Preparation method of polyanion positive electrode material with high pole piece peel strength

Abstract

The invention discloses a preparation method of a polyanion positive electrode material with high pole piece peel strength. The preparation method comprises the following steps: S1, preparation of raw material slurry: dispersing an iron source, a carbon source, a phosphorus source, a sodium source and a dispersing agent in a pH environment at controlled temperature by taking water as a solvent, continuously stirring and grinding to obtain the raw material slurry; s2, preparation of a first precursor: drying the raw material slurry to obtain the first precursor; s3, preparation of a second precursor: pre-crystallizing the precursor in a protective atmosphere to obtain the second precursor; s4, preparing a third precursor: crushing the second precursor, mixing the crushed second precursor with a surfactant, and grinding to obtain the third precursor; and S5, high-temperature sintering: carrying out secondary sintering on the third precursor in a protective atmosphere to obtain the final polyanion positive electrode material. The preparation method of the polyanion positive electrode material with high pole piece peel strength has the characteristics of high pole piece peel strength, good conductivity and long cycle life.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion battery materials, in particular to a preparation method of a polyanion positive electrode material with high electrode strip peeling strength. BACKGROUND

[0002] With the rapid development of renewable energy and the increasing demand for large-scale energy storage, sodium ion batteries have broad development prospects. Sodium ion batteries can become substitutes for lithium ion batteries due to the advantages of abundant raw material sources, low cost and environmental protection.

[0003] At present, the three major systems of sodium ion positive electrode materials are: polyanion compounds, layered oxides and prussian blue compounds. The polyanion positive electrode material has the advantages of good thermal stability, long cycle life and high safety due to its structural safety, and occupies a unique ecological niche in the sodium battery positive electrode material system.

[0004] In the production of sodium ion batteries, the electrode strip peeling strength refers to the bonding force between the electrode coating after drying and the current collector. Although the polyanion has good structural stability, it will still swell and shrink to a certain extent during the sodium ion deintercalation process. If the interface bonding strength between the material and the binder is poor, the repeated volume change will continuously generate shear stress on the interface between the electrode coating and the current collector, causing premature failure and peeling of the interface, and leading to continuous deterioration of the cycle.

[0005] At present, the methods for improving the electrode strip peeling strength include increasing the amount of binder and pretreating the current collector. However, increasing the amount of binder will reduce the proportion of active material in the slurry, thereby reducing the energy density of the battery; and the pretreatment of the current collector will increase the complexity of the current collector process and the production cost.

[0006] Therefore, starting from the positive electrode material, the interface bonding ability of the material and the binder and the current collector is improved through process optimization of the material preparation process, which is the best and effective way to quickly improve the electrode strip peeling strength. SUMMARY

[0007] The application aims to provide a preparation method of a polyanion positive electrode material with high electrode strip peeling strength, which has the characteristics of high electrode strip peeling strength, good conductivity and long cycle life.

[0008] The application can be realized by the following technical scheme:

[0009] The preparation method of the polyanion positive electrode material with high electrode strip peeling strength comprises the following steps:

[0010] S1, preparation of raw material slurry: the iron source, carbon source, phosphorus source, sodium source and dispersant are dispersed in water as solvent under pH environment with temperature control, continuous stirring and grinding to obtain the raw material slurry;

[0011] S2, preparation of first precursor: the above raw material slurry is dried to obtain the first precursor;

[0012] S3, preparation of second precursor: the above precursor is pre-crystallized in a protective atmosphere to obtain the second precursor;

[0013] S4, preparation of third precursor: the second precursor is crushed and mixed with a surfactant and ground to obtain the third precursor;

[0014] S5, high-temperature sintering: the third precursor is sintered twice in a protective atmosphere to obtain the final polyanion positive electrode material.

[0015] Further, in step S1, the temperature for temperature control is 40-50℃. Combined with the characteristics that the viscosity of liquid fluid decreases with increasing temperature, a large amount of organic acid is rich in the above slurry which is relatively viscous at room temperature. Therefore, reasonable control of the grinding temperature not only improves the mixing and grinding efficiency, but also promotes the reaction activity of the materials in the slurry while preparing for the subsequent drying process, reducing the generation of destructive stress in the drying process.

[0016] Further, in step S1, the pH is controlled to be 5-7. When the pH is less than 5, hydrogen ions in the solution are easy to compete with organic acid radicals to cause the decomposition of the complex to generate the conjugate acid of the organic acid radical and the iron salt. When the solution is alkaline (pH greater than 7), it is not only possible to break the coordination bond between iron ions and organic acid radicals, making organic acid radicals and iron ions free in the solution, but also easy to cause the hydrolysis of iron ions.

[0017] Further, in step S3, the sintering temperature for pre-crystallization is 400-450℃, the heating rate is 1-3℃ / min, and the holding time is 8-12h; the protective atmosphere is nitrogen and / or argon; wherein, in the range of 400-450℃, the organic matter will not be completely graphitized at this temperature, but will form a stable, amorphous carbon skeleton rich in aromatic ring structure through dehydration, crosslinking, cyclization and other reactions. The carbon layer uniformly wrapped around the inorganic matter can physically block the direct contact between the grains in the subsequent high-temperature stage, effectively inhibiting Ostwald ripening, so as to obtain fine and uniform grains.

[0018] Further, in step S4, the surfactant is one or more of 3-hydroxypropionic acid, lactic acid, and omega-hydroxy fatty acid. The above surfactant is a short-chain hydroxy fatty acid or a medium-chain hydroxy fatty acid. Taking the hydroxy fatty acid as an example, the hydroxy fatty acid plays the roles of grinding aid, surface coating, and secondary pore forming. In the grinding process, the hydroxy fatty acid molecules are adsorbed on the particle surface through the hydrophilic groups (-COOH, -OH) to form an organic molecular film. The steric hindrance effect of the hydrophobic tail chain can effectively prevent the newly generated fine particles from agglomerating under the action of mechanical force and van der Waals force. In the subsequent sintering process, the organic matter will decompose and volatilize, leaving a cavity on the particle surface. Finally, a nanocrystal-porous carbon network structure is formed.

