Lithium ion negative electrode binder as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of binders for lithium ion batteries, and particularly relates to a lithium ion negative electrode binder which is characterized by comprising the following components: an ion conductor polymer, a pole piece toughening aid and a solvent, and the mass ratio of the ion conductor polymer to the pole piece toughening aid is (2-20): 1; the ionic conductor polymer is a copolymer of polyethylene glycol and diallyldimethylammonium chloride, wherein the mass ratio of polyethylene glycol to diallyldimethylammonium chloride is (1-5): (5-1); the pole piece toughening auxiliary agent is any one of N-hydroxymethyl acrylamide and hydroxyethyl acrylate or a combination of the N-hydroxymethyl acrylamide and the hydroxyethyl acrylate; in the lithium ion negative electrode binder, the ion conductor polymer and the pole piece toughening aid are subjected to graft polymerization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery binders, and particularly relates to a lithium ion negative electrode binder and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of the new energy automobile industry, the market demand for high energy density, high power and long cycle lithium ion power batteries is increasing. At the Pack module end, the charging voltage of the power battery is constantly advancing from 200V to 800V, and the charging rate is developing from 50kW, 100kW to 200kW. In order to continuously improve the fast charging performance of lithium ion batteries, in addition to measures such as reducing the particle size of the negative electrode material and regulating the electrolyte, the role of the negative electrode binder cannot be ignored.

[0003] In the prior art, acrylate polymers can be used as binders to improve the flexibility and kinetic performance of electrodes because they have high flexibility and contain some electronegative elements. For example, poly(methyl acrylate lithium) PMALi can provide free lithium ions, thereby shortening the lithium ion diffusion path and improving the diffusion rate of lithium ions. However, the glass transition temperature Tg of poly(methyl acrylate lithium) PMALi is relatively high, and the relatively hard and brittle molecular chain segment movement ability is insufficient, and the ion conductivity improvement effect is limited. High toughness type (such as some flexible acrylates) can improve ion transport performance and buffer volume changes, but the adhesion may be insufficient, and the active material cannot be firmly "grabbed", and peeling will also occur during the cycle process, resulting in damage to the electrode structure. The new generation of lithium ion batteries with high energy density demand have shown signs of fatigue in ion conductivity, and how to overcome the defects of insufficient ion conductivity of the negative electrode binder is a technical problem that needs to be solved in the field.

[0004] The present application improves the ion conductivity of the high polymer by designing an organic combination of ion conductor polymer and pole piece toughening aid, reduces the internal resistance of the negative electrode piece, and at the same time ensures high mechanical strength, which helps to improve the fast charging performance of lithium batteries.

[0005] It should be noted that the above information disclosed in the background section of the present application is only used to understand the background of the present application, and therefore, the above description is not considered to constitute prior art information. SUMMARY

[0006] The present application provides at least a kind of lithium ion negative electrode binder and a preparation method and application thereof.

[0007] In a first aspect, embodiments of this disclosure provide a lithium-ion anode binder, comprising the following components: an ion-conducting polymer, an electrode toughening agent, and a solvent, wherein the mass ratio of the ion-conducting polymer to the electrode toughening agent is 2–20:1; the ion-conducting polymer is a copolymer of polyethylene glycol and diallyl dimethyl ammonium chloride, wherein the mass ratio of polyethylene glycol to diallyl dimethyl ammonium chloride is 1–5:5–1; the electrode toughening agent is any one or a combination of two of N-hydroxymethylacrylamide and hydroxyethyl acrylate; in the lithium-ion anode binder, the ion-conducting polymer and the electrode toughening agent are grafted polymers.

[0008] In one optional embodiment, the weight-average molecular weight of the lithium-ion anode binder is 200,000 to 2,000,000.

[0009] In one optional embodiment, the lithium-ion anode binder simultaneously meets the following conditions: the peel strength of the lithium-ion anode binder after coating is ≥300 N / m, and the peel strength after immersion in electrolyte is ≥200 N / m; the molecular weight distribution (PDI) of the lithium-ion anode binder is <2.0; 1% carbon black powder is dispersed in a 1% aqueous solution of the lithium-ion anode binder using a dispersion disc at a dispersion linear velocity of 5 m / s, and the slurry fineness is less than 40 μm after 6 hours of dispersion.

