A polyanionic sodium-ion battery cathode material and a preparation method thereof

Abstract

The application provides a kind of polyanionic sodium ion battery positive electrode material and preparation method thereof, and relates to the technical field of sodium ion battery.The positive electrode material includes high compaction positive electrode material and long-acting sodium supplement agent;High compaction positive electrode material is Na a Fe b (PO4)2P2O7;Wherein, 3.8≤a≤4.4, 2.4≤b≤3.2;Long-acting sodium supplement agent is Na v Ni x Fe y Mn z Zn w O2;Wherein, 1.0≤v≤1.4, 0.20≤x≤0.30, 0.30≤y≤0.50, 0.10≤z≤0.30, 0.05≤w≤0.15;And x+y+z+w=1.The positive electrode material combines high compaction positive electrode material and long-acting sodium supplement agent.The sodium supplement agent can sacrifice sodium, and does not produce gas and does not decompose, ensuring the stability of the system.This combination ultimately realizes the compromise of high compaction density and high charge capacity, and improves the energy density of the battery.

Description

Technical Field

[0001] This invention relates to the field of sodium battery technology, and more specifically, to a polyanion-type sodium-ion battery cathode material and its preparation method. Background Technology

[0002] Against the backdrop of the global pursuit of carbon neutrality and energy structure transformation, new energy technologies, especially electrochemical energy storage technologies, play a crucial role. As the core carrier of electrochemical energy storage, the development of secondary batteries directly impacts the application of electric vehicles and large-scale energy storage systems. Among various battery systems, sodium-ion batteries, due to their abundant resources, low cost, and high safety, are considered a highly promising alternative technology in large-scale energy storage and two-wheeled vehicle power batteries, becoming a research hotspot in the new energy field.

[0003] Among the key materials for sodium-ion batteries, the cathode material plays a decisive role in the battery's energy density, safety, and cost. Polyanionic cathode materials, with their stable three-dimensional framework structure, exhibit excellent cycle stability and thermal stability. Sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7, abbreviated as NFPP) material, due to its unique structure, exhibits extremely high safety, such as no thermal runaway, puncture resistance and no fire, while also possessing characteristics such as resistance to frequent charge-discharge cycles, excellent low-temperature performance, and long lifespan. It is highly suitable for energy storage and power applications and is considered one of the ideal materials to replace traditional lead-acid batteries.

[0004] However, NFPP materials still face challenges in commercialization. Their main drawback lies in their lower compaction density and energy density compared to mature materials like lithium iron phosphate. This limits their application in scenarios requiring high volumetric energy density and ultimately impacts their cost-effectiveness. To address these issues, existing technologies have explored various approaches. For example, some solutions attempt to improve the compaction density of NFPP materials through specific precursor preparation methods, achieving a compaction density of 2.39 g / cm³. 3 However, the overall energy density of the battery packs produced by this method still needs further improvement. Another approach involves adding organic chain-like sodium supplements to compensate for the initial cycle capacity loss of the cathode material, thereby increasing the discharge capacity of the cell. However, these sodium supplements decompose and generate gas during cycling, negatively impacting the long-term cycle performance and safety of the battery.

[0005] In summary, existing NFPP cathode materials and their preparation technologies still have shortcomings. On the one hand, further research is needed on how to optimize the process at the precursor preparation stage to obtain NFPP materials with higher compaction density and discharge capacity. On the other hand, while existing sodium supplementation technology can improve capacity to some extent, its decomposition gas generation and weak conductivity hinder the practical application of batteries. Therefore, how to effectively combine material modification and cell capacity compensation technology to simultaneously improve the compaction density of NFPP materials and the energy density of the cell without sacrificing battery safety and stability is a major technical challenge currently facing this field. In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a polyanionic sodium-ion battery cathode material and its preparation method. The polyanionic sodium-ion battery cathode material is prepared by high-pressure compacted Na... a Fe b (PO4)2P2O7 as the main component and a specific Na+ that does not produce gas and can be used for sacrificial sodium supplementation. v Ni x Fe y Mn z Zn w The combination of O2 and sodium supplementation maintains high safety while also achieving high compaction density and high charging capacity, thereby improving battery energy density.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] In a first aspect, the present invention provides a polyanionic sodium-ion battery cathode material, comprising a high-pressure compaction cathode material and a long-lasting sodium replenishing agent;

[0009] The high-pressure positive electrode material is Na. a Fe b (PO4)2P2O7; where 3.8≤a≤4.4, 2.4≤b≤3.2;

[0010] The long-acting sodium supplement is Na v Ni x Fe y Mn z Zn w O2; where 1.0≤v≤1.4, 0.20≤x≤0.30, 0.30≤y≤0.50, 0.10≤z≤0.30, 0.05≤w≤0.15; and x+y+z+w=1.

[0011] In an optional embodiment, the long-acting sodium supplement contains 1.05 ≤ v ≤ 1.25; and / or,

[0012] The long-lasting sodium replenishing agent accounts for 1% to 10% by mass in the polyanionic sodium-ion battery cathode material; or, 2% to 5% by mass.

[0013] The long-acting sodium supplement has a particle size Dv 50 1μm~6μm; or 2μm~4μm; and / or,

[0014] The particle size Dv of the high-pressure positive electrode material 50 The range is 1.5μm to 7.5μm; or 2μm to 5μm.

[0015] Secondly, the present invention provides a method for preparing a polyanionic sodium-ion battery cathode material as described in the foregoing embodiments, comprising:

[0016] A high-pressure positive electrode material and a long-lasting sodium replenishing agent are prepared separately; and the high-pressure positive electrode material and the long-lasting sodium replenishing agent are mixed to obtain the polyanionic sodium-ion battery positive electrode material.

[0017] In an optional embodiment, the high-pressure positive electrode material is prepared by stirring a first precursor, a first sodium source, a carbon source, and an acidic solution, followed by granulation and sintering under an inert atmosphere; wherein the first precursor is nano-sized Na. a1 Fe b1 P c1 O d1 ·eH₂O, 0<a₁≤2.5, 2.4≤b₁≤3.2, 3.2≤c₁≤4.3, 3.5c₁≤d₁≤4c₁, 0<e≤4; and / or,

[0018] The long-acting sodium supplement is prepared by mixing a second precursor with a first sodium source and sintering the mixture in an air atmosphere; the second precursor is Ni. x Fe y Mn z Zn w (OH)2.

[0019] In an optional embodiment, the first sodium source used in the preparation of the high-pressure positive electrode material and the long-acting sodium supplement includes at least one of Na₂CO₃, CH₃COONa, and Na₂C₂O₄; and / or,

[0020] The carbon source includes at least one selected from glucose, PEG, sucrose, and citric acid; and / or,

[0021] The acidic solution is a mixed solution of an acidic reagent and a dispersant; wherein the acidic reagent includes at least one of phosphoric acid, oxalic acid and nitric acid; and / or the dispersant includes at least one of PVP, ethylene glycol and sodium hexametaphosphate.

