Self-healing conductive polymer binder, method for preparing the same and lithium ion battery

Abstract

This invention provides a method for preparing a self-healing conductive polymer adhesive, comprising, by weight, a pre-polymerization step, a re-polymerization step, an emulsification step, and a post-polymerization step. This invention also provides a self-healing conductive polymer adhesive and a lithium-ion battery including the self-healing conductive polymer adhesive. The self-healing conductive polymer adhesive of this invention exhibits excellent adhesion and solubility, effectively buffering the structural tension generated by the expansion and contraction of the electrode structure during charging and discharging. It also possesses excellent hydrophilicity, good electrolyte wettability, high ionic conductivity, and good dispersion, and is not prone to demulsification under prolonged stirring. Compared with traditional SBR adhesives, it has better ionic conductivity. Furthermore, the self-healing conductive polymer adhesive of this invention also possesses self-healing properties, capable of self-repairing after structural damage caused by electrode expansion, ensuring battery stability and extending service life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a self-healing conductive polymer adhesive and its preparation method, and also to a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, as a highly efficient, reliable, and environmentally friendly energy storage technology, have been widely used in portable electronic devices, electric vehicles, and energy storage systems, driving the development of renewable energy and electric transportation. One of the core components of a lithium-ion battery is the negative electrode material, which is formed by coating a paste-like adhesive of active materials, binders, and additives onto both sides of copper foil and then rolling it. The conductive binder for the negative electrode plays a crucial role in lithium-ion batteries; it is responsible for fixing the active materials in the negative electrode material onto the electrode sheet, providing a uniform electron conduction path, suppressing volume expansion caused by battery charging and discharging, enhancing the mechanical stability of the electrode, and protecting the negative electrode material.

[0003] Currently, styrene-butadiene rubber (SBR) is mainly used as a binder in the negative electrode slurry of lithium-ion batteries. While SBR is a mature industrial binder, it suffers from problems such as low ionic conductivity, swelling, easy demulsification under prolonged stirring, and poorer dispersion compared to CMC (conductively coupled polymer). Low ionic conductivity leads to increased electrode resistance and reduced capacity, while swelling damages the electrode structure and reduces overall performance. Furthermore, it lacks self-healing properties, resulting in functional loss once the molecular structure is damaged. To address these issues, researchers are exploring novel conductive polymer negative electrode binders to reduce battery internal resistance and improve overall performance.

[0004] In this research, one approach involves adding fluorides to the adhesive polymer to improve its performance. However, the addition of fluorides cannot effectively suppress the volume expansion of silicon-based materials, and as a fluorinated oil-based adhesive, it is not environmentally friendly, consumes a lot of energy, is expensive, and is detrimental to the health of operators. Another approach involves using polymeric polysaccharides to make adhesives, which have better environmental performance and are relatively inexpensive. However, their performance does not meet the current standards for commercial lithium-ion battery applications, and the polysaccharide polymers used, such as chitosan, have poor dispersibility in aqueous solvents, introducing new problems to the electrode fabrication process. Summary of the Invention

[0005] In view of this, the present invention provides a self-healing conductive polymer adhesive and its preparation method. The present invention also provides a lithium-ion battery to solve the problems of existing lithium-ion battery adhesives, such as being environmentally unfriendly, having high energy consumption, high price, poor water solubility, and being unable to effectively suppress the volume expansion of silicon-based materials.

[0006] In a first aspect, the present invention provides a method for preparing a self-healing conductive polymer adhesive, comprising the following steps by weight:

[0007] Prepolymerization: A first reaction vessel is provided and 130-150 parts of polyether polyol or polyester polyol are added to it. The first reaction vessel is heated to 50-70°C, and then 40-60 parts of diisocyanate and 0.2-1 parts of organotin catalyst or organic amine catalyst are added. The first reaction vessel is heated to 70-80°C and maintained for 0.5-3 h. Then 1-3 parts of hydrophilic chain extender are added to the first reaction vessel. The temperature of the first reaction vessel is adjusted to 75-85°C, and the reaction is stirred for 6-8 h. After the reaction is completed, the prepolymer is obtained.

