A positive electrode material precursor, a preparation method thereof, a positive electrode material, a positive electrode sheet, and a sodium-ion battery

Abstract

The application discloses a positive electrode material precursor, a preparation method of the positive electrode material precursor, a positive electrode material, a positive electrode sheet and a sodium ion battery. x Me y CO3 or Na x Me y (CO3) 1‑z B z , wherein 0.02<=x<=1.5y, x / 2+y<=1, 0.001<=z<=0.45, the Me is at least one of Mn, Fe, Ni, Co, Cu, Mg and Al elements; the B is at least one of HCO3 ‑ , OH ‑ , C2O4 2‑ anions. The positive electrode material precursor disclosed by the application has a high sodium content, reduces the amount of a subsequent sodium source, has a low sulfur content, and avoids forming non-active substances; the positive electrode material prepared by using the positive electrode material precursor has a structural stability, and does not need a protective atmosphere in the preparation process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a positive electrode material precursor, a preparation method thereof, a positive electrode material, a positive electrode sheet and a sodium ion battery. BACKGROUND

[0002] Compared with traditional energy storage systems, sodium ion batteries have the advantages of low cost, easy availability of raw materials, green environmental protection, safety and reliability. Sodium ion batteries are mainly composed of positive electrode materials, negative electrode materials, separators, electrolytes and the like, and the performance of the positive electrode material directly determines the electrochemical performance of the battery. At present, the positive electrode materials of sodium ion batteries in the industry mainly include the following types: oxide materials, polyanion materials, prussian blue analogues and organic electrode materials, etc. Among them, sodium ion battery oxide materials have attracted widespread attention due to their high compatibility with lithium ion battery positive electrode materials in terms of process and equipment. Generally, sodium ion battery oxide positive electrode materials are usually obtained by high-temperature sintering of a hydroxide precursor mixed with sodium salt.

[0003] A preparation method of a Fe-substituted Co ternary positive electrode material is disclosed in Chinese Patent CN114956202A, which comprises: preparing a mixed salt solution of Ni, Fe and Mn, using sodium hydroxide or potassium hydroxide as a precipitating agent, and using an ammonia solution as a complexing agent to prepare a precursor.

[0004] A preparation method of a quaternary positive electrode material precursor is disclosed in Chinese Patent CN115594233A, which comprises: preparing a solution of nickel salt and manganese salt; preparing a solution of soluble ferrous salt and magnesium salt containing a complexing agent; in an aqueous phase reaction system containing ammonia and a pH adjusting agent, passing in the solutions of nickel salt, manganese salt, ferrous salt and magnesium salt, and continuously passing in the ammonia solution and the pH adjusting agent solution to maintain the ammonia concentration and pH value in the aqueous phase reaction system, and performing a co-precipitation reaction to obtain a quaternary positive electrode material precursor.

[0005] A preparation method of a copper ion-doped nickel-iron-manganese-based ternary precursor is disclosed in Chinese Patent CN115924999A, which comprises: preparing a solution containing copper salt and nickel-iron-manganese salt; adding an ammonia solution and a sodium hydroxide solution with a certain concentration, adjusting the solution pH to 11.5, and after washing and drying, a copper ion-doped hydroxide precursor is prepared.

[0006] However, the sodium-electric positive electrode material precursor in the prior art has the following disadvantages: 1. The sodium content in the sodium-electric positive electrode material precursor is extremely low, and a large amount of sodium needs to be added subsequently; 2. Since the relative atomic mass and ion radius of sodium ions are larger than those of lithium ions, the resistance of migration in the solid crystal lattice is greater, the solid-phase diffusion speed during sintering is slower, the sodium ions in the sodium source are not easy to penetrate into the interior of the particles of the precursor, the sintering temperature required is high, the sintering time is long, and the sintering energy consumption is high; 3. The sodium-electric positive electrode material is prepared by using a hydroxide precursor, and the sodium content in the precursor is less than 300 ppm. SUMMARY

[0007] The present application aims at providing a positive electrode material precursor, solving the problems of low sodium content in the sodium-electric positive electrode material precursor and high sintering temperature and long sintering time required, and reducing the energy loss during sintering.

[0008] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A positive electrode material precursor, the chemical general formula of the positive electrode material precursor is Na x Me y CO3 or Na x Me y (CO3) 1-z B z , wherein 0.02≤x≤1.5y, x / 2+y≤1, 0.001≤z≤0.45, the Me is at least one of Mn, Fe, Ni, Co, Cu, Mg, Al elements; the B is at least one of HCO3 - , OH - , C2O4 2- anions.

[0010] Preferably, the XRD pattern of the positive electrode material precursor at a diffraction angle of 2θ includes the following characteristic peaks: characteristic peak F1: 19°-20°, characteristic peak F2: 31°-32°.

[0011] Preferably, the ratio F1 / F2 of the characteristic peak F1 to the characteristic peak F2 satisfies the relationship: 0.05≤(F1 / F2)≤20.

