Adhesive, silicon negative electrode, all-solid-state battery and preparation method of all-solid-state battery

Abstract

The invention provides an adhesive, a silicon negative electrode, an all-solid-state battery and a preparation method, and belongs to the technical field of solid-state batteries. According to the method, acrylic acid-2-hydroxyethyl ester, acrylic acid and polyethylene glycol monomethyl ether methacrylate triblock copolymer PHAP is prepared through free radical polymerization, and in the preparation process, hydrogen bonds with different bond energy are formed through a large number of phenolic hydroxyl groups in small molecule tea polyphenol, the PHAP and hydroxyl groups and carboxyl groups of an n-type conductive polymer; when the adhesive is applied to a silicon negative electrode and the volume of the silicon negative electrode expands in the circulation process, hydrogen bonds of the adhesive are sequentially broken from low bonding energy to high bonding energy, so that stress concentration generated by the silicon negative electrode in the circulation process is dissipated step by step, an energy consumption buffer layer is formed, the stability of the silicon negative electrode is improved, small cracks are reduced, and the service life of the silicon negative electrode is prolonged. The occurrence of vertical net-shaped large cracks is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state battery energy storage materials, and relates to an adhesive, a silicon negative electrode, an all-solid-state battery, and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have been widely used in electronic communications, new energy vehicles and other fields due to their advantages such as high energy power density, long cycle life and environmental protection. However, safety issues have gradually attracted people's attention. Traditional liquid batteries use flammable and volatile organic liquid electrolytes, which have certain unsafe characteristics.

[0003] All-solid-state batteries (ASSBs) use solid electrolytes, which have higher energy density and safety compared to traditional liquid batteries (LIBs). They are considered to be the next generation of rechargeable battery systems. Currently, the main solid electrolytes include sulfide-based, oxide-based and polymer-based solid electrolytes. Among them, sulfide-based solid electrolytes (SE) are popular due to their high ionic conductivity (>1mS·cm -1 ) has attracted great attention. Lithium metal is considered the ultimate negative electrode material for ASSBs due to its low electrochemical potential and high theoretical capacity. However, the abnormal growth of lithium dendrites hinders its practical application in ASSBs. Silicon has a high theoretical capacity (Li 15 Si4: ~3590mAh·g -1 ) and relatively low electrochemical potential, abundant natural resources, low cost, and environmental friendliness make silicon a promising anode material for ASSBs. However, the inherent disadvantages of silicon anodes have hindered their commercial application in all-solid-state batteries. Specifically, the low intrinsic conductivity and slow lithium-ion diffusion kinetics limit the rate performance of silicon anodes, and the significant volume expansion (greater than 300%) and contraction of silicon anodes during cycling generate huge mechanical stress, leading to electrode fracture and pulverization. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an adhesive, a silicon negative electrode and an all-solid-state battery and a preparation method to solve the problems of volume expansion and low conductivity of the silicon negative electrode in the all-solid-state battery in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An adhesive is prepared by reacting a small molecule crosslinking agent, an n-type conductive polymer, and a triblock copolymer PHAP. The small molecule crosslinking agent has a phenolic hydroxyl group, and the triblock copolymer PHAP has the structural formula:

[0007]

[0008] Among them, the range of x is 30-90, the range of y is 30-90, the range of z is 60-150, and n is 10-30.

[0009] A further improvement of the present invention is:

[0010] Preferably, the small molecule cross-linking agent is any one of tea polyphenols or tannic acid.

[0011] Preferably, the n-type conductive polymer is any one of poly(benzofurandione) or poly(benzofurandione).

[0012] A method for preparing the above adhesive comprises the following steps: dissolving a small molecule crosslinking agent in water to obtain a crosslinking agent solution; mixing the crosslinking agent solution, an n-type conductive polymer solution and a PHAP solution, and reacting the mixed mixture to obtain an adhesive.

[0013] Preferably, the mass ratio of the PHAP: small molecule cross-linking agent, and n-type conductive polymer is (9-27):1:(9-18).

[0014] Preferably, the reaction temperature is 25-30° C., and the reaction time is 3-5 hours.

[0015] Preferably, the preparation method of PHAP is:

[0016] Step 1, dissolving 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate in a mixed solution of N,N-dimethylformamide and water, and stirring uniformly to obtain a homogeneous solution;

[0017] Step 2: adding an initiator to the homogeneous solution, freezing and thawing the solution several times, then heating the solution to cause a polymerization reaction, placing the entire reaction system in an ice-water bath to terminate the reaction and obtain a reaction product;

[0018] Step 3: After dialyzing and freezing the reaction product, a triblock copolymer PHAP is obtained.

[0019] Preferably, in step 1, the molar ratio of 2-hydroxyethyl acrylate, acrylic acid and polyethylene glycol monomethyl ether methacrylate is (1-3): (1-3): (2-5);

[0020] In step 2, the reaction temperature is 60-75° C., and the reaction time is 3-5 hours.

