Double-doped sodium battery positive electrode material precursor as well as preparation method and application thereof

Abstract

The invention provides a double-doped sodium battery positive electrode material precursor and a preparation method and application thereof, the chemical formula of the double-doped sodium battery positive electrode material precursor is NiaFebMncMd (OH) e, 0.1 < = a < = 0.35, 0.3 < = b < = 0.5, 0.15 < = c < = 0.6, 0.001 < = d < = 0.02, 1.8 < = e < = 2.2, and M is Nb and Mo. According to the double-doped sodium battery positive electrode material precursor provided by the invention, through double doping of Nb and Mo, the phase change of the corresponding positive electrode material in the circulation process is reduced, the damage to the structure is reduced, the structural stability of the positive electrode material is improved, meanwhile, the reversibility of the phase change in the charging and discharging process is also improved, and the impedance increase of the positive electrode material is inhibited; the problems that an existing iron-based sodium battery positive electrode material is low in structural stability and poor in electrochemical performance, and large-scale mass production and application cannot be achieved are solved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a cathode material precursor, particularly a double-doped sodium cathode material precursor and its preparation method and application. Background Technology

[0002] With the explosive growth of new energy vehicles, electric vehicles are increasingly appearing in people's lives, which places higher demands on power batteries. They need to have both good electrochemical performance and relatively low cost. Sodium-ion battery cathode materials, which have lower costs, are gradually attracting attention.

[0003] Sodium-ion battery layered oxide cathode materials have advantages such as relatively high specific capacity and low cost, and can be used as a substitute for lithium-ion battery cathodes. Once the technology matures, it can be applied to energy storage power stations and low-speed electric vehicles, reducing people's dependence on limited lithium and cobalt resources.

[0004] However, the layered oxide cathode of sodium-ion batteries still suffers from capacity decay and poor rate performance, which urgently need to be addressed. The stability of the layered structure during cycling is one of the main factors leading to the capacity decay of sodium-ion cathode materials.

[0005] CN116495802A discloses a method for preparing and applying a sodium-ion battery cathode material. The method includes: dissolving a sodium source, a nickel source, a ferrous source, a manganese source, and a salt containing a dopant element M in water to form a metal salt solution; adding a complexing agent solution to obtain a mixed solution; adjusting the mixed solution to alkalinity; adding nitrogen- and sulfur-containing organic compounds to the mixed solution; removing the solvent to form a sol; drying to obtain a gel and grinding it; subjecting the ground gel to a first heating sintering, cooling, pressing into a sheet, and then subjecting the pressed sample to a second heating sintering to obtain a layered oxide material for sodium-ion batteries. This method has a complex process flow, requires adjusting the mixed solution to alkalinity, results in poor elemental uniformity, produces a large amount of powder after grinding, and makes it difficult to ensure the consistency of the cathode material. Furthermore, it involves nitrogen- and sulfur-containing organic compounds, which poses a waste gas pollution problem during the sintering process.

[0006] Therefore, to address the shortcomings of existing technologies, there is a need to provide a structurally stable, double-doped sodium cathode material precursor, its preparation method, and its applications. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a dual-doped sodium-ion cathode material precursor, its preparation method, and its application. The dual-doped sodium-ion cathode material precursor, through the dual doping of Nb and Mo, not only reduces the phase transition of the corresponding cathode material during cycling, minimizing structural damage and improving the structural stability of the cathode material, but also enhances the reversibility of the phase transition during charge and discharge, suppressing the increase in impedance of the cathode material. This solves the problems of low structural stability, poor electrochemical performance, and inability to achieve large-scale mass production and application of current iron-based sodium-ion cathode materials.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a dual-doped sodium-ion cathode material precursor, wherein the chemical formula of the dual-doped sodium-ion cathode material precursor is Ni. a Fe b Mn c M d (OH) e , where 0.1≤a≤0.35, 0.3≤b≤0.5, 0.15≤c≤0.6, 0.001≤d≤0.02, 1.8≤e≤2.2, and M represents Nb and Mo.