[0022] In an optional embodiment, the stirring process during the preparation of the high-pressure positive electrode material further includes: replenishing the acidic solution during stirring to adjust the pH to 2.5 ± 0.5, and ensuring that the particle size of the mixture is no greater than 200 nm; and / or,

[0023] The granulation is spray granulation; the parameters of the spray granulation include: air flow rate of 50 to 200 times the liquid flow rate; and / or, inlet air temperature of 260℃ to 280℃; and / or, outlet air temperature of 90℃ to 110℃; and / or, outlet particle size of Dv. 10 =1.0μm~3.0μm, Dv 50 =3.0μm~8.0μm, Dv 90 =8μm~28μm; and / or,

[0024] The inert atmosphere sintering includes: A. First stage: heating to 300℃~400℃ at a heating rate of 1℃ / min~3℃ / min; B. Second stage: holding at 300℃~400℃ for 2 hours~4 hours; C. Third stage: heating to 500℃~600℃ at a heating rate of 3℃ / min~5℃ / min; D. Fourth stage: holding at 500℃~600℃ for 6 hours~12 hours.

[0025] In an optional embodiment, the method for preparing the first precursor includes:

[0026] The second sodium source, iron source, and phosphorus source were mixed under an inert atmosphere, and an oxidant solution was added to carry out a precipitation reaction to obtain the first precursor.

[0027] In an optional embodiment, the second sodium source used in the preparation of the first precursor includes at least one of Na₂CO₃, NaH₂PO₄, Na₃PO₄, and Na₄P₂O₇; and / or,

[0028] The particle size distribution of the first precursor is 40nm ≤ DV50 ≤ 200nm; and / or,

[0029] The phosphorus source includes at least one of NH4H2PO4 and H3PO4; and / or,

[0030] The iron source includes at least one of FeC2O4, FeSO4, and Fe(NO3)3; and / or,

[0031] The oxidant includes at least one of hydrogen peroxide, nitric acid, and sodium peroxide.

[0032] In an optional embodiment, the sintering conditions of the long-acting sodium supplement include: a sintering temperature of 860℃~980℃; and / or, a sintering time of 8 hours~12 hours; and / or,

[0033] The preparation of the long-acting sodium supplement further includes: after sintering, subjecting the sintered material to air milling at 0.55 MPa to 0.75 MPa; and / or,

[0034] The preparation of the second precursor includes: preparing a mixed solution of nickel source, zinc source, iron source and manganese source, and performing complexation co-precipitation of the mixed solution with ammonia water and alkaline solution under an inert atmosphere to obtain the second precursor.

[0035] In an optional embodiment, the metal ion concentration of the mixed solution is 90 g / L to 120 g / L; and / or,

[0036] The nickel source includes nickel sulfate; and / or,

[0037] The zinc source includes zinc sulfate; and / or,

[0038] The iron source includes ferrous sulfate; and / or,

[0039] The manganese source includes manganese sulfate.

[0040] Thirdly, the present invention provides a battery comprising the polyanionic sodium-ion battery cathode material as described in the foregoing embodiments; or, the polyanionic sodium-ion battery cathode material prepared according to the preparation method described in any of the foregoing embodiments.

[0041] Fourthly, the present invention provides an electrical device including a battery as described in the foregoing embodiments.

[0042] This invention provides a polyanionic sodium-ion battery cathode material and its preparation method. The polyanionic sodium-ion battery cathode material incorporates a high-compact cathode material, Na... a Fe b (PO4)2P2O7 and specific components of long-acting sodium supplement Na v Ni x Fe y Mn z Zn w Combined with O2.

[0043] Among them, Na a Fe b The (PO4)2P2O7 component can provide a higher material compaction density (e.g., ≥2.3 g / cm³). 3 This helps improve the volumetric energy density of batteries. Long-lasting sodium supplement Na... v Ni x Fe y Mn z Zn wO2 employs a specific elemental molar ratio, particularly by controlling the ratio of Zn to Fe, so that Zn can fully stimulate the redox reaction of Fe. This design gives the sodium supplement high initial capacity (e.g., ≥200 mAh / g) and extremely low capacity retention (e.g., decaying to less than 5% after 100 cycles), making it suitable for providing "sacrificial" sodium supplementation in the early stages of battery cycling to compensate for capacity loss in the first cycle.

[0044] The key is that this specific component of the long-lasting sodium replenisher does not decompose or generate gas when providing sodium replenishment, thus having no adverse effect on the stability of the battery system. Simultaneously, its operating voltage (close to 4.4V) is compatible with the safe voltage of the high-pressure positive electrode material, and it possesses good conductivity and Na+ ion transport capability, preventing any deterioration of the battery's electronic and ionic conductivity.

[0045] Therefore, this combination enables the final cathode material to achieve both high compaction density and high charging capacity, thereby improving the battery's energy density and overcoming the defects of gas generation and instability in existing sodium replenishment technologies, while maintaining the high safety of polyanionic materials. Attached Figure Description

[0046] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 This is a SEM image of the high-voltage positive electrode material in Example 1 of this application;

[0048] Figure 2 This is a SEM image of the long-acting sodium supplement material in Example 1 of this application;

[0049] Figure 3 SEM image of 97.2% by mass of high-voltage positive electrode material mixed with 2.8% by mass of long-acting sodium supplement material in Example 1 of this application;

[0050] Figure 4 The above are charge-discharge curves for Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0051] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0052] This application provides a polyanionic sodium-ion battery cathode material, comprising two parts: a high-pressure cathode material and a long-lasting sodium replenishing agent.

[0053] (1) High-pressure positive electrode material:

[0054] This is the main carrier for the storage and release of sodium ions during battery charging and discharging.

[0055] Its chemical formula is Na a Fe b (PO4)2P2O7; where 3.8≤a≤4.4, 2.4≤b≤3.2.

[0056] This material is a complex of sodium (Na) and iron (Fe) phosphates (PO4) and pyrophosphates (P2O7). Because it contains two phosphate anions (PO4 and P2O7), this material is called a "polyanionic" material.

[0057] In chemical formulas, subscripts a and b represent molar coefficients. For example, a Na... 4.15 Fe 2.95 (PO4)2P2O7, with a=4.15 (within 3.8-4.4) and b=2.95 (within 2.4-3.2), meets the chemical formula requirements for this component.

[0058] The term "high compaction" is a functional description. It means that the component material has a higher compaction density (i.e., a higher mass of material per unit volume).

[0059] Polyanionic materials (such as NFPP) in cathode materials typically have the advantages of structural stability and high safety. The "high-compaction" characteristic makes the battery electrodes made from this material more dense, which helps to improve the volumetric energy density of the battery (i.e., the battery of the same size can store more energy).