[0021] A silicon negative electrode comprises a coating slurry and a current collector, wherein the coating slurry is composed of silicon particles and the above-mentioned binder.

[0022] An all-solid-state battery comprises a positive electrode, the above-mentioned silicon negative electrode and a diaphragm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention discloses an adhesive for a negative electrode. The adhesive is formed by the reaction polymerization of a small molecule crosslinker, PHAP, and an n-type conductive polymer. The PHAP and the n-type conductive polymer contain a large number of hydroxyl and carboxyl groups. The large number of phenolic hydroxyl groups on the small molecule crosslinker can react with the hydroxyl and carboxyl groups, allowing the small molecule crosslinker to act as an intermediate to connect the PHAP and the n-type conductive polymer, forming a three-dimensional continuous ion-electron transport network. During the polymerization process, different types of hydrogen bonds are formed, such as C=O...HO-Ph, C=O...H-OOC, and C=O...HOC. Due to the different bond energies between different hydrogen bonds, a gradient hydrogen bond stress dissipation adhesive is ultimately formed. When the adhesive is applied to a silicon negative electrode, as the silicon particles expand during application, the hydrogen bonds gradually dissociate from weak to strong, achieving effective stress dissipation. This achieves a step-by-step dissipation of the stress concentration generated by the silicon negative electrode during cycling, suppresses the formation of cracks, and maintains the interface stability between the silicon negative electrode and the solid electrolyte and the structural stability within the silicon negative electrode. At the same time, the ultra-high conductivity of the n-type highly conductive polymer in the adhesive can provide an electron transmission path, achieve rapid electron transmission, and significantly improve the electron conductivity inside the silicon negative electrode.

[0025] Furthermore, one of the main components of the adhesive is a triblock copolymer composed of 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate monomers. The adhesive constructs a three-dimensional continuous ionic and electronic conductive network, creating gradient hydrogen bonds through small molecule crosslinking. The ether bonds rich in polyethylene glycol monomethyl ether methacrylate provide lithium ion transport pathways, enabling rapid ion transport, while the carboxyl functional groups of acrylic acid ensure strong adhesion between the adhesive and the silicon particles and current collector.

[0026] The present invention also discloses a method for preparing an adhesive for silicon negative electrode materials of all-solid-state batteries. The preparation method first dissolves 2-hydroxyethyl acrylate, acrylic acid and polyethylene glycol monomethyl ether methacrylate monomers in a mixed solution of N,N-dimethylformamide and deionized water, then initiates a polymerization reaction with an initiator to generate a triblock copolymer, and forms hydrogen bonds of different bond energies with small molecules and n-type conductive polymers to generate a gradient hydrogen bond stress dissipation type high ionic electronic conductivity adhesive. The preparation method generates a polymer by copolymerizing 2-hydroxyethyl acrylate, acrylic acid and polyethylene glycol monomethyl ether methacrylate monomers, and forms gradient hydrogen bonds through small molecule connection. The preparation method is simple, has high ionic electronic conductivity, strong adhesion, adopts simple free radical polymerization, and is suitable for large-scale preparation.

[0027] The present invention discloses a silicon anode, which includes a coating slurry and a current collector. The coating slurry is composed of silicon particles and the above-mentioned adhesive. The adhesive forms hydrogen bonds with different bond energies with PHAP and hydroxyl and carboxyl groups of an n-type conductive polymer through a large number of phenolic hydroxyl groups of a small molecule cross-linking agent. When the volume of the silicon anode expands during the cycle, the gradient hydrogen bonds are broken step by step during the cycle of the silicon anode, dissipating the stress concentration generated by the silicon anode during the cycle, suppressing the generation of vertical network cracks, and maintaining the interface stability between the silicon anode and the solid electrolyte and the structural stability inside the silicon anode.

[0028] The present invention also discloses a sulfide all-solid-state battery silicon anode based on the adhesive and a sulfide all-solid-state battery containing the silicon anode. Through the application of the present invention, the long-cycle performance of the battery is effectively improved, and an all-solid-state battery with high energy density and high current is successfully prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the chemical reaction for preparing PHAP adhesive in Example 1 of the present invention;

[0030] Figure 2 This is an infrared spectrum of the PHUP adhesive prepared in Example 1 of the present invention;

[0031] Figure 3 The long cycle performance of Example 1, Example 2, Example 3, and Comparative Example 1 and Comparative Example 2 under 1C of the present invention is shown;

[0032] Figure 4 This is the long cycle performance of Example 5 of the present invention at 2C;

[0033] Figure 5 This is the long cycle performance of Example 6 of the present invention at 0.5C;

[0034] Figure 6 Scanning electron microscope images of the electrodes of Example 1 of the present invention and Comparative Example 1 before and after 50 cycles;

[0035] Figure 7 This is a comparison diagram of the electronic conductance of Example 1 of the present invention and Comparative Examples 1 and 2;

[0036] Figure 8 The differential scanning calorimetry curves of Example 1 and Comparative Example 2 of the present invention are shown. DETAILED DESCRIPTION

[0037] The present invention is described in further detail below with reference to the accompanying drawings:

[0038] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0039] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0040] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0041] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0042] The first aspect of the present invention discloses an adhesive, which is prepared by physically crosslinking a small molecule crosslinking agent, an n-type conductive polymer, and PHAP. The structural formula of the PHAP is:

[0043]

[0044] Among them, the range of x is 30-90, the range of y is 30-90, the range of z is 60-150, and n is 10-30.

