Carbonized polyimide-based multifunctional interlayer material, preparation method and application of carbonized polyimide-based multifunctional interlayer material in lithium-sulfur battery

Abstract

According to the invention, a flexible carbonized polyimide film (C-PI) is used as a skeleton, and mixed slurry of nickel coordinated tetraaminobenzoquinone (Ni-TABQ) and poly 3, 4-ethylenedioxythiophene-polystyrolsulfon acid (PEDOT: PSS) is coated on the skeleton; the invention relates to a multifunctional interlayer material integrating physical barrier, chemical adsorption, catalysis and flame retardance, a preparation method and application of the multifunctional interlayer material in a lithium-sulfur battery. The prepared multifunctional intermediate layer is used as a functional intermediate layer of the lithium-sulfur battery and is clamped between a positive electrode and a diaphragm. The preparation method has the beneficial effects that the middle layer can be used as an upper layer current collector, and the PEDOT: PSS and Ni-TABQ with double catalytic sites can also provide more nucleation sites and reaction or contact sites of polysulfide for sulfur and lithium sulfide Li2S, so that the utilization rate of active substances is greatly improved. In addition, the lithium-sulfur battery can be used as a flame-retardant layer to prevent spontaneous combustion caused by short circuit, electric leakage and the like, so that the overall safety performance of the lithium-sulfur battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and more specifically to a multifunctional intermediate layer material prepared by coating a PEDOT:PSS / Ni-TABQ mixed slurry on a carbonized polyimide skeleton, a preparation method and application thereof in lithium sulfur batteries. Background Art

[0002] The polysulfides in lithium-sulfur batteries are easily soluble in the electrolyte, which not only greatly reduces the utilization rate of active materials, but also leads to the shuttle effect. At the same time, the polysulfides that shuttle to the negative electrode are also prone to corrode the lithium metal negative electrode. Therefore, the researchers introduced the concept of "intermediate layer", that is, inserting a functional intermediate layer between the positive electrode and the separator to hinder the shuttling of polysulfides. On the one hand, the intermediate layer acts as a "barrier" to physically block the shuttle effect; on the other hand, the conductive intermediate layer as the "second electrode" can not only act as an upper current collector, but also provide more nucleation sites for the charging product S and the discharge product Li2S, as well as reaction or contact sites with lithium polysulfide, thereby significantly improving the utilization rate of active materials. The introduction of the concept of intermediate layer has shifted the research and development direction of lithium-sulfur batteries from "closed" modification of positive electrode materials to "open" modification of positive electrode materials. An ideal functional intermediate layer usually has the following functions: ① Improve the positive electrode interface resistance. 1. By introducing a material with high conductivity as the upper current collector of the positive electrode of the battery, the recycling of polysulfides on the surface of the positive electrode is promoted, the utilization rate of active materials is increased, and the cycle stability of the battery is improved; 2. Inhibit the diffusion of lithium polysulfide. Through the structural design of the intermediate layer, chemical bonding, electrostatic repulsion and other physical or chemical adsorption effects, the diffusion of polysulfides is effectively inhibited, and the coulombic efficiency of the overall lithium-sulfur battery is improved; 3. Improve the kinetics of redox reactions. In order to promote the solid-liquid-solid phase conversion and improve the rate performance of the battery, materials with catalytic functions for the redox reaction of the battery are introduced. Therefore, various carbon-based materials with excellent conductive properties, polar materials with increased chemical adsorption sites, and catalytic materials such as single-atom metals are often used in the design of the intermediate layer. Summary of the invention

[0003] The present invention aims to solve the technical problems raised by the above-mentioned background technology and provide a new composite functional intermediate layer to solve the problems of low utilization rate of active materials and poor long-cycle stability in lithium-sulfur batteries.

[0004] To achieve the above object, the present invention provides the following technical solution: using lightweight and flexible C-PI as the skeleton, coating with doped Ni-TABQ and PEDOT:PSS composite coating, synergistically constructing a (PEDOT:PSS / Ni-TABQ)@C-PI multifunctional intermediate layer integrating physical barrier, chemical adsorption, catalysis and flame retardancy;

[0005] The raw materials of the intermediate layer include C-PI, Ni-TABQ, and PEDOT:PSS;

[0006] A further preferred solution: the C-PI is a polyimide membrane which has been treated by a carbonization process and has a thickness of 60 μm and an opening rate of ≥80%.

