CN-121975476-A - Positive electrode composite adhesive and preparation method thereof

Abstract

The invention provides a positive electrode composite adhesive and a preparation method thereof, and relates to the technical field of positive electrode adhesives. The positive electrode composite adhesive comprises 20-40% of anionic waterborne polyurethane resin with a polycarbonate type soft segment, 10-25% of maleic anhydride grafted polyolefin elastomer, 5-15% of conductive nano particles, 1-5% of polycarboxylate type anionic dispersing agent, 0.5-3% of thickener and the balance of deionized water. The invention adopts a water-based fluorine-free system, has the advantages of environmental protection and high safety, realizes chemical bonding and elastic buffering by utilizing the maleic anhydride grafted polyolefin elastomer, effectively prevents the pole piece from cracking and improves the bonding strength, combines the corrosion-resistant polycarbonate polyurethane and the conductive nano particles, ensures the stability of electrolyte resistance, builds a high-efficiency conductive network, and remarkably improves the cycle life and the multiplying power performance of the battery.

Inventors

• Lu yajie
• ZHU HUAJUN
• WANG ZHENGWEI
• XU JING
• Shao Panrun
• GONG QIANG
• SHI YUNHUI
• WANG HAIMING

Assignees

• 星恒电源股份有限公司

Dates

Publication Date

20260505

Application Date

20260206

Claims (10)

1. 1. The positive composite adhesive is characterized by comprising, by mass, 20% -40% of an anionic aqueous polyurethane resin with a polycarbonate type soft segment, 10% -25% of a maleic anhydride grafted polyolefin elastomer, 5% -15% of conductive nano particles, 1% -5% of a polycarboxylate type anionic dispersing agent, 0.5% -3% of a thickening agent and the balance of deionized water.
2. 2. The positive electrode composite binder according to claim 1, wherein the maleic anhydride-grafted polyolefin elastomer is at least one selected from the group consisting of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene and maleic anhydride-grafted ethylene-octene copolymer, and/or, The grafting rate of the maleic anhydride grafted polyolefin elastomer is 1% -5%, and/or, The soft segment is polycarbonate type anion water-based polyurethane resin, the number average molecular weight of the resin is 50000-150000, and the molecular chain is provided with carboxylate ions or sulfonate ions, and/or, The conductive nano particles are selected from at least one of graphene, carbon nano tubes and nano carbon black, and/or, The particle size of the conductive nano particles is 10 nm-100 nm, and/or, The polycarboxylate type anionic dispersant is selected from polycarboxylate ammonium salt or polycarboxylate sodium salt.
3. 3. A method of preparing the positive electrode composite adhesive according to claim 1 or 2, comprising: adding the anionic water-based polyurethane resin with the soft segment of polycarbonate into deionized water for first stirring treatment to obtain a resin solution; adding the maleic anhydride grafted polyolefin elastomer into the resin solution for second stirring treatment to obtain mixed emulsion; premixing the conductive nano particles and the polycarboxylate anionic dispersing agent, and then adding the conductive nano particles and the polycarboxylate anionic dispersing agent into the mixed emulsion for ultrasonic dispersion; And adding the thickener to regulate the viscosity to obtain the positive electrode composite adhesive.
4. 4. The method for preparing a positive electrode composite adhesive according to claim 3, wherein the rotation speed of the first stirring treatment is 300r/min to 500r/min, the stirring time is 10min to 20min, and/or, The rotation speed of the second stirring treatment is 800-1000 r/min, the stirring time is 30-40 min, the Zeta potential of the obtained mixed emulsion is-30 mV-40 mV, and/or, The power of ultrasonic dispersion is 1000-1500W, and the treatment time is 20-30 min.
5. 5. The positive electrode plate is characterized by comprising a current collector and an electrode material layer coated on the current collector; the electrode material layer includes a positive electrode active material and a conductive agent, and the positive electrode composite adhesive according to claim 1 or 2, or the positive electrode composite adhesive prepared by the method for preparing a positive electrode composite adhesive according to claim 3 or 4.
6. 6. The positive electrode sheet according to claim 5, wherein the positive electrode active material comprises at least one of LiNi x Co y Mn (1-x-y) O 2 、LiFePO 4 、LiCoO 2 and LiMn 2 O 4 , wherein 0< x <1,0< y <1, x+y <1.
7. 7. The positive electrode sheet according to claim 5, wherein the positive electrode active material comprises NaCoO 2 、NaNi x Co y Mn (1-x-y) O 2 、Na 3 V 2 (PO 4 ) 3 , wherein 0< x <1,0< y <1, x+y <1.
8. 8. The positive electrode sheet according to claim 5, wherein the electrode material layer comprises 80% -95% of positive electrode active material, 1% -10% of conductive agent, and 1% -10% of positive electrode composite adhesive.
9. 9. A battery comprising the positive electrode sheet according to any one of claims 5 to 8.
10. 10. An electrical device comprising the battery of claim 9.

