Positive electrode material precursor, positive electrode material, preparation method thereof, and sodium ion battery

Abstract

The present disclosure discloses a positive electrode material precursor, a positive electrode material, a method for preparing the same, and a sodium-ion battery. The positive electrode material precursor includes a core and a shell surrounding the core, the core being made of Ni x Fe y Mn 1-x-y (OH)2, where 0.2≦x≦0.7 and 0.2≦y≦0.5, and the shell is M a Mn 1-a (OH)2, where M is nickel or iron, 0.05≦a≦0.7, and the core and shell are both deposited with flaky primary particles. The cathode material precursor of the present application can obtain a heterostructure cathode material having an O3 phase core and a P2 phase shell by controlling the components of the core and shell and combining them with a sparse structure deposited with flaky primary particles, and the synergistic effect of the two-phase structure can achieve both high capacity and high cycle stability, further improving the electrochemical performance of sodium ion batteries. In addition, the preparation method of the cathode material of the present application is simple, low cost, and suitable for industrial large-scale production.

Description

[Technical Field]

[0001] The present application relates to the technical field of battery production and manufacturing, such as a cathode material precursor, a cathode material, a preparation method thereof, and a sodium ion battery. [Background technology]

[0002] Sodium, which has similar chemical properties to lithium, is not only abundant in resource reserves but also widely distributed, so sodium-ion batteries are considered the most promising secondary batteries to be widely applied in the field of large-scale energy storage, replacing lithium-ion batteries. In addition, compared with lithium-ion batteries, sodium-ion batteries have greater cost advantages, do not contain toxic heavy metals, have simpler battery structures, and are easier to recycle and reuse, so they have more potential for sustainable development.

[0003] However, because sodium ions have a larger radius than lithium ions, cathode materials undergo complex multiple phase transitions during charging and discharging, resulting in a more unstable structure and lower specific capacity than lithium-ion batteries. Currently, layered cathode materials are typically used in sodium-ion batteries. Depending on the sodium ion coordination environment, layered cathode materials are primarily divided into P2 and O3 phases. The P2 phase is a sodium-deficient compound with open prismatic channels, providing rapid ionic conductivity and high structural stability, but its capacity is low. On the other hand, the O3 phase has the advantage of high specific capacity, but its poor structural stability results in poor cycling stability. Neither phase achieves high structural stability nor high specific capacity at the same time. Therefore, how to simultaneously improve the cycling stability and specific capacity of sodium-ion batteries is a key issue facing the large-scale application of sodium-ion batteries.

[0004] CN108987708A discloses a positive electrode material for a sodium ion battery, a preparation method thereof and a sodium ion battery, and 0.67 Ni0.167 Co 0.167 Mn 0.67 The ZrO2 substrate is coated with one layer, and the mass of the coating layer is 1-5% of the mass of the substrate material. Nickel salt, cobalt salt, and manganese salt are co-precipitated with Na2CO3 and ammonia water complexing agent to obtain spherical particle precursors, which are then calcined to form the substrate material Na 0.67 Ni 0.167 Co 0.167 Mn 0.67 O2 is obtained, and the substrate is mixed with Zr(C3H7O)4 to evaporate the solvent, thereby obtaining a sodium ion cathode material coated with ZrO2. However, this method requires the solvent to be evaporated to dryness during coating, which makes the treatment process complicated and unfriendly to the environment.

[0005] CN113921809A discloses a positive electrode material for a P2-type layered sodium ion battery and a method for preparing the same, in which Na ions are located in the middle of the transition metal layer and form an alkali metal layer, and Na + The cathode material is co-doped with transition metal sites to improve the electrochemical performance of the material. The chemical formula of the cathode material is Na 0.67-x M x Mn 1-y N y O2, where M = Zn, Al, Mg, K, Ca, Li, and N = Fe, Cr, V, Ni, Ti, Cu, Nb, Co. This method uses the sol-gel method to quantitatively dope trace elements and achieve intermolecular doping, but the P2 still has a single-phase structure, the specific capacity is not high, and the sol-gel method is only applicable to laboratory preparation and not to large-scale production.

[0006] CN113292113A discloses an O3-phase layered oxide cathode material for sodium-ion batteries and a method for preparing the same, which includes dissolving and mixing a transition metal salt and a soluble sodium salt in deionized water to obtain a mixed salt solution, spray-pyrolyzing the mixed salt solution to obtain a sodium-containing oxide precursor, and pressing the sodium-containing oxide precursor into a sheet and then high-temperature solid-state sintering to obtain an O3-phase layered oxide cathode material. The layered cathode material obtained by this method still has a single-phase structure, which makes it prone to interlayer slippage of the cathode material during battery charge and discharge, and does not solve the problem of poor structural stability.

[0007] Therefore, how to simultaneously improve the cycle stability and specific capacity of the positive electrode material for sodium ion batteries while simplifying the preparation process and facilitating industrialized large-scale production is very important for the realization of large-scale application of sodium ion batteries. Summary of the Invention [Problem to be solved by the invention]

[0008] The following is a general summary of the subject matter described in detail herein. This summary does not limit the scope of the claims.

[0009] The present application provides a cathode material precursor, a cathode material, a preparation method thereof, and a sodium ion battery. The cathode material precursor controls the core and shell components and combines them with a loose structure formed by the deposition of flaky primary particles to obtain a heterostructure cathode material having an O3 phase core and a P2 phase shell, which simultaneously improves the cycle stability and specific capacity of the cathode material for sodium ion batteries. [Means for solving the problem]

[0010] In Aspect 1, the present application provides a cathode material precursor, comprising: The positive electrode material precursor includes a core and a shell surrounding the core, and the core is made of Ni x Fe y Mn1-x-y (OH)2, wherein 0.2≦x≦0.7 and 0.2≦y≦0.5, and the shell is M a Mn 1-a (OH)2, where M is nickel or iron, 0.05≦a≦0.7, and the core and the shell are both deposited with flaky primary particles; A positive electrode material precursor is provided.

[0011] In this application, the core and shell of the cathode material precursor have different compositions, and both the core and shell have a loose structure formed by flaky primary particles. This loose structure subsequently contributes to the diffusion of sodium ions into the cathode material. Controlling the core and shell compositions of the cathode material precursor and combining them with the loose structure formed by flaky primary particles contributes to the subsequent production of a heterogeneous cathode material having an O3 core and a P2 shell. In this case, the O3 core provides high capacity, and the P2 shell forms a stable interfacial layer. The synergistic effect of the two-phase structure achieves both high specific capacity and high cycling stability, significantly improving the electrochemical performance of the cathode material. Note that the loose structure formed by flaky primary particles in this application refers to the morphology of the core and shell subunits being flaky, which differs from a layered structure defined by a crystalline phase, and the core and shell also having a loose structure, which also differs from a layered structure.

