Self-repairing conductive binder and preparation method thereof, all-solid-state battery silicon-based negative electrode slurry, negative electrode and all-solid-state battery

Abstract

The invention belongs to the technical field of all-solid-state batteries, and particularly relates to a self-repairing conductive binder and a preparation method thereof, all-solid-state battery silicon-based negative electrode slurry, a negative electrode and an all-solid-state battery, and the binder is formed by blending polylipoic acid ionic gel, a conductive polymer and a dispersing agent; the mass ratio of the polylipoic acid ionic gel to the conductive polymer to the dispersing agent is 80: (5-20): (5-10); the polylipoic acid ionic gel is formed by performing concentration-induced autonomous ring opening polymerization on alpha-lipoic acid in the presence of ionic liquid. According to the self-repairable ion / electron double-conductive adhesive provided by the invention, due to the self-repairing capability, the self-repairable ion / electron double-conductive adhesive can cope with mechanical damage and crack or deformation of an electrode in a repairing cycle process, and enough ion / electron conductivity can promote ion / electron transfer between the electrode and an electrolyte. Therefore, the solid-state battery containing the binder has improved specific capacity and cycling stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state batteries, and specifically relates to a self-repairing conductive adhesive and a preparation method thereof, an all-solid-state battery silicon-based negative electrode slurry, a negative electrode and an all-solid-state battery. Background Art

[0002] Liquid lithium-ion battery systems have gradually reached a bottleneck in their material systems. Energy density struggles to exceed 350Wh / kg, while liquid electrolytes pose safety concerns. Compared to liquid batteries, all-solid-state batteries utilize solid-state electrolytes instead of liquid electrolytes. The anode is upgraded from graphite to silicon-based / lithium metal, and the cathode is upgraded from high-nickel to ultra-high nickel / lithium nickel manganese oxide / lithium-rich manganese-based. These batteries can achieve high energy density and superior safety, representing the future development direction of lithium batteries. However, due to the solid electrolyte, solid-state batteries face technical challenges such as low conductivity leading to slow charge and discharge rates, poor solid-solid interface stability leading to battery failure, and difficulty balancing the overall performance of various electrolyte types. Interface issues have always been a major bottleneck for all-solid-state batteries. The electrolyte interface shifts from a soft solid-liquid contact to a hard solid-solid contact, resulting in high interface resistance, poor rate performance, and poor cycling stability due to interfacial stress and side reactions between the electrolyte and the electrode. Therefore, improving interfacial mass transfer and stability is particularly important for solid-state batteries.

[0003] In all-solid-state batteries, binders stabilize the electrode structure, enhance carrier transport, and connect components to regulate the solid-state electrolyte interface, making them key to developing all-solid-state batteries with higher energy density. Traditional liquid battery binders, such as polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and polyacrylic acid (PAA), offer only adhesion properties, poor mass transfer capabilities, and a lack of self-healing capabilities. They also cannot alleviate interfacial stress to ensure interface stability, making them unsuitable for all-solid-state batteries. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a self-healing conductive adhesive and a preparation method thereof, an all-solid-state battery silicon-based negative electrode slurry, a negative electrode and an all-solid-state battery. The adhesive of the present invention not only has adhesion ability (attributed to: having many polar groups), but also has a certain self-healing ability, which can repair the electrode structure rupture caused by the deformation of the active material during the cycle, ensure the stability of the electrode structure and interface, improve the cycle performance, and it has a certain ion / electron transmission ability, reduce the interface resistance, and improve the rate performance.

[0005] The present invention is specifically implemented through the following technical solutions.

[0006] The present invention provides a self-repairing conductive adhesive, more specifically, a self-repairing ion / electronic dual conductive adhesive formed by blending polylipoic acid ion gel, a conductive polymer and a dispersant.

[0007] The mass ratio of the polylipoic acid ion gel, the conductive polymer and the dispersant is 80:5~20:5~10; Polylipoic acid ion gel is formed by concentration-induced spontaneous ring-opening polymerization of α-lipoic acid in the presence of ionic liquid.