[0008] Repolymerization: Adjust the temperature of the first reaction vessel to 40-50℃ and add 30-50 parts of acrylate to the first reaction vessel. Then raise the temperature of the first reaction vessel to 70-80℃ and maintain it for 1-5 hours. After the reaction is completed, cool the first reaction vessel to room temperature to obtain the repolymer.

[0009] Emulsification: The repolymer is transferred to an emulsification container and 250-300 parts of distilled water and 1-5 parts of TEA are added to the emulsification container to obtain an emulsion system. The emulsion system is stirred for 0.5-3 h. Then, 100-150 parts of styrene, 50-100 parts of crosslinking agent and 1-5 parts of emulsifier are added to the emulsion system. The emulsion system is stirred for another 0.5-3 h to obtain an emulsion system.

[0010] Post-polymerization: The emulsion system is transferred to a second reaction vessel and heated to 70-90°C. While stirring the emulsion system, 1-3 parts of polymerization initiator are added. The reaction is continued for 4-8 hours. After the reaction is completed, the second reaction vessel is cooled to room temperature to obtain a self-healing conductive polymer adhesive.

[0011] The preparation method of the self-healing conductive polymer adhesive of this invention includes a pre-polymerization step, a repolymerization step, an emulsification step, and a post-polymerization step. In the pre-polymerization step, under the catalysis of an organotin catalyst or an organoamine catalyst, a polyether polyol or a polyester polyol undergoes a polymerization reaction with a diisocyanate to generate a polymer with NCO ends. This NCO-end polymer then reacts with a hydrophilic chain extender to obtain a prepolymer with high molecular weight and high crosslinking degree. The hydrophilic chain extender can react with functional groups on the linear polymer chain, thereby extending the molecular chain and increasing the molecular weight, which is used to improve the mechanical and process properties of the self-healing conductive polymer for lithium-ion batteries. In the repolymerization step, due to the excellent electrolyte wettability of acrylates, modifying the prepolymer with acrylates can significantly improve the electrolyte wettability of the self-healing conductive polymer adhesive, thereby improving the rate performance of the battery. In the emulsification step, the addition of an emulsifier ensures that the newly added substances are dispersed evenly, especially water-insoluble reactive monomers such as styrene. After adding an emulsifier, water-insoluble reactants such as styrene can form micelles in the solution, uniformly dispersed in the aqueous reaction system, and participate in subsequent reactions. In the post-polymerization step, the styrene and crosslinking agent added in the previous step are emulsified and mixed evenly. Further polymerization occurs in the aqueous medium under the initiation of an initiator. Adding a crosslinking agent promotes crosslinking between the crosslinking agent and the polymer, and this crosslinking reaction is reversible. This reversible reaction is beneficial for self-healing conductive polymer adhesives to maintain their adhesive properties under different pressure conditions through reversible crosslinking, thus achieving the self-healing function of the adhesive. Triethylamine is used in the preparation of polyurethane to counteract acidic ions in the polymer backbone. The post-polymerization step allows for the post-polymerization of the previously formed polyurethane prepolymer, further increasing the molecular weight of the polymer chain. Simultaneously, multiple nucleation initiations produce a high-solids-content, low-viscosity emulsion with a multi-dimensional particle size distribution.

[0012] Preferably, in the pre-polymerization step, the polyether polyol is polytetrahydrofuran ether diol, polypropylene oxide diol, or tetrahydrofuran-propylene oxide copolydiol; the polyester polyol is polyethylene terephthalate-1,4-cyclohexanediol, polycaprolactone polyol, or polycarbonate diol; and the diisocyanate is isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, or methylcyclohexane diisocyanate. Suitable polyether polyols or polyester polyols and diisocyanates can further improve the mechanical and processing properties of the self-healing conductive polymer adhesive.

[0013] Preferably, in the pre-polymerization step, the organotin catalyst is dibutyltin dilaurate, tributyltin alcohol, or trimylated phenyltin; the organoamine catalyst is triethylamine, pyridine, or pyrrolidine; and the hydrophilic chain extender is dimethylolpropionic acid (DMPA) or 4,4-diaminodiphenyl sulfide. A suitable catalyst can significantly improve the reaction rate and the uniformity of polymer molecular weight, while reducing reaction time.