[0060] (2) Long-acting sodium supplements:

[0061] It is an auxiliary additive for positive electrode materials. Its chemical formula is Na. v Ni x Fe y Mn z Zn wO2; where 1.0≤v≤1.4, 0.20≤x≤0.30, 0.30≤y≤0.50, 0.10≤z≤0.30, 0.05≤w≤0.15; and x+y+z+w=1.

[0062] This is a composite oxide (O2) containing five metallic elements: sodium (Na), nickel (Ni), iron (Fe), manganese (Mn), and zinc (Zn).

[0063] The subscripts in the chemical formula are molar ratio coefficients, such as V representing the sodium content, ranging from 1 to 1.4. The formula x+w+y+z=1 specifies that the overall molar ratio of the four transition metals is 1.

[0064] For example, a substance is Na 1.1 Ni 0.25 Fe 0.40 Mn 0.25 Zn 0.1 O2, whose coefficients for each element are all within the specified range, and 0.25+0.40+0.25+0.1=1, meets the requirements for this component.

[0065] The aforementioned "long-lasting sodium replenisher" is its functional description. During the first operation of a sodium-ion battery, some (approximately 15%) of the sodium ions embedded in the hard carbon negative electrode will be unable to escape, and a solid electrolyte interface (SEI) will form on its surface. These two processes will irreversibly consume a portion of the sodium ions, leading to a decrease in the total battery capacity.

[0066] The function of the aforementioned "sodium replenisher" is to release additional (or "sacrificial") sodium ions during the first charge to compensate for this loss. The specific elemental composition and ratio range of this sodium replenisher (especially the ratio of Zn to Fe) give it the characteristics of high first-cycle capacity (able to replenish sodium) and rapid decay (it quickly becomes ineffective after sodium replenishment and does not affect subsequent cycles).

[0067] Its advantage lies in the fact that it can provide sodium replenishment in the early stage of cycling, and it does not decompose or produce gas, so it has no impact on the stability of the battery system and overcomes the problems of gas production and safety impact of existing sodium replenishment technologies.

[0068] This long-lasting sodium replenisher achieves a synergistic effect of high-efficiency sodium replenishment and high stability. Its key advantage lies in its non-decomposition and gas-generating properties during operation; instead, it achieves sacrificial sodium replenishment through natural lattice collapse and cyclic decay, a crucial factor for NFPP material systems requiring long cycling. This sodium replenisher has approximately twice the capacity of the host material, satisfying sodium replenishment requirements while avoiding the gas generation or reduced conductivity issues often associated with other higher-capacity sodium replenishers. Furthermore, this sodium replenisher (itself a poorly cycling sodium-ionized oxygen cathode) exhibits superior electronic conductivity compared to the host material and inherently contains sodium. +The channel does not affect the electronic conductivity and ion transport of the system. More importantly, its high excitation voltage (close to 4.4V) is highly compatible with the 4.4V safety voltage of the high-pressure positive electrode material, ensuring that the two work together, but also making it unsuitable for layered sodium electrode materials with lower operating voltages (such as 4.0V).

[0069] This cathode material achieves complementary advantages by combining the two components mentioned above. First, the high-compact cathode material (component A) ensures high volumetric energy density and high safety by utilizing its high-compact characteristics and high safety. Second, the long-lasting sodium replenisher (component B) replenishes sodium ions during the first cycle, compensating for the initial capacity loss of the main material, thereby improving the battery's charging capacity and energy density while reducing battery costs. By using a sodium replenisher (component B) with a specific elemental ratio, the process of replenishing sodium is ensured to be gas-free, resolving the compatibility issue between the sodium replenisher and the high-safety polyanionic material system, resulting in a material that combines high energy density and high stability.

[0070] In some embodiments, the long-acting sodium supplement has a concentration of 1.05 ≤ v ≤ 1.25. For example, it can be 1.05, 1.10, 1.15, 1.20, 1.25, etc.

[0071] In some embodiments, the long-lasting sodium supplement agent accounts for 1% to 10% of the mass percentage of the polyanionic sodium-ion battery cathode material (e.g., it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.); or, the mass percentage is 2% to 5%.

[0072] The mass percentage of the aforementioned long-acting sodium supplement in the positive electrode material of polyanionic sodium-ion batteries is limited to 1% to 10% (preferably 2% to 5%). This range is a key balance point for achieving the best synergistic effect.

[0073] This long-lasting sodium replenisher, through a specific elemental ratio design (especially the Zn and Fe ratio), achieves a sacrificial sodium replenishment characteristic of high initial capacity (≥200 mAh / g) and low capacity retention (≤5% after 100 cycles). If the amount added is too small (e.g., below 1%), the total capacity provided by the sodium replenisher will be insufficient to compensate for the capacity loss caused by the low initial efficiency of the main material, resulting in an insignificant sodium replenishment effect. Conversely, if the amount added is too large (e.g., above 10%), the content of the main cathode material will be reduced accordingly, and the battery's main capacity provision will become overly dependent on this poorly performing sodium replenisher, leading to a rapid decrease in energy density in the later stages of cycling and a deterioration in overall cycle performance. Therefore, the range of 1% to 10% (especially 2% to 5%) aims to ensure sufficient sodium replenishment while minimizing the negative impact on the battery's energy density and cycle life in the later stages of cycling.

[0074] In some embodiments, the particle size Dv of the long-acting sodium supplement 50 The value can be 1μm to 6μm (for example, it can be 1, 2, 3, 4, 5, 6, etc.); or 2μm to 4μm.

[0075] The particle size Dv50 of the aforementioned long-acting sodium supplement is limited to 1μm~6μm (preferably 2μm~4μm), which is a result of balancing preparation cost and electrochemical performance. If the particle size is too small (e.g., less than 1μm), a large amount of energy will be required for crushing during preparation, resulting in excessively high costs. At the same time, an excessively small particle size (high specific surface area) may also exacerbate side reactions with the electrolyte, which is detrimental to the stability of the battery cell system. Conversely, if the particle size is too large (e.g., greater than 6μm), the sodium ion extraction path will become longer, resulting in a poorer sodium supplementation effect and a reduction in the capacity that the sodium supplement can exert.

[0076] In some embodiments, the particle size Dv of the high-pressure positive electrode material 50 The range is 1.5μm to 7.5μm (for example, it can be 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, etc.); or 2μm to 5μm.

[0077] This application provides a method for preparing a polyanionic sodium-ion battery cathode material as described in the foregoing embodiments, including:

[0078] Step S100: Prepare high-pressure positive electrode material and long-acting sodium supplement.

[0079] The above steps constitute the preparation stage of the preparation method. It clarifies that the two key components of the final product (i.e., the cathode material): the "high-pressure compaction cathode material" and the "long-lasting sodium supplement" are not generated simultaneously in a reactor, but must first be manufactured as two separate substances.

[0080] This step involves two completely separate production processes:

[0081] (1) Process A: Through a series of chemical reactions and physical treatments, "high-pressure positive electrode material" (i.e., Na) is produced. a Fe b (PO4)2P2O7 powder.

