A combined energy storage battery positive electrode and a preparation method thereof
By introducing a modified polyvinylidene fluoride (PVDF) binder into the positive electrode of a lithium-ion battery, the problems of PVDF binder being unable to fix active materials and buffer volume changes are solved, resulting in better electrode structure stability and improved battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YANGZHOU KAIDI POWER CO LTD
- Filing Date
- 2025-05-21
- Publication Date
- 2026-05-15
AI Technical Summary
In existing lithium-ion batteries, polyvinylidene fluoride binders cannot effectively fix the positive electrode active material due to weak polar surface interactions and rigid molecular structure. This leads to the active material falling off during charging and discharging, affecting battery capacity. Furthermore, they are unable to buffer the mechanical stress caused by volume changes in the positive electrode material, resulting in unstable electrode structure.
A modified polyvinylidene fluoride (PVDF) binder is used. By introducing ester groups and pyrimidine structures with strong coordination ability into PVDF, the toughness and chain segment mobility of the binder are improved by utilizing the mercapto-alkene click reaction. The combination of the pyrimidine structure enhances the interaction between molecular chains and inhibits the shuttle effect of active materials and the propagation of electrode cracks.
It improves the binder's ability to anchor active materials, suppresses volume changes during charging and discharging, extends the battery's cycle life, reduces the battery's internal resistance, and improves the battery's charge and discharge efficiency and cycle capacity retention.
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Figure BDA0005413133340000081 
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium battery technology, specifically, it relates to a combined energy storage battery cathode and its preparation method. Background Technology
[0002] Lithium-ion batteries are currently the most commonly used energy storage batteries on the market, consisting of a positive electrode, a negative electrode, a separator, and an electrolyte. Although the amount of binder used in the positive electrode system of a lithium-ion battery is relatively small, it is a key component in maintaining the integrity of the electrode structure and its electrochemical performance. The most commonly used binder in current lithium-ion battery technology is polyvinylidene fluoride (PVDF). PVDF binders have good electrochemical stability and high-temperature resistance, and good resistance to organic solvents. However, due to its weakly polar surface interactions and rigid molecular structure, PVDF binders lack the ability to fix the positive electrode active material and cannot effectively suppress the shuttle effect of the active material. During long-term charge-discharge cycles, the active material gradually detaches, affecting the battery capacity.
[0003] Furthermore, during the charging and discharging process of lithium-ion batteries, the cathode material often undergoes significant lattice volume changes, resulting in periodic mechanical stress inside the electrode. Polyvinylidene fluoride, due to its poor toughness, is unable to buffer this dynamic strain. To address the above technical defects, this invention provides a combined energy storage battery cathode and its preparation method. Summary of the Invention
[0004] The purpose of this invention is to provide a combined energy storage battery positive electrode and its preparation method, in order to solve the problems mentioned in the background art.
[0005] The objective of this invention can be achieved through the following technical solutions:
[0006] A combined energy storage battery positive electrode includes a current collector and a conductive agent, an active material, and a binder on the surface of the current collector;
[0007] Furthermore, the current collector is one of aluminum foil or aluminum foam.
[0008] Furthermore, the conductive agent is any one or a mixture of acetylene black, graphene, and carbon nanotubes.
[0009] Furthermore, the active material is a lithium salt, including at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese phosphate, and lithium vanadium phosphate.
[0010] Furthermore, the adhesive is modified polyvinylidene fluoride (PVDF), and the modification method of PVDF includes the following steps:
[0011] S1. Under nitrogen protection, 2,4-dihydroxy-6-methylpyrimidine, 3-mercaptopropionic acid, and p-toluenesulfonic acid were mixed in a four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and water separator. After turning on the mechanical stirrer, the system temperature was raised to 80-90℃ and reacted at 80-90℃ for 6-8 hours. During the reaction, the water produced was continuously separated. After the reaction was completed, the crude product was washed with deionized water and dried to obtain a photocuring agent.
[0012] S2. Polyvinylidene fluoride, 1,8-diazabicyclo(5,4,0)-7-undecene (DBU), and N,N-dimethylacetamide were added to a four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser. After turning on the mechanical stirrer, the temperature of the system was raised to 60-80℃ and reacted at 60-80℃ for 12-16 hours. After the reaction was completed, the mixture was filtered and the filtrate was poured into deionized water to precipitate. The precipitate was then filtered out and washed with anhydrous ethanol and deionized water in sequence and dried to obtain polyvinylidene fluoride with double bonds.