[0045] The small molecule cross-linking agent is selected based on the condition that it has abundant phenolic hydroxyl groups, and is any one of tea polyphenols and tannic acid.

[0046] The n-type conductive polymer is either poly(benzofurandione) or poly(benzofurandione). Poly(benzofurandione) comprises a benzene ring and two furandione units covalently linked to form a linear or cross-linked structure. When applied to a silicon anode as part of an adhesive, this material exhibits strong electron injection properties, thereby promoting electron mobility. Poly(benzofurandione) comprises a conjugated plane formed by the fusion of a benzene ring and furandione, which exhibits a strong ability to delocalize electrons within the molecule, thereby promoting electron transfer.

[0047] The second aspect of the present invention discloses a method for preparing an adhesive, comprising the following steps: dissolving a small molecule crosslinker in water to obtain a crosslinker solution; mixing the crosslinker solution, an n-type conductive polymer solution, and a triblock copolymer PHAP solution, and reacting the mixed mixtures to obtain a gradient hydrogen bond stress dissipation adhesive.

[0048] In some embodiments of the present invention, the mass ratio of the PHAP, the small molecule cross-linking agent, and the n-type conductive polymer is (9-27):1:(9-18).

[0049] In some embodiments of the present invention, the crosslinker mass fraction is 5-20%, the n-type conductive polymer mass fraction is 1-2%, and the PHAP mass fraction is 5-20%. The n-type conductive polymer solution is a solution of the n-type conductive polymer dissolved in water, and the triblock copolymer PHAP solution is a solution of PHAP dissolved in water.

[0050] In some embodiments of the present invention, the reaction temperature is 25-30° C., and the reaction time is 3-5 h.

[0051] In some embodiments of the present invention, the preparation method of PHAP is:

[0052] Step 1, dissolving 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate in a mixed solution of N,N-dimethylformamide and deionized water, wherein the molar ratio of 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate (PDMA) is (1-3):(1-3):(2-5), and stirring for 10-30 minutes to form a homogeneous solution;

[0053] Preferably, the ratio of the mixed solution of N,N-dimethylformamide and deionized water is (3-7): (3-7).

[0054] Preferably, the total mass fraction of the three monomers in the homogeneous solution is 10-30%.

[0055] Step 2: adding an initiator to the homogeneous solution, freezing it in liquid nitrogen, pumping it for 3-5 minutes, then introducing argon, thawing it in room temperature water, freezing and pumping it again, repeating three times to deoxygenate and introduce protective gas to prevent the inhibition of oxygen on the polymerization reaction, heating it to 60-75° C., maintaining it for 3-5 hours to allow the polymerization reaction to proceed, and cooling the product in an ice water bath to terminate the reaction, thereby producing a triblock copolymer;

[0056] Preferably, the initiator is any one of ammonium persulfate and potassium persulfate; preferably, the mass of the initiator is 0.5-1.5% of the mass of the solute.

[0057] Step 3: The solution after the polymerization reaction is dialyzed with deionized water for 2-4 days and freeze-dried using a freeze dryer to obtain a triblock copolymer PHAP, the structural formula of which is shown below:

[0058]

[0059] Among them, the range of x is 30-90, the range of y is 30-90, the range of z is 60-150, and n is 10-30.

[0060] It should be understood that in the above structural formula, the specific values of x, y and z are determined by controlling the reaction time to determine the content of each block in the triblock polymer, and the number of n is determined by the amount of polyethylene glycol monomethyl ether methacrylate contained at the time of purchase.

[0061] The third aspect of the present invention discloses a silicon negative electrode, comprising a current collector and a negative electrode slurry coated on the current collector; the negative electrode slurry is composed of a negative electrode active material and a binder; the negative electrode active material is silicon particles with a size of 30nm-1μm, and the binder is the above-mentioned binder.

[0062] In some embodiments of the present invention, the mass ratio of the negative electrode active material to the binder is (7-9):(1-3).

[0063] As a preferred solution, the ratio of negative electrode active material to binder is 8:2.

[0064] Preferably, the current collector is a copper foil with a thickness of 12 μm.

[0065] A fourth aspect of the present invention discloses an all-solid-state battery, comprising a positive electrode, a solid electrolyte and the above-mentioned silicon negative electrode.

