A sodium-ion battery metal oxide composition cathode material, a preparation method thereof and a sodium-ion battery

Abstract

The application discloses a sodium ion battery metal oxide composition positive electrode material, a preparation method thereof and a sodium ion battery, the positive electrode material comprising modified NaMn 1‑x Al x O2, a conductive agent, a binder and a dispersing agent; the modified NaMn 1‑x Al x O2 is prepared by the following steps: dissolving zirconyl nitrate and sodium nitrate in a solvent to obtain a mixed solution, adding tetraethyl orthosilicate and ammonium dihydrogen phosphate, adjusting pH and stirring to form a sol, adding NaMn 1‑x Al x O2, removing the solvent to obtain a gel, drying and heat treating to form an inner layer, dispersing the obtained product in a tris-hydroxymethyl aminomethane hydrochloride buffer solution, adding dopamine hydrochloride and phenylboronic acid to react, performing solid-liquid separation after the reaction is completed, drying and carbonizing the product to obtain the modified NaMn 1‑x Al x O2; the sodium ion battery has excellent cycle performance under fast charging with the positive electrode material as the positive electrode.

Description

Technical Field

[0001] The present application relates to the technical field of sodium-ion batteries, and particularly to a positive electrode material of a sodium-ion battery metal oxide composition, a preparation method thereof, and a sodium-ion battery. Background Art

[0002] Sodium-ion batteries are regarded as an important supplementary and alternative system for lithium-ion batteries due to their rich raw material resources and low cost, and have received extensive attention in recent years. Among them, layered oxide positive electrode materials have become the focus of research due to their high specific capacity, adjustable structure, and relatively mature synthesis process. Existing technologies mainly improve their structural stability through element doping (such as aluminum, iron, nickel, etc.), and often use surface coating to inhibit side reactions between the electrode and the electrolyte and improve the cycling performance.

[0003] However, in the application scenarios pursuing high-rate fast charging, the cycling performance is poor. The volume change of the active material and the intensity of the interfacial side reaction will be sharply amplified during the fast charging and discharging process. The existing single or simple composite coating layer is difficult to balance mechanical flexibility and strong interfacial protection. The single brittle inorganic layer is prone to cracking and failure, resulting in continuous erosion of the electrolyte on the core, accelerating manganese dissolution and structural distortion. The single flexible layer has weak chemical isolation ability for the electrolyte, and the composite coating layer is prone to separation and failure during the cycling process. Summary of the Invention

[0004] In order to improve the problem of insufficient cycling performance under fast charging, a positive electrode material of a sodium-ion battery metal oxide composition, a preparation method thereof, and a sodium-ion battery are provided.

[0005] The above first object of the present invention is achieved by the following technical solutions: A positive electrode material of a sodium-ion battery metal oxide composition, comprising the following components in parts by weight: Modified NaMn 1-x Al x O2 70 - 80 parts, Conductive agent 1 - 5 parts, Binder 5 - 10 parts, Dispersant 1 - 3 parts; Wherein, the x value range of modified NaMn 1-x Al x O2 is 0 < x < 1, and modified NaMn 1-x Al x O2 is prepared by a method including the following steps: S1: Dissolve zirconium oxynitrate and sodium nitrate in a solvent to obtain a mixed solution, add tetraethyl orthosilicate and ammonium dihydrogen phosphate to the mixed solution, adjust the pH, and stir and react to form a sol; S2: NaMn 1-xAl x O2 is added to the sol, dispersed, and the solvent is evaporated to obtain a gel. After drying and heat treatment, a sodium zirconium silicon phosphorus oxygen inner layer is formed. S3: The product obtained in step S2 is dispersed in tris(hydroxymethyl)aminomethane hydrochloride buffer to obtain a dispersion. Dopamine hydrochloride and phenylboronic acid are added to the dispersion to carry out the reaction. After the reaction is completed, solid-liquid separation is performed. The obtained solid is dried and carbonized to obtain modified NaMn. 1-x Al x O2.