[0010] In one optional embodiment, the elongation at break of the film formed by the lithium-ion anode binder is ≥25%.

[0011] Secondly, this disclosure also provides a method for preparing the lithium-ion anode binder as described above, comprising the following steps: S1, adding solvent, polyethylene glycol, and diallyl dimethyl ammonium chloride to a reactor, starting stirring and heating to obtain a comonomer; S2, dissolving an initiator in a solution, and adding the initiator, comonomer, and solvent dropwise to the reactor after the initiator, comonomer, and solvent are mixed evenly, and then reacting at a constant temperature after the dropwise addition is completed; S3, adding the initiator, electrode toughening agent, and solvent dropwise to the reactor after the initiator, electrode toughening agent, and solvent are mixed evenly to react, then naturally cooling to room temperature, adding alkali solution and deionized water, adjusting the solid content and pH value to obtain the lithium-ion anode binder.

[0012] In one optional embodiment, the heating temperature range in step S1 is 60–80°C.

[0013] In one optional embodiment, the temperature range of the isothermal reaction in steps S2 and S3 is 60–90°C.

[0014] Thirdly, embodiments of this disclosure also provide a lithium-ion negative electrode sheet, comprising the lithium-ion negative electrode binder as described above, wherein the amount of the lithium-ion negative electrode binder added accounts for 1% to 3% of the total mass of the lithium-ion negative electrode sheet.

[0015] In one optional embodiment, the film resistance of the lithium-ion negative electrode is 0.2 to 0.5 Ω·m.

[0016] Fourthly, embodiments of this disclosure also provide an application of the lithium-ion anode binder as described above in the field of lithium-ion anode sheets.

[0017] Compared to existing technologies, the lithium battery negative electrode binder provided by this invention has the following significant advantages: The core of this invention lies in the introduction of an ion-conducting polymer with a specific structure and ratio. The polyethylene glycol (PEG) segment can coordinate with lithium ions, effectively promoting their dissociation and migration, and is the cornerstone for improving lithium-ion conductivity. The diallyl dimethyl ammonium chloride segment provides stable cationic groups, which helps form more stable ion channels and may improve electrolyte wettability through electrostatic interactions. By copolymerizing these two segments in a specific mass ratio, the synergistic and optimized ion conduction function is achieved, making the binder itself no longer merely an "insulating" adhesive material, but rather an ion-conducting network within the electrode. This greatly reduces the transmission impedance of lithium ions between electrode particles, thereby directly improving the fast-charging performance of the lithium battery.

[0018] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0022] In this document, as used herein, expressions such as “at least one of…” modify the entire list of elements when following a list of elements, rather than individual elements in the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0023] The terminology used herein is for the purpose of describing specific exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may also be intended to include plural forms unless otherwise clearly stated herein. The terms “comprising,” “including,” and “having” are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the specific order discussed or shown, unless specifically identified as such. Additional or alternative steps may be employed.

[0024] The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0025] This disclosure provides a lithium-ion anode binder comprising the following components: an ion-conducting polymer, an electrode toughening agent, and a solvent, wherein the mass ratio of the ion-conducting polymer to the electrode toughening agent is 2–20:1; the ion-conducting polymer is a copolymer of polyethylene glycol and diallyl dimethyl ammonium chloride, wherein the mass ratio of polyethylene glycol to diallyl dimethyl ammonium chloride is 1–5:5–1; the electrode toughening agent is any one or a combination of two of N-hydroxymethylacrylamide and hydroxyethyl acrylate; in the lithium-ion anode binder, the ion-conducting polymer and the electrode toughening agent are grafted polymers.

[0026] Specifically, the core of this invention lies in the introduction of an ion-conducting polymer (a copolymer of polyethylene glycol and diallyl dimethyl ammonium chloride) with a specific structure and ratio. The polyethylene glycol (PEG) segments can coordinate with lithium ions, effectively promoting their dissociation and migration, and are the cornerstone of improved lithium-ion conductivity. The diallyl dimethyl ammonium chloride segments provide stable cationic groups, which help form more stable ion channels and may improve electrolyte wettability through electrostatic interactions. By copolymerizing these two segments in a specific mass ratio (1–5:5–1), synergistic optimization of ion conduction functions is achieved, making the binder itself no longer merely an "insulating" adhesive material, but rather an ion-conducting network within the electrode. This significantly reduces the transmission impedance of lithium ions between electrode particles, thereby directly improving the fast-charging performance of lithium batteries.