[0019] Further, in step S5, the high-temperature sintering conditions are as follows: sintering temperature 580-600℃, heating rate 1-3℃ / min, and protective atmosphere nitrogen and / or argon. In the present application, 580-600℃ provides sufficient thermodynamic driving force for the crystal nucleation and growth of materials such as sodium iron phosphate, ensuring that the precursor is completely converted into the target crystal phase with good crystallinity and electrochemical activity. The amorphous carbon formed by pre-sintering is further cross-linked and ordered, and its electrical conductivity is significantly improved, but it will not be graphitized. In addition, it can effectively promote atomic diffusion and complete lattice reconstruction, thereby inhibiting the generation of metastable phases or impurities and obtaining high-purity products. If the temperature is too low, the crystallization will not be complete; if the temperature is too high, phase decomposition or new impurities may be generated.

[0020] Further, in step S1, the dispersant is one or more of polyethylene glycol, polyacrylic acid, polyacryl alcohol, polyacrylamide, polyethylene oxide, polyvinylpyrrolidone, polymaleic acid, polyethylene glycol monomethyl ether, polyethylene glycol diacrylate, polyethylene glycol stearate, polyethylene glycol amine, polyethylene glycol sulfonic acid, polyethylene glycol phosphate, polyethylene glycol silane, polyethylene glycol block copolymer, and polyethylene glycol graft copolymer.

[0021] Further, the iron source is an organic iron source and / or an inorganic iron source. The organic iron source is one or more of ferric citrate, ferric oxalate, ferric acetate, basic ferric acetate, and ferric acrylate. The advantage of using an organic iron salt as the iron source is that the organic acid radical and the iron ion do not exist as free ions in the solution. The organic acid radical and the iron ion are combined through a coordination bond to form a complex with the iron ion as the center.

[0022] Further, the carbon source is one or more of citric acid, sodium citrate, isocitric acid, glucose, gluconic acid, sucrose, graphene, carbon nanotube, ascorbic acid, ketoglutaric acid, oxalic acid, tartaric acid, gluconic acid, ethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid, ethylene glycol diethyl ether diamine tetraacetic acid, nitrilotriacetic acid, ethylenediamine di-o-hydroxyphenyl acetic acid, 8-hydroxyquinoline, phenanthroline, bipyridine, dithiocarbamate, 1,2-dihydroxybenzene-3,5-disodium sulfonate, acetylacetone, and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid.

[0023] Further, the phosphorus source is one or more of triethyl phosphine, aminotriisopropyl phosphonic acid, hydroxyethylidene diphosphonic acid, phosphoric acid, triphenyl phosphine, triethyl phosphate, triphenyl phosphate, adenosine triphosphate, glyphosate, triphenyl phosphine oxide, tris(chloroisopropyl)phosphate, tetraethyl pyrophosphate, phospholipid, hexamethylphosphoramide, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, and metaphosphoric acid.

[0024] Further, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium chloride, sodium sulfate, sodium nitrate, sodium silicate, sodium acetate, monosodium phosphate, disodium hydrogen phosphate, sodium phosphate, sodium oxalate, sodium benzoate, sodium citrate, sodium thiosulfate, sodium borohydride, sodium methoxide, sodium ethoxide, sodium stearate, sodium glutamate, sodium perchlorate, and sodium valproate.

[0025] Further, in step S2, the drying method is one or more of oven drying, spray drying, freeze drying, microwave drying, infrared drying, vacuum drying, and rotary flash drying.

[0026] Further, in step S4, the mixing method is one or more of convection mixing, diffusion mixing, and shear mixing, and the mixing process simultaneously implements a crushing process, and the crushing method is one or more of crushing, impact crushing, grinding, and airflow crushing.

[0027] The poly-anion positive electrode material preparation method with high pole piece peeling strength has the following advantages:

[0028] First, the pole piece peeling force is high. The present application performs controllable micro-nano reconstruction on the material surface layer. The pre-crystallization of the first sintering ensures the formation and stability of the main structure of the material, and the subsequent secondary etching process precisely constructs a rich multi-level rough structure of protrusions and ravines on the material surface. Through the increased surface roughness, the contact area of the binder and the active material is greatly expanded. When the binder solution is coated, more sufficient infiltration and spreading can be achieved. After solidification, the binder macromolecular chain segments can penetrate into the micro-nano pores, producing a strong "anchoring effect" and "physical occlusion" action, thereby significantly enhancing the adhesion between the active material and the current collector, and ultimately greatly improving the pole piece peeling force.

[0029] Second, good conductivity, the application synchronously optimizes the material from two aspects of the conductive network and the interface structure by adopting the synergistic process of "high carbon coating" and "secondary sintering etching".

[0030] Third, long cycle life, the high carbon coating not only forms a continuous and dense conductive layer on the surface of the active material, greatly improving the electron transport efficiency, but more importantly, this thick carbon shell acts as an elastic buffer matrix, which can effectively adapt to the volume change of the material during the cycle process and inhibit the particle breakage. A rich micron / nanometer double-scale pore is constructed in the carbon coating layer and the subsurface layer of the material. On the one hand, the pore provides ample channels for electrolyte infiltration and ion rapid migration, and on the other hand, in combination with the high carbon layer, a three-dimensional integrated network of "conductive-buffer-ion conduction" is formed. The synergistic effect of the two stabilizes the interface structure of the electrode, significantly slows down the failure of the active material and the side reaction of the electrolyte, thereby fundamentally enhancing the long-term cycle life and capacity retention rate of the material. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 SEM images for application examples;

[0032] Figure 2 Polar plate peel strength test patterns of different embodiments;

[0033] Figure 3 Cycle performance test patterns of different embodiments. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solutions of the present application, the product of the present application will be further described in detail below in combination with embodiments.

