Electrolyte swelling resistant elastomer cable and preparation method thereof

Abstract

The invention relates to an electrolyte swelling resistant elastomer cable and a preparation method thereof, and belongs to the technical field of cables. The cable comprises a conductor and a sheath layer, the sheath layer is made of a composite material, and the composite material comprises, by weight, 100 parts of an acrylate rubber matrix, 5-30 parts of a nano filler, 0.5-8 parts of an ionic liquid containing a crosslinkable functional group, 1-5 parts of a vulcanizing agent, 0.5-3 parts of a vulcanizing aid, and 0.5-2 parts of an anti-aging agent. Wherein the ionic liquid is combined on the surface of the nano filler. According to the invention, the ionic liquid containing the cross-linkable functional group is combined on the surface of the nano-filler, and then is blended and vulcanized with the acrylate rubber matrix, so that the cross-linkable functional group of the ionic liquid is covalently crosslinked with the rubber matrix, and the obtained cable has excellent electrolyte swelling resistance and stability.

Description

Technical Field

[0001] This invention belongs to the field of cable technology and relates to an electrolyte-resistant elastomeric cable and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles and grid energy storage technologies, the safety and reliability of lithium-ion battery energy storage systems have become a focus of industry attention. The internal connecting cables of energy storage systems are constantly exposed to a complex chemical environment, particularly facing the potential risk of electrolyte leakage. Lithium-ion battery electrolytes are mainly composed of highly polar carbonate organic solvents such as ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), as well as lithium salts, which have extremely strong swelling and corrosive effects on common polymer materials. Traditional cable sheath materials such as polyvinyl chloride, neoprene rubber, and thermoplastic polyurethane are prone to severe swelling in such environments, leading to a sharp decline in mechanical properties, insulation rupture, and even short circuits and thermal runaway accidents.

[0003] To address the aforementioned issues, several improvements have been proposed in existing technologies. For example, highly oil-resistant materials such as fluororubber (FKM) or hydrogenated nitrile butadiene rubber (HNBR) are used as cable sheaths, leveraging their intrinsic chemical inertness to resist electrolyte corrosion. However, fluororubber is expensive and difficult to process, and hydrogenated nitrile butadiene rubber still exhibits some degree of swelling under prolonged immersion in high-temperature electrolytes. Another approach involves adding nanofillers (such as montmorillonite and nano-silica) to construct a physical barrier network, delaying solvent molecule penetration. However, the interfacial bonding between these fillers and the rubber matrix is ​​weak, and interfacial debonding easily occurs under long-term electrolyte immersion, leading to a decrease in barrier effect. Furthermore, while methods such as radiation crosslinking or peroxide crosslinking to increase crosslinking density can partially suppress swelling, they often sacrifice material flexibility, making it difficult to meet the cable bending performance requirements of the confined spaces within energy storage systems.

[0004] Therefore, developing a cable sheath material that combines excellent resistance to electrolyte swelling, good mechanical properties, and process feasibility has become a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide an electrolyte-resistant elastomer cable and its preparation method, which has excellent resistance to carbonate electrolyte swelling and good mechanical properties.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides an electrolyte-resistant swelling elastomer cable, comprising a conductor and a sheath layer, wherein the sheath layer is made of a composite material, and the composite material comprises, by weight: 100 parts of acrylic rubber matrix; 5-30 parts of nanofiller; 0.5-8 parts of ionic liquid containing crosslinkable functional groups; 1-5 parts of vulcanizing agent; Vulcanizing aid 0.5-3 parts; Anti-aging agent 0.5-2 parts; The ionic liquid is bonded to the surface of the nanofiller.

[0007] As used herein, "ionic liquid" refers to an organic salt compound composed entirely of cations and anions that is liquid at room temperature. Due to its extremely low volatility, high thermal stability, and structural designability, it possesses unique advantages in the field of polymer modification. The ionic liquid used in this invention contains crosslinkable functional groups. Its cations (such as imidazolium) can bind to the surface of the nanofiller, while its anions or crosslinkable functional groups such as vinyl and methacrylate groups introduced on its side chains can undergo covalent crosslinking reactions with the acrylate rubber matrix during vulcanization, thereby constructing a chemically bonded interface between the filler and the rubber.

[0008] In this paper, nanofillers refer to inorganic fillers in the range of 1-100 nanometers, including various morphologies such as sheet-like (e.g., montmorillonite), tubular (e.g., halloysite nanotubes), and spherical (e.g., nano-silica). Different morphologies of nanofillers can form complementary physical barrier networks in a rubber matrix: sheet-like fillers extend the diffusion path of small electrolyte molecules, tubular fillers form bridging structures to enhance interfacial bonding, and spherical fillers fill the gaps between molecular chains to improve material density.

