Conductive adhesive, method for preparing the same, positive electrode sheet, and secondary battery

Abstract

The application belongs to the technical field of secondary batteries, and particularly relates to a conductive adhesive, a preparation method thereof, a positive electrode sheet and a secondary battery. The preparation method of the conductive adhesive comprises the following steps: step S1, stirring and dissolving trimethylol aminomethane in a solvent, adding hydrochloric acid to adjust the pH to obtain a trimethylol aminomethane solution; and step S2, adding pyrrole to the trimethylol aminomethane solution, cooling to 0-8 DEG C, and stirring for 1-5 h to obtain polypyrrole, namely the conductive adhesive. The conductive adhesive prepared by the application still has good adhesion at high voltage, can provide sufficient bonding strength, ensures that the electrode sheet does not delaminate or peel off at high voltage and high rate, significantly improves the adhesion and cycle stability of the electrode sheet; and the conductive adhesive also has good conductivity, effectively reduces impedance, improves electrochemical kinetic performance, and enables the electrode sheet to have good first charge-discharge performance, capacity retention rate, rate performance and stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary batteries, and particularly relates to a conductive binder, a preparation method thereof, a positive electrode sheet and a secondary battery. BACKGROUND

[0002] Consumer-grade lithium-ion battery products, especially 5G mobile phones and the like, have increasingly high requirements for the endurance time and charging time of lithium-ion batteries and the size thereof, and it is urgently needed to further improve the volume energy density and charging capacity of the batteries. Increasing the charging voltage of lithium cobaltate batteries can increase the volume energy density of the batteries, and increasing the charging rate of lithium cobaltate batteries can shorten the charging time of the batteries.

[0003] However, in the case of high-voltage and high-rate operation, the insufficient conductive capacity of the positive electrode material can cause a sharp capacity attenuation of the lithium battery, which cannot meet the requirements of actual production. A very effective way to improve the performance of high-voltage and high-rate lithium batteries is to develop a new type of binder with conductive capacity. At present, polyvinylidene fluoride (PVDF) is the most widely used binder in the lithium-ion battery system, and has good electrochemical stability, strong mechanical properties and electrolyte absorption rate, but does not have conductive capacity. Moreover, the PVDF only plays a binding role between the active material through weak van der Waals forces, and the weak van der Waals forces cannot provide sufficient binding strength, resulting in the easy occurrence of delamination and peeling of the electrode sheet under high-voltage operation, and thus cannot meet the use requirements of high-voltage and high-rate electrode materials. SUMMARY

[0004] One of the purposes of the application is to provide a conductive binder with conductive performance and binding strength in view of the deficiencies of the prior art, so that the material has sufficient binding strength, ensures that the electrode sheet does not delaminate or peel under high-voltage and high-rate, significantly improves the adhesion performance and cycle stability performance of the electrode sheet, and also has good conductive performance, effectively reduces the impedance, improves the electrochemical kinetic performance, and makes the electrode sheet have good first charge-discharge performance, capacity retention rate, rate performance and stability.

[0005] In order to achieve the above purpose, the application adopts the following technical scheme:

[0006] A preparation method of a conductive binder comprises the following steps:

[0007] Step S1, 0.2-1.5 parts by weight of tris-hydroxymethyl aminomethane is added to 30-60 parts of a solvent for stirring and dissolving, and hydrochloric acid is added to adjust the pH to obtain a tris-hydroxymethyl aminomethane solution;

[0008] Step S2, 1-5 parts by weight of pyrrole is added to the tris-hydroxymethyl aminomethane solution, cooled to-5℃-10℃, and stirred for 1-5 hours to obtain polypyrrole, i.e. the conductive binder.

[0009] Preferably, the step S2 is followed by a modification treatment of the polypyrrole.

[0010] Preferably, the modification treatment specifically comprises adding a buffer to the polypyrrole of step S2, cooling and stirring, adding dopamine, cooling and stirring again, to obtain dopamine-modified polypyrrole.

[0011] Preferably, the polypyrrole, the buffer and the dopamine are in a weight ratio of 1-4:2-10:0.1-3.