[0014] Preferably, in the prepolymerization step, 140 parts of polytetrahydrofuran ether diol are added to the first reaction vessel, the first reaction vessel is heated to 60°C, and then 50 parts of isoflavone diisocyanate and 0.5 parts of dibutyltin dilaurate are added to it, and then the first reaction vessel is heated to 75°C and maintained for 1 h.

[0015] Two parts of dimethylolpropionic acid were then added to the first reaction vessel, and the temperature of the first reaction vessel was adjusted to 80°C. The mixture was stirred at 400–800 RPM for 6–8 hours. After the reaction was completed, the prepolymer was obtained. Appropriate amounts of reactants and reaction steps can significantly improve the reaction rate and the uniformity of polymer molecular weight, while reducing reaction time.

[0016] Preferably, in the repolymerization step, the acrylate is methyl acrylate, ethyl acrylate, methyl 2-methacrylate, ethyl 2-methacrylate, or butyl acrylate. A suitable acrylate can fully participate in the polymer modification process and effectively improve the hydrophilicity and wetting properties of the self-healing conductive polymer adhesive in the electrolyte.

[0017] Preferably, in the repolymerization step, the temperature of the first reaction vessel is adjusted to 45°C and 40 parts of methyl methacrylate are added to the first reaction vessel. The temperature of the first reaction vessel is then raised to 75°C and maintained for 3 hours. After the reaction is completed, the first reaction vessel is cooled to room temperature to obtain the repolymer. Suitable polymerization reaction process conditions and dosages can improve the reaction progress and reduce the yield of by-products.

[0018] Preferably, in the emulsification step, the crosslinking agent is boric acid, and the emulsifier is sodium dodecyl sulfate or dodecylphenol polyoxyethylene ether;

[0019] The stirring speed is 600–1500 RPM. The borate ester bonds ensure good mechanical strength of the sample, and they also enable reversible hydrolysis, a dynamic process that promotes self-healing. A suitable emulsifier allows the reactants to form micelles in the solution, uniformly dispersing them within the aqueous reaction system to participate in the reaction.

[0020] Preferably, in the post-polymerization step, the polymerization initiator is a mixed solution with a mass fraction of 0.3% to 1.5%, and the solute of the polymerization initiator is sodium persulfate, potassium persulfate, or ammonium persulfate;

[0021] The stirring speed is 300–800 RPM. Selecting a polymerization initiator in a mixed solution state helps the polymerization initiator to fully contact the reactants, fully initiate polymerization, and ensure that the polymerization reaction proceeds completely and the product has a uniform molecular weight and structure.

[0022] In a second aspect, the present invention also provides a self-healing conductive polymer adhesive, wherein the self-healing conductive polymer adhesive is prepared by the preparation method of the self-healing conductive polymer adhesive described in any one of the first aspects.

[0023] This invention's self-healing conductive polymer adhesive exhibits excellent adhesion and solubility, effectively buffering the structural tension generated by electrode expansion and contraction during charging and discharging. It also possesses excellent hydrophilicity, good electrolyte wettability, high ionic conductivity, and good dispersion, and is not prone to demulsification under prolonged stirring. Compared to traditional SBR adhesives, it demonstrates superior ionic conductivity. Furthermore, this self-healing conductive polymer adhesive possesses self-healing properties, enabling it to self-repair after structural damage caused by electrode expansion, ensuring battery stability and extending its lifespan.

[0024] Thirdly, the present invention also provides a lithium-ion battery comprising the self-healing conductive polymer adhesive described in the second aspect.

[0025] The lithium-ion battery of this invention uses a self-healing conductive polymer adhesive, and the lithium-ion battery has excellent cycle stability, capacity retention and rate performance.

[0026] The advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the embodiments thereof. Attached Figure Description

[0027] To more clearly illustrate the content of this invention, it will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Figure 1 The graph shows the results of a comparative test of the cycling performance at room temperature.

[0029] Figure 2 This is a graph showing the test results of a single-sided electrode through a steel needle.

[0030] Figure 3 The graph shows the results of the electrode internal resistance test.

