High-strength pole piece and battery comprising same
By using aramid binders to form high-strength electrodes, the problem of insufficient mechanical strength and stability of traditional binders in batteries is solved, achieving high-strength electrode peel strength and electronic conductivity, and improving the cycle stability and safety of the battery.
Patent Information
- Application Number
- CN202510702546.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-28
- Publication Date
- 2025-10-17
AI Technical Summary
Existing binders have low mechanical strength, narrow electrochemical window, and poor environmental tolerance, making it difficult to adapt to the volume expansion of silicon-based anodes and the stability requirements of high-voltage cathodes. This leads to electrode pulverization and failure, affecting battery performance and safety.
Using aramid as a binder, and utilizing the hydrogen bonds and coordination bonds between amide bonds and current collectors and active materials, combined with the π-π stacking effect of benzene rings and the physical interlocking effect of nanofibers, a high-strength electrode structure is formed, which enhances interfacial bonding and electronic conductivity, and suppresses volume expansion.
The electrode has extremely high peel strength and electronic conductivity, which significantly improves the long-cycle stability and safety of the battery and extends its service life.
Smart Images
Figure CN120809727A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of battery materials, and in particular to a high-strength pole piece and a battery comprising the pole piece. BACKGROUND
[0002] With the acceleration of the transformation of global energy structure to renewable energy, the development of efficient and safe energy storage technology has become an effective means to solve the problem of energy intermittency. Lithium batteries dominate in the fields of consumer electronics, electric vehicles and grid energy storage due to their high energy density and mature industrialization foundation. As the "invisible framework" of the electrode structure of the battery, the binder is a key material that affects the energy density, cycle life and safety of the battery, and its importance is increasingly prominent with the development of battery technology to high specific energy, extreme working conditions and new systems.
[0003] Although the current mainstream binders (such as PVDF, CMC / SBR) can meet the basic needs of batteries, their low mechanical strength, narrow electrochemical window and poor environmental tolerance have become a bottleneck restricting the breakthrough of battery performance. For example, the traditional binder is difficult to adapt to the 300% volume expansion of silicon-based anodes, resulting in electrode pulverization failure. In addition, with the rise of high-voltage cathodes (such as lithium-rich manganese-based and lithium nickel manganese oxide) and solid-state batteries, the binder needs to remain stable in high voltage above 4.8V or rigid interface. In terms of safety, the anti-swelling properties of the binder can reduce the interface degradation caused by electrolyte infiltration, and the flame retardant properties can further delay the spread of thermal runaway, opening up a new path for the safety design of power batteries. The application of advanced binders can improve the energy density of batteries, reduce costs, and support the needs of fast charging, wide temperature range and other scenarios. Therefore, binder innovation is not only a breakthrough point in materials science, but also an important engine for the development of lithium battery industry, which will have a profound impact on the energy revolution process in the fields of new energy vehicles, energy storage power stations and even aerospace.
[0004] Traditional binders such as PVDF achieve binding through intermolecular van der Waals forces, and some biomass materials such as CMC, SBR and PAA achieve binding through physical cross-linking network and hydrogen bonds due to their rich functional groups and unique structure. However, the binding effect of these binders is relatively weak and they will swell in electrolyte, affecting the binding strength. Further, they cannot effectively alleviate the volume change of active materials during charging and discharging, causing pole piece cracking and electrode material shedding during long cycle of the battery. Therefore, it is urgent to develop a binder with good binding, low swelling rate and effective alleviation of active material volume expansion. SUMMARY
[0005] The present application aims to at least partially solve one of the problems of the prior art. To this end, it is an object of the present application to propose a high-strength pole piece and a battery comprising the pole piece.
[0006] In a first aspect, the present application provides a high-strength electrode sheet, comprising a current collector and an active layer, wherein the active layer comprises a binder, and the binder comprises aramid fiber.