[0013] S3. The photocuring agent, polyvinylidene fluoride with double bonds, and initiator are dissolved in N,N-dimethylacetamide, and then cast into a film on a polytetrafluoroethylene plate. After drying, the film is cross-linked by photocuring to obtain modified polyvinylidene fluoride.
[0014] Furthermore, the initiator is one of 2-hydroxy-2-methylphenylacetone, 1-hydroxycyclohexylphenyl ketone, and benzoyldimethyl ketal.
[0015] Furthermore, the mass ratio of 2,4-dihydroxy-6-methylpyrimidine, 3-mercaptopropionic acid, and p-toluenesulfonic acid used in S1 is 12.6–14: 23.3–26.5: 0.6–1.2.
[0016] Furthermore, the mass ratio of polyvinylidene fluoride, 1,8-diazabicyclo(5,4,0)-7-undecene, and N,N-dimethylacetamide used in S2 is 14–18:7–12:120–240.
[0017] Furthermore, the mass ratio of the photocuring agent, polyvinylidene fluoride with double bonds, initiator, and N,N-dimethylacetamide used in S3 is 3-4:12-16:0.3-0.6:120-240.
[0018] Furthermore, the photocuring crosslinking conditions in S3 are as follows: ultraviolet light intensity of 100–300 mW / cm². 2 Curing and crosslinking under the specified conditions for 40–80 minutes.
[0019] A method for preparing the positive electrode of a combined energy storage battery includes the following steps:
[0020] The conductive agent, active material and binder are dissolved in an organic solvent and coated onto the surface of the current collector. After drying to remove the solvent, the positive electrode of the combined energy storage battery is obtained.
[0021] Furthermore, the mass ratio of active material, conductive agent, and binder is 91-95:2-4:3-5.
[0022] Furthermore, the organic solvent is one of N-methylpyrrolidone and N,N-dimethylacetamide.
[0023] Furthermore, the drying temperature conditions are 130–170°C.
[0024] This invention has at least one of the following beneficial effects:
[0025] 1) This invention uses 2,4-dihydroxy-6-methylpyrimidine and 3-mercaptopropionic acid as raw materials. Under the catalysis of p-toluenesulfonic acid, an esterification reaction is carried out to obtain a photocuring agent with two thiol structures. Then, DBU is used to react on the surface of polyvinylidene fluoride to eliminate hydrogen fluoride and introduce double bonds to obtain polyvinylidene fluoride with double bonds. Finally, the photocuring agent is used to modify the polyvinylidene fluoride with double bonds by a thiol-olefin click reaction to obtain a modified polyvinylidene fluoride. This invention introduces ester groups and pyrimidine structures with strong coordination ability into polyvinylidene fluoride, which effectively improves the anchoring ability of polyvinylidene fluoride binder to the active materials in the energy storage battery, can better suppress the shuttle effect of active materials during charging and discharging, and effectively extend the cycle life of the energy storage battery.
[0026] 2) This invention utilizes an olefin-click reaction to introduce flexible thioether bonds and heterocyclic pyrimidine structures into polyvinylidene fluoride (PVDF) binders. The thioether bonds can improve the mobility of local chain segments and reduce stress concentration, while the pyrimidine structures can enhance the interaction between molecular chains through their own π-bond stacking. The two work synergistically to improve the toughness and deformation recovery ability of PVDF binders, better cope with the volume changes of the cathode material during charging and discharging, suppress the propagation of electrode cracks caused by volume expansion, maintain the integrity of the conductive network, and reduce the internal resistance of the battery.
[0027] 3) Currently, the most commonly used lithium salt in lithium-ion battery electrolytes is lithium hexafluorophosphate. However, lithium hexafluorophosphate is sensitive to water and reacts with trace amounts of water to generate hydrofluoric acid, which corrodes the electrodes / current collectors and accelerates battery capacity decay. The modified polyvinylidene fluoride binder of this invention contains a pyrimidine ring structure. The pyrimidine ring has a basic nitrogen atom, which can neutralize the hydrofluoric acid in the electrolyte and eliminate the corrosive and destructive effects of the hydrofluoric acid in the electrolyte on the positive electrode material. Detailed Implementation
[0028] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.