[0012] In the present application, the positive electrode material precursor is Ni x Fe y Mn 1-x-y (OH)2@M a Mn 1-a (OH)2, which means that a Mn 1-a (OH)2 is Ni x Fe y Mn 1-x-y The outer surface of (OH)2 is coated with

[0013] The cathode material precursor of the present application controls the core and shell components and combines them with the loose structure deposited by the flaky primary particles to subsequently form a heterostructure cathode material having an O3 phase core and a P2 phase shell, thereby achieving the effect of simultaneously improving the cycle stability and specific capacity of the cathode material for sodium-ion batteries.

[0014] In one preferred technical solution of the present application, the shape of the core in the positive electrode material precursor includes a spherical or near-spherical shape.

[0015] Preferably, the particle size of the core in the positive electrode material precursor is 2 to 4.5 μm, and may be, for example, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, or 4.5 μm, but is not limited to the listed values, and other values within the range that are not listed also apply.

[0016] Preferably, the morphology of the positive electrode material precursor includes a spherical or near-spherical shape. Preferably, the particle size of the positive electrode material precursor is 2.5 to 4.5 μm, and may be, for example, 2.5 μm, 3 μm, 3.5 μm, 4 μm, or 4.5 μm, but is not limited to the listed values, and other values within the range that are not listed also apply.

[0017] In the present application, the core particle size of the positive electrode material precursor and the particle size of the positive electrode material precursor both refer to the average particle size.

[0018] In aspect 2, the present embodiment comprises: simultaneously injecting a first metal salt mixed solution, a complexing agent solution, and a precipitant solution into a reactor, and performing a primary co-precipitation reaction during the injection process to obtain a core of a positive electrode material precursor; and then simultaneously injecting a second metal salt mixed solution, the complexing agent solution, and the precipitant solution into the reactor, and performing a secondary co-precipitation reaction during the injection process to obtain the positive electrode material precursor; A method for preparing the cathode material precursor of embodiment 1 is provided.

[0019] In the present application, when the primary coprecipitation reaction is carried out, the first metal salt solution, complexing agent solution, and precipitant solution are simultaneously injected into a reactor at constant flow rates, and the primary coprecipitation reaction is carried out while the injections are being carried out. The primary coprecipitation reaction is not terminated when the injection of each component is stopped, and the coprecipitation reaction is not started until all the necessary first metal salt solution, complexing agent solution, and precipitant solution have been added to the reactor. Similarly, the operating process of the secondary coprecipitation reaction in the present application is the same as that of the primary coprecipitation reaction. In other words, both the primary and secondary coprecipitation reactions in the present application are continuous injection and continuous reaction processes.

[0020] The present application employs a stepwise co-precipitation process of continuous injection and continuous reaction, which allows for more effective control of the core and shell components of the positive electrode material precursor, as well as more effective adjustment and control of the precipitant concentration and complexing agent concentration in the mixed solution in the reactor during the co-precipitation process, thereby adjusting and controlling the balance between the nucleation rate and growth rate of crystals, and further forming a loose structure in which both the core and shell are deposited with flake-like primary particles.

[0021] In one preferred technical solution of the present application, the first metal salt mixed solution is prepared by mixing a nickel salt, an iron salt, a manganese salt and a solvent.

[0022] Preferably, the total concentration of metal ions in the first metal salt mixed solution is 1 to 4 mol / L, and may be, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or 4 mol / L, but is not limited to the recited values, and other values not recited within the numerical range also apply.

[0023] Preferably, the molar ratio of the nickel salt, the iron salt, and the manganese salt is x:y:(1-xy), where 0.2≦x≦0.7 and 0.2≦y≦0.5. For example, x may be 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7, and y may be 0.2, 0.3, 0.4, or 0.5.

[0024] Preferably, the nickel salt comprises any one of nickel sulfate, nickel chloride, or nickel nitrate.

[0025] Preferably, the iron salt comprises ferrous sulfate or ferrous chloride. Preferably, the manganese salt comprises any one of manganese sulfate, manganese chloride or manganese nitrate.

[0026] Preferably, the solvent comprises deionized water. Preferably, the concentration of the complexing agent is 1 to 3 mol / L, and may be, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, but is not limited to the recited values, and other values within the range that are not recited also apply.

[0027] Preferably, the complexing agent comprises an aqueous ammonia complexing agent. In the present application, an ammonia water complexing agent solution is prepared by mixing ammonia water and deionized water.

[0028] Preferably, the concentration of the precipitant is 1 to 3 mol / L, and may be, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, but is not limited to the recited values, and other values within the range that are not recited also apply.

[0029] Preferably, the precipitating agent comprises an alkaline solution. Preferably, the alkaline solution comprises a sodium hydroxide solution or a potassium hydroxide solution.

[0030] In this application, the precipitant solution is prepared by dissolving the precipitant particles in deionized water. In one preferred technical solution of the present application, in the primary coprecipitation reaction, the first metal salt mixed solution is injected into the reactor at a flow rate of 8 to 12 kg / h, which may be, for example, 8 kg / h, 8.5 kg / h, 9 kg / h, 9.5 kg / h, 10 kg / h, 10.5 kg / h, 11 kg / h, 11.5 kg / h, or 12 kg / h, but is not limited to the listed values, and other unlisted values within the numerical range also apply.

[0031] Preferably, in the primary coprecipitation reaction, the complexing agent solution is injected into the reactor at a flow rate of 1 to 3 kg / h, which may be, for example, 1 kg / h, 1.5 kg / h, 2 kg / h, 2.5 kg / h, or 3 kg / h, but is not limited to the recited values, and other unrecited values within the range also apply.

[0032] Preferably, in the primary coprecipitation reaction, the precipitant solution is injected into the reactor at a flow rate of 2.4 to 3 kg / h, which may be, for example, 2.4 kg / h, 2.5 kg / h, 2.6 kg / h, 2.7 kg / h, 2.8 kg / h, 2.9 kg / h, or 3 kg / h, but is not limited to the recited values, and other unrecited values within the range also apply.

[0033] In the present application, the flow rates of the first metal salt mixed solution in the primary coprecipitation reaction are limited to 8 to 12 kg / h, the complexing agent solution to 1 to 3 kg / h, and the precipitating agent solution to 2.4 to 3 kg / h. This is because the coordination of the flow rates of the first metal salt solution, complexing agent solution, and precipitating agent solution can maintain a stable pH (i.e., a stable precipitating agent concentration in the solution in the reactor) and a stable complexing agent concentration in the solution in the reactor during the primary coprecipitation reaction, thereby maintaining system stability throughout the primary coprecipitation reaction and contributing to the formation of a sparse core structure deposited by flaky primary particles. Coprecipitation is performed only after all the necessary first metal salt mixed solution, complexing agent solution, and precipitating agent solution are added to the reactor, thereby avoiding the problem of the pH and complexing agent concentration in the coprecipitation reaction gradually decreasing due to the continuous consumption of precipitating agent and complexing agent, which results in poor system stability and makes it difficult to accurately control the core composition and morphology.

