High-temperature-resistant lithium supplementing positive electrode material and preparation method thereof

Abstract

The application discloses a high-temperature-resistant lithium-supplementing positive electrode material and a preparation method thereof. The high-temperature-resistant lithium-supplementing positive electrode material comprises the following raw material components in parts by weight: 80-100 parts of a positive electrode active material, 5-13 parts of a conductive agent, 5-10 parts of a binder, 5-8 parts of a stabilizing agent and 50-60 parts of a solvent; the binder is a compounded composition of polyvinylidene fluoride and polyacrylamide; and the stabilizing agent comprises hydroxyapatite nanowires treated by a macromolecular silane coupling agent. The high-temperature-resistant lithium-supplementing positive electrode material can improve the heat resistance of a battery and maintain the stability of the electrochemical performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a high-temperature resistant lithium-replenishing cathode material and its preparation method. Background Technology

[0002] Lithium-ion batteries are among the most commonly used commercially available batteries, boasting advantages such as high energy density, light weight, large capacity, and short charging time. They are widely used in electric vehicles, smartphones, laptops, and other devices. A lithium-ion battery typically consists of a positive electrode, a separator, a negative electrode, an organic electrolyte, and a battery casing. The positive electrode generally comprises active materials, conductive agents, and a binder. The binder, besides binding the active materials and conductive agents together, also plays a role in inhibiting electrode volume expansion and preventing side reactions between the active materials and the electrolyte. However, current binders have relatively poor heat resistance. When the battery's internal temperature rises during prolonged use, the binder's adhesion tends to deteriorate. After repeated charge-discharge cycles, problems such as active material failure and electrode volume expansion can easily occur, leading to shortened battery life and reduced capacity.

[0003] Therefore, in order to address the aforementioned technical issues, it is necessary to further improve the composition of the cathode in lithium-ion batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature resistant lithium-replenishing cathode material and its preparation method, which can effectively improve the thermal stability and electrochemical performance of the battery.

[0005] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0006] A high-temperature resistant lithium-supplementing cathode material comprises the following raw material components in parts by weight: 80-100 parts of cathode active material, 5-13 parts of conductive agent, 5-10 parts of binder, 5-8 parts of stabilizer, and 50-60 parts of solvent.

[0007] The adhesive is a compound composition of polyvinylidene fluoride and polyacrylamide;

[0008] The stabilizer comprises hydroxyapatite nanowires treated with macromolecular silane coupling agents.

[0009] In one or more embodiments of the present invention, the macromolecular silane coupling agent is dodecyltrimethoxysilane, hexadecyltrimethoxysilane, or trimethoxy-terminated polydimethylsiloxane.

[0010] In one or more embodiments of the present invention, the hydroxyapatite nanowires have a length of 100 μm-200 μm and a diameter of 10 nm-100 nm.

[0011] In one or more embodiments of the present invention, the stabilizer further includes zirconium oxide treated with a small molecule silane coupling agent and polydopamine-coated spherical hydroxyapatite, wherein the mass ratio of the hydroxyapatite nanowires, spherical hydroxyapatite and zirconium oxide is (5-6):(2-3):1.

[0012] In one or more embodiments of the present invention, the spherical hydroxyapatite has a size of 8μm-12μm, and the zirconium oxide has a particle size of 0.5μm-3μm.

[0013] In one or more embodiments of the present invention, the small molecule silane coupling agent is 3-aminopropyltriethoxysilane or glycidoxypropyltrimethoxysilane.

[0014] In one or more embodiments of the present invention, the mass ratio of polyvinylidene fluoride to polyacrylamide is (2-3):1.

[0015] In one or more embodiments of the present invention, the positive electrode active material includes a lithium-rich manganese-based material and at least one of lithium squaric acid, lithium oxalate, lithium iron phosphate, and lithium manganese iron phosphate.

[0016] In one or more embodiments of the present invention, the conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and carbon fiber.

[0017] The technical solution provided by a specific embodiment of the present invention is as follows:

[0018] A method for preparing the above-mentioned high-temperature resistant lithium-replenishing cathode material involves taking each raw material component according to the specified ratio, mixing them evenly, and then obtaining the high-temperature resistant lithium-replenishing cathode material.

[0019] Compared with existing technologies, this invention utilizes hydroxyapatite nanowires treated with macromolecular silane coupling agents as stabilizers, which effectively improves the high-temperature resistance of the cathode material and ensures that the battery has superior electrochemical performance. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention are clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0021] A specific embodiment of the present invention provides a high-temperature resistant lithium-supplementing cathode material, comprising the following components by weight: 80-100 parts of cathode active material, 5-13 parts of conductive agent, 5-10 parts of binder, 5-8 parts of stabilizer, and 50-60 parts of solvent.