[0012] Preferably, the modification treatment further comprises adding polyacrylic acid gel to the dopamine-modified polypyrrole, adding a catalyst, stirring, centrifuging, and depositing to obtain polyacrylic acid / dopamine-modified polypyrrole.

[0013] Preferably, the polyacrylic acid gel, the dopamine-modified polypyrrole and the catalyst are in a weight ratio of 0.2-5:1-5:1-10.

[0014] Preferably, the modification treatment specifically comprises adding a buffer to the polypyrrole of step S2, cooling and stirring, adding polyacrylic acid gel and a catalyst, stirring, centrifuging, and depositing to obtain polyacrylic acid-modified polypyrrole.

[0015] Preferably, the polypyrrole, the buffer, the polyacrylic acid gel and the catalyst are in a weight ratio of 1-4:2-10:0.2-3:2-10.

[0016] The second object of the present application is to provide a conductive adhesive with both conductive and adhesive properties to overcome the deficiencies of the prior art.

[0017] To achieve the above object, the present application adopts the following technical scheme:

[0018] A conductive adhesive prepared by the method for preparing a conductive adhesive.

[0019] The third object of the present application is to provide a positive electrode sheet with good electrochemical properties to overcome the deficiencies of the prior art.

[0020] To achieve the above object, the present application adopts the following technical scheme:

[0021] A positive electrode sheet comprising the conductive adhesive.

[0022] The fourth object of the present application is to provide a secondary battery with good safety and cycle performance to overcome the deficiencies of the prior art.

[0023] To achieve the above object, the present application adopts the following technical scheme:

[0024] A secondary battery comprising the aforementioned positive electrode plate.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: the conductive binder prepared by the present invention still has good adhesion under high voltage, can provide sufficient bonding strength, and ensure that the electrode does not delaminate or peel off under high voltage and high rate, significantly improving the electrode adhesion performance and cycle stability; at the same time, it also has good conductivity, effectively reducing impedance and improving electrochemical kinetic performance, so that the electrode has good first charge and discharge performance, capacity retention, rate performance and stability. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0027] A method for preparing a conductive adhesive includes the following steps:

[0028] Step S1: Add 0.2 to 1.5 parts by weight of tris(hydroxymethyl)aminomethane to 30 to 60 parts by weight of solvent and stir to dissolve. Add hydrochloric acid to adjust the pH to obtain a tris(hydroxymethyl)aminomethane solution.

[0029] Step S2: Add 1 to 5 parts by weight of pyrrole to a tris(hydroxymethyl)aminomethane solution, cool to -5°C to 10°C, and stir for 1 to 5 hours to obtain polypyrrole, i.e., a conductive binder.

[0030] The conductive binder prepared by this invention maintains good adhesion under high voltage, providing sufficient bond strength to prevent electrode delamination or peeling, significantly improving electrode adhesion and cycle stability. Simultaneously, it exhibits good conductivity, effectively reducing impedance and improving electrochemical kinetics, resulting in good capacity retention and stability of the electrode. The conductive binder prepared by this invention is suitable for all cathode materials, and preferably works better in lithium cobalt oxide systems.

[0031] Step S1 involves preparing a Tris solution. Step S2 mainly involves mixing the Tris solution with pyrrole and polymerizing the mixture to obtain polypyrrole. The chemical formula for the prepared polypyrrole is as follows.

[0032]

[0033] Where n is a positive integer.

[0034] Preferably, the step S2 is followed by a modification treatment of the polypyrrole. Traditional binders include sodium carboxymethyl cellulose or polyvinylidene fluoride, both of which have poor conductivity and are prone to peeling off during the cycle process, losing the binder, and failing more severely under high voltage. The present application uses polypyrrole with good conductivity and adhesion to replace traditional binders, making the pole piece better, improving the conductivity and adhesion of the pole piece, and enabling the pole piece to withstand high voltage of 4.8V, 10C rate of charge and discharge, and more charge and discharge cycles. The present application uses polyacrylic acid and / or dopamine to modify the polypyrrole. The modified material can more closely connect and uniformly wrap the pole piece material, thereby improving the electron transport capacity between active substances and the adhesion effect.

