Lithium-sulfur battery cell shell high polymer material and preparation method thereof

Abstract

The application discloses a lithium-sulfur battery cell shell high polymer material and a preparation method thereof. The high polymer material comprises polyketone resin, modified polyamide resin, polytetrafluoroethylene, modified potassium titanate whisker, flame retardant and antioxidant. The modified polyamide resin is prepared by graft copolymerization of polyamide resin and trifluoroethyl methacrylate. The modified potassium titanate whisker is prepared by surface modification of potassium titanate whisker by amino silane coupling agent. The modified potassium titanate whisker is prepared by surface modification of potassium titanate whisker by amino silane coupling agent. The lithium-sulfur battery cell shell high polymer material provided by the application has excellent mechanical properties and flame retardant properties, and has low water absorption, strong gas barrier property and strong chemical corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a polymer material for the casing of a lithium-sulfur battery cell and its preparation method. Background Technology

[0002] With the increasing global demand for green and renewable energy, secondary batteries, as essential energy storage devices in the energy conversion and storage process, have received widespread attention and research from researchers. Currently, commercially available lithium-ion batteries are limited by their theoretical specific capacity and cannot meet the quality requirements of practical applications.

[0003] Lithium-sulfur batteries are rechargeable batteries that use sulfur as the positive electrode. Their materials have high theoretical specific capacity density (1675 mAh / g) and theoretical specific energy density (2600 Wh / kg), far exceeding those of currently commercialized lithium-ion batteries and meeting practical application requirements. Furthermore, because elemental sulfur is abundant on Earth, inexpensive, and environmentally friendly, lithium-sulfur batteries are a low-cost, green rechargeable battery option.

[0004] Current lithium battery cell casing and battery module housing designs can be divided into PVC heat-sealing and metal casings. PVC heat-sealing for cell casings is generally suitable for situations where the number of cells in series or parallel is small and the overall weight is light. However, for lithium-ion battery packs with a heavier overall weight, fixing brackets need to be added between the cells, and a fiberglass sheet is added for external protection before PVC heat sealing. Metal casings often use aluminum as the casing material. An aluminum casing is a battery casing made of aluminum alloy. The reason for using aluminum casings for lithium batteries is its light weight and safety compared to steel casings. Aluminum casings come in two designs: square corners and rounded corners. The material of aluminum casings is generally an aluminum-manganese alloy, which contains important alloying components such as Mn, Cu, Mg, Si, and Fe. These five alloys play different roles in the aluminum casing of lithium-ion batteries, and the aluminum alloy material structure has excellent safety performance.

[0005] However, PVC heat-sealing and aluminum alloy battery cell casings cannot simultaneously meet the requirements of mechanical performance and lightweight design. Therefore, engineering plastics made of polymer materials can be used as battery cell casings, so that they have both excellent mechanical performance and can meet the requirements of the new energy industry for lightweight materials.

[0006] However, the mechanical properties of polymer materials in existing technologies still need to be improved. For safety reasons, their flame retardant properties need to be enhanced. Furthermore, the electrical performance of the battery cell is affected when the battery cell casing material has poor water absorption or gas barrier properties. At the same time, the casing will be in long-term contact with various corrosive chemical components, so it needs to have excellent chemical corrosion resistance.

[0007] Therefore, there is an urgent need for a polymer material for lithium-sulfur battery cell casings that has excellent mechanical and flame-retardant properties, low water absorption, strong gas barrier properties, and strong resistance to chemical corrosion. Summary of the Invention

[0008] Purpose of the invention: In view of the deficiencies of the prior art, the purpose of this invention is to provide a polymer material for lithium-sulfur battery cell casing with excellent mechanical properties and flame retardant properties, low water absorption, strong gas barrier properties and strong chemical corrosion resistance, as well as a method for its preparation.

[0009] Technical solution:

[0010] A polymer material for the casing of a lithium-sulfur battery cell, characterized in that it comprises polyketone resin, modified polyamide resin, polytetrafluoroethylene, modified potassium titanate whiskers, flame retardant and antioxidant.

[0011] The modified polyamide resin is prepared by graft copolymerization of polyamide resin and trifluoroethyl methacrylate;

[0012] The modified potassium titanate whiskers were prepared by surface modification of potassium titanate whiskers using an aminosilane coupling agent.