[0022] Furthermore, the positive electrode active material includes lithium-rich manganese-based materials and at least one of lithium squartz, lithium oxalate, lithium iron phosphate, and lithium manganese iron phosphate. Lithium-rich manganese-based materials have the advantages of high specific capacity and high voltage platform; when used in combination with lithium iron phosphate or lithium manganese iron phosphate, they can significantly improve the battery's cycle performance. Combining lithium-rich manganese-based materials with lithium squartz or with lithium oxalate can optimize the electrochemical performance of the positive electrode material at high temperatures, increase energy density, and maintain the structural stability of the positive electrode material.

[0023] Furthermore, the conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and carbon fiber. These types of conductive agents possess excellent conductivity, can form an effective conductive network, reduce the impedance of the positive electrode material, and improve the charge and discharge efficiency of the battery.

[0024] Furthermore, the binder is a composite composition of polyvinylidene fluoride (PVDF) and polyacrylamide (PAF), with a mass ratio of PVDF to PAF of (2-3):1. PVDF exhibits excellent oxidation resistance and chemical corrosion resistance, maintaining stability under high voltage conditions, but its adhesive strength is slightly weaker. PAF, on the other hand, possesses excellent adhesive strength and helps reduce the volume expansion of the positive electrode material, improving the battery's cycle life, but its thermal stability is slightly weaker than that of PVDF. Therefore, the composite use of PVDF and PAF is beneficial for forming a more stable electrode structure, effectively improving the battery's cycle performance and capacity retention.

[0025] Furthermore, the stabilizer includes hydroxyapatite nanowires treated with a macromolecular silane coupling agent. The hydroxyapatite nanowires have a length of 100 μm to 200 μm and a diameter of 10 nm to 100 nm. The macromolecular silane coupling agent is dodecyltrimethoxysilane, hexadecyltrimethoxysilane, or trimethoxy-terminated polydimethylsiloxane. Preferably, the macromolecular silane coupling agent is hexadecyltrimethoxysilane or trimethoxy-terminated polydimethylsiloxane.

[0026] Specifically, in cathode materials, polyacrylamide forms a network structure through molecular chain entanglement and acts as a binder through hydrogen bonding. However, this network structure is easily disrupted by rising temperatures, resulting in decreased viscosity. Therefore, this invention uses hydroxyapatite nanowires treated with macromolecular silane coupling agents as a stabilizer. First, hydroxyapatite nanowires exhibit excellent thermal stability, maintaining structural integrity even at high temperatures, reducing the likelihood of battery failure due to high temperatures. Second, the surface of hydroxyapatite nanowires is rich in hydroxyl and phosphate ions, which can promote lithium-ion transport and improve the battery's rate performance. Furthermore, hydroxyapatite nanowires can participate in the formation of the polyacrylamide network structure, further enhancing its stability.

[0027] Furthermore, macromolecular silane coupling agents can entangle with polyacrylamide molecular chains. Simultaneously, the interaction between the macromolecular silane coupling agent and polyacrylamide promotes the participation of the macromolecular silane coupling agent in the formation of the polyacrylamide network structure. The macromolecular silane coupling agent exhibits superior thermal stability, maintaining the stability of the polyacrylamide network structure and ensuring stable bonding performance. Treating hydroxyapatite nanowires with macromolecular silane coupling agents can also promote the stable existence of hydroxyapatite nanowires in the system, thereby contributing to improved battery thermal stability.

[0028] Furthermore, the stabilizers also include zirconium oxide treated with a small molecule silane coupling agent and spherical hydroxyapatite coated with polydopamine, wherein the small molecule silane coupling agent is 3-aminopropyltriethoxysilane or propylene oxide-trimethoxysilane.

[0029] Specifically, both zirconium oxide and spherical hydroxyapatite have good thermal stability. Zirconium oxide and spherical hydroxyapatite can fill the network structure in the system, increasing the density of the network structure. At the same time, zirconium oxide can optimize the particle size distribution of the cathode material, shorten the diffusion path of lithium ions, and improve the discharge specific capacity of the material.