[0012] Preferably, the mass fraction of sodium element in the positive electrode material precursor is 0.3-17.8wt%, the mass fraction of Me element is 24-52wt%, the mass fraction of CO3 2- is 25-56wt%, and the molar ratio n(Na):n(Me) of the sodium element to the Me element is 2%-150%.

[0013] Preferably, the D50 median particle size of the positive electrode material precursor is 0.5-15μm.

[0014] The application further provides a preparation method of the positive electrode material precursor.

[0015] S1, preparing a Me metal element salt slurry: weighing Me metal element salt, adding water for ball milling to obtain the Me metal element salt slurry;

[0016] S2, preparing a sodium salt solution: weighing a sodium-containing compound, dissolving in water to obtain the sodium salt solution;

[0017] S3, preparing an additive: weighing oxalic acid or an oxalate salt, dissolving in water to obtain an additive 1, and weighing a surfactant as an additive 2;

[0018] S4, mixing the Me metal element salt slurry, the sodium salt solution, the additive 1 and the additive 2 to generate a precipitate, and spray drying at 110-180 ℃ to obtain the positive electrode material precursor.

[0019] Preferably, the molar ratio of sodium element to Me metal element in the sodium salt solution and the Me metal element salt slurry satisfies the relationship: n(Na):n(Me)≤1.5.

[0020] Preferably, the Me metal element salt is at least one of ferrous carbonate, manganese carbonate, copper carbonate, nickel carbonate and cobalt carbonate; the sodium-containing compound is at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxalate, sodium metaaluminate, sodium acetate, sodium citrate and sodium ascorbate; the oxalate salt is at least one of sodium oxalate, ammonium oxalate and ammonium hydrogen oxalate; and the surfactant is at least one of a cationic surfactant, an anionic surfactant, a nonionic surfactant, a combination of a cationic surfactant and a nonionic surfactant, and a combination of an anionic surfactant and a nonionic surfactant.

[0021] The application further provides a preparation method of the positive electrode material precursor.

[0022] S1, preparing a Me metal element salt solution: weighing Me metal element salt, dissolving in water to obtain the Me metal element salt solution;

[0023] S2, preparing a sodium salt solution: weighing a sodium-containing compound, dissolving in water to obtain the sodium salt solution;

[0024] S3, preparing an additive: weighing a surfactant as an additive;

[0025] S4, under the condition of coprecipitation, coprecipitating the Me metal element salt solution, the sodium salt solution and the additive to generate a precipitate;

[0026] S5, the obtained precipitate is washed with a sodium-containing solution, filtered to remove by-products, and the obtained filter cake is dried to obtain the positive electrode material precursor.

[0027] Preferably, the concentration of the Me metal element salt solution is 0.5-4.1 mol / L; the molar ratio of sodium element to Me metal element in the sodium salt solution and the Me metal element salt solution satisfies the relationship: n(Na):n(Me)≥2.0; the temperature of the sodium salt solution is 10-90℃; the mass fraction of sodium in the sodium salt solution is 1-15wt%; the drying temperature is 110-180℃, the drying time is 10-16h, and the end point of the drying is that the moisture content of the material is W≤1wt%.

[0028] Preferably, the Me metal element salt includes at least one of ferrous salt, manganese salt, copper salt, and nickel salt; the ferrous salt includes at least one of ferrous sulfate, ferrous nitrate, and ferrous chloride; the manganese salt includes at least one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; the copper salt includes at least one of copper sulfate, copper nitrate, copper acetate, and copper chloride; the nickel salt includes at least one of nickel sulfate, nickel nitrate, nickel acetate, and nickel chloride; the sodium-containing compound is at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium hydrogen oxalate, sodium metaaluminate, sodium acetate, sodium citrate, and sodium ascorbate; and the surfactant is at least one of cationic surfactant, anionic surfactant, non-ionic surfactant, combination of cationic surfactant and non-ionic surfactant, and combination of anionic surfactant and non-ionic surfactant.

[0029] The application further provides a positive electrode material, which is obtained by high-temperature sintering of the above-mentioned positive electrode material precursor.

[0030] Preferably, the high-temperature sintering includes primary sintering and secondary sintering in an air atmosphere; the primary sintering includes the following segmented heating operation:

[0031] 1) heating at a rate of 5-10℃ / min to 350-450℃, and holding for 1-2h;

[0032] 2) heating at a rate of 5-10℃ / min to 450-650℃, and holding for 1-2h;

[0033] 3) heating at a rate of 2-6℃ / min to 650-820℃, and holding for 1-6h;

[0034] The secondary sintering includes grinding the obtained product after the primary sintering is cooled to room temperature, and then performing the following segmented heating operation for sintering:

[0035] 1) heating at a rate of 5-10℃ / min to 450-650℃, and holding for 1-2h;

[0036] 2) heating at a rate of 2-6℃ / min to 650-780℃, and holding for 1-6h.

