Double-conduction adhesive as well as preparation method and application thereof

Abstract

The invention discloses the technical field of adhesives, and particularly relates to a double-conduction adhesive which is prepared by the following steps: adding polyacrylic acid (PAA) and polyacrylamide (PAM) into deionized water, and stirring at room temperature to form a transparent solution, namely the double-conduction adhesive (c-PAA-PAM). The double-conduction binder prepared by the invention has excellent bonding performance and electrolyte wettability.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and in particular relates to a double-conductive adhesive and a preparation method and application thereof. Background Art

[0002] Internal resistance is an important factor affecting the power performance and discharge efficiency of lithium-ion capacitors. Its initial size is mainly determined by the structural design of the capacitor, the properties of the raw materials and the manufacturing process. It is one of the important indicators for evaluating the performance of lithium-ion capacitors. Internal resistance can cause polarization, which can cause the working state of lithium-ion capacitors to deviate from the steady state. In practice, as the polarization increases, the voltage drop of the capacitor increases, the rate performance is poor, and the discharge capacity decreases. Most of the current research focuses on the design of battery structure or the research on positive and negative active materials and electrolytes, and there is less research on inactive components in the battery, such as binders, conductive agents, etc. However, studies have shown that such inactive substances play a vital role in lithium-ion batteries.

[0003] Conductive agents mainly increase the conductivity of electrodes, and binders mainly bond several components of electrodes together. Therefore, in order to reduce the resistance of the electrode, the amount of conductive agents and binders needs to be increased, but the capacity will be reduced. The two balance and restrict each other. In order to solve the contradiction between increasing the proportion of active materials and improving the conductivity of electrodes, a feasible way is to develop binders with ultra-low impedance capabilities, which can solve the problems of electronic and ionic conduction while playing a bonding role.

[0004] Binders are polymer compounds that adhere electrode active materials to current collectors. They can maintain the structural stability of the electrode during charge and discharge and enhance the electronic contact between the electrode active materials and the conductive agent and current collector. Although traditional binders such as polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC) and sodium alginate (SA) can improve electrochemical stability, the electrochemical inertness of the binder will inevitably increase the ohmic resistance of the electrode, hindering the rapid transmission of electrons and ions between the electrode active materials and the conductive agent and current collector, thereby severely limiting the power density and energy density of energy storage devices.

[0005] In order to improve the overall conductivity of the electrode in traditional batteries, a certain amount of conductive agent needs to be added to the electrode. However, both the binder and the conductive agent are non-electrochemically active substances and do not contribute to any capacity. In addition, during high-rate charge and discharge, the binder oxidizes and decomposes and fails, often destroying the electronic conductive network of the electrode.

[0006] With this in mind, researchers use conductive polymers as binders. Conductive polymers can act as both conductors and binders, thereby reducing the use of inactive materials and increasing the proportion of active materials in the electrode. Conductive polymers are organic polymers with an extended π-conjugated structure throughout the polymer backbone that promotes electron conduction. In order to increase the conductivity of conjugated polymers, they need to be doped by oxidation (p-type doping) or reduction (n-type doping), and the doping process is crucial to improving conductivity. During the p-type doping process, free electrons are removed to produce positive polarons / bipolarons. During the n-type doping process, electrons are embedded in the polymer backbone to produce negative polarons / bipolarons, thereby exhibiting higher mobility.

[0007] In 2011, Yang et al. prepared polyfluorene-based n-type conductive polymer (PFFOMB) from 9,9-dioctylfluorene, fluorenone and methyl benzoate. The electron-withdrawing carbon group (C=O) in fluorenone can reduce the lowest unoccupied molecular orbital (LUMO) energy level and promote n-type doping. Methyl benzoate can improve the bonding strength of PFFOMB and give it the characteristics of a binder. Based on the good conductivity and mechanical properties of PFFOMB, Yang et al. used it as a silicon negative electrode binder, and the prepared electrode still had 2100 mAh g after 650 cycles. –1 Specific capacity.

[0008] Cui et al. used phytic acid and aniline as monomers and encapsulated silicon particles in a three-dimensional porous conductive polymer network by in-situ polymerization to obtain a silicon-polyaniline composite electrode (Si-PANi). The conductive polymer network provides a fast transmission channel for ions / electrons, the porous structure can accommodate the volume change of silicon, and the phosphate functional groups of phytic acid can react with SiO on the silicon surface. 2 Hydrogen bonds are formed. Therefore, the electrode structure is not easily destroyed during the cycle and has good conductivity and structural integrity. –1 After 5000 cycles, the capacity retention rate of Si-PANi electrode can reach 90%. Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) is a water-soluble conductive polymer with good electrochemical stability and mechanical stability. Its conductivity can be greatly improved by a simple secondary doping treatment. Coleman et al. used formic acid to perform secondary doping on PEDOT:PSS, which greatly improved its conductivity by nearly 100 times compared to undoped PEDOT:PSS. Using it as a conductive binder for silicon, the electrode has a high conductivity at 1.0A g –1 After 100 cycles, it can maintain 1950mAh g –1 The reversible specific capacity has excellent cycle stability.