[0006] By adopting the above technical solution, NaMn is modified. 1-x Al x O2, as the main active substance, has an intrinsic structure of layered oxide with reversible sodium ion insertion / extraction. This is followed by modification of NaMn. 1-x Al x The O2 surface forms a coating layer, which can reduce the problems of material structure collapse and capacity decay caused by manganese ion dissolution during recycling, crystal structure distortion caused by Jahn-Teller distortion, and side reactions with electrolyte, thereby improving cycle life. In NaMn 1-x Al x During O2 modification, the added zirconium oxynitrate provides the zirconium source. Zirconium ions can exist on the surface in the form of doped or composite oxides. Their high bond energy helps stabilize the crystal structure and improve stability. Tetraethyl orthosilicate hydrolyzes and condenses in acidic aqueous solution to form a network structure with silicon-oxygen tetrahedra as the basic unit. Ammonium dihydrogen phosphate provides phosphate ions. The phosphate groups have strong coordination ability and can combine with zirconium ions, silicon-oxygen network and metal ions on the surface of active material. After adjusting the pH, the added precursor components are copolymerized through sol-gel. After encapsulation, drying and heat treatment, an inorganic coating layer is formed, namely the sodium zirconium silicon phosphorus oxygen inner layer. This layer has a dense structure and stable chemical properties. It isolates the direct contact between the electrolyte and the active material, inhibits the oxidative decomposition reaction of the active material by the electrolyte, and reduces the loss of manganese ions in the electrolyte. Particles coated with the inner layer were dispersed in a tris(hydroxymethyl)aminomethane hydrochloride buffer solution. This buffer system provides a weakly alkaline environment in which the added dopamine hydrochloride undergoes oxidative self-polymerization. Its catechol and amine groups form a uniform polydopamine film on the particle surface through covalent and non-covalent interactions. The boric acid groups of the added phenylboronic acid can reversibly bond with the catechol groups on the polydopamine chain, introducing crosslinking points into the polymer network and enhancing the mechanical strength of the polymer layer and its adhesion to the inner layer. Carbonization treatment under an inert atmosphere causes the polydopamine-phenylboronic acid crosslinked polymer to pyrolyze into a carbonaceous material, forming a carbon layer. Nitrogen and boron atoms in this carbon layer are in-situ doped into the carbon framework. Nitrogen doping can introduce... To improve the electronic conductivity of carbon materials, boron atoms can be incorporated into the carbon lattice by replacing carbon atoms. Since boron atoms have only three valence electrons in their outer shell, acting as electron-deficient centers, their doping can alter the electronic structure of carbon materials. High electronic conductivity improves the material's own electronic conduction ability and enhances its ability as an electron acceptor, thereby increasing the bulk electronic conductivity of the carbon material. This provides an efficient electronic channel for charge compensation during the sodium ion insertion / extraction process, directly reducing the charge transfer impedance of the electrode. Furthermore, this carbon layer inherits the toughness and uniformity of the polymer precursor, enabling it to adapt to the lattice volume changes that occur during the repeated insertion / extraction of sodium ions. Through elastic deformation, it buffers internal stress, which helps prevent particle cracking or pulverization. The inner sodium zirconium silicon phosphorus oxygen rigid inorganic coating acts as a chemical barrier, effectively inhibiting electrolyte erosion and transition metal ion dissolution, ensuring the interfacial chemical stability during long-term cycling. The outer nitrogen boron co-doped carbon flexible conductive layer constructs an efficient electronic conduction network and buffers volume stress. Its boron doping further enhances the conductivity and structural stability of the carbon layer. The inner layer plays a role in chemical passivation and structural anchoring, while the carbon layer, as the outer layer, focuses on electronic conduction and mechanical buffering. The combination of the two achieves a balance between rigidity and flexibility, significantly reducing charge transport impedance while maintaining the integrity of the particle structure, thus jointly achieving excellent long cycle life and high-rate charge and discharge capability. Conductive agents construct an electronic conductive network within the electrode, reducing charge transfer resistance; binders maintain the mechanical integrity between electrode components and adapt to volume changes during cycling; dispersants ensure slurry uniformity, forming an electrode film with a consistent microstructure. In summary, the inner layer reduces side reactions and manganese ion outflow through its chemical inertness, while the carbon layer, as the outer layer, enhances conductivity and stabilizes the particle structure of active materials. The inner layer, outer layer, conductive agents, binders, and dispersants work together to reduce resistance and side reactions, resulting in high cycle stability during fast charging when applied to batteries.

[0007] Preferably, the value of x is in the range of 0.08 ≤ x ≤ 0.12.

[0008] By adopting the above technical solution, aluminum ions replace some manganese sites. Due to their stronger bonding energy with oxygen and the absence of the Jahn-Teller effect, they can effectively suppress the lattice distortion caused by manganese and improve the structural stability of the main lattice. With the aluminum doping amount within this range, a stabilization effect can be provided without excessively sacrificing the material's reversible capacity. This provides a more stable crystal matrix for subsequent surface modification, allowing the composite coating layer to play a more effective role. As a result, it is beneficial to the reversible changes in phase structure during cycling.

[0009] Preferably, the mass ratio of dopamine hydrochloride to phenylboronic acid is 1:(0.1-0.2).

[0010] By adopting the above technical solution, at this ratio, phenylboronic acid and dopamine hydrochloride can form a precursor polymer with a moderate degree of cross-linking, which helps to prevent excessive shrinkage or cracking of the carbon layer during carbonization and helps to form a continuous, dense conductive carbon layer with a certain mechanical strength. This carbon layer not only has better electronic conductivity, but also has a stronger bond with the surface of the active material and is not easily peeled off during cycling, thus providing more durable protection and conductivity.

[0011] Preferably, the conductive agent includes graphitized carboxylated multi-walled carbon nanotubes and hydroxylated conductive carbon black.

[0012] By adopting the above technical solution, graphitized carboxyl multi-walled carbon nanotubes possess a one-dimensional nanostructure and graphitized lattice, providing a long-range electron transport path. Their carboxyl functional groups enhance the interfacial bonding with active materials and binders, improving dispersibility. Hydroxylated conductive carbon black has a high specific surface area and abundant hydroxyl groups, providing point-to-point conductive contact, filling the gaps between active materials and carbon nanotubes, and constructing a three-dimensional conductive network. Carbon nanotubes serve as the conductive framework, and carbon black serves as the connection point, forming a highly efficient electronic conduction system, reducing the overall electrode resistance, improving the electrode's electronic conductivity, supporting high-rate charge and discharge, and maintaining the stability of the network structure during cycling, which is beneficial to cycling performance.

[0013] Preferably, the mass ratio of graphitized carboxyl multi-walled carbon nanotubes to hydroxylated conductive carbon black is (1-1.5):1.