[0034] Preferably, the primary coprecipitation reaction is carried out at 40 to 60°C, for example, 40°C, 45°C, 50°C, 55°C, or 60°C, but is not limited to the listed values, and other values not listed within the range also apply.

[0035] Preferably, during the primary coprecipitation reaction, the pH of the solution in the reactor is 9.5 to 11, for example, 9.5, 10, 10.5, or 11, but is not limited to the listed values, and other values not listed within the range also apply.

[0036] Preferably, during the primary coprecipitation reaction, the concentration of the complexing agent in the solution in the reactor is 7 to 11 g / L, and may be, for example, 7 g / L, 7.5 g / L, 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L, 10 g / L, 10.5 g / L, or 11 g / L, but is not limited to the listed values, and other values not listed within the range also apply.

[0037] In the present invention, by coordinating the flow rates of the first metal salt solution, the complexing agent solution, and the precipitant solution, the pH of the primary coprecipitation reaction can be controlled to 9.5-11 and the complexing agent concentration to 7-11 g / L, where the pH is mainly used to adjust and control the crystal nucleation rate in the primary coprecipitation reaction, and the complexing agent concentration is mainly used to adjust and control the crystal growth rate in the primary coprecipitation reaction. Thus, by controlling the pH and the complexing agent concentration within an appropriate range, the crystal nucleation and crystal growth rates can be dynamically balanced, which contributes to obtaining a sparse core structure deposited with flaky primary particles and effectively controls the uniformity of the core particle size.

[0038] Preferably, the primary coprecipitation reaction is carried out under stirring. Preferably, the stirring rotation speed of the primary coprecipitation reaction is 300 to 380 r / min, and may be, for example, 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min, 350 r / min, 360 r / min, 370 r / min, or 380 r / min, but is not limited to the listed values, and other unlisted values within the range also apply.

[0039] In this application, the stirring rotation speed of the primary coprecipitation reaction is limited to 300 to 380 r / min. If the rotation speed is lower than 300 r / min, the secondary particles will aggregate severely and the sphericity will be poor. If the rotation speed is higher than 380 r / min, the particle size will not grow easily during the coprecipitation process and fine powder will be easily generated, which will affect the electrochemical performance of the positive electrode material.

[0040] In the present invention, by adjusting and controlling the pH of the solution in the reactor and the concentration of the complexing agent during the primary coprecipitation reaction and combining this with an appropriate stirring speed, it is possible to obtain better spherical / spherical cores deposited with flaky primary particles.

[0041] Preferably, the time for the primary coprecipitation reaction is 60 to 90 hours, for example, 60 hours, 65 hours, 70 hours, 75 hours, 80 hours, 85 hours, or 90 hours, but is not limited to the listed values, and other values not listed within the range also apply.

[0042] Preferably, before the primary coprecipitation reaction, deionized water, the complexing agent solution, and the precipitating agent solution are first added to the reaction apparatus to form a base solution for the primary coprecipitation reaction.

[0043] In this application, a certain amount of deionized water, a complexing agent solution, and a precipitating agent solution are added to the reactor to form a base solution, which ensures that crystal nucleation and growth occur in the solution system and maintains the stability of the subsequent coprecipitation reaction system. The pH of the base solution is 10.5 to 11, and the concentration of the complexing agent is 7 to 10. When a 200 L reactor is used as the reactor, the total amount of the base solution may be 100 L.

[0044] In one preferred technical solution of the present application, the second metal salt mixed solution is prepared by mixing a nickel salt, a manganese salt and a solvent, or the second metal salt mixed solution is prepared by mixing an iron salt, a manganese salt and a solvent.

[0045] Preferably, the total concentration of metal ions in the second metal salt mixed solution is 1 to 4 mol / L, and may be, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or 4 mol / L, but is not limited to the listed values, and other values not listed within the range also apply.

[0046] Preferably, the molar ratio of the nickel salt to the manganese salt is a:(1-a), or the molar ratio of the iron salt to the manganese salt is a:(1-a), provided that 0.05≦a≦0.7, for example, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7, is not limited to the recited values, and other unrecited values within the numerical ranges also apply.

[0047] Preferably, the nickel salt comprises any one of nickel sulfate, nickel chloride, or nickel nitrate.

[0048] Preferably, the iron salt comprises ferrous sulfate or ferrous chloride. Preferably, the manganese salt comprises any one of manganese sulfate, manganese chloride or manganese nitrate.

[0049] Preferably, the solvent comprises deionized water. Preferably, in the secondary coprecipitation reaction, the second metal salt mixed solution is injected into the reactor at a flow rate of 8 to 12 kg / h, which may be, for example, 8 kg / h, 8.5 kg / h, 9 kg / h, 9.5 kg / h, 10 kg / h, 10.5 kg / h, 11 kg / h, 11.5 kg / h, or 12 kg / h, but is not limited to the listed values, and other unlisted values within the range also apply.

[0050] Preferably, in the secondary coprecipitation reaction, the complexing agent solution is injected into the reactor at a flow rate of 1 to 3 kg / h, which may be, for example, 1 kg / h, 1.5 kg / h, 2 kg / h, 2.5 kg / h, or 3 kg / h, but is not limited to the recited values, and other unrecited values within the range also apply.

[0051] Preferably, in the secondary coprecipitation reaction, the precipitant solution is injected into the reactor at a flow rate of 2.4 to 3 kg / h, which may be, for example, 2.4 kg / h, 2.5 kg / h, 2.6 kg / h, 2.7 kg / h, 2.8 kg / h, 2.9 kg / h, or 3 kg / h, but is not limited to the recited values, and other unrecited values within the numerical range also apply.

[0052] Similarly, the present invention can maintain stable pH and complexing agent concentration during the secondary coprecipitation reaction by coordinating the flow rates of the second metal salt solution, complexing agent solution, and precipitant solution, thereby maintaining system stability throughout the entire secondary coprecipitation reaction and contributing to the formation of a sparse shell structure deposited on the outer surface of the core with flaky primary particles. By adding all the necessary second metal salt mixed solution, complexing agent solution, and precipitant solution to the reactor before coprecipitation, it is possible to avoid the problem of the pH and complexing agent concentration gradually decreasing during the coprecipitation reaction due to the continuous consumption of precipitant and complexing agent, resulting in poor system stability and making it difficult to accurately control the core composition and morphology. Furthermore, the complexing agent solution and precipitant solution used in the secondary coprecipitation reaction are the same as those used in the primary coprecipitation reaction, respectively.