[0010] The ionic radii of Nb and Mo are close to those of Fe. Co-doping with Nb and Mo can substitute for Fe sites without significantly altering the lattice parameters, thus maintaining the stability of the precursor material's crystal structure. Furthermore, Nb doping increases the mobility of sodium ions, while Mo doping reduces cation mixing in the lattice. The dual-doped sodium-based cathode material precursor provided by this invention, through the dual doping of Nb and Mo, not only reduces phase transitions in the corresponding cathode material during cycling, minimizing structural damage and improving the structural stability of the cathode material, but also enhances the reversibility of phase transitions during charge and discharge, suppressing the increase in cathode material impedance. This solves the problems of low structural stability, poor electrochemical performance, and the inability to achieve large-scale mass production and application of current iron-based sodium-based cathode materials.

[0011] The chemical formula of the dual-doped sodium cathode material precursor provided by this invention is Ni a Fe b Mn c M d (OH) e The value of a satisfies 0.1≤a≤0.35, for example, it can be 0.1, 0.15, 0.2, 0.25, 0.3 or 0.35, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0012] This invention, through the dual doping of Nb and Mo, can specifically improve the electrochemical performance of the dual-doped sodium cathode material precursor with Ni composition satisfying 0.1≤a≤0.35. When the Ni content is too high, the improvement of the precursor's electrochemical performance by Nb and Mo dual doping is limited.

[0013] The value of b satisfies 0.3≤b≤0.5. For example, it can be 0.3, 0.35, 0.4, 0.45 or 0.5, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] The value of c satisfies 0.15≤c≤0.6. For example, it can be 0.15, 0.2, 0.3, 0.4, 0.5 or 0.6, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] The value of d satisfies 0.001≤d≤0.02, for example, it can be 0.001, 0.005, 0.01, 0.015 or 0.02, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] The value of e satisfies 1.8≤e≤2.2. For example, it can be 1.8, 1.9, 2, 2.1 or 2.2, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, in the dual-doped sodium cathode material precursor, the molar ratio of nickel, ferrous iron, and manganese is (2-3):(2-4):(2-4), for example, it can be 3:3:3, 2:4:2, or 2:2:4, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In a second aspect, the present invention provides a method for preparing a dual-doped sodium cathode material precursor as described in the first aspect, the method comprising the following steps:

[0019] A mixed metal salt solution, a doped salt solution, a complexing agent solution, and a precipitant solution are subjected to a co-precipitation reaction to obtain the dual-doped sodium cathode material precursor.

[0020] The metal salts in the metal salt solution include nickel salt, ferrous salt and manganese salt in the prescribed amounts;

[0021] The doped salt in the doped salt solution includes niobium salt and molybdenum salt in the prescribed amounts.

[0022] The preparation method provided by the present invention also includes conventional aging, washing and drying after the coprecipitation reaction, and the present invention does not impose too many limitations on these.

[0023] Preferably, the nickel salt includes any one or a combination of at least two of nickel sulfate, nickel nitrate, nickel chloride, or nickel acetate. Typical but non-limiting combinations include combinations of nickel sulfate and nickel nitrate, nickel nitrate and nickel chloride, nickel chloride and nickel acetate, nickel sulfate, nickel nitrate and nickel chloride, nickel nitrate, nickel chloride and nickel acetate, or nickel sulfate, nickel nitrate, nickel chloride and nickel acetate.

[0024] Preferably, the ferrous salt includes any one or a combination of at least two of ferrous sulfate, ferrous nitrate, ferrous chloride, or ferrous acetate. Typical but non-limiting combinations include combinations of ferrous sulfate and ferrous nitrate, ferrous nitrate and ferrous chloride, ferrous chloride and ferrous acetate, ferrous sulfate, ferrous nitrate and ferrous chloride, ferrous nitrate, ferrous chloride and ferrous acetate, or combinations of ferrous sulfate, ferrous nitrate, ferrous chloride and ferrous acetate.

[0025] Preferably, the manganese salt includes any one or a combination of at least two of manganese sulfate, manganese nitrate, manganese chloride, or manganese acetate. Typical but non-limiting combinations include combinations of manganese sulfate and manganese nitrate, manganese nitrate and manganese chloride, manganese chloride and manganese acetate, manganese sulfate, manganese nitrate and manganese chloride, manganese nitrate, manganese chloride and manganese acetate, or manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.

[0026] Preferably, the niobium salt comprises any one or a combination of at least two of nickel sulfate, niobium nitrate, niobium chloride, or niobium acetate. Typical but non-limiting combinations include combinations of niobium sulfate and niobium nitrate, niobium nitrate and niobium chloride, niobium chloride and niobium acetate, niobium sulfate, niobium nitrate and niobium chloride, niobium nitrate, niobium chloride and niobium acetate, or niobium sulfate, niobium nitrate, niobium chloride and niobium acetate.