[0037] The application further provides a positive electrode sheet comprising the positive electrode material.

[0038] The application further provides a sodium ion battery comprising the positive electrode sheet.

[0039] The positive electrode material precursor of the application has the advantages that the sodium content in the positive electrode material precursor is high, so that the amount of sodium source used in the subsequent process can be reduced, the sulfur content in the positive electrode material precursor is low, so that non-active substances are avoided, the positive electrode material prepared by using the positive electrode material precursor has the characteristics of structural stability, and a protective atmosphere is not required in the preparation process; the sodium content in the precursor prepared by the prior art is less than 300ppm, because the radius of sodium ion is larger than that of lithium ion, the solid phase diffusion speed is slow during sintering, so that the sodium ions in the sodium source are not easy to penetrate into the interior of the particles of the precursor, while the sodium content in the precursor prepared by the application is high, and the particles contain sodium ions, so that the distance of solid phase diffusion of sodium ions is reduced during sintering, and the sintering energy consumption is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 XRD spectrum of the positive electrode material precursor of an embodiment of the application;

[0041] Figure 2 SEM image of the positive electrode material precursor of an embodiment of the application;

[0042] Figure 3 SEM image of the positive electrode material of an embodiment of the application;

[0043] Figure 4 XRD spectrum of the positive electrode material in the diffraction angle 2θ of Example 2 and Comparative Example 1 of the application;

[0044] Figure 5 Charge-discharge curve of the positive electrode material of an embodiment of the application at 3.8V 0.1C in a sodium ion battery. DETAILED DESCRIPTION

[0045] In order to make the technical solutions and advantages of the application clearer, the technical solutions of the application will be described clearly and completely below in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0046] In the first aspect according to the application, the application provides a positive electrode material precursor, the chemical general formula of the positive electrode material precursor is Nax Me y CO3 or Na x Me y (CO3) 1-z B z , wherein 0.02≤x≤1.5y, x / 2+y≤1, 0.001≤z≤0.45, Me is at least one of Mn, Fe, Ni, Co, Cu, Mg, Al elements; B is at least one of HCO3 - , OH - , C2O4 2- anions.

[0047] The positive electrode material precursor of the present application contains a high amount of sodium, which can reduce the amount of subsequent sodium source, and the positive electrode material precursor contains a low amount of sulfur, which avoids the formation of non-active substances; the positive electrode material prepared using the positive electrode material precursor has the characteristic of structural stability, and does not require a protective atmosphere during preparation; the prepared precursor has a high sodium content, and contains sodium ions in the particles, which reduces the solid-phase diffusion distance of sodium ions during sintering and reduces the sintering energy consumption.

[0048] In an embodiment according to the present application, the XRD pattern of the positive electrode material precursor at a diffraction angle of 2θ includes the following characteristic peaks: characteristic peak F1: 19°-20°, characteristic peak F2: 31°-32°.

[0049] In an embodiment according to the present application, the ratio F1 / F2 of the characteristic peak F1 to the characteristic peak F2 satisfies the relationship: 0.05≤(F1 / F2)≤20.

[0050] In an embodiment according to the present application, the mass fraction of sodium elements in the positive electrode material precursor is 0.3-17.8wt%, and specifically can be 0.3wt%, 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 3.0wt%, 4.0wt%, 5.0wt%, 6.0wt%, 7.0wt%, 8.0wt%, 9.0wt%, 10.0wt%, 11.0wt%, 12.0wt%, 13.0wt%, 14.0wt%, 15.0wt%, 16.0wt%, 17.0wt%, 17.8wt%; when the sodium content is controlled within the above range, the energy consumption can be reduced during sintering, because the prepared precursor has a high sodium content, and contains sodium ions in the particles, which reduces the solid-phase diffusion distance of sodium ions during sintering.

[0051] In an embodiment according to the present application, the mass fraction of Me elements is 24-52wt%, and specifically can be 24wt%, 28wt%, 30wt%, 32wt%, 35wt%, 40wt%, 42wt%, 45wt%, 48wt%, 50wt%, 52wt%; CO32- 25-56wt%, specifically, it can be 25wt%, 28wt%, 30wt%, 32wt%, 35wt%, 40wt%, 42wt%, 45wt%, 48wt%, 50wt%, 52wt%, 54wt%, 56wt%; if the mass fraction of Me element and CO3 2- If the mass fraction of Me element and CO3

[0052] In an embodiment according to the present application, the molar ratio of sodium element to Me element n(Na):n(Me) is 2%-150%, specifically, it can be 2%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%; 90%, 100%, 110%, 120%, 130%, 140%, 150%. When the molar ratio of sodium element to Me element is controlled within the above range, the energy consumption required during sintering can be reduced.

[0053] In an embodiment according to the present application, the D50 median particle size of the positive electrode material precursor is 0.5-15μm, specifically, it can be 0.5μm, 1.0μm, 2.0μm, 3.0μm, 4.0μm, 5.0μm, 6.0μm, 7.0μm, 8.0μm, 9.0μm, 10.0μm, 11.0μm, 12.0μm, 13.0μm, 14.0μm, 15.0μm.