[0008] Preferably, the preparation method of polylipoic acid ion gel comprises the following steps: Alpha-lipoic acid (abbreviated as TA) is dissolved in anhydrous ethanol to prepare a first mixed solution.

[0009] The ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate (abbreviated as [EMI][ES]) is added dropwise into the first mixed solution and stirred to obtain the polylipoic acid ion gel.

[0010] Preferably, the molar ratio of α-lipoic acid to the ionic liquid 1-ethyl-3-methylimidazole ethyl sulfate is 5-10:1, the mass ratio of α-lipoic acid to anhydrous ethanol is 1-5:1, and the stirring time is 5 min.

[0011] Preferably, the conductive polymer is one or both of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) and sulfonated polyaniline; and the dispersant is one or both of hydroxypropyl cellulose and ethyl cellulose.

[0012] The present invention provides a method for preparing the above-mentioned self-repairing conductive adhesive, comprising the following steps: Using ethanol as solvent, polylipoic acid ion gel, dispersant and conductive polymer are mixed evenly to prepare a self-healing conductive adhesive. More preferably, the specific mixing steps are:

[0013] The polylipoic acid ion gel is diluted with ethanol to 10 wt.% to 25 wt.% to obtain a polylipoic acid ion gel solution.

[0014] 0.5 wt % to 5 wt % of a dispersant ethanol solution was added to the polylipoic acid ion gel solution and stirred uniformly to prepare a second mixed solution.

[0015] A conductive polymer is added to the second mixed solution and stirred evenly to prepare a self-repairing conductive adhesive.

[0016] The mass ratio of polylipoic acid ion gel, conductive polymer and dispersant is 80:5~20:5~10.

[0017] The present invention provides a silicon-based negative electrode slurry for an all-solid-state battery, which is prepared by dispersing an active material, a conductive additive and the above-mentioned binder in ethanol. In the mixture consisting of the active material, the conductive additive and the binder, the mass fraction of the active material is 92% to 96%, the mass fraction of the conductive additive is 1% to 2%, and the remainder is the binder, which together account for 100%. In the negative electrode slurry, the solid content is 30wt.% to 55wt.%.

[0018] The present invention provides a silicon-based negative electrode for an all-solid-state battery, comprising a current collector and a negative electrode material attached to the current collector. The negative electrode material is obtained by coating the above-mentioned all-solid-state battery negative electrode slurry on the current collector and drying it. The coating surface density is 2 mg / cm 2 ~8mg / cm 2 .

[0019] The present invention provides an all-solid-state battery, comprising a positive electrode plate, an electrolyte layer and a negative electrode plate arranged in sequence, wherein the negative electrode plate is formed by pressing the above-mentioned all-solid-state battery silicon-based negative electrode.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a self-healing conductive adhesive. The adhesive is formed by blending a polylipoic acid ion gel with a conductive polymer and a dispersant. The polylipoic acid ion gel is formed by concentration-induced self-ring-opening polymerization of the natural small molecule α-lipoic acid (TA) in the presence of an ionic liquid. The presence of the ionic liquid forms COOH···O=S hydrogen bonds with TA, preventing further depolymerization of the poly-TA, thereby forming a stretchable ion gel with conductive and self-healing properties. The addition of a small amount of conductive polymer enhances the system's ion / electron transport capabilities. Application of this adhesive in the negative electrode of an all-solid-state battery can stabilize the electrode structure, enhance carrier transport, and connect various components to regulate the solid-electrolyte interface, thereby achieving a high-energy-density solid-state battery.

[0021] The all-solid-state battery using the binder has excellent rate performance and cycle stability. The preparation method of the binder of the present invention is environmentally friendly, simple and easy to implement, and the obtained binder has good stability and is suitable for large-scale preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 These are optical images of the adhesive prepared in Example 1 at different healing times in the self-healing performance test. DETAILED DESCRIPTION

[0023] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples and accompanying drawings. However, the examples are not intended to limit the present invention. The experimental methods and detection methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0024] The invention provides a repairable ion / electronic dual conductive adhesive. The self-repairing conductive adhesive is formed by blending polylipoic acid ion gel, a conductive polymer and a dispersant.

