Binder system with electron and ion conduction function and application thereof

Abstract

The invention discloses a binder system with an electron and ion conduction function and application thereof. The binder system comprises 1) a cross-linking agent containing an ethyoxyl unit and 2) a polymer with electron conduction or electron and ion conduction functions, and the cross-linking agent and the polymer respectively have groups which are cross-linked under light and / or heat conditions; when in use, light and / or heat are utilized to initiate a cross-linking reaction, so that the polymer is cross-linked in situ by the cross-linking agent, and a three-dimensional binder network structure for ion and electron transmission is formed. According to the binder system disclosed by the invention, the polymer is subjected to in-situ crosslinking by utilizing the cross-linking agent to form a three-dimensional binder network structure, the polymer is used as a conjugated main chain for providing electron transmission, and the cross-linking agent is used as a flexible cross-linking chain segment beneficial to ion diffusion, so that the mechanical property of the binder is improved to the greatest extent while the high adhesive force of the binder is ensured; enough mechanical properties are provided for a battery pole piece to maintain the integrity of an electrode, so that the cycling stability of the high-specific-capacity negative electrode material is improved.

Description

Technical Field

[0001] The present application relates to the technical field of battery binder materials, and in particular to a binder system having electron and ion conducting functions and its application. Background Art

[0002] The rapid development of electric vehicles and consumer electronics has stimulated an urgent need for high energy density batteries. Using silicon-based anodes to break through the capacity limitations of traditional graphite anodes is a promising approach. Silicon-based anodes exhibit advantages such as high theoretical specific capacity, low redox potential, green environmental protection, and low cost. Nevertheless, silicon-based anodes experience significant volume expansion during the lithium insertion-delithiation process, resulting in unrestricted thickening of the solid electrolyte interface (SEI). This evolution ultimately leads to electrolyte depletion and destruction of the electron percolation network, resulting in irreversible capacity loss.

[0003] Traditional battery electrode sheets are composed of three main components: electrode active materials, conductive carbon black and binders. Among them, the binder is one of the important components of the battery electrode. Its function is to bond the electrode active material and conductive carbon black to the current collector to maintain the integrity of the electrode's electron transport network. Commercial binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), sodium polyacrylate (PAA-Na), lithium polyacrylate (PAA-Li), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR) and acrylonitrile copolymers (LA132, LA133). Although the binder accounts for a low proportion in the electrode, its own performance plays a key role in the electrochemical performance of the electrode, especially in terms of cycle stability and rate performance.

[0004] Existing commercial binders can meet the use requirements of graphite negative electrode materials. However, when high specific capacity negative electrode materials (such as silicon-based materials) replace traditional graphite negative electrodes, existing commercial binders cannot adapt to the severe volume changes of the negative electrode, and cannot solve the problems of particle pulverization and electrode collapse, which eventually causes the electrode material to fall off the current collector and lose electrochemical activity. Therefore, the key to preventing performance degradation is to inhibit the free expansion / contraction of the electrode while maintaining the integrity of the electron / ion transport network at the silicon-based negative electrode interface. The development of new binders with electronic and ion conductive functions (i.e., electronic / ion conductive binders) is considered to be one of the important strategies to solve the problem of cycle stability of high specific capacity negative electrode materials.

[0005] The so-called binder with electron and ion functions refers to a special type of binder with both electron and ion transport properties and adhesiveness. Its adhesiveness can bond the various components of the electrode to the current collector, its electron transport performance can replace conductive carbon black to build a molecular-level conductive network, and its ion transport performance can accelerate the diffusion of interface ions. With the help of the three-dimensional electron and ion network constructed by the electron / ion binder, the high-capacity negative electrode can maintain electrochemical activity by maintaining good contact with the binder after particle pulverization. Current research results show that when a conductive polymer and polyethylene oxide (PEO) are blended as a negative electrode binder, the conductive polymer has an electron transport function after electrochemical doping, and the rich ethoxy units in PEO can coordinate with ions to facilitate ion diffusion. Silicon-based electrodes using such binders will greatly improve their cycle stability and rate performance. However, the conductive polymer itself has a low molecular weight and limited mechanical properties. Simply physically mixing it with polyethylene oxide cannot provide sufficient mechanical properties to maintain electrode integrity, thus hindering its practical application in batteries.

[0006] How to improve the comprehensive performance of the electron / ion binder system so that it can maximize the mechanical properties of the binder while ensuring high adhesion of the binder and improve the cycle stability of high specific capacity negative electrode materials has become a major technical problem to be solved. Summary of the invention

[0007] The purpose of the present application is to provide a new adhesive system having electron and ion conducting functions and its application.

[0008] In order to achieve the above objectives, this application adopts the following technical solutions:

[0009] The first aspect of the present application discloses a binder system with electron-conducting and ion-conducting functions, comprising 1) a cross-linking agent containing ethoxy units and 2) a polymer with electron-conducting functions or electron-conducting and ion-conducting functions, wherein the cross-linking agent and the polymer respectively have groups that are cross-linked under light and / or heat conditions; when used, the cross-linking reaction is initiated by light and / or heat, so that the cross-linking agent cross-links the polymer in situ to form a three-dimensional binder network structure for ion and electron transmission.

[0010] It should be noted that compared with the existing binders of the same type, the binder system of the present application with electron and ion conductive functions uses a crosslinking agent to in-situ crosslink a polymer (such as a conductive polymer, or a polymer with electron and ion conductive functions) to form a three-dimensional binder network structure, which can maximize the mechanical properties of the binder while ensuring high adhesion of the binder, thereby providing sufficient mechanical properties for the battery electrode to maintain electrode integrity, thereby improving the cycle stability of the high specific capacity negative electrode material. The binder system of the present application, such as Figure 1As shown, the polymer acts as a conjugated main chain that provides electron transport, and the cross-linking agent acts as a flexible cross-linking segment that is beneficial to ion diffusion. The two react through heat and / or light to form a three-dimensional electron and ion transport network; when the polymer is an electron-conducting and ion-functional polymer, the ion-conducting function of the binder system can be further enhanced.

[0011] In one implementation of the present application, the crosslinking agent has a thiol group and the polymer has an olefin group; and / or both the crosslinking agent and the polymer have an olefin group. The thiol group of the crosslinking agent and the olefin group of the polymer initiate a crosslinking reaction by light; when both the crosslinking agent and the polymer have an olefin group, the crosslinking reaction is initiated by heating.

[0012] It should be noted that the key to the present application is that the cross-linking agent cross-links the polymer in situ to form a three-dimensional binder network structure for ion and electron transport; therefore, in principle, as long as the cross-linking agent and polymer can produce a cross-linking reaction under light and / or heat conditions, they can be applied to the binder system of the present application, not limited to the photo-click reaction of thiol and olefin groups or the thermal cross-linking reaction of olefin groups.

[0013] In one implementation of the present application, the polymer also has a group and / or side chain for ion transport, so that it has an ion-conducting function.

[0014] In one implementation of the present application, the group of the polymer used for ion transport is an ethoxy group, and the side chain used for ion transport is a side chain containing an ethoxy group.

[0015] It should be noted that the ethoxy group is only a specific ion transport group used in one implementation of the present application and has been proven to have good effects. Under the inventive concept of the present application, it is not excluded that other groups with ion transport functions can also be used.

[0016] In one implementation of the present application, the polymer further has a group and / or side chain that increases viscosity.

[0017] In one implementation of the present application, the group that increases the viscosity of the polymer is a carboxylic acid, and the side chain that increases the viscosity is a carboxylate side chain.

[0018] It should be noted that the polymer has a carboxylic acid or carboxylate side chain, which can increase the adhesion of the adhesive system; it can be understood that the carboxylic acid or carboxylate side chain is only one implementation of the present application to increase the viscosity of the polymer. Under the inventive concept of the present application, it is not excluded that other groups that increase the viscosity of the polymer can also be used.

[0019] In one implementation of the present application, the polymer is a water-soluble polyfluorene and / or a water-soluble polyfluorene derivative.