[0009] Preferably, the ionic liquid is an imidazolium-based ionic liquid. Imidazolium-based ionic liquids have stable cationic structures and strong polarity, making them easy to form strong interactions with the surface of nanofillers. Furthermore, their molecular structures are easily modified to introduce various crosslinkable functional groups, making them a preferred type of ionic liquid for realizing the technical solution of this invention.

[0010] Preferably, the crosslinkable functional group is selected from at least one of vinyl and methacrylate groups. Vinyl and methacrylate groups are the most commonly used and most reactive crosslinkable functional groups in peroxide vulcanization systems, and can efficiently undergo covalent crosslinking reactions with acrylate rubber matrices at vulcanization temperatures to form stable chemical bond networks.

[0011] Preferably, the nanofiller is selected from at least one of sheet-like nanofillers, tubular nanofillers, and spherical nanofillers.

[0012] Preferably, the acrylate rubber matrix is ​​selected from ethylene-acrylate rubber. Ethylene-acrylate rubber has excellent heat resistance, oil resistance, and mechanical properties, and the active sites on its molecular chain can undergo covalent reactions with the crosslinkable functional groups of ionic liquids.

[0013] Preferably, the vulcanizing agent is an organic peroxide. Organic peroxides are the most commonly used vulcanizing agents for acrylate rubbers. Under heating conditions, they decompose to generate free radicals, which initiate a crosslinking reaction between the crosslinkable functional groups of the ionic liquid and the rubber matrix.

[0014] Preferably, the vulcanizing aid is at least one selected from triallyl isocyanurate and trimethylolpropane trimethacrylate. The vulcanizing aid acts as a crosslinking aid in the peroxide vulcanization system, improving crosslinking efficiency and density, and further optimizing the mechanical properties and resistance to media of the material.

[0015] The core of this invention lies in the following: First, ionic liquid is pre-anchored on the surface of the filler to form a modified nanofiller. Subsequently, during vulcanization, the crosslinkable functional groups on the ionic liquid undergo a covalent crosslinking reaction with the acrylate rubber matrix, thereby establishing a strong chemical bond interface between the filler and the rubber. This changes the traditional state where fillers are merely physically dispersed in the matrix, making the filler an organic component of the rubber crosslinking network. When the cable sheath is exposed to carbonate electrolytes, on the one hand, the acrylate rubber matrix itself has a certain polarity matching, exhibiting a certain degree of tolerance to the electrolyte; on the other hand, the physical barrier network formed by the nanofiller slows down the diffusion path of electrolyte molecules; more importantly, the chemical bonding structure of the filler-rubber interface makes it difficult for electrolyte molecules to penetrate into the interior of the material along the interface.

[0016] Secondly, the present invention provides a method for preparing an electrolyte-resistant swelling elastomer cable, comprising the following steps: (1) An ionic liquid containing crosslinkable functional groups is mixed with a nanofiller in a solvent, so that the ionic liquid binds to the surface of the nanofiller, and the modified nanofiller is obtained after removing the solvent. (2) The modified nanofiller obtained in step (1) is blended with an acrylate rubber matrix, a vulcanizing agent and other additives to obtain a sheath layer composite material; (3) The sheath layer composite material obtained in step (2) is coated onto the conductor by an extruder to form a sheath layer; (4) The coated cable is vulcanized to allow the crosslinkable functional groups of the ionic liquid to participate in the crosslinking reaction, thereby obtaining the electrolyte-resistant swelling elastomer cable.

[0017] The “pre-anchoring” process in step (1): With the assistance of solvent, the ionic liquid fully contacts the nanofiller and binds to the surface of the filler through ionic bonds or hydrogen bonds to form modified nanofiller.

[0018] The vulcanization process in step (4) causes the crosslinkable functional groups of the ionic liquid to undergo a covalent crosslinking reaction, ultimately forming an integrated chemical bonding network of "filler-ionic liquid-rubber".

[0019] Preferably, the mixing temperature in step (1) is 20-80°C, and the time is 0.5-6 hours. This temperature range is lower than the initiation temperature of the crosslinkable functional groups, ensuring that the ionic liquid binds to the filler surface only through physical action during the pre-anchoring stage, without premature crosslinking; at the same time, it ensures that the ionic liquid is fully dissolved in the solvent and uniformly adsorbed on the filler surface.

[0020] Preferably, the vulcanization temperature in step (4) is 150-190°C, and the time is 5-30 minutes. This temperature range allows the ionic liquid and the rubber matrix to undergo a sufficient covalent cross-linking reaction, forming a stable chemical bond network.