[0066] The present invention also discloses an application of a sulfide all-solid-state battery silicon negative electrode for preparing a sulfide all-solid-state battery negative electrode. The solid electrolyte used in the sulfide all-solid-state battery is Li6PS5Cl (LPSC), Li 5.5 PS 4.5 Cl 1.5 He Li10 GeP2S 12 Any one or more of .

[0067] In some embodiments of the present invention, the preparation process of an all-solid-state half-cell based on a sulfide all-solid-state battery silicon negative electrode comprises the following steps:

[0068] Step 1: Add 160 mg of silicon particles and 1300 mg of a 3% solute binder (the solvent is water) to a mushroom box. The ratio of silicon particles to binder is 8:2, and the total mass fraction of silicon particles and binder in the slurry is 13%. Ball milling is carried out in a planetary ball mill at a speed of 300-350 rpm for 1 hour to fully mix the mixture to obtain a uniformly dispersed negative electrode slurry. Use an automatic coating agent to coat the slurry on a copper foil current collector with a coating thickness of 70-250 μm and a loading of 0.6-2.5 mg cm -2 After coating, the electrode was placed in a vacuum oven to completely evaporate the solvent to obtain the final electrode, which was then cut into electrode pieces with a diameter of 12 mm using a cutting machine. The active material loading was calculated by weighing the mass of the electrode piece minus the mass of the copper foil and the mass of the inactive material.

[0069] Step 2: Transfer the electrode sheet prepared in step 1 to a glove box filled with argon to assemble the sulfide all-solid-state battery half-cell. First, weigh 100 mg of sulfide solid electrolyte Li6PS5Cl (LPSC) and grind it twice in a mortar. Spread the ground powder in a mold, then press the solid electrolyte at 175 MPa for 1 minute. Then place the prepared negative electrode sheet in the mold. The active material contacts the solid electrolyte and is pressed at 175 MPa for 1 minute. Then, pressurize to 350 MPa and hold the pressure for 5 minutes. Unload after the pressure is maintained. Use a 12 mm diameter punch to cut a 150 μm thick ultra-thin lithium, a 100 μm thick indium, and a 100 μm thick ultra-thin stainless steel sheet. Place the indium sheet, lithium sheet, and ultra-thin stainless steel sheet in the solid electrolyte sheet in turn. The ultra-thin stainless steel sheet serves as the current collector. Assemble the mold and pressurize to 175 MPa. Hold the pressure for 1 minute. Lithium and indium form a lithium-indium alloy under pressure. Slowly release the pressure to 75MPa and tighten the screws, and the assembly of the sulfide all-solid-state half-cell is completed; slowly release the pressure to 10MPa and tighten the screws, and the assembly of the 10MPa sulfide all-solid-state half-cell is completed.

[0070] Step 3: Test the electrochemical performance of the half-cell assembled in step 2. The voltage window is set to -0.61V to 0.88V (0.01~1.5V, vs. Li + / Li), the theoretical specific capacity is set to 3500mAh·g -1, pre-cycled 3 times at a rate of 0.1C, and a long cycle test was performed at a rate of 1C. Before the start of the cycle and after 50 cycles, the battery was disassembled and the surface morphology of the negative electrode was observed using a scanning electron microscope (SEM) to study the changes in the negative electrode at different cycle stages.

[0071] The present invention is described in further detail below with reference to specific embodiments:

[0072] Example 1

[0073] (1) 2-Hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were prepared in a molar ratio of 1:1:2. 1.16 g of 2-Hydroxyethyl acrylate, 0.72 g of acrylic acid, and 2.88 g of polyethylene glycol monomethyl ether methacrylate were dissolved in a mixture of 10 mL of N,N-dimethylformamide (DMF) and 10 mL of deionized water at room temperature to form a homogeneous solution in a 50 mL Schlenk flask. The total mass fraction of the three monomers in the solution was 20%. 47.6 mg of initiator ammonium persulfate was added, where the mass of the initiator was 1% of the mass of the solute. The homogeneous solution was then frozen solid in liquid nitrogen, evacuated for 5 minutes, then introduced with argon, thawed in room temperature water, and frozen and evacuated again. This was repeated three times. The reaction flask was heated to 70°C and reacted for 4 hours. After the polymerization reaction, the product was cooled in an ice-water bath to terminate the reaction. The cooled solution was dialyzed in water for three days and freeze-dried for two days to obtain a pure triblock copolymer PHAP. The infrared spectra of the three monomers and PHAP are as follows Figure 2 As shown in the figure, it can be seen that 1711cm -1 and 1703cm -1 The peaks at 2869 cm-1 correspond to the C=O stretching vibration peaks of the ester group in the HEA group and the C=O stretching vibration peaks of the carboxyl group in the AA group. -1 and 2928cm -1 The peaks at 3460 cm correspond to the CH2 stretching peaks in PEGMA and the carboxyl stretching peaks in AA, respectively. -1 The peak at corresponds to the OH stretching peak in HEA. The successful synthesis of the triblock copolymer was confirmed by infrared spectroscopy. The copolymer was dissolved in water to prepare a 10% PHAP solution, poured into a mold, and the solvent was evaporated in an oven to form a film. The glass transition temperature of the copolymer was tested by differential scanning calorimetry (DSC). The results are as follows: Figure 8 shown.