[0035] Preferably, the modification treatment specifically includes adding a buffer to the polypyrrole in step S2, cooling and stirring, adding dopamine, cooling and stirring again, and obtaining dopamine-modified polypyrrole. Dopamine has good adhesion and structural stability, and has a reaction site available for reaction. Using dopamine to modify polypyrrole increases the adhesion of polypyrrole while maintaining a certain structural stability and avoiding dispersion under high voltage. The buffer is ammonium persulfate solution, which is used to adjust the pH of the solution for subsequent reactions. The chemical formula of the reaction is as follows:

[0036]

[0037] wherein a, b, and n are positive integers greater than or equal to 2.

[0038] Preferably, the weight ratio of polypyrrole, buffer, and dopamine is 1-4:2-10:0.1-3. Preferably, the weight ratio of polypyrrole, buffer, and dopamine is 1-4:2-10:0.1-3, 1-4:3-10:1-3, 1-4:3-8:1-3, 1-4:2-10:1-3, 1-4:2-7:1-3. Specifically, the weight ratio of polypyrrole, buffer, and dopamine is 1:2:0.1, 2:3:1.5, 1:2:2, 2:3:3, 1:2:3.

[0039] Preferably, the modification process further comprises adding polyacrylic acid gel into the dopamine-modified polypyrrole, adding a catalyst, stirring, centrifuging, and depositing to obtain polyacrylic acid / dopamine-modified polypyrrole. The secondary modification of the dopamine-modified polypyrrole using polyacrylic acid can increase the hardness, solubility and adhesion of the material, and significantly improve the adhesion and long cycle performance of the electrode material. The catalyst is 1-ethyl-(3-dimethylaminopropyl) carbonyl diimide hydrochloride. The stirring time is 3-12 h. The preparation method of the polyacrylic acid gel is to mix polyacrylic acid powder and deionized water, stir the supernatant until the white powder is completely dissolved and uniform, and obtain the polyacrylic acid gel. Finally, the precipitate collected by centrifugation is dried in a thermostatic electric blast drying oven at 60°C for 24 h, and the dried solid is finely ground in an agate mortar to obtain polyacrylic acid (PAA) / dopamine (DA)-modified polypyrrole (PPy).

[0040] Preferably, the weight ratio of the polyacrylic acid gel, the dopamine-modified polypyrrole and the catalyst is 0.2-3:1-5:2-10. The weight ratio of the polyacrylic acid gel, the dopamine-modified polypyrrole and the catalyst is 0.2-3:2-5:3-10, 0.5-3:2-5:3-8, 0.8-3:2-5:3-7, 1-3:1-5:2-7, 1.2-3:1-5:2-10, 1.5-3:1-5:2-10. Specifically, the weight ratio of the polyacrylic acid gel, the dopamine-modified polypyrrole and the catalyst is 0.2:2.5:4, 0.8:2.8:4, 2.3:3:4, 2.5:3.2:4, 2.8:3.5:4, 3:3.7:4, 2.8:4:4, 3:5:4.

[0041] Preferably, the weight ratio of the polyacrylic acid gel and the dopamine-modified polypyrrole is 0.2-5:1-10. The weight ratio of the polyacrylic acid gel and the dopamine-modified polypyrrole is 0.2-5:1-10, 0.5-5:2-10, 0.8-5:3-10, 1.2-5:4-10, 1.5-5:5-10, 2-5:5-10, 1.5-4:2-10. Specifically, the weight ratio of the polyacrylic acid gel and the dopamine-modified polypyrrole is 0.2:1, 0.8:2.5, 1.2:3, 2.5:3.8, 2.5:4.3, 2:4.8, 3:5.2, 3:6.1, 4:7.2, 4:8, 4.5:9, 5:9.

[0042] Preferably, the modification process specifically comprises adding a buffer to the polypyrrole in step S2, cooling and stirring, adding polyacrylic acid gel and a catalyst, stirring, centrifuging, and depositing to obtain polyacrylic acid-modified polypyrrole. The buffer is ammonium persulfate solution, which is used to adjust the pH value of the solution to facilitate the subsequent reaction.