[0054] In the second aspect according to the present application, the present application further provides a preparation method of the above-mentioned positive electrode material precursor, comprising the following steps:

[0055] S1, preparing Me metal element salt slurry: weighing Me metal element salt, adding water for ball milling to obtain Me metal element salt slurry;

[0056] S2, preparing sodium salt solution: weighing sodium-containing compound, dissolving in water to obtain sodium salt solution;

[0057] S3, preparing additives: weighing oxalic acid or oxalate, dissolving in water to obtain additive 1, weighing surfactant as additive 2;

[0058] S4, mixing Me metal element salt slurry, sodium salt solution, additive 1 and additive 2 to generate precipitation, and spray drying at 110-180℃ to obtain the positive electrode material precursor.

[0059] The preparation method of the above-mentioned positive electrode material precursor of the present application can only contain sodium sulfate impurities, and can also reduce the washing process.

[0060] The present application uses a spray dryer to dry the precipitate, and the specific steps include: preheating the spray dryer, setting the inlet temperature of the spray dryer to 170 DEG C, opening the cyclone to 100%, and the internal pressure of the instrument is between-50 to-70 Mpa; when the measured outlet temperature is greater than 120 DEG C, the sample speed is set to 2 ml / min, and the gas flow rate is 500 L / h. The deionized water tests the droplet situation sprayed at the nozzle, and when the sprayed mist droplets can be dried instantly and will not adhere to the inner wall of the glass spray cylinder, it can be used. After waiting for the inlet temperature and the outlet temperature to be stable, the mixed and uniform spray liquid is used to replace the deionized water to start sampling. After the spray liquid sampling is completed, the deionized water sampling is restarted, and the sampling is stopped after about 1 min, the heating program is turned off, and after the spray dryer is cooled to room temperature, the cyclone is turned off, and the obtained positive electrode material precursor solid powder sample is collected.

[0061] In an embodiment according to the present application, the molar ratio of sodium element to Me metal element in the sodium salt solution and the Me metal element salt slurry satisfies the relationship: n(Na):n(Me)≤1.5.

[0062] In an embodiment according to the present application, the Me metal element salt is at least one of ferrous carbonate, manganese carbonate, copper carbonate, nickel carbonate, and cobalt carbonate.

[0063] In an embodiment according to the present application, the sodium-containing compound is at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium hydrogen oxalate, sodium metaaluminate, sodium acetate, sodium citrate, and sodium ascorbate; preferably, it is sodium carbonate.

[0064] In an embodiment according to the present application, the oxalate is at least one of sodium hydrogen oxalate, ammonium oxalate, and ammonium hydrogen oxalate; preferably, it is sodium hydrogen oxalate.

[0065] In an embodiment according to the present application, the surfactant is at least one of a cationic surfactant, an anionic surfactant, a nonionic surfactant, a combination of a cationic surfactant and a nonionic surfactant, and a combination of an anionic surfactant and a nonionic surfactant; preferably, it is at least one of a fatty alcohol polyoxyethylene ether, a fatty acid polyoxyethylene ester, an alkyl polyglycoside, an alkyl alcohol amide, and an ethoxylated sorbitan fatty acid ester; more preferably, it is a fatty alcohol polyoxyethylene ether.

[0066] In a third aspect according to the present application, the present application further provides a preparation method of the above-mentioned positive electrode material precursor, which comprises the following steps:

[0067] S1, preparing a Me metal element salt solution: weighing the Me metal element salt, dissolving in water to obtain a Me metal element salt solution;

[0068] S2, preparing a sodium salt solution: weighing the sodium-containing compound, dissolving in water to obtain a sodium salt solution;

[0069] S3, a preparation aid: a surfactant is weighed as an aid;

[0070] S4, under co-precipitation conditions, the Me metal element salt solution, the sodium salt solution, and the aid are co-precipitated to generate a precipitate;

[0071] S5, the obtained precipitate is washed and filtered using a sodium-containing solution to remove by-products, and the obtained filter cake is dried to obtain a positive electrode material precursor.

[0072] In the method for preparing the positive electrode material precursor described above, the obtained precipitate is washed and filtered using a sodium-containing solution to remove sodium sulfate impurities, so as to obtain a pure positive electrode material precursor, thereby reducing energy loss during sintering.

[0073] In an embodiment according to the present application, the concentration of the Me metal element salt solution is 0.5-4.1 mol / L; specifically, it can be 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, or 4.1 mol / L.

[0074] In an embodiment according to the present application, the molar ratio of sodium to Me metal elements in the sodium salt solution and the Me metal element salt solution satisfies the relationship: n(Na):n(Me)≥2.0.

[0075] In an embodiment according to the present application, the temperature of the sodium salt solution is 10-90℃, specifically, it can be 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, or 90℃.