[0074] (2) Tea polyphenols were dissolved in deionized water to prepare a 10% solution by mass. The 10% tea polyphenol solution and 1.5% PBFDO solution were added to the 10% PHAP solution by mass. The mixture was magnetically stirred at 25°C for 3 h to mix evenly. The mass ratio of PHAP, tea polyphenols and PBFDO was controlled to be 18:1:9 to obtain a gradient hydrogen bond stress dissipation adhesive PHAP-PBFDO. The glass transition temperature (Tg) of the polymer adhesive was tested by differential scanning calorimetry. The results are shown in FIG. Figure 8 As shown in Figure 2, the addition of small-molecule tea polyphenols and PBFDO to PHAP polymer significantly reduces the Tg of PHAP-PBFDO compared to PHAP. This is due to the formation of hydrogen bonds between the small-molecule tea polyphenols and the polymer chains and PBFDO, which physically crosslinks the PHAP polymer chains and reduces polymer chain entanglement. This enhances the mobility of the PHAP polymer chains and lowers the Tg of the polymer. Based on the ratio of PHAP to PBFDO, it is named 40PHAP-20PBFDO.

[0075] (3) Add 160 mg of nano-silicon powder and 1300 mg of a 3% solute binder to the mushroom box. The ratio of silicon powder to binder PHAP-PBFDO is 8:2, and the total mass fraction of silicon powder and binder in the slurry is 13%. The mixture is ball-milled at 350 rpm in a planetary ball mill for 1 hour to fully mix the mixture and obtain a uniformly dispersed negative electrode slurry. The slurry is coated on a copper foil current collector using an automatic coating agent with a coating thickness of 90 μm. After coating, the slurry is placed in a vacuum oven to completely evaporate the solvent and cut into electrode pieces with a diameter of 12 mm. Finally, a silicon negative electrode composited with 40 PHAP-20 PBFDO is obtained. Its electronic conductivity is tested, and the results are as follows: Figure 7 As shown, it exhibits higher electronic conductivity.

[0076] The prepared 20PHAP-20PBFDO negative electrode is used in a sulfide all-solid-state battery. The preparation process of the battery includes the following steps:

[0077] Step 1: Transfer the cut electrode pieces to an argon-filled glove box and assemble the sulfide all-solid-state battery half-cell. First, weigh 100 mg of the sulfide solid electrolyte Li6PS5Cl (LPSC) and grind it twice in a mortar. Spread the ground powder in a mold, then press the solid electrolyte at 175 MPa for 1 minute. Then, place the prepared negative electrode piece in the mold, contacting the active material with the solid electrolyte. Press at 175 MPa for 1 minute, then increase the pressure to 350 MPa and hold for 5 minutes. After the pressure is maintained, unload the battery. Use a punch with a diameter of 12mm to cut a piece of ultra-thin lithium with a thickness of 150μm, an indium with a thickness of 100μm, and an ultra-thin stainless steel sheet with a thickness of 100μm. Place the indium sheet, lithium sheet, and ultra-thin stainless steel sheet in the solid electrolyte sheet one by one. The ultra-thin stainless steel sheet serves as the current collector. After assembling the mold, pressurize it to 175MPa and maintain the pressure for 1min. Lithium and indium form lithium-indium alloy under pressure. Then slowly release the pressure to 75MPa and tighten the screws. The sulfide all-solid-state half-cell is assembled.

[0078] Step 2: Test the electrochemical performance of the half-cell assembled in step 1. The voltage window is set to -0.61V to 0.88V (0.01~1.5V, vs. Li + / Li), the theoretical specific capacity is set to 3500mAh·g -1 , pre-cycled 3 times at 0.1C rate, and long cycle test was performed at 1C rate. Before the start of the cycle and after 50 cycles, the battery was disassembled and the surface morphology of the negative electrode was observed using a scanning electron microscope (SEM) to study the changes in the negative electrode at different cycle stages. The results are shown in Figure 2. Figure 3 As shown in the figure, the long cycle test results are as follows Figure 3 As shown, the morphology of the electrode before and after the cycle is as follows Figure 6 As shown in the figure, the specific performance is: after the pre-cycle, the discharge capacity is 2460.03mAh·g under the 1C rate test condition. -1 , the capacity after 500 cycles is 2049.46 mAh g -1 The retention rate is 83.29%, the cycle stability performance is good, and the surface morphology of the electrode remains structurally stable and intact after the cycle.