[0053] Preferably, the secondary coprecipitation reaction is carried out at 40 to 60°C, for example, 40°C, 45°C, 50°C, 55°C, or 60°C, but is not limited to the listed values, and other values not listed within the range also apply.

[0054] Preferably, during the secondary coprecipitation reaction, the pH of the solution in the reactor is 8.5 to 11, for example, 8.5, 9, 9.5, 10, 10.5, or 11, but is not limited to the listed values, and other values not listed within the range also apply.

[0055] Preferably, during the secondary coprecipitation reaction, the concentration of the complexing agent in the solution in the reactor is 8 to 12 g / L, and may be, for example, 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L, 10 g / L, 10.5 g / L, or 11 g / L, but is not limited to the listed values, and other values not listed within the range also apply.

[0056] Similarly, in this application, pH is primarily used to adjust and control the crystal nucleation rate in the secondary coprecipitation reaction, and the complexing agent concentration is primarily used to adjust and control the crystal growth rate in the secondary coprecipitation reaction. Therefore, by controlling the pH and complexing agent concentration within appropriate ranges, the crystal nucleation and crystal growth rates can be adjusted and controlled, contributing to the formation of a sparse shell structure consisting of flaky primary particles deposited on the core surface. During the secondary coprecipitation process, the crystal particles on the core surface can be used as seed crystals to grow and form a shell, and crystal growth is more difficult during the secondary coprecipitation process. Therefore, the pH of the secondary coprecipitation is slightly lower than that of the primary coprecipitation, but the complexing agent concentration is slightly higher than that of the primary coprecipitation.

[0057] Preferably, the secondary coprecipitation reaction is carried out under stirring. Preferably, the stirring rotation speed of the secondary coprecipitation reaction is 250 to 350 r / min, and may be, for example, 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min, 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min, or 350 r / min, but is not limited to the listed values, and other unlisted values within the numerical range also apply.

[0058] In the present application, the stirring rotation speed of the secondary coprecipitation reaction is limited to 250 to 350 r / min. If the rotation speed is lower than 250 r / min, the secondary particles will aggregate severely, resulting in poor sphericity and uneven coating. If the rotation speed is higher than 350 r / min, the particle growth rate will be limited and fine powder will be easily generated, which will affect the electrochemical performance of the positive electrode material.

[0059] In the present application, by adjusting and controlling the pH of the solution in the reactor and the concentration of the complexing agent during the secondary coprecipitation reaction, and by combining with an appropriate stirring speed, it is possible to obtain a shell deposited with flaky primary particles and obtain a spherical / near-spherical cathode material precursor.

[0060] Preferably, the time for the secondary coprecipitation reaction is 2 to 8 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours, but is not limited to the listed values, and other values not listed within the range also apply.

[0061] In aspect 3, the present embodiment comprises: prepared with the cathode material precursor of embodiment 1; A positive electrode material is provided.

[0062] The positive electrode material includes an O3 phase core and a P2 phase shell surrounding the O3 phase core, and the O3 phase core is composed of Na(Ni x Fe y Mn 1-x-y )O2, where 0.2≦x≦0.7 and 0.2≦y≦0.5, and the P2 phase shell is Na b (M a Mn 1-a )O2, where M is nickel or iron, 0.05≦a≦0.7, and 0.67≦b≦0.78, and the O3 phase core and the P2 phase shell are both formed by deposition of flake-shaped primary particles.

[0063] The present cathode material has a P2 shell structure surrounding an O3 core, and the advantages of the high capacity of the O3 phase and the high stability of the P2 phase solve the problem of the incompatibility of capacity and stability faced by sodium ion cathode materials at the crystalline structure level. Furthermore, the particle size of the present cathode material is not significantly different from that of the cathode material precursor.

[0064] In the present application, the positive electrode material is Na(Ni x Fe y Mn 1-x-y )O2@Na b (MaMn 1-a )O2, which means that Na b (MaMn 1-a )O2 and Na(Ni x Fe y Mn 1-x-y )O2 outer surface.

[0065] In aspect 4, the present embodiment comprises: mixing a positive electrode material precursor, a dispersant, and a sodium source, and then calcining the mixture to obtain the positive electrode material; A method for preparing the cathode material of embodiment 3 is provided.

[0066] In this application, a dispersant is added during the mixing process of the positive electrode material precursor and the sodium source, which promotes the diffusion of sodium ions into the interior of the positive electrode material precursor particles at high temperatures, further promoting the formation of a positive electrode material structure with an O3 core and a P2 shell. The preparation method is simple, low cost, and suitable for large-scale industrial production.

[0067] In one preferred technical solution of the present application, the dispersant comprises polyvinylpyrrolidone. Preferably, the sodium source comprises sodium carbonate.

[0068] Preferably, the positive electrode material precursor, the dispersant, and the sodium source are mixed by grinding in a mortar.

[0069] Preferably, the firing temperature is 800 to 1000°C, and may be, for example, 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 950°C, 980°C, or 1000°C, but is not limited to the listed values, and other values not listed within the range also apply.

[0070] Preferably, the baking time is 12 to 20 hours, and may be, for example, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, or 20 hours, but is not limited to the listed values, and other values not listed within the range also apply.

[0071] In aspect 5, the present embodiment comprises: comprising the cathode material of embodiment 3; A sodium-ion battery is provided.

[0072] The sodium ion battery prepared with the cathode material of the present application has significantly improved specific capacity and cycle stability, which further improves the electrochemical performance of the sodium ion battery and promotes the industrial development of the sodium ion battery. [Effects of the Invention]

[0073] Compared with the related art, the beneficial effects of the embodiments of the present application are as follows: The cathode material precursor of the present application, by controlling the core and shell components and combining the sparse structure of the flaky primary particles deposited therein with the characteristic of contributing to the inward diffusion of sodium ions during the sintering process, can produce a heterostructure cathode material with an O3 core and a P2 shell. The O3 core provides high capacity, while the P2 shell forms a stable interfacial layer. The synergistic effect of the two-phase structure achieves both high capacity and high cycle stability, further improving the electrochemical performance of sodium-ion batteries. Furthermore, the preparation method of the present cathode material is simple, low-cost, and suitable for large-scale industrial production.