[0031] Figure 4 The graph shows the results of the DC internal resistance test. Detailed Implementation

[0032] The following describes preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0033] The following detailed embodiments illustrate the self-healing conductive polymer adhesive of this application and its preparation method, as well as the lithium-ion battery assembled using the self-healing conductive polymer adhesive of this application as the negative electrode adhesive. Example 1

[0034] A method for preparing a self-healing conductive polymer adhesive, comprising the following steps by weight:

[0035] Prepolymerization step: A stainless steel reactor was provided, and 135 g of polypropylene glycol was added to it. The reactor was then heated to 70°C. After heating, 45 g of methylcyclohexane diisocyanate and 0.2 g of triethylamine were added to the reactor, and the temperature was raised to 70°C and maintained for 3 h. After the reaction was completed, 1 g of dimethylolpropionic acid was added to the reactor, and the temperature was adjusted to 75°C again. The mixture in the reactor was stirred at 400 RPM for 7 h. After the reaction was completed, the prepolymer was obtained.

[0036] Repolymerization step: Adjust the temperature of the stainless steel reactor to 40℃ and add 40 parts of methyl acrylate to the stainless steel reactor. Then raise the temperature of the stainless steel reactor to 75℃ and maintain it for 1 h. After the reaction is completed, lower the stainless steel reactor to room temperature to obtain the repolymer.

[0037] Emulsification step: The aforementioned repolymer was transferred to an emulsification container and 250 g of distilled water and 2 g of neutralizing agent TEA (triethylamine) were added to the emulsification container to obtain an emulsion system. The emulsification system was stirred at 1500 RPM for 0.5 h. Then, 100 g of styrene, 50 g of boric acid and 1 g of dodecylphenol polyoxyethylene ether were added to the emulsification system, and the emulsification system was stirred at 1500 RPM for another 0.5 h to obtain an emulsion system.

[0038] Post-polymerization step: The aforementioned emulsion system was transferred to a stainless steel reactor and heated to 70°C. While stirring the emulsion system, 2 g of potassium persulfate solution with a mass fraction of 0.3% was slowly added dropwise. The emulsion system was stirred at a speed of 300 RPM for 6 h while adding dropwise. After the stirring reaction was completed, the stainless steel reactor was cooled to room temperature to obtain the self-healing conductive polymer adhesive. Example 2

[0039] A method for preparing a self-healing conductive polymer adhesive, comprising the following steps by weight:

[0040] Prepolymerization step: A stainless steel reactor was provided, and 130 g of polycaprolactone polyol was added to it. The reactor was then heated to 60°C. After heating, 40 g of diphenylmethane diisocyanate and 0.3 g of tributyltin alcohol were added to the reactor, and the temperature was raised to 70°C and maintained for 2 h. After the reaction was completed, 2 g of the hydrophilic chain extender 4,4-diaminodiphenyl sulfide was added to the reactor, and the temperature was adjusted to 80°C. The mixture in the reactor was stirred at 400 RPM for 8 h. After the reaction was completed, the prepolymer was obtained.

[0041] Repolymerization step: Adjust the temperature of the stainless steel reactor to 40℃ and add 30 parts of ethyl acrylate to the stainless steel reactor. Then raise the temperature of the stainless steel reactor to 70℃ and maintain it for 2 hours. After the reaction is completed, lower the stainless steel reactor to room temperature to obtain the repolymer.

[0042] Emulsification step: The aforementioned repolymer was transferred to an emulsification container and 260 g of distilled water and 1 g of neutralizing agent TEA (triethylamine) were added to the emulsification container to obtain an emulsion system. The emulsification system was stirred at 600 RPM for 1 h. Then, 130 g of styrene, 60 g of boric acid and 2 g of sodium dodecyl sulfate were added to the emulsification system, and the emulsification system was stirred at 600 RPM for another 1 h to obtain an emulsion system.