[0025] The polylipoic acid ion gel is formed by concentration-induced autonomous ring-opening polymerization of natural small molecule α-lipoic acid (TA) in the presence of ionic liquid.

[0026] In the present invention, the mass ratio of the polylipoic acid ion gel to the conductive polymer and the dispersant is 80:5-20:5-10, more preferably 80:10:10.

[0027] In the present invention, the presence of polylipoic acid ion gel ensures the binder possesses certain self-healing and ion-conducting capabilities, while the presence of carboxyl groups imparts strong adhesion. The presence of a conductive polymer imparts a certain degree of conductivity to the binder, and the presence of a dispersant ensures a more uniform electrode slurry. The self-healing conductive binder provided by the present invention enables all-solid-state batteries to exhibit excellent rate performance and cycling stability. The present invention limits the mass ratio of polylipoic acid ion gel to conductive polymer to dispersant to 80:5-20:5-10. Within this range, the overall performance of the binder can be improved.

[0028] Among them, the mechanism of polylipoic acid ion gel is as follows: Polylipoic acid ion gels are formed by concentration-induced spontaneous ring-opening polymerization of the naturally occurring small molecule α-lipoic acid (TA) in the presence of an ionic liquid. The ionic liquid forms COOH···O=S hydrogen bonds with TA, preventing further depolymerization of the poly-TA. This results in a stretchable ion gel with conductive and self-healing properties.

[0029] The present invention provides a method for preparing the self-healing conductive adhesive described in the above technical solution, comprising the following steps: (1) Add ethanol to dilute the polylipoic acid ion gel to 10 wt.%~25 wt.%, to obtain a polylipoic acid ion gel solution.

[0030] (2) Add dispersant ethanol solution (concentration 0.5wt%~5wt%) to the solution prepared in (1) and stir evenly.

[0031] (3) Adding a conductive polymer to the solution prepared in (2) and stirring evenly to obtain a self-healing conductive adhesive.

[0032] In the present invention, the dispersant is one or more of hydroxypropyl cellulose and ethyl cellulose.

[0033] The conductive polymer is one or more of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) and sulfonated polyaniline.

[0034] The mass ratio of the polylipoic acid ion gel to the conductive polymer and the dispersant is preferably 80:5-20:5-10, more preferably 80:10:10.

[0035] In the present invention, the preparation steps of the polylipoic acid ion gel are: Step 1: Dissolve TA in anhydrous ethanol and stir to form a yellow transparent solution.

[0036] Step 2: Add a certain amount of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([EMI][ES]) dropwise into the above solution and stir for 5 minutes to obtain polylipoic acid ion gel.

[0037] The mass ratio of TA to anhydrous ethanol is 1-5:1, more preferably 1:1, and the molar ratio of TA to [EMI][ES] is preferably 10-5:1, more preferably 10:2.

[0038] The present invention provides the use of the self-healing conductive adhesive described in the above technical solution, or the self-healing conductive adhesive prepared by the preparation method described in the above technical solution, in solid-state batteries, preferably for silicon-based anodes. The self-healing conductive adhesive provided by the present invention enables all-solid-state batteries to maintain excellent cycling stability and rate performance.

[0039] The present invention provides an all-solid-state battery negative electrode slurry, comprising an active material, a conductive additive and a binder; the binder is the self-healing conductive binder described in the above technical solution or the self-healing conductive binder prepared by the preparation method described in the above technical solution.

[0040] In the present invention, the mixture of active material, conductive additive, and binder comprises 92% to 96% by mass of active material, 1% to 2% by mass of conductive additive, and the remainder being binder, for a total of 100%. In the present invention, the active material preferably comprises one or more of silicon, silicon-carbon, and silicon-oxygen materials; and the conductive additive preferably comprises one or more of Super P, acetylene black, and Ketjen black.

[0041] In the present invention, the method for preparing the all-solid-state battery anode slurry preferably includes mixing an active material, a conductive additive, and a binder, and dispersing the mixture in ethanol by stirring to obtain the all-solid-state battery anode slurry. In the present invention, the solid content of the all-solid-state battery anode slurry (i.e., the total mass fraction of the active material, conductive additive, and binder) is preferably 30 wt.% to 55 wt.%, more preferably 45 wt.%.