[0007] A further preferred embodiment: the solid content of the PEDOT:PSS is 1.5%.

[0008] Further preferred embodiment: the loading amount of the mixed slurry PEDOT:PSS / Ni-TABQ on the C-PI is about 0.16 mg cm -2 .

[0011] Further preferred embodiment: the surface density of the (PEDOT:PSS / Ni-TABQ)@C-PI multifunctional intermediate layer is 2.16 mg cm -2

[0014] A multifunctional intermediate layer material with a flexible C-PI as a skeleton and coated with a mixed slurry of Ni-TABQ and PEDOT:PSS and a preparation method thereof, comprising the following steps: (S1) carbonizing a polyimide film to obtain C-PI, (S2) preparing Ni-TABQ, (S3) dissolving Ni-TABQ in PEDOT:PSS, (S4) coating the mixed slurry on a C-PI film after stirring evenly, and obtaining a (PEDOT:PSS / Ni-TABQ)@C-PI multifunctional intermediate layer after drying.

[0015] A further preferred embodiment: the carbonization process is to heat the PI film at 2°C min under the protection of 0.1 MPa nitrogen atmosphere. -1 The temperature was raised from room temperature to 500°C in a vacuum tube furnace at a heating rate and maintained for 1 hour, then raised to 600°C at the same heating rate and maintained for 1 hour. Finally, the temperature was raised to 800°C at the same rate, maintained for 20 minutes, and then cooled to room temperature to obtain C-PI.

[0016] The above-mentioned (PEDOT:PSS / Ni-TABQ)@C-PI multifunctional intermediate layer is applied in the field of lithium-sulfur batteries and is used to prepare an intermediate layer of lithium-sulfur batteries, which is sandwiched between the positive electrode and the separator.

[0017] The steps of assembling lithium-sulfur batteries are as follows: in an Ar atmosphere in a glove box, lithium metal sheets, polypropylene microporous diaphragms (Celgard2400), intermediate layers, sulfur-carbon composite cathodes, and stainless steel springs are stacked in sequence and encapsulated in a CR2032 stainless steel battery case from top to bottom. A DOL / DME (V:V=1:1) mixed solvent containing 1M LiTFSI and 0.1M LiNO3 is selected, and the electrolyte is added according to the mass ratio of electrolyte to sulfur E / S≈9.

[0018] Beneficial effects:

[0019] 1. The conjugated double bond structure of C-PI and PEDOT:PSS chain ends jointly constructs a cross-linked interpenetrating three-dimensional conductive network, which not only plays the role of the upper current collector but also improves the utilization rate of active materials;

[0020] 2. The filler Ni-TABQ has a dense microstructure, and its Ni-N4 and quinone dual catalytic sites can enhance the adsorption of polysulfides, thereby improving the kinetics of the redox reaction;

[0021] 3. PEDOT:PSS chemically adsorbs lithium polysulfide by forming a chelate coordination structure of O-Li and S-Li bonds;

[0022] 4. The non-porous design of the PEDOT:PSS coating and the conformational changes of its polymer chains connect the entire cross section of the C-PI skeleton, improving the mechanical strength of the middle layer and its barrier ability to polysulfides;

[0023] 5. The adsorption energy of Ni-TABQ on polysulfides is stronger than that of PEDOT:PSS on lithium polysulfide. During the reaction with lithium polysulfide, the adsorption sites will not occupy the catalytic sites of Ni-TABQ, balancing the catalytic function and adsorption function. The redox kinetics only requires a lower activation energy, which is beneficial to improving the rate performance of the battery.

[0024] 6. When the intermediate layer is assembled into a battery, the electrolyte can improve the wetting ability of the PEDOT:PSS gel film, effectively lubricate the boundary of the heterojunction structure, and reduce the interface impedance.