[0079] Example 2

[0080] The preparation method, reaction conditions, purification method, and conductive polymer compounding method of the triblock copolymer PHAP of 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were the same as those in Example 1, except that the mass ratio of PHAP, tea polyphenols, and PBFDO was 9:1:9. The product was named 20PHAP-20PBFDO according to the ratio of PHAP to PBFDO.

[0081] The prepared 20PHAP-20PBFDO adhesive was applied to the silicon negative electrode according to Example 1 and the sulfide all-solid-state battery was assembled and tested. The results are as follows: Figure 3 As shown in the figure, the specific performance is: after the pre-cycle, the discharge capacity is 2318.68mAh·g under the 1C rate test condition. -1 The capacity retention rate after 500 cycles is 72.82%, and the cycle stability performance is good.

[0082] Example 3

[0083] The preparation method, reaction conditions, purification method, and conductive polymer compounding method of the triblock copolymer PHAP of 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were the same as those in Example 1, except that the mass ratio of PHAP, tea polyphenols, and PBFDO was 27:1:9. The product was named 60PHAP-20PBFDO according to the ratio of PHAP to PBFDO.

[0084] The prepared 60PHAP-20PBFDO adhesive was applied to the silicon negative electrode according to Example 1 and the sulfide all-solid-state battery was assembled for testing. The long cycle test results are as follows: Figure 3 As shown in the figure, the specific performance is: after the pre-cycle, the discharge capacity is 2350.58mAh·g under the 1C rate test condition. -1 The capacity retention rate after 500 cycles is 81.79%, and the cycle stability performance is good.

[0085] analyze Figure 3 It can be seen that the addition of conductive polymers in different proportions can improve the cycle stability of the battery.

[0086] Example 4

[0087] The preparation method, reaction conditions, purification method, and conductive polymer compounding method of the triblock copolymer PHAP of 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were the same as those in Example 1, except that the mass ratio of PHAP, tea polyphenols, and PBFDO was 9:1:18. The product was named 20PHAP-40PBFDO according to the ratio of PHAP to PBFDO.

[0088] The prepared 20PHAP-40PBFDO binder and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0089] Example 5

[0090] The preparation method and raw material ratio of the gradient hydrogen bond stress dissipation adhesive PHAP-PBFDO are the same as those in Example 1.

[0091] The prepared PHAP-PBFDO adhesive was applied to the silicon negative electrode according to the above method and assembled into a sulfide all-solid-state battery for testing. The test conditions were 3 pre-cycles at a rate of 0.1C and a long cycle test at a rate of 2C. The test results are as follows: Figure 4 As shown in the figure, the specific performance is: after the pre-cycle, the discharge capacity is 2236.17mAh·g under the 2C rate test condition. -1 After 1000 cycles, there is still 1546.51 mAh g -1 The capacity retention rate is 69.14%, and it has excellent cycle stability at high rates.

[0092] Example 6

[0093] The preparation method and raw material ratio of the gradient hydrogen bond stress dissipation adhesive PHAP-PBFDO are the same as those in Example 1.

[0094] The prepared PHAP-PBFDO adhesive was applied to the silicon anode according to the above method with a coating thickness of 120 μm. After the solvent was completely evaporated, the active mass was 1 mg cm -2 , and assembled the sulfide all-solid-state battery for testing. The test conditions were 3 pre-cycles at a rate of 0.1C and a long cycle test at a rate of 0.5C. The test results are as follows Figure 5 As shown in the figure, the specific performance is: after the pre-cycle, the discharge capacity is 2733.74mAh·g under the 0.5C rate test condition. -1 After 500 cycles, there is still 1826.85 mAh g -1 The capacity retention rate is 66.81%, and it still shows excellent cycle stability at high surface loading.

[0095] Example 7

[0096] 2-Hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were dissolved in a mixture of 10 mL of N,N-dimethylformamide and 10 mL of deionized water in a molar ratio of 1:3:2 and stirred thoroughly. An ammonium persulfate initiator (1% by weight of the solute) was added. The remaining reaction conditions and preparation method were the same as in Example 1 to prepare the adhesive PHAP-PBFDO-2.

[0097] The prepared binder PHAP-PBFDO-2 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0098] Example 8

[0099] 2-Hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were dissolved in a mixture of 10 mL of N,N-dimethylformamide and 10 mL of deionized water in a molar ratio of 3:1:2 and stirred thoroughly. An initiator, ammonium persulfate, was added at 1% of the solute mass. The remaining reaction conditions and preparation method were the same as in Example 1 to prepare the adhesive PHAP-PBFDO-3.

[0100] The prepared binder PHAP-PBFDO-3 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0101] Example 9

[0102] 2-Hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were dissolved in a mixture of 10 mL of N,N-dimethylformamide and 10 mL of deionized water at a molar ratio of 1:1:5 and stirred thoroughly. An ammonium persulfate initiator (1% by weight of the solute) was added. The remaining reaction conditions and preparation method were the same as in Example 1 to prepare the binder PHAP-PBFDO-4.