[0082] (2) Process B: Through another series of independent chemical reactions and physical processes, a "long-acting sodium supplement" (i.e., Na) is produced. v Ni x Fe y Mn z Zn w O2 powder.

[0083] Step S200: Mix the high-pressure positive electrode material and the long-lasting sodium supplement to obtain the polyanion-type sodium-ion battery positive electrode material.

[0084] The above steps are the final compounding or finished product preparation steps, which combine the two separate powders obtained in step S100 into a single product. Specifically, this can be a physical mixing process. The purpose of this process is to disperse the two powder particles (the main material particles and the sodium supplement particles) together as uniformly as possible at the microscopic level.

[0085] This step can be achieved using conventional powder mixing equipment. For example, two powders are added to a mixing device in a specific mass ratio (such as the ratio described above, for example, 98% of the main material and 2% of the sodium supplement) and mechanically stirred.

[0086] The equipment that can be used may include, but is not limited to, ball mills (such as dry ball mills), V-type mixers, three-dimensional motion mixers, or high-speed stirrers. The goal is to achieve uniform mixing and avoid localized enrichment or deficiency of sodium supplement.

[0087] This preparation method yielded the final product, a "polyanionic sodium-ion battery cathode material." This is a macroscopically homogeneous powder mixture containing Na... a Fe b (PO4)2P2O7 particles and Na v Ni x Fe y Mn z Zn w O2 particles. The advantage of this step is that it allows for precise control of the component ratios in the final product. Through physical mixing, the amount of long-acting sodium supplement added can be controlled very precisely (e.g., within the range of 1% to 10% or 2% to 5%), which is key to achieving the desired electrochemical performance (such as compensating for first-cycle capacity loss without affecting cycle life).

[0088] In some embodiments, the high-pressure positive electrode material is prepared by stirring a first precursor, a first sodium source, a carbon source, and an acidic solution, followed by granulation and sintering under an inert atmosphere; wherein the first precursor is nano-sized Na. a1 Fe b1 P c1 O d1 ·eH2O, 0<a1≤2.5, 2.4≤b1≤3.2, 3.2≤c1≤4.3, 3.5c1≤d1≤4c1, 0<e≤4.

[0089] The first step described above is the preparation of a slurry or suspension of the high-pressure positive electrode material. This involves mixing all solid raw materials and functional liquids in a mixing tank. This step treats four key components: a first precursor, which forms the main framework of the material and provides iron (Fe), phosphorus (P), and a portion of sodium (Na). This precursor is specifically defined as "nanoscale," meaning its original particle size is very small and it has a specific range of elemental proportions (specifically, the range of a1, b1, c1, d1, e). A first sodium source, used to supplement sodium, ensuring the sodium content (a) in the final product reaches the target range of 3.8–4.4%. A carbon source, an organic compound (such as glucose or sucrose), serves two purposes: first, to provide reducing carbon to reduce the trivalent Fe in the first precursor to divalent Fe during the sintering reaction; and second, to transform it into conductive carbon during high-temperature pyrolysis, which then coats the material surface. An acidic solution is a mixed solution of an acidic reagent (phosphoric acid, oxalic acid, etc.) and a dispersant (ethylene glycol, sodium hexametaphosphate, etc.) used to disperse the aforementioned solid particles, especially nanoscale precursors. "Stirring treatment" refers to the process of uniformly mixing these components in a liquid medium (such as pure water) using mechanical force (such as high-speed stirring).

[0090] After stirring, a uniform, stable, and non-agglomerated suspension (or slurry) is obtained.

[0091] By using "nanoscale" precursors, various elements can be uniformly mixed at the atomic or nanoscale, laying the foundation for subsequent sintering to form pure-phase, low-impurity materials.

[0092] The addition of an "acidic solution" is crucial, as the acidic environment can effectively prevent nanoparticles from agglomerating or growing during the mixing process, thus maintaining their nanoscale properties.

[0093] Furthermore, the slurry obtained through this "acid-dissolving and stirring" treatment has a sufficiently small particle size and is well dispersed, so it can be used directly for the next step of granulation without the need for a "sand milling" process, which simplifies the process and reduces costs.

[0094] Then, the liquid slurry obtained in the previous step is transformed into dry solid particles with a specific particle size distribution. That is, the slurry is dried and shaped to obtain a dry composite particle powder composed of multiple raw materials.

[0095] The aforementioned "granulation" process ensures that within each micron-sized particle, the nano-sized precursor, sodium source, and carbon source are uniformly mixed. This is crucial for the uniformity of the subsequent sintering reaction and can prevent elemental segregation.

[0096] The aforementioned "inert atmosphere sintering" is the final chemical reaction and crystal growth step, transforming the particles into the final product at high temperature. In other words, the composite particles obtained in the previous step are heated at high temperature in an "inert atmosphere."

[0097] "Inert atmosphere" refers to a gaseous environment that contains no oxygen or has a very low oxygen content, such as using nitrogen (N2) or argon (Ar) for protection, thus obtaining the final "high-pressure positive electrode material".

[0098] At high temperatures in this step, the carbon source is pyrolyzed to form a conductive carbon layer, and the precursor, sodium source, and partially pyrolyzed carbon react to form the target crystalline phase structure.

[0099] The aforementioned "inert atmosphere" is crucial to this process. Because the material contains iron (Fe), it is easily over-oxidized when exposed to air (oxygen) at high temperatures, leading to the formation of non-target impurity phases. The inert atmosphere protects the valence state of iron, ensuring the formation of the target product (Na). a Fe b The formation of (PO4)2P2O7. Combined with the nanoscale precursor from the first step, the material prepared by this method has the advantages of fewer impurities and higher compaction density.

[0100] In some embodiments, the long-acting sodium supplement is prepared by mixing a second precursor with a first sodium source and then sintering the mixture in an air atmosphere; the second precursor is Ni. x Fe y Mn z Zn w (OH)2.

[0101] The first step involves mixing the raw materials for preparing a long-acting sodium supplement. This can be done by physically mixing the second precursor and the first sodium source, both solid powder raw materials.

[0102] The second precursor is a complex metal hydroxide that provides all the transition metal elements (Ni, Fe, Mn, Zn) required for the final product. The first sodium source provides sodium (Na).

[0103] A homogeneous mixture of the two powders is obtained by mixing.

[0104] Specifically, the two reactant powders can be brought into full contact through methods including (but not limited to) dry ball milling or V-type mixers.

[0105] After mixing the materials, a solid-phase reaction is carried out at high temperature to synthesize the final product. Specifically, the mixed powder obtained in the previous step can be heated at high temperature in an "air atmosphere".

[0106] The aforementioned "air atmosphere" is distinct from the "inert atmosphere" used in the preparation of high-pressure compaction materials, thus yielding the final "long-lasting sodium supplement," which is a composite metal oxide.