[0027] Specifically, this invention utilizes graft polymerization to chemically bond ion-conducting polymers with electrode toughening agents (N-hydroxymethylacrylamide and / or hydroxyethyl acrylate). The introduction of the electrode toughening agent allows its active functional groups (such as hydroxymethyl and hydroxyl groups) to form partial crosslinks with the carboxyl groups in the system, as well as self-crosslinking through hydroxyl dehydration, thereby effectively enhancing the toughness, cohesion, and adhesion to the current collector of the binder system. This structure not only effectively buffers the significant volume expansion / contraction (~300%) of the negative electrode material (such as silicon-carbon material) during charging and discharging, suppressing electrode pulverization, but also ensures that the electrode structure remains intact and stable under high ion conductivity. This collectively guarantees that the battery maintains excellent structural stability and long cycle life even under long-term cycling, especially under high-current fast charging conditions.

[0028] Specifically, controlling the mass ratio of the ion-conducting polymer to the electrode toughening agent within 2–20:1 is key to this invention. This ratio range ensures that while achieving extremely high ionic conductivity, the binder system still possesses sufficient mechanical strength and adhesion. Too low a ratio (too much toughening agent) weakens the ion-conducting network; too high a ratio (too much ion-conducting polymer) may lead to insufficient electrode structural strength. At this optimized ratio, the performance of both is balanced, achieving both "high ionic conductivity" and "high mechanical strength," which is unattainable with conventional physical blend binders.

[0029] In some embodiments, specifically, the weight-average molecular weight of the lithium-ion anode binder is 200,000 to 2,000,000.

[0030] In some embodiments, specifically, the lithium-ion anode binder simultaneously meets the following conditions: the lithium-ion anode binder is coated on the smooth surface of the lithium battery electrolytic copper foil with a wet film thickness of 100 μm, and after drying at 80°C for 1 hour, the peel strength of the coating at 180°C is ≥300 N / m, and the peel strength after immersion in electrolyte is ≥200 N / m; the molecular weight distribution (PDI) of the lithium-ion anode binder is <2.0; the lithium-ion anode binder is used to disperse 1% carbon black powder in a 1% aqueous solution using a dispersion disc at a dispersion linear velocity of 5 m / s, and the fineness of the slurry after 6 hours of dispersion is less than 40 μm.

[0031] In some embodiments, specifically, the elongation at break of the film formed by the lithium-ion anode binder is ≥25%.

[0032] This disclosure also provides a method for preparing the lithium-ion anode binder as described above, comprising the following steps: S1, adding solvent, polyethylene glycol, and diallyl dimethyl ammonium chloride to a reactor, starting stirring and heating to obtain a comonomer; S2, dissolving an initiator in the solution, and adding the initiator, comonomer, and solvent dropwise to the reactor after the initiator, comonomer, and solvent are mixed evenly, and reacting at a constant temperature for 4-6 hours after the dropwise addition is completed; S3, adding the initiator, electrode toughening agent, and solvent dropwise to the reactor after the dropwise addition is completed, reacting for 6-10 hours after the dropwise addition is completed, then naturally cooling to room temperature, adding alkali solution and deionized water, adjusting the solid content and pH value to obtain the lithium-ion anode binder.

[0033] In some embodiments, specifically, the heating temperature range in step S1 is 60–80°C.

[0034] In some embodiments, specifically, the temperature range of the isothermal reaction in steps S2 and S3 is 60–90°C.

[0035] This disclosure also provides a lithium-ion negative electrode sheet, comprising the lithium-ion negative electrode binder as described above, wherein the amount of the lithium-ion negative electrode binder added accounts for 1% to 3% of the total mass of the lithium-ion negative electrode sheet.

[0036] In some embodiments, specifically, the film resistance of the lithium-ion negative electrode is 0.2 to 0.5 Ω·m.

[0037] This disclosure also provides an application of the lithium-ion anode binder as described above in the field of lithium-ion anode sheets.