[0020] In one implementation of the present application, the water-soluble polyfluorene derivative is a water-soluble homopolymer or copolymer formed by a fluorene unit of the water-soluble polyfluorene and at least one unit of benzothiadiazole, carbazole, and phenylacetylene.

[0021] In one implementation of the present application, the water-soluble polyfluorene is polymerized by the units shown in Formula 1 and Formula 2.

[0022] In one implementation of the present application, the water-soluble polyfluorene derivative is a water-soluble homopolymer or copolymer formed by adding at least one unit of formulae 3 to 8, wherein the water-soluble polyfluorene derivative is a unit of formulae 1 and 2;

[0023]

[0024] In Formula 1, Formula 2 and Formula 3, n is an integer greater than 0; in Formula 2, R is H, Li, Na or K.

[0025] It should be noted that the binder system of the present application, the units shown in Formula 1 and Formula 2, are only water-soluble polyfluorenes specifically used in one implementation of the present application, and other water-soluble polyfluorenes may also be used. In the present application, Formula 1 is characterized in that the fluorene structural unit has an olefin side chain, which serves as an active reaction site for subsequent thermal or photocrosslinking reactions; Formula 2 is characterized in that the fluorene structural unit has a carboxylic acid or carboxylate side chain, which increases the adhesion of the binder system; therefore, the ratio of Formula 1 and Formula 2 can be adjusted according to demand. Generally speaking, the two can form a polymer in a 1:1 ratio.

[0026] It should also be noted that the binder system of the present application, the water-soluble polyfluorene derivative obtained by replacing the units shown in formulas 3 to 8, has the effect of introducing new functions and effects in polyfluorene through the units shown in formulas 3 to 8, improving the performance of polyfluorene, and then improving the overall performance of the binder system. For example, formula 3 is characterized in that it has an ethoxy side chain, which has the effect of giving the polymer an ion-conducting function and enhancing the ion-conducting function of the binder system. Formula 4 is characterized in that the benzene ring structure can form a conjugated conductive electron main chain with formulas 1 and 2, which has the effect of increasing the degree of freedom of the polymer segment and regulating the flexibility of the segment, which will affect the conductivity of the polymer. Formulas 5 to 7 are characterized in that they constitute a polymer main chain with formulas 1 and 2, which has the effect of regulating the electrochemical doping effect of the polymer and improving the conductivity of the polymer. The structure of formula 8 participates in the formation of a polymer, which has the effect of modifying a linear polymer into a dendritic polymer.

[0027] In one implementation of the present application, the molecular weight of the polymer is 1000-150000.

[0028] It should be noted that in the present application, the higher the molecular weight of the polymer, the better its mechanical properties, but its solubility will deteriorate accordingly; similarly, the lower the molecular weight, the worse its performance, but the solubility will increase, so the optimal molecular weight is around 50,000.

[0029] In one implementation of the present application, the polymer dispersibility index of the polymer is 1.0-10.0.

[0030] It should be noted that in the present application, the smaller the polymer dispersibility index (PDI) value is, the narrower and more consistent the molecular weight distribution of the polymer is; however, due to its own rigid structure, the prepared polymer has uneven molecular weight; in short, the lower the PDI value of the prepared polymer, the better.

[0031] In one implementation of the present application, the crosslinking agent is a photo-initiated crosslinking agent and / or a thermally-initiated crosslinking agent.

[0032] It should be noted that the key to the present application is to use a crosslinking agent to crosslink the polymer in situ to form a three-dimensional binder network structure for ion and electron transport; the specific crosslinking method can be photo-induced crosslinking, or heat-induced crosslinking, or a combination of the two. Correspondingly, the crosslinking agent used in the photo-induced crosslinking reaction is a photo-induced crosslinking agent, and the crosslinking agent used in the heat-induced crosslinking reaction is a heat-induced crosslinking agent.

[0033] In one implementation of the present application, the photoinitiator crosslinking agent is at least one of the polymers shown in Formula 9 to Formula 15;

[0034]

[0035] In Formula 9 to Formula 15, n is an integer greater than 0.

[0036] In one implementation of the present application, the heat-initiated crosslinking agent is at least one of the polymers shown in Formula 16 to Formula 21;

[0037]

[0038] In Formula 16 to Formula 21, n is an integer greater than 0.

[0039] It should be noted that the cross-linking agents used in this application can be purchased from regular channels. The key to the photoinitiator cross-linking agent used in this application is that it contains two to four thiol groups as active reaction sites for subsequent photo-cross-linking reactions; in addition, it contains ethoxy groups as sites to promote ion diffusion.

[0040] In one implementation of the present application, the mass ratio of the polymer to the cross-linking agent is 0.5-100.

[0041] It should be noted that in the present application, the lower the ratio of polymer to cross-linking agent, the higher the proportion of cross-linking agent, the higher the degree of cross-linking of the binder after the in-situ cross-linking reaction, and the mechanical properties will be greatly improved; similarly, the larger the ratio of the two, the lower the proportion of cross-linking agent, the lower the degree of cross-linking of the obtained cross-linked binder, and the less obvious improvement in mechanical properties; for different application scenarios, the optimal value may be different. For example, in battery electrode sheets, due to the different sizes of active particles, the optimal mass ratio of polymer to cross-linking agent is different; in short, the best improvement in the mechanical properties of the actual system is used as the standard in different application scenarios.

[0042] The second aspect of the present application discloses a battery slurry containing the binder system of the present application.

[0043] It should be noted that, due to the use of the binder system of the present application, the battery slurry of the present application can form a three-dimensional binder network structure to effectively fix the electrode material; thereby, the high specific capacity negative electrode can still maintain good contact with the binder after particle pulverization and maintain electrochemical activity.

[0044] It can be understood that the key to the battery slurry of the present application is that it contains the binder system of the present application. As for other components, reference can be made to existing battery slurries. On this basis, the battery slurry of the present application can also contain other conventional binders as auxiliary.

[0045] In one implementation of the present application, the solvent of the battery slurry of the present application is water, wherein the amount of the binder system is 0.1-30% of the total weight of the battery slurry.

[0046] In one implementation of the present application, the viscosity of the battery slurry is 1-10000 mPa.

[0047] It should be noted that the binder system of the present application, its dosage and the viscosity of the prepared battery slurry and other properties can refer to the existing binders and battery slurries. For example, the dosage of the binder system is 0.1-30% of the total weight of the battery slurry, and the viscosity of the battery slurry is 1-10000mPa, etc.

[0048] It should also be noted that in the battery slurry of the present application, the optimal mass ratio of polymer to cross-linker is related to the size of the electrode material and needs to be determined according to the actual application scenario; for example, for a pure silicon negative electrode material with a diameter of 30 nanometers, the optimal mass ratio of polymer to cross-linker is about 10, and for a silicon oxide negative electrode material with a diameter of 1 micron, the optimal value is about 25. According to the solubility of the polymer and the cross-linker in water, the mass ratio of the polymer to the cross-linker is 0.5-100. According to different usage scenarios, the viscosity of the slurry can be adjusted by changing the solid content of the polymer and the cross-linker in the slurry.

[0049] The third aspect of the present application discloses a battery pole piece containing the battery slurry of the present application.

[0050] It should be noted that the battery electrode of the present application, due to the use of the battery slurry of the present application, can still maintain good contact with the binder and maintain electrochemical activity after the high specific capacity negative electrode particles are pulverized, thereby solving the problems of reduced electrochemical activity and electrode collapse caused by the shedding of particles from the current collector after pulverization.

[0051] In one implementation of the present application, the battery electrode of the present application further contains an auxiliary adhesive.

[0052] In one implementation of the present application, the auxiliary binder is at least one of polyacrylic acid, lithium polyacrylate, sodium polyacrylate, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyvinyl alcohol, polyacrylamide, polyacrylonitrile, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, and acrylonitrile copolymers.

[0053] It should be noted that the electron / ion in-situ photocrosslinking binder of the present application accounts for 0.01wt%-50wt% of the total mass of the electrode. Adding different types of auxiliary binders can improve the mechanical properties of the electrode to meet different usage scenarios. Depending on the type of active material in the electrode, the proportion of the electron / ion in-situ photocrosslinking binder used in the electrode is different. For example, if there is a material that expands in volume during the electrochemical process, it is necessary to increase the proportion of the binder in the electrode sheet.