[0043] Post-polymerization step: The aforementioned emulsion system was transferred to a stainless steel reactor and heated to 75°C. While stirring the emulsion system, 1 g of 1.2% ammonium persulfate solution was slowly added dropwise. The emulsion system was stirred at 400 RPM for 8 h while adding the solution. After the stirring reaction was completed, the stainless steel reactor was cooled to room temperature to obtain the self-healing conductive polymer adhesive. Example 3

[0044] A method for preparing a self-healing conductive polymer adhesive, comprising the following steps by weight:

[0045] Prepolymerization step: A stainless steel reactor was provided, and 140 g of polytetrahydrofuran ether diol was added to it. The reactor was then heated to 60°C. After heating, 50 g of isoflavone diisocyanate and 0.5 g of dibutyltin dilaurate were added to the reactor, and the temperature was raised to 75°C and maintained for 1 h. After the reaction was completed, 2 g of the hydrophilic chain extender dimethylolpropionic acid was added to the reactor, and the temperature was adjusted to 80°C again. The mixture in the reactor was stirred at 600 RPM for 7 h. After the reaction was completed, the prepolymer was obtained.

[0046] Repolymerization step: Adjust the temperature of the stainless steel reactor to 45°C and add 40 parts of methyl 2-methacrylate to the stainless steel reactor. Then raise the temperature of the stainless steel reactor to 75°C and maintain it for 3 hours. After the reaction is completed, lower the stainless steel reactor to room temperature to obtain the repolymer.

[0047] Emulsification step: The aforementioned repolymer was transferred to an emulsification container and 280 g of distilled water and 3 g of neutralizing agent TEA (triethylamine) were added to the emulsification container to obtain an emulsion system. The emulsification system was stirred at 1000 RPM for 2 h. Then, 120 g of styrene, 80 g of boric acid and 3 g of sodium dodecyl sulfate were added to the emulsification system, and the emulsification system was stirred at 1000 RPM for another 2 h to obtain an emulsion system.

[0048] Post-polymerization step: The aforementioned emulsion system was transferred to a stainless steel reactor and heated to 80°C. While stirring the emulsion system, 2 g of sodium persulfate solution with a mass fraction of 1% was slowly added dropwise. The emulsion system was stirred at a speed of 500 RPM for 6 h while adding dropwise. After the stirring reaction was completed, the stainless steel reactor was cooled to room temperature to obtain the self-healing conductive polymer adhesive. Example 4

[0049] A method for preparing a self-healing conductive polymer adhesive, comprising the following steps by weight:

[0050] Prepolymerization step: A stainless steel reactor was provided, and 150 g of polyethylene terephthalate-1,4-cyclohexanediethanol ester was added. The reactor was then heated to 70°C. After heating, 60 g of hexamethylene diisocyanate and 0.8 g of pyrrolidine were added to the reactor, and the temperature was raised to 80°C and maintained for 1 h. After the reaction, 3 g of the hydrophilic chain extender 4,4-diaminodiphenyl sulfide was added to the reactor, and the temperature was adjusted to 85°C. The mixture in the reactor was stirred at 600 RPM for 8 h. After the reaction was completed, the prepolymer was obtained.

[0051] Repolymerization step: Adjust the temperature of the stainless steel reactor to 50°C and add 50 parts of ethyl 2-methacrylate to the stainless steel reactor. Then raise the temperature of the stainless steel reactor to 80°C and maintain it for 5 hours. After the reaction is completed, lower the stainless steel reactor to room temperature to obtain the repolymer.

[0052] Emulsification step: The aforementioned repolymer was transferred to an emulsification container and 290 g of distilled water and 5 g of neutralizing agent TEA (triethylamine) were added to the emulsification container to obtain an emulsion system. The emulsification system was stirred at 800 RPM for 3 h. Then, 150 g of styrene, 100 g of boric acid and 5 g of sodium dodecyl sulfate were added to the emulsification system, and the emulsification system was stirred at 800 RPM for another 3 h to obtain an emulsion system.

[0053] Post-polymerization step: The aforementioned emulsion system was transferred to a stainless steel reactor and heated to 85°C. While stirring the emulsion system, 3 g of potassium persulfate solution with a mass fraction of 0.8% was slowly added dropwise. The emulsion system was stirred at 800 RPM for 4 h while adding dropwise. After the stirring reaction was completed, the stainless steel reactor was cooled to room temperature to obtain the self-healing conductive polymer adhesive. Example 5

[0054] A method for preparing a self-healing conductive polymer adhesive, comprising the following steps by weight:

[0055] Prepolymerization step: A stainless steel reactor was provided, and 145 g of tetrahydrofuran-propylene oxide copolydiol was added to it. The reactor was then heated to 60°C. After heating, 55 g of toluene diisocyanate and 1 g of trimylated tin were added to the reactor, and the temperature was raised to 80°C and maintained for 0.5 h. After the reaction was completed, 3 g of the hydrophilic chain extender dimethylolpropionic acid was added to the reactor, and the temperature was adjusted to 85°C again. The mixture in the reactor was stirred at 800 RPM for 6 h. After the reaction was completed, the prepolymer was obtained.