[0009] Therefore, it is of positive significance to design and develop adhesives with high electrical conductivity and tensile strength. Summary of the invention

[0010] The present invention aims to provide a method for preparing a dual-conductive adhesive to provide an adhesive having excellent bonding properties and electrolyte wettability.

[0011] A method for preparing a dual-conductive adhesive in the present scheme comprises the following steps: adding polyacrylic acid (PAA) and polyacrylamide (PAM) into deionized water, and stirring at room temperature to form a transparent solution, namely, a dual-conductive adhesive (c-PAA-PAM).

[0012] Furthermore, the mass ratio of the polyacrylic acid to the polyacrylamide is 1.25:1 to 1:1.5.

[0013] Furthermore, the mass ratio of the sum of the mass of the polyacrylic acid and the polyacrylamide to the mass of deionized water is 0.3:9.7 to 0.5:9.5.

[0014] Furthermore, the stirring speed is 800-1200 r / min, and the stirring time is 6-12 h.

[0015] A dual-conductive adhesive is prepared by the preparation method of the dual-conductive adhesive.

[0016] The present application also claims protection for the use of the dual-conductive adhesive in electrode sheets and / or energy storage devices.

[0017] Furthermore, the electrode sheet is an electrode sheet for a lithium ion capacitor or a lithium ion battery.

[0018] Furthermore, the energy storage device is a lithium ion capacitor or a lithium ion battery.

[0019] Beneficial effects:

[0020] 1. c-PAA-PAM as a binder can form a stable complex with lithium ions (such as Figure 1 ), reducing the free energy of lithium ions at the interface, thereby significantly reducing the interface impedance.

[0021] 2. c-PAA-PAM has excellent bonding properties and electrolyte wettability, which can effectively promote the transmission of lithium ions and reduce electrode resistance.

[0022] 3. c-PAA-PAM dual-conductive adhesive has a large tensile force (16.02N). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of dual-conductive adhesive with PAA and PAM as raw materials;

[0024] Figure 2 This is a comparison chart of the tensile force tests of adhesives c-PAA-PAM, PAM and PAA;

[0025] Figure 3 Comparison of contact angle tests of adhesives c-PAA-PAM, PAM and PAA

[0026] Figure 4 It is a comparison chart of the conductivity test of each embodiment and comparative example. DETAILED DESCRIPTION

[0027] The following is further described in detail through specific implementation methods:

[0028] Example 1: 0.2g of PAA and 0.25g of PAM (mass ratio 1:1.25) were added to 9.55g of deionized water, and stirred at room temperature for 10 hours at a speed of 1000r / min to form a transparent solution to obtain a dual-conductive binder solution (c-PAA-PAM), and active materials were added and stirred to obtain electrode slurry. After the dual-conductive binder solution was uniform, it was coated on copper foil, and then placed in a vacuum drying oven at 150°C for heat treatment for 2 hours to obtain a c-PAA-PAM dual-conductive binder film, which can be used for subsequent tensile force and conductivity tests.

[0029] Figure 2 and Figure 3 The tensile force test and electrolyte wettability test results of PAA (the ratio between PAA and deionized water is 0.4:9.6), PAM (the ratio between PAA and deionized water is 0.4:9.6), and c-PAA-PAM (the ratio between the sum of the mass of PAA and PAM and deionized water is 0.4:9.6) are compared. The tensile force of the c-PAA-PAM dual-conductive adhesive reaches 16.02N, and the contact angle with the electrolyte is 30.5°, showing good electrolyte wettability.

[0030] Comparative Example 1: 0.3g of PAA and 0.25g of PAM (mass ratio 1.2:1) were added to 9.45g of deionized water, and stirred at room temperature for 10 hours at a speed of 1000r / min to form a transparent solution (c-PAA-PAM), and a dual-conductive binder solution (c-PAA-PAM) was obtained. The active material can be added and stirred to obtain an electrode slurry. After the dual-conductive binder solution is uniform, it is coated on a copper foil, and then placed in a vacuum drying oven at 150°C for heat treatment for 2 hours to obtain a c-PAA-PAM dual-conductive binder film, which can be used for subsequent tensile force and conductivity tests.