[0007] According to the high-strength electrode sheet provided by the present application, aramid fiber is used as the binder, and the aramid fiber contains both amide bonds (-NH-CO-) and benzene rings. The amide bonds form hydrogen bonds with the hydroxyl groups (-OH) on the surface oxide layer of the current collector, thereby enhancing the interfacial bonding. Meanwhile, the amide bonds can also form multi-point anchoring with the oxygen atoms on the surface of the oxide positive active material or the hydroxyl groups of the negative active material through hydrogen bonds. In addition, the amide bonds can act as ligands to form coordination bonds with metal ions in the active layer. By forming hydrogen bonds or coordination bonds, the peeling strength between the active layer and the current collector is improved. The benzene ring structure has a π-π stacking effect, specifically, the benzene ring and the graphitized carbon layer on the surface of the carbon-based conductive agent or the current collector occur π-π stacking, thereby improving the electron conductivity, and the π electron cloud of the benzene ring participates in the coordination of metal ions as a weak ligand. As a nanofiber, aramid fiber has a physical interlocking effect. The aramid nanofiber has a high aspect ratio and can penetrate the porous structure of the active material or wrap the active material. After solidification, a three-dimensional mechanical anchoring network is formed, thereby inhibiting volume expansion. Moreover, the elastic modulus of aramid fiber is much higher than that of traditional binders, and can constrain the displacement of active material particles. Thus, the electrode sheet provided by the present application has small influence of electrolyte, the binder has extremely low swelling rate, the connection between the current collector and the active layer is strong, the electrode sheet has extremely high peeling strength, and the electrode sheet has strong electron conductivity, low volume expansion, long cycle stability and safety.
[0008] According to the high-strength electrode sheet provided by the present application, the mass fraction of the aramid fiber is 0.1%-4%, preferably 0.5%-3%, based on the total mass of the active layer. For example, the mass fraction of the aramid fiber is 0.1%, 0.5%, 1%, 2%, 3%, 4%, or a range between any two of the above-mentioned values.
[0009] According to the high-strength electrode sheet provided by the present application, the aramid fiber is selected from one or more of meta-aramid fiber, para-aramid fiber, meta-aramid fibrid, para-aramid fibrid, meta-aramid pulp, para-aramid pulp, meta-aramid polymer, para-aramid polymer, and aramid fiber derivative.
[0010] According to the high-strength electrode sheet provided by the present application, the molecular weight of the aramid fiber is 5000-2000000. For example, the molecular weight of the aramid fiber is 5000, 50000, 500000, 1000000, 2000000, or a range between any two of the above-mentioned values.
[0011] According to the high-strength electrode sheet provided by the present application, the active layer further comprises an active material and a conductive agent.
[0012] The active material is a positive electrode active material or a negative electrode active material.
[0013] The mass percentage of the conductive agent in the total mass of the active layer is 0.1%-4%.
[0014] The positive electrode active material is at least one selected from a ferrous phosphate-based material, a ferrous vitriol-based material, a nickel-cobalt-manganese-based material, a nickel-cobalt-aluminum-based material, a lithium-rich manganese-based material, a manganate-based material, a cobaltate-based material, a nickel manganate-based material, and a sulfur-based material, and preferably the nickel-cobalt-manganese-based material.
[0015] In some embodiments of the present application, the active layer comprises a positive electrode active material, a conductive agent, and a aramid binder, the positive electrode active material is at least one selected from a ferrous phosphate-based material, a ferrous vitriol-based material, a nickel-cobalt-manganese-based material, a nickel-cobalt-aluminum-based material, a lithium-rich manganese-based material, a manganate-based material, a cobaltate-based material, a nickel manganate-based material, and a sulfur-based material, and the mass percentage of aramid in the total mass of the active layer is 0.1%-3%.
[0016] The negative electrode active material is at least one selected from a graphite-based material, a titanate-based material, a silicon-based material, a tin-based material, an antimony-based material, and a phosphorus-based material, and preferably the silicon-based material.
[0017] In some embodiments of the present application, the active layer comprises a negative electrode active material, a conductive agent, and a aramid binder, the negative electrode active material is at least one selected from a graphite-based material, a titanate-based material, a silicon-based material, a tin-based material, an antimony-based material, and a phosphorus-based material, and the mass percentage of aramid in the total mass of the active layer is 0.5%-4%.
[0018] The conductive agent is at least one selected from carbon nanotubes, graphene, carbon fibers, conductive carbon black, Ketjen black, acetylene black, Super P, and conductive graphite.
[0019] The current collector is selected from a copper current collector, an aluminum current collector, a carbon-coated copper current collector, a carbon-coated aluminum current collector, or a composite current collector, and preferably the copper current collector or the aluminum current collector.
[0020] The thickness of the active layer on one side of the current collector is 30-200 μm.