[0013] This invention combines polyamide resin, which possesses excellent mechanical properties, and polyketone resin, which possesses excellent barrier properties, enabling the application of polymer materials in battery cell casing materials. Through the composite of polyketone resin, modified polyamide resin, polytetrafluoroethylene, modified potassium titanate whiskers, flame retardants, and antioxidants, it exhibits excellent mechanical and flame-retardant properties, as well as low water absorption, strong gas barrier properties, and strong resistance to chemical corrosion.

[0014] This invention adds polytetrafluoroethylene (PTFE) as a modified filler, which further improves the chemical corrosion resistance of the material through the stable chemical properties of PTFE; and the barrier properties of the material can be improved by uniformly compounding PTFE.

[0015] Furthermore, the polyketone resin is a copolymer of carbon monoxide and an olefin, wherein the olefin is selected from ethylene or propylene; and the polyamide resin is selected from PA66, PA6, PA610, PA612, PA1010 or PA11.

[0016] Furthermore, the flame retardant is selected from one of melamine cyanurate, aluminum tripolyphosphate, or antimony trioxide.

[0017] Furthermore, the antioxidant is selected from one of phosphite antioxidant 168, hindered phenolic antioxidant 1010, hindered phenolic antioxidant 1098, or hindered phenolic antioxidant 1076.

[0018] Further, the weight content of each component, by weight parts, is as follows:

[0019]

[0020] Further, the preparation of the modified polyamide resin includes the following steps: in a reactor, an organic solvent and polyamide resin are added, heated to 50-60°C, stirred to dissolve the polyamide resin, an initiator is added and trifluoroethyl methacrylate is slowly added dropwise over a period of 30-50 minutes, after the addition is completed, the temperature is raised to 70-90°C, and the reaction is maintained at this temperature for 2-3 hours. Then, the solvent is removed and the resin is recrystallized to obtain the modified polyamide resin.

[0021] Furthermore, the mass ratio of the polyamide resin to trifluoroethyl methacrylate is 3-5:1; the initiator is benzoyl peroxide.

[0022] This invention prepares a modified polyamide resin by graft copolymerization of polyamide resin and trifluoroethyl methacrylate. On the one hand, by grafting trifluoroethyl methacrylate groups onto the side links, the mechanical properties of the polyamide resin are further improved without changing the aggregation state of the polyamide and maintaining its main mechanical properties. On the other hand, by adding fluorine-containing groups, the chemical corrosion resistance of the polyamide resin can be significantly improved.

[0023] Furthermore, the preparation of the modified potassium titanate whiskers includes the following steps:

[0024] (1) Add aminosilane coupling agent and organic solvent to the reactor, stir evenly and adjust pH to 1.5-2 for later use;

[0025] (2) In a reactor, potassium titanate whiskers, organic solvent and the product of step (1) are added and stirred for 4-6 hours. The mixture is then filtered, washed and dried to obtain the modified potassium titanate whiskers.

[0026] Furthermore, the potassium titanate whiskers are selected from either potassium tetratitanate whiskers or potassium hexatitanate whiskers.

[0027] Furthermore, the mass ratio of the aminosilane coupling agent to potassium titanate whiskers is 1:10-15; the aminosilane coupling agent is selected from KH792 or KH602.

[0028] The present invention adds modified potassium titanate whiskers, which have excellent dispersibility in resin materials and can significantly improve the mechanical properties, chemical corrosion resistance and heat resistance of the materials. Furthermore, the present invention modifies the surface of potassium titanate whiskers with an aminosilane coupling agent, which can further improve its dispersibility in the materials and improve the materials' barrier properties against moisture and gas.

[0029] The preparation method of the polymer material for the lithium-sulfur battery cell casing according to any one of the above is characterized by comprising the following steps: weighing polyketone resin, modified polyamide resin, polytetrafluoroethylene, modified potassium titanate whiskers, flame retardant and antioxidant in proportion and adding them to a high-speed mixer for dry mixing for 3-5 minutes, then extruding them through a twin-screw extruder at 220-240°C, cooling, granulating, drying and packaging to obtain the polymer material for the lithium-sulfur battery cell casing.

[0030] Beneficial effects:

[0031] (1) The polymer material for lithium-sulfur battery cell casing provided by the present invention is a composite of polyketide resin and polyamide resin. By combining polyamide resin with excellent mechanical properties and polyketide resin with excellent barrier properties, the polymer material can be applied to cell casing material.