[0107] This step utilizes oxygen in an "air atmosphere" as a reactant to react the metal hydroxide precursor and the sodium source at high temperature, transforming them into a thermodynamically more stable oxide crystalline phase structure. This is a standard solid-phase synthesis method for preparing composite oxide materials.

[0108] In some embodiments, the first sodium source used in the preparation of the high-pressure positive electrode material and the long-acting sodium supplement includes at least one of Na2CO3, CH3COONa and Na2C2O4.

[0109] In some embodiments, the carbon source includes at least one of glucose, PEG, sucrose, and citric acid.

[0110] In some embodiments, the acidic solution is a mixed solution of an acidic reagent and a dispersant; wherein the acidic reagent includes at least one of phosphoric acid, oxalic acid, and nitric acid; and / or, the dispersant includes at least one of PVP, ethylene glycol, and sodium hexametaphosphate.

[0111] In some embodiments, the stirring process in the preparation of the high-pressure positive electrode material further includes: adding the acidic solution during stirring to adjust the pH to 2.5±0.5, and ensuring that the particle size of the mixture is no greater than 200nm.

[0112] In some embodiments, the granulation is spray granulation; the parameters of the spray granulation include: an air flow rate of 50 to 200 times the liquid flow rate; and / or, an inlet air temperature of 260°C to 280°C; and / or, an outlet air temperature of 90°C to 110°C; and / or, an outlet particle size of Dv. 10 =1.0μm~3.0μm, Dv 50 =3.0μm~8.0μm, Dv 90 =8μm~28μm.

[0113] In some embodiments, the inert atmosphere sintering includes:

[0114] A. The first stage is a slow heating stage, specifically heating to 300℃~400℃ at a heating rate of 1℃ / min~3℃ / min (for example, it can be 1℃ / min, 1.5℃ / min, 2℃ / min, 3℃ / min, etc.); for example, it can be 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, etc.

[0115] B. The second stage is the first heat preservation stage, which involves heat preservation at 300℃~400℃ (for example, it can be 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, etc.) for 2 hours to 4 hours; for example, it can be 2 hours, 3 hours, 4 hours, etc.

[0116] C. The third stage is the rapid heating stage, where the temperature is increased to 500℃~600℃ at a rate of 3℃ / min~5℃ / min (for example, it can be 3℃ / min, 3.2℃ / min, 3.4℃ / min, 3.6℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, etc.); for example, it can be 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, etc.

[0117] D. The fourth stage is the second heat preservation stage, which involves heat preservation at 500℃~600℃ (for example, it can be 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, etc.) for 6 hours to 12 hours. For example, it can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.

[0118] In some embodiments, the method for preparing the first precursor includes:

[0119] The second sodium source, iron source, and phosphorus source were mixed under an inert atmosphere, and then an oxidant solution was added to carry out a precipitation reaction to obtain the first precursor.

[0120] In some embodiments, the second sodium source used in the preparation of the first precursor includes at least one of Na2CO3, NaH2PO4, Na3PO4, and Na4P2O7.

[0121] In some embodiments, the particle size distribution of the first precursor is 40 nm ≤ D V50 ≤200nm.

[0122] The particle size distribution D of the first precursor mentioned above V50 Limiting the particle size to the range of 40nm to 200nm represents an optimized range that balances sintering performance and manufacturing costs. If the particle size is too large (e.g., DV50 exceeding 200nm), the uniformity of elemental mixing within the particles decreases, making elemental segregation more likely during subsequent high-temperature sintering, leading to an increase in impurities and affecting the final material's compaction density. On the other hand, while theoretically smaller particle sizes (closer to atomic-level mixing) are more beneficial for subsequent solid-state reactions, excessively small particle sizes (e.g., DV50 exceeding 200nm) can also negatively impact the final material's compaction density. 50Below 40nm, the preparation process becomes extremely difficult, requiring stringent reaction conditions for control, resulting in excessively high preparation costs. Therefore, the 40nm to 200nm range represents a balance between achieving good sintering activity, avoiding segregation, and maintaining process feasibility and economy.

[0123] In some embodiments, the phosphorus source includes at least one of NH4H2PO4 and H3PO4.

[0124] In some embodiments, the iron source includes at least one of FeC2O4, FeSO4, and Fe(NO3)3.

[0125] In some embodiments, the oxidant includes at least one of hydrogen peroxide, nitric acid, and sodium peroxide.

[0126] In some embodiments, the sintering conditions of the long-acting sodium supplement include: a sintering temperature of 860°C to 980°C (e.g., 860°C, 880°C, 900°C, 920°C, 950°C, 980°C); and / or a sintering time of 8 hours to 12 hours (e.g., 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.).

[0127] In some embodiments, the preparation of the long-acting sodium supplement further includes: after sintering, the sintered material is subjected to air milling at 0.55 MPa to 0.75 MPa (for example, 0.55 MPa, 0.60 MPa, 0.65 MPa, 0.70 MPa, 0.75 MPa, etc.).

[0128] In some embodiments, the preparation of the second precursor includes: preparing a mixed solution of a nickel source, a zinc source, an iron source and a manganese source, and then, under an inert atmosphere, performing complexation co-precipitation of the mixed solution with ammonia and an alkaline solution to obtain the second precursor.

[0129] In some embodiments, the metal ion concentration of the mixed solution is 90 g / L to 120 g / L. For example, it can be 90 g / L, 100 g / L, 110 g / L, 120 g / L, etc.

[0130] In some embodiments, the nickel source includes nickel sulfate.

[0131] In some embodiments, the zinc source includes zinc sulfate.

[0132] In some embodiments, the iron source includes ferrous sulfate.

[0133] In some embodiments, the manganese source includes manganese sulfate.

[0134] This application also provides a battery comprising the polyanionic sodium-ion battery cathode material as described in the foregoing embodiments; or, the polyanionic sodium-ion battery cathode material prepared according to the preparation method described in any of the foregoing embodiments.

[0135] The aforementioned battery can be a sodium-ion battery because its core material is a "polyanionic sodium-ion battery positive electrode material." As a battery, its structure typically includes, but is not limited to, a positive electrode (positive electrode sheet), a negative electrode (negative electrode sheet), an electrolyte, and a separator. The core feature of this battery lies in its positive electrode: the positive electrode (or positive electrode sheet) contains the aforementioned polyanionic sodium-ion battery positive electrode material. In other words, the active material of this positive electrode is a composite material composed of a high-compact positive electrode material and a long-lasting sodium-replenishing agent. Alternatively, the positive electrode may be a positive electrode material ultimately prepared through the aforementioned preparation methods (e.g., including steps such as "acid dissolution and stirring," "inert atmosphere sintering," "air atmosphere sintering," and "mixing").

[0136] This application also provides an electrical device, including a battery as described in the foregoing embodiments.