[0021] In some embodiments of the present application, the preparation process of the above-mentioned electrode plate comprises: uniformly mixing the active material, the conductive agent, and the binder in an organic solvent, then coating on the surface of the current collector, and drying, rolling, and cutting to obtain.
[0022] In a second aspect, the present application provides a battery comprising the above-mentioned electrode tab. Thus, the battery has long cycle stability and long service life.
[0023] In some embodiments of the present application, the battery comprises a positive electrode tab, a separator and a negative electrode tab, wherein the positive electrode tab uses the above-mentioned high-strength electrode tab.
[0024] In some embodiments of the present application, the battery comprises a positive electrode tab, a separator and a negative electrode tab, wherein the negative electrode tab uses the above-mentioned high-strength electrode tab.
[0025] Preferably, the positive electrode tab of the battery and the negative electrode tab of the battery both use the above-mentioned high-strength electrode tab.
[0026] In some embodiments of the present application, the battery comprises a liquid ion battery, a semi-solid ion battery or a solid ion battery.
[0027] The present application has at least the following beneficial effects: The high-strength electrode tab of the present application uses aramid as the binder, fully utilizes the multi-level chemical bond synergy (hydrogen bond network, complexation, π-π stacking, etc.), nanofiber physical interlocking effect, mechanical property advantages (high modulus, etc.) and other characteristics of aramid, breaks through the performance bottleneck of the existing battery electrode tab binder, makes the electrode tab have excellent peel strength, and the battery prepared using the electrode tab has long cycle stability, significantly improves the safety and service life of the battery. BRIEF DESCRIPTION OF DRAWINGS
[0028] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without any creative effort.
[0029] Figure 1 is the peel strength test photo of the negative electrode tab of Example 1 of the present application; Figure 2 is the cycle performance test result of the battery of Example 1 of the present application; Figure 3 is the peel strength test photo of the negative electrode tab of Example 2 of the present application; Figure 4 is the cycle performance test result of the battery of Example 2 of the present application; Figure 5 is the cycle performance test result of the battery of Example 3 of the present application; Figure 6 is the peel strength test photo of the negative electrode tab of Comparative Example 1 of the present application; Figure 7 is the cycle performance test result of the battery of Invention Comparative Example 1; Figure 8 is the cycle performance test result of the battery of Invention Comparative Example 2. DETAILED DESCRIPTION
[0030] All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without creative labor fall within the scope of protection of the present application. The present application is described below with reference to specific embodiments, and it should be noted that these embodiments are merely descriptive and do not limit the present application in any way.
[0031] Example 1 (1) The present embodiment provides a negative electrode sheet, and the specific preparation process is as follows: The silicon-based active material, carbon nanotube conductive agent and meta-aramid fiber binder are mixed uniformly in an organic solvent to obtain a negative electrode slurry. The negative electrode slurry is coated on a copper current collector, and then dried and rolled to prepare a negative electrode sheet. The negative electrode sheet includes a copper current collector and a negative electrode active layer. In the negative electrode active layer, the mass fraction of meta-aramid fiber (molecular weight 500000) is 1%, and the mass fraction of conductive agent is 1.5%. The thickness of the negative electrode active layer on one side of the copper current collector is 53 μm.
[0032] (2) The present embodiment provides a battery, and the specific process is as follows: The negative electrode sheet obtained in step (1) and a high-nickel ternary positive electrode sheet (PVDF as binder) are assembled into a lithium ion secondary battery.
[0033] The peel strength of the negative electrode sheet of Example 1 is determined, and the specific test method is as follows: test according to GB / T 2792-2014 "Test method for peel strength of adhesive tape".
[0034] The specific test photos are as shown in Figure 1 The average peel force of the selected 5 negative electrode sheets is 28.59 N, and the average peel strength is 2.40 N / mm.
[0035] The high peeling strength of the negative electrode sheet is caused by the following three effects: (1) the polar effect of the amide bond: the amide bond (-NH-CO-) of the aramid binder forms a hydrogen bond with the hydroxyl group of the copper current collector surface oxide layer, enhancing the interface bonding; the amide bond of the aramid binder and the hydroxyl group of the silicon negative active material form a multi-point anchoring through a hydrogen bond; the amide bond of the aramid binder acts as a ligand to form a coordination bond with the oxidized copper ions on the surface of the copper current collector. (2) The π-π stacking effect of the aromatic ring structure: the benzene ring of the aramid binder occurs π-π stacking with the carbon nanotube conductive agent, improving the electron conductivity; the π electron cloud of the benzene ring of the aramid binder acts as a weak ligand to coordinate with the oxidized copper ions on the surface of the copper current collector. (3) The physical interlocking effect of the nanofiber: the aramid nanofiber has a high aspect ratio, wraps the silicon active material, and forms a three-dimensional mechanical anchoring network after curing, thereby inhibiting the volume expansion; the elastic modulus of the aramid is much higher than that of the traditional binder, which can constrain the displacement of the active material particles.