[0035] The preparation method of the high-polar anion positive electrode material polar plate of the present application comprises the following steps:

[0036] S1, preparation of raw material slurry: iron source, carbon source, phosphorus source, sodium source and dispersant are dispersed in water as solvent under pH environment, continuously stirred and ground to obtain raw material slurry;

[0037] S2, preparation of first precursor: the above raw material slurry is dried to obtain the first precursor;

[0038] S3, preparation of second precursor: the above precursor is pre-crystallized in a protective atmosphere to obtain the second precursor;

[0039] S4, preparation of third precursor: the second precursor is crushed and mixed with a surfactant and ground to obtain the third precursor;

[0040] S5, high-temperature sintering: the third precursor is sintered again in a protective atmosphere, and a final polyanion positive electrode material is obtained.

[0041] Further, in step S1, the temperature of the temperature control is 40-50℃.

[0042] Further, in step S1, the pH is controlled to be 5-7.

[0043] Further, in step S3, the sintering temperature of the pre-crystallization is 400-450℃, the heating rate is 1-3℃ / min, the holding time is 8-12h, and the protective atmosphere is nitrogen and / or argon.

[0044] Further, in step S4, the surfactant is one or more of 3-hydroxypropionic acid, lactic acid, and omega-hydroxy fatty acid.

[0045] Further, in step S5, the high-temperature sintering conditions are: a sintering temperature of 580-600℃, a heating rate of 1-3℃ / min, and a protective atmosphere of nitrogen and / or argon.

[0046] Further, in step S1, the dispersant is one or more of polyethylene glycol, polyacrylic acid, polyacrylic alcohol, polyacrylamide, polyethylene oxide, polyvinylpyrrolidone, polymaleic acid, polyethylene glycol monomethyl ether, polyethylene glycol diacrylate, polyethylene glycol stearate, polyethylene glycol amine, polyethylene glycol sulfonic acid, polyethylene glycol phosphate, polyethylene glycol silane, polyethylene glycol block copolymer, and polyethylene glycol graft copolymer.

[0047] Further, the iron source is an organic iron source and / or an inorganic iron source, and the organic iron source is one or more of ferric citrate, ferric oxalate, ferric acetate, basic ferric acetate, and ferric acrylate. It should be noted that the inorganic iron source is not limited and can be any conventional inorganic iron source.

[0048] Further, the carbon source is one or more of citric acid, sodium citrate, isocitric acid, glucose, gluconic acid, sucrose, graphene, carbon nanotubes, ascorbic acid, ketoglutaric acid oxalic acid, tartaric acid, gluconic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, nitrilotriacetic acid, ethylenediamine di-o-hydroxyphenyl acetic acid, 8-hydroxyquinoline, phenanthroline, bipyridine, dithiocarbamate, 1,2-dihydroxybenzene-3,5-disodium sulfonate, acetylacetone, and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid.

[0049] Further, the phosphorus source is one or two or more of triethylphosphine, aminotrimethylene phosphonic acid, hydroxyethylidene diphosphonic acid, phosphoric acid, triphenylphosphine, triethyl phosphate, triphenyl phosphate, adenosine triphosphate, glyphosate, triphenylphosphine oxide, tris(chloroisopropyl)phosphate, tetraethyl pyrophosphate, phospholipid, hexamethylphosphorus triamide, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, and metaphosphoric acid.

[0050] Further, the sodium source is one or two or more of sodium carbonate, sodium hydroxide, sodium chloride, sodium sulfate, sodium nitrate, sodium silicate, sodium acetate, monosodium phosphate, disodium hydrogen phosphate, sodium phosphate, sodium oxalate, sodium benzoate, sodium citrate, sodium thiosulfate, sodium borohydride, sodium methoxide, sodium ethoxide, sodium stearate, sodium glutamate, sodium perchlorate, and sodium valproate.

[0051] Further, in step S2, the drying method is one or two or more of oven drying, spray drying, freeze drying, microwave drying, infrared drying, vacuum drying, and rotary flash drying.

[0052] Further, in step S4, the mixing method is one or two or more of convection mixing, diffusion mixing, and shear mixing, and the mixing process simultaneously implements a crushing process, and the crushing method is one or two or more of crushing, impact crushing, grinding, and airflow crushing.

[0053] Example 1

[0054] This embodiment relates to a polyanion positive electrode material with high pole piece peeling strength, and a preparation method thereof includes the following steps:

[0055] S1, preparation of raw material slurry: the iron source, carbon source, phosphorus source, sodium source, and dispersant are dispersed in water as a solvent under temperature control and pH environment, continuously stirred, and ground to obtain a raw material slurry. Specifically, the temperature control temperature is 50°C, and the pH is controlled to 6.

[0056] S2, preparation of first precursor: the above raw material slurry is dried to obtain a first precursor. Specifically, the drying method is oven drying.

[0057] S3, preparation of second precursor: the above precursor is pre-crystallized in a protective atmosphere to obtain a second precursor. Specifically, the sintering temperature of pre-crystallization is 450°C, the heating rate is 2°C / min, and the holding time is 8h; the protective atmosphere is nitrogen.

[0058] S4, preparation of third precursor: the second precursor is crushed, mixed with a surfactant, and ground to obtain a third precursor. Specifically, the mixing method is convection mixing, the mixing process simultaneously implements a crushing process, and the crushing method is crushing; the surfactant is 3-hydroxypropionic acid.

[0059] S5, high-temperature sintering: the third precursor is sintered in a protective atmosphere, and a final polyanion positive electrode material is obtained. Specifically, the high-temperature sintering conditions are: a sintering temperature of 600℃, a heating rate of 2℃ / min, and a protective atmosphere of nitrogen or argon.

[0060] In this embodiment, the dispersant is polyethylene glycol, polyacrylic acid, polyacrylic alcohol, polyacrylamide, polyethylene oxide, polyvinylpyrrolidone, and polymaleic acid; the iron source is an organic iron source and an inorganic iron source, the organic iron source is ferric citrate, ferric oxalate, and ferric acetate; the carbon source is citric acid, sodium citrate, isocitric acid, glucose, gluconic acid, sucrose, graphene, carbon nanotubes, ascorbic acid, ketoglutaric acid oxalic acid, tartaric acid, gluconic acid, ethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid, ethylene glycol diethyl ether diamine tetraacetic acid, and nitrilotriacetic acid; the phosphorus source is triethyl phosphine, amino-tris-methyl phosphonic acid, hydroxyethylidene diphosphonic acid, phosphoric acid, triphenyl phosphine, triethyl phosphate, and triphenyl phosphate; and the sodium source is sodium carbonate, sodium hydroxide, sodium chloride, sodium sulfate, sodium nitrate, sodium silicate, and sodium acetate.