[0042] The present invention provides an all-solid-state battery anode, comprising a current collector and a negative electrode material attached to the current collector; the negative electrode material is obtained by coating the all-solid-state battery anode slurry described in the above technical solution on the current collector and drying it. In the present invention, the coating surface density of the all-solid-state battery anode slurry on the current collector is 2 mg / cm 2 ~8mg / cm 2 In the present invention, the current collector preferably comprises copper foil. In the present invention, the thickness of the current collector is preferably 8 microns. In the present invention, the coating is preferably performed using an automatic coating machine. In the present invention, the drying is preferably vacuum drying.

[0043] The present invention also provides an all-solid-state battery comprising the all-solid-state battery anode described in the above technical solution. In the present invention, the preparation method of the all-solid-state battery preferably includes the following steps: placing the all-solid-state battery anode in an argon-filled glove box; using a lithium-indium alloy as a counter electrode; using a 10 mm diameter die to punch out a lithium sheet (150 microns thick) and an indium sheet (100 microns thick); forming the lithium-indium alloy under pressure; using Li6PS5Cl as a solid electrolyte; weighing 100 mg; grinding it twice in a mortar; placing it in a mold to evenly cover the electrolyte; and flattening it; placing the all-solid-state battery anode in the mold and co-pressing it with the solid electrolyte. The cut lithium and indium sheets are placed sequentially on the other side of the mold; the mold is placed on a mold frame; pressurizing it; slowly releasing the pressure; and tightening the screws to complete the assembly, thereby obtaining the all-solid-state battery.

[0044] The self-healing conductive adhesive provided by the present invention not only has the adhesion ability of ordinary adhesives (with many polar groups) but also has a certain self-healing ability. It can repair the electrode structure cracks caused by the deformation of the active material during the cycle, ensure the stability of the electrode structure and interface, and improve the cycle performance. It also has a certain ion / electron transmission ability, reduces the interface resistance, and improves the rate performance.

[0045] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Example 1 A method for preparing a self-repairing conductive adhesive, comprising the following steps: (1) Dissolve 1 g of TA in 1 g of anhydrous ethanol and stir to form a yellow transparent solution.

[0047] (2) 0.2 g of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([EMI][ES]) was added dropwise to the solution prepared in step (1) and stirred for 5 min to obtain polylipoic acid ion gel.

[0048] (3) The polylipoic acid ion gel prepared in step (2) was diluted to 20 wt.% by adding 3.8 g of ethanol to obtain a polylipoic acid ion gel solution.

[0049] (4) Add 3 g of hydroxypropyl cellulose ethanol solution (concentration 5 wt.%) to the polylipoic acid ion gel solution in step (3) and stir evenly.

[0050] (5) Add 10 g of PEDOT:PSS aqueous dispersion (concentration 1.5 wt.%) to the solution prepared in step (4) and stir evenly to obtain a self-healing conductive adhesive.

[0051] Example 2 A method for preparing a self-repairing conductive adhesive, comprising the following steps: (1) Dissolve 1 g of TA in 1 g of anhydrous ethanol and stir to form a yellow transparent solution.

[0052] (2) Add 0.15 g of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([EMI][ES]) dropwise into the solution of step (1) and stir for 5 min to obtain polylipoic acid ion gel.

[0053] (3) The polylipoic acid ion gel prepared in step (2) was diluted to 20 wt.% by adding 3.6 g of ethanol to obtain a polylipoic acid ion gel solution.

[0054] (4) Add 3.25 g of hydroxypropyl cellulose ethanol solution (concentration 5 wt.%) to the polylipoic acid ion gel solution in step (3) and stir evenly.

[0055] (5) Add 10 g of PEDOT:PSS aqueous dispersion (concentration 1.5 wt.%) to the solution prepared in step (4) and stir evenly to obtain a self-healing conductive adhesive.

[0056] Example 3 A method for preparing a self-repairing conductive adhesive, comprising the following steps: (1) Dissolve 1 g of TA in 1 g of anhydrous ethanol and stir to form a yellow transparent solution.