[0038] The specific performance testing methods for the adhesive front end are as follows: Peel strength test of adhesive Peel strength was tested using a tensile testing machine. The smooth surface of 7µm lithium battery electrolytic copper foil was selected and uniformly coated with a wet film thickness of 100µm using a small laboratory coating machine. The copper foil coated with adhesive was then transferred to a forced-air drying oven and dried at 80℃ for 1 hour. The coated sample was then cut into 30mm*70mm test pieces. 3M pressure-sensitive 3M-VHB double-sided tape was attached to the side of the test piece coated with the negative electrode paste, and the other side of the double-sided tape was attached to a stainless steel plate. The stainless steel plate and the test piece were fixed on the fixture of a tensile testing instrument and a 180-degree peel test was performed at a speed of 50mm / min. The force detected when the copper current collector was completely peeled off is the peel force.

[0039] Wherein, peel strength = peel force / spline width.

[0040] The sample was immersed in an electrolyte solution of 1M lithium hexafluorophosphate with EC / DEC / EMC=3 / 5 / 2 and wt% for 24 hours at 60°C. After immersion, the sample was removed, dried, and the peel strength was tested. The peel strength after immersion is the peel strength of the sample.

[0041] Carbon black dispersibility The binder was diluted with deionized water to a solid content of 1%, and then 1% carbon black (Temiga SP-Li) powder by mass of the solution was added. The mixture was dispersed on a small laboratory disperser at a linear speed of 5 m / s. After 6 hours of dispersion, a sample was taken and the fineness was tested using a scraper fineness meter.

[0042] Elongation at break The adhesive sample was placed in a polytetrafluoroethylene mold and dried in a 40℃ forced-air drying oven for 24 hours and then dried at 80℃ for 2 hours to obtain a film with a thickness of 0.05-0.2 mm. The sample was cut into strips using a dumbbell-shaped mold and fixed on the fixture of a tensile testing instrument. The tensile test was performed at a speed of 50 mm / min to test the elongation at break.

[0043] Polymer average molecular weight and molecular weight distribution Testing instruments: Pump: Agilent HPLC1260iso Pump G1310B Automated sampler: Agilent HPLC 1260 ALS G1329B Column: Waters Ultrahydrogel 300x7.8mm 500-250-120A Column oven: Agilent HPLC 1260 TCC G1316A Detector: Agilent RID G1362A Test methods include (1) calibration, (2) sample pretreatment and (3) sample testing. Correction: Prepare 5–10 calibration standard solutions with different average molecular weights (MWH) using the mobile phase as the solvent, with a mass concentration of 1.0 g / L. Gently shake and then allow to stand for at least 12 hours to allow for complete dissolution. Avoid using methods such as ultrasound or heating to accelerate dissolution.

[0044] Set the column temperature to 30℃ and the mobile phase flow rate to 0.5 mL / min to 1.2 mL / min. Wash the column with the mobile phase until the baseline is stable.

[0045] Using an autosampler, a calibration standard solution is injected, and the retention time of the corresponding peak for each standard is recorded by the data acquisition and processing system.

[0046] Establish a calibration curve, repeat the above operation at least three times, calculate the average retention time of each standard sample, plot the average retention time of each standard sample against lgMi, and perform linear fitting. The linear correlation coefficient R should not be less than 0.9995. If the R value does not meet the requirements, the calibration steps need to be repeated for the standard sample that caused the poor calibration. The poor calibration point can be found by calculating the difference between the actual average molecular weight and the average molecular weight calculated using the polynomial of the best-fit line.

[0047] Sample pretreatment Take 2g to 5g of sample, adjust the pH value to 7 to 9 with sodium hydroxide solution, place it in a vacuum drying oven, and dry it to constant weight at a vacuum degree of 0.1MPa and (74±2)℃.

[0048] Sample testing: Prepare a sample solution from the dried sample and perform chromatographic analysis.