[0054] The fourth aspect of the present application discloses a method for preparing the battery pole piece of the present application, comprising coating the battery slurry on the current collector, placing the current collector in a nitrogen or argon environment, performing a cross-linking reaction by ultraviolet light and / or heating, and then drying to obtain the battery pole piece of the present application.

[0055] It should be noted that the preparation method of the present application is to first dissolve the cross-linking agent, polymer, electrode material and other components in water to prepare a battery slurry; after the battery slurry is coated, it is placed in a nitrogen or argon atmosphere, and subjected to photo-cross-linking reaction by ultraviolet light and / or thermal cross-linking reaction by heating, so that the cross-linking agent cross-links the polymer in situ to form a three-dimensional binder network structure, thereby obtaining the battery electrode of the present application.

[0056] It should also be noted that the in-situ photocross-linking binder for conducting electrons / ions used in the battery negative electrode of the present application has a content of 0.01-50wt% in the electrode, and the negative electrode material can be at least one of a silicon negative electrode, a silicon oxygen negative electrode, a silicon carbon negative electrode, and a carbon-based negative electrode.

[0057] In one implementation of the present application, for the photo-crosslinking reaction, the ultraviolet irradiation time is 1-360 min.

[0058] It can be understood that the time of ultraviolet irradiation is related to the light intensity of the ultraviolet lamp used. For ultraviolet lamps with stronger light intensity, the irradiation time can be shortened; for ultraviolet lamps with weaker light intensity, the irradiation time should be increased to complete the cross-linking reaction; in principle, as long as the cross-linking agent and the polymer can fully complete the photo-cross-linking reaction, the ultraviolet irradiation time is usually 1-360 minutes.

[0059] In one implementation of the present application, for the thermal cross-linking reaction, the heating temperature is 60-200° C. and the heating time is 1-24 hours.

[0060] It can be understood that the heating time is related to the heating temperature. For higher heating temperatures, the heating time can be shortened; for lower heating temperatures, the heating time should be increased to complete the cross-linking reaction; in principle, as long as the cross-linking agent and the polymer can fully complete the thermal cross-linking reaction, the heating time is usually 1-24 hours.

[0061] In one implementation of the present application, the drying temperature is 60-150°C.

[0062] It can be understood that the main function of drying is to remove the solvent, and the temperature is usually 60-150°C.

[0063] The fifth aspect of the present application discloses a battery containing the battery electrode of the present application.

[0064] It should be noted that the battery of the present application, due to the use of the battery electrode of the present application, effectively improves the cycle stability of the high specific capacity negative electrode material.

[0065] The sixth aspect of the present application discloses the application of the binder system of the present application in a solid-state battery.

[0066] The seventh aspect of the present application discloses a solid-state battery, comprising a positive electrode sheet, a solid electrolyte layer, a negative electrode sheet, and at least two electron and ion transport layers formed using the binder system of the present application, and the solid electrolyte layer is sandwiched between the two electron and ion transport layers and is in close contact with the solid electrolyte.

[0067] In one implementation of the present application, the solid electrolyte layer has an ion transport function.

[0068] In one implementation of the present application, the solid electrolyte layer is prepared using an organic solid electrolyte, an inorganic solid electrolyte, or an organic-inorganic composite solid electrolyte.

[0069] It should be noted that the solid-state battery of the present application constructs an electron and ion transport network in situ in its positive and negative electrode sheets through a binder system with electron and ion conducting functions, and the network can achieve close contact with the intermediate solid electrolyte layer, achieve molecular-level contact, and achieve a "wetting" effect. This effectively solves the problem of poor contact between traditional solid electrolytes and electrodes, and gives full play to the electrochemical properties of positive and negative electrodes. It can be understood that the key to this application is to use the binder system of this application in a solid-state battery. As for the specific positive electrode sheet, solid electrolyte layer, and negative electrode sheet, reference can be made to existing solid-state batteries.

[0070] The eighth aspect of the present application discloses the application of the binder system of the present application, or the battery slurry of the present application, or the battery pole piece of the present application in power lithium batteries or 3C consumer electronics lithium-ion batteries.

[0071] Due to the adoption of the above technical solution, the beneficial effects of this application are:

[0072] The binder system of the present application utilizes a cross-linking agent to in-situ cross-link a polymer to form a three-dimensional binder network structure; wherein the polymer serves as a conjugated main chain providing electron transport, and the cross-linking agent serves as a flexible cross-linking segment that is beneficial to ion diffusion, and the two initiate a cross-linking reaction through heat and / or light to form a three-dimensional electron and ion transport network; while ensuring high adhesion of the binder, the mechanical properties of the binder are maximized, providing sufficient mechanical properties for the battery pole piece to maintain electrode integrity, thereby improving the cycle stability of the high specific capacity negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 is a schematic diagram of the structure of the binder system in the embodiment of the present application being cross-linked by light or heat cross-linking reaction;

[0074] Figure 2 The electrochemical performance test results of the lithium ion battery negative electrode prepared by using the binder system CPFDP-COOLi prepared in Example 1 of the present application as a binder for a high-capacity silicon oxide negative electrode;

[0075] Figure 3 1 is a performance result diagram of the binder system CPFDP-COOLi prepared in Example 1 of the present application and the uncrosslinked conductive polymer PFDP-COOLi in Comparative Example 1 at different current densities (100 mA / g, 200 mA / g, 400 mA / g, 800 mA / g, 1600 mA / g and 200 mA / g) in a silicon oxide negative electrode battery, wherein the curves corresponding to the marks 0.1 A / g, 0.2 A / g, 0.4 A / g, 0.8 A / g, 1.6 A / g and 0.2 A / g are rate curves of the corresponding current densities;

[0076] Figure 4 The electrochemical performance test results of the lithium-ion battery negative electrode prepared by using the binder system CP3PFDP-COOLi prepared in Example 2 of the present application as a binder for a high-capacity nano-silicon negative electrode;

[0077] Figure 5 This is a performance result graph of the binder system CP3PFDP-COOLi prepared in Example 2 of the present application and the uncrosslinked conductive polymer PFDP-COOLi in Comparative Example 1 at different current densities (210mA / g, 420mA / g, 840mA / g, 1680mA / g, 3360mA / g, 4200mA / g and 420mA / g) in a nano-silicon negative electrode battery, wherein the curves corresponding to marks such as 0.21A / g, 0.42A / g, 0.84A / g, 1.68A / g, 3.36A / g, 4.2A / g and 0.42A / g are the rate curves of the corresponding current densities. DETAILED DESCRIPTION

[0078] Existing binder systems with electronic and ionic functions, such as binder systems blended with conductive polymers and polyethylene oxide, are simply physical mixtures of two components. They have poor mechanical properties and cannot provide sufficient mechanical properties to maintain electrode integrity, which hinders the practical application of such binder systems in batteries.

[0079] Based on the above problems, the present application creatively proposes to use two cross-linkable components to form a binder system to improve the mechanical properties, thereby providing sufficient mechanical properties to maintain the integrity of the electrode. Based on such an inventive concept, the inventors of the present application have creatively developed a new binder system that has both electron-conducting and ion-conducting functions after a lot of research and experiments, that is, a new binder system composed of 1) a cross-linking agent containing ethoxy units and 2) a polymer that has electron-conducting functions or has electron-conducting and ion-conducting functions, wherein the cross-linking agent has a thiol group and the polymer has an olefin group; and / or, both the cross-linking agent and the polymer have an olefin group.

[0080] The binder system of the present application, when used, utilizes heat and / or light to initiate a crosslinking reaction so that the crosslinking agent crosslinks the polymer in situ to form a three-dimensional binder network structure. In the three-dimensional binder network structure formed by the present application, the polymer serves as a conjugated main chain that provides electron transport, and the crosslinking agent serves as a flexible crosslinking segment that facilitates ion diffusion, thereby forming a three-dimensional electron and ion transport network.