[0032] (2) The modified polyamide resin in the lithium-sulfur battery cell shell polymer material provided by the present invention is obtained by graft copolymerization of polyamide resin and trifluoroethyl methacrylate. On the one hand, by grafting trifluoroethyl methacrylate groups on the side, the mechanical properties of the polyamide resin are further improved without changing the aggregation state of the polyamide and maintaining its main mechanical properties. On the other hand, by adding fluorine-containing groups, the chemical corrosion resistance of the polyamide resin can be significantly improved.

[0033] (3) The polymer material of the lithium-sulfur battery cell shell provided by the present invention adds polytetrafluoroethylene as a modified filler. Through the stable chemical properties of polytetrafluoroethylene, the chemical corrosion resistance of the material is further improved; and the barrier ability of the material can be improved by uniformly compositing polytetrafluoroethylene.

[0034] (4) The modified potassium titanate whiskers added to the polymer material of the lithium-sulfur battery cell shell provided by the present invention have excellent dispersibility in the resin material, which can significantly improve the mechanical properties, chemical corrosion resistance and heat resistance of the material. Furthermore, the present invention can further improve the dispersibility of potassium titanate whiskers in the material by surface modification with aminosilane coupling agent, and can also improve the material's barrier to moisture and gas.

[0035] (5) The polymer material for the lithium-sulfur battery cell shell provided by the present invention is composed of polyketone resin, modified polyamide resin, polytetrafluoroethylene, modified potassium titanate whiskers, flame retardant and antioxidant. It has excellent mechanical properties and flame retardant properties, and has low water absorption, strong gas barrier properties and strong chemical corrosion resistance. Detailed Implementation

[0036] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0037] The polyamide resin PA66 was purchased from Dongguan Xinhui Plastic Raw Materials Co., Ltd. (RF002XSX); potassium hexatitanate whiskers were purchased from Shanghai Whisker Composite Materials Manufacturing Co., Ltd.; KH792 was purchased from Shandong Huachen New Materials Co., Ltd.; polyketone resin was purchased from Shandong Li'ang New Materials Technology Co., Ltd. (la5415); polytetrafluoroethylene was purchased from Guangzhou Jingchen Plastics Co., Ltd. (PTFE 6C); the remaining reagents and equipment were conventional reagents and equipment in this technical field.

[0038] Preparation of modified polyamide resin-1

[0039] Modified polyamide resin-1 was prepared by the following steps:

[0040] In a flask equipped with a stirrer, reflux condenser, thermometer, and dropping funnel, 50 mL of n-propanol and 5 g of polyamide resin PA66 powder were added. The mixture was heated to 55 °C and stirred to dissolve the polyamide resin PA66 powder. 0.3 g of benzoyl peroxide was added, and 1.2 g of trifluoroethyl methacrylate was slowly added dropwise over 50 minutes. After the addition was completed, the temperature was raised to 80 °C and the reaction was maintained at this temperature for 3 hours. The solvent was then removed, and the mixture was recrystallized to obtain the modified polyamide resin-1.

[0041] Preparation of modified polyamide resin-2

[0042] The preparation method is basically the same as that of modified polyamide resin-1, except that trifluoroethyl methacrylate is replaced with an equal amount of ethyl acrylate.

[0043] Preparation of modified potassium titanate whiskers

[0044] Modified potassium titanate whiskers were prepared by the following steps:

[0045] (1) In the reactor, add 0.5g of KH792 and 30mL of anhydrous ethanol, stir well, and then add glacial acetic acid to adjust the pH to 2 for later use.

[0046] (2) In a reactor, add 6g of potassium hexatitanate whiskers, 100mL of anhydrous ethanol and the product of step (1), stir for 6 hours, filter, wash and dry to obtain the modified potassium titanate whiskers.

[0047] Example 1

[0048] The polymer material for lithium-sulfur battery cell casing is prepared by the following steps:

[0049] Weigh out polyketone resin, modified polyamide resin-1, polytetrafluoroethylene, modified potassium titanate whiskers, aluminum tripolyphosphate and phosphite antioxidant 168 according to the proportions, add them to a high-speed mixer and dry mix for 5 minutes. Then, extrude the mixture at 230°C using a twin-screw extruder, cool it, granulate it, dry it, and package it to obtain the polymer material for the lithium-sulfur battery cell shell.