[0014] By adopting the above technical solutions, when the proportion of carbon nanotubes is high, the network connectivity is enhanced, but too much may lead to agglomeration or affect the electrode compaction density. An appropriate proportion of carbon black ensures that the voids are fully filled and provides enough contact points. Within this range, long-range conduction and short-range contact are balanced, resulting in lower impedance of the electron transport path, better electronic conductivity of the electrode, and reduced ohmic loss during charging and discharging. At the same time, the uniform conductive network reduces local current density and promotes cycle stability.

[0015] Preferably, the adhesive is polyvinylidene fluoride.

[0016] By adopting the above technical solution, polyvinylidene fluoride (PVDF), a semi-crystalline polymer, possesses good chemical stability and bonding strength. After dissolving in a polar solvent, it forms a viscoelastic solution. During the drying process, the active material and conductive agent are bonded to the current collector through van der Waals forces and mechanical interlocking. The fluorine atoms of PVDF form weak interactions with the surface of the electrode components, enhancing interfacial adhesion. Its toughness can buffer the volume changes of the active material during charging and discharging, preventing crack formation and maintaining the integrity of the electrode structure. Furthermore, PVDF has a certain degree of swelling in the electrolyte but does not dissolve, which is beneficial for ion transport. As a binder, PVDF improves the cycle durability under fast charging.

[0017] Preferably, the dispersant is ammonium polyacrylate.

[0018] By adopting the above technical solution, ammonium polyacrylate provides positive charge through ammonium ions, which interact with the particle surface. Its polyanionic chains adsorb onto the surface of active materials and conductive agents, generating electrostatic repulsion and steric hindrance effects, reducing particle agglomeration in the slurry, making the components uniformly dispersed, forming a micro-uniform electrode film. The electrode has a consistent microstructure and interface characteristics, improving the utilization rate of active materials, uniform stress distribution during cycling, extending lifespan, and the conductive network promotes rapid electron transport, which is beneficial to improving cycle performance under fast charging.

[0019] The second objective of this invention is achieved through the following technical solution: The preparation method of the above-mentioned sodium-ion battery metal oxide composition cathode material includes the following steps: modifying NaMn 1-x Al x O2, conductive agent, binder, dispersant and solvent are mixed and stirred to form a slurry. The slurry is coated onto the current collector and then rolled into a sheet after drying.

[0020] By adopting the above technical solution, solvent dispersion ensures uniform distribution of each component, coating forms a continuous electrode layer, the drying process removes the solvent to form a porous structure, the rolling step improves the electrode density and interparticle contact, but retains appropriate porosity to facilitate electrolyte wetting, and the uniform slurry and compaction process optimize the macroscopic and microscopic structure of the electrode, promotes the connectivity of ion and electron transport paths, and improves the cycling performance under fast charging.

[0021] The third inventive objective of this invention is achieved through the following technical solution: A sodium-ion battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes the aforementioned positive electrode material.

[0022] By adopting the above technical solution, the resulting sodium-ion battery has a stable positive electrode material structure and conductivity characteristics that enable reversible insertion and extraction of sodium ions during charging and discharging, with fewer side reactions, and achieves high cycle capability under fast charging.

[0023] In summary, this application has at least the following beneficial effects: (1) Modified NaMn 1-x Al x As a layered oxide cathode material, aluminum doping of O2 helps to suppress Jahn-Teller distortion and improve the stability of the bulk structure. (2) A double-layer coating is adopted. The inner layer is a dense sodium zirconium silicon phosphorus oxygen inorganic layer, which mainly acts as a chemical barrier to inhibit electrolyte corrosion. The outer layer is a nitrogen boron co-doped carbon layer, which provides high electronic conductivity and buffers volume stress. The two work together to improve interface stability. (3) Conductive agents, binders and dispersants work together to optimize the electrode microstructure, build a stable conductive network and ensure uniform composition, thereby reducing the overall impedance and ultimately enabling the battery to achieve excellent cycle durability under fast charging conditions. Detailed Implementation

[0024] raw material Tetraethyl orthosilicate (99.999 wt% purity), ammonium dihydrogen phosphate (98 wt% purity), tris(hydroxymethyl)aminomethane hydrochloride buffer (Tris-HCl, 1 mol / L, pH 6.5), dopamine hydrochloride (5-hydroxydopamine hydrochloride, 98 wt% purity), polytetrafluoroethylene (average particle size 3 µm), phenylboronic acid (99.5 wt%), and sodium polyacrylate (average molecular weight 2100) were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Hydroxylated conductive carbon black, with an average particle size of 40 nm and a specific surface area of ​​96 m². 2 / g, hydroxyl content 5.5wt%, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; Graphitized carboxyl multiwalled carbon nanotubes, with a diameter of 10 nm, an inner diameter of 5 nm, a length of 20 µm, and a carboxyl content of 1.28 wt%, were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Multi-walled carbon nanotubes, with a diameter of 10 nm, an inner diameter of 5 nm, and a length of 20 µm, were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Conductive carbon black with an average particle size of 40 nm and a specific surface area of ​​125 m². 2 / g, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; Ammonium polyacrylate, 99 wt% purity, purchased from Experiment Valley (Nanjing) Information Technology Development Co., Ltd. Polyvinylidene fluoride, powder, average molecular weight 500,000, purchased from Zhejiang Juhua Co., Ltd. MnSO4·H2O, Al2(SO4)3·18H2O, Na2CO3, 25wt% ammonia, ZrO(NO3)2·2H2O, NaNO3, and N-methylpyrrolidone were all sourced from commercially available sources.