[0081] Taking water-soluble polyfluorene conductive polymer as an example, its preparation method is as follows:

[0082] 1) According to the common Suzuki coupling reaction principle and reaction steps, one or more aromatic bromines and one or more boron esterified aromatic compounds (the molar ratio of bromine reaction sites to boron ester reaction sites is maintained at 1:1) are dispersed in an organic solvent to prepare solution A; and a base is dissolved in water to prepare a 2M base solution.

[0083] 2) Mix the solution A prepared in step 1) and the alkali solution, and add a phase transfer agent (eg Aliquant 336).

[0084] 3) The solution obtained in step 2) is subjected to 3-5 times of freezing and deoxygenation operation, and then a palladium catalyst is added under the protection of an inert gas, and the reaction is carried out in an oil bath at 60-150° C. for 1-240 hours, and the reaction is cooled to room temperature after completion of the reaction.

[0085] 4) pouring the reaction product obtained in step 3) into an alcohol solvent for precipitation and filtering, re-dissolving the crude product, and then pouring it into an alcohol solvent for precipitation and filtering, repeating 1-10 times, and then drying the purified product to obtain a main chain conjugated precursor polymer; wherein the solvent used for re-dissolution is one or more of anhydrous dichloromethane, chloroform and tetrahydrofuran.

[0086] 5) The precursor polymer obtained in step 4) is redissolved in an organic solvent, the organic solvent is one or more of anhydrous dichloromethane, chloroform and tetrahydrofuran, trifluoroacetic acid is added as a deprotecting agent, and the reaction is carried out at room temperature for 1 to 240 hours. After the reaction is completed, the organic solvent and the deprotecting agent are removed by rotary evaporation, an alkaline solution is added to react for 1 to 240 hours, and after the reaction is completed, the solvent is removed, and the product is washed 3 times with an alcohol solvent and dried to obtain Figure 1 The conductive polymer shown.

[0087] The method for preparing an in-situ photo-crosslinking adhesive for conducting electrons / ions by photo- / thermal-crosslinking reaction between a conductive polymer and a crosslinking agent comprises:

[0088] The prepared conductive polymer is dispersed in water, and a cross-linking agent rich in ethoxy structural units (purchased) is added. In an inert gas atmosphere such as nitrogen or argon, the cross-linking reaction is completed by irradiating with ultraviolet light for 1 min-360 min, or heating at 60-200 ° C for 1-24 h, and then the solvent is dried to obtain an in-situ photo-cross-linked adhesive that conducts electrons / ions.

[0089] It should be noted that in the above preparation method, the Suzuki coupling reaction in step 1), i.e., the Suzuki reaction, is a type of organic coupling reaction; step 2) solution A is mixed with an alkali solution, wherein the role of the alkali solution is to provide an alkaline reaction environment. In this application, the monomer needs to react in an alkaline environment. Without the participation of an alkali, it is difficult to react or even not react; in step 3), the catalyst mainly catalyzes the cross-coupling reaction of aromatic borate and bromoaryl, and the typical catalyst is tetrakis(triphenylphosphine)palladium; in step 4), the role of the deprotecting agent is to remove the tert-butyl group on the side chain of the polymer so as to react with the alkaline solution later, wherein the purpose of the alkaline solution reaction is to introduce Li, Na or K ions on the R anti-group to increase the water solubility of the conductive polymer in preparation for the subsequent cross-linking reaction. Taking water-soluble polyfluorene as an example, the precursor structure refers to the polyfluorene polymer that is not hydrolyzed after the polymerization of all monomers, and its side chain contains a tert-butyl group, and the polyfluorene refers to the polyfluorene structure with a carboxylate-containing side chain formed by the hydrolysis of the precursor structure. This method is a common method for synthesizing polyfluorene conductive polymers. The types of solvent, catalyst, and base in the reaction system will vary slightly depending on the type of monomer.

[0090] Preferably, in step 1), the organic solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, toluene, ethyl acetate and dioxane; and the base is sodium carbonate or potassium carbonate.

[0091] Preferably, in step 2), the concentration of solution A is 0.1-0.5 mol / L; the alkali is lithium carbonate, sodium carbonate and / or potassium carbonate, and the concentration of the alkali solution is 2 mol / L.

[0092] Preferably, in step 3), the volume ratio of solution A to alkali solution is 0.1-100; the volume ratio of the phase transfer agent Aliquant336 added to solution A is 0.01-1.

[0093] Preferably, in step 3), the inert gas is nitrogen or argon; in step 4), the alcohol is methanol or ethanol.

[0094] Preferably, in step 4), the volume ratio of the organic solvent to trifluoroacetic acid is 1 to 100; the alkaline solution is selected from at least one of potassium carbonate, sodium carbonate, lithium carbonate, potassium bicarbonate and sodium bicarbonate or lithium hydroxide, sodium hydroxide and potassium hydroxide; and the concentration of the alkaline solution is 0.01 to 10 mol / L.

[0095] The in-situ photo-crosslinked binder of the present invention for conducting electrons / ions can realize efficient crosslinking reaction (e.g., free radical reaction, thiol-ene click reaction) in-situ by means of heat / light initiation, and prepare a crosslinked binder with electron and ion transport function. And it can be effectively applied in batteries, such as in-situ construction of crosslinked electron and lithium ion transport network in the negative electrode, which provides simplicity, efficiency and controllability compared with the thermal crosslinking method. Uncrosslinked conductive polymers contribute to good dispersion of active materials in the slurry, thereby ensuring good uniformity in the electrode. After in-situ photo-crosslinking, the resulting polymer combines the flexibility of the polyether segment (rich in ethoxy units) and the rigidity of the polyfluorene segment to form an elastic binding network. At the same time, the electron percolation network constructed by the conjugated framework and the lithium ion transport channel provided by the crosslinked segment ensure stable charge transfer in the negative electrode. Due to the improvement of the mechanical property modulus, the cyclic expansion rate of the high-performance negative electrode is significantly reduced, and the elastic polymer network formed in situ not only retains the structural integrity of the electrode, but also helps to maintain the stability of the components and structures in the SEI. Utilizing this binder system, high-performance anode electrodes exhibit exceptional electrochemical performance.

[0096] The cross-linked binder of the present application, when used as a negative electrode conductive binder, can replace the conductive carbon black and binder parts in traditional lithium-ion batteries; wherein, the side chain of the conductive polymer has abundant carboxylic acid polar groups, which can achieve effective bonding to the particles; its conjugated main chain can serve as an electron transmission channel, which can provide a molecular-level conductive network; its cross-linked chain segment has abundant ethoxy units, which can accelerate the diffusion of lithium ions. The electron transmission segment and the ion diffusion segment are interwoven into a dense network to ensure the structural integrity of the negative electrode material and the effectiveness of the electron / ion transmission network in the electrode during the charge and discharge process of the battery, and improve the cycle stability of the electrode material. The conductive electron / ion binder of the present application is dispersed in an aqueous solution before cross-linking, which is not only green, environmentally friendly and safe, but also has simple components and is easy to regulate.

[0097] The present invention is further described in detail below by means of specific implementation modes in combination with the accompanying drawings. The following examples are only used to further illustrate the present application and should not be construed as limiting the present application.

[0098] Example 1

[0099] The synthesis steps of the monomer 2,7-dibromo-9,9-bis(tert-butyl 3-propionate)fluorene (M1, Formula 2) are as follows: 1mmol tetrabutylammonium bromide and 50mmol 2,7-dibromofluorene are added to 50ml toluene, 10ml of 50wt% potassium hydroxide aqueous solution is added dropwise, and stirred at room temperature for 1 hour. Then 120mmol of tert-butyl acrylate is added dropwise, stirred at room temperature for 12 hours, diluted with dichloromethane, washed three times with deionized water, dried and concentrated under reduced pressure. The monomer M1 is obtained by purification by column chromatography or recrystallization.