[0029] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.
[0030] It should be understood that the order of the steps or the order in which certain actions are performed is not important as long as the invention remains operational. Furthermore, two or more steps or actions can be performed simultaneously.
[0031] The use of any and all instances or exemplary language such as “e.g.” or “including” in this document is merely intended to better illustrate the invention and is not intended to limit the scope of the invention unless the claims are made. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of the invention.
[0032] Example 1
[0033] A modified polyvinylidene fluoride adhesive is prepared by the following steps:
[0034] S1. Under nitrogen protection, 12g of 2,4-dihydroxy-6-methylpyrimidine, 23.3g of 3-mercaptopropionic acid, and 0.6g of p-toluenesulfonic acid were mixed in a four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and water separator. After turning on the mechanical stirrer, the system temperature was raised to 80℃ and reacted at 80℃ for 8 hours. During the reaction, the water produced was continuously separated. After the reaction was completed, the crude product was washed with deionized water and dried to obtain a photocuring agent.
[0035] S2. Add 14g of polyvinylidene fluoride, 7g of 1,8-diazabicyclo(5,4,0)-7-undecene, and 120g of N,N-dimethylacetamide to a four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. After turning on the mechanical stirrer, raise the temperature of the system to 60℃ and react at 60℃ for 16h. After the reaction is completed, filter the mixture and pour the filtrate into deionized water to precipitate. Then filter out the precipitate and wash it with anhydrous ethanol and deionized water in sequence, and then dry it to obtain polyvinylidene fluoride with double bonds.
[0036] S3. Dissolve 3g of UV-curing agent, 12g of polyvinylidene fluoride with double bonds, and 0.3g of 2-hydroxy-2-methylphenylacetone in 120g of N,N-dimethylacetamide. Cast the solution onto a polytetrafluoroethylene (PTFE) plate to form a film. After drying, test the film under UV light intensity of 300mW / cm². 2 Modified polyvinylidene fluoride was obtained by curing and crosslinking under the specified conditions for 40 minutes.
[0037] Example 2
[0038] A modified polyvinylidene fluoride adhesive is prepared by the following steps:
[0039] S1. Under nitrogen protection, 13g of 2,4-dihydroxy-6-methylpyrimidine, 24.9g of 3-mercaptopropionic acid, and 0.9g of p-toluenesulfonic acid were mixed in a four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and water separator. After turning on the mechanical stirrer, the system temperature was raised to 85℃ and reacted at 85℃ for 7 hours. During the reaction, the water produced was continuously separated. After the reaction was completed, the crude product was washed with deionized water and dried to obtain a photocuring agent.
[0040] S2. Add 16g of polyvinylidene fluoride, 9.5g of 1,8-diazabicyclo(5,4,0)-7-undecene, and 180g of N,N-dimethylacetamide to a four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. After turning on the mechanical stirrer, raise the temperature of the system to 70℃ and react at 70℃ for 14h. After the reaction is completed, filter and pour the filtrate into deionized water to precipitate. Then filter out the precipitate and wash it with anhydrous ethanol and deionized water in sequence, and then dry it to obtain polyvinylidene fluoride with double bonds.
[0041] S3. Dissolve 3.5g of UV-curing agent, 14g of polyvinylidene fluoride with double bonds, and 0.45g of 1-hydroxycyclohexylphenyl ketone in 180g of N,N-dimethylacetamide. Cast the solution onto a polytetrafluoroethylene (PTFE) plate to form a film. After drying, test the film under UV light intensity of 100mW / cm². 2 Modified polyvinylidene fluoride was obtained by curing and crosslinking under the specified conditions for 80 minutes.
[0042] Example 3
[0043] A modified polyvinylidene fluoride adhesive is prepared by the following steps:
[0044] S1. Under nitrogen protection, 14g of 2,4-dihydroxy-6-methylpyrimidine, 26.5g of 3-mercaptopropionic acid, and 1.2g of p-toluenesulfonic acid were mixed in a four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and water separator. After turning on the mechanical stirrer, the system temperature was raised to 90℃ and reacted at 90℃ for 6 hours. During the reaction, the water produced was continuously separated. After the reaction was completed, the crude product was washed with deionized water and dried to obtain a photocuring agent.