[0025] Preparation Example 1 A NaMn 0.9 Al 0.1 The preparation method of O2 is as follows: 164.2 g of MnSO4·H2O and 36 g of Al2(SO4)3·18H2O were dissolved in 500 mL of deionized water to obtain a metal salt solution. 120.2 g of Na2CO3 was dissolved in 400 mL of deionized water to obtain a sodium carbonate solution. The metal salt solution was mixed with 100 mL of 25 wt% ammonia water and stirred at 600 rpm for 15 min in a 50℃ water bath. The metal salt solution mixed with ammonia water and the sodium carbonate solution were added to a flask. The metal salt solution mixed with ammonia water was added at a dropping rate of 3 mL / min, and the sodium carbonate solution was added at a dropping rate of 2.8 mL / min, while maintaining stirring at 300 rpm. After the addition was complete, the reaction was carried out at 300 rpm and in a 50℃ water bath for 2 h. After the reaction was completed, the precipitate was collected by vacuum filtration to obtain the reactant. The precipitate was washed with deionized water until no SO4 was found in the filtrate. 2- (No white precipitate was detected by BaCl2). The precursor was dried at 110℃ under a vacuum of -0.095MPa for 12 hours. The precursor was then ball-milled with 62.28g of Na2CO3 for 30 minutes to obtain a homogeneous mixture. The mixture was placed in a muffle furnace and calcined at 500℃ for 4 hours, then at 850℃ for 12 hours, followed by natural cooling to room temperature (25℃). The mixture was then milled through a 400-mesh sieve to obtain NaMn. 0.9 Al 0.1 O2.

[0026] Preparation Example 2 A NaMn 0.85 Al 0.15 The difference between this preparation and Example 1 is that the amount of Al2(SO4)3·18H2O used is 53.8 g, the amount of MnSO4·H2O used is 156.1 g, and the amount of Na2CO3 used in preparing the sodium carbonate solution is 119.3 g, resulting in the product NaMn. 0.85 Al 0.15 O2; the rest of the preparation is the same as in Preparation Example 1.

[0027] Preparation Example 3 A NaMn 0.88 Al 0.12The difference between this preparation and Example 1 is that the amount of Al2(SO4)3·18H2O used is 43.2 g, the amount of MnSO4·H2O used is 159.9 g, and the amount of Na2CO3 used in preparing the sodium carbonate solution is 119.9 g, resulting in the product NaMn. 0.88 Al 0.12 O2; the rest of the preparation is the same as in Preparation Example 1.

[0028] Preparation Example 4 A NaMn 0.92 Al 0.08 The difference between this preparation and Example 1 is that the amount of O2 used is 28.9 g of Al2(SO4)3·18H2O, the amount of MnSO4·H2O used is 165.0 g, and the amount of Na2CO3 used in preparing the sodium carbonate solution is 120.9 g, resulting in the product NaMn. 0.92 Al 0.08 O2; the rest of the preparation is the same as in Preparation Example 1.

[0029] Preparation Example 5 A NaMn 0.95 Al 0.05 The difference between this preparation and Example 1 is that the amount of O2 used is 18.0 g of Al2(SO4)3·18H2O, the amount of MnSO4·H2O used is 167.5 g, and the amount of Na2CO3 used in preparing the sodium carbonate solution is 121.3 g, resulting in the product NaMn. 0.95 Al 0.05 O2; the rest of the preparation is the same as in Preparation Example 1.

[0030] Preparation Example 6 A modified NaMn 0.9 Al 0.1 O2 is prepared as follows: S1: Dissolve 2.6g of ZrO(NO3)2·2H2O and 1.28g of NaNO3 in 100mL of deionized water and stir at 300rpm for 15min to obtain a mixture. Then add 1.04g of tetraethyl orthosilicate and 1.73g of ammonium dihydrogen phosphate to the mixture and stir at 300rpm for 10min. Adjust the pH to 3.4 with 1M HCl solution and stir at 500rpm for 2h to obtain a sol. S2: Add 100g of NaMn 0.9 Al 0.1 O2 is added to the sol obtained in step S1, NaMn 0.9 Al 0.1O2 was obtained from Preparation Example 1. The mixture was stirred at 300 rpm for 30 min to obtain a suspension. The suspension was then placed in an 80°C water bath and stirred for 10 h to obtain a gel. The gel was placed in a vacuum drying oven at -0.095 MPa and 120°C for 12 h to obtain a dry gel. The dry gel was placed in a muffle furnace and heated to 600°C at a rate of 2°C / min, held at that temperature for 5 h, and then cooled to room temperature (25°C) with the furnace to obtain NaMn coated with a sodium zirconium silicon phosphorus oxide inner layer. 0.9 Al 0.1 O2; S3: NaMn coated with the sodium zirconium silicon phosphorus oxide inner layer obtained in S2 0.9 Al 0.1 O2 was added to 1 L of tris(hydroxymethyl)aminomethane hydrochloride buffer and dispersed at 3000 rpm for 30 min. 5 g of dopamine hydrochloride and 0.75 g of phenylboronic acid were added, and the mixture was stirred at 300 rpm for 24 h. After the reaction was complete, the solid reactant was obtained by centrifugation. The reactant was washed three times with deionized water and then placed in a vacuum drying oven at -0.095 MPa and dried at 60 °C for 12 h. The dried product was then placed in a tube furnace and heated to 600 °C at 5 °C / min under an argon atmosphere and carbonized for 2 h. After naturally cooling to room temperature (25 °C), the product was removed, yielding modified NaMn. 0.9 Al 0.1 O2.