[0027] Preferably, the molybdenum salt includes any one or a combination of at least two of molybdenum sulfate, molybdenum nitrate, molybdenum chloride, or molybdenum acetate. Typical but non-limiting combinations include combinations of molybdenum sulfate and molybdenum nitrate, combinations of molybdenum nitrate and molybdenum chloride, combinations of molybdenum chloride and molybdenum acetate, combinations of molybdenum sulfate, molybdenum nitrate, and molybdenum chloride, combinations of molybdenum nitrate, molybdenum chloride, and molybdenum acetate, or combinations of molybdenum sulfate, molybdenum nitrate, molybdenum chloride, and molybdenum acetate.

[0028] Preferably, the complexing agent in the complexing agent solution includes any one or a combination of at least two of ammonia, acetic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), salicylic acid, or acetylacetone. Typical but non-limiting combinations include the combination of acetic acid and citric acid, the combination of ammonia and EDTA, and the combination of salicylic acid and acetylacetone.

[0029] Preferably, the precipitant in the precipitant solution includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate. Typical but non-limiting combinations include combinations of sodium hydroxide and potassium hydroxide, sodium carbonate and potassium carbonate, sodium hydroxide and sodium carbonate, potassium hydroxide and potassium carbonate, or combinations of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0030] For example, the concentration of the precipitant solution in this invention is 8-12 mol / L, such as 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L or 12 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the temperature of the coprecipitation reaction is 30-80℃, for example, it can be 30℃, 35℃, 40℃, 50℃, 70℃, 75℃ or 80℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 35-75℃.

[0032] Preferably, the pH value of the coprecipitation reaction is 6.5-13, for example, it can be 6.5, 7.5, 8.5, 9, 10, 12 or 13, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 8.5-12.

[0033] Preferably, the concentration of the complexing agent during the coprecipitation reaction is 0.17-1.0 mol / L, for example, it can be 0.17 mol / L, 0.2 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L or 1 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the target particle size D50 of the coprecipitation reaction is 3-15 μm, for example, it can be 3 μm, 5 μm, 8 μm, 10 μm, 12 μm or 15 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the coprecipitation reaction is carried out under stirring conditions, with a stirring speed of 180-1200 rpm, such as 180 rpm, 300 rpm, 500 rpm, 600 rpm, 800 rpm, 1000 rpm or 1200 rpm, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Thirdly, the present invention provides a dual-doped sodium-ion cathode material, wherein the dual-doped sodium-ion cathode material is prepared from the dual-doped sodium-ion cathode material precursor described in the first aspect, and has the chemical formula Na.x Ni a Fe b Mn c M d O e , where 0.5≤x≤1.5, 0.1≤a≤0.35, 0.3≤b≤0.5, 0.15≤c≤0.6, 0.001≤d≤0.02, 1.8≤e≤2.2, and M represents Nb and Mo.

[0037] The value of x satisfies 0.5≤x≤1.5. For example, it can be 0.5, 0.8, 1, 1.2 or 1.5, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] The value of 'a' satisfies 0.1 ≤ a ≤ 0.35. For example, it can be 0.1, 0.15, 0.2, 0.25, 0.3, or 0.35, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] The value of b satisfies 0.3≤b≤0.5. For example, it can be 0.3, 0.35, 0.4, 0.45 or 0.5, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] The value of c satisfies 0.15≤c≤0.6. For example, it can be 0.15, 0.2, 0.3, 0.4, 0.5 or 0.6, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] The value of d satisfies 0.001≤d≤0.02, for example, it can be 0.001, 0.005, 0.01, 0.015 or 0.02, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] The value of e satisfies 1.8≤e≤2.2. For example, it can be 1.8, 1.9, 2, 2.1 or 2.2, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Fourthly, the present invention provides a dual-doped sodium cathode material as described in the third aspect, the preparation method comprising the following steps:

[0044] The sodium source and the dual-doped sodium cathode material precursor described in the first aspect are mixed according to the formula amount and sintered to obtain the dual-doped sodium cathode material.

[0045] Preferably, the sodium source includes sodium carbonate.