[0056] Repolymerization step: Adjust the temperature of the stainless steel reactor to 45℃ and add 40 parts of butyl acrylate to the stainless steel reactor. Then raise the temperature of the stainless steel reactor to 80℃ and maintain it for 4 hours. After the reaction is completed, lower the stainless steel reactor to room temperature to obtain the repolymer.

[0057] Emulsification step: The aforementioned repolymer was transferred to an emulsification container and 300 g of distilled water and 4 g of neutralizing agent TEA (triethylamine) were added to the emulsification container to obtain an emulsion system. The emulsification system was stirred at 1200 RPM for 2 h. Then, 120 g of styrene, 90 g of boric acid and 4 g of dodecylphenol polyoxyethylene ether were added to the emulsification system, and the emulsification system was stirred at 1200 RPM for another 2 h to obtain an emulsion system.

[0058] Post-polymerization step: The aforementioned emulsion system was transferred to a stainless steel reactor and heated to 90°C. While stirring the emulsion system, 2 g of sodium persulfate solution with a mass fraction of 1.5% was slowly added dropwise. The emulsion system was stirred at a speed of 600 RPM for 5 h while adding dropwise. After the stirring reaction was completed, the stainless steel reactor was cooled to room temperature to obtain the self-healing conductive polymer adhesive.

[0059] Example 1: Physical property testing of self-healing conductive polymer adhesive

[0060] The self-healing conductive polymer adhesives prepared in Examples 1-5 were used as test samples, and the commercially available SBR adhesive TRD104A produced by Japan Synthetic Rubber Co., Ltd. was used as a control sample. The test samples and control samples were subjected to physical tests simultaneously. The test indicators included the Tg, viscosity, pH and solid content of the adhesives. The test results are shown in Table 1.

[0061] Table 1 Physical Test Results

[0062] TRD104A Example 1 Example 2 Example 3 Example 4 Example 5 Tg / ℃ 0.0 0.0 -5.8 -4.3 -3.8 -1.4 Viscosity / mPa·s 100 1512 1531 1545 1577 1603 pH 7.0 8.8 9.2 9.1 8.9 9.1 Solid content 45% 40% 40% 40% 40% 40%

[0063] As shown in Table 1, the physical test results indicate that, compared to the TRD104A type SBR adhesive, the self-healing conductive polymer adhesives prepared in Examples 1-5 exhibit higher viscosity and stronger adhesion with similar or even lower solid content. These results demonstrate that the self-healing conductive polymer adhesive prepared in this application possesses superior adhesion performance.

[0064] Example 2: Comparative Test of Cyclic Performance at Room Temperature

[0065] The self-healing conductive polymer adhesive prepared in Example 3 was used as the test sample, and the commercially available SBR adhesive TRD104A manufactured by Japan Synthetic Rubber Co., Ltd. was used as the control sample. The test sample and the control sample were simultaneously subjected to a room temperature cycling performance comparison test. Test equipment: Xinwei Battery testing cabinet, internal resistance tester, multimeter, digital caliper. Test method: At 25±2℃, the battery was charged at a charging current of 0.5 C to 4.2 V with a cutoff current of 0.01 C, rested for 10 min, and then discharged at 1 C to 2.75 V, rested for 10 min. This process was repeated 500 times. Test requirements: After 500 cycles of 1 C / 1 C, the capacity retention rate should be ≥80%. Test results are attached. Figure 1 .

[0066] like Figure 1As shown, during the first 200 cycles, the capacity retention rates of the test sample and the control sample were essentially the same. However, between 200 and 300 cycles, the capacity retention rate of the test sample began to differ significantly from that of the control sample, with the test sample exhibiting a better capacity retention rate. This indicates that as the number of cycles increases, the internal electrodes of the battery begin to gradually deteriorate. The test sample, due to its self-healing properties, mitigates this damage, thus achieving better capacity retention than the control sample over longer cycles. By 500 cycles, the capacity retention rate of the test sample was 1-2% higher than that of the control sample. Therefore, the test sample's cycle life is superior to the control sample, demonstrating the effectiveness of its self-healing properties and its contribution to extending the lifespan of the lithium battery.