[0076] In an embodiment according to the present application, the mass fraction of sodium in the sodium salt solution is 1-15wt%, specifically, it can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, or 15wt%; the drying temperature is 110-180℃, specifically, it can be 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, or 180℃; the drying time is 10-16h, specifically, it can be 10h, 11h, 12h, 13h, 14h, 15h, or 16h; and the end point of drying is that the water content of the material is W≤1wt%.

[0077] In an embodiment according to the present application, the Me metal element salt includes at least one of ferrous salt, manganese salt, copper salt, and nickel salt.

[0078] In an embodiment according to the present application, the ferrous salt comprises at least one of ferrous sulfate, ferrous nitrate, ferrous chloride; preferably ferrous sulfate.

[0079] In an embodiment according to the present application, the manganese salt comprises at least one of manganese sulfate, manganese nitrate, manganese acetate, manganese chloride; preferably manganese sulfate.

[0080] In an embodiment according to the present application, the copper salt comprises at least one of copper sulfate, copper nitrate, copper acetate, copper chloride; preferably copper sulfate.

[0081] In an embodiment according to the present application, the nickel salt comprises at least one of nickel sulfate, nickel nitrate, nickel acetate, nickel chloride; preferably nickel sulfate.

[0082] In an embodiment according to the present application, the sodium-containing compound is at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium hydrogen oxalate, sodium metaaluminate, sodium acetate, sodium citrate, sodium ascorbate; preferably sodium carbonate.

[0083] In an embodiment according to the present application, the surfactant is at least one of cationic surfactant, anionic surfactant, nonionic surfactant, combination of cationic surfactant and nonionic surfactant, combination of anionic surfactant and nonionic surfactant; preferably at least one of fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ester, alkyl polyglycoside, alkylol amide, ethoxylated sorbitan fatty acid ester; more preferably fatty alcohol polyoxyethylene ether.

[0084] In a fourth aspect according to the present application, the present application further provides a positive electrode material, which is obtained by high-temperature sintering of the above-mentioned positive electrode material precursor.

[0085] In an embodiment according to the present application, the high-temperature sintering comprises a first sintering and a second sintering in an air atmosphere; the first sintering comprises the following segmented heating operation:

[0086] 1) heating at a rate of 5-10℃ / min to 350-450℃, and holding for 1-2h;

[0087] 2) heating at a rate of 5-10℃ / min to 450-650℃, and holding for 1-2h;

[0088] 3) heating at a rate of 2-6℃ / min to 650-820℃, and holding for 1-6h;

[0089] The second sintering comprises grinding the product obtained from the first sintering after cooling to room temperature, and then sintering by the following segmented heating operation:

[0090] 1) heating at a rate of 5-10℃ / min to 450-650℃, and holding for 1-2h;

[0091] 2) heating at a rate of 2-6℃ / min to 650-780℃, and holding for 1-6h.

[0092] The present application uses segmented sintering to make the connection between substances more closely, the substance with low melting point is first melted into liquid, and then the temperature is increased, because of the existence of liquid phase, which provides a channel for the diffusion of solid phase substances, and strengthens the solid phase diffusion reaction; in addition, the existence of liquid phase can wet the surface of solid particles, and by the action of surface tension, the particles are close, tight and rearranged, which is beneficial to expand the reaction interface between particles.

[0093] In a fifth aspect according to the present application, the present application further provides a positive electrode sheet comprising the positive electrode material described above.

[0094] In a sixth aspect according to the present application, the present application further provides a sodium ion battery comprising the positive electrode sheet described above.

[0095] The sodium ion battery provided by the present application further comprises an electrolyte, which is composed of an organic solvent and an electrolyte sodium salt. The organic solvent can be selected from one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonate, diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and methyl tert-butyl ether; and the electrolyte sodium salt can be selected from at least one of sodium hexafluorophosphate, sodium bisfluorosulfonylimide, sodium bis(trifluoromethanesulfonyl)imide, sodium triflate, sodium tetrafluoroborate, sodium difluorophosphate and sodium perchlorate.

[0096] The present application will be further described below through specific embodiments.

[0097] Embodiment 1

[0098] The present application provides a preparation method of a positive electrode material precursor, wherein the molar ratio of sodium element and transition metal element Me is n(Na):n(Me)≤1.5, and the specific steps are as follows:

[0099] Step S1, according to the stoichiometric ratio of metal elements nickel, manganese and copper, 0.2:0.75:0.05, ferrous carbonate, manganese carbonate and copper carbonate are weighed, a total of 1 mol, dispersed in 500 mL of water, and a transition metal salt slurry is prepared;

[0100] Step S2, weigh 53.53g of sodium carbonate, dissolve in 250mL of water to prepare a sodium salt solution;

[0101] Step S3, weigh 63.04g of dihydrate oxalic acid, dissolve in 250mL of water to prepare an auxiliary agent 1;

[0102] Step S4, weigh 0.50 g of ethoxylated sorbitan fatty acid ester (PEG-60) as an auxiliary agent 2;