[0100]

[0101] The synthesis steps of the monomer 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborane)-9,9-bis(tert-butyl 3-propionate)fluorene (M2, Formula 2) are as follows: 30mmol CH3COOK, 10mmol monomer M1 and 25mmol bis(pinacol)diboron are added to 50ml dimethylformamide. In order to completely remove the residual oxygen in the bottle, the reaction liquid is frozen into a solid with liquid nitrogen, evacuated, filled with N2, and the process is repeated three times after thawing. Then, 300mg of catalyst Pd(dppf)2Cl2 is added under an inert gas atmosphere such as nitrogen or argon, reacted at 80℃ for 10h, cooled to room temperature, poured into deionized water, and extracted with dichloromethane. Wash with deionized water three times, dry and concentrate under reduced pressure. Purify by column chromatography or recrystallization to obtain monomer M2.

[0102]

[0103] Monomer 2,7-dibromo-9,9-di(penta-4-en-1-yl)-9H-fluorene (M DP , the synthesis steps of formula 1) are as follows: 5mmol 2,7-dibromofluorene and 0.5mmol phase transfer agent tetrabutylammonium bromide are dissolved in 20ml toluene. After injecting 50wt% sodium hydroxide solution and stirring for 1 hour, 12mmol 5-bromo-1-pentene is added dropwise, the solution is heated to reflux, and the reaction is allowed to proceed overnight under argon. After cooling, the mixture is extracted with ethyl acetate, and the organic phase is washed with 1M HCl solution, deionized water and saturated NaCl solution in sequence. The solvent in the organic phase is rotary evaporated to obtain a light yellow oily liquid. The product is purified by column chromatography using hexane as the eluent, and the solvent is evaporated to obtain a translucent oily crude product. The product is dissolved in ethyl acetate, recrystallized in methanol, purified, and dried in vacuo to obtain a solid product.

[0104]

[0105] Using M1, M2 and M DP The preparation of the conductive polymer of this example specifically includes:

[0106] 1) Add 1.5 mmol of monomer M1, 2 mmol of monomer M2 and 0.5 mmol of monomer M DP Dissolve in tetrahydrofuran to obtain solution A; prepare 10mL of 2mol / L Na2CO3 aqueous solution; the reaction is as follows:

[0107]

[0108] 2) Solution A and Na2CO3 aqueous solution are mixed, and 1 to 30 drops, about 100-3000 μL, of chain transfer agent Aliquant336 are added. The specific amount used in this example is 10 drops, i.e., about 1000 μL.

[0109] 3) The solution obtained in step 2) was subjected to three freezing and pumping operations to remove oxygen, and then 300 mg of tetrakis(triphenylphosphine)palladium was added under nitrogen protection, reacted at 120° C. for 72 h, and cooled to room temperature.

[0110] 4) The solution obtained in step 3) is poured into methanol for precipitation, filtered, dissolved in dichloromethane, and then precipitated in methanol again. After filtering, the process is repeated three times to obtain polyfluorene PFDP-Bu having a tert-butyl ester group on the side chain.

[0111] 5) The polyfluorene obtained in step 4) was added to a dichloromethane solution containing 15 wt% trifluoroacetic acid and stirred overnight. The excess solvent was then removed by rotary evaporation, and the mixture was washed three times with methanol to obtain a polyfluorene PFDP-COOH having a carboxylic acid group on the side chain, which was dissolved in 100 mL of a 0.5 M LiOH aqueous solution.

[0112] 6) Add the solution obtained in step 5) to a dialysis membrane (1000D) for dialysis, change the water every 12 hours, and repeat 10 times. After removing most of the water in the dialysate by vacuum rotary evaporation, freeze-drying is performed to obtain the final water-soluble polyfluorene binder PFDP-COOLi.

[0113] 7) Disperse 200 mg of the binder obtained in step 6) in 2 mL of deionized water, add 8 mg of 3,6-dioxa-1,8-octanedithiol (article number: Aladdin D154345) as a cross-linking agent, then add 1664 mg of silicon dioxide as a negative electrode material and 208 mg of conductive carbon black as a conductive agent, stir overnight to prepare a battery slurry. The battery slurry is coated on copper foil and irradiated with ultraviolet light for 1 hour to complete the photocrosslinking reaction and obtain a cross-linked binder network CPFDP-COOLi; then put it into an oven and vacuum dry it at 135°C for 12 hours, and then compact the cut pieces, which are the battery pole pieces in this example. The cross-linking reaction is schematically shown as follows:

[0114]

[0115] 8) Assemble the electrode obtained in step 7) into a half-cell, with lithium metal as the negative electrode, Celgard2600 as the separator, and the electrolyte being a mixture of 1.2M LiPF6 containing 10wt% FEC in EC / DEC (volume ratio 1:1), with an electrolyte addition amount of 60μL.

[0116] 9) After the half-battery obtained in 8) was left to stand at room temperature for 12 h, a charge and discharge test was performed under constant current conditions.

[0117] Example 2

[0118] 1) Monomer 2,7-dibromo-9,9-bis(3-tert-butyl propionate)fluorene (M1, Formula 2), monomer 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborane)-9,9-bis(3-tert-butyl propionate)fluorene (M2, Formula 2) and monomer 2,7-dibromo-9,9-di(penta-4-en-1-yl)-9H-fluorene (M DP The synthesis method of M1 (Formula 1) is the same as that of Example 1. The monomer 1,3,5-tri(4-bromophenyl)benzene (M3, Formula 8) was purchased from Beijing Innochem Technology Co., Ltd. (Article No.: InnochemA69606). 1.280 mmol of monomer M1, 2 mmol of monomer M2, 0.195 mmol of monomer M3 and 0.426 mmol of M DP Dissolve in the above tetrahydrofuran dispersion to obtain solution A; prepare 10mL of 2mol / L Na2CO3 aqueous solution. The reaction is as follows:

[0119]

[0120] 2) Solution A and Na2CO3 aqueous solution are mixed, and 1 to 30 drops, about 100-3000 μL, of chain transfer agent Aliquant336 are added. The specific amount used in this example is 10 drops, i.e., about 1000 μL.

[0121] 3) The solution obtained in step 2) was subjected to three freezing and pumping operations to remove oxygen, and then 300 mg of tetrakis(triphenylphosphine)palladium was added under nitrogen protection, reacted at 120° C. for 72 h, and cooled to room temperature.

[0122] 4) The solution obtained in step 3) is poured into methanol for precipitation, filtered, dissolved in dichloromethane, and then precipitated in methanol again. After filtering, the process is repeated three times to obtain polyfluorene P3PFDP-Bu having a tert-butyl ester group on the side chain.

[0123] 5) The polyfluorene obtained in step 4) was added to a dichloromethane solution containing 15 wt% trifluoroacetic acid and stirred overnight. The excess solvent was then removed by rotary evaporation, and the mixture was washed three times with methanol to obtain a polyfluorene P3PFDP-COOH having a carboxylic acid group on the side chain, which was dissolved in 100 mL of a 0.5 M LiOH aqueous solution.

[0124] 6) Add the solution obtained in step 5) to a dialysis membrane (1000D) for dialysis, change the water every 12 hours, and repeat 10 times. After removing most of the water in the dialysate by vacuum rotary evaporation, freeze-drying is performed to obtain the final water-soluble polyfluorene binder P3PFDP-COOLi.

[0125] 7) Disperse 200 mg of the binder obtained in step 6) in 2 mL of deionized water, add 20 mg of 3,6-dioxa-1,8-octanedithiol as a crosslinker, then add 440 mg of nano-silicon as a negative electrode material, and stir overnight. Coat on copper foil, irradiate with ultraviolet light for 1 hour, complete the photocrosslinking reaction to obtain a crosslinked binder network CP3PFDP-COOLi, then put it into an oven at 135°C and vacuum dry for 12 hours, then compact the cut pieces. The crosslinking reaction is shown as follows:

[0126]

[0127] 8) Assemble the electrode obtained in step 7) into a half-cell, with lithium metal as the negative electrode, Celgard2600 as the separator, and the electrolyte being a mixture of 1.2M LiPF6 containing 10wt% FEC in EC / DEC (volume ratio 1:1), with an electrolyte addition amount of 60μL.

[0128] 9) After the half-battery obtained in 8) was left to stand at room temperature for 12 h, a charge and discharge test was performed under constant current conditions.

