium iron manganese phosphate, nickel-cobalt-manganese ternary material, and nickel-cobalt-aluminum ternary material; and/or The conductive agent is selected from at least one of carbon black, graphite, carbon fiber, and carbon nanotubes; and/or The aqueous dispersant is selected from sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyvinyl pyrrolidone, hydroxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyacrylic acid , polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyacrylic acid-acrylonitrile copolymer, polyacrylic acid-acrylate-acrylonitrile copolymer, methacrylic acid-acrylonitrile copolymer, acrylate - at least one of acrylonitrile copolymer, methacrylate-acrylonitrile copolymer, polyacrylate-acrylate-acrylonitrile copolymer, and polymethacrylate-acrylate-acrylonitrile copolymer. 9. A cathode electrode sheet, comprising a cathode current collector and a cathode active layer combined on at least one surface of the cathode current collector, wherein the cathode active layer is made of any one of claims 1 to 8. prepared from an aqueous cathode slurry. 10. cathode pole piece as claimed in claim 9, is characterized in that: described cathode active layer adopts thermogravimetric mass spectrometry in the cracked product after cracking, ethylene monomer and/or propylene monomer account for the monomer in cracked product. 5 to 95% of the total weight. 11. The cathode electrode sheet according to claim 9, wherein the cathode active layer comprises a cathode active material, an aqueous polymer, an aqueous dispersant and a conductive agent, and in the cathode active layer, the aqueous polymer The content of the material is 1-10wt%, the content of the aqueous dispersant is 0.1-3wt%, the content of the conductive agent is 0.5-10wt%, and the content of the cathode active material is 77-98.4wt%. 12 . A lithium ion battery, characterized in that: the lithium ion battery comprises the cathode electrode piece according to any one of claims 9 to 11 .