[0049] The specific performance testing methods for the negative electrode are as follows: negative electrode coating peel strength Peel strength was tested using a tensile testing machine. The coated negative electrode sheet was cut into 30mm*70mm test pieces. 3M varistor 3M-VHB double-sided tape was applied to the side of the test piece coated with the negative electrode paste, and the other side of the tape was attached to a stainless steel plate. The stainless steel plate and the test piece were fixed to the fixture of a tensile testing instrument. A 180-degree peel test was performed at a speed of 50mm / min. The force detected when the aluminum current collector was completely peeled off is the peel force. Peel strength = peel force / spline width The performance indicators are as follows: Excellent: Peel force > 9 N / m; Good: Peel force 8-9 N / m; Average: Peel force 7-8 N / m; Poor: Peel force < 7 N / m.

[0050] Secondary battery cycle performance Ten lithium-ion rechargeable batteries were fabricated and charged to 4.2V using a 10C constant current method and discharged to 3V using a 1C constant current method at 25℃, constituting one cycle. 200 cycles were performed. The ratio of the capacitance after 200 cycles to the average capacitance at the end of 5 cycles was calculated. The discharge capacity retention rate = (average capacitance at the end of 200 cycles / average capacitance at the end of 5 cycles) * 100.

[0051] The higher the capacity retention rate at a 10C charging rate, the better the fast charging performance and the better the high-rate cycle performance of the battery. Example 1

[0052] Adhesive preparation: Deionized water solvent, 10 parts polyethylene glycol and 50 parts diallyl dimethyl ammonium chloride were added to the reactor, and stirring and heating were started to raise the temperature to 60°C; then 0.3 parts initiator ammonium persulfate, 35 parts acrylic acid and deionized water solvent were mixed and added dropwise to the reactor, and the temperature was raised to 80°C; after the dropwise addition was completed, the reaction was kept at the temperature for 6 hours; finally, 0.3 parts initiator, 5 parts N-hydroxymethylacrylamide and deionized water solvent were mixed and added to the reactor, and the temperature was kept at the temperature for another 6 hours.

[0053] The obtained binder was coated on the smooth surface of the lithium battery electrolytic copper foil with a wet film thickness of 100 μm. After drying at 80°C for 1 h, the peel strength of the coating at 180°C was 525 N / m, and the peel strength after immersion in electrolyte was 346 N / m. The molecular weight distribution coefficient (PDI) of the obtained binder was 1.5, and the weight-average molecular weight was 50 W. The elongation at break of the film made with the obtained binder was 54%. Example 2

[0054] Adhesive preparation: Add deionized water, 50 parts polyethylene glycol and 10 parts diallyl dimethyl ammonium chloride to the reactor, start stirring and heating, and raise the temperature to 80°C; then add 0.3 parts ammonium persulfate initiator, 35 parts lithium acrylate and deionized water to the reactor dropwise, and raise the temperature to 80°C; after the dropwise addition is completed, keep the reaction at this temperature for 4 hours; finally, add 0.3 parts initiator, 5 parts hydroxyethyl acrylate and deionized water to the reactor, and continue to keep the temperature at this temperature for 6 hours.

[0055] The obtained binder was coated on the smooth surface of the lithium battery electrolytic copper foil with a wet film thickness of 100 μm. After drying at 80°C for 1 h, the peel strength of the coating at 180°C was 606 N / m, and the peel strength after immersion in electrolyte was 462 N / m. The molecular weight distribution coefficient (PDI) of the obtained binder was 1.7, and the weight-average molecular weight was 60 W. The elongation at break of the film made with the obtained binder was 25%. Example 3

[0056] Adhesive preparation: Deionized water solvent, 40 parts polyethylene glycol and 40 parts diallyl dimethyl ammonium chloride were added to the reactor, and stirring and heating were started to raise the temperature to 70°C; then 0.5 parts initiator ammonium persulfate, 16 parts acrylic acid and deionized water solvent were mixed and added dropwise to the reactor, and the temperature was raised to 80°C; after the dropwise addition was completed, the reaction was kept at the temperature for 6 hours; finally, 0.5 parts initiator, 4 parts hydroxyethyl acrylate and deionized water solvent were mixed and added to the reactor, and the temperature was kept at the temperature for another 10 hours.