Description

Positive electrode composite adhesive and preparation method thereof Technical Field The invention relates to the technical field of positive electrode adhesives, in particular to a positive electrode composite adhesive and a preparation method thereof. Background Secondary batteries, such as lithium ion batteries and sodium ion batteries, have been widely used in the fields of portable electronic devices, electric vehicles, energy storage systems, and the like, by virtue of their high energy density, long cycle life, and the like. The positive electrode is used as a core component of the secondary battery, and the performance of the positive electrode directly determines key indexes such as energy density, cycle stability, rate capability and the like of the battery. The positive electrode sheet is generally composed of a positive electrode active material, a conductive agent, an adhesive and a current collector, wherein the adhesive has the main function of firmly adhering positive electrode active material particles and the conductive agent together and tightly adhering the positive electrode active material particles and the conductive agent to the surface of the current collector so as to construct a stable electrode structure and good electron and ion conduction paths. Therefore, the performance of the binder is critical to the overall performance of the secondary battery. Currently, positive electrode adhesives widely used in the industry mainly include oily adhesives such as polyvinylidene fluoride (PVDF), and aqueous adhesives such as a small amount of polyacrylic acid (PAA) and sodium carboxymethyl cellulose (CMC). Among them, PVDF is the positive electrode adhesive material which is dominant at present because of having better electrochemical stability and mechanical properties. However, conventional PVDF adhesives still face a number of technical bottlenecks in practical applications. First, PVDF typically requires the use of N-methylpyrrolidone (NMP) as a solvent, which is toxic and volatile, not only increasing the environmental processing costs in the production process, but also presents health risks. Secondly, PVDF belongs to a rigid high polymer material, the elastic modulus is higher, and positive electrode active substances often accompany obvious volume expansion and shrinkage in the charge and discharge process, so that the stress generated by the volume change is difficult to effectively buffer, and the pole piece coating is easy to crack or fall off from a current collector, thereby shortening the service life of the battery. Furthermore, PVDF itself is an insulating material, and its distribution in the electrode increases interfacial resistance to some extent, which is detrimental to the performance of the battery rate. In addition, the PVDF molecular structure contains fluorine element, and when the battery is subjected to thermal runaway under the extreme abuse condition, the PVDF molecular structure is easy to decompose to generate highly toxic corrosive gases such as Hydrogen Fluoride (HF) and the like, so that serious potential safety hazards exist. In order to overcome the defects of the organic solvent system, although a part of aqueous adhesive systems are developed in the industry, water is used as a dispersion medium to improve the environmental protection. However, the existing aqueous adhesive generally has the problem that the electrolyte resistance stability and the bonding flexibility are difficult to be combined. For example, some aqueous resins tend to swell under electrolyte immersion, leading to adhesive failure, or while chemically stable, lack sufficient elasticity to accommodate the volumetric effects of high energy density materials. Therefore, there is a need to develop a high-safety positive electrode composite adhesive system capable of simultaneously satisfying the development requirements of high-performance secondary batteries, which is environment-friendly, high in adhesive strength, excellent in elastic buffer capacity, good in electrical conductivity, and free of fluorine. In view of this, the present invention has been made. Disclosure of Invention The invention aims to provide a positive electrode composite adhesive and a preparation method thereof, wherein the positive electrode composite adhesive is constructed through a water-based fluorine-free formula, chemical bonding toughening and a conductive network, so that the comprehensive improvement of the positive electrode adhesive in environmental protection, safety, adhesive strength, elastic buffering, electrolyte resistance, stability and conductivity is realized. In order to achieve the above object of the present invention, the following technical solutions are specifically adopted: in the first aspect, the invention provides a positive electrode composite adhesive, which comprises, by mass, 20% -40% of an anionic aqueous polyurethane resin with a polycarbonate type soft segment, 10% -25% of