[0103] Step S5, mix the transition metal salt slurry, sodium salt solution, auxiliary agent 1, and auxiliary agent 2 to obtain a spraying liquid; preheat the spray dryer, set the inlet temperature of the spray dryer to 170℃, the cyclone is opened at 100%, and the internal pressure of the instrument is between-50 and-70 MPa. After the outlet temperature is measured to be greater than 120℃, the sample injection speed is set to 2 ml / min, and the gas flow rate is 500 L / h. Deionized water is used to test the droplet situation sprayed at the nozzle, and when the sprayed mist droplets can be dried instantly and will not adhere to the inner wall of the glass spray cylinder, the inlet and outlet temperatures are waited to be stable, and the mixed and uniform spraying liquid is used to replace the deionized water to start sampling. After the spraying liquid sampling is completed, the deionized water sampling is restarted, and the sampling is stopped after about 1 min. The heating program is turned off, and after the spray dryer is cooled to room temperature, the cyclone is turned off, and the obtained positive electrode material precursor solid powder sample is collected.

[0104] The positive electrode material precursor prepared by the above method is obtained by high-temperature solid-phase sintering to obtain a positive electrode material, which specifically includes first sintering and second sintering, and the specific steps are as follows: the positive electrode material precursor is loaded into a sagger and placed in a muffle furnace, first heated to 450℃ at a rate of 6℃ / min, and kept for 2 h; then heated to 650℃ at a rate of 6℃ / min, and kept for 2 h; finally, heated to 820℃ at a rate of 4℃ / min, and kept for 6 h to complete the first sintering; after cooling to room temperature, the obtained material is ground, loaded into a sagger, and placed in a muffle furnace for secondary sintering, first heated to 650℃ at a rate of 6℃ / min, and kept for 2 h; then heated to 780℃ at a rate of 4℃ / min, and kept for 6 h; finally, cooled with the furnace to obtain a sodium battery positive electrode material. The entire solid-phase sintering atmosphere is an air atmosphere.

[0105] Example 2

[0106] In this embodiment, the molar ratio n(Na):n(Me) of the sodium element and the transition metal element Me is ≥2.0, and the specific steps are as follows:

[0107] Step S1, according to the stoichiometric ratio of metal elements nickel, manganese, and copper being 0.2:0.75:0.05, weigh 56.73 g of nickel sulfate heptahydrate, 127.17 g of manganese sulfate monohydrate, and 12.50 g of copper sulfate pentahydrate, dissolve in 940 g of water to prepare a mixed salt solution;

[0108] Step S2, weigh 137.78 g of sodium carbonate, add 500 g of water to prepare a Na2CO3 solution;

[0109] Step S3, weigh 0.30 g of fatty alcohol polyoxyethylene ether (AEO9) as an additive;

[0110] Step S4, the additive is added to the reaction kettle containing 200 mL of deionized water, and then the Na2CO3 solution and the mixed salt solution are added to the reaction kettle for mixing and stirring to carry out coprecipitation reaction to obtain a precipitate product; wherein the temperature of the reaction kettle is 80°C, the stirring speed of the stirrer is 2000 rpm, and the feeding speed is 1 mL / min,

[0111] Step S5, the precipitate product is aged at 70°C for 12 h, suction filtered, and the filter cake and filtrate are separated, washed with a sodium carbonate solution for 3 times, and oven dried at 120°C to constant weight to obtain a positive electrode material precursor, wherein the mass content of Na is 1.9%.

[0112] The embodiment also provides a preparation method of a positive electrode material, comprising the following steps:

[0113] S1, 120.25 g of the positive electrode material precursor prepared by the preparation method is mixed with 24.21 g of sodium carbonate, wherein the addition amount of sodium carbonate is weighed according to the stoichiometric ratio n(Na):n(Me) of 0.9:1, and the mixing mode is high-speed mixing of solid powder.

[0114] S2, the mixture is loaded into a sagger and placed in a muffle furnace, first heated to 450°C at a rate of 6°C / min, and kept for 2 h; then heated to 650°C at a rate of 6°C / min, and kept for 2 h; finally heated to 820°C at a rate of 4°C / min, and kept for 6 h to complete the first sintering; after cooling to room temperature in the furnace, the obtained material is ground, loaded into a sagger and placed in a muffle furnace for secondary sintering, first heated to 650°C at a rate of 6°C / min, and kept for 2 h; then heated to 780°C at a rate of 4°C / min, and kept for 6 h; finally cooled in the furnace to obtain a positive electrode material. The whole solid-phase sintering atmosphere is an air atmosphere.

[0115] Example 3

[0116] The difference between this embodiment and examples 1 and 2 is that the transition metal element Me is Fe, Mn and Cu, and the stoichiometric ratio is 3:6:1. The rest is the same as examples 1 and 2, which will not be repeated here.