[0074] Other aspects may be understood upon reading and understanding the drawings and detailed description. The drawings are intended to provide a further understanding of the technical solutions of the embodiments of the present invention, constitute a part of the specification, and are intended to interpret the technical solutions of the present invention together with the embodiments of the present application, but are not intended to limit the technical solutions of the present invention. [Brief explanation of the drawings]

[0075] [Figure 1] FIG. 2 is an SEM image of a positive electrode material precursor according to Example 1 of the present application. [Figure 2] FIG. 2 is an SEM image of a cross section of a positive electrode material precursor according to Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0076] The technical solution of the present application will be further described below through specific embodiments, which are merely for the understanding of those skilled in the art and are not intended to specifically limit the present application. [Example]

[0077] This embodiment provides a method for preparing a positive electrode material, which includes the following steps: (1) Nickel sulfate, ferrous sulfate, and manganese sulfate were dissolved in deionized water in a molar ratio of 0.25:0.5:0.25 to prepare a first metal salt mixed solution with a total metal ion concentration of 1 mol / L, and ferrous sulfate and manganese sulfate were dissolved in deionized water in a molar ratio of 0.5:0.5 to prepare a second metal salt mixed solution with a total metal ion concentration of 2 mol / L. At the same time, an ammonia water complexing agent solution with a concentration of 1 mol / L and a sodium hydroxide solution with a concentration of 2 mol / L were prepared.

[0078] (2) Add deionized water, the ammonia water complexing agent solution obtained in step (1) and sodium hydroxide solution to a 200L reactor to form a base solution to maintain the stability of the system, where the total volume of the base solution is 100L, and control the ammonia water complexing agent concentration in the base solution within the range of 9-10g / L, and control the pH within the range of 10.6-11. Then, simultaneously inject the first metal salt mixed solution, the ammonia water complexing agent solution and the sodium hydroxide solution into the reactor at flow rates of 8kg / h, 2kg / h and 2.5kg / h, respectively, and carry out a primary coprecipitation reaction at a temperature of 45°C and a stirring speed of 340r / min for 80 hours to obtain a core Ni of a cathode material precursor with an average particle size of 3.8μm. 0.25 Fe 0.5 Mn 0.25 (OH)2 was obtained, and during the primary coprecipitation reaction, the pH of the solution in the reaction vessel was maintained within the range of 9.5 to 10, and the concentration of the complexing agent in the solution in the reaction vessel was maintained within the range of 8 to 10 g / L.

[0079] (3) The second metal salt mixed solution, the ammonia water complexing agent solution, and the sodium hydroxide solution were simultaneously injected into the reactor at flow rates of 8 kg / h, 2.3 kg / h, and 2.4 kg / h, respectively, and the secondary coprecipitation reaction was carried out at a temperature of 45°C and a stirring speed of 280 r / min for 4 hours to obtain a cathode material precursor Ni with an average particle size of 4.2 μm. 0.25 Fe 0.5 Mn 0.25 (OH)2@Fe 0.5 Mn 0.5 (OH)2 was obtained and is shown in Figures 1 and 2. Here, during the secondary coprecipitation reaction, the pH of the solution in the reaction vessel was maintained within the range of 9.5 to 10.5, and the concentration of the complexing agent in the solution in the reaction vessel was maintained within the range of 9 to 11 g / L.

[0080] (4) The positive electrode material precursor obtained in step (3), polyvinylpyrrolidone, and sodium carbonate were mixed uniformly in a mortar, and then calcined at a temperature of 800°C for 18 hours to obtain a cathode material having the chemical formula Na(Ni 0.25 Fe 0.5 Mn 0.25 )O2@Na 2 / 3 (Fe 0.5 Mn 0.5 )O2 cathode material was obtained. [Example]

[0081] This embodiment provides a method for preparing a positive electrode material, which includes the following steps: (1) Nickel sulfate, ferrous sulfate, and manganese sulfate were dissolved in deionized water in a molar ratio of 1 / 3:1 / 3:1 / 3 to prepare a first metal salt mixed solution having a total metal ion concentration of 1 mol / L, and ferrous sulfate and manganese sulfate were dissolved in deionized water in a molar ratio of 0.7:0.3 to prepare a second metal salt mixed solution having a total metal ion concentration of 2 mol / L. At the same time, an ammonia water complexing agent solution having a concentration of 2 mol / L and a sodium hydroxide solution having a concentration of 2 mol / L were prepared.

[0082] (2) Add deionized water, the ammonia water complexing agent solution obtained in step (1) and sodium hydroxide solution to a 200L reactor to form a base solution to maintain the stability of the system, where the total volume of the base solution is 100L, and control the ammonia water complexing agent concentration in the base solution within the range of 7-8g / L, and control the pH within the range of 10.5-11. Then, simultaneously inject the first metal salt mixed solution, the ammonia water complexing agent solution and the sodium hydroxide solution into the reactor at flow rates of 10kg / h, 2.5kg / h and 2.8kg / h, respectively, and carry out a primary coprecipitation reaction at a temperature of 52°C and a stirring speed of 350r / min for 75 hours to obtain a cathode material precursor core Ni with an average particle size of 3.6μm. 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 was obtained, and during the primary coprecipitation reaction, the pH of the solution in the reaction vessel was maintained within the range of 9.8 to 10.6, and the concentration of the complexing agent in the solution in the reaction vessel was maintained within the range of 8 to 10 g / L.

[0083] (3) The second metal salt mixed solution, the ammonia water complexing agent solution, and the sodium hydroxide solution were simultaneously injected into the reactor at flow rates of 10 kg / h, 3 kg / h, and 2.6 kg / h, respectively, and the secondary coprecipitation reaction was carried out at a temperature of 52°C and a stirring speed of 300 r / min for 8 hours to obtain a cathode material precursor Ni with an average particle size of 4 μm. 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2@Fe0.7 Mn 0.3 (OH)2 was obtained, and during the secondary coprecipitation reaction, the pH of the solution in the reaction vessel was maintained within the range of 9.5 to 10.5, and the concentration of the complexing agent in the solution in the reaction vessel was maintained within the range of 9 to 11 g / L.

[0084] (4) The positive electrode material precursor obtained in step (3), polyvinylpyrrolidone, and sodium carbonate were mixed uniformly in a mortar, and then baked at a temperature of 900°C for 16 hours to obtain a cathode material having the chemical formula Na(Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )O2@Na 0.7 (Fe 0.7 Mn 0.3 )O2 cathode material was obtained. [Example]

[0085] This embodiment provides a method for preparing a positive electrode material, which includes the following steps: (1) Nickel sulfate, ferrous sulfate, and manganese sulfate were dissolved in deionized water in a molar ratio of 0.2:0.5:0.3 to prepare a first metal salt mixed solution having a total metal ion concentration of 3 mol / L, and nickel sulfate and manganese sulfate were dissolved in deionized water in a molar ratio of 0.6:0.4 to prepare a second metal salt mixed solution having a total metal ion concentration of 1 mol / L. At the same time, an ammonia water complexing agent solution having a concentration of 1 mol / L and a sodium hydroxide solution having a concentration of 3 mol / L were prepared.