[0043] Preferably, the weight ratio of the polypyrrole, the buffering agent, the polyacrylic acid gel, and the catalyst is 1-4:2-10:0.2-3:2-10. The weight ratio of the polypyrrole, the buffering agent, the polyacrylic acid gel, and the catalyst is 1-4:2-10:0.2-3:2-10, 2-4:3-10:1-3:3-10, 1-4:3-10:2.1-3:4-8, 1-4:2-10:0.2-3:2-10, 1-4:2-8:0.2-3:2-9, 1-4:2-10:0.2-3:2-10.

[0044] A conductive binder prepared by the above-mentioned method for preparing a conductive binder. The conductive binder of the present application has both conductive performance and adhesive performance.

[0045] A positive electrode sheet including the above-mentioned conductive binder.

[0046] The positive electrode sheet of the present application has good conductivity and high-rate charge-discharge performance, and also has good adhesion and stability, thereby improving the electrochemical and cycle characteristics of a lithium ion battery, effectively reducing material impedance, improving electrochemical kinetics, increasing system strength, and making capacity retention and stability higher.

[0047] A secondary battery including the above-mentioned positive electrode sheet.

[0048] A secondary battery having good safety performance and cycle performance.

[0049] The secondary battery can be a lithium ion battery, a sodium ion battery, a magnesium ion battery, a calcium ion battery, a potassium ion battery, etc. Preferably, the following secondary battery takes the lithium ion battery as an example, the lithium ion battery including a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and a shell, the separator separating the positive electrode sheet and the negative electrode sheet, and the shell being used to accommodate the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte. The positive electrode sheet is the above-mentioned positive electrode sheet.

[0050] Positive electrode

[0051] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material. The positive electrode active material can be, but is not limited to, Li a Ni x Co y M z O 2-b N bone or more of the compounds represented by the formulae: LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi0.5Mn1.5O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, TiS2, etc. The positive electrode active material can also be subjected to a modification treatment, and the method for modifying the positive electrode active material should be known to those skilled in the art, for example, the positive electrode active material can be modified by coating, doping, etc., and the material used for the modification treatment can be one or more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc. The positive current collector is generally a structure or part for collecting current, and the positive current collector can be any of the materials suitable for use as a positive current collector of a lithium ion battery in the art, for example, the positive current collector can be one or more of metal foils, etc., and more specifically, one or more of aluminum foils, etc. 0.5 Mn 1.5 one or more of the compounds represented by the formulae: LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi0.5Mn1.5O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, TiS2, etc. The positive electrode active material can also be subjected to a modification treatment, and the method for modifying the positive electrode active material should be known to those skilled in the art, for example, the positive electrode active material can be modified by coating, doping, etc., and the material used for the modification treatment can be one or more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc. The positive current collector is generally a structure or part for collecting current, and the positive current collector can be any of the materials suitable for use as a positive current collector of a lithium ion battery in the art, for example, the positive current collector can be one or more of metal foils, etc., and more specifically, one or more of aluminum foils, etc.

[0052] Negative electrode

[0053] The negative electrode sheet includes a negative current collector and a negative electrode active material layer disposed on the surface of the negative current collector, and the negative electrode active material layer includes a negative electrode active material, which can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based material, tin-based material, lithium titanate, or other metal capable of forming an alloy with lithium, etc. The graphite can be one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon alloy; and the tin-based material can be one or more of elemental tin, tin oxide compound, tin alloy. The negative current collector is generally a structure or part for collecting current, and the negative current collector can be any of the materials suitable for use as a negative current collector of a lithium ion battery in the art, for example, the negative current collector can be one or more of metal foils, etc., and more specifically, one or more of copper foils, etc.