[0117] Example 4

[0118] The difference between this embodiment and examples 1 and 2 is that the transition metal element Me is Ni, Mn and Cu. The rest is the same as examples 1 and 2, which will not be repeated here.

[0119] Example 5

[0120] The difference between this embodiment and embodiments 1 and 2 is that the transition metal element Me is Fe, Mn, or Ni. The rest is the same as in embodiments 1 and 2, and will not be repeated here.

[0121] Example 6

[0122] The difference between this embodiment and embodiments 1 and 2 is that the transition metal element Me is Fe, Mn, Ni, or Cu. The rest is the same as in embodiments 1 and 2, and will not be repeated here.

[0123] Example 7

[0124] The difference between this embodiment and Embodiments 1 and 2 is that the transition metal element Me is Fe, Mn, Ni, or Mg. The rest is the same as in Embodiments 1 and 2, and will not be repeated here.

[0125] Comparative Example 1

[0126] The difference between this comparative example and Examples 1 and 2 is that the method for preparing the precursor is different, and the specific steps are as follows:

[0127] S1. Nickel-manganese-copper hydroxide was prepared by co-precipitation using sodium hydroxide and ammonia as raw materials. After washing and drying, the precursor for the cathode material was obtained. ICP analysis showed that the sodium content was 170 ppm.

[0128] S2. Mix the positive electrode material precursor with sodium carbonate, wherein the amount of sodium is stoichiometric in the form of n(Na):n(Me) of 1.05:1, and the mixing method is direct mechanical stirring of solid powder.

[0129] Performance testing

[0130] (1) The cathode material precursors prepared in Examples 1-7 were subjected to XRD tests at a diffraction angle of 2θ. The test results are as follows: Figure 1 As shown; the cathode material precursors prepared in Examples 1-7 were subjected to SEM testing, and the test results are as follows. Figure 2 As shown.

[0131] (2) The cathode materials prepared in Examples 1-7 were subjected to SEM testing, and the test results are as follows: Figure 3 As shown.

[0132] (3) The cathode materials prepared in Example 2 and Comparative Example 1 were subjected to XRD tests at a diffraction angle of 2θ. The test results are as follows: Figure 4 As shown.

[0133] (4) The positive electrode materials prepared in Examples 1-7 were used in sodium-ion batteries and charge-discharge tests were conducted at 3.8V and 0.1C. The test results are as follows: Figure 5 As shown.

[0134] Results Analysis

[0135] (1) From Figure 1 As can be seen from the data, the cathode material precursor has the following characteristic peaks: F1: 19°~20°, F2: 31°~32°, and the ratio of characteristic peak F1 to characteristic peak F2 satisfies the following relationship: 0.05≤(F1 / F2)≤20.

[0136] (2) From Figure 2 As can be clearly seen, the cathode material precursor is spherical.

[0137] (3) From Figure 3 The good crystallinity of the cathode material can be clearly seen.

[0138] (4) From Figure 4 It can be seen that the cathode material prepared by the present invention does not have impurity peaks, while the cathode material prepared by the method of Comparative Example 1 has obvious impurity peaks formed by Ni, Mn and O. The reason is that the radius of sodium ions is larger than that of lithium ions, and the solid-phase diffusion rate is slower during sintering, which makes it difficult for sodium ions in the sodium source to penetrate into the interior of the precursor particles, i.e., the sodium ion diffusion is uneven. The precursor prepared by the present invention has a high sodium content and contains sodium ions in the particles, which reduces the distance of sodium ion solid-phase diffusion during sintering, making the sodium ion diffusion more uniform, and also reducing the sintering energy consumption.

[0139] (5) From Figure 5 It can be seen that the discharge specific capacity of the cathode material prepared by this invention is 121.5 mAh / g.

[0140] In summary, the cathode material precursor of the present invention has a high sodium content, which can reduce the amount of sodium source used in the subsequent process; the cathode material precursor has a low sulfur content, which avoids the formation of inactive substances; the cathode material prepared using the cathode material precursor has a stable structure and does not require a protective atmosphere during the preparation process.