[0050] The weight content of each component, by weight parts, is as follows:

[0051]

[0052] Example 2

[0053] Basically the same as in Example 1, except that, by weight, the components and their weight content are as follows:

[0054]

[0055] Example 3

[0056] Basically the same as in Example 1, except that, by weight, the components and their weight content are as follows:

[0057]

[0058] Comparative Example 1

[0059] The method is basically the same as in Example 1, except that the modified polyamide resin-1 is replaced with an equal amount of commercially available polyamide resin PA66, and the polytetrafluoroethylene and modified potassium titanate whiskers are replaced with an equal amount of polyketide resin.

[0060] Comparative Example 2

[0061] The process is basically the same as in Example 1, except that the modified polyamide resin-1 is replaced with an equal amount of commercially available polyamide resin PA66.

[0062] Comparative Example 3

[0063] The process is basically the same as in Example 1, except that modified polyamide resin-1 is replaced with an equal amount of modified polyamide resin-2.

[0064] Comparative Example 4

[0065] The basic formula is the same as in Example 1, except that the modified potassium titanate whiskers are replaced with an equal amount of potassium hexatitanate whiskers.

[0066] Comparative Example 5

[0067] The method is basically the same as in Example 1, except that polytetrafluoroethylene is replaced with an equal amount of polyketide resin.

[0068] Performance testing

[0069] Mechanical strength testing: The tensile strength and elongation at break of the products of Examples 1-3 and Comparative Examples 1-5 were tested according to GB / T 1040 standard for determination of tensile properties of plastics.

[0070] Flame retardant performance testing: According to GB-T2408-2008 Test for flammability of plastics - Horizontal and vertical methods, the flame retardant ability of the products of Examples 1-3 and Comparative Examples 1-5 was tested by the vertical method.

[0071] The test results are shown in the table below:

[0072] Tensile strength (MPa) Elongation at break (%) Flame retardant properties Example 1 60 45 V-0 Example 2 58 46 V-0 Example 3 60 45 V-0 Comparative Example 1 40 30 V-1 Comparative Example 2 46 34 V-1 Comparative Example 3 51 37 V-0 Comparative Example 4 53 39 V-0 Comparative Example 5 55 43 V-1

[0073] According to the comparison of the test results of Examples 1-3 and Comparative Example 1, the polymer material for lithium-sulfur battery cell casing provided by the present invention has excellent mechanical strength and flame retardant properties, and can be applied to cell casing materials.

[0074] According to the comparison of the test results of Examples 1-3 and Comparative Examples 2 and 3, it can be seen that the addition of modified polyamide resin to the polymer material of the lithium-sulfur battery cell shell provided by the present invention, and the grafting modification of polyamide resin by trifluoroethyl methacrylate, can further improve its mechanical strength.

[0075] According to the comparison of the test results of Examples 1-3 and Comparative Example 4, it can be seen that adding modified potassium titanate whiskers to the polymer material of the lithium-sulfur battery cell shell provided by the present invention can limit and improve the mechanical strength of the material.

[0076] According to the comparison of the test results of Examples 1-3 and Comparative Example 5, it can be seen that adding polytetrafluoroethylene to the polymer material of the lithium-sulfur battery cell shell provided by the present invention can improve the flame retardant performance and mechanical strength of the material.

[0077] Chemical corrosion resistance test: Neutral salt spray test: The products of Examples 1-3 and Comparative Examples 1-5 were immersed in a 5% salt solution at room temperature, and the changes in the coating were observed; Alkali resistance test: The products of Examples 1-3 and Comparative Examples 1-5 were immersed in a 5% sodium hydroxide solution at room temperature, and the changes in the coating were observed.

[0078] Water absorption rate test: The water absorption rate of the products of Examples 1-3 and Comparative Examples 1-5 was tested according to the test standard of ISO 62-2008 for the determination of water absorption of plastics.

[0079] Gas barrier performance test: The gas permeability coefficient was tested using a self-made automated air tightness tester according to the GB / T1038-2000 standard. The smaller the gas permeability coefficient, the better the gas barrier performance. Test conditions: 23℃, N2 atmosphere.