[0031] Example 2: 0.2g of PAA and 0.25g of PAM (mass ratio 1:1.25) were added to 9.55g of deionized water, and stirred at room temperature for 8 hours at a speed of 1000r / min to form a transparent solution (c-PAA-PAM), and a dual-conductive binder solution (c-PAA-PAM) was obtained. The active material can be added and stirred to obtain an electrode slurry. After the dual-conductive binder solution is uniform, it is coated on a copper foil, and then placed in a vacuum drying oven at 150°C for heat treatment for 2 hours to obtain a c-PAA-PAM dual-conductive binder film, which can be used for subsequent tensile force and conductivity tests.

[0032] Comparative Example 2: 0.2g of PAA and 0.25g of PAM (mass ratio 1:1.25) were added to 9.55g of deionized water, and stirred at room temperature for 12 hours at a speed of 1000r / min to form a transparent solution (c-PAA-PAM), and a dual-conductive binder solution (c-PAA-PAM) was obtained. The active material can be added and stirred to obtain an electrode slurry. After the dual-conductive binder solution is uniform, it is coated on a copper foil, and then placed in a vacuum drying oven at 150°C for heat treatment for 2 hours to obtain a c-PAA-PAM dual-conductive binder film, which can be used for subsequent tensile force and conductivity tests.

[0033] Example 3: 0.3g of PAA and 0.2g of PAM (mass ratio 1.5:1) were added to 9.5g of deionized water, and stirred at room temperature for 10 hours at a speed of 1000r / min to form a transparent solution (c-PAA-PAM), and a dual-conductive binder solution (c-PAA-PAM) was obtained. The active material can be added and stirred to obtain an electrode slurry. After the dual-conductive binder solution is uniform, it is coated on a copper foil, and then placed in a vacuum drying oven at 150°C for heat treatment for 2 hours to obtain a c-PAA-PAM dual-conductive binder film, which can be used for subsequent tensile force and conductivity tests.

[0034] Comparative Example 3: 0.3g of PAA and 0.25g of PAM (mass ratio 1.2:1) were added to 9.45g of deionized water, and stirred at room temperature for 10 hours at a speed of 1000r / min to form a transparent solution (c-PAA-PAM), and a dual-conductive binder solution (c-PAA-PAM) was obtained. The active material can be added and stirred to obtain an electrode slurry. After the dual-conductive binder solution is uniform, it is coated on a copper foil, and then placed in a vacuum drying oven at 150°C for heat treatment for 2 hours to obtain a c-PAA-PAM dual-conductive binder film, which can be used for subsequent tensile force and conductivity tests.

[0035] The present invention uses PAA (polyacrylic acid) binder as the main chain and composites polyacrylamide (PAM) through an in-situ polymerization route to prepare a dual-conductive composite adhesive, while maintaining its excellent bonding ability, improving its transmission dynamics and structural stability, thereby obtaining a lithium ion capacitor with ultra-high power density. Figure 1 This is a schematic diagram of the structure of the dual-conductive binder after cross-linking. Polyacrylic acid (PAA) has a large number of carboxyl functional groups, which can form strong hydrogen bonds between the active material and the current collector. It is an adhesive suitable for both positive and negative electrodes. Figure 4 This is the test result of the conductivity of the dual-conductive adhesive, which can reach up to 1.14mS / cm.

[0036] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a dual-conductive adhesive, characterized in that: The following steps are involved: Add polyacrylic acid and polyacrylamide into deionized water and stir at room temperature to form a transparent solution, namely, a dual-conductive adhesive.

2. The method for preparing a dual-conductive adhesive according to claim 1, characterized in that: The mass ratio of the polyacrylic acid to the polyacrylamide is 1.25:1 to 1:1.

5.

3. The method for preparing a dual-conductive adhesive according to claim 2, characterized in that: The mass ratio of the sum of the mass of the polyacrylic acid and the polyacrylamide to the mass of deionized water is 0.3:9.7 to 0.5:9.

5.

4. The method for preparing a dual-conductive adhesive according to claim 3, characterized in that: The stirring speed is 800-1200 r / min, and the stirring time is 6-12 h.

5. A dual-conductive adhesive, characterized in that: The dual-conductive adhesive is prepared by the preparation method of the dual-conductive adhesive according to any one of claims 1 to 4.

6. Use of the dual-conductive adhesive according to claim 5 in electrode sheets and / or energy storage devices.

7. The use of a dual-conductive adhesive in an electrode sheet and / or an energy storage device according to claim 6, characterized in that: The electrode sheet is an electrode sheet for a lithium ion capacitor or a lithium ion battery.

8. The use of a dual-conductive adhesive in an electrode sheet and / or an energy storage device according to claim 6, characterized in that: The energy storage device is a lithium ion capacitor or a lithium ion battery.

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