[0086] (2) Add deionized water, the ammonia water complexing agent solution obtained in step (1) and sodium hydroxide solution to a 200L reactor to form a base solution to maintain the stability of the system, where the total volume of the base solution is 100L, and the concentration of the ammonia water complexing agent in the base solution is controlled within the range of 9-10g / L, and the pH is controlled within the range of 10.6-11. Then, simultaneously inject the first metal salt mixed solution, the ammonia water complexing agent solution and the sodium hydroxide solution into the reactor at flow rates of 12kg / h, 3kg / h and 2.4kg / h, respectively, and carry out a primary coprecipitation reaction at a temperature of 40°C and a stirring speed of 380r / min for 60 hours to obtain a core Ni of a cathode material precursor with an average particle size of 2μm.0.2 Fe 0.5 Mn 0.3 (OH)2 was obtained, and the pH of the solution in the reaction vessel was maintained within the range of 9.8 to 11 during the primary coprecipitation reaction, and the concentration of the complexing agent in the solution in the reaction vessel was maintained within the range of 7 to 9 g / L.

[0087] (3) The second metal salt mixed solution, the ammonia water complexing agent solution, and the sodium hydroxide solution were simultaneously injected into the reactor at flow rates of 12 kg / h, 3 kg / h, and 2.4 kg / h, respectively, and the secondary coprecipitation reaction was carried out at a temperature of 40°C and a stirring speed of 350 r / min for 2 hours to obtain a cathode material precursor Ni with an average particle size of 2.5 μm. 0.2 Fe 0.5 Mn 0.3 (OH)2@Ni 0.6 Mn 0.4 (OH)2 was obtained, and during the secondary coprecipitation reaction, the pH of the solution in the reaction vessel was maintained within the range of 8.5 to 9.5, and the concentration of the complexing agent in the solution in the reaction vessel was maintained within the range of 8 to 10 g / L.

[0088] (4) The positive electrode material precursor obtained in step (3), polyvinylpyrrolidone, and sodium carbonate were mixed uniformly in a mortar, and then calcined at a temperature of 1000°C for 12 hours to obtain a cathode material having the chemical formula Na(Ni 0.2 Fe 0.5 Mn 0.3 )O2@Na 0.78 (Ni 0.6 Mn 0.4 )O2 cathode material was obtained. [Example]

[0089] This embodiment provides a method for preparing a positive electrode material, which includes the following steps: (1) Nickel sulfate, ferrous sulfate, and manganese sulfate were dissolved in deionized water in a molar ratio of 0.7:0.2:0.1 to prepare a first metal salt mixed solution having a total metal ion concentration of 4 mol / L, and ferrous sulfate and manganese sulfate were dissolved in deionized water in a molar ratio of 0.1:0.9 to prepare a second metal salt mixed solution having a total metal ion concentration of 4 mol / L. At the same time, an ammonia water complexing agent solution having a concentration of 1 mol / L and a sodium hydroxide solution having a concentration of 3 mol / L were prepared.

[0090] (2) Add deionized water, the ammonia water complexing agent solution obtained in step (1) and sodium hydroxide solution to a 200L reactor to form a base solution to maintain the stability of the system, where the total volume of the base solution is 100L, and control the ammonia water complexing agent concentration in the base solution within the range of 9-10g / L, and control the pH within the range of 10.6-11. Then, simultaneously inject the first metal salt mixed solution, the ammonia water complexing agent solution and the sodium hydroxide solution into the reactor at flow rates of 11kg / h, 1kg / h and 3kg / h, respectively, and carry out a primary coprecipitation reaction at a temperature of 60°C and a stirring speed of 300r / min for 90 hours to obtain a cathode material precursor core Ni with an average particle size of 4μm. 0.7 Fe 0.2 Mn 0.1 (OH)2 was obtained, and during the primary coprecipitation reaction, the pH of the solution in the reaction vessel was maintained within the range of 9.5 to 11, and the concentration of the complexing agent in the solution in the reaction vessel was maintained within the range of 9 to 11 g / L.

[0091] (3) The second metal salt mixed solution, the ammonia water complexing agent solution, and the sodium hydroxide solution were simultaneously injected into the reactor at flow rates of 11 kg / h, 1 kg / h, and 3 kg / h, respectively, and the secondary coprecipitation reaction was carried out at a temperature of 60°C and a stirring speed of 250 r / min for 6 hours to obtain a cathode material precursor Ni with an average particle size of 4.5 μm. 0.7 Fe 0.2 Mn 0.1 (OH)2@Fe 0.1 Mn 0.9 (OH)2 was obtained, and during the secondary coprecipitation reaction, the pH of the solution in the reaction vessel was maintained within the range of 10-11, and the concentration of the complexing agent in the solution in the reaction vessel was maintained within the range of 10-12 g / L.

[0092] (4) The positive electrode material precursor obtained in step (3), polyvinylpyrrolidone, and sodium carbonate were mixed uniformly in a mortar, and then calcined at a temperature of 800°C for 20 hours to obtain a cathode material having the chemical formula Na(Ni 0.7 Fe 0.2 Mn 0.1 )O2@Na 2 / 3 (Fe 0.1 Mn 0.9 )O2 cathode material was obtained. [Example]

[0093] The difference between this example and Example 1 is that the flow rate of the sodium hydroxide solution in step (2) is 3.5 kg / h, and the pH of the solution in the reactor is maintained within the range of 11.5 to 12.5 during the primary coprecipitation reaction. The remaining process parameters and operating conditions are the same as those in Example 1. [Example]

[0094] The difference between this example and Example 1 is that the flow rate of the sodium hydroxide solution in step (2) was 2 kg / h, and the pH of the solution in the reactor was maintained within the range of 8 to 9.2 during the primary coprecipitation reaction; the remaining process parameters and operating conditions were the same as those in Example 1. [Example]

[0095] The difference between this example and Example 1 is that the flow rate of the ammonia water complexing agent solution in step (2) is 4 kg / h, and the complexing agent concentration in the solution in the reactor during the primary coprecipitation reaction is maintained within the range of 11.5 to 13.5; the remaining process parameters and operating conditions are the same as those in Example 1. [Example]

[0096] The difference between this example and Example 1 is that the flow rate of the ammonia water complexing agent solution in step (2) is 0.5 kg / h, and the complexing agent concentration in the solution in the reactor during the primary coprecipitation reaction is maintained within the range of 5 to 6.5; the remaining process parameters and operating conditions are the same as those in Example 1. [Example]