[0103] The prepared binder PHAP-PBFDO-4 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0104] Example 10

[0105] 2-Hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were dissolved in a mixture of 10 mL of N,N-dimethylformamide and 10 mL of deionized water in a molar ratio of 1:1:2 and stirred thoroughly. An ammonium persulfate initiator (0.5% by weight of the solute) was added. The remaining reaction conditions and preparation method were the same as in Example 1 to prepare the adhesive PHAP-PBFDO-5.

[0106] The prepared binder PHAP-PBFDO-5 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0107] Example 11

[0108] The preparation method, reaction conditions, purification method and conductive polymer compounding method of PHAP, a triblock copolymer of 2-hydroxyethyl acrylate, acrylic acid and polyethylene glycol monomethyl ether methacrylate, are the same as those in Example 1. PDADF is selected as the n-type conductive polymer as the binder PHAP-PDADF.

[0109] The prepared binder PHAP-PDADF and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0110] Example 12

[0111] The preparation method, reaction conditions, purification method, and conductive polymer compounding method of a triblock copolymer of 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate, PHAP, were the same as in Example 1. Tannic acid was used as the small molecule crosslinker, and the remaining reaction conditions were the same as in Example 1. This was used as the adhesive, PHAP-PBFDO-6.

[0112] The prepared binder PHAP-PBFDO-6 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0113] Example 13

[0114] In this example, the reaction conditions of the tea polyphenol solution, PBFDP and PHAP solution were adjusted relative to those in Example 1. The reaction temperature was 28° C. and the reaction time was 4 h to obtain the adhesive PHAP-PBFDO-7.

[0115] The prepared binder PHAP-PBFDO-7 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0116] Example 14

[0117] In this example, the reaction conditions of the tea polyphenol solution, PBFDP and PHAP solution were adjusted relative to those in Example 1. The reaction temperature was 30° C. and the reaction time was 4 h to obtain the adhesive PHAP-PBFDO-8.

[0118] The prepared binder PHAP-PBFDO-8 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0119] Example 15

[0120] In this example, similar to Example 1, 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were added in a molar ratio of 3:1:2 to form a homogeneous solution. After forming a homogeneous solution, ammonium persulfate as an initiator was added, with the mass of the initiator being 0.8% of the mass of the solute. The homogeneous solution was then frozen solid in liquid nitrogen, evacuated for 5 minutes, then flushed with argon, thawed in room temperature water, and frozen and evacuated again, repeating this process three times. The reaction flask was heated to 60°C and reacted for 5 hours. After the polymerization reaction, the product was cooled in an ice-water bath to terminate the reaction. The cooled solution was dialyzed against water for three days and freeze-dried for two days to obtain pure triblock copolymer PHAP. The remaining reaction conditions and preparation method were the same as in Example 1, and the product was used as the binder PHAP-PBFDO-9.

[0121] The prepared binder PHAP-PBFDO-9 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0122] Example 16

[0123] In this example, similar to Example 1, 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate were added in a molar ratio of 2:3:5 to form a homogeneous solution. After forming a homogeneous solution, ammonium persulfate as an initiator was added, with the mass of the initiator being 1% of the mass of the solute. The homogeneous solution was then frozen solid in liquid nitrogen, evacuated for 5 minutes, then purged with argon, thawed in room temperature water, and frozen again for evacuation. This process was repeated three times. The reaction flask was heated to 75°C and reacted for 3 hours. After the polymerization reaction, the product was cooled in an ice-water bath to terminate the reaction. The cooled solution was dialyzed against water for three days and freeze-dried for two days to obtain pure triblock copolymer PHAP. The remaining reaction conditions and preparation method were the same as in Example 1, and the product was used as the binder PHAP-PBFDO-10.

[0124] The prepared binder PHAP-PBFDO-10 and the corresponding silicon negative electrode were used in a sulfide all-solid-state battery, and all the steps were the same as in Example 1.

[0125] Comparative Example 1

[0126] No binder was used and a pure silicon negative electrode was used as a comparative example.

[0127] 200 mg of silicon nanoparticles were weighed and added to a mushroom box equipped with quartz ball milling beads. Deionized water was added to adjust the slurry solid content to 20%. The mushroom box was placed in a planetary ball mill and ball milled at 350 rpm for 60 minutes to obtain a uniformly dispersed negative electrode slurry. The final electrode was coated on a copper foil current collector and vacuum dried. The coating thickness was 100 μm, and the loading was controlled at 0.7 mg cm. -2 The pure silicon electrodes were transferred into an argon-filled vacuum glove box to assemble the mold half-cell for testing.

[0128] The prepared Pure-Si negative electrode was used in a sulfide all-solid-state battery. All the steps were the same as in Example 1. The electronic conductivity of the electrode was as follows: Figure 7 shown.

[0129] Comparative Example 2

[0130] A commercial adhesive polyacrylic acid (PAA) was used as a comparative example.

