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CN-121991433-A - Polypropylene composite current collector special film and preparation method thereof

CN121991433ACN 121991433 ACN121991433 ACN 121991433ACN-121991433-A

Abstract

The invention relates to the field of special films, in particular to a special film of a polypropylene composite current collector and a preparation method thereof. The special film is used as a supporting base film of a composite current collector and comprises, by weight, 100 parts of high-crystalline polypropylene resin, 8-15 parts of a composite modifier, 5-10 parts of hydroxylated boron nitride, 8-12 parts of a compatilizer, 0.5-1 part of an antioxidant, 0.3-0.5 part of a light stabilizer and 0.3-0.6 part of a lubricant. The special film prepared by the invention has high mechanical strength, excellent heat resistance and flame retardance, insulation stability, dimensional stability and high binding force with a metal coating, has good film thickness uniformity and high surface smoothness, can be used as a support base film of a composite current collector, and effectively improves the cycle life, safety and energy density of a lithium battery.

Inventors

  • WANG RUNXIAO
  • XIA JINGJING
  • ZHUANG ZHI
  • CHEN HUAIYU
  • WANG FENG
  • WANG YONGJUN

Assignees

  • 扬州博恒新能源材料科技有限公司

Dates

Publication Date
20260508
Application Date
20260304

Claims (10)

  1. 1. The special film for the polypropylene composite current collector is characterized by being used as a supporting base film of the composite current collector and comprising the following components in parts by weight: 100 parts of high-crystalline polypropylene resin, 8-15 parts of composite modifier, 5-10 parts of hydroxylated boron nitride, 8-12 parts of compatilizer, 0.5-1 part of antioxidant, 0.3-0.5 part of light stabilizer and 0.3-0.6 part of lubricant.
  2. 2. The special film for a polypropylene composite current collector according to claim 1, wherein the crystallinity of the high crystalline polypropylene resin is more than 70%, and the melt index is 2-8g/10min at 230 ℃ and 2.16 kg.
  3. 3. The special film for the polypropylene composite current collector according to claim 1, wherein the preparation method of the composite modifier comprises the following steps: S1, adding 1, 5-naphthalene diisocyanate and N-methylpyrrolidone into a flask under continuous nitrogen flow, adding a catalyst at the same time, heating the flask to 80-90 ℃ in an oil bath, stirring until the mixture is completely dissolved, rapidly adding 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, preserving heat and stirring vigorously, and continuously reacting for 3-5 hours to obtain a phosphorus-containing prepolymer solution; s2, dissolving 5-aminobenzotriazole in N-methylpyrrolidone, dropwise adding the N-methylpyrrolidone into a prepolymer solution, heating to 95-115 ℃ after the dropwise adding is finished, stirring and reacting for 5-7h, precipitating, washing and drying after the reaction is finished, grinding and sieving to obtain the composite modifier.
  4. 4. A special film for a polypropylene composite current collector according to claim 3, wherein the mass ratio of 1, 5-naphthalene diisocyanate, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 5-aminobenzotriazole is 5.00:4.14-4.48:2.32-2.76.
  5. 5. The special polypropylene composite current collector film according to claim 3, wherein the catalyst is dibutyl tin dilaurate, and the addition amount is 0.5-1.5% of the mass of the 1, 5-naphthalene diisocyanate.
  6. 6. The special film for the polypropylene composite current collector, according to claim 1, wherein the preparation method of the hydroxylated boron nitride comprises the following steps: Mixing nanoscale boron nitride powder with sodium hydroxide solution, pouring into a hydrothermal reaction kettle, reacting for 6-10h at 160-200 ℃, cooling, filtering, washing with water to neutrality, and vacuum drying to obtain hydroxylated boron nitride.
  7. 7. The special polypropylene composite current collector film according to claim 1, wherein the compatilizer is maleic anhydride grafted polypropylene, the grafting rate is 1-1.5%, and the melt index MFR is 6-12g/10min under the conditions of 230 ℃ and 2.16 kg.
  8. 8. The special polypropylene composite current collector film according to claim 1, wherein the antioxidant comprises a main antioxidant and an auxiliary antioxidant in a mass ratio of 2:1, wherein the main antioxidant is antioxidant 1010 or antioxidant 1076, and the auxiliary antioxidant is antioxidant 168 or antioxidant 810.
  9. 9. The special film for the polypropylene composite current collector according to claim 1, wherein the light stabilizer is a hindered amine light stabilizer, specifically a light stabilizer 770 or a light stabilizer 944, and the lubricant is at least one of polyethylene glycol monostearate, calcium stearate, magnesium stearate and ethylene bis stearamide.
  10. 10. A method for preparing the special film of the polypropylene composite current collector, which is characterized by comprising the following steps: step 1, drying the raw materials, adding high-crystalline polypropylene resin, a composite modifier and hydroxylated boron nitride into a high-speed mixer, and uniformly mixing to obtain premix; step 2, mixing the premix and other auxiliary materials, putting the mixture into a double-screw extruder, and carrying out melt blending extrusion granulation to obtain master batch; And 3, putting the master batch into a casting film machine, and preparing a base film through melting, casting and cooling shaping to obtain the finished polypropylene composite current collector special film.