[0031] Preparation Example 7 A modified NaMn 0.9 Al 0.1 O2 is prepared as follows: S1: Dissolve 2.6g of ZrO(NO3)2·2H2O and 1.28g of NaNO3 in 100mL of deionized water and stir at 300rpm for 15min to obtain a mixture. Then add 1.04g of tetraethyl orthosilicate and 1.73g of ammonium dihydrogen phosphate to the mixture and stir at 300rpm for 10min. Adjust the pH to 3.4 with 1M HCl solution and stir at 500rpm for 2h to obtain a sol. S2: Add 100g of NaMn 0.9 Al 0.1 O2 is added to the sol obtained in step S1, NaMn 0.9 Al 0.1O2 was obtained from Preparation Example 1. The mixture was stirred at 300 rpm for 30 min to obtain a suspension. The suspension was then placed in an 80°C water bath and stirred for 10 h to obtain a gel. The gel was placed in a vacuum drying oven at -0.095 MPa and 120°C for 12 h to obtain a dry gel. The dry gel was placed in a muffle furnace and heated to 600°C at a rate of 2°C / min, held at that temperature for 5 h, and then cooled to room temperature (25°C) with the furnace to obtain modified NaMn. 0.9 Al 0.1 O2;

[0032] A modified NaMn 0.9 Al 0.1 O2, which differs from Preparation Example 6 in that: no phenylboronic acid is added, and the dopamine hydrochloride content is 5.75 g; the rest of the contents are the same as Preparation Example 6.

[0033] Preparation Example 9 A modified NaMn 0.85 Al 0.15 O2, which differs from preparation example 6 in that NaMn is used. 0.85 Al 0.15 O2 and other mass substitutes for NaMn 0.9 Al 0.1 O2, NaMn 0.85 Al 0.15 O2 was derived from Preparation Example 2; the rest was the same as in Preparation Example 6.

[0034] Preparation Example 10 A modified NaMn 0.88 Al 0.12 O2, which differs from preparation example 6 in that NaMn is used. 0.88 Al 0.12 O2 and other mass substitutes for NaMn 0.9 Al 0.1 O2, NaMn 0.88 Al 0.12 O2 was derived from Preparation Example 3; the rest was the same as in Preparation Example 6.

[0035] Preparation Example 11 A modified NaMn 0.92 Al 0.08 O2, which differs from preparation example 6 in that NaMn is used. 0.92 Al 0.08 O2 and other mass substitutes for NaMn 0.9 Al 0.1 O2, NaMn 0.92 Al 0.08 O2 was derived from Preparation Example 4; the rest was the same as in Preparation Example 6.

[0036] Preparation Example 12 A modified NaMn 0.95 Al 0.05 O2, which differs from preparation example 6 in that NaMn is used. 0.95 Al 0.05 O2 and other mass substitutes for NaMn 0.9 Al 0.1 O2, NaMn 0.95 Al 0.05 O2 was derived from Preparation Example 5; the rest was the same as in Preparation Example 6.

[0037] Preparation Example 13 A modified NaMn 0.9 Al 0.1 The difference between O2 and Preparation Example 6 is that: dopamine hydrochloride is 5.4g and phenylboronic acid is 0.3g; the rest is the same as Preparation Example 6.

[0038] Preparation Example 14 A modified NaMn 0.9 Al 0.1 The difference between O2 and Preparation Example 6 is that: the amount of dopamine hydrochloride is 5.230 g, the amount of phenylboronic acid is 0.523 g, and the mass ratio of dopamine hydrochloride to phenylboronic acid is 1:0.1; the rest of the ingredients are the same as those in Preparation Example 6.

[0039] Preparation Example 15 A modified NaMn 0.9 Al 0.1 The difference between O2 and Preparation Example 6 is that: the amount of dopamine hydrochloride is 4.79 g, the amount of phenylboronic acid is 0.958 g, and the mass ratio of dopamine hydrochloride to phenylboronic acid is 1:0.2; the rest of the ingredients are the same as those in Preparation Example 6.

[0040] Preparation Example 16 A modified NaMn 0.9 Al 0.1 The difference between O2 and Preparation Example 6 is that: the amount of dopamine hydrochloride is 4.6 g and the amount of phenylboronic acid is 1.15 g; the rest of the ingredients are the same as those in Preparation Example 6.

[0041] Preparation Example 17 A modified NaMn 0.9 Al 0.1 O2 is prepared as follows: NaMn 0.9 Al 0.1 O2 was added to 10 L of tris(hydroxymethyl)aminomethane hydrochloride buffer, NaMn 0.9 Al 0.1O2 was derived from Preparation Example 1. The mixture was dispersed at 3000 rpm for 30 min, followed by the addition of 5 g of dopamine hydrochloride and 0.75 g of phenylboronic acid. The mixture was stirred at 300 rpm for 24 h. After the reaction was complete, the solid reactant was obtained by centrifugation. The reactant was washed three times with deionized water and then placed in a vacuum drying oven at -0.095 MPa. It was dried at 60 °C for 12 h. The dried product was then placed in a tube furnace and heated to 600 °C at 5 °C / min under an argon atmosphere. The temperature was maintained for 2 h for carbonization. After natural cooling to room temperature (25 °C), the product was removed, yielding modified NaMn. 0.9 Al 0.1 O2.