[0137] The aforementioned "electrical equipment" refers to any end product or system that includes or utilizes the aforementioned battery as its power source, energy storage unit, or backup power source. The core feature of this equipment is its integrated sodium-ion battery. Due to the high safety, high energy density, long lifespan, and resistance to frequent charge-discharge of the cathode material used in this battery, it is particularly suitable for applications with high requirements for safety and cost. Specific categories of "electrical equipment" may include, but are not limited to: energy storage systems: such as grid-scale containerized energy storage systems, industrial and commercial energy storage cabinets, residential energy storage devices (household energy storage), uninterruptible power supplies (UPS) or backup power for communication base stations; electric vehicles: especially in safety- and cost-sensitive areas, such as two-wheeled vehicles (e.g., electric bicycles, electric motorcycles, electric mopeds) or low-speed electric vehicles (e.g., golf carts, sightseeing vehicles); other lead-acid battery alternatives: any equipment that traditionally uses lead-acid batteries and is now seeking a more environmentally friendly and higher-performance alternative, such as electric forklifts or portable power stations.

[0138] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0139] Table 1. Summary of Examples and Comparative Examples

[0140]

[0141] Example 1

[0142] In this embodiment, a sodium-ion battery cathode material was prepared.

[0143] Experimental methods:

[0144] S1, Synthesis of the first precursor (Na) 2.03 Fe 2.95 P4O 15.11 ·2.74H2O):

[0145] (1) FeSO4·7H2O crystals were stirred with pure water at room temperature to prepare Fe 2+ A salt solution with a concentration of 60±5 g / L is prepared by adding dilute sulfuric acid to adjust the pH of the salt solution to 4.0±0.5 to prevent oxidation; this solution is denoted as solution A. A 10 L oxidant solution of dilute sulfuric acid and hydrogen peroxide is prepared by mixing 1.5 L dilute sulfuric acid (1.5 mol / L) with 7.5 L hydrogen peroxide (15 wt.%); this solution is denoted as solution B. A solution with a P concentration of 30±0.5 g / L is prepared using Na4P2O7; this solution is denoted as solution C. Solution C is maintained at 50~60℃.

[0146] (2) Add 100L of solution A to the reactor as the bottom liquid. Purge nitrogen gas into the bottom of the reactor until the oxygen content is <5000ppm. Then, turn on the water bath jacket heating, setting the temperature to 55℃ and the stirring speed to 500r / min. Rapidly add solution C to the reactor, ensuring the molar ratio of the added phosphorus source to the iron source in the bottom liquid satisfies Fe:P = 2.95:4. Then, slowly add solution B, turning off the nitrogen gas and continuing stirring until the pH of the suspension in the reactor reaches 4.0~6.0. Centrifuge, wash, and dry the resulting slurry to obtain the first precursor, Na. a1 Fe 2.95 P4O d1 ·eH2O. In the first precursor, a1=2.03, d1=15.11, and e=2.74, which is Na. 2.03 Fe 2.95 P4O 15.11 ·2.74H2O.

[0147] S2, Preparation of high-pressure positive electrode material (Na) 4.15 Fe 2.95 (PO4)2P2O7):

[0148] (1) The first precursor in S1 and Na2CO3, glucose, oxalic acid, and ethylene glycol (prepared according to design values) are mixed and stirred evenly in pure water to obtain a suspension. Na2CO3 is used in the suspension. 2.03 Fe 2.95 P4O 15.11The total Na and Fe contents in 2.74H2O and Na2CO3 conform to the molar ratio of Na:Fe = 4.15: 2.95; oxalic acid was added to make the pH of the suspension 2.5 ± 0.5; ethylene glycol was added at 0.5% of the total weight of the suspension.

[0149] (2) The suspension obtained in (1) was spray-dried using a two-flow spray dryer with the inlet air temperature set at 270°C, the outlet air temperature set at 105°C, and the compressed air flow rate set at 4.8 m³ / s. 3 / h, set the suspension flow rate to 15L / h, and spray to obtain Dv 10 =1.48μm, Dv 50 =4.07μm, Dv 90 Sintering raw materials with a diameter of 12.80 μm.

[0150] (3) Place the sintering raw material from (2) into a graphite sagger, introduce N2 gas into the sintering furnace until the oxygen content is <100ppm, and start the sintering program. First, raise the temperature to 350℃ at 2℃ / min, then hold at 350℃ for 3h, then raise the temperature to 560℃ at 4℃ / min, and then hold at 560℃ for 10h to obtain the high-pressure compaction cathode material: NFPP cathode material Na 4.15 Fe 2.95 (PO4)2P2O7.

[0151] S3. Preparation of the second precursor (Ni 0.25 Fe 0.40 Mn 0.25 Zn 0.1 (OH)2):

[0152] A clear solution with a total metal ion concentration of 110±5 g / L, denoted as solution D, was prepared by mixing nickel sulfate, zinc sulfate, ferric sulfate, manganese sulfate, and pure water. The molar ratio of metal ions was Ni:Fe:Mn:Zn = 25:40:25:10. 100 L of pure water and 100 mL of hydrazine hydrate were added to a reactor, and the temperature was raised to 65 °C. N2 gas was continuously introduced into the bottom of the reactor. Ammonia water was then added until the ammonia concentration in the reactor reached 10±2 g / L. Liquid alkali was added to maintain the pH at 11.8±0.2. The flow rates of solution D, ammonia water, and liquid alkali were all set and introduced into the reactor for co-precipitation. During this process, the ammonia concentration was maintained at 10±2 g / L, and the pH was maintained at 11.8±0.2. The reaction was stopped when the particle size of the precipitate in the reactor reached 2.5~3.0 μm. The resulting slurry was filtered, washed, and dried to obtain the second precursor, Ni. 0.25 Fe 0.40 Mn 0.25 Zn 0.1 (OH)2.

[0153] S4. Preparation of long-acting sodium supplements (Na 1.1 Ni0.25 Fe 0.40 Mn 0.25 Zn 0.1 O2):

[0154] The second precursor was mixed with Na2CO3 in a designed ratio and sintered in a box furnace. Air was introduced into the furnace, and the temperature was first increased to 850℃ at a rate of 3℃ / min, held at 850℃ for 2.5 hours, then increased to 980℃ at a rate of 2℃ / min, and held at 980℃ for 11 hours to obtain the long-acting sodium supplement Na2CO3. 1.15 Ni 0.22 Zn 0.12 Fe 0.44 Mn 0.22 O2.

[0155] S5. Preparation of polyanionic sodium-ion battery cathode material:

[0156] The high-density positive electrode material prepared by S2 and the long-lasting sodium supplement prepared by S4 were mixed evenly at a mass ratio of 97.2:2.8 to obtain a high-energy-density polyanion sodium-ion battery positive electrode material.

[0157] For details, please refer to the following: Figure 1 This is a SEM image of the high-voltage positive electrode material in Example 1 of this application; Figure 2 This is a SEM image of the long-acting sodium supplement material in Example 1 of this application; Figure 3 SEM image of 97.2% by mass of high-voltage positive electrode material mixed with 2.8% by mass of long-acting sodium supplement material in Example 1 of this application; Figure 4 The above are charge-discharge curves for Example 1 and Comparative Example 1 of this application.