[0057] (2) Add 0.2 g of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([EMI][ES]) dropwise into the solution of step (1) and stir for 5 min to obtain polylipoic acid ion gel.

[0058] (3) The polylipoic acid ion gel prepared in step (2) was diluted to 20 wt.% by adding 3.8 g of ethanol to obtain a polylipoic acid ion gel solution.

[0059] (4) Add 3 g of hydroxypropyl cellulose ethanol solution (concentration 5 wt.%) to the polylipoic acid ion gel solution in step (3) and stir evenly.

[0060] (5) Add 8 g of PEDOT:PSS aqueous dispersion (concentration 1.5 wt.%) to the solution prepared in step (4) and stir evenly to obtain a self-healing conductive adhesive.

[0061] Example 4 A method for preparing a self-repairing conductive adhesive, comprising the following steps: (1) Dissolve 1 g of TA in 1 g of anhydrous ethanol and stir to form a yellow transparent solution.

[0062] (2) Add 0.2 g of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([EMI][ES]) dropwise into the solution (1) and stir for 5 min to obtain polylipoic acid ion gel.

[0063] (3) The polylipoic acid ion gel prepared in step (2) was diluted to 20 wt.% by adding 3.8 g of ethanol to obtain a polylipoic acid ion gel solution.

[0064] (4) Add 5 g of hydroxypropyl cellulose ethanol solution (concentration 5 wt.%) to the polylipoic acid ion gel solution in step (3) and stir evenly.

[0065] (5) Add 10 g of PEDOT:PSS aqueous dispersion (concentration 1.5 wt.%) to the solution prepared in step (4) and stir evenly to obtain a self-healing conductive adhesive.

[0066] Example 5 A method for preparing a self-repairing conductive adhesive, comprising the following steps: (1) Dissolve 1 g of TA in 1 g of anhydrous ethanol and stir to form a yellow transparent solution.

[0067] (2) Add 0.1 g of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([EMI][ES]) dropwise into the solution prepared in step (1) and stir for 5 min to obtain polylipoic acid ion gel.

[0068] (3) The polylipoic acid ion gel prepared in step (2) was diluted to 20 wt.% by adding 3.8 g of ethanol to obtain a polylipoic acid ion gel solution.

[0069] (4) Add 3 g of hydroxypropyl cellulose ethanol solution (concentration 5 wt.%) to the polylipoic acid ion gel solution prepared in step (3) and stir evenly.

[0070] (5) Add 10 g of PEDOT:PSS aqueous dispersion (concentration 1.5 wt.%) to the solution prepared in step (4) and stir evenly to obtain a self-healing conductive adhesive.

[0071] Comparative Example 1 Styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 3:2 as comparative example 1.

[0072] Comparative Example 2 The amount of ionic liquid added is too high. The specific preparation steps are: (1) Dissolve 1 g of TA in 1 g of anhydrous ethanol and stir to form a yellow transparent solution.

[0073] (2) 0.5 g of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([EMI][ES]) was added dropwise to the solution prepared in step (1) and stirred for 5 min to obtain polylipoic acid ion gel.

[0074] (3) The polylipoic acid ion gel prepared in (2) was diluted to 20 wt.% by adding 5 g of ethanol to obtain a polylipoic acid ion gel solution.

[0075] (4) Add 3 g of hydroxypropyl cellulose ethanol solution (concentration 5 wt.%) to the lipoic acid ion gel solution in step (3) and stir evenly.

[0076] (5) Add 10 g of PEDOT:PSS aqueous dispersion (concentration 1.5 wt.%) to the solution prepared in step (4) and stir evenly to obtain a self-healing conductive adhesive.

[0077] Comparative Example 3 Compared with Example 2, no conductive polymer is added, and the specific preparation steps are as follows: (1) Dissolve 1 g of TA in 1 g of anhydrous ethanol and stir to form a yellow transparent solution.

[0078] (2) Add 0.15 g of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([EMI][ES]) dropwise into the solution of step (1) and stir for 5 min to obtain polylipoic acid ion gel.

[0079] (3) The polylipoic acid ion gel prepared in step (2) was diluted to 20 wt.% by adding 3.6 g of ethanol to obtain a polylipoic acid ion gel solution.