[0067] Example 3: Single-sided electrode test with steel needle

[0068] The self-healing conductive polymer adhesive prepared in Example 3 was used as the test sample, and the commercially available SBR adhesive TRD104A produced by Japan Synthetic Rubber Co., Ltd. was used as the control sample. The test sample and the control sample were tested simultaneously with the single-sided electrode through the steel needle.

[0069] Test methods: (1) Prepare several electrodes according to the electrode preparation method. Coating to roller pressing: Observe the sedimentation and stratification of the slurry, abnormal gelation, and abnormalities such as shrinkage cavities, bubbles, and decarburization in the appearance of the electrode. Calculate the electrode yield. (2) Needle winding: Take the cold-pressed electrode (the compaction density is selected according to the actual application. The laboratory recommends a compaction density of 1.65 g / cm). 3 Starting with the largest winding needle (5mm), wrap the electrode around the winding needle in sequence (diameter: 5 mm, 4 mm, 3 mm, 2 mm), aligning the wrapped portion firmly. (3) Aim the objective lens at the bent tip, magnify 100x, and observe for cracks. Observe the detachment after unfolding. Test results are attached. Figure 2 .

[0070] like Figure 2 As shown, there was no significant difference between the test sample and the control sample when the steel needle diameter was 5 mm and 4 mm. When the steel needle diameter reached 3 mm, the control sample electrode began to partially detach, while only a small portion of the test sample electrode detached. When the steel needle diameter reached 2 mm, most of the control sample electrode had detached, while only a small portion of the test sample electrode still detached. Therefore, the electrode prepared in Example 3 has better adhesion than the control sample.

[0071] Example 4: Electrode internal resistance test and DC internal resistance test

[0072] According to the battery manufacturing process, the self-healing conductive polymer adhesive prepared in Example 3 and the SBR adhesive TRD104A were assembled into a test battery, and the test battery was marked with JSR104A and GT901 respectively.

[0073] Electrode internal resistance test: Cut the negative electrode sample into pieces 100–200 mm wide and 220 mm long, and test the thickness of the sheet. Place the test sample on the sample holder and adjust the height handwheel to ensure good contact between the probe and its surface. Turn on the power and preheat for 1 hour. Measure the resistivity three times according to the operating procedure of the four-probe tester and take the average value. See the appendix for test results. Figure 3 .

[0074] DC internal resistance test:

[0075] The battery was adjusted to different SOC states (remaining battery capacity 100%, 80%, 60%, 40%, 20%), and its DC resistance (DCIR) was measured using a DC resistance meter at 1 C & 30 s. The result was: DCIR = (V / s) 30s -V 0s ) / I 1C The test results are attached. Figure 4 .

[0076] like Figure 3 As shown, the electrode internal resistance of SBR binder TRD104A was higher than that of the self-healing conductive polymer adhesive prepared in Example 3 in all three tests. This indicates that the self-healing conductive polymer adhesive prepared in Example 3 has better conductivity, and the corresponding battery has better electrical performance.

[0077] like Figure 4 As shown, the DC resistance of the SBR binder TRD104A under different SOC states is greater than that of the self-healing conductive polymer adhesive prepared in Example 3. This indicates that the self-healing conductive polymer adhesive prepared in Example 3 has better conductivity, and the corresponding battery has better electrical performance.