[0025] 7. Highly heat-resistant PI has excellent mechanical properties. After carbonization treatment, C-PI not only stimulates more active sites, but also improves its heat resistance. It can resist circuit heating and spontaneous combustion caused by leakage, short circuit and other reasons inside the lithium-sulfur battery, thereby enhancing the safety performance of the battery.

[0026] 8. In summary, when the (PEDOT:PSS / Ni-TABQ)@C-PI multifunctional interlayer is inserted between the positive electrode and the separator of the lithium-sulfur battery, it can inhibit the diffusion and shuttling of polysulfides in the redox reaction, promote the rapid capture and catalytic conversion of polysulfides, and significantly improve the electrochemical performance of the lithium-sulfur battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the present invention applied to lithium-sulfur batteries.

[0028] Figure 2 This is a schematic diagram of the process flow for preparing the (PEDOT:PSS / Ni-TABQ)@C-PI intermediate layer of the present invention.

[0029] Figure 3 This is a scanning electron microscope image of the (PEDOT:PSS / Ni-TABQ)@C-PI intermediate layer of the present invention.

[0030] Figure 4 This is a test diagram of the conductivity of the (PEDOT:PSS / Ni-TABQ)@C-PI intermediate layer of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the attached embodiment of the present invention Figure 1-Figure 4 , clearly and completely describe the technical solutions in the embodiments of the present invention.

[0032] See also Figure 1-4 In the embodiment of the present invention, a light and flexible C-PI is used as a skeleton, and a doped Ni-TABQ and PEDOT:PSS composite coating is coated to collaboratively construct a (PEDOT:PSS / Ni-TABQ)@C-PI multifunctional intermediate layer integrating physical barrier, chemical adsorption, catalysis and flame retardancy;

[0033] In the embodiment of the present invention, a PI film with a thickness of 60 μm and an opening rate of ≥80% is heated at 2°C min under a 0.1 MPa nitrogen atmosphere. -1 The temperature was raised from room temperature to 500°C in a vacuum tube furnace at a heating rate of 100 °C and maintained for 1 h. Then, the temperature was raised to 600°C at the same heating rate and maintained for 1 h. Finally, the temperature was raised to 800°C at the same rate, maintained for 20 min, and then cooled to room temperature. The obtained product was C-PI. A roller press with a preset thickness of 30 μm was used at a pressure of 10 MPa and a pressure of 1 ms. -1 The C-PI film was rolled at a speed of .

[0034] In an embodiment of the present invention, 582 mg of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and 6 mL of concentrated ammonia water are dissolved in 120 mL of dimethyl sulfoxide (DMSO). After Ni(NO3)2·6H2O is completely dissolved, 336 mg of tetraaminobenzoquinone (TABQ) is added to the mixed solution. After vigorously stirring and reacting at 40°C for 2 hours, the mixture is transferred to a centrifuge and centrifuged at 9000 rpm for 10 minutes. The mixture is repeatedly washed with deionized water and alcohol for several times, and the product is vacuum dried at 80°C for 12 hours to obtain Ni-TABQ.

[0035] In the embodiment of the present invention, 2 mg of Ni-TABQ was dissolved in 10 mL of PEDOT:PSS with a solid content of 1.5%, and after being stirred evenly, the mixed slurry was coated on the C-PI film and dried at 60 ° C in a vacuum state for 12 h. The dried intermediate layer was cut into discs with a diameter of 16 mm using a slicer to obtain a thickness of 30 μm and a surface density of 2.16 mg cm -2 The (PEDOT:PSS / Ni-TABQ)@C-PI intermediate layer has a loading capacity of about 0.16 mg cm -2 .

[0036] In the embodiment of the present invention, the preparation of the positive electrode sheet is as follows:

[0037] Sublimed sulfur (S) and carbon nanotubes (CNTs) were mixed in a mass ratio of 8:2 and added to a ball mill, and anhydrous ethanol was added until the sample was just covered, and then the mixture was ball milled at a ball milling rate of 350rpm for 5 hours to obtain a mixture of sublimated sulfur and CNTs. After the mixture was dried and ground in a constant temperature blast drying oven at 60°C, it was transferred to a hydrothermal reactor and heated at 155°C for 12 hours under inert gas protection. After the reaction was completed, it was cooled to room temperature and ground to obtain a S / CNTs positive electrode material with a core-shell structure.