[0036] The performance of the battery provided in Example 1 was determined, and the specific method was as follows: the standard cycle life in 6.4 of GB / T 31484-2015 “Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles” was used for testing.
[0037] The cycle performance test results of the battery of Example 1 can be referred to Figure 2 , and it can be known that the capacity retention rate of the battery after 500 cycles is 83.9%.
[0038] Example 2 (1) The negative electrode sheet provided in this embodiment is different from that of Example 1 only in the specific preparation process. In the negative active layer, the mass fraction of the meta-aramid fiber is 2%.
[0039] (2) The battery provided in this embodiment has the same specific preparation process as that of Example 1.
[0040] The peeling strength of the negative electrode sheet of Example 2 was determined, and the specific test method was the same as that of Example 1.
[0041] The specific test photos are as Figure 3 . The average peeling force of the selected five negative electrode sheets is 29.20 N, and the average peeling strength is 2.41 N / mm.
[0042] The performance of the battery provided in Example 2 was determined, and the specific method was the same as that of Example 1.
[0043] The cycle performance test results of the battery of Example 2 can be referred to Figure 4 , and it can be known that the capacity retention rate of the battery after 500 cycles is 76.8%.
[0044] Example 3 (1) The embodiment provides a positive electrode tab, and a specific preparation process is as follows: The high-nickel ternary active material, the conductive carbon black conductive agent and the para-aramid fiber binder are uniformly mixed in an organic solvent to obtain a positive electrode slurry. The positive electrode slurry is coated on an aluminum current collector, and then dried and rolled to prepare a positive electrode tab. The positive electrode tab comprises an aluminum current collector and a positive electrode active layer. The mass percentage of para-aramid fiber (molecular weight 80000) in the positive electrode active layer is 0.8%, and the mass percentage of the conductive agent is 1%. The thickness of the positive electrode active layer on one side of the aluminum current collector is 86 μm.
[0045] (2) The embodiment provides a battery, and the specific process is as follows: The positive electrode tab obtained in step (1) and a silicon oxide negative electrode tab (CMC / SBR as a binder) are assembled into a lithium ion secondary battery.
[0046] The peeling strength of the positive electrode tab of Example 3 is determined, and the specific test method is the same as that of Example 1.
[0047] The average peeling force of the selected 5 positive electrode tabs is 153 N, and the average peeling strength is 12.83 N / mm.
[0048] The high peeling strength of the positive electrode tab is caused by the following three effects: (1) the polar effect of the amide bond: the amide bond (-NH-CO-) of the aramid binder can form a hydrogen bond with the hydroxyl group of the oxide layer on the surface of the aluminum current collector, thereby enhancing the interface bonding; the amide bond of the aramid binder and the oxygen atom on the surface of the high-nickel ternary material form a multi-point anchoring through a hydrogen bond; the amide bond of the aramid binder acts as a ligand to form a coordination bond with Ni, Co and Mn metal ions; the amide bond of the aramid binder acts as a ligand to form a coordination bond with the aluminum ions on the surface of the aluminum current collector. (2) The π-π stacking effect of the aromatic ring structure: the π-π stacking of the benzene ring of the aramid binder and the conductive carbon black conductive agent improves the electronic conductivity; the π electron cloud of the benzene ring of the aramid binder acts as a weak ligand to coordinate with the aluminum ions on the surface of the aluminum current collector. (3) The physical interlocking effect of the nanofiber: the aramid nanofiber has a high aspect ratio, wraps the high-nickel ternary active material, and forms a three-dimensional mechanical anchoring network after solidification, thereby inhibiting the volume expansion; the elastic modulus of the aramid is much higher than that of the traditional binder, and can constrain the displacement of the active material particles.
[0049] The performance of the battery provided in Example 3 is determined, and the specific method is the same as that of Example 1.