[0129] Example 3

[0130] 1) Monomer 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane)-9,9-bis(tert-butyl 3-propionate)fluorene (M2, Formula 2) and monomer 2,7-dibromo-9,9-di(penta-4-ene-1-yl)-9H-fluorene (M DP, Formula 1) is synthesized in the same manner as in Example 1. Monomers 2,7-dibromo-9-fluorenone (M4, Formula 5), ​​2,7-dibromo-9,10-phenanthrenequinone (M5, Formula 6), and 2,7-dibromo-pyrene-4,5,9,10-tetraketone (M6, Formula 7) were purchased from Beijing Innochem Technology Co., Ltd. (Article No.: InnochemA07395, InnochemA34593, MacklinD756019). 4 mmol of monomer M2, 1 mmol of monomer M4, 1 mmol of monomer M5, 1 mmol of monomer M6, and 1 mmol of M DP Dissolve in the above tetrahydrofuran dispersion to obtain solution A; prepare 20mL of 2mol / L Na2CO3 aqueous solution. The reaction is as follows:

[0131]

[0132] 2) Solution A and Na2CO3 aqueous solution are mixed, and 1 to 30 drops, about 100-3000 μL, of chain transfer agent Aliquant336 are added. The specific amount used in this example is 20 drops, i.e., about 2000 μL.

[0133] 3) The solution obtained in step 2) was subjected to three freezing and pumping operations to remove oxygen, and then 600 mg of tetrakis(triphenylphosphine)palladium was added under nitrogen protection, reacted at 120° C. for 72 h, and cooled to room temperature.

[0134] 4) The solution obtained in step 3) is poured into methanol for precipitation, filtered, dissolved in dichloromethane, and then precipitated in methanol again. After filtering, the process is repeated three times to obtain polyfluorene NPFDP-Bu having a tert-butyl ester group on the side chain.

[0135] 5) The polyfluorene obtained in step 4) was added to a dichloromethane solution containing 15 wt% trifluoroacetic acid and stirred overnight. The excess solvent was then removed by rotary evaporation, and the mixture was washed three times with methanol to obtain polyfluorene NPFDP-COOH having a carboxylic acid group on the side chain, which was dissolved in 200 mL of a 0.5 M LiOH aqueous solution.

[0136] 6) Add the solution obtained in step 5) to a dialysis membrane (1000D) for dialysis, change the water every 12 hours, and repeat 10 times. After removing most of the water in the dialysate by vacuum rotary evaporation, freeze-drying is performed to obtain the final water-soluble polyfluorene binder NPFDP-COOLi.

[0137] 7) Disperse 200 mg of the binder obtained in step 6) in 2 mL of deionized water, add 20 mg of 3,6-dioxa-1,8-octanedithiol as a crosslinking agent, then add 440 mg of nano-silicon as a negative electrode material, and stir overnight. Coat on copper foil, irradiate with ultraviolet light for 1 hour, complete the photocrosslinking reaction to obtain a crosslinked binder network, then put it into an oven at 135°C for vacuum drying for 12 hours, and then compact the cut pieces. The reaction process is similar to that of Examples 1 and 2.

[0138] 8) Assemble the electrode obtained in step 7) into a half-cell, with lithium metal as the negative electrode, Celgard2600 as the separator, and the electrolyte being a mixture of 1.2M LiPF6 containing 10wt% FEC in EC / DEC (volume ratio 1:1), with an electrolyte addition amount of 60μL.

[0139] 9) After the half-battery obtained in 8) was left to stand at room temperature for 12 h, a charge and discharge test was performed under constant current conditions.

[0140] Example 4

[0141] 1) Monomer 2,7-dibromo-9,9-bis(3-tert-butyl propionate)fluorene (M1, Formula 2), monomer 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborane)-9,9-bis(3-tert-butyl propionate)fluorene (M2, Formula 2) and monomer 2,7-dibromo-9,9-di(penta-4-en-1-yl)-9H-fluorene (M DP , Formula 1) is synthesized in the same manner as in Example 1. Monomer 1,4-dibromobenzene (M7, Formula 4) was purchased from Beijing Inokai Technology Co., Ltd. (Article No.: Aladdin D104691). 1 mmol of monomer M1, 2 mmol of monomer M2, 0.5 mmol of monomer M7 and 0.5 mmol of M DP Dissolve in the above tetrahydrofuran dispersion to obtain solution A; prepare 10mL of 2mol / L Na2CO3 aqueous solution. The reaction is as follows:

[0142]

[0143] 2) Solution A and Na2CO3 aqueous solution are mixed, and 1 to 30 drops, about 100-3000 μL, of chain transfer agent Aliquant336 are added. The specific amount used in this example is 10 drops, i.e., about 1000 μL.

[0144] 3) The solution obtained in step 2) was subjected to three freezing and pumping operations to remove oxygen, and then 300 mg of tetrakis(triphenylphosphine)palladium was added under nitrogen protection, reacted at 120° C. for 72 h, and cooled to room temperature.

[0145] 4) The solution obtained in step 3) is poured into methanol for precipitation, filtered, dissolved in dichloromethane, and then precipitated in methanol again. After filtering, the process is repeated three times to obtain polyfluorene PhPFDP-Bu having a tert-butyl ester group on the side chain.

[0146] 5) The polyfluorene obtained in step 4) was added to a dichloromethane solution containing 15 wt% trifluoroacetic acid and stirred overnight. The excess solvent was then removed by rotary evaporation, and the mixture was washed three times with methanol to obtain a polyfluorene PhPFDP-COOH having a carboxylic acid group on the side chain, which was dissolved in 100 mL of a 0.5 M LiOH aqueous solution.

[0147] 6) Add the solution obtained in step 5) to a dialysis membrane (1000D) for dialysis, change the water every 12 hours, and repeat 10 times. After removing most of the water in the dialysate by vacuum rotary evaporation, freeze-drying is performed to obtain the final water-soluble polyfluorene binder PhPFDP-COOLi.

[0148] 7) Disperse 200 mg of the binder obtained in step 6) in 2 mL of deionized water, add 20 mg of 3,6-dioxa-1,8-octanedithiol as a crosslinking agent, then add 440 mg of nano-silicon as a negative electrode material, and stir overnight. Coat on copper foil, irradiate with ultraviolet light for 1 hour, complete the photocrosslinking reaction to obtain a crosslinked binder network, then put it into an oven at 135 ° C for 12 hours in vacuum, and then compact the cut pieces. The reaction process is similar to that of Examples 1 and 2.

[0149] 8) Assemble the electrode obtained in step 7) into a half-cell, with lithium metal as the negative electrode, Celgard2600 as the separator, and the electrolyte being a mixture of 1.2M LiPF6 containing 10wt% FEC in EC / DEC (volume ratio 1:1), with an electrolyte addition amount of 60μL.

[0150] 9) After the half-battery obtained in 8) was left to stand at room temperature for 12 h, a charge and discharge test was performed under constant current conditions.

[0151] Example 5

[0152] 1) Monomer 2,7-dibromo-9,9-bis(3-tert-butyl propionate)fluorene (M1, Formula 2), monomer 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborane)-9,9-bis(3-tert-butyl propionate)fluorene (M2, Formula 2) and monomer 2,7-dibromo-9,9-di(penta-4-en-1-yl)-9H-fluorene (M DPThe synthesis method of (formula 1) is the same as that of Example 1. The monomer 2,7-dibromo-9,9-bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl)-9H-fluorene (M8, formula 3) was purchased from Shanghai Bidex Pharmaceutical Technology Co., Ltd. (article number: Bidex BD01111180). 1 mmol of monomer M1, 2 mmol of monomer M2, 0.5 mmol of monomer M8 and 0.5 mmol of M DP Dissolve in the above tetrahydrofuran dispersion to obtain solution A; prepare 10mL of 2mol / L Na2CO3 aqueous solution. The reaction is as follows:

[0153]

[0154] 2) Solution A and Na2CO3 aqueous solution are mixed, and 1 to 30 drops, about 100-3000 μL, of chain transfer agent Aliquant336 are added. The specific amount used in this example is 10 drops, i.e., about 1000 μL.