[0158] Example 2

[0159] In this embodiment, a sodium-ion battery cathode material was prepared.

[0160] The experimental method is basically the same as in "Example 1", the difference being the elemental molar ratio of the high-pressure positive electrode material and the long-acting sodium supplementer, as detailed in "Table 1".

[0161] Example 3

[0162] In this embodiment, a sodium-ion battery cathode material was prepared.

[0163] The experimental method is basically the same as in "Example 1", the difference being the elemental molar ratio of the high-pressure positive electrode material and the long-acting sodium supplementer, as detailed in "Table 1".

[0164] Example 4

[0165] In this embodiment, a sodium-ion battery cathode material was prepared.

[0166] The experimental method is basically the same as in "Example 1", the difference being the mass ratio of the long-acting sodium supplement in the battery cathode material, as detailed in "Table 1".

[0167] Example 5

[0168] In this embodiment, a sodium-ion battery cathode material was prepared.

[0169] The experimental method is basically the same as in "Example 1", the difference being the mass ratio of the long-acting sodium supplement in the battery cathode material, as detailed in "Table 1".

[0170] Example 6

[0171] In this embodiment, a sodium-ion battery cathode material was prepared.

[0172] The experimental method is basically the same as in "Example 1", the difference being the sintering temperature and rate of the high-pressure positive electrode material and the long-acting sodium supplement, as detailed in "Table 1".

[0173] Example 7

[0174] In this embodiment, a sodium-ion battery cathode material was prepared.

[0175] The experimental method is basically the same as in "Example 1", the difference being the sintering temperature and rate of the high-pressure positive electrode material and the long-acting sodium supplement, as detailed in "Table 1".

[0176] Comparative Example 1

[0177] In this comparative example, a sodium-ion battery cathode material was prepared.

[0178] The experimental method is basically the same as in "Example 1", except that there is no preparation step for the long-acting sodium supplement, that is, no "S4, S5" steps in "Example 1".

[0179] Comparative Example 2

[0180] In this comparative example, a sodium-ion battery cathode material was prepared.

[0181] The experimental method is basically the same as in "Example 1", except that there is no acidic solution stirring step in the preparation process, that is, no acidic solution of oxalic acid and ethylene glycol is added in the step of "Example 1, S2, (1)".

[0182] Comparative Example 3

[0183] In this comparative example, a sodium-ion battery cathode material was prepared.

[0184] Experimental methods:

[0185] S1. Preparation of high-pressure positive electrode material (Na) 4.15 Fe 2.95 (PO4)2P2O7):

[0186] (1) FePO4, NaH2PO4, Na2CO3, glucose, oxalic acid and ethylene glycol are prepared according to the design values ​​and then mixed and stirred evenly in pure water to obtain a suspension; wherein the content of Na and Fe conforms to the molar ratio of Na:Fe=4.15:2.95; oxalic acid is added to make the pH of the suspension=2.5±0.5; the amount of ethylene glycol added is 0.5% of the total weight of the suspension.

[0187] (2) The suspension obtained in (1) was milled for 6 hours, and then sprayed using a two-flow spray dryer to obtain the sintering raw material; the spraying parameters were the same as in "Example 1".

[0188] (3) The sintering raw material in (2) is placed in a graphite sagger and sintered. The sintering steps are the same as those of the high-voltage positive electrode material sintering method in "Example 1".

[0189] S2, Preparation of the second precursor (Ni) 0.25 Fe 0.40 Mn 0.25 Zn 0.1 (OH)2), to prepare a long-acting sodium supplement (Na) 1.1 Ni 0.25 Fe 0.40 Mn 0.25 Zn 0.1 O2), to prepare polyanionic sodium-ion battery cathode material; consistent with "S3, S4, S5" in "Example 1".

[0190] Test Experiment

[0191] 1. Testing method:

[0192] (1) Preparation of coin cells using the cathode materials in the examples and comparative examples:

[0193] A. Preparation of the positive electrode:

[0194] Mixing: Mix the positive electrode material (sodium-ion battery positive electrode material), conductive agent and binder in a ratio (e.g., 8:1:1).

[0195] Pulping: Add solvent (NMP) and stir thoroughly to form a uniform black slurry.

[0196] Coating: Apply the slurry evenly onto the aluminum foil.

[0197] Drying: Dry the electrode sheets to remove solvent.

[0198] Stamping: The dried electrode sheets are stamped into standard round pieces and then vacuum dried again to remove water.

[0199] B. Battery assembly (completed inside the glove box):

[0200] Preparation: Prepare the battery casing, sodium metal sheet (negative electrode), separator, and electrolyte.

[0201] Stacking: Place the gasket, positive electrode plate (coating side up), separator, and sodium plate into the positive electrode shell in sequence.

[0202] Electrolyte application: After each stacking step, add an appropriate amount of electrolyte to wet the substrate.

[0203] Finishing touches: Place the gasket and spring, then cover with the negative electrode shell.

[0204] C. Packaging and resting:

[0205] Encapsulation: The battery is sealed using a crimping machine.

[0206] Let stand: Allow the battery to stand at room temperature for at least 12 hours.

[0207] After allowing it to settle, place it in the Blue Electric Test Cabinet to begin testing.

[0208] (2) Capacity retention test: At 25℃, the charge-discharge cycle characteristics of the button cell were tested using a Blue Electric test cabinet, with 1C = 110mAh / g set. Charge and discharge were performed at a charge-discharge rate of 0.2C within a voltage range of 1.5V to 3.8V. Specifically, the cell was charged at a constant current of 0.2C to 3.8V, then charged at a constant voltage of 3.8V until the cutoff current < 0.02C, rested for 5 minutes, then discharged at a constant current of 0.2C to 1.5V, and then discharged at a constant voltage of 1.5V until the cutoff current < 0.02C. After that, the cell was charged and discharged at a charge-discharge rate of 1C within a voltage range of 1.5V to 3.8V, with the same process as the 0.2C charge-discharge procedure. This process was repeated 100 times, and the charge-discharge capacity of the 1C cell in the 1st and 100th cycles was recorded.

[0209] Cycle capacity retention (%) = (Discharge capacity at 100th cycle / Discharge capacity at 1st cycle) × 100%.

[0210] 2. Test Results:

[0211] The theoretical capacity of NFPP is 129 mAh / g, and the theoretical capacity of sodium supplement is 244 mAh / g. In Example 1, the charging capacity of high-pressure compacted NFPP was 119 mAh / g, and the charging capacity of sodium supplement was 231 mAh / g. The performance of the cathode material of the final battery is shown in the table below.