[0061] Embodiment 2

[0062] This embodiment relates to a polyanion positive electrode material with high pole piece peeling strength, and a preparation method thereof includes the following steps:

[0063] S1, preparation of raw material slurry: the iron source, carbon source, phosphorus source, sodium source, and dispersant are dispersed in water as a solvent under temperature control in a pH environment, continuously stirred, and ground to obtain a raw material slurry. Specifically, the temperature control temperature is 45℃, and the pH control is 5.

[0064] S2, preparation of the first precursor: the above raw material slurry is dried to obtain the first precursor. Specifically, the drying method is spray drying.

[0065] S3, preparation of the second precursor: the above precursor is pre-crystallized in a protective atmosphere to obtain the second precursor. Specifically, the pre-crystallization sintering temperature is 430℃, the heating rate is 1℃ / min, the holding time is 12h, and the protective atmosphere is nitrogen or argon.

[0066] S4, preparation of the third precursor: the second precursor is crushed, mixed with a surfactant, and ground to obtain the third precursor. Specifically, the mixing method is diffusion mixing, the mixing process simultaneously realizes the crushing process, the crushing method is crushing and impact crushing, and the surfactant is lactic acid and omega-hydroxy fatty acid.

[0067] S5, high-temperature sintering: the third precursor is sintered in a protective atmosphere, and a final polyanion positive electrode material is obtained. Specifically, the high-temperature sintering conditions are: a sintering temperature of 600℃, a heating rate of 2℃ / min, and a protective atmosphere of nitrogen or argon.

[0068] In the present embodiment, the dispersant is polyethylene glycol diacrylate, polyethylene glycol stearate, polyethylene glycol amine, polyethylene glycol sulfonic acid, polyethylene glycol phosphate, polyethylene glycol silane, polyethylene glycol block copolymer, polyethylene glycol graft copolymer; the iron source is an organic iron source, the organic iron source is ferric citrate, ferric oxalate, ferric acetate; the carbon source is citric acid, ethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid, ethylene glycol diethyl ether diamine tetraacetic acid, nitrilotriacetic acid, acetylacetone, N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid; the phosphorus source is phosphorous acid, hypophosphorous acid, pyrophosphoric acid, metaphosphoric acid; the sodium source is sodium citrate, sodium thiosulfate, sodium borohydride, sodium methoxide, sodium ethoxide, sodium stearate, sodium glutamate, sodium perchlorate, sodium valproate.

[0069] Example 3

[0070] The present embodiment relates to a polyanion positive electrode material with high pole piece peeling strength, and a preparation method thereof, which comprises the following steps:

[0071] S1, preparation of raw material slurry: the iron source, carbon source, phosphorus source, sodium source and dispersant are dispersed in water as the solvent under temperature control and pH environment, and continuously stirred and ground to obtain the raw material slurry. Specifically, the temperature control temperature is 40℃, and the pH control is 7.

[0072] S2, preparation of first precursor: the above raw material slurry is subjected to drying treatment to obtain the first precursor. Specifically, the drying method is freeze drying or microwave drying.

[0073] S3, preparation of second precursor: the above precursor is subjected to pre-crystallization in a protective atmosphere to obtain the second precursor. Specifically, the sintering temperature of pre-crystallization is 400℃, the heating rate is 3℃ / min, and the holding time is 10h; the protective atmosphere is nitrogen and argon.

[0074] S4, preparation of third precursor: the second precursor is crushed, mixed with a surfactant and ground to obtain the third precursor. Specifically, the mixing method is shear mixing, the mixing process realizes the crushing process at the same time, and the crushing method is grinding crushing; the surfactant is 3-hydroxypropionic acid, lactic acid or ω-hydroxy fatty acid.

[0075] S5, high-temperature sintering: the third precursor is subjected to secondary sintering in a protective atmosphere to obtain the final polyanion positive electrode material. Specifically, the high-temperature sintering conditions are as follows: sintering temperature 580℃, heating rate 3℃ / min, and protective atmosphere nitrogen and / or argon.

[0076] In the embodiment, the dispersant is polyacrylamide, polyethylene oxide, polyvinylpyrrolidone, polymaleic acid, polyethylene glycol monomethyl ether, polyethylene glycol diacrylate, polyethylene glycol stearate, polyethylene glycol amine, polyethylene glycol block copolymer, polyethylene glycol graft copolymer; the iron source is an organic iron source, the organic iron source is iron acetate, basic iron acetate, iron acrylate; the carbon source is diethylenetriamine pentaacetic acid, ethylene glycol diethyl ether diamine tetraacetic acid, nitrilotriacetic acid, ethylenediamine di-o-hydroxyphenyl acetic acid, 8-hydroxyquinoline, phenanthroline, bipyridine, dithiocarbamate, 1,2-dihydroxybenzene-3,5-disulfonic acid sodium, acetylacetone, N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid; the phosphorus source is triethyl phosphate, triphenyl phosphate, adenosine triphosphate, glyphosate, triphenylphosphine oxide, tris(chloroisopropyl)phosphate; the sodium source is sodium citrate, sodium thiosulfate, sodium borohydride, sodium methoxide, sodium ethoxide, sodium stearate, sodium glutamate, sodium perchlorate, sodium valproate.

[0077] Embodiment 4

[0078] The embodiment relates to a polyanion positive electrode material with high pole piece peeling strength, and a preparation method thereof comprises the following steps.

[0079] S1, preparation of raw material slurry: the iron source, the carbon source, the phosphorus source, the sodium source and the dispersant are dispersed in water as a solvent under pH environment, continuous stirring and grinding to obtain the raw material slurry. Specifically, the temperature of temperature control is 42 DEG C, and the pH is controlled to be 6.