[0054] Electrolyte

[0055] The lithium ion battery further comprises an electrolyte, the electrolyte comprising an organic solvent, an electrolyte lithium salt and an additive. The electrolyte lithium salt can be LiPF6 and / or LiBOB used in high-temperature electrolyte, or at least one of LiBF4, LiBOB and LiPF6 used in low-temperature electrolyte, or at least one of LiBF4, LiBOB, LiPF6 and LiTFSI used in overcharge-preventing electrolyte, or at least one of LiClO4, LiAsF6, LiCF3SO3 and LiN(CF3SO2)2. The organic solvent can be a cyclic carbonate, including PC and EC, or a chain carbonate, including DFC, DMC or EMC, or a carboxylic acid ester, including MF, MA, EA and MP. The additive includes, but is not limited to, at least one of a film-forming additive, a conductive additive, a flame-retardant additive, an overcharge-preventing additive, an additive for controlling the contents of H2O and HF in electrolyte, an additive for improving low-temperature performance, and a multifunctional additive.

[0056] Preferably, the material of the shell is one of stainless steel and aluminum plastic film. More preferably, the shell is aluminum plastic film.

[0057] Example 1

[0058] (1) Preparation of Tris solution

[0059] The reaction medium used in the experiment is Tris solution with a pH of 8.5 and a concentration of 10 mmol·L-1. The Tris solution is prepared as follows: 0.7268 g of Tris is weighed and dissolved in 50 mL of distilled water as a solvent. The pH of the solution is tested with a pH meter, and 6 mol·L-1 of HCl is added dropwise to adjust the pH to 8.5. Finally, 60 mL of Tris solution is obtained.

[0060] (2) Preparation of dopamine (DA)-modified polypyrrole (PPy)

[0061] 1.4536 g of pyrrole (Py) and the Tris solution prepared above are added to a flask, which is placed on a stirrer and stirred for 1 h with the temperature controlled at 0-8℃.

[0062] Chemical reaction equation of the above step:

[0063]

[0064] wherein n is a positive integer.

[0065] A certain concentration of 6 g of ammonium persulfate solution was slowly dropped into 2 g of the previous solution, and after stirring at 0-8℃ for 3h, 1.5 g of dopamine (DA) was added, and stirring was continued at 0-8℃ for 12h to obtain a dopamine (DA) modified polypyrrole (PPy) solution.

[0066] The chemical reaction equation of the above step is:

[0067]

[0068] Wherein, a, b, n are all positive integers greater than or equal to 2.

[0069] (3) Preparation of polyacrylic acid (PAA) / dopamine (DA) modified polypyrrole (PPy):

[0070] Polyacrylic acid powder was mixed with deionized water and stirred overnight until the white powder was completely dissolved and uniformly dispersed to obtain a polyacrylic acid gel. 4 g of polyacrylic acid gel was added to 8 g of dopamine (DA) modified polypyrrole (PPy) solution in step (2), and a catalyst EDCl was added and stirred overnight. After centrifugation and deionized water washing, the polyacrylic acid (PAA) / dopamine (DA) modified polypyrrole (PPy) particles produced in the reaction were collected. Finally, the precipitate collected by centrifugation was dried in an electric thermostatic air drying oven at 60℃ for 24h, and the dried solid was finely ground in an agate mortar to obtain polyacrylic acid (PAA) / dopamine (DA) modified polypyrrole (PPy).

[0071] Example 2

[0072] (1) Preparation of Tris solution

[0073] The reaction medium selected in this experiment was Tris solution with a pH of 8.5 and a concentration of 10 mmol·L-1. The method for preparing the Tris solution was as follows: 0.7268 g of Tris was weighed and dissolved in 50 mL of distilled water, the pH value of the solution was tested with a pH meter, and 6 mol·L-1 of HCl was added dropwise to adjust the pH value to 8.5, and 60 mL of Tris solution was obtained.

[0074] (2) Preparation of polypyrrole (PPy):

[0075] Pyrrole (Py) and Tris solution were added to a flask and stirred on a stirrer for 1h, controlling the temperature at 0-8℃. A certain concentration of ammonium persulfate solution was slowly dropped into the previous solution, and stirring was continued at 0-8℃ for 12h to obtain a polypyrrole (PPy) solution.

[0076] The chemical reaction equation of the above step is:

[0077]

[0078] wherein n is a positive integer.