[0097] The difference between this example and Example 1 is that the flow rate of the sodium hydroxide solution in step (3) was 3.5 kg / h, and the pH of the solution in the reactor was maintained within the range of 11.7 to 12.5 during the secondary coprecipitation reaction. The remaining process parameters and operating conditions were the same as those in Example 1. [Example]

[0098] The difference between this example and Example 1 is that the flow rate of the sodium hydroxide solution in step (3) was 2 kg / h, and the pH of the solution in the reactor was maintained within the range of 6.5 to 8 during the secondary coprecipitation reaction; the remaining process parameters and operating conditions were the same as those in Example 1. [Example]

[0099] The difference between this example and Example 1 is that the flow rate of the ammonia water complexing agent solution in step (3) is 4.5 kg / h, and the complexing agent concentration in the solution in the reactor during the primary coprecipitation reaction is maintained within the range of 12.5 to 14.5; the remaining process parameters and operating conditions are the same as those in Example 1. [Example]

[0100] The difference between this example and Example 1 is that the flow rate of the ammonia water complexing agent solution in step (3) is 0.3 kg / h, and the complexing agent concentration in the solution in the reactor during the primary coprecipitation reaction is maintained within the range of 6 to 7.5; the remaining process parameters and operating conditions are the same as those in Example 1. [Example]

[0101] The difference between this example and Example 1 is that the addition of polyvinylpyrrolidone in step (4) is omitted, while the remaining process parameters and operating conditions are the same as those in Example 1. Comparative Example 1

[0102] The difference between this comparative example and Example 1 is that the first metal salt mixed solution, the ammonia water complexing agent solution, and the sodium hydroxide solution required in step (2) were all placed in the reactor before the primary coprecipitation reaction was carried out; the remaining process parameters and operating conditions were the same as those in Example 1.

[0103] The difference between this comparative example and Example 1 is that the second metal salt mixed solution, the ammonia water complexing agent solution, and the sodium hydroxide solution required in step (3) were all placed in the reactor before the secondary coprecipitation reaction was carried out; the remaining process parameters and operating conditions were the same as those in Example 1.

[0104] The positive electrode materials prepared in Examples 1 to 13 and Comparative Examples 1 and 2 were assembled into coin batteries, and electrochemical performance tests were carried out.

[0105] The performance test parameters are as follows: (1) Reversible capacity test: Initial charge / discharge curve of half-cell at a current density of 12.5 (0.1C), and the voltage range was 2-4.2V.

[0106] (2) Cycle performance test: The half-cell was cycled 100 times at 1C, with a voltage range of 2-4.2V.

[0107] The positive electrode materials prepared in Examples 1 to 13 and Comparative Examples 1 and 2 were assembled into coin batteries, and their electrochemical performance test structures are shown in Table 1.

[0108] [Table 1]

[0109] The data in Table 1 reveal the following: (1) The positive electrode materials prepared in Examples 1 to 4 have high reversible capacity and excellent cycle performance, which means that the preparation method of the present application can be used to obtain a heterostructure positive electrode material having an O3 core and a P2 shell. In this case, the O3 core provides high capacity, and the P2 shell forms a stable interfacial layer. The synergistic effect of the two-phase structure achieves both high capacity and high cycle stability, further improving the electrochemical performance of sodium-ion batteries.

[0110] (2) The capacity and cycle performance of the positive electrode materials prepared in Examples 5 to 8 were all lower than those of Example 1. This was because the flow rate of the precipitant in the primary coprecipitation was too high in Example 5, too low in Example 6, too high in Example 7, and too low in Example 8. This suggests that by controlling the flow rates of the precipitant and complexing agent in the primary coprecipitation within appropriate ranges, the stability of the system throughout the primary coprecipitation reaction can be better maintained, contributing to the formation of a sparse core structure composed of flaky primary particles, and further improving the electrochemical performance of the positive electrode materials.

[0111] (3) The capacity and cycle performance of the positive electrode materials prepared in Examples 9 to 12 were all lower than those of Example 1. This was because the flow rate of the precipitant in the secondary coprecipitation was too high in Example 9, too low in Example 10, too high in Example 11, and too low in Example 12. Therefore, the present invention aims to maintain the stability of the system throughout the secondary coprecipitation reaction by controlling the flow rates of the precipitant and complexing agent within appropriate ranges, which contributes to the formation of a sparse shell structure composed of flaky primary particles deposited on the outer surface of the core, thereby further improving the electrochemical performance of the positive electrode material.

[0112] (4) The capacity and cycle performance of the positive electrode material prepared in Example 13 were both lower than those of Example 1. This was because the addition of a dispersant was omitted during the calcination process in Example 13, which prevented the sodium ions from effectively diffusing into the positive electrode material precursor particles during the calcination process, thereby affecting the electrochemical performance of the positive electrode material.

[0113] (5) The capacity and cycle performance of the positive electrode materials prepared in Comparative Examples 1 and 2 were all lower than that of Example 1. This is because in Comparative Example 1, the first metal salt mixed solution, complexing agent solution, and precipitant solution were all placed in a reactor to carry out the primary precipitation reaction, while in Comparative Example 2, the second metal salt mixed solution, complexing agent solution, and precipitant solution were all placed in a reactor to carry out the secondary precipitation reaction. These factors prevented the pH stability and complexing agent concentration stability from being effectively maintained during the primary and secondary coprecipitation reactions, making it impossible to adjust and control the rates of crystal nucleation and crystal growth during the primary and secondary coprecipitation reactions. As a result, a sparsely structured positive electrode material precursor composed of flaky primary particles could not be obtained, which further affected the electrochemical performance of the positive electrode material.

[0114] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto, and the applicant declares that it should be understood that any modifications or replacements that a person skilled in the art can easily conceive within the technical scope disclosed in the present application are all included in the scope of protection and disclosure of the present application.

Claims

1. A positive electrode material precursor for a sodium ion battery, comprising: The positive electrode material precursor includes a core and a shell surrounding the core, and the core is made of Ni. ｘ Fe ｙ Mn １－ｘ－ｙ (OH) ２ where 0.2≦x≦0.7 and 0.2≦y≦0.5, and the shell is M ａ Mn １－ａ (OH) ２ wherein M is nickel or iron, 0.05≦a≦0.7, and the core and the shell both have a loose structure formed by the accumulation of flake-like primary particles. A precursor to the positive electrode material of sodium-ion batteries.

2. The morphology of the core in the positive electrode material precursor includes a spherical or near-spherical shape. The positive electrode material precursor of claim 1 .

3. The particle size of the core in the positive electrode material precursor is 2 to 4.5 μm; The positive electrode material precursor of claim 1 .

4. The morphology of the positive electrode material precursor includes a spherical or near-spherical shape. The positive electrode material precursor of claim 1 .