[0080] S2, preparation of the first precursor: the raw material slurry is dried to obtain the first precursor. Specifically, the drying method is infrared drying or vacuum drying.

[0081] S3, preparation of the second precursor: the precursor is pre-crystallized in a protective atmosphere to obtain the second precursor. Specifically, the sintering temperature of pre-crystallization is 420 DEG C, the heating rate is 2 DEG C / min, and the holding time is 11 h; the protective atmosphere is nitrogen and argon.

[0082] S4, preparation of the third precursor: the second precursor is crushed, mixed with a surfactant and ground to obtain the third precursor. Specifically, the mixing mode is shear mixing, the mixing process realizes the crushing process at the same time, and the crushing mode is air flow crushing; the surfactant is 3-hydroxypropionic acid, lactic acid and omega-hydroxy fatty acid.

[0083] S5, high-temperature sintering: the third precursor is sintered twice in a protective atmosphere to obtain the final polyanion positive electrode material. Specifically, the high-temperature sintering conditions are as follows: sintering temperature 590 DEG C, heating rate 2 DEG C / min, and protective atmosphere nitrogen and or argon.

[0084] In the embodiment, the dispersant is polyethylene glycol, polyacrylic acid, and polyvinyl alcohol; the iron source is an organic iron source and an inorganic iron source, the organic iron source is ferric citrate and ferric oxalate; the carbon source is citric acid, sodium citrate, isocitric acid, glucose, gluconic acid, sucrose, and graphene; the phosphorus source is triethyl phosphine, aminotri(methylphosphine) acid, hydroxyethylidene diphosphonic acid, phosphoric acid, and triphenylphosphine; and the sodium source is sodium carbonate, sodium hydroxide, sodium chloride, sodium sulfate, sodium nitrate, sodium silicate, and sodium acetate.

[0085] Embodiment 5

[0086] The embodiment relates to a polyanion positive electrode material with high pole piece peeling strength, and a preparation method thereof.

[0087] S1, preparation of a raw material slurry: an iron source, a carbon source, a phosphorus source, a sodium source, and a dispersant are dispersed in water as a solvent under temperature control and pH control, and are continuously stirred and ground to obtain a raw material slurry. Specifically, the temperature control temperature is 45°C, and the pH control is 6.

[0088] S2, preparation of a first precursor: the raw material slurry is subjected to drying treatment to obtain a first precursor. Specifically, the drying method is microwave drying.

[0089] S3, preparation of a second precursor: the precursor is subjected to pre-crystallization in a protective atmosphere to obtain a second precursor. Specifically, the pre-crystallization sintering temperature is 430°C, the heating rate is 2°C / min, and the holding time is 10 h; and the protective atmosphere is nitrogen and argon.

[0090] S4, preparation of a third precursor: the second precursor is crushed, mixed with a surfactant, and ground to obtain a third precursor. Specifically, the mixing mode is shear mixing, the mixing process simultaneously realizes the crushing process, the crushing mode is crushing and impact crushing; and the surfactant is 3-hydroxypropionic acid, lactic acid, and omega-hydroxy fatty acid.

[0091] S5, high-temperature sintering: the third precursor is subjected to secondary sintering in a protective atmosphere to obtain the final polyanion positive electrode material. Specifically, the high-temperature sintering conditions are as follows: the sintering temperature is 600°C, the heating rate is 2°C / min, and the protective atmosphere is nitrogen and / or argon.

[0092] In this embodiment, the dispersant is polyethylene glycol, polyacrylic acid, polyacryl alcohol, polyacrylamide, polyethylene oxide, polypyrrolidone, or polymaleic acid; the iron source is an organic iron source, which includes ferric citrate, ferric oxalate, ferric acetate, basic ferric acetate, or ferric acrylate; the carbon source is citric acid, sodium citrate, isocitrate, glucose, gluconic acid, sucrose, or graphene; the phosphorus source is triethylphosphine, aminotrimethylphosphonic acid, hydroxyethylidene diphosphate, phosphoric acid, triphenylphosphine, triethyl phosphate, triphenyl phosphate, adenosine triphosphate, glyphosate, or triphenylphosphine oxide; and the sodium source is sodium carbonate, sodium hydroxide, sodium chloride, sodium sulfate, or sodium nitrate.

[0093] Application Example 1

[0094] This embodiment relates to a polyanionic cathode material with high electrode peel strength, and its preparation method includes the following steps:

[0095] S1. Preparation of raw material slurry: Specifically, FeC2O4·2H2O is used as the iron source, phosphoric acid as the phosphorus source, sodium hydroxide as the sodium source, and glucose and carbon nanotubes as the carbon source. The iron, phosphorus, and sodium sources are added according to an elemental ratio of Fe / P = 0.75 and Na / P = 1.3. Water is added for dispersion, and the mixture is then milled. When the particle size distribution reaches D50 = 1 micrometer, polyvinyl acid, glucose, and carbon nanotubes are added, ensuring a Fe to glucose molar ratio of 10:1 and that the amount of carbon nanotubes added is the same as the mass of glucose. Milling continues until the particle size distribution reaches 0.5-0.6 micrometers.

[0096] S2, Preparation of the first precursor: Specifically, the slurry in S1 is spray-dried using a pressure spray dryer with an inlet air temperature of 220°C and an outlet temperature of 120°C.

[0097] S3. Preparation of the second precursor: The spray-dried precursor from S2 was heated to 420℃ in a vacuum box furnace at a heating rate of 5℃ / min and held at that temperature for 5 hours. The sintering atmosphere was high-purity nitrogen.

[0098] S4. Preparation of the third precursor: The second precursor was pulverized using an air jet mill to achieve a particle size distribution of D50 = 3 micrometers. 2.0% by weight of hydroxy fatty acid was added to the pulverized third precursor, and the mixture was then ground in a ball mill for 1 hour.

