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CN-122011291-A - Water-based polyurethane-acrylate composite emulsion with core-shell structure, and preparation method and application thereof

CN122011291ACN 122011291 ACN122011291 ACN 122011291ACN-122011291-A

Abstract

The invention discloses a water-based polyurethane-acrylic ester composite emulsion with a core-shell structure, and a preparation method and application thereof. The composite emulsion is prepared by sequentially carrying out seed emulsion polymerization on a component A, a component B and a component C, wherein the component A is formed into a core part by double-bond end-capped aqueous polyurethane, the component B is formed into an inner shell part by copolymerization of components comprising, by mass, 20-30 parts of fluorine-containing acrylate monomers, 10-20 parts of alkyl acrylate monomers with 4-18 carbon atoms, 0.15-0.25 part of a first initiator and 0.5-3 parts of a first emulsifier, and the component C is formed into an outer shell part by copolymerization of components comprising, by mass, 30-60 parts of acrylic acid monomers, 20-40 parts of acrylamide monomers, 10-30 parts of hydroxy acrylate monomers, 0.3-0.65 part of a second initiator and 0.5-3 parts of a second emulsifier. The composite emulsion can effectively overcome the defects of insufficient electrolyte swelling resistance and insufficient high-voltage oxidation resistance in the application of high-voltage lithium ion batteries, and can effectively improve the cycle performance of the batteries.

Inventors

  • LIU ZIHAO
  • WU CHAOSEN
  • Pan Linyan
  • Qi Yanchunxiao
  • YANG DONGFANG

Assignees

  • 惠州普赛达新材料有限公司

Dates

Publication Date
20260512
Application Date
20260310

Claims (10)

  1. 1. The aqueous polyurethane-acrylate composite emulsion with the core-shell structure is characterized by being prepared by sequentially carrying out seed emulsion polymerization on a component A, a component B and a component C, wherein the component A is formed by capping aqueous polyurethane with double bonds to form a core part, the component B is formed by copolymerizing 20-30 parts by mass of fluorine-containing acrylate monomers, 10-20 parts by mass of alkyl acrylate monomers with 4-18 carbon atoms, 0.15-0.25 part by mass of first initiator and 0.5-3 parts by mass of first emulsifier, and the component C is formed by copolymerizing 30-60 parts by mass of acrylic acid monomers, 10-40 parts by mass of acrylamide monomers, 10-30 parts by mass of hydroxy acrylate monomers, 0.3-0.65 part by mass of second initiator and 0.5-3 parts by mass of second emulsifier; The mass ratio of the component A to the component B to the component C is 100:30-55:50-135.
  2. 2. The aqueous polyurethane-acrylate composite emulsion with core-shell structure according to claim 1 wherein the fluoroacrylate monomer is selected from at least one of trifluoroethyl methacrylate, hexafluorobutyl acrylate, dodecafluoroheptyl methacrylate.
  3. 3. The aqueous polyurethane-acrylate composite emulsion with a core-shell structure according to claim 1, wherein the alkyl acrylate monomer with 4-18 carbon atoms is at least one selected from lauryl acrylate and stearyl acrylate.
  4. 4. The aqueous polyurethane-acrylate composite emulsion having a core-shell structure according to claim 1 wherein said hydroxy acrylate monomer is selected from at least one of hydroxyethyl acrylate and hydroxyethyl methacrylate.
  5. 5. The aqueous polyurethane-acrylate composite emulsion having a core-shell structure according to claim 1 wherein the first initiator and the second initiator are each independently selected from at least one of ammonium persulfate, sodium persulfate, and potassium persulfate, and the first emulsifier and the second emulsifier are each independently selected from at least one of ammonium nonylphenol polyoxyethylene ether sulfate, sodium dodecyl benzene sulfonate, and sodium fatty alcohol polyoxyethylene ether sulfate.
  6. 6. The method for preparing the aqueous polyurethane-acrylate composite emulsion with the core-shell structure according to any one of claims 1 to 5, which is characterized by comprising the following steps: (1) Uniformly mixing the fluorinated acrylate monomer, the alkyl acrylate monomer with the carbon number of 4-18 and the first emulsifier in deionized water to obtain a first pre-emulsion, uniformly mixing the acrylic acid monomer, the acrylamide monomer, the hydroxyacrylate monomer and the second emulsifier in deionized water to obtain a second pre-emulsion, dissolving the first initiator in deionized water to form a first initiator aqueous solution, and dissolving the second initiator in deionized water to form a second initiator aqueous solution to provide double-bond-terminated aqueous polyurethane seed emulsion; (2) Adding a first initiator aqueous solution into the double-bond capped aqueous polyurethane seed emulsion, and dropwise adding the first pre-emulsion to perform polymerization reaction to obtain a primary composite emulsion with a core-shell structure; (3) And adding a second initiator aqueous solution into the primary composite emulsion, and dropwise adding the second pre-emulsion to perform polymerization reaction to obtain the aqueous polyurethane-acrylate composite emulsion with the core-shell structure.
  7. 7. The method for preparing the aqueous polyurethane-acrylate composite emulsion with the core-shell structure according to claim 6, wherein in the step (1), the double bond end-capped aqueous polyurethane seed emulsion is prepared by reacting polyol and diisocyanate under the condition of a catalyst to obtain a prepolymer, sequentially adding a carboxyl-containing hydrophilic chain extender to carry out chain extension, and end-capping a hydroxyl-containing and alkenyl-containing monomer, and neutralizing and emulsifying.
  8. 8. The method for preparing a core-shell structured aqueous polyurethane-acrylate composite emulsion according to claim 6, wherein in the step (3), the pH of the reaction solution is adjusted to 7.5-8.5 by using a lithium base reagent after the polymerization reaction.
  9. 9. Use of the aqueous polyurethane-acrylate composite emulsion with a core-shell structure according to any one of claims 1 to 5 or the composite emulsion prepared by the preparation method of the aqueous polyurethane-acrylate composite emulsion with a core-shell structure according to any one of claims 6 to 8 in preparation of lithium ion battery electrodes.
  10. 10. The use according to claim 9, wherein the electrode is a positive electrode and the active material of the positive electrode is a lithium transition metal oxide having an operating voltage of not less than 4.4V.