[0046] Preferably, the sintering temperature is 600-1000℃, for example, it can be 600℃, 700℃, 800℃, 900℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] The sintering temperature is 8 hours or more, for example, it can be 8 hours, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, 20 hours or 25 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] The ionic radii of Nb and Mo are close to those of Fe. Co-doping with Nb and Mo can substitute for Fe sites without significantly altering the lattice parameters, thus maintaining the stability of the precursor material's crystal structure. Furthermore, Nb doping increases the mobility of sodium ions, while Mo doping reduces cation mixing in the lattice. The dual-doped sodium-based cathode material precursor provided by this invention, through the dual doping of Nb and Mo, not only reduces phase transitions in the corresponding cathode material during cycling, minimizing structural damage and improving the structural stability of the cathode material, but also enhances the reversibility of phase transitions during charge and discharge, suppressing the increase in cathode material impedance. This solves the problems of low structural stability, poor electrochemical performance, and the inability to achieve large-scale mass production and application of current iron-based sodium-based cathode materials. Detailed Implementation

[0051] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0052] Example 1

[0053] This embodiment provides a dual-doped sodium-ion cathode precursor, wherein the chemical formula of the dual-doped sodium-ion cathode material precursor is Ni. 0.33 Fe 0.33 Mn 0.34 Nb 0.006 Mo 0.003 (OH)2;

[0054] The preparation method of the dual-doped sodium cathode material precursor includes the following steps:

[0055] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the precursor of the double-doped sodium cathode material.

[0056] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes niobium sulfate and molybdenum sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0057] The complexing agent solution is ammonia water; the precipitant solution is a 10 mol / L sodium hydroxide solution;

[0058] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 0.5 mol / L, and a target particle size D50 of 12 μm.

[0059] Example 2

[0060] This embodiment provides a dual-doped sodium-ion cathode precursor, wherein the chemical formula of the dual-doped sodium-ion cathode material precursor is Ni. 0.33 Fe 0.33 Mn 0.34 Nb 0.0005 Mo 0.0005 (OH)2;

[0061] The preparation method of the dual-doped sodium cathode material precursor includes the following steps:

[0062] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the precursor of the double-doped sodium cathode material.

[0063] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes niobium sulfate and molybdenum sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0064] The complexing agent is ammonia; the precipitant solution is a 10 mol / L sodium hydroxide solution.

[0065] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 0.17 mol / L, and a target particle size D50 of 12 μm.

[0066] Example 3

[0067] This embodiment provides a dual-doped sodium-ion cathode precursor, wherein the chemical formula of the dual-doped sodium-ion cathode material precursor is Ni. 0.33 Fe 0.33 Mn 0.34 Nb 0.01 Mo 0.01 (OH)2;

[0068] The preparation method of the dual-doped sodium cathode material precursor includes the following steps:

[0069] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the precursor of the double-doped sodium cathode material.

[0070] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes niobium sulfate and molybdenum sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0071] The complexing agent solution is ammonia water; the precipitant solution is a 10 mol / L sodium hydroxide solution;

[0072] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 1 mol / L, and a target particle size D50 of 12 μm.

[0073] Example 4

[0074] This embodiment provides a dual-doped sodium-ion cathode precursor, wherein the chemical formula of the dual-doped sodium-ion cathode material precursor is Ni. 0.1 Fe 0.45 Mn 0.45 Nb 0.006 Mo 0.003 (OH)2;

[0075] The preparation method of the dual-doped sodium cathode material precursor includes the following steps:

[0076] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the precursor of the double-doped sodium cathode material.

[0077] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes niobium sulfate and molybdenum sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0078] The complexing agent solution is ammonia water; the precipitant solution is a 10 mol / L sodium hydroxide solution;

[0079] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 0.5 mol / L, and a target particle size D50 of 12 μm.

[0080] Example 5

[0081] This embodiment provides a dual-doped sodium-ion cathode precursor, wherein the chemical formula of the dual-doped sodium-ion cathode material precursor is Ni. 0.35 Fe 0.32 Mn 0.33 Nb 0.006 Mo 0.003 (OH)2;

[0082] The preparation method of the dual-doped sodium cathode material precursor includes the following steps:

[0083] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the precursor of the double-doped sodium cathode material.

[0084] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes niobium sulfate and molybdenum sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0085] The complexing agent solution is ammonia water; the precipitant solution is a 10 mol / L sodium hydroxide solution;

[0086] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 0.5 mol / L, and a target particle size D50 of 12 μm.