[0030] After spherical hydroxyapatite is coated with polydopamine, the adhesive properties of polydopamine allow it to bond with the network structure within the system. Simultaneously, the short chain length of the small-molecule silane coupling agent enables it to form hydrogen bonds with the polydopamine distributed around the zirconium oxide, further enhancing the stability of the network structure and maintaining the stability of the battery's electrochemical performance. Additionally, the large-molecule silane coupling agent may also form hydrogen bonds with the polydopamine, further improving the battery's heat resistance.

[0031] Preferably, the mass ratio of hydroxyapatite nanowires, spherical hydroxyapatite, and zirconium oxide is (5-6):(2-3):1, the size of the spherical hydroxyapatite is 8μm-12μm, and the particle size of the zirconium oxide is 0.5μm-3μm. By limiting the mass ratio and size of hydroxyapatite nanowires, spherical hydroxyapatite, and zirconium oxide, the network structure in the system can be made stable, thereby improving the stability of the battery's electrochemical performance.

[0032] Furthermore, the solvent is N-methylpyrrolidone.

[0033] Another specific embodiment of the present invention provides a method for preparing the above-mentioned high-temperature resistant lithium-replenishing cathode material, wherein each raw material component is taken according to the ratio, and mixed evenly to obtain the high-temperature resistant lithium-replenishing cathode material.

[0034] The present invention will be further described in detail below with reference to specific embodiments.

[0035] In this invention, the hydroxyapatite nanowires were purchased from Suzhou Kaifa New Materials, catalog number BkZNZ2020102066-01; the spherical hydroxyapatite was purchased from Yingxin Laboratory, catalog number TX21249-25g-B; the zirconium oxide was purchased from Jinkun Zirconium Industry; and the lithium-rich manganese-based material was purchased from Suzhou Beike Nanotechnology, with a Li-type structure. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2; polyacrylamide was purchased from Weifang Baicheng Chemical, model number 85236; polyvinylidene fluoride was purchased from Dongguan Zhengtao Plastics, product number HH9010TIEQ8.

[0036] Preparation Example 1

[0037] Anhydrous ethanol and water were mixed at a volume ratio of 95:5 to prepare a mixture. Hexadecyltrimethoxysilane was added at a mass ratio of 100:0.8 to the mixture and mixed well. Then, hydroxyapatite nanowires were added at a mass ratio of 0.5:5 to hexadecyltrimethoxysilane. The mixture was reacted at 60°C for 1 hour. After the reaction was completed, the precipitate was collected by centrifugation and dried to obtain hydroxyapatite nanowires treated with macromolecular silane coupling agent.

[0038] Preparation Example 2

[0039] 3-Aminopropyltriethoxysilane and anhydrous ethanol were mixed to prepare a treatment solution with a volume concentration of 10%. The treatment solution and zirconium oxide were mixed at a liquid-solid ratio of 50 mL: 5 g and reacted. After reacting for 3 h, the solution was washed with anhydrous ethanol, centrifuged, and dried at 65 °C to obtain zirconium oxide treated with small molecule silane coupling agent.

[0040] Preparation Example 3

[0041] Spherical hydroxyapatite and Tris buffer at pH 9.0 were mixed at a liquid-to-solid ratio of 10 ml: 100 mg. Dopamine hydrochloride and Tris buffer at pH 9.0 were then mixed at a liquid-to-solid ratio of 10 ml: 100 mg. The two mixtures were mixed and stirred continuously for 3 hours. The mixture was then centrifuged, the precipitate was collected, and dried to obtain polydopamine-coated spherical hydroxyapatite.

[0042] Example 1

[0043] By weight, 50 parts of lithium-rich manganese-based material, 30 parts of lithium oxalate, 10 parts of conductive carbon black, 3.3 parts of polyvinylidene fluoride, 1.7 parts of polyacrylamide, 5 parts of hydroxyapatite nanowires treated with the macromolecular silane coupling agent in Preparation Example 1, and 50 parts of N-methylpyrrolidone were mixed to obtain a high-temperature resistant lithium-replenishing cathode material.

[0044] Example 2

[0045] By weight, 60 parts of lithium-rich manganese-based material, 32 parts of lithium oxalate, 5 parts of conductive carbon black, 7.5 parts of polyvinylidene fluoride, 2.5 parts of polyacrylamide, 8 parts of hydroxyapatite nanowires treated with the macromolecular silane coupling agent in Preparation Example 1, and 60 parts of N-methylpyrrolidone were mixed to prepare a high-temperature resistant lithium-replenishing cathode material.