5. The particle size of the positive electrode material precursor is 2.5 to 4.5 μm. The positive electrode material precursor of claim 1 .

6. A method for preparing a cathode material precursor according to any one of claims 1 to 5, comprising the steps of: the preparation method includes: continuously injecting a first metal salt mixed solution, a complexing agent solution, and a precipitant solution into a reactor simultaneously, and performing a primary coprecipitation reaction during the injection process to obtain a core of a positive electrode material precursor; and then continuously injecting a second metal salt mixed solution, the complexing agent solution, and the precipitant solution into the reactor simultaneously, and performing a secondary coprecipitation reaction during the injection process to obtain the positive electrode material precursor; During the primary coprecipitation reaction, the pH of the solution in the reactor is 9.5 to 11; During the primary coprecipitation reaction, the concentration of the complexing agent in the solution in the reactor is 7 to 11 g / L; the primary coprecipitation reaction is carried out under stirring, and the rotation speed of the stirring is 300 to 380 r / min; During the secondary coprecipitation reaction, the pH of the solution in the reactor is 8.5 to 11; During the secondary coprecipitation reaction, the concentration of the complexing agent in the solution in the reactor is 8 to 12 g / L; The secondary coprecipitation reaction is carried out under stirring, and the rotation speed of the stirring is 250 to 350 r / min. Preparation method.

7. The first metal salt mixed solution is prepared by mixing a nickel salt, an iron salt, a manganese salt, and a solvent. The preparation method according to claim 6.

8. the total concentration of metal ions in the first metal salt mixed solution is 1 to 4 mol / L; The preparation method according to claim 6.

9. the molar ratio of the nickel salt, the iron salt, and the manganese salt is x:y:(1-x-y), where 0.2≦x≦0.7 and 0.2≦y≦0.5; The preparation method according to claim 7.

10. The nickel salt includes any one of nickel sulfate, nickel chloride, and nickel nitrate. The preparation method according to claim 7.

11. The iron salt comprises ferrous sulfate or ferrous chloride. The preparation method according to claim 7.

12. The manganese salt includes any one of manganese sulfate, manganese chloride, and manganese nitrate. The preparation method according to claim 7.

13. The solvent comprises deionized water. The preparation method according to claim 7.

14. The concentration of the complexing agent solution is 1 to 3 mol / L; The preparation method according to claim 7.

15. The complexing agent comprises an ammonia water complexing agent; The preparation method according to claim 7.

16. The concentration of the precipitant is 1 to 3 mol / L; The preparation method according to claim 7.

17. The precipitating agent comprises an alkaline solution. The preparation method according to claim 7.

18. The alkaline solution includes a sodium hydroxide solution or a potassium hydroxide solution.

18. The method of claim 17.

19. In the primary coprecipitation reaction, the first metal salt mixed solution is injected into the reactor at a flow rate of 8 to 12 kg / h. The preparation method according to claim 6.

20. In the primary coprecipitation reaction, the complexing agent solution is injected into the reactor at a flow rate of 1 to 3 kg / h. The preparation method according to claim 6.

21. In the primary coprecipitation reaction, the precipitant solution is injected into the reactor at a flow rate of 2.4 to 3 kg / h. The preparation method according to claim 6.

22. The primary coprecipitation reaction is carried out at 40 to 60°C. The preparation method according to claim 6.

23. The time of the primary coprecipitation reaction is 60 to 90 hours; 7. The method of claim 6.

24. Before the primary coprecipitation reaction, deionized water, the complexing agent solution, and the precipitant solution are first added to the reactor to prepare a base solution for the primary coprecipitation reaction.

7. The method of claim 6.

25. The second metal salt mixed solution is prepared by mixing a nickel salt, a manganese salt, and a solvent, or the second metal salt mixed solution is prepared by mixing an iron salt, a manganese salt, and a solvent. The preparation method according to claim 6.

26. the total concentration of metal ions in the second metal salt mixed solution is 1 to 4 mol / L; 7. The method of claim 6.

27. the molar ratio of the nickel salt to the manganese salt is a:(1-a), or the molar ratio of the iron salt to the manganese salt is a:(1-a), with the proviso that 0.05≦a≦0.7; 26. The method of claim 25.

28. The nickel salt includes any one of nickel sulfate, nickel chloride, and nickel nitrate.

26. The method of claim 25.

29. The iron salt comprises ferrous sulfate or ferrous chloride.

26. The method of claim 25.

30. The manganese salt includes any one of manganese sulfate, manganese chloride, and manganese nitrate.

26. The method of claim 25.

31. The solvent comprises deionized water.

26. The method of claim 25.

32. In the secondary coprecipitation reaction, the second metal salt mixed solution is injected into the reactor at a flow rate of 8 to 12 kg / h.

7. The method of claim 6.

33. In the secondary coprecipitation reaction, the complexing agent solution is injected into the reactor at a flow rate of 1 to 3 kg / h.

7. The method of claim 6.

34. In the secondary coprecipitation reaction, the precipitant solution is injected into the reactor at a flow rate of 2.4 to 3 kg / h.

7. The method of claim 6.

35. The secondary coprecipitation reaction is carried out at 40 to 60°C.

7. The method of claim 6.

36. The time of the secondary coprecipitation reaction is 2 to 8 hours; 7. The method of claim 6.

37. A positive electrode material, The positive electrode material is prepared from the positive electrode material precursor according to any one of claims 1 to 5, The positive electrode material includes an O3 phase core and a P2 phase shell surrounding the O3 phase core, and the O3 phase core is formed of Na(Ni ｘ Fe ｙ Mn １－ｘ－ｙ ) O ２ where 0.2≦x≦0.7 and 0.2≦y≦0.5, and the P2 phase shell is Na ｂ (M ａ Mn １－ａ ) O ２ wherein M is nickel or iron, 0.05≦a≦0.7, and 0.67≦b≦0.78, and the O3 phase core and the P2 phase shell are both formed by deposition of flake-shaped primary particles. Positive electrode material.

38. mixing a positive electrode material precursor, a dispersant, and a sodium source, and then calcining the mixture to obtain the positive electrode material; 38. A method for preparing the cathode material of claim 37.

39. The dispersing agent comprises polyvinylpyrrolidone.

39. The method of claim 38.

40. the sodium source comprises sodium carbonate; 39. The method of claim 38.

41. the positive electrode material precursor, the dispersant, and the sodium source are mixed by grinding in a mortar; 39. The method of claim 38.

42. The firing temperature is 800 to 1000°C.

39. The method of claim 38.

43. The baking time is 12 to 20 hours.

39. The method of claim 38.

44. 38. The cathode material of claim 37, Sodium-ion battery.

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