[0078] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a self-healing conductive polymer adhesive, characterized in that, by weight Includes the following steps; Prepolymerization: A first reaction vessel is provided and 130-150 parts of polyether polyol or polyester polyol are added to it. The first reaction vessel is heated to 50-70°C, and then 40-60 parts of diisocyanate and 0.2-1 parts of organotin catalyst or organic amine catalyst are added. The first reaction vessel is heated to 70-80°C and maintained for 0.5-3 hours. Then 1-3 parts of hydrophilic chain extender are added to the first reaction vessel. The temperature of the first reaction vessel is adjusted to 75-85°C, and the reaction is stirred for 6-8 hours. After the reaction is completed, the prepolymer is obtained. Repolymerization: Adjust the temperature of the first reaction vessel to 40-50℃ and add 30-50 parts of acrylate to the first reaction vessel. Then raise the temperature of the first reaction vessel to 70-80℃ and maintain it for 1-5 hours. After the reaction is completed, cool the first reaction vessel to room temperature to obtain the repolymer. Emulsification: The repolymer is transferred to an emulsification container and 250-300 parts of distilled water and 1-5 parts of TEA are added to the emulsification container to obtain an emulsion system. The emulsion system is stirred for 0.5-3 hours. Then, 100-150 parts of styrene, 50-100 parts of crosslinking agent and 1-5 parts of emulsifier are added to the emulsion system. The emulsion system is stirred for another 0.5-3 hours to obtain an emulsion system. Post-polymerization: The emulsion system is transferred to a second reaction vessel and heated to 70-90°C. While stirring the emulsion system, 1-3 parts of polymerization initiator are added. The reaction is continued for 4-8 hours. After the reaction is completed, the second reaction vessel is cooled to room temperature to obtain a self-healing conductive polymer adhesive. The acrylate is methyl acrylate, ethyl acrylate, methyl 2-methacrylate, ethyl 2-methacrylate, or butyl acrylate, and the crosslinking agent is boric acid.

2. The method for preparing the self-healing conductive polymer adhesive as described in claim 1, characterized in that, In the prepolymerization step, the polyether polyol is polytetrahydrofuran ether diol, polypropylene oxide diol, or tetrahydrofuran-propylene oxide copolyol; the polyester polyol is polyethylene terephthalate-1,4-cyclohexanediol, polycaprolactone polyol, or polycarbonate diol; and the diisocyanate is isoflavone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, or methylcyclohexane diisocyanate.

3. The method for preparing the self-healing conductive polymer adhesive as described in claim 1, characterized in that, In the prepolymerization step, the organotin catalyst is dibutyltin dilaurate, the organoamine catalyst is triethylamine, pyridine or pyrrolidine, and the hydrophilic chain extender is dimethylolpropionic acid (DMPA) or 4,4-diaminodiphenyl sulfide.

4. The method for preparing the self-healing conductive polymer adhesive as described in claim 1, characterized in that, In the prepolymerization step, 140 parts of polytetrahydrofuran ether diol were added to the first reaction vessel, the first reaction vessel was heated to 60°C, and then 50 parts of isoflavone diisocyanate and 0.5 parts of dibutyltin dilaurate were added to it. The first reaction vessel was then heated to 75°C and maintained for 1 hour. Add 2 parts of dimethylolpropionic acid to the first reaction vessel, adjust the temperature of the first reaction vessel to 80°C, and stir the reaction at 400-800 RPM for 6-8 hours. After the reaction is completed, the prepolymer is obtained.

5. The method for preparing the self-healing conductive polymer adhesive as described in claim 1, characterized in that, In the repolymerization step, the temperature of the first reaction vessel is adjusted to 45°C and 40 parts of methyl methacrylate are added to the first reaction vessel. The temperature of the first reaction vessel is then raised to 75°C and maintained for 3 hours. After the reaction is completed, the first reaction vessel is cooled to room temperature to obtain the repolymer.

6. The method for preparing the self-healing conductive polymer adhesive as described in claim 1, characterized in that, In the emulsification step, the emulsifier is sodium dodecyl sulfate or dodecylphenol polyoxyethylene ether; The stirring speed is 600-1500 RPM.

7. The method for preparing the self-healing conductive polymer adhesive as described in claim 1, characterized in that, In the post-polymerization step, the polymerization initiator is a mixed solution with a mass fraction of 0.3% to 1.5%, and the solute of the polymerization initiator is sodium persulfate, potassium persulfate, or ammonium persulfate; The stirring speed is 300-800 RPM.

8. A self-healing conductive polymer adhesive, characterized in that, The self-healing conductive polymer adhesive is prepared using the preparation method of the self-healing conductive polymer adhesive according to any one of claims 1-7.

9. A lithium-ion battery, characterized in that, Includes the self-healing conductive polymer adhesive as described in claim 8.

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