[0099] S5. High-temperature sintering: Specifically, the mixture of the third precursor in S4 and the hydroxy fatty acid is heated to 300°C at a heating rate of 2°C / min and held for 2 hours, and then heated to 600°C at a heating rate of 5°C / min and held for 8 hours in a vacuum box furnace.

[0100] The prepared positive electrode material was homogenized according to the mass ratio of active material slurry: active material: PVDF: SP: MWCNT=95: 3:1.5:0.5, and coated onto carbon-coated aluminum foil with a single-sided surface density of 150g / ㎡ to make a positive electrode sheet. The positive electrode sheet was then assembled with a hard carbon negative electrode sheet, a separator, an electrolyte, etc. to form a sodium-ion battery.

[0101] Comparative Example 1

[0102] This embodiment relates to a polyanionic cathode material, the preparation method of which includes the following steps:

[0103] S1. Preparation of raw material slurry: Specifically, FeC2O4·2H2O is used as the iron source, phosphoric acid as the phosphorus source, sodium hydroxide as the sodium source, and glucose and carbon nanotubes as the carbon source. The iron, phosphorus, and sodium sources are added according to an elemental ratio of Fe / P = 0.75 and Na / P = 1.3. Water is added for dispersion, and the mixture is then milled. When the particle size distribution reaches D50 = 1 micrometer, polyvinyl acid, glucose, and carbon nanotubes are added, ensuring a Fe to glucose molar ratio of 10:1 and that the amount of carbon nanotubes added is the same as the mass of glucose. Milling continues until the particle size distribution reaches 0.5-0.6 micrometers.

[0104] S2, Preparation of the first precursor: Specifically, the slurry in S1 is spray-dried using a pressure spray dryer with an inlet air temperature of 220°C and an outlet temperature of 120°C.

[0105] S3. Preparation of the second precursor: The spray-dried precursor from S2 was heated to 420℃ in a vacuum box furnace at a heating rate of 5℃ / min and held at that temperature for 5 hours. The sintering atmosphere was high-purity nitrogen.

[0106] S4. Preparation of the third precursor: The second precursor was pulverized using an air jet mill to achieve a particle size distribution of D50 = 3 micrometers. 1.0% by weight of hydroxy fatty acid was added to the pulverized third precursor, and the mixture was then ground using a ball mill for 1 hour.

[0107] S5. High-temperature sintering: Specifically, the mixture of the third precursor in S4 and the hydroxy fatty acid is heated to 300°C at a heating rate of 2°C / min and held for 2 hours, and then heated to 600°C at a heating rate of 5°C / min and held for 8 hours in a vacuum box furnace.

[0108] The prepared positive electrode material was homogenized according to the mass ratio of active material slurry: active material: PVDF: SP: MWCNT=95: 3:1.5:0.5, and coated onto carbon-coated aluminum foil with a single-sided surface density of 150g / ㎡ to make a positive electrode sheet. The positive electrode sheet was then assembled with a hard carbon negative electrode sheet, a separator, an electrolyte, etc. to form a sodium-ion battery.

[0109] Comparative Example 2

[0110] This embodiment relates to a polyanionic cathode material, the preparation method of which includes the following steps:

[0111] S1. Preparation of raw material slurry: Specifically, FeC2O4·2H2O is used as the iron source, phosphoric acid as the phosphorus source, sodium hydroxide as the sodium source, and glucose and carbon nanotubes as the carbon source. The iron, phosphorus, and sodium sources are added according to an elemental ratio of Fe / P = 0.75 and Na / P = 1.3. Water is added for dispersion, and the mixture is then milled. When the particle size distribution reaches D50 = 1 micrometer, polyvinyl acid, glucose, and carbon nanotubes are added, ensuring a Fe to glucose molar ratio of 10:1 and that the amount of carbon nanotubes added is the same as the mass of glucose. Milling continues until the particle size distribution reaches 0.5-0.6 micrometers.

[0112] Preparation of the first precursor of S2: Specifically, the slurry of S1 is spray-dried using a pressure spray dryer with an inlet air temperature of 220°C and an outlet temperature of 120°C.

[0113] S3. Preparation of the second precursor: The spray-dried precursor from S2 was heated to 420℃ in a vacuum box furnace at a heating rate of 5℃ / min and held at that temperature for 5 hours. The sintering atmosphere was high-purity nitrogen.

[0114] S4. Preparation of the third precursor: The second precursor is pulverized using an air jet mill to achieve a particle size distribution of D50 = 3 micrometers.

[0115] S5. High-temperature sintering: Specifically, the mixture of the third precursor in S4 and the hydroxy fatty acid is heated to 300°C at a heating rate of 2°C / min and held for 2 hours, and then heated to 600°C at a heating rate of 5°C / min and held for 8 hours in a vacuum box furnace.

[0116] The prepared positive electrode material was homogenized according to the mass ratio of active material slurry: active material: PVDF: SP: MWCNT=95: 3:1.5:0.5, and coated onto carbon-coated aluminum foil with a single-sided surface density of 150g / ㎡ to make a positive electrode sheet. The positive electrode sheet was then assembled with a hard carbon negative electrode sheet, a separator, an electrolyte, etc. to form a sodium-ion battery.

[0117] Comparative Example 3

[0118] This embodiment relates to a polyanionic cathode material, the preparation method of which includes the following steps:

[0119] S1. Preparation of raw material slurry: Specifically, FeC2O4·2H2O is used as the iron source, phosphoric acid as the phosphorus source, sodium hydroxide as the sodium source, and glucose and carbon nanotubes as the carbon source. The iron, phosphorus, and sodium sources are added according to an elemental ratio of Fe / P = 0.75 and Na / P = 1.3. Water is added for dispersion, and the mixture is then milled. When the particle size distribution reaches D50 = 1 micrometer, polyvinyl acid, glucose, and carbon nanotubes are added, ensuring a Fe to glucose molar ratio of 10:1 and that the amount of carbon nanotubes added is the same as the mass of glucose. Milling continues until the particle size distribution reaches 0.5-0.6 micrometers.

[0120] S2, Preparation of the first precursor: Specifically, the slurry in S1 is spray-dried using a pressure spray dryer with an inlet air temperature of 220°C and an outlet temperature of 120°C.