[0079] (3) Preparation of dopamine (DA) modified polypyrrole (PPy):

[0080] A certain concentration of ammonium persulfate solution was slowly dropped into the previous solution, and after stirring at 0-8°C for 3h, a certain amount of dopamine (DA) was added, and the stirring was continued at 0-8°C for 12h to obtain a dopamine (DA) modified polypyrrole (PPy) solution. The dopamine (DA) modified polypyrrole (PPy) particle precipitate produced in the reaction was collected by centrifugation and deionized water washing. Finally, the centrifugation collected precipitate was dried in an electric thermostatic blast drying oven at 60°C for 24h, and the dried solid was finely ground in an agate mortar to obtain the dopamine (DA) modified polypyrrole (PPy).

[0081] Chemical reaction equation of the above step:

[0082]

[0083] wherein a, b, n are all positive integers greater than or equal to 2.

[0084] Example 3

[0085] (1) Preparation of Tris solution

[0086] The reaction medium selected in this experiment was Tris solution with a pH of 8.5 and a concentration of 10mmol·L-1. The method for preparing Tris solution was as follows: Tris 0.7268g was weighed and dissolved in 50mL of distilled water, the pH value of the solution was tested with a pH meter, and 6mol·L-1 HCl was added dropwise to adjust the pH value to 8.5, obtaining 60mL of Tris solution.

[0087] (2) Preparation of polypyrrole (PPy):

[0088] Pyrrole (Py) and Tris solution were added to a flask, stirred on a stirrer for 1h, and the temperature was controlled at 0-8°C. A certain concentration of ammonium persulfate solution was slowly dropped into the previous solution, and the stirring was continued at 0-8°C for 12h to obtain a polypyrrole (PPy) solution.

[0089] Chemical reaction equation:

[0090]

[0091] wherein n is a positive integer.

[0092] (3) Preparation of polyacrylic acid (PAA) / polypyrrole (PPy):

[0093] Polyacrylic acid powder was mixed with deionized water and stirred overnight until the white powder was completely dissolved and evenly distributed, obtaining a polyacrylic acid gel. A small amount of polyacrylic acid gel was added to the polypyrrole (PPy) solution in step (2), and a catalyst EDCI was added and stirred overnight. After centrifugation and deionized water washing, the polyacrylic acid (PAA) / polypyrrole (PPy) particles produced in the reaction were collected. Finally, the centrifugally collected precipitate was dried in an electric thermostatic air-drying oven at 60°C for 24h, and the dried solid was ground in an agate mortar to obtain polyacrylic acid (PAA) / polypyrrole (PPy).

[0094] Example 4

[0095] (1) Preparation of Tris solution

[0096] The reaction medium selected in this experiment was a Tris solution with a pH of 8.5 and a concentration of 10mmol·L-1. The method for preparing the Tris solution was as follows: Tris 0.7268g was weighed and dissolved in 50mL of distilled water, the pH value of the solution was tested with a pH meter, and 6mol·L-1 HCl was added dropwise to adjust the pH value to 8.5, obtaining 60mL of Tris solution.

[0097] (2) Preparation of polypyrrole (PPy):

[0098] Chemical reaction equation:

[0099]

[0100] wherein n is a positive integer.

[0101] Pyrrole (Py) and Tris solution were added to a flask and stirred on a stirrer for 1h, controlling the temperature at 0-8°C. A certain concentration of ammonium persulfate solution was slowly added dropwise into the previous solution, and stirring was continued at 0-8°C for 12h, obtaining a polypyrrole (PPy) solution. After centrifugation and deionized water washing, the polypyrrole (PPy) particles produced in the reaction were collected. Finally, the centrifugally collected precipitate was dried in an electric thermostatic air-drying oven at 60°C for 24h, and the dried solid was ground in an agate mortar to obtain polypyrrole (PPy).

[0102] Example 5

[0103] The difference from Example 1 is that the weight fraction of pyrrole is 1 part and the weight fraction of tris-hydroxymethyl aminomethane is 0.5 part.

[0104] The rest is the same as Example 1.