[0080] The test results are shown in the table below:

[0081]

[0082]

[0083] According to the comparison of the test results of Examples 1-3 and Comparative Example 1, the polymer material of the lithium-sulfur battery cell shell provided by the present invention has excellent chemical corrosion resistance, low water absorption, and strong gas barrier properties.

[0084] According to the comparison of the test results of Examples 1-3 and Comparative Examples 2 and 3, it can be seen that the addition of modified polyamide resin to the polymer material of the lithium-sulfur battery cell shell provided by the present invention, and the grafting modification of polyamide resin by trifluoroethyl methacrylate, can significantly improve the chemical corrosion resistance of the material.

[0085] According to the comparison of the test results of Examples 1-3 and Comparative Example 4, it can be seen that adding modified potassium titanate whiskers to the polymer material of the lithium-sulfur battery cell shell provided by the present invention can significantly improve the chemical corrosion resistance of the material. Furthermore, by modifying the surface of potassium titanate whiskers with an aminosilane coupling agent, its dispersibility in the material can be further improved, and the material's barrier properties against moisture and gas can be enhanced.

[0086] According to the comparison of the test results of Examples 1-3 and Comparative Example 5, it can be seen that adding polytetrafluoroethylene to the polymer material of the lithium-sulfur battery cell shell provided by the present invention can further improve the chemical corrosion resistance of the material, and the barrier ability of the material can be improved by uniformly compositing polytetrafluoroethylene.

[0087] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A polymer material for the casing of a lithium-sulfur battery cell, characterized in that, By weight, it includes: 30-50 parts of polyketone resin 30-40 parts of modified polyamide resin 5-10 parts of polytetrafluoroethylene 10-15 parts of modified potassium titanate whiskers 1-3 parts flame retardant Antioxidant 1-3 parts; The modified polyamide resin is prepared by graft copolymerization of polyamide resin and trifluoroethyl methacrylate. The process includes the following steps: In a reactor, an organic solvent and polyamide resin are added, heated to 50-60°C, and stirred to dissolve the polyamide resin. Then, benzoyl peroxide, an initiator, is added, and trifluoroethyl methacrylate is slowly added dropwise. The mass ratio of polyamide resin to trifluoroethyl methacrylate is 3-5:1, and the addition time is 30-50 minutes. After the addition is completed, the temperature is raised to 70-90°C, and the reaction is maintained at this temperature for 2-3 hours. Finally, the solvent is removed, and the modified polyamide resin is obtained by recrystallization. The modified potassium titanate whiskers are prepared by surface modification of potassium titanate whiskers with an aminosilane coupling agent, including the following steps: (1) In the reactor, add aminosilane coupling agent and organic solvent, stir evenly and adjust pH to 1.5-2 for later use; the aminosilane coupling agent is selected from KH792 or KH602; (2) In the reactor, potassium titanate whiskers, organic solvent and the product of step (1) are added and stirred for 4-6 hours. After stirring, the modified potassium titanate whiskers are obtained by filtration, washing and drying. The mass ratio of aminosilane coupling agent to potassium titanate whiskers is 1:10-15.

2. The polymer material for the lithium-sulfur battery cell casing according to claim 1, characterized in that, The polyketone resin is a copolymer of carbon monoxide and an olefin, wherein the olefin is selected from ethylene or propylene; the polyamide resin is selected from PA66, PA6, PA610, PA612, PA1010 or PA11.

3. The polymer material for the lithium-sulfur battery cell casing according to claim 1, characterized in that, The flame retardant is selected from one of melamine cyanurate, aluminum tripolyphosphate, or antimony trioxide.

4. The polymer material for the lithium-sulfur battery cell casing according to claim 1, characterized in that, The antioxidant is selected from one of phosphite antioxidant 168, hindered phenolic antioxidant 1010, hindered phenolic antioxidant 1098, or hindered phenolic antioxidant 1076.

5. The method for preparing the polymer material for the lithium-sulfur battery cell casing according to any one of claims 1-4, characterized in that, Includes the following steps: Weigh out polyketone resin, modified polyamide resin, polytetrafluoroethylene, modified potassium titanate whiskers, flame retardant and antioxidant in proportion and add them to a high-speed mixer to dry mix for 3-5 minutes. Then, extrude the mixture through a twin-screw extruder at 220-240℃, cool it, granulate it, dry it and package it to obtain the polymer material for the lithium-sulfur battery cell shell.

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