[0042] Example 1 A sodium-ion battery metal oxide composition cathode material is prepared as follows: 72g of N-methylpyrrolidone and 8g of polyvinylidene fluoride are added to a mixing tank and stirred at 300 rpm for 30 min, then at 500 rpm for 2 h to obtain a binder solution. 2g of ammonium polyacrylate is added to the binder solution and stirred at 800 rpm for 15 min. 1.3g of hydroxylated conductive carbon black and 1.7g of graphitized carboxyl multi-walled carbon nanotubes are added, and the mixture is stirred at 1500 rpm under a vacuum of -0.095 MPa for 60 min. 75g of modified NaMn is then added. 0.9 Al 0.1 O2, modified NaMn 0.9 Al 0.1 O2 was derived from Preparation Example 6. The mixture was stirred at 1000 rpm under a vacuum of -0.095 MPa for 2 hours. After stirring was stopped, it was allowed to stand and mature for 4 hours to obtain a coating material. An aluminum foil current collector was fixed on a coating machine substrate, and the coating material was applied to the aluminum foil current collector to a wet film thickness of 200 µm at a coating speed of 20 cm / s, resulting in a coated electrode. The coated electrode was then placed in a 120°C vacuum drying oven and dried under a vacuum of -0.1 MPa for 8 hours to remove the solvent. The dried electrode was cooled to room temperature (25°C) and then rolled using a roller press to achieve a compaction density of 3.0 g / cm³. 3 The rolling speed is 1m / min, and the electrode sheet is cut into 14mm round pieces using a cutting machine to obtain the positive electrode material of sodium-ion battery metal oxide composition.

[0043] Comparative Example 1 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 O2 was derived from Preparation Example 7; the rest was the same as in Example 1.

[0044] Comparative Example 2 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 O2 was derived from Preparation Example 8; the rest was the same as in Example 1.

[0045] Comparative Example 3 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 O2 was derived from Preparation Example 17; the rest was the same as in Example 1.

[0046] Example 2 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.85 Al 0.15 O2 and other mass substitutes for modified NaMn 0.9 Al 0.1 O2, of which modified NaMn 0.85 Al 0.15 O2 was derived from Preparation Example 9; the rest was the same as in Example 1.

[0047] Example 3 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.88 Al 0.12 O2 and other mass substitutes for modified NaMn 0.9 Al 0.1 O2, of which modified NaMn 0.88 Al 0.12 O2 was derived from Preparation Example 10; the rest was the same as in Example 1.

[0048] Example 4 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.92 Al 0.08 O2 and other mass substitutes for modified NaMn 0.9 Al 0.1 O2, of which modified NaMn 0.92 Al 0.08 O2 was derived from Preparation Example 11; the rest was the same as in Example 1.

[0049] Example 5 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.95 Al 0.05 O2 and other mass substitutes for modified NaMn 0.9 Al0.1 O2, of which modified NaMn 0.95 Al 0.05 O2 was derived from Preparation Example 12; the rest was the same as in Example 1.

[0050] Example 6 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 O2 was derived from Preparation Example 13; the rest was the same as in Example 1.

[0051] Example 7 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 O2 was derived from Preparation Example 14; the rest was the same as in Example 1.

[0052] Example 8 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 O2 was derived from Preparation Example 15; the rest was the same as in Example 1.

[0053] Example 9 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 O2 was derived from Preparation Example 16; the rest was the same as in Example 1.

[0054] Example 10 A sodium-ion battery metal oxide composition cathode material differs from Example 1 in that: multi-walled carbon nanotubes of equal mass are used instead of graphitized carboxyl multi-walled carbon nanotubes; the rest is the same as in Example 1.

[0055] Example 11 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that: conductive carbon black of equal mass is used instead of hydroxylated conductive carbon black; the rest is the same as in Example 1.

[0056] Example 12 A sodium-ion battery metal oxide composition cathode material differs from Example 1 in that: the mass ratio of graphitized carboxylated multi-walled carbon nanotubes is 1.3g and the mass ratio of hydroxylated conductive carbon black is 1.7g; the rest is the same as in Example 1.

[0057] Example 13 A sodium-ion battery metal oxide composition cathode material differs from Example 1 in that: the mass ratio of graphitized carboxylated multi-walled carbon nanotubes is 1.5g and the mass ratio of hydroxylated conductive carbon black is 1.5g; the rest is the same as in Example 1.

[0058] Example 14 A sodium-ion battery metal oxide composition cathode material differs from Example 1 in that: the mass ratio of graphitized carboxylated multi-walled carbon nanotubes is 1.8g and the mass ratio of hydroxylated conductive carbon black is 1.2g; the rest is the same as in Example 1.

[0059] Example 15 A sodium-ion battery metal oxide composition cathode material differs from Example 1 in that: the mass ratio of graphitized carboxylated multi-walled carbon nanotubes is 2.0g and the mass ratio of hydroxylated conductive carbon black is 1.0g; the rest is the same as in Example 1.

[0060] Example 16 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that: polytetrafluoroethylene is used in place of polyvinylidene fluoride by an equal mass; the rest is the same as in Example 1.

[0061] Example 17 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that: sodium polyacrylate is used in place of polyvinylidene fluoride by mass; the rest is the same as in Example 1.

[0062] Example 18 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that: styrene-butadiene rubber is used instead of polyvinylidene fluoride by mass; the rest is the same as in Example 1.

[0063] Example 19 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that: polyvinylpyrrolidone is used in place of ammonium polyacrylate by mass; the rest is the same as in Example 1.

[0064] Example 20 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that: methyl ethyl acrylate is used in place of ammonium polyacrylate by mass; the rest is the same as in Example 1.