[0131] PAA was formed into a film and its glass transition temperature was tested by differential scanning calorimetry. Figure 8 As shown, it can be seen that the glass transition temperature of PAA is higher.

[0132] 160 mg of silicon nanoparticles and 40 mg of polyacrylic acid (PAA) binder were weighed in a ratio of 8:2, and added to a mushroom box equipped with quartz ball milling beads. Deionized water was added to adjust the slurry solids content to 20%. The mushroom box was placed in a planetary ball mill and ball milled at 350 rpm for 60 minutes to obtain a uniformly dispersed negative electrode slurry. The final electrode was coated on a copper foil current collector and dried under vacuum. The coating thickness was 100 μm, and the loading was controlled at 0.7 mg cm. -2 The composite electrodes were transferred to a vacuum glove box filled with argon to assemble the mold half-cell for testing.

[0133] The prepared Si-PAA negative electrode was used in a sulfide all-solid-state battery. All the steps were the same as in Example 1. The electronic conductivity of the electrode was as follows: Figure 7 As shown in Figure 3, the electronic conductivity of the Si-PAA anode is lower than that of the pure Si anode, indicating that the introduction of the electronic insulating binder PAA hinders the electronic conduction process.

[0134] The present invention provides a gradient hydrogen bond stress dissipation adhesive capable of improving the cycle performance of sulfide all-solid-state batteries, as well as its preparation method and application. A series of triblock copolymers of 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate in different proportions were prepared by free radical polymerization. The large number of phenolic hydroxyl groups of small molecule tea polyphenols form hydrogen bonds with different bond energies with the hydroxyl and carboxyl groups of PHAP and n-type conductive polymers. When the silicon negative electrode expands in volume during the cycle, the hydrogen bonds of the adhesive are broken in sequence from low to high binding energy, so that the stress concentration generated by the silicon negative electrode during the cycle is dissipated step by step, thereby forming an energy consumption buffer layer, improving the stability of the silicon negative electrode, reducing the generation of small cracks, and avoiding the appearance of large vertical network cracks. At the same time, the large number of ether bonds distributed in the PEGMA block provide an efficient transmission path for lithium ions, and the n-type conductive polymer significantly improves the electronic conductivity of the adhesive, constructing a continuous ion and electron efficient transmission network inside the silicon negative electrode.

[0135] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An adhesive, characterized in that The adhesive is prepared by reacting a small molecule cross-linking agent, an n-type conductive polymer, and a triblock copolymer PHAP. The small molecule cross-linking agent has a phenolic hydroxyl group, and the triblock copolymer PHAP has the following structural formula: Among them, the range of x is 30-90, the range of y is 30-90, the range of z is 60-150, and n is 10-30.

2. An adhesive according to claim 1, characterized in that The small molecule cross-linking agent is any one of tea polyphenols or tannic acid.

3. The adhesive according to claim 1, characterized in that The n-type conductive polymer is any one of poly(benzofurandione) or poly(benzofurandione).

4. A method for preparing the adhesive according to claim 1, characterized in that: The following steps are involved: A small molecule cross-linking agent is dissolved in water to obtain a cross-linking agent solution; the cross-linking agent solution, an n-type conductive polymer solution and a PHAP solution are mixed, and the mixture is uniformly reacted to obtain an adhesive.

5. The method for preparing the adhesive according to claim 4, wherein: The mass ratio of the PHAP: small molecule cross-linking agent and n-type conductive polymer is (9-27):1:(9-18).

6. The method for preparing the adhesive according to claim 4, wherein: The reaction temperature is 25-30°C, and the reaction time is 3-5 hours.

7. The method for preparing the adhesive according to claim 4, wherein: The preparation method of the PHAP is as follows: Step 1, dissolving 2-hydroxyethyl acrylate, acrylic acid, and polyethylene glycol monomethyl ether methacrylate in a mixed solution of N,N-dimethylformamide and water, and stirring uniformly to obtain a homogeneous solution; Step 2: adding an initiator to the homogeneous solution, freezing and thawing the solution several times, then heating the solution to cause a polymerization reaction, placing the entire reaction system in an ice-water bath to terminate the reaction and obtain a reaction product; Step 3: After dialyzing and freezing the reaction product, a triblock copolymer PHAP is obtained.

8. The method for preparing the adhesive according to claim 7, characterized in that: In step 1, the molar ratio of 2-hydroxyethyl acrylate, acrylic acid and polyethylene glycol monomethyl ether methacrylate is (1-3): (1-3): (2-5); In step 2, the reaction temperature is 60-75° C. and the reaction time is 3-5 hours.

9. A silicon negative electrode, characterized in that: The silicon negative electrode comprises a coating slurry and a current collector, wherein the coating slurry is composed of silicon particles and the binder according to claim 1 .

10. An all-solid-state battery, characterized in that: The all-solid-state battery comprises a positive electrode, the silicon negative electrode according to claim 9 and a separator.

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