[0155] 3) The solution obtained in step 2) was subjected to three freezing and pumping operations to remove oxygen, and then 300 mg of tetrakis(triphenylphosphine)palladium was added under nitrogen protection, reacted at 120° C. for 72 h, and cooled to room temperature.

[0156] 4) The solution obtained in step 3) is poured into methanol for precipitation, filtered, dissolved in dichloromethane, and then precipitated in methanol again. After filtering, the process is repeated three times to obtain polyfluorene EOPFDP-Bu having a tert-butyl ester group on the side chain.

[0157] 5) The polyfluorene obtained in step 4) was added to a dichloromethane solution containing 15 wt% trifluoroacetic acid and stirred overnight. The excess solvent was then removed by rotary evaporation, and the mixture was washed three times with methanol to obtain polyfluorene EOPFDP-COOH having a carboxylic acid group on the side chain, which was dissolved in 100 mL of a 0.5 M LiOH aqueous solution.

[0158] 6) Add the solution obtained in step 5) to a dialysis membrane (1000D) for dialysis, change the water every 12 hours, and repeat 10 times. After removing most of the water in the dialysate by vacuum rotary evaporation, freeze-drying is performed to obtain the final water-soluble polyfluorene binder EOPFDP-COOLi.

[0159] 7) Disperse 200 mg of the binder obtained in step 6) in 2 mL of deionized water, add 20 mg of 3,6-dioxa-1,8-octanedithiol as a crosslinking agent, then add 440 mg of nano-silicon as a negative electrode material, and stir overnight. Coat on copper foil, irradiate with ultraviolet light for 1 hour, complete the photocrosslinking reaction to obtain a crosslinked binder network, then put it into an oven at 135 ° C for 12 hours in vacuum, and then compact the cut pieces. The reaction process is similar to that of Examples 1 and 2.

[0160] 8) Assemble the electrode obtained in step 7) into a half-cell, with lithium metal as the negative electrode, Celgard2600 as the separator, and the electrolyte being a mixture of 1.2M LiPF6 containing 10wt% FEC in EC / DEC (volume ratio 1:1), with an electrolyte addition amount of 60μL.

[0161] 9) After the half-battery obtained in 8) was left to stand at room temperature for 12 h, a charge and discharge test was performed under constant current conditions.

[0162] Example 6

[0163] 1) Prepare the silicon dioxide electrode sheet of CPFDP-COOLi according to steps 1 to 7 in Example 1.

[0164] 2) According to step 1 to step 6 in Example 1, a conductive polymer PFDP-COOLi was prepared, and then 200 mg of the binder was dispersed in 2 mL of deionized water, 8 mg of 3,6-dioxa-1,8-octanedithiol was added as a cross-linking agent, and then 1664 mg of lithium iron phosphate was added as a positive electrode material and 208 mg of conductive carbon black as a conductive agent, and stirred overnight. Coated on aluminum foil, irradiated with ultraviolet light for 1 hour, completed the photocrosslinking reaction to obtain a cross-linked binder network, and then placed in an oven at 100 ° C for 12 hours in vacuum drying, and then compacted and cut. The reaction process is similar to that of Example 1.

[0165] 3) The obtained pole pieces are assembled into a solid-state battery, with the silicon oxide electrode as the negative electrode and the lithium iron phosphate electrode as the positive electrode. The LLZTO inorganic solid electrolyte sheet purchased from CLUDE is used as the middle electrolyte layer to assemble into a button-type solid-state battery.

[0166] 4) The button-type solid-state battery obtained in 8) was left to stand at 45° C. for 12 h, and then subjected to a charge and discharge test under constant current conditions.

[0167] Comparative Example 1

[0168] The synthesis steps of the uncrosslinked conductive polymer in this example are the same as step 1) to step 6) in Example 1.

[0169] 200 mg of conductive polymer PFDP-COOLi binder was dispersed in 2 mL of deionized water, and then 1000 mg of silicon dioxide was added as the negative electrode material, and stirred overnight. Coated on copper foil, and then placed in an oven at 135°C for 12 hours to obtain silicon dioxide electrode sheets, which were then compacted and cut into pieces.

[0170] 200 mg of conductive polymer PFDP-COOLi binder was dispersed in 2 mL of deionized water, and then 1000 mg of nano-silicon was added as the negative electrode material, and stirred overnight. Coated on copper foil, and then placed in an oven at 135°C for 12 hours under vacuum to obtain a nano-silicon electrode sheet, which was then compacted and cut into pieces.

[0171] The battery assembly and testing are consistent with step 8) and step 9) in Example 1.

[0172] The polymer film electronic conductivity (S cm -1 ) test, polymer membrane ionic conductivity (S cm -1 ) test, elastic modulus (GPa) test and elongation at break (%) test, the test method refers to the existing conventional pole piece test method, and the test results are shown in Table 1. The batteries assembled in the above embodiments and comparative examples were tested for cycle performance and rate performance. Both cycle performance measurement and rate performance measurement were performed using the Neware battery test system. All test results are shown in Table 1. The cycle performance test results of Example 1 are shown in Table 1. Figure 2 As shown, the rate performance test is as follows Figure 3 The cycle performance test results of Example 2 are shown in Figure 4 As shown, the rate performance test is as follows Figure 5 shown.

[0173] Figure 2 The electrochemical performance diagram of the negative electrode of a lithium-ion battery prepared by using the electron / ion conducting in-situ photocrosslinking binder CPFDP-COOLi in Example 1 of the present application as a binder for a high-capacity silicon oxide negative electrode; the cycle performance measurement was performed using a Neware battery test system. The voltage range of the half-cell is 0.01-1V (Li / Li + ); The results show that the cross-linked CPFDP-COOLi electrode sheet exhibits a higher discharge specific capacity, that is, it exhibits excellent cycle performance.

[0174] Figure 3 The performance results of the in-situ photocrosslinking binder CPFDP-COOLi of the electron / ion conductor prepared in Example 1 of the present application and the uncrosslinked conductive polymer PFDP-COOLi in Comparative Example 1 at different current densities (100mA / g, 200mA / g, 400mA / g, 800mA / g, 1600mA / g and 200mA / g) in the silicon oxide negative electrode battery are shown in the figure, wherein the curves corresponding to the marks of 0.1A / g, 0.2A / g, 0.4A / g, 0.8A / g, 1.6A / g and 0.2A / g are the rate curves of the corresponding current densities; the rate performance measurement is carried out using the Neware battery test system. The voltage range of the half-cell is 0.01-1V (Li / Li+ ); The results show that the cross-linked CPFDP-COOLi electrode sheet exhibits higher discharge specific capacity at different current densities, that is, it exhibits better rate performance.

[0175] Figure 4 The electrochemical performance diagram of the negative electrode of a lithium-ion battery prepared by using the electron / ion conducting in-situ photocrosslinking binder CP3PFDP-COOLi in Example 2 of the present application as a binder for a high-capacity nano-silicon negative electrode; the cycle performance measurement was performed using a Neware battery test system. The voltage range of the half-cell is 0.01-1V (Li / Li + ); The results show that the cross-linked CP3PFDP-COOLi electrode sheet exhibits a higher discharge specific capacity, that is, it exhibits excellent cycle performance.

[0176] Figure 5 This is a performance result diagram of the in-situ photo-crosslinked binder CP3PFDP-COOLi of the conductive electrons / ions prepared in Example 2 of the present application and the uncrosslinked conductive polymer PFDP-COOLi in Comparative Example 1 at different current densities (210mA / g, 420mA / g, 840mA / g, 1680mA / g, 3360mA / g, 4200mA / g and 420mA / g) in the nano-silicon negative electrode battery, wherein the curves corresponding to the marks 0.21A / g, 0.42A / g, 0.84A / g, 1.68A / g, 3.36A / g, 4.2A / g and 0.42A / g are the rate curves of the corresponding current densities. The rate performance measurement was carried out using the Neware battery test system. The voltage range of the half-cell is 0.01-1V (Li / Li + ); The results show that the cross-linked CP3PFDP-COOLi electrode sheet exhibits higher discharge specific capacity at different current densities, that is, it exhibits better rate performance.