[0080] (4) Add 3.25 g of hydroxypropyl cellulose ethanol solution (concentration 5 wt.%) to the polylipoic acid ion gel solution in step (3) and stir evenly to prepare a self-healing adhesive.

[0081] Test Case Electrochemical performance test: (1) The negative electrode active material silicon powder, the conductive additive (Super P) and the binder were mixed in a mass ratio of 96:1:3 and uniformly dispersed in ethanol by stirring to obtain a uniformly mixed lithium-ion battery negative electrode slurry with a solid content of 45 wt.%.

[0082] (2) Use an automatic coating machine to evenly coat the lithium-ion battery negative electrode slurry in (1) on an 8-micron thick copper foil to a coating thickness of 80 microns, and then place it in a vacuum drying oven to dry and remove the solvent; after drying, cut it into negative electrode sheets with a diameter of 10 mm.

[0083] (3) The negative electrode prepared in (2) was transferred to a glove box filled with argon and assembled into a solid-state battery. A lithium-indium alloy was used as the counter electrode. A 10 mm diameter die was used to punch out a lithium sheet (150 μm thick) and an indium sheet (100 μm thick) to form a lithium-indium alloy under pressure. Li6PS5Cl was used as the solid electrolyte. 100 mg was weighed and ground twice in a mortar. The mixture was placed in the mold to evenly cover the electrolyte and flattened. The negative electrode of the all-solid-state battery was placed in the mold and pressed together with the solid electrolyte. The cut lithium sheet and indium sheet were placed in sequence on the other side of the mold. The mold was placed on the mold frame, pressurized, and after slowly releasing the pressure, the screws were tightened to complete the assembly, thus obtaining an all-solid-state battery.

[0084] (4) The all-solid-state battery assembled in (3) is heated to 0.01~1.5V. Vs. Constant current charge and discharge tests were performed within the voltage range of Li+. After one cycle at a rate of 0.1 C, the charge and discharge cycle test was repeated at a rate of 1 C. The rate test was repeated at 0.1 C, 0.2 C, 0.4 C, 0.6 C, 0.8 C, 1 C, 2 C, and 0.1 C for 10 cycles each. Battery rate performance = 1 C capacity / 0.1 C capacity × 100%.

[0085] (5) The all-solid-state battery assembled in (3) is discharged at a constant current of 0.1C to 0.01V, charged at a constant current to 1.5V, and then charged at a constant voltage of 1.5V to a current of 0.05C. After standing for 5 minutes, the voltage V1 is recorded. Then, the battery is discharged at 0.1C for 30 seconds and the voltage V2 is recorded. The internal resistance DCIR of the battery after the first cycle is obtained by (V2 - V1) / (0.1C), which is used as the impedance of the all-solid-state battery.

[0086] The self-healing conductive adhesives of each embodiment and the comparative example were applied to the negative electrode and assembled into an all-solid-state battery using the test example method, and the electrochemical performance was tested. The specific results are shown in Table 1.

[0087] Table 1 Electrochemical cycle performance data of Examples 1 to 5 and Comparative Examples 1 to 3 As can be seen from the results of Table 1, the self-repairing conductive adhesive provided by the present invention is assembled into an all-solid-state battery with a first-week coulombic efficiency of more than 80%, a capacity retention rate of more than 80% after 500 cycles, and a rate performance of more than 78%. However, the binder SBR / CMC of Comparative Example 1 has a first-week coulombic efficiency of 77.1% and a capacity retention rate of only 20.3% after 500 cycles. It can be seen from this that the all-solid-state battery formed by the self-repairing conductive adhesive of the present invention has a relatively low internal resistance and excellent cycle stability and rate performance. It should be noted that in Comparative Example 2, during the preparation of the polylipoic acid ion gel, the amount of ionic liquid added is too high, which causes the performance of the all-solid-state battery to decline. The reason is that the addition of ionic liquid can regulate the mechanical properties of the ion gel, such as elongation, modulus and tensile strength. As the amount of ionic liquid added increases, the stretchability of the ion gel is significantly enhanced, while the modulus decreases. Therefore, when the amount of ionic liquid added is too high, the mechanical strength of the ion gel deteriorates and is insufficient to maintain the stability of the electrode structure, resulting in poor battery cycle performance and rate performance.