[0057] The obtained binder was coated on the smooth surface of the lithium battery electrolytic copper foil with a wet film thickness of 100 μm. After drying at 80°C for 1 h, the peel strength of the coating at 180°C was 630 N / m, and the peel strength after immersion in electrolyte was 301 N / m. The molecular weight distribution coefficient (PDI) of the obtained binder was 1.4, and the weight-average molecular weight was 100 W. The elongation at break of the film made with the obtained binder was 80%. Example 4

[0058] Adhesive preparation: Deionized water solvent, 20 parts polyethylene glycol and 40 parts diallyl dimethyl ammonium chloride were added to the reactor, and stirring and heating were started to raise the temperature to 70°C; then 0.5 parts ammonium persulfate initiator, 10 parts lithium methacrylate and deionized water solvent were mixed and added dropwise to the reactor, and the temperature was raised to 80°C; after the dropwise addition was completed, the reaction was kept at this temperature for 6 hours; finally, 0.5 parts initiator, 30 parts hydroxyethyl acrylate and deionized water solvent were mixed and added to the reactor, and the temperature was kept at this temperature for another 10 hours.

[0059] The obtained adhesive was coated on the smooth surface of the lithium battery electrolytic copper foil with a wet film thickness of 100 μm. After drying at 80°C for 1 hour, the peel strength of the coating at 180°C was 550 N / m, and the peel strength after immersion in electrolyte was 518 N / m. The elongation at break of the film made with the obtained adhesive was 40%. Example 5

[0060] Adhesive preparation: Deionized water, 40 parts polyethylene glycol, and 20 parts diallyl dimethyl ammonium chloride were added to the reactor, and stirring and heating were started to raise the temperature to 80°C. Then, 0.3 parts ammonium persulfate, 30 parts lithium acrylate, and deionized water were mixed and added dropwise to the reactor, and the temperature was raised to 70°C. After the dropwise addition was completed, the reaction was kept at this temperature for 6 hours. Finally, 0.3 parts N-hydroxymethyl acrylamide, 5 parts hydroxyethyl acrylate, and deionized water were mixed and added to the reactor, and the temperature was kept at this temperature for another 10 hours.

[0061] The obtained binder was coated on the smooth surface of the lithium battery electrolytic copper foil with a wet film thickness of 100 μm. After drying at 80°C for 1 h, the peel strength of the coating at 180°C was 489 N / m, and the peel strength after immersion in electrolyte was 468 N / m. The molecular weight distribution coefficient (PDI) of the obtained binder was 1.6, and the weight-average molecular weight was 80 W. The elongation at break of the film made with the obtained binder was 60%.

[0062] Comparative Example 1 Adhesive preparation: Add deionized water, 5 parts polyethylene glycol and 30 parts diallyl dimethyl ammonium chloride to the reactor, start stirring and heating, and raise the temperature to 70°C; then add 0.5 parts ammonium persulfate initiator, 45 parts acrylic acid and deionized water to the reactor dropwise, and raise the temperature to 80°C; after the dropwise addition is completed, keep the reaction at this temperature for 6 hours; finally, add 0.5 parts initiator, 20 parts hydroxyethyl acrylate and deionized water to the reactor, and continue to keep the temperature at this temperature for 10 hours.

[0063] The obtained binder was coated on the smooth surface of the lithium battery electrolytic copper foil with a wet film thickness of 100 μm. After drying at 80°C for 1 h, the peel strength of the coating at 180°C was 407 N / m, and the peel strength after immersion in electrolyte was 253 N / m. The molecular weight distribution coefficient (PDI) of the obtained binder was 2.1, and the weight-average molecular weight was 120 W. The elongation at break of the film made with the obtained binder was 10%.

[0064] Comparative Example 2 Adhesive preparation: Deionized water, 30 parts polyethylene glycol, and 5 parts diallyl dimethyl ammonium chloride were added to the reactor, and stirring and heating were started to raise the temperature to 70°C. Then, 0.5 parts ammonium persulfate initiator, 50 parts acrylic acid, and deionized water were mixed and added dropwise to the reactor, and the temperature was raised to 80°C. After the dropwise addition was completed, the reaction was kept at this temperature for 6 hours. Finally, 0.5 parts initiator, 1 part N-hydroxymethylacrylamide, and deionized water were mixed and added to the reactor, and the temperature was kept at this temperature for another 10 hours.