[0065] Example 21 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that: sodium carboxymethyl cellulose is used in place of ammonium polyacrylate by mass; the rest is the same as in Example 1.

[0066] Example 22 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 The amount of O2 was 70g, the amount of graphitized carboxylated multi-walled carbon nanotubes was 0.57g, the amount of hydroxylated conductive carbon black was 0.43g, the amount of polyvinylidene fluoride was 5g, and the amount of ammonium polyacrylate was 1g; the rest of the ingredients were the same as in Example 1.

[0067] Example 23 A sodium-ion battery metal oxide composition cathode material, which differs from Example 1 in that it uses modified NaMn. 0.9 Al 0.1 The amount of O2 is 80g, the amount of graphitized carboxylated multi-walled carbon nanotubes is 2.85g, the amount of hydroxylated conductive carbon black is 2.15g, the amount of polyvinylidene fluoride is 10g, and the amount of ammonium polyacrylate is 3g; the rest of the ingredients are the same as in Example 1.

[0068] Example 24 A sodium-ion battery is provided, wherein the positive electrode is derived from the electrode of Example 1, the electrolyte is a sodium hexafluorophosphate solution in a mixed solvent of ethylene carbonate and propylene carbonate, wherein the volume ratio of ethylene carbonate and propylene carbonate is 1:1, the sodium hexafluorophosphate content is 1 mol / L, the negative electrode is a metallic sodium sheet with a diameter of 16 mm and a thickness of 0.5 mm, the separator is a Celgard polyolefin separator with a diameter of 19 mm, and the battery casing is a 2032 type stainless steel button battery casing, including a positive electrode casing, a negative electrode casing and a spring contact. The battery is assembled in a glove box under an argon protective atmosphere in the following order: positive electrode casing, positive electrode, electrolyte, separator, electrolyte, negative electrode, spring contact and negative electrode casing. After assembly, the battery is left to stand for 12 hours to obtain the sodium-ion battery.

[0069] Examples 25-46 All of these are sodium-ion batteries. The difference between them and Example 24 is that the source of the positive electrode sheet is different. Details of the source of the positive electrode sheet are shown in Table 1.

[0070] Table 1 Source of Positive Electrode Sheets in Examples 25-46

[0071] Comparative Example 3 A sodium-ion battery differs from Example 24 in that the positive electrode is derived from Comparative Example 1; the rest is the same as Example 24.

[0072] Comparative Example 4 A sodium-ion battery differs from Example 24 in that the positive electrode is derived from Comparative Example 2; the rest is the same as Example 24.

[0073] Comparative Example 5 A sodium-ion battery differs from Example 24 in that the positive electrode is derived from Comparative Example 3; the rest is the same as Example 24.

[0074] The performance of Examples 24-46 and Comparative Examples 3-5 was tested as follows: All batteries (2032 coin cells) from Examples 24-46 and Comparative Examples 3-5 were stabilized at 25°C in a constant temperature chamber and subjected to three cycles of charge-discharge at a current of 0.1C. The voltage window was set to 3.0V for battery activation. Constant current charging was used with a charging rate of 3C (simulating fast charging), and the charging cutoff condition was that the voltage reached 4.0V. Constant current discharging was used with a discharging rate of 0.5C, and the discharging cutoff was at 2.0V. The first cycle after activation was recorded as the first cycle. The cycle was repeated 500 times from the first cycle. The capacity of the first and 500th cycles was measured, and the capacity retention rate after 500 cycles was calculated using the formula (capacity of the 500th cycle / capacity of the first cycle) * 100%. The test results are shown in Table 2.

[0075] Table 2. Test results of Examples 24-46 and Comparative Examples 3-5

[0076] Based on Table 2, the test results are analyzed as follows: Comparing Example 24 with Comparative Examples 3 and 5, the capacity retention rate of Example 1 is greater than that of Comparative Example 3. The difference between Example 24 and Comparative Examples 3 and 5 is that the modified NaMn cathode material in Example 24... 0.9 Al 0.1 The O2 composite layer consists of an inner sodium-zirconium-silicon-phosphorus-oxygen layer and a nitrogen-boron-doped carbon layer; the O2 is deposited in NaMn using a sol-gel method. 1-x Al x A dense, rigid sodium-zirconium-silicon-phosphorus-oxygen (NaMnO2) inner layer was constructed on the O2 surface, effectively inhibiting electrolyte erosion. Based on this, a flexible, nitrogen-boron co-doped outer layer was formed through the cross-linking polymerization and carbonization of polydopamine and phenylboronic acid. This rigid-flexible bilayer structure synergistically enhances interfacial stability and electronic conductivity; therefore, the modified NaMnO2 cathode material… 0.9 Al 0.1 The O2 composite layer consists of an inner sodium zirconium silicon phosphorus oxygen layer and a nitrogen-boron doped carbon layer, which can improve the cycle performance under fast charging.

[0077] Comparing Example 24 and Comparative Example 4, the capacity retention rate of Example 1 is greater than that of Comparative Example 4. The difference between Example 24 and Comparative Example 4 is that the modified NaMn cathode material in Example 24... 0.9 Al 0.1During the preparation of the O2 outer coating layer, phenylboronic acid is added; boron atoms replace carbon atoms in the crystal lattice to achieve doping. Since boron atoms have only three valence electrons in their outer shell, they act as electron-deficient centers, altering the electronic structure of carbon materials and improving electronic conductivity. This provides an efficient electronic channel for charge compensation during sodium ion insertion / extraction, thus helping to reduce the charge transfer impedance of the electrode. Therefore, the modification of NaMn into the cathode material... 0.9 Al 0.1 Adding phenylboronic acid during the preparation of the O2 outer coating layer can improve the cycling performance under fast charging.