[0121] S3. Preparation of the second precursor: 2.0% (by mass) of hydroxy fatty acid was added to the first precursor and milled using a ball mill for 1 hour. The mixture of the first precursor and hydroxy fatty acid was sintered in a vacuum box furnace, heated to 420°C at a heating rate of 5°C / min, and held at that temperature for 5 hours. The sintering atmosphere was high-purity nitrogen.

[0122] S4. Preparation of the third precursor: The second precursor is pulverized using an air jet mill to achieve a particle size distribution of D50 = 3 micrometers.

[0123] S5. High-temperature sintering: The third precursor is sintered by heating to 300°C at a heating rate of 2°C / min and holding for 2 hours, and then heating to 600°C at a heating rate of 5°C / min and holding for 8 hours.

[0124] The prepared positive electrode material was homogenized according to the mass ratio of active material slurry: active material: PVDF: SP: MWCNT=95: 3:1.5:0.5, and coated onto carbon-coated aluminum foil with a single-sided surface density of 150g / ㎡ to make a positive electrode sheet. The positive electrode sheet was then assembled with a hard carbon negative electrode sheet, a separator, an electrolyte, etc. to form a sodium-ion battery.

[0125] Comparative Example 4

[0126] This embodiment relates to a polyanionic cathode material, the preparation method of which includes the following steps:

[0127] S1. Preparation of raw material slurry: Specifically, FeC2O4·2H2O is used as the iron source, phosphoric acid as the phosphorus source, sodium hydroxide as the sodium source, and glucose and carbon nanotubes as the carbon source. The iron, phosphorus, and sodium sources are added according to an elemental ratio of Fe / P = 0.75 and Na / P = 1.3. Water is added for dispersion, and the mixture is then milled. When the particle size distribution reaches D50 = 1 micrometer, polyvinyl acid, glucose, and carbon nanotubes are added, ensuring a Fe to glucose molar ratio of 10:1 and that the amount of carbon nanotubes added is the same as the mass of glucose. Milling continues until the particle size distribution reaches 0.5-0.6 micrometers.

[0128] S2, Preparation of the first precursor: Specifically, the slurry in S1 is spray-dried using a pressure spray dryer with an inlet air temperature of 220°C and an outlet temperature of 120°C.

[0129] S3. Preparation of the second precursor: 1.0% (by weight) of hydroxy fatty acid was added to the first precursor and milled using a ball mill for 1 hour. The mixture of the first precursor and hydroxy fatty acid was sintered in a vacuum box furnace, heated to 420°C at a heating rate of 5°C / min, and held at that temperature for 5 hours. The sintering atmosphere was high-purity nitrogen.

[0130] S4. Preparation of the third precursor: The second precursor is pulverized using an air jet mill to achieve a particle size distribution of D50 = 3 micrometers.

[0131] The prepared positive electrode material was homogenized according to the mass ratio of active material slurry: active material: PVDF: SP: MWCNT=95: 3:1.5:0.5, and coated onto carbon-coated aluminum foil with a single-sided surface density of 150g / ㎡ to make a positive electrode sheet. The positive electrode sheet was then assembled with a hard carbon negative electrode sheet, a separator, an electrolyte, etc. to form a sodium-ion battery.

[0132] Comparative Example 5

[0133] This embodiment relates to a polyanionic cathode material, the preparation method of which includes the following steps:

[0134] S1. Preparation of raw material slurry: Specifically, FeC2O4·2H2O is used as the iron source, phosphoric acid as the phosphorus source, sodium hydroxide as the sodium source, and glucose and carbon nanotubes as the carbon source. The iron, phosphorus, and sodium sources are added according to an elemental ratio of Fe / P = 0.75 and Na / P = 1.3. Water is added for dispersion, and the mixture is then milled. When the particle size distribution reaches D50 = 1 micrometer, polyvinyl acid, glucose, and carbon nanotubes are added, ensuring a Fe to glucose molar ratio of 10:1 and that the amount of carbon nanotubes added is the same as the mass of glucose. Milling continues until the particle size distribution reaches 0.5-0.6 micrometers.

[0135] S2, Preparation of the first precursor: Specifically, the slurry in S1 is spray-dried using a pressure spray dryer with an inlet air temperature of 220°C and an outlet temperature of 120°C.

[0136] S3. Preparation of the second precursor: The mixture of the first precursor and hydroxy fatty acid was sintered in a vacuum box furnace, heated to 420°C at a heating rate of 5°C / min, and held at that temperature for 5 hours. The sintering atmosphere was high-purity nitrogen.

[0137] S4. Preparation of the third precursor: The second precursor is pulverized using an air jet mill to achieve a particle size distribution of D50 = 3 micrometers.

[0138] The prepared positive electrode material was homogenized according to the mass ratio of active material slurry: active material: PVDF: SP: MWCNT=95: 3:1.5:0.5, and coated onto carbon-coated aluminum foil with a single-sided surface density of 150g / ㎡ to make a positive electrode sheet. The positive electrode sheet was then assembled with a hard carbon negative electrode sheet, a separator, an electrolyte, etc. to form a sodium-ion battery.

[0139] This invention proposes a method for preparing NFPP, a sodium-ion battery cathode material with high electrode peel strength. Through process innovation and synergistic optimization of material design, it improves the problems of weak adhesion and easy powdering between NFPP and platinum material, as well as short cycle life. Its core advantage lies in improving the carbon coating effect through secondary sintering followed by surface etching to create pores, increasing its surface roughness (e.g., ...). Figure 1 As shown in Table 1, higher electrode peeling force is obtained, which also helps the electrolyte to wet better and increases cycle life. This provides a high peeling force and high performance solution for sodium-ion batteries in the field of large-scale energy storage (as shown in Table 1).