[0212] Table 2. Material Properties of Examples and Comparative Examples

[0213]

[0214] As shown in Table 2, Example 1 exhibits the best overall performance. Example 2, by using the lower limit of element content, results in a decrease in the content of elements such as Na, Ni, and Zn, leading to a decline in capacity. Example 3, by using the upper limit of element content, results in an increase in the content of elements such as Na, Ni, and Zn, leading to an increase in capacity, but also significant cycle decay. Example 4, with a reduction in sodium supplementation, results in a decrease in both capacity and compaction. Example 5, with an increase in sodium supplementation, results in an increase in both capacity and compaction, but also significant cycle decay. Example 6, with its low sintering temperature and rate, exhibits overall performance close to that of Example 1. Example 7, with its high sintering temperature and rate, increases compaction, but the high temperature tends to cause particle growth, resulting in a slight decrease in capacity.

[0215] Comparative Example 1, without sodium supplementation, had a slightly lower capacity. Furthermore, since the compaction of the sodium supplementation was 3.0-3.1 g / cm3, its removal reduced the overall compaction of the cathode material. Comparative Example 2 eliminated acid dissolution stirring during the preparation process, which prevented the effective dispersion of the nano-sized "precursor 1," causing the material to agglomerate and grow. Although the compaction increased, the capacity decreased significantly. Comparative Example 3 did not use "precursor 1" and relied on commercially available Fe, Na, and P sources to synthesize the NFPP cathode, resulting in the lowest compaction of the final product.

[0216] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polyanionic sodium-ion battery cathode material, characterized in that, Including high-pressure positive electrode materials and long-acting sodium replenishing agents; The high-pressure positive electrode material is Na. a Fe b (PO4)2P2O7; where 3.8≤a≤4.4, 2.4≤b≤3.2; The long-acting sodium supplement is Na v Ni x Fe y Mn z Zn w O2; where 1.05≤v≤1.25, 0.20≤x≤0.30, 0.30≤y≤0.50, 0.10≤z≤0.30, 0.05≤w≤0.15; and x+y+z+w=1; The long-acting sodium replenishing agent accounts for 2% to 5% of the mass of the polyanionic sodium-ion battery cathode material; the particle size Dv of the long-acting sodium replenishing agent... 50 The particle size Dv of the high-pressure positive electrode material is 2μm~4μm. 50 The size ranges from 2μm to 5μm.

2. A method for preparing the polyanionic sodium-ion battery cathode material as described in claim 1, characterized in that, include: A high-pressure positive electrode material and a long-lasting sodium replenishing agent are prepared separately; and the high-pressure positive electrode material and the long-lasting sodium replenishing agent are mixed to obtain the polyanionic sodium-ion battery positive electrode material.

3. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 2, characterized in that, The high-pressure positive electrode material is prepared by stirring a first precursor, a first sodium source, a carbon source, and an acidic solution, followed by granulation and sintering in an inert atmosphere; wherein the first precursor is nano-sized Na. a1 Fe b1 P c1 O d1 ·eH2O, 0<a1≤2.5, 2.4≤b1≤3.2, 3.2≤c1≤4.3, 3.5c1≤d1≤4c1, 0<e≤4.

4. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 2, characterized in that, The long-acting sodium supplement is prepared by mixing a second precursor with a first sodium source and sintering the mixture in an air atmosphere; the second precursor is Ni. x Fe y Mn z Zn w (OH)2.

5. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The first sodium source used in the preparation of the high-pressure positive electrode material and the long-acting sodium supplement includes at least one of Na2CO3, CH3COONa and Na2C2O4.

6. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The carbon source includes at least one of glucose, PEG, sucrose, and citric acid.

7. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The acidic solution is a mixed solution of an acidic reagent and a dispersant; wherein the acidic reagent includes at least one of phosphoric acid, oxalic acid and nitric acid; and / or the dispersant includes at least one of PVP, ethylene glycol and sodium hexametaphosphate.

8. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The stirring process in the preparation of the high-pressure positive electrode material further includes: adding the acidic solution during stirring to adjust the pH to 2.5±0.5, and ensuring that the particle size of the mixture is not greater than 200nm.

9. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The granulation is spray granulation; the parameters of the spray granulation include: air flow rate of 50 to 200 times the liquid flow rate; and / or, inlet air temperature of 260℃ to 280℃; and / or, outlet air temperature of 90℃ to 110℃; and / or, outlet particle size of Dv. 10 =1.0μm~3.0μm, Dv 50 =3.0μm~8.0μm, Dv 90 =8μm~28μm.

10. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The inert atmosphere sintering includes: A. First stage: heating to 300℃~400℃ at a heating rate of 1℃ / min~3℃ / min; B. Second stage: holding at 300℃~400℃ for 2 hours~4 hours; C. Third stage: heating to 500℃~600℃ at a heating rate of 3℃ / min~5℃ / min; D. Fourth stage: holding at 500℃~600℃ for 6 hours~12 hours.

11. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The method for preparing the first precursor includes: The second sodium source, iron source, and phosphorus source were mixed under an inert atmosphere, and an oxidant solution was added to carry out a precipitation reaction to obtain the first precursor.

12. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 11, characterized in that, The second sodium source used in the preparation of the first precursor includes at least one of Na2CO3, NaH2PO4, Na3PO4, and Na4P2O7.

13. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The particle size distribution of the first precursor is 40 nm ≤ Dv 50 ≤200nm.

14. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 11, characterized in that, The phosphorus source includes at least one of NH4H2PO4 and H3PO4.

15. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 11, characterized in that, The iron source includes at least one of FeC2O4, FeSO4, and Fe(NO3)3.

16. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 11, characterized in that, The oxidant includes at least one of hydrogen peroxide, nitric acid, and sodium peroxide.

17. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The sintering conditions for the long-acting sodium supplement include: a sintering temperature of 860℃ to 980℃; and / or a sintering time of 8 hours to 12 hours.

18. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 3, characterized in that, The preparation of the long-acting sodium supplement further includes: after sintering, the sintered material is subjected to air milling at 0.55 MPa to 0.75 MPa.

19. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 4, characterized in that, The preparation of the second precursor includes: preparing a mixed solution of nickel source, zinc source, iron source and manganese source, and performing complexation co-precipitation of the mixed solution with ammonia water and alkaline solution under an inert atmosphere to obtain the second precursor.

20. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 19, characterized in that, The concentration of metal ions in the mixed solution is 90 g / L to 120 g / L.

21. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 19, characterized in that, The nickel source includes nickel sulfate.

22. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 19, characterized in that, The zinc source includes zinc sulfate.

23. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 19, characterized in that, The iron source includes ferrous sulfate.

24. The method for preparing the polyanionic sodium-ion battery cathode material as described in claim 19, characterized in that, The manganese source includes manganese sulfate.

25. A battery, characterized in that, Includes the polyanionic sodium-ion battery cathode material as described in claim 1; or, the polyanionic sodium-ion battery cathode material prepared by the preparation method according to any one of claims 2-24.

26. An electrical-related device, characterized in that, Includes the battery as described in claim 25.

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