[0078] Comparing Examples 24 and 25-28, the capacity retention rates of Examples 1 and 26-27 are greater than those of Examples 25 and 28. The difference between Examples 24 and 25-28 is that the main active ingredient in Examples 24 and 26-27 is NaMn. 0.9 Al 0.1 O2, NaMn 0.88 Al 0.12 O2 or NaMn 0.92 Al 0.08 O2, i.e., aluminum doping at a level of 8%-12%, allows aluminum ions to replace some manganese sites. Due to their stronger bonding energy with oxygen and the absence of the Jahn-Teller effect, aluminum ions can effectively suppress lattice distortion and improve the stability of the main structure. While maintaining considerable reversible capacity, aluminum ions enhance the material's stability and provide a stable crystal matrix for subsequent surface modification, which is beneficial for reversible changes in phase structure during cycling. Therefore, an aluminum doping level of 8%-12% can improve cycling performance under fast charging.

[0079] Comparing Examples 24 and 29-32, the capacity retention rates of Examples 1 and 30-31 are greater than those of Examples 29 and 32. The difference between Examples 24 and 29-32 is that the modified NaMn of the cathode material in Examples 24 and 30-31... 0.9 Al 0.1 In the preparation of the O2 carbon layer, the mass ratio of dopamine hydrochloride to phenylboronic acid is 1:(0.1-0.2). At this ratio, phenylboronic acid and dopamine hydrochloride can form a moderately cross-linked precursor polymer, which is beneficial for obtaining a structurally complete, dense, and mechanically strong conductive carbon layer during the carbonization process. This carbon layer has better electronic conductivity and a stronger bond with the active material, and can stably perform its conductive and protective functions during long-term cycling. Therefore, the modified NaMn of the cathode material... 0.9 Al 0.1 When preparing the O2 carbon layer, the mass ratio of dopamine hydrochloride to phenylboronic acid is 1:(0.1-0.2), which can improve the cycle performance under fast charging.

[0080] Comparing Examples 24 and 33-34, the capacity retention rate of Example 1 is greater than that of Examples 33-34. The difference between Examples 24 and 33-34 is that the conductive agent in Example 24 is graphitized carboxyl multi-walled carbon nanotubes and hydroxylated conductive carbon black. Graphitized carboxyl multi-walled carbon nanotubes and hydroxylated conductive carbon black synergistically construct a three-dimensional conductive network. The former, with its one-dimensional structure and carboxyl functional groups, provides a long-range electron transport path and enhances interfacial bonding. The latter, with its high specific surface area and abundant hydroxyl groups, serves as a connection point to fill gaps, forming a stable conductive system, which helps to reduce electrode resistance and improve overall electronic conductivity and cycle stability. Therefore, using graphitized carboxyl multi-walled carbon nanotubes and hydroxylated conductive carbon black as conductive agents can improve cycle performance under fast charging.

[0081] Comparing Examples 24 and 35-38, the capacity retention rates of Examples 1 and 36-37 are greater than those of Examples 35 and 38. The difference between Examples 24 and 35-38 is that the mass ratio of graphitized carboxylated multi-walled carbon nanotubes to hydroxylated conductive carbon black in the cathode material of Examples 24 and 36-37 is (1-1.5):1. In this ratio, an appropriate amount of carbon nanotubes enhances long-range electron transport, while an appropriate amount of carbon black can effectively fill the gaps and provide sufficient contact points, thereby reducing electron transport impedance and ohmic losses during charging and discharging. At the same time, the uniform conductive network helps to alleviate local current polarization, thus improving cycle stability. Therefore, a mass ratio of graphitized carboxylated multi-walled carbon nanotubes to hydroxylated conductive carbon black of the cathode material of (1-1.5):1 can improve cycle performance under fast charging.

[0082] Comparing Examples 24 and 39-41, the capacity retention rate of Example 1 is greater than that of Examples 39-41. The difference between Examples 24 and 39-41 is that the binder for the positive electrode material in Example 24 is polyvinylidene fluoride (PVDF). PVDF is a semi-crystalline polymer with good chemical stability and adhesion. The viscoelastic solution it forms in polar solvents can effectively bind the various components of the electrode through interfacial interactions, buffering the volume change of the active material and maintaining the integrity of the electrode structure. Furthermore, its moderate swelling property in the electrolyte helps with ion transport. Therefore, using PVDF as the binder for the positive electrode material in Example 24 can improve the cycle performance under fast charging.

[0083] Comparing Examples 24 and 42-44, the capacity retention rate of Example 1 is greater than that of Examples 42-44. The difference between Examples 24 and 42-44 is that the dispersant of the positive electrode material in Example 24 is ammonium polyacrylate. Ammonium polyacrylate is adsorbed onto the particle surface through its polyanionic chains, and the electrostatic repulsion and steric hindrance effect are used to inhibit agglomeration, promote uniform dispersion of the slurry, and form an electrode film with a consistent microstructure. This is beneficial to improving the utilization rate of active materials and making the stress distribution more uniform during cycling. Therefore, the use of ammonium polyacrylate as the dispersant of the positive electrode material in Example 24 can improve the cycling performance under fast charging.

[0084] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of protection claimed in this application.

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