Description

Water-based polyurethane-acrylate composite emulsion with core-shell structure, and preparation method and application thereof Technical Field The invention relates to the technical field of lithium ion battery materials, in particular to an aqueous adhesive for a lithium ion battery electrode, especially a high-voltage positive electrode, and a preparation method thereof, and especially an aqueous polyurethane-acrylate composite emulsion with a core-shell structure, and a preparation method and application thereof. Background With the rapid development of new energy automobiles and large-scale energy storage markets, higher requirements are put on the energy density, the cycle life and the safety of lithium ion batteries. The use of high capacity, high operating voltage positive electrode materials (e.g., high nickel ternary materials NCM811, NCM90505, and lithium-rich manganese-based materials, etc.) is one of the key paths for improving the energy density of batteries. However, the operating voltages of these positive electrode materials are typically as high as 4.4V and above, which poses serious challenges for battery internal materials, particularly adhesives. Currently, the adhesives widely used in the manufacture of lithium ion battery anodes mainly comprise oil-based polyvinylidene fluoride and traditional aqueous adhesives. PVDF and its limitation that PVDF needs to use toxic N-methyl pyrrolidone as solvent has the problems of high cost, large environmental pollution, poor ionic conductivity and the like. More importantly, PVDF relies on weaker van der waals forces for bonding, is easily oxidized at high voltages, and has limited resistance to electrolyte swelling, which can easily lead to failure of the electrode structure in long-term cycling. The traditional aqueous adhesive and the limitation thereof are that aqueous adhesives such as styrene-butadiene rubber, polyacrylic acid and salts thereof are paid attention to in terms of environmental protection, low cost and strong binding power. In particular, the polyacrylic acid adhesive has rich carboxyl groups, can form strong hydrogen bonds and ionic bonds with the surface of the positive electrode active material, and has excellent adhesive property. However, they also face the bottleneck that electrolyte swelling resistance is poor, and a large number of polar groups on the polymer chain are liable to interact with carbonate electrolyte solvents, resulting in swelling and softening of the adhesive film, decrease in cohesive strength and modulus, and failure to effectively restrain the active material, thereby causing pulverization of the electrode structure. Under the high voltage environment, the cathode material with strong oxidizing property can attack and degrade chemical bonds such as C-H, C-C in the molecular chain of the adhesive, so that the adhesive is invalid, the interface impedance is rapidly increased, and the battery capacity is rapidly attenuated. Polyacrylic acid-based adhesives are generally hard and brittle, and it is difficult to effectively buffer stress generated by volume changes of active particles during charge and discharge. To overcome the shortcomings of single materials, researchers have developed composite adhesives, such as aqueous polyurethane-acrylate composite emulsions. The aqueous polyurethane has good flexibility and strong acrylic ester binding power, and the advantages of the aqueous polyurethane and the acrylic ester can be complemented by each other. However, existing compounding techniques are often limited to simple physical blending or random copolymerization, or simple single layer core-shell structures. The structure can not accurately regulate and control the interface performance and realize the functional partition, and has obvious defects that the compatibility of the simply blended two phases is poor, the phase separation is easy to occur, and the performance is uneven. While the two-phase compatibility is improved by the simple core-shell structure (e.g., WPU as core and PAA as shell), the flexible WPU core is still susceptible to swelling and oxidation when directly exposed to harsh electrolyte environments, and the stiffness of the PAA shell may initiate microcracks at the interface due to modulus mismatch. Therefore, there is an urgent need in the art for a novel aqueous adhesive that can not only maintain high strength binding and ion conductivity, but also fundamentally improve the stability of electrolyte corrosion resistance and high pressure oxidation resistance, thereby meeting the long life requirements of next generation high energy density lithium ion batteries. Disclosure of Invention In view of the above problems, the present invention aims to provide an aqueous polyurethane-acrylate composite emulsion with a core-shell structure, and a preparation method and application thereof, wherein the aqueous polyurethane-acrylate composite emulsion with a core-shell structure can effective