[0045] S2. Add 18g of polyvinylidene fluoride, 12g of 1,8-diazabicyclo(5,4,0)-7-undecene, and 240g of N,N-dimethylacetamide to a four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. After turning on the mechanical stirrer, raise the temperature of the system to 80℃ and react at 80℃ for 12h. After the reaction is completed, filter the mixture and pour the filtrate into deionized water to precipitate. Then filter out the precipitate and wash it with anhydrous ethanol and deionized water in sequence, and then dry it to obtain polyvinylidene fluoride with double bonds.
[0046] S3. Dissolve 4g of UV-curing agent, 16g of polyvinylidene fluoride with double bonds, and 0.6g of benzoyl dimethyl ketal in 240g of N,N-dimethylacetamide. Cast the solution onto a polytetrafluoroethylene (PTFE) plate, and after drying, test it under UV light intensity of 200mW / cm². 2 Modified polyvinylidene fluoride was obtained by curing and crosslinking under the specified conditions for 60 minutes.
[0047] Experimental Example 1
[0048] The modified polyvinylidene fluoride obtained in Examples 1-3 was cut into strips of 30×100mm. Unmodified polyvinylidene fluoride served as a blank control. Stress-strain tests were performed on the samples of each component using a universal testing machine to test the yield strength and elongation at break of each component. The test results are shown in Table 1.
[0049] Table 1
[0050] project Yield strength / MPa Elongation at break / % Example 1 35.84 41.7 Example 2 35.32 40.2 Example 3 34.67 38.4 Blank control 20.32 12.3
[0051] As can be seen from Table 1, the modified polyvinylidene fluoride in this invention has a much better elongation at break and yield strength than the unmodified polyvinylidene fluoride, indicating that the modified polyvinylidene fluoride of this invention has better toughness and deformation recovery ability, and can better cope with the volume change of the cathode material during the charging and discharging process.
[0052] Example 4
[0053] A combined energy storage battery positive electrode includes a current collector and a conductive agent, an active material, and a binder on the surface of the current collector;
[0054] The current collector is aluminum foil, the conductive agent is acetylene black, the active material is lithium iron phosphate, and the binder is the modified polyvinylidene fluoride obtained in Example 1.
[0055] In this embodiment, the mass ratio of active material, conductive agent, and binder is 91:4:5.
[0056] A method for preparing the positive electrode of a combined energy storage battery includes the following steps:
[0057] The conductive agent, active material and binder are dissolved in N,N-dimethylacetamide and coated onto the surface of the current collector. Then, the solvent is removed by drying at 130°C to obtain the positive electrode of the combined energy storage battery.
[0058] Example 5
[0059] A combined energy storage battery positive electrode includes a current collector and a conductive agent, an active material, and a binder on the surface of the current collector;
[0060] The current collector is aluminum foil, the conductive agent is graphene, the active material is lithium manganese phosphate, and the binder is the modified polyvinylidene fluoride obtained in Example 2.
[0061] In this embodiment, the mass ratio of active material, conductive agent, and binder is 93:3:4.
[0062] A method for preparing the positive electrode of a combined energy storage battery includes the following steps:
[0063] The conductive agent, active material, and binder are dissolved in N,N-dimethylacetamide and coated onto the surface of the current collector. The solvent is then removed by drying at 150°C to obtain the positive electrode of the combined energy storage battery.
[0064] Example 6
[0065] A combined energy storage battery positive electrode includes a current collector and a conductive agent, an active material, and a binder on the surface of the current collector;
[0066] The current collector is aluminum foam, the conductive agent is carbon nanotubes, the active material is lithium vanadium phosphate, and the binder is the modified polyvinylidene fluoride obtained in Example 3.
[0067] In this embodiment, the mass ratio of active material, conductive agent, and binder is 95:2:3.
[0068] A method for preparing the positive electrode of a combined energy storage battery includes the following steps:
[0069] The conductive agent, active material and binder are dissolved in N-methylpyrrolidone and coated onto the surface of the current collector. Then, the solvent is removed by drying at 170°C to obtain the positive electrode of the combined energy storage battery.