[0050] The cycle performance test results of the battery of Example 3 can be referred to Figure 5 It can be known that the capacity retention rate of the battery is 78.8% after 500 cycles.
[0051] Comparative Example 1 (1) The present comparative example provides a negative electrode sheet, and the difference between the specific preparation process and Example 1 is only that: In the negative active layer, the binder used in Comparative Example 1 is sodium carboxymethyl cellulose and butadiene rubber, and the mass ratio of the two is 1:2.
[0052] (2) The present comparative example provides a battery, and the specific preparation process is the same as Example 1.
[0053] The peel strength of the negative electrode sheet of Comparative Example 1 is determined, and the specific test method is the same as Example 1.
[0054] The specific test photos are as follows: Figure 6 The average peel force of the selected 5 negative electrode sheets is 12.43 N, and the average peel strength is 0.95 N / mm.
[0055] The performance of the battery provided by Comparative Example 1 is determined, and the specific method is the same as Example 1.
[0056] The cycle performance test results of the battery of Comparative Example 1 can be referred to Figure 7 , and it can be known that the capacity retention rate of the battery is 70.1% after 500 cycles.
[0057] Comparative Example 2 (1) The present comparative example provides a positive electrode sheet, and the difference between the specific preparation process and Example 3 is only that: In the positive active layer, the binder used in Comparative Example 2 is PVDF.
[0058] (2) The present comparative example provides a battery, and the specific preparation process is the same as Example 3.
[0059] The peel strength of the positive electrode sheet of Comparative Example 2 is determined, and the specific test method is the same as Example 1.
[0060] The average peel force of the selected 5 positive electrode sheets is 63.68 N, and the average peel strength is 5.22 N / mm.
[0061] The performance of the battery provided by Comparative Example 2 is determined, and the specific method is the same as Example 1.
[0062] The cycle performance test results of the battery of Comparative Example 2 can be referred to Figure 8 , and it can be known that the capacity retention rate of the battery is 64.34% after 371 cycles.
[0063] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A high-strength pole piece, comprising a current collector and an active layer, wherein the active layer comprises a binder, characterized in that: The binder includes aramid.
2. The high-strength pole piece according to claim 1, characterized in that: Based on the total mass of the active layer, the mass of the aramid fiber accounts for 0.1%-4%.
3. The high-strength pole piece according to claim 1, characterized in that: The aramid is selected from one or more of meta-aramid fiber, para-aramid fiber, meta-aramid fibrid, para-aramid fibrid, meta-aramid pulp, para-aramid pulp, meta-aramid polymer, para-aramid polymer, and aramid derivatives.
4. The high-strength pole piece according to claim 1, characterized in that: The molecular weight of the aramid is 5,000-2,000,000.
5. The high-strength pole piece according to any one of claims 1 to 4, characterized in that: The active layer further includes an active material and a conductive agent.
6. The high-strength pole piece according to claim 5, characterized in that: The active material is a positive electrode active material or a negative electrode active material; And / or, based on the total mass of the active layer, the mass of the conductive agent accounts for 0.1% to 4%.
7. The high-strength pole piece according to claim 6, characterized in that: The positive electrode active material is selected from at least one of ferrous phosphate-based materials, vanadium phosphate-based materials, nickel-cobalt-manganese-based materials, nickel-cobalt-aluminum-based materials, lithium-rich manganese-based materials, manganate-based materials, cobalt-based materials, nickel-manganate-based materials, and sulfur-based materials, preferably nickel-cobalt-manganese-based materials; And / or, the negative electrode active material is selected from at least one of graphite-based materials, titanate-based materials, silicon-based materials, tin-based materials, antimony-based materials, and phosphorus-based materials, preferably silicon-based materials; And / or, the conductive agent is selected from at least one of carbon nanotubes, graphene, carbon fiber, conductive carbon black, Ketjen black, acetylene black, SuperP, and conductive graphite.
8. The high-strength pole piece according to any one of claims 1 to 4, characterized in that: The current collector is selected from a copper current collector, an aluminum current collector, a carbon-coated copper current collector, a carbon-coated aluminum current collector or a composite current collector, preferably a copper current collector or an aluminum current collector.
9. A battery, characterized in that: The invention comprises the high-strength pole piece as described in any one of claims 1 to 8.
10. The battery according to claim 9, characterized in that: The battery includes a liquid ion battery, a semi-solid ion battery or a solid ion battery.