[0046] Example 3

[0047] By weight, 70 parts of lithium-rich manganese-based material, 30 parts of lithium iron phosphate, 13 parts of conductive carbon black, 5.4 parts of polyvinylidene fluoride, 2.6 parts of polyacrylamide, 7 parts of hydroxyapatite nanowires treated with the macromolecular silane coupling agent in Preparation Example 1, and 56 parts of N-methylpyrrolidone were mixed to obtain a high-temperature resistant lithium-replenishing cathode material.

[0048] Example 4

[0049] By weight, 60 parts of lithium-rich manganese-based material, 32 parts of lithium oxalate, 5 parts of conductive carbon black, 7.5 parts of polyvinylidene fluoride, 2.5 parts of polyacrylamide, 8 parts of stabilizer, and 60 parts of N-methylpyrrolidone were taken. The stabilizer included the macromolecular silane coupling agent treated in Preparation Example 1, the zirconium oxide treated with the small molecule silane coupling agent in Preparation Example 2, and the polydopamine-coated spherical hydroxyapatite in Preparation Example 3, all in a mass ratio of 5:3:1. The mixture was stirred to obtain a high-temperature resistant lithium-replenishing cathode material.

[0050] Example 5

[0051] By weight, 60 parts of lithium-rich manganese-based material, 32 parts of lithium oxalate, 5 parts of conductive carbon black, 7.5 parts of polyvinylidene fluoride, 2.5 parts of polyacrylamide, 8 parts of stabilizer, and 60 parts of N-methylpyrrolidone were taken. The stabilizer included the macromolecular silane coupling agent treated in Preparation Example 1, the zirconium oxide treated with the small molecule silane coupling agent in Preparation Example 2, and the polydopamine-coated spherical hydroxyapatite in Preparation Example 3, all in a mass ratio of 5.5:2:1. The mixture was stirred to obtain a high-temperature resistant lithium-replenishing cathode material.

[0052] Example 6

[0053] By weight, 60 parts of lithium-rich manganese-based material, 32 parts of lithium oxalate, 5 parts of conductive carbon black, 7.5 parts of polyvinylidene fluoride, 2.5 parts of polyacrylamide, 8 parts of stabilizer, and 60 parts of N-methylpyrrolidone were taken. The stabilizer included the macromolecular silane coupling agent treated in Preparation Example 1, the zirconium oxide treated with the small molecule silane coupling agent in Preparation Example 2, and the polydopamine-coated spherical hydroxyapatite in Preparation Example 3, all in a mass ratio of 6:3:1. The mixture was stirred to obtain a high-temperature resistant lithium-replenishing cathode material.

[0054] Example 7

[0055] By weight, 60 parts of lithium-rich manganese-based material, 32 parts of lithium oxalate, 5 parts of conductive carbon black, 7.5 parts of polyvinylidene fluoride, 2.5 parts of polyacrylamide, 8 parts of stabilizer, and 60 parts of N-methylpyrrolidone were taken. The stabilizer included zirconium oxide treated with macromolecular silane coupling agent in Preparation Example 1, zirconium oxide treated with small molecule silane coupling agent in Preparation Example 2, and polydopamine-coated spherical hydroxyapatite in Preparation Example 3, all in a mass ratio of 3:4:1. The mixture was stirred to obtain a high-temperature resistant lithium-replenishing cathode material.

[0056] Comparative Example 1

[0057] By weight, 60 parts of lithium-rich manganese-based material, 32 parts of lithium oxalate, 5 parts of conductive carbon black, 7.5 parts of polyvinylidene fluoride, 10.5 parts of polyacrylamide and 60 parts of N-methylpyrrolidone were mixed to prepare a high-temperature resistant lithium-replenishing cathode material.

[0058] Comparative Example 2

[0059] By weight, 60 parts of lithium-rich manganese-based material, 32 parts of lithium oxalate, 5 parts of conductive carbon black, 7.5 parts of polyvinylidene fluoride, 2.5 parts of polyacrylamide, 0.7 parts of hexadecyltrimethoxysilane, 7.3 parts of hydroxyapatite nanowires and 60 parts of N-methylpyrrolidone were mixed to prepare a high-temperature resistant lithium-replenishing cathode material.

[0060] Comparative Example 3

[0061] Anhydrous ethanol and water were mixed at a volume ratio of 95:5 to prepare a mixture. 3-aminopropyltriethoxysilane was added at a mass ratio of 100:0.8 to the mixture and mixed well. Then, hydroxyapatite nanowires were added at a mass ratio of 0.5:5 to 3-aminopropyltriethoxysilane. The mixture was reacted at 60°C for 1 hour. After the reaction was completed, the precipitate was collected by centrifugation and dried to obtain pretreated hydroxyapatite nanowires.