[0021] The beneficial effects of this invention are: This invention constructs an integrated chemical bonding network structure of "filler-ionic liquid-rubber" by pre-anchoring ionic liquid on the surface of nanofiller and covalent cross-linking with acrylate rubber matrix. At the same time, combined with the synergistic physical barrier effect of the multimorphology of nanofiller, a dual protection mechanism of chemical bonding and physical barrier is formed, which enables the cable sheath material to exhibit excellent resistance to electrolyte swelling and long-term stability. Detailed Implementation

[0022] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0023] An electrolyte-resistant swellable elastomer cable and its preparation method, comprising the following steps: (1) Dissolve 2 parts of 1-vinyl-3-ethylimidazolium tetrafluoroborate [VEIm]BF4 in 100 parts of anhydrous ethanol, add 10 parts of montmorillonite, and stir at 50°C for 2 hours to allow the ionic liquid to fully bind to the surface of montmorillonite. After the reaction is complete, remove the ethanol under reduced pressure, and dry the resulting solid under vacuum at 60°C for 4 hours to obtain the modified nanofiller.

[0024] (2) 100 parts of ethylene-acrylate rubber were put into a mixer and plasticized at 90°C for 2 minutes; the modified nanofiller prepared in step (1) and 1 part of N-phenyl-N were added. ' - Isopropyl p-phenylenediamine (4010NA) is mixed at 90-100℃ for 10 minutes; after debinding, it is transferred to a two-roll mill, cooled to 60℃, and 3 parts of dicumyl peroxide (DCP) and 2 parts of triallyl isocyanurate (TAIC) are added. The mixture is then thinly mixed 5 times and sheeted to obtain the sheath layer composite material.

[0025] (3) The sheath layer composite material obtained in step (2) is continuously coated onto the copper conductor through an extruder to form a sheath layer. The temperature of each section of the extruder is controlled at 80-100℃. The coated cable enters a continuous vulcanization pipeline and is vulcanized at 170℃ for 15 minutes to covalently crosslink the vinyl group of the ionic liquid with the ethylene-acrylate rubber, thereby obtaining an electrolyte-resistant swelling elastomer cable.

[0026] Example 2 An electrolyte-resistant swellable elastomer cable and its preparation method, comprising the following steps: The method is basically the same as in Example 1, except that montmorillonite is replaced with halloysite nanotubes, the amount of ionic liquid is adjusted to 4 parts, and the amount of nanofiller is adjusted to 15 parts.

[0027] Example 3 An electrolyte-resistant swellable elastomer cable and its preparation method, comprising the following steps: The method is basically the same as in Example 1, except that montmorillonite is replaced with nano-silica, the amount of ionic liquid is adjusted to 6 parts, and the amount of nanofiller is adjusted to 20 parts.

[0028] Example 4 An electrolyte-resistant swellable elastomer cable and its preparation method, comprising the following steps: The method is basically the same as in Example 1, except that: a composite nanofiller is used, and 8 parts of montmorillonite and 7 parts of halloysite nanotubes are mixed together, and the amount of ionic liquid is adjusted to 5 parts by weight.

[0029] Example 5 An electrolyte-resistant swellable elastomer cable and its preparation method, comprising the following steps: The method is basically the same as in Example 1, except that: the ionic liquid is replaced with an ionic liquid containing methacrylate groups (1-methacryloyloxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt), and the amount used is 3 parts; the vulcanizing aid is replaced with 2 parts of trimethylolpropane trimethacrylate (TMPTMA).

[0030] Comparative Example 1 The method is basically the same as in Example 1, except that 10 parts of montmorillonite are directly blended with the rubber matrix without adding ionic liquid.

[0031] Comparative Example 2 The process is basically the same as in Example 1, except that the ionic liquid and montmorillonite are added by direct blending without the pre-anchoring treatment in step (1).

[0032] Comparative Example 3 The example is basically the same as in Example 1, except that the ionic liquid used is a common ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, [EMIm]BF4) that does not contain crosslinkable functional groups.

[0033] Comparative Example 4 This comparative example is basically the same as Example 1, except that: silane coupling agent KH550 is used instead of ionic liquid to modify montmorillonite.

[0034] Example 6: Ionic Liquid Dosage Range The basic formulation is the same as in Example 1, except that the amount of ionic liquid [VEIm]BF4 is adjusted to 0.3 parts, 0.5 parts, 2.0 parts, 5.0 parts, 8.0 parts, and 9.0 parts, respectively.

[0035] Example 7: Range of Nanofiller Dosage The basic formula is the same as in Example 1, except that the amount of montmorillonite is adjusted to 3 parts, 5 parts, 15 parts, 25 parts, 30 parts, and 35 parts respectively.