[0105] Example 6

[0106] The difference from Example 1 is that the weight fraction of pyrrole is 4 parts and the weight fraction of tris-hydroxymethyl aminomethane is 0.9 part.

[0107] The rest is the same as Example 1.

[0108] Example 7

[0109] The difference from Example 1 is that the weight fraction of pyrrole is 4 parts and the weight fraction of tris-hydroxymethyl aminomethane is 1.5 part.

[0110] The rest is the same as Example 1.

[0111] Example 8

[0112] The difference from Example 1 is that the weight fraction ratio of the polypyrrole, the buffer, and the dopamine is 1-4:2-10:0.1-3.

[0113] The rest is the same as Example 1.

[0114] Example 9

[0115] The difference from Example 1 is that the weight fraction ratio of the polypyrrole, the buffer, and the dopamine is 1-4:2-10:0.1-3.

[0116] The rest is the same as Example 1.

[0117] Example 10

[0118] The difference from Example 1 is that the weight fraction ratio of the polypyrrole, the buffer, and the dopamine is 1-4:2-10:0.1-3.

[0119] The rest is the same as Example 1.

[0120] Example 11

[0121] The difference from Example 1 is that the weight fraction ratio of the polyacrylic acid gel and the dopamine-modified polypyrrole is 0.5:3.

[0122] The rest is the same as Example 1.

[0123] Example 12

[0124] The difference from Example 1 is that the weight fraction ratio of the polyacrylic acid gel and the dopamine-modified polypyrrole is 2:5.

[0125] The rest is the same as example 1.

[0126] Example 13

[0127] The difference from example 1 is that the weight ratio of the polyacrylic acid gel to the dopamine modified polypyrrole is 2:6.

[0128] The rest is the same as example 1.

[0129] Example 14

[0130] The difference from example 1 is that the weight ratio of the polyacrylic acid gel to the dopamine modified polypyrrole is 4:10.

[0131] The rest is the same as example 1.

[0132] Comparative example 1 uses a polyvinylidene fluoride binder.

[0133] The binder prepared in the above examples 1-14 and comparative example 1 is mixed with lithium cobalt oxide and SuperP to prepare a positive electrode sheet, and the cathode sheet is applied to a lithium ion battery. The positive electrode sheet prepared in the above examples 1-14 and comparative example 1 is assembled into a lithium ion button cell, and the electrical performance test is carried out at room temperature, the charging condition is 10.0C, the discharging condition is 1.0C, and the charging and discharging range is 3.0V-4.70V. The test electrical performance results are as follows:

[0134] Table 1

[0135]

[0136]

[0137] From the above Table 1, it can be concluded that the conductive binder prepared by the present application has better capacity retention rate, and the first charge-discharge efficiency is not deteriorated, and the cycle stability and charge-discharge performance are effectively improved. From the comparison of Examples 1-4, it can be concluded that the conductive binder prepared by the present application has better capacity retention rate, first charge-discharge performance and rate performance, and the capacity retention rate after 100 charge-discharge cycles is 87.2%, the first charge-discharge efficiency is 97.1%, the charge capacity is 207.6 mAh / g, and the discharge capacity is 201.6 mAh / g. The performance of the conductive binder prepared by Example 2 is slightly worse than that of Example 1, but it is greatly improved compared with Comparative Example 1. This is because the dopamine used in Example 2 has good adhesion and stable structure, and can provide many reaction sites, thereby improving the stability of the conductive binder and preventing it from being broken down at high voltage and high rate. The performance of the conductive binder prepared by Example 3 is better than that of the traditional polyvinylidene fluoride binder. From the comparison of Example 2 and Example 3, it can be concluded that the modification of polypyrrole by dopamine and the modification of polypyrrole by polyacrylic acid can effectively improve the performance of polypyrrole, thereby effectively improving the performance of the conductive binder, and the improvement effect of dopamine on polypyrrole is better. From Example 4, it can be concluded that the polypyrrole prepared by the present application still has better electrochemical performance than the traditional polyvinylidene fluoride binder, and the first charge-discharge efficiency, capacity retention rate and rate performance are greatly improved.