[0038] In the embodiment of the present invention, the preparation of the positive electrode sheet is as follows:

[0039] In the glove box under Ar atmosphere, lithium metal sheet, polypropylene microporous diaphragm (Celgard 2400), intermediate layer, sulfur-carbon composite positive electrode, stainless steel spring are stacked in sequence and encapsulated in a CR2032 stainless steel battery shell from top to bottom. A DOL / DME (V:V=1:1) mixed solvent containing 1MLiTFSI and 0.1M LiNO3 is selected, and the electrolyte is added according to the mass ratio of electrolyte to sulfur E / S≈9.

Claims

1. A multifunctional intermediate layer for lithium-sulfur batteries, characterized in that: It uses a lightweight, flexible carbonized polyimide film (C-PI) as the skeleton, on which is coated a mixed filler of Ni-TABQ and PEDOT:PSS. This intermediate layer brings out the synergistic effect of the component materials and improves the overall electrical performance of the lithium-sulfur battery.

2. A multifunctional intermediate layer for a lithium-sulfur battery according to claim 1, characterized in that The carbonized polyimide is used as the skeleton, and the carbonized polyimide is a skeleton of a polyimide (PI) film with a thickness of 60 μm and an opening rate of ≥80% after being carbonized.

3. The multifunctional intermediate layer of a lithium-sulfur battery according to claim 1, characterized in that The (PEDOT:PSS / Ni-TABQ)@C-PI multifunctional interlayer has a thickness of 30 μm and an area density of 2.16 mg cm -2 The loading amount of the mixed slurry PEDOT:PSS / Ni-TABQ is about 0.16 mg cm -2 , lithium-sulfur batteries have the best electrical performance.

4. The multifunctional intermediate layer of a lithium-sulfur battery according to claim 1, characterized in that The conjugated double bond structures of the C-PI and PEDOT:PSS chain ends jointly construct a cross-linked interpenetrating three-dimensional conductive network.

5. The multifunctional intermediate layer of a lithium-sulfur battery according to claim 1, characterized in that The PEDOT:PSS / Ni-TABQ coating is non-porous.

6. A method for preparing a multifunctional intermediate layer of a lithium-sulfur battery according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Preparation of C-PI skeleton: The PI film was carbonized in a vacuum tube furnace under the protection of a 0.1 MPa nitrogen atmosphere. After carbonization, it was cooled to room temperature and rolled using a roller press with a preset thickness of 30 μm at a pressure of 10 MPa at a speed of 1 m s -1 The film was rolled at a speed of 100 to obtain a C-PI film. (2) Preparation of Ni-TABQ: Dissolve 582 mg of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and 6 mL of concentrated ammonia in 120 mL of dimethyl sulfoxide (DMSO). After Ni(NO3)2·6H2O is completely dissolved, add 336 mg of tetraaminobenzoquinone (TABQ) to the mixed solution. After vigorously stirring at 4°C for 2 h, transfer the mixture to a centrifuge and centrifuge at 9000 rpm for 10 min. Wash the mixture repeatedly with deionized water and alcohol, and dry the product in vacuum at 80°C for 12 h. The obtained Ni-TABQ is ready for use. (3) Preparation of (PEDOT:PSS / Ni-TABQ)@C-PI functional intermediate layer: Dissolve 2 mg of Ni-TABQ described in step (2) in 10 mL of PEDOT:PSS with a solid content of 1.5%, stir evenly, and then coat the mixed slurry on the C-PI film described in step (1). Dry it at 60°C in a vacuum state for 12 hours. The dried intermediate layer is cut into discs with a diameter of 16 mm using a slicer to obtain the (PEDOT:PSS / Ni-TABQ)@C-PI functional intermediate layer for use.

7. The method for preparing a multifunctional intermediate layer of a lithium-sulfur battery according to claim 6, characterized in that: The carbonization process is that the heating rate of the vacuum tube furnace from room temperature to 500°C is 2°C min -1 The temperature was then raised to 600°C at the same rate and held for 1 hour. Finally, the temperature was raised to 800°C at the same rate and held for 20 minutes.

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