[0036] Performance testing: (1) Volume swelling rate test: The vulcanized sheath material is made into a 10mm×10mm×2mm sample, the initial mass W0 is weighed, and it is immersed in a carbonate electrolyte (ethylene carbonate: dimethyl carbonate: methyl ethyl carbonate volume ratio 1:1:1) at 85℃ for 240 hours. After taking it out, the surface electrolyte is quickly wiped dry, and the mass W1 after swelling is weighed. The volume swelling rate is calculated as follows: Volume swelling rate (%) = (W1-W0) / W0×100%.

[0037] (2) Tensile strength and elongation at break test: Referring to GB / T 528-2009 standard, the vulcanized sheath material was made into dumbbell-shaped specimens and tested on a universal testing machine at a tensile speed of 500 mm / min. The initial tensile strength and initial elongation at break were recorded. After immersing the specimens in an electrolyte at 85℃ for 240 hours, the specimens were removed and the tensile strength and elongation at break after immersion were tested in the same way. The retention rate was calculated as follows: Retention rate (%) = (performance after immersion / initial performance) × 100%.

[0038] (3) Gel content test: Cut the vulcanized sheath material into small pieces, weigh the mass W2, wrap it with filter paper and place it in a Soxhlet extractor. Reflux extract with acetone as solvent for 24 hours. After taking it out, vacuum dry it to constant weight, weigh the mass W3, and calculate the gel content: gel content (%) = (W3 / W2) × 100%.

[0039] Table 1 Performance test results of each embodiment and comparative example As can be seen from the test results in Table 1, the cable sheath materials prepared in Examples 1-5 of this invention, after being immersed in carbonate electrolyte at 85°C for 240 hours, all exhibited a volume swelling rate of less than 6%, a tensile strength retention rate of more than 90%, and a break elongation retention rate of more than 85%, demonstrating excellent resistance to electrolyte swelling and long-term stability.

[0040] Table 2 Validation Results of Ionic Liquid Dosage Range The results showed that satisfactory electrolyte resistance and mechanical property retention could be achieved when the amount of ionic liquid was in the range of 0.5-8 parts.

[0041] Table 3 Validation results of nanofiller dosage range The results showed that the amount of nanofiller in the range of 5-30 parts could achieve satisfactory electrolyte resistance and mechanical property retention, and the processability was good.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An electrolyte-resistant elastomeric cable, comprising a conductor and a sheath layer, characterized in that, The sheath layer is made of a composite material, which comprises, by weight: 100 parts of acrylic rubber matrix; 5-30 parts of nanofiller; 0.5-8 parts of ionic liquid containing crosslinkable functional groups; 1-5 parts of vulcanizing agent; Vulcanizing aid 0.5-3 parts; Anti-aging agent 0.5-2 parts; The ionic liquid is bonded to the surface of the nanofiller.

2. The electrolyte-resistant elastomeric cable according to claim 1, characterized in that, The ionic liquid is an imidazolium-based ionic liquid.

3. The electrolyte-resistant elastomeric cable according to claim 1, characterized in that, The crosslinkable functional group is selected from at least one of vinyl and methacrylate groups.

4. The electrolyte-resistant elastomeric cable according to claim 1, characterized in that, The nanofiller is selected from at least one of sheet-like nanofillers, tubular nanofillers, and spherical nanofillers.

5. The electrolyte-resistant elastomeric cable according to claim 1, characterized in that, The acrylate rubber matrix is ​​selected from ethylene-acrylate rubber.

6. The electrolyte-resistant elastomeric cable according to claim 1, characterized in that, The vulcanizing agent is an organic peroxide.

7. The electrolyte-resistant elastomeric cable according to claim 1, characterized in that, The vulcanization aid is at least one of triallyl isocyanurate and trimethylolpropane trimethacrylate.

8. A method for preparing the electrolyte-resistant swelling elastomer cable according to any one of claims 1-7, characterized in that, Includes the following steps: (1) An ionic liquid containing crosslinkable functional groups is mixed with a nanofiller in a solvent, so that the ionic liquid binds to the surface of the nanofiller, and the modified nanofiller is obtained after removing the solvent. (2) The modified nanofiller obtained in step (1) is blended with an acrylate rubber matrix, a vulcanizing agent and other additives to obtain a sheath layer composite material; (3) The sheath layer composite material obtained in step (2) is coated onto the conductor by an extruder to form a sheath layer; (4) The cable after being covered is vulcanized so that the crosslinkable functional groups of the ionic liquid participate in the crosslinking reaction to obtain the electrolyte-resistant swelling elastomer cable.

9. The preparation method according to claim 8, characterized in that, The mixing temperature in step (1) is 20-80℃ and the time is 0.5-6 hours.

10. The preparation method according to claim 8, characterized in that, The vulcanization temperature in step (4) is 150-190℃ and the time is 5-30 minutes.

Images