[0141] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A cathode material precursor, characterized in that, The general chemical formula of the cathode material precursor is Na. x Me y CO3 or Na x Me y (CO3) 1-z B z Wherein, 0.02≤x≤1.5y, x / 2+y≤1, 0.001≤z≤0.45, and Me is at least one of Mn, Fe, Ni, Co, Cu, Mg, and Al; and B is HCO3. - OH - C2O4 2- At least one of the anions; the XRD pattern of the cathode material precursor at a diffraction angle of 2θ includes the following characteristic peaks: characteristic peak F1: 19°~20°, characteristic peak F2: 31°~32°; the ratio of characteristic peak F1 to characteristic peak F2, F1 / F2, satisfies the relationship: 0.05≤(F1 / F2)≤20; the cathode material precursor is prepared by any of the following methods: Preparation method 1: S1. Preparation of Me metal element salt slurry: Weigh the Me metal element salt, add water and ball mill to obtain Me metal element salt slurry; S2. Preparation of sodium salt solution: Weigh out the sodium-containing compound, dissolve it in water to obtain a sodium salt solution; S3. Preparation of auxiliary agents: Weigh out oxalic acid or oxalate, dissolve it in water to obtain auxiliary agent 1, and weigh out the surfactant as auxiliary agent 2. S4. Mix the Me metal element salt slurry, sodium salt solution, additive 1, and additive 2 to form a precipitate, and spray dry at 110~180℃ to obtain the cathode material precursor. Preparation method two: S1. Preparation of Me metal element salt solution: Weigh out Me metal element salt, add water to dissolve it, and obtain Me metal element salt solution; S2. Preparation of sodium salt solution: Weigh out the sodium-containing compound, dissolve it in water to obtain a sodium salt solution; S3. Preparation of additives: Weigh out the surfactant as an additive; S4. Under co-precipitation conditions, the Me metal element salt solution, sodium salt solution, and auxiliary agent are co-precipitated to form a precipitate; S5. The obtained precipitate is washed and filtered with a sodium-containing solution to remove byproducts. The dried filter cake is the precursor of the positive electrode material.

2. The cathode material precursor according to claim 1, characterized in that, The precursor of the cathode material contains sodium with a mass fraction of 0.3-17.8 wt% and me with a mass fraction of 24-52 wt%; the CO3... 2- The mass fraction is 25~56wt%; the molar ratio of sodium to Me is n(Na):n(Me) = 2%~150%.

3. The cathode material precursor according to claim 1, characterized in that, The median D50 particle size of the cathode material precursor is 0.5~15μm.

4. The cathode material precursor according to claim 1, characterized in that, In preparation method one, the molar ratio of sodium to Me in the sodium salt solution and the Me metal element salt slurry satisfies the following relationship: n(Na):n(Me)≤1.

5.

5. The cathode material precursor according to claim 1, characterized in that, In preparation method one, the Me metal element salt is at least one of ferrous carbonate, manganese carbonate, copper carbonate, nickel carbonate, and cobalt carbonate; the sodium-containing compound is at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium bioxalate, sodium aluminate, sodium acetate, sodium citrate, and sodium ascorbate; the oxalate is at least one of sodium bioxalate, ammonium oxalate, and ammonium bioxalate; and the surfactant is at least one of cationic surfactant, anionic surfactant, nonionic surfactant, a combination of cationic and nonionic surfactants, or a combination of anionic and nonionic surfactants.

6. The cathode material precursor according to claim 1, characterized in that, In preparation method two, the concentration of the Me metal element salt solution is 0.5~4.1 mol / L; the molar ratio of sodium to Me metal element in the sodium salt solution and the Me metal element salt solution satisfies the relationship: n(Na):n(Me)≥2.0; the temperature of the sodium salt solution is 10-90℃; the mass fraction of sodium in the sodium salt solution is 1~15wt%; the drying temperature is 110-180℃, the drying time is 10-16h, and the drying endpoint is that the moisture content of the material W≤1wt%.

7. The cathode material precursor according to claim 1, characterized in that, In preparation method two, the Me metal element salt includes at least one of ferrous salt, manganese salt, copper salt, and nickel salt; the ferrous salt includes at least one of ferrous sulfate, ferrous nitrate, and ferrous chloride; the manganese salt includes at least one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; the copper salt includes at least one of copper sulfate, copper nitrate, copper acetate, and copper chloride; the nickel salt includes at least one of nickel sulfate, nickel nitrate, nickel acetate, and nickel chloride; the sodium-containing compound is at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium bioxalate, sodium aluminate, sodium acetate, sodium citrate, and sodium ascorbate; and the surfactant is at least one of cationic surfactant, anionic surfactant, nonionic surfactant, a combination of cationic and nonionic surfactant, or a combination of anionic and nonionic surfactant.

8. A positive electrode material, characterized in that, It is obtained by high-temperature sintering of the cathode material precursor as described in any one of claims 1-7.

9. The cathode material according to claim 8, characterized in that, The high-temperature sintering includes primary sintering and secondary sintering in an air atmosphere; the primary sintering includes the following segmented heating operation: 1) Increase the temperature to 350-450℃ at a rate of 5-10℃ / min and hold for 1-2 hours; 2) Increase the temperature to 450-650℃ at a rate of 5-10℃ / min and hold for 1-2 hours; 3) Increase the temperature to 650-820℃ at a rate of 2-6℃ / min and hold for 1-6 hours; The secondary sintering involves cooling the product obtained from the primary sintering to room temperature, grinding it, and then performing sintering using the following segmented heating operation: 1) Increase the temperature to 450-650℃ at a rate of 5-10℃ / min and hold for 1-2 hours; 2) Heat to 650-780℃ at a rate of 2-6℃ / min and hold for 1-6 hours.

10. A positive electrode plate, characterized in that, Includes the cathode material described in any one of claims 8-9.

11. A sodium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 10.

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