[0062] By weight, 60 parts of lithium-rich manganese-based material, 32 parts of lithium oxalate, 5 parts of conductive carbon black, 7.5 parts of polyvinylidene fluoride, 2.5 parts of polyacrylamide, 8 parts of pretreated hydroxyapatite nanowires, and 60 parts of N-methylpyrrolidone were mixed to prepare a high-temperature resistant lithium-replenishing cathode material.

[0063] Performance testing

[0064] The high-temperature resistant lithium-replenishing cathode materials used in each embodiment and comparative example were uniformly coated onto aluminum foil and dried in an oven at 80°C to obtain cathode sheets. The cathode sheets were then assembled into button batteries with a 1 mol / L LiPF6 electrolyte (EC:DMC=1:1) and a lithium sheet as the anode.

[0065] Each button cell battery was subjected to a 45°C high-temperature cycling test: the test voltage was 2.0-4.55V, the charge / discharge rate was 1C, and the capacity retention rate of the button cell battery after 500 cycles was recorded.

[0066] Each button cell battery was subjected to a 55°C high-temperature storage performance test: the test voltage was 2.0-4.55V, the charge / discharge rate was 1C, and the batteries were removed from the storage box on the 35th day of storage. The capacity retention rate of the button cells on the 35th day was recorded.

[0067] Table 1 Performance Test Results

[0068]

[0069] As can be seen from Table 1, compared with the comparative examples, the high-temperature resistant lithium-replenishing cathode materials in Examples 1-3 of the present invention exhibit better high-temperature resistance, indicating that the hydroxyapatite nanowires treated with macromolecular silane coupling agents in the present invention can improve the thermal stability of the battery and ensure that the battery has better electrochemical performance.

[0070] As can be seen from Examples 2 and 4-7, the combination of hydroxyapatite nanowires, spherical hydroxyapatite, and zirconium oxide in a specific ratio can better improve the capacity retention rate of the battery during high-temperature cycling and its stability under high-temperature storage.

[0071] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This method of description is merely for clarity, and those skilled in the art should consider the specification as a whole. The technical solutions in the various embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-temperature resistant lithium-filling cathode material, characterized in that, It includes the following raw material components by weight: 80-100 parts of positive electrode active material, 5-13 parts of conductive agent, 5-10 parts of binder, 5-8 parts of stabilizer, and 50-60 parts of solvent. The adhesive is a compound composition of polyvinylidene fluoride and polyacrylamide; The stabilizer includes hydroxyapatite nanowires treated with a macromolecular silane coupling agent. The stabilizer also includes zirconium oxide treated with a small molecule silane coupling agent and spherical hydroxyapatite coated with polydopamine, wherein the mass ratio of the hydroxyapatite nanowires, spherical hydroxyapatite and zirconium oxide is (5-6):(2-3):

1.

2. The high-temperature resistant lithium-replenishing cathode material according to claim 1, characterized in that, The macromolecular silane coupling agent is dodecyltrimethoxysilane, hexadecyltrimethoxysilane, or trimethoxy-terminated polydimethylsiloxane.

3. The high-temperature resistant lithium-replenishing cathode material according to claim 1, characterized in that, The hydroxyapatite nanowires have a length of 100μm-200μm and a diameter of 10nm-100nm.

4. The high-temperature resistant lithium-replenishing cathode material according to claim 1, characterized in that, The spherical hydroxyapatite has a size of 8μm-12μm, and the zirconium oxide has a particle size of 0.5μm-3μm.

5. The high-temperature resistant lithium-replenishing cathode material according to claim 1, characterized in that, The small molecule silane coupling agent is 3-aminopropyltriethoxysilane or glycidoxypropyltrimethoxysilane.

6. The high-temperature resistant lithium-replenishing cathode material according to claim 1, characterized in that, The mass ratio of polyvinylidene fluoride to polyacrylamide is (2-3):

1.

7. The high-temperature resistant lithium-replenishing cathode material according to claim 1, characterized in that, The positive electrode active material includes lithium-rich manganese-based materials and at least one of lithium succinate, lithium oxalate, lithium iron phosphate, and lithium manganese iron phosphate.

8. The high-temperature resistant lithium-replenishing cathode material according to claim 1, characterized in that, The conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and carbon fiber.

9. A method for preparing a high-temperature resistant lithium-replenishing cathode material according to any one of claims 1-8, characterized in that, Take each raw material component according to the formula, mix them evenly to obtain a high-temperature resistant lithium-replenishing cathode material.

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