[0140] Comparing Application Example 1, Comparative Example 1, and Comparative Example 2, Application Example 1 exhibits higher peel strength and cycle life, attributed to excellent carbon coating during the first sintering and surface modification by hydroxy fatty acids during the second sintering process. In Comparative Example 1, the use of 1% hydroxy fatty acids did not affect the carbon coating process during the first sintering, but its surface activation effect during the second sintering was slightly lower than that of Application Example 1, resulting in lower peel strength. In Comparative Example 2, no hydroxy fatty acids were used for surface activation. While this did not affect carbon coating during the first sintering, the surface activation effect was significantly reduced during the second sintering, thus its peel strength was significantly lower compared to Application Example 1 and Comparative Example 1. Figure 2 ).

[0141] Application Example 1 and Comparative Example 3. Comparative Example 3 did not employ a two-stage sintering process; hydroxy fatty acids were added during the first sintering process. The oxygen-containing functional groups of the hydroxy fatty acids caused the particles to bond too tightly during sintering, thus affecting the carbon coating process. Therefore, although the surface was sufficiently rough, the carbon coating effect was poor, resulting in poor cycle performance. Figure 3 ).

[0142] Comparative Examples 1 and 4, and Comparative Examples 2 and 5. Similarly, Comparative Examples 4 and 5 did not employ secondary sintering; that is, carbon coating and surface activation pore formation were performed simultaneously in a single sintering process. This affected the carbon coating process, resulting in a lower cycle life compared to Comparative Examples 1 and 2. Furthermore, Comparative Examples 2 and 5 did not use hydroxy fatty acids, thus significantly reducing their surface activation pore formation effect, leading to a decrease in peel strength for both.

[0143] Table 1 Performance Test Results

[0144] Example Average peeling strength of positive electrode sheet (N / m) Cycling 300 cycles capacity retention rate (%) Example 1 106.18 99.31 Comparative Example 1 88.25 95.98 Comparative Example 2 28.13 95.45 Comparative Example 3 90.24 88.37 Comparative Example 4 78.77 91.97 Comparative Example 5 21.09 90.34

[0145] The above embodiments are merely specific examples of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A method for preparing a polyanionic cathode material with high electrode peel strength, characterized in that... Includes the following steps: S1. Preparation of raw material slurry: Iron source, carbon source, phosphorus source, sodium source and dispersant are dispersed in water as solvent under controlled temperature and pH environment, continuously stirred and ground to obtain raw material slurry; S2. Preparation of the first precursor: The above raw material slurry is dried to obtain the first precursor; S3. Preparation of the second precursor: The above precursor is pre-crystallized in a protective atmosphere to obtain the second precursor; S4. Preparation of the third precursor: The second precursor is pulverized, mixed with a surfactant, and ground to obtain the third precursor; S5. High-temperature sintering: The third precursor is sintered twice in a protective atmosphere to obtain the final polyanion cathode material.

2. The method for preparing polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S1, the temperature is controlled at 40-50℃.

3. The method for preparing polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S1, the pH is controlled at 5-7.

4. The method for preparing polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S3, the sintering temperature for pre-crystallization is 400-450℃, the heating rate is 1-3℃ / min, and the holding time is 8-12h; the protective atmosphere is nitrogen and / or argon.

5. The method for preparing polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S4, the surfactant is one or more of 3-hydroxypropionic acid, lactic acid, and ω-hydroxy fatty acid.

6. The method for preparing polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S5, the conditions for high-temperature sintering are: sintering temperature 580-600℃, heating rate 1-3℃ / min, and protective atmosphere of nitrogen and / or argon.

7. The method for preparing polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S1, the dispersant is one or more of the following: polyethylene glycol, polyacrylic acid, polyacryl alcohol, polyacrylamide, polyethylene oxide, polypyrrolidone, polymaleic acid, polyethylene glycol monomethyl ether, polyethylene glycol diacrylate, polyethylene glycol stearate, polyethylene glycol amine, polyethylene glycol sulfonic acid, polyethylene glycol phosphate, polyethylene glycol silane, polyethylene glycol block copolymer, and polyethylene glycol graft copolymer.

8. The method for preparing polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S1, The iron source is an organic iron source and / or an inorganic iron source, wherein the organic iron source is one or more of ferric citrate, ferric oxalate, ferric acetate, basic ferric acetate, and ferric acrylate. The carbon source is one or more of the following: citric acid, sodium citrate, isocitrate, glucose, gluconic acid, sucrose, graphene, carbon nanotubes, ascorbic acid, ketoglutarate, oxalic acid, tartaric acid, gluconic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, hypozonyltriacetic acid, ethylenediamine di-o-hydroxyphenylacetic acid, 8-hydroxyquinoline, phenanthroline, bipyridine, dithiocarbamate, sodium 1,2-dihydroxybenzene-3,5-disulfonic acid, acetylacetone, and N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid. The phosphorus source is one or more of the following: triethylphosphine, aminotrimethylphosphonic acid, hydroxyethylidene diphosphate, phosphoric acid, triphenylphosphine, triethyl phosphate, triphenyl phosphate, adenosine triphosphate, glyphosate, triphenylphosphine oxide, tri(chloroisopropyl) phosphate, tetraethyl pyrophosphate, phospholipid, hexamethylphosphoric acid triamine, phosphorous acid, hypophosphite, pyrophosphate, and metaphosphoric acid. The sodium source is one or more of the following: sodium carbonate, sodium hydroxide, sodium chloride, sodium sulfate, sodium nitrate, sodium silicate, sodium acetate, sodium monohydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, sodium oxalate, sodium benzoate, sodium citrate, sodium thiosulfate, sodium borohydride, sodium methoxide, sodium ethoxide, sodium stearate, monosodium glutamate, sodium perchlorate, and sodium valproate.

9. The method for preparing a polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S2, the drying method is one or more of the following: oven drying, spray drying, freeze drying, microwave drying, infrared drying, vacuum drying, and rotary flash drying.

10. The method for preparing a polyanionic cathode material with high electrode peel strength according to claim 1, characterized in that: In step S4, the mixing method is one or more of convection mixing, diffusion mixing, and shear mixing. The mixing process simultaneously realizes the pulverization process, and the pulverization method is one or more of crushing, impact pulverization, grinding pulverization, and air jet pulverization.

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