[0065] The obtained binder was coated on the smooth surface of the lithium battery electrolytic copper foil with a wet film thickness of 100 μm. After drying at 80°C for 1 h, the peel strength of the coating at 180°C was 208 N / m, and the peel strength after immersion in electrolyte was 124 N / m. The molecular weight distribution coefficient (PDI) of the obtained binder was 2.3, and the weight-average molecular weight was 10 W. The elongation at break of the film made with the obtained binder was 50%.

[0066] The negative electrode binders obtained in Examples 1-5 and Comparative Examples 1-2 were used to prepare negative electrode sheets, and their back-end performance was tested. The results are shown in Table 1 below.

[0067] Table 1

[0068] In summary, this lithium-ion anode binder and its preparation method integrate ion conduction and structural enhancement functions through molecular design, resulting in a lithium battery anode with extremely low interfacial and bulk ion impedance, significantly improving rate performance and meeting fast-charging requirements. The robust and resilient electrode structure effectively suppresses capacity decay during cycling. Excellent interfacial stability reduces side reactions and enhances battery safety. Therefore, the binder provided by this invention is a highly efficient and innovative material solution for resolving the contradiction between fast-charging performance and long cycle life in current high-energy-density lithium batteries.

[0069] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A lithium-ion anode binder, characterized in that, It includes the following components: The mixture comprises an ion conductor polymer, an electrode toughening agent, and a solvent, wherein the mass ratio of the ion conductor polymer to the electrode toughening agent is 2 to 20:

1. The ion conductor polymer is a copolymer of polyethylene glycol and diallyl dimethyl ammonium chloride, wherein the mass ratio of polyethylene glycol to diallyl dimethyl ammonium chloride is 1-5:5-1; The electrode toughening agent is any one or a combination of two of N-hydroxymethylacrylamide and hydroxyethyl acrylate. In the lithium-ion anode binder, the ion conductor polymer and the electrode toughening agent are graft polymers.

2. The lithium-ion anode binder as described in claim 1, characterized in that, The weight-average molecular weight of the lithium-ion anode binder is 200,000 to 2,000,000.

3. The lithium-ion anode binder as described in claim 1, characterized in that, The peel strength of the lithium-ion negative electrode after coating with the binder is ≥300N / m, and the peel strength after immersion in electrolyte is ≥200N / m. The molecular weight distribution (PDI) of the lithium-ion anode binder is <2.0; The lithium-ion anode binder is dissolved in an aqueous solution with a mass fraction of 1% and carbon black powder with a mass fraction of 1% is dispersed in a dispersion disc at a dispersion linear velocity of 5 m / s. After 6 hours of dispersion, the fineness of the slurry is less than 40 μm.

4. The lithium-ion anode binder as described in claim 1, characterized in that, The elongation at break of the film formed by the lithium-ion anode binder is ≥25%.

5. A method for preparing a lithium-ion anode binder as described in any one of claims 1-4, characterized in that, Includes the following steps: S1, add solvent, polyethylene glycol, and diallyldimethylammonium chloride to the reactor, start stirring and heating to obtain the comonomer; S2, dissolve the initiator in the solution, and add it dropwise to the reactor after the initiator, comonomer and solvent are mixed evenly. After the addition is completed, the reaction is carried out at a constant temperature. S3, after the initiator, electrode toughening agent and solvent are mixed evenly, is added dropwise to the reactor to react, then cooled to room temperature, alkali solution and deionized water are added, and the solid content and pH value are adjusted to obtain lithium-ion negative electrode binder.

6. The preparation method according to claim 5, characterized in that, The heating temperature range in step S1 is 60–80°C.

7. The preparation method according to claim 5, characterized in that, The temperature range for the isothermal reaction in steps S2 and S3 is 60–90°C.

8. A lithium-ion negative electrode sheet, characterized in that, The lithium-ion anode binder as described in any one of claims 1-4 is included, wherein the amount of the lithium-ion anode binder added accounts for 1% to 3% of the total mass of the lithium-ion anode sheet.

9. The lithium-ion negative electrode sheet as described in claim 8, characterized in that, The film resistance of the lithium-ion negative electrode is 0.2 to 0.5 Ω·m.

10. The application of the lithium-ion anode binder as described in any one of claims 1-4 in the field of lithium-ion anode sheets.

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