[0138] From the comparison of Examples 1, 5-7, it can be concluded that when the weight fraction of polypyrrole is set to 2 parts and the weight fraction of tris is set to 1 part, the conductive binder prepared has better electrochemical performance, and the first charge-discharge efficiency, capacity retention rate and rate performance are greatly improved.

[0139] From the comparison of Examples 1, 8-10, it can be concluded that when the weight fraction ratio of polypyrrole, buffer and dopamine is set to 2:6:1.5, the conductive binder prepared has better electrochemical performance, and the first charge-discharge efficiency, capacity retention rate and rate performance are greatly improved.

[0140] It is concluded from the comparison of Examples 1, 11-14 that when the weight ratio of the polyacrylic acid gel to the dopamine-modified polypyrrole is 4:8, the prepared conductive adhesive has better electrochemical performance, and the first charge-discharge efficiency, capacity retention rate and rate performance are greatly improved.

[0141] Those skilled in the art can make modifications and variations to the above embodiments according to the disclosure and teachings of the specification. Therefore, the present application is not limited to the specific embodiments described above, and any obvious improvements, replacements or variations made by those skilled in the art on the basis of the present application shall fall within the protection scope of the present application. In addition, although some specific terms are used in the specification, these terms are only for convenience of description and do not constitute any limitation on the present application.

Claims

1. A method for producing an electrically conductive adhesive, characterized by, The conductive binder is a positive electrode conductive binder, comprising the following steps: Step S1, 0.2-1.5 parts by weight of tris-hydroxymethyl aminomethane is added into 30-60 parts of solvent to be stirred and dissolved, hydrochloric acid is added to adjust the pH to obtain a tris-hydroxymethyl aminomethane solution; Step S2, 1-5 parts by weight of pyrrole is added into the tris-hydroxymethyl aminomethane solution, cooled to-5-10℃, stirred for 1-5h, ammonium persulfate solution is slowly dropped into the previous solution, and the stirring is continued at 0-8℃ for 12h to obtain polypyrrole, i.e. the conductive binder; The chemical formula of the polypyrrole is as follows: Wherein, n is a positive integer; The step S2 further comprises a modification treatment of the polypyrrole; The modification treatment specifically comprises: adding a buffer into the polypyrrole of step S2, cooling and stirring, adding dopamine, secondary cooling and stirring to obtain dopamine-modified polypyrrole; or, The modification treatment specifically comprises: adding a buffer into the polypyrrole of step S2, cooling and stirring, adding polyacrylic acid gel and a catalyst, stirring, centrifuging, and depositing to obtain polyacrylic acid-modified polypyrrole.

2. The method of claim 1, wherein the conductive adhesive is prepared by mixing the conductive filler and the resin in a ratio of 1 : 1 to 1 :

10. The weight ratio of the polypyrrole, the buffer, and the dopamine is 1-4:2-10:0.1-3.

3. The method of claim 1, wherein the conductive adhesive is prepared by mixing the conductive filler and the resin in a ratio of 1 : 1 to 1 :

10. The modification treatment further comprises adding polyacrylic acid gel into the dopamine-modified polypyrrole, adding a catalyst, stirring, centrifuging, and depositing to obtain polyacrylic acid / dopamine-modified polypyrrole.

4. The method of claim 3, wherein the conductive adhesive is prepared by mixing the conductive filler and the resin in a ratio of 1 : 1 to 1 :

10. The weight ratio of the polyacrylic acid gel, the dopamine-modified polypyrrole, and the catalyst is 0.2-5:1-5:1-10.

5. The method of claim 1, wherein the conductive adhesive is prepared by mixing the conductive filler and the resin in a ratio of 1 : 1 to 1 :

10. The weight ratio of the polypyrrole, the buffer, the polyacrylic acid gel, and the catalyst is 1-4:2-10:0.2-3:2-10.

6. An electrically conductive adhesive characterized by, The conductive binder is prepared by the preparation method of any one of claims 1-5.

7. A positive electrode sheet characterized by comprising: The conductive binder of claim 6 is included.

8. A secondary battery characterized by comprising: The positive electrode sheet of claim 7 is included.

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