Description

Polypropylene composite current collector special film and preparation method thereof Technical Field The invention relates to the field of special films, in particular to a special film of a polypropylene composite current collector and a preparation method thereof. Background With the rapid iteration of new energy automobiles, portable electronic devices and large-scale energy storage systems, lithium ion batteries have increasingly stringent requirements on energy density, safety performance and cost control. The current collector is used as a core component for bearing active substances and collecting and transmitting current in the battery, and the performance of the current collector directly determines the overall performance and service life of the battery. The traditional current collector adopts pure metal foil (positive aluminum foil and negative copper foil), but has the inherent defects of high metal density, obviously increased overall weight of the battery, restricted energy density improvement, limited mechanical toughness of the metal foil, easy internal short circuit caused by electrode particle puncture, potential safety hazard, and high price fluctuation of metal raw materials, so that the production cost of the battery is high. In order to solve the problems, the composite current collector technology has developed, a high polymer film is used as a middle supporting base film, a metal layer is deposited on the surface of the composite current collector, and the composite current collector has the advantages of low density, high tensile strength and strong puncture resistance, can effectively delay short circuit risk, and improves the safety of a battery. Polypropylene (PP) is one of ideal candidate materials for composite current collector base films due to the characteristics of low density, low cost, excellent chemical stability resistance, good processing fluidity and the like. However, the polypropylene base film has the following technical problems in practical application that (1) in order to enhance the energy density of a battery, the thickness of the base film needs to be reduced to below 20 mu m, but the crystallinity of the PP itself is higher, the flexibility of a molecular chain is strong, the mechanical strength is obviously attenuated after thinning, and the mechanical requirements of the subsequent metal deposition and battery assembly process cannot be met, (2) the PP molecular chain is nonpolar, the surface energy is low, the chemical inertness is strong, the interfacial compatibility with a metal layer is poor, the adhesion force is weak after depositing the metal layer, stripping and falling easily occur in the battery charge-discharge cycle and temperature change process, and (3) the glass transition temperature and the thermal deformation temperature of the PP are low, the thermal stability is insufficient, the difference between the PP and the thermal shrinkage difference between the PP and the metal layer is obvious, the PP is easy to curl and warp due to internal stress in the high-temperature processing or the battery working process, and even interlayer separation is poor, and the PP is easy to age degradation in the long-term service process of the battery and the service life of a current collector is affected. Therefore, a special modified polypropylene film needs to be developed, and on the basis of keeping the light weight, low cost advantage and thinner characteristics of the PP, the mechanical strength, the binding force with a metal layer and the high-temperature resistance stability of the PP are synchronously improved, so that the large-scale application of the high-performance composite current collector is promoted, and the core requirements of a new energy device on high energy density and high safety are met. Disclosure of Invention Aiming at the problems existing in the prior art, the invention aims to provide a polypropylene composite current collector special film and a preparation method thereof. The aim of the invention is realized by adopting the following technical scheme: The invention provides a polypropylene composite current collector special film which is used as a support base film of a composite current collector and comprises the following components in parts by weight: 100 parts of high-crystalline polypropylene resin, 8-15 parts of composite modifier, 5-10 parts of nano modified filler, 8-12 parts of compatilizer, 0.5-1 part of antioxidant, 0.3-0.5 part of light stabilizer and 0.3-0.6 part of lubricant. Preferably, the high crystalline polypropylene resin has a crystallinity of greater than 70% and a melt index of 2 to 8g/10min at 230 ℃ and 2.16 kg. More preferably, the high crystalline polypropylene resin is of the brand medium petrochemical PPH-Y35, a density of 0.902g/cm 3, a crystallinity of 75%, a melt index mfr=3.5 g/10min (230 ℃,2.16 kg). Preferably, the preparation method of the composite modifier comprises the following