[0177] Table 1 Electrochemical performance test results

[0178]

[0179] The results in Table 1 show that the electronic conductivity of the conductive polymer decreases slightly after the cross-linking reaction, but remains at 10 -2 The ionic conductivity of the polymer membrane is significantly improved, and the strength and toughness of the polymer membrane are improved. Therefore, in the half-cell cycle performance test with silicon monoxide as the negative electrode, the cycle performance is better than that of the uncrosslinked binder.

[0180] On the basis of Example 1, different cross-linking agents are further used to replace the 3,6-dioxa-1,8-octanedithiol in Example 1 in equal amounts. Specifically, the present application further uses tetra(ethylene glycol) disulfide (Formula 9) (Article No.: Aladdin T469021), bis(3-mercaptopropionic acid) ethylene glycol (Formula 10) (Article No.: Aladdin E404431), tetraethylene glycol bis(3-mercaptopropionic acid ester) (Formula 11) (Article No.: Wako 322-62592), bis(thioglycolic acid) ethylene glycol ester (Formula 11) (Article No.: Aladdin E302277), carbon dithiocarboxylic acid, O,O'-1,2-ethylene glycol ester (Formula 12) (Article No.: SAGECHEMS275523), 2-[3-(2-sulfonyloxy)-2,2-bis[(2-sulfonyloxy)methyl]propoxy]ethane-1-thiol (Formula 13) (Article No.: Aurora190.543.360), glycerol thioglycolate (Formula 14) (Hangzhou Shangjie Chemical Co., Ltd.), 2-[[(Mercaptoethyl [Acyl)oxy]methyl]-2-methyl-1,3-propanediyl di(thioglycolate) (Formula 14) (Article No.: AlfaACM10193983) and pentaerythritol tetrathioglycolate (Formula 15) (Article No.: AldrichXW101939942, etc.) were used to replace the 3,6-dioxa-1,8-octanedithiol in Example 1 as the binder system to prepare battery electrodes, and the battery was assembled and tested in the same manner as in Example 1.

[0181] The results show that the above cross-linking agents can utilize photo-click reactions to cross-link conductive polymers in situ to form a three-dimensional binder network structure. In the half-cell cycle performance test with silicon monoxide as the negative electrode, they all exhibited better cycle performance than the uncross-linked binder.

[0182] It can be understood that, in addition to the above cross-linking agents, other cross-linking agents rich in ethoxy units are also applicable to the present application as long as they can cross-link the conductive polymer of the present application in situ by means of a photo-click reaction.

[0183] On the basis of Example 1, an equal amount of a cross-linking agent for heat-induced cross-linking reaction is further used to replace the 3,6-dioxa-1,8-octanedithiol in Example 1. Specifically, the present application uses ethylene glycol divinyl ether (Formula 16) (Article No.: 1pchem 1P005Y9F), diethylene glycol divinyl ether (Formula 16) (Article No.: InnochemA70071), ethylene glycol diallyl ether (Formula 17) (Article No.: Macklin B964349), dimethylallyl ethylene glycol diether (Formula 18) (Article No.: Xiens E-0445431), 2-acrylic acid, 2-(vinyloxy)ethyl ester (Formula 19) (Article No.: Leyan 1176915), polyethylene glycol diacrylate (Formula 20) (Article No.: InnochemA98705), and ethylene glycol dimethacrylate (Formula 21) (Article No.: InnochemA01426) to replace the 3,6-dioxa-1,8-octanedithiol of Example 1 as a binder system to prepare a battery slurry. The battery slurry was coated on the copper foil, and then placed in an oven for vacuum drying at 150°C for 12 hours to complete the thermal cross-linking reaction and obtain a cross-linked adhesive network. The battery pole pieces were prepared and the battery was assembled and tested in the same manner as in Example 1.

[0184] The results show that the above cross-linking agents can utilize thermal free radical reactions to cross-link the conductive polymers in situ, forming a three-dimensional binder network structure for electron and ion transmission. In the half-cell cycle performance test with silicon monoxide as the negative electrode, they all exhibited better cycle performance than the uncross-linked binder.

[0185] The above specific examples are used to illustrate the present application, which is only used to help understand the present application and is not intended to limit the present application. For technicians in the technical field to which the present application belongs, they can also make some simple deductions, deformations or substitutions based on the ideas of the present application.

Claims

1. A binder system having the function of conducting electrons and ions, characterized in that: The invention comprises 1) a crosslinking agent containing ethoxy units and 2) a polymer having electron-conducting function or electron-conducting and ion-conducting function, and the crosslinking agent and the polymer respectively have groups that are crosslinked under light and / or heat conditions; when used, the crosslinking reaction is initiated by light and / or heat, so that the crosslinking agent crosslinks the polymer in situ to form a three-dimensional binder network structure for ion and electron transmission.

2. The binder system according to claim 1, characterized in that: The cross-linking agent has a mercapto group and the polymer has an olefin group; and / or, both the cross-linking agent and the polymer have an olefin group; Preferably, the polymer has groups and / or side chains for ion transport; Preferably, in the polymer, the group for ion transport is an ethoxy group, and the side chain for ion transport is a side chain containing an ethoxy group; Preferably, the polymer also has groups and / or side chains that increase viscosity; Preferably, in the polymer, the viscosity-increasing group is a carboxylic acid, and the viscosity-increasing side chain is a carboxylate side chain; Preferably, the polymer is a water-soluble polyfluorene and / or a water-soluble polyfluorene derivative; Preferably, the water-soluble polyfluorene derivative is a water-soluble homopolymer or copolymer formed by a fluorene unit of a water-soluble polyfluorene and at least one unit of benzothiadiazole, carbazole, or phenylacetylene; Preferably, the water-soluble polyfluorene is polymerized from the units shown in Formula 1 and Formula 2; The water-soluble polyfluorene derivative is a water-soluble homopolymer or copolymer formed by adding at least one unit of formulae 3 to 8 to the units of formulae 1 and 2; In Formula 1, Formula 2 and Formula 3, n is an integer greater than 0; in Formula 2, R is H, Li, Na or K; Preferably, the molecular weight of the polymer is 1000-150000; Preferably, the polymer has a polymer dispersibility index of 1.0-10.

0.

3. The binder system according to claim 1, characterized in that: The crosslinking agent is a photo-initiated crosslinking agent and / or a thermally initiated crosslinking agent; Preferably, the photoinitiator crosslinking agent is at least one of the polymers shown in Formula 9 to Formula 15; In Formula 9 to Formula 15, n is an integer greater than 0; Preferably, the heat-induced crosslinking agent is at least one of the polymers shown in Formula 16 to Formula 21; In Formula 16 to Formula 21, n is an integer greater than 0; Preferably, the mass ratio of the polymer to the cross-linking agent is 0.5-100.

4. A battery slurry comprising the binder system according to any one of claims 1 to 3.

5. A battery pole piece containing the battery slurry according to claim 4.

6. The method for preparing a battery pole piece according to claim 5, characterized in that: The process comprises coating the battery slurry on the current collector, placing the current collector in a nitrogen or argon environment, performing a cross-linking reaction by ultraviolet light and / or heating, and then drying to obtain the battery pole piece.

7. A battery comprising the battery electrode sheet according to claim 5.

8. Use of the binder system according to any one of claims 1 to 3 in solid-state batteries.

9. A solid-state battery, comprising a positive electrode sheet, a solid electrolyte layer, and a negative electrode sheet, characterized in that: It also comprises at least two electron and ion transport layers formed by the binder system according to any one of claims 1 to 3, and the solid electrolyte layer is sandwiched between the two electron and ion transport layers and is in close contact with the solid electrolyte.

10. The solid-state battery according to claim 9, characterized in that: The solid electrolyte layer has an ion transport function; Preferably, the solid electrolyte layer is prepared by an organic solid electrolyte, an inorganic solid electrolyte or an organic-inorganic composite solid electrolyte.

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