[0070] Comparative Example 1
[0071] A combined energy storage battery positive electrode includes a current collector and a conductive agent, an active material, and a binder on the surface of the current collector;
[0072] The current collector is aluminum foam, the conductive agent is carbon nanotubes, the active material is lithium vanadium phosphate, and the binder is polyvinylidene fluoride.
[0073] In this embodiment, the mass ratio of active material, conductive agent, and binder is 95:2:3.
[0074] A method for preparing the positive electrode of a combined energy storage battery includes the following steps:
[0075] The conductive agent, active material and binder are dissolved in N-methylpyrrolidone and coated onto the surface of the current collector. Then, the solvent is removed by drying at 170°C to obtain the positive electrode of the combined energy storage battery.
[0076] Experiment Example 2
[0077] Using graphite as the negative electrode and the components from Examples 4-6 and Comparative Example 1 as the positive electrode, batteries were assembled by injecting electrolyte (the mass fraction of each raw material in the electrolyte was ethylene carbonate: dimethyl carbonate: lithium hexafluorophosphate: propanesulfonate lactone = 25:60:12:3) into a glove box protected by inert gas. The initial charge-discharge efficiency and capacity retention after 500 cycles of each component battery were tested. The test results are shown in Table 2.
[0078] Table 2
[0079]
[0080]
[0081] As can be seen from Table 2, the battery assembled using the modified polyvinylidene fluoride of the present invention has better overall charge-discharge efficiency and cycle capacity retention.
[0082] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.
Claims
1. A combined energy storage battery positive electrode, characterized in that, It includes current collectors and conductive agents, active substances and binders on the surface of current collectors; The binder is modified polyvinylidene fluoride (PVDF). The modification method of PVDF includes the following steps: mixing 2,4-dihydroxy-6-methylpyrimidine, 3-mercaptopropionic acid, and p-toluenesulfonic acid, and reacting them at a controlled temperature of 80-90°C to obtain a photocurable agent; dissolving PVDF and 1,8-diazabicyclo(5,4,0)-7-undecene in N,N-dimethylformamide and reacting them at a controlled temperature of 60-80°C to obtain PVDF with double bonds; finally, dissolving the photocurable agent, PVDF with double bonds, and initiator in N,N-dimethylacetamide, casting into a film, drying it, and then photocuring and crosslinking it to obtain modified PVDF. The initiator is one of 2-hydroxy-2-methylphenylacetone, 1-hydroxycyclohexylphenyl ketone, or benzoyladium dimethyl ketal; the photocuring and crosslinking conditions are curing and crosslinking for 40-80 min under ultraviolet light intensity of 100-300 mW / cm²; the mass ratio of 2,4-dihydroxy-6-methylpyrimidine, 3-mercaptopropionic acid, and p-toluenesulfonic acid is 12.6-14:23.3-26.5:0.6-1.2; the mass ratio of polyvinylidene fluoride and 1,8-diazabicyclo(5,4,0)-7-undecene is 14-18:7-12; and the mass ratio of photocuring agent, polyvinylidene fluoride with double bonds, and initiator is 3-4:12-16:0.3-0.
6.
2. The positive electrode of a combined energy storage battery according to claim 1, characterized in that, The current collector is either aluminum foil or aluminum foam.
3. The positive electrode of a combined energy storage battery according to claim 1, characterized in that, The conductive agent is any one or a mixture of acetylene black, graphene, and carbon nanotubes.
4. The positive electrode of a combined energy storage battery according to claim 1, characterized in that, The active material is a lithium salt, including at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese phosphate, and lithium vanadium phosphate.
5. A method for preparing the positive electrode of a combined energy storage battery as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The conductive agent, active material and binder are dissolved in an organic solvent and coated onto the surface of the current collector. After drying to remove the solvent, the positive electrode of the combined energy storage battery is obtained.
6. The method for preparing a combined energy storage battery positive electrode according to claim 5, characterized in that, The mass ratio of active material, conductive agent, and binder is 91-95:2-4:3-5.
7. The method for preparing a combined energy storage battery positive electrode according to claim 5, characterized in that, The organic solvent is one of N-methylpyrrolidone and N,N-dimethylacetamide.
8. The method for preparing a combined energy storage battery positive electrode according to claim 5, characterized in that, The drying temperature is 130–170℃.