[0088] In addition, in order to prove that the adhesive prepared by the present invention has a self-repairing function, the following self-repairing performance test was also carried out: the adhesive obtained in Example 1 was used to prepare an electrode by the above-mentioned test method. After a clear mark was scratched on the electrode with a scalpel, it was placed at room temperature without applying external force. When the healing time was 0h, 2h and 4h, the repair of the scratch on the sample was observed using an optical microscope. The self-repairing performance was as follows: Figure 1 As shown, when the healing time is 0 h, the scratches on the sample are clearly visible, when the healing time is 2 h, the scratches become lighter and partially repaired, and when the healing time is 4 h, the scratches on the sample disappear and are completely repaired, indicating that the adhesive prepared by the present invention has a self-repairing function.

[0089] Therefore, the self-healing conductive binder provided by the present invention can repair electrode structural cracks caused by deformation of the active material during cycling, ensuring electrode structural and interface stability and improving cycling performance. Furthermore, it possesses a certain ion / electron transport capacity, reduces interfacial resistance, and enhances rate performance. The self-healing conductive binder provided by the present invention is environmentally friendly, and its structure is easily controllable, effectively meeting the requirements for negative electrode preparation and production.

[0090] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, such changes and modifications are intended to be included.

Claims

1. A self-repairing conductive adhesive, characterized in that: It is formed by blending polylipoic acid ion gel, conductive polymer and dispersant; The mass ratio of the polylipoic acid ion gel, the conductive polymer and the dispersant is 80:5~20:5~10; Polylipoic acid ion gel is formed by concentration-induced spontaneous ring-opening polymerization of α-lipoic acid in the presence of ionic liquid.

2. The self-healing conductive adhesive according to claim 1, characterized in that: The preparation method of polylipoic acid ion gel comprises the following steps: dissolving α-lipoic acid in anhydrous ethanol to prepare a first mixed solution; The ionic liquid 1-ethyl-3-methylimidazole ethyl sulfate is added into the first mixed solution and stirred to obtain the polylipoic acid ion gel.

3. The self-repairing conductive adhesive according to claim 2, characterized in that: The molar ratio of α-lipoic acid and ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate is 5-10:1, the mass ratio of α-lipoic acid and anhydrous ethanol is 1-5:1, and the stirring time is 5 min.

4. The self-healing conductive adhesive according to claim 1, characterized in that The conductive polymer is one or two of poly(3,4-ethylenedioxythiophene), poly(styrenesulfonic acid), and sulfonated polyaniline; The dispersant is one or both of hydroxypropyl cellulose and ethyl cellulose.

5. The method for preparing the self-repairing conductive adhesive according to any one of claims 1 to 4, characterized in that: The following steps are involved: Using ethanol as solvent, polylipoic acid ion gel, dispersant and conductive polymer are uniformly mixed to prepare a self-healing conductive adhesive; The mass ratio of polylipoic acid ion gel, conductive polymer and dispersant is 80:5~20:5~10.

6. A silicon-based negative electrode slurry for an all-solid-state battery, characterized in that: The active material, the conductive additive and the binder according to any one of claims 1 to 4 are dispersed in ethanol. In the mixture consisting of the active material, the conductive additive and the binder, the mass fraction of the active material is 92% to 96%, the mass fraction of the conductive additive is 1% to 2%, and the remainder is the binder, which is 100% in total.

7. A silicon-based negative electrode for an all-solid-state battery, characterized in that: The invention comprises a current collector and a negative electrode material attached to the current collector, wherein the negative electrode material is obtained by coating the negative electrode slurry of the all-solid-state battery according to claim 6 on the current collector and drying it, and the coating surface density is 2 mg / cm 2 ~8mg / cm 2 .

8. An all-solid-state battery, characterized in that: It comprises a positive electrode plate, an electrolyte layer and a negative electrode plate arranged in sequence, and the negative electrode plate is formed by pressing the all-solid-state battery silicon-based negative electrode according to claim 7.

Images