[0087] Example 6

[0088] This embodiment provides a double-doped sodium cathode precursor, which is the same as in Example 1 except that the pH value of the coprecipitation reaction is 8.5.

[0089] Example 7

[0090] This embodiment provides a double-doped sodium cathode precursor, which is the same as that in Example 1 except that the pH value of the coprecipitation reaction is 12.

[0091] Example 8

[0092] This embodiment provides a double-doped sodium cathode precursor, which is the same as in Example 1 except that the pH value of the coprecipitation reaction is 6.5.

[0093] Example 9

[0094] This embodiment provides a double-doped sodium cathode precursor, which is the same as that in Example 1 except that the pH value of the coprecipitation reaction is 13.

[0095] Comparative Example 1

[0096] This comparative example provides a dual-doped sodium-ion cathode precursor, the chemical formula of which is Ni. 0.4 Fe 0.3 Mn 0.3 Nb 0.006 Mo 0.003 (OH)2;

[0097] The preparation method of the dual-doped sodium cathode material precursor includes the following steps:

[0098] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the precursor of the double-doped sodium cathode material.

[0099] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes niobium sulfate and molybdenum sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0100] The complexing agent solution is ammonia water; the precipitant solution is a 10 mol / L sodium hydroxide solution;

[0101] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 0.5 mol / L, and a target particle size D50 of 12 μm.

[0102] Comparative Example 2

[0103] This comparative example provides a sodium-ion battery cathode precursor, the chemical formula of which is Ni. 0.33 Fe0.33 Mn 0.34 Nb 0.009 (OH)2;

[0104] The preparation method of the sodium-ion cathode material precursor includes the following steps:

[0105] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the sodium electrode material precursor.

[0106] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes niobium sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0107] The complexing agent solution is ammonia water; the precipitant solution is a 10 mol / L sodium hydroxide solution;

[0108] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 0.5 mol / L, and a target particle size D50 of 12 μm.

[0109] Comparative Example 3

[0110] This comparative example provides a sodium-ion battery cathode precursor, the chemical formula of which is Ni. 0.33 Fe 0.33 Mn 0.34 Mo 0.009 (OH)2;

[0111] The preparation method of the sodium-ion cathode material precursor includes the following steps:

[0112] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the sodium electrode material precursor.

[0113] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes molybdenum sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0114] The complexing agent solution is ammonia water; the precipitant solution is a 10 mol / L sodium hydroxide solution;

[0115] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 0.5 mol / L, and a target particle size D50 of 12 μm.

[0116] Comparative Example 4

[0117] This comparative example provides a dual-doped sodium-ion cathode precursor, the chemical formula of which is Ni. 0.33 Fe 0.33 Mn 0.34 Nb 0.006 Sb 0.003 (OH)2;

[0118] The preparation method of the dual-doped sodium cathode material precursor includes the following steps:

[0119] A mixed solution of metal salt and doped salt was obtained, and then a co-precipitation reaction was carried out with a complexing agent solution and a precipitating agent solution under a nitrogen atmosphere. After centrifugation, the mixture was washed until neutral and dried at 150°C to obtain the precursor of the double-doped sodium cathode material.

[0120] The metal salt in the metal salt solution includes nickel sulfate, ferrous sulfate and manganese sulfate in the prescribed amounts, and the doped salt in the doped salt solution includes niobium sulfate and molybdenum sulfate in the prescribed amounts. The total concentration of metal ions in the resulting mixture is 1.5 mol / L.

[0121] The complexing agent solution is ammonia water; the precipitant solution is a 10 mol / L sodium hydroxide solution;

[0122] The coprecipitation reaction was carried out under stirring at 360 rpm, at a temperature of 70°C, a pH of 10, a complexing agent concentration of 0.5 mol / L, and a target particle size D50 of 12 μm.

[0123] Performance Characterization

[0124] The cathode precursors obtained in the above examples and comparative examples were used to prepare cathode materials: sodium carbonate and cathode material precursors were mixed, calcined at 800°C for 25 hours in an oxygen atmosphere, and then ground and sieved to obtain cathode materials; wherein, the amount of sodium carbonate added was such that the molar ratio of Na to cathode material precursor was 1.02:1.

[0125] The obtained cathode material was used to prepare the battery to be tested.

[0126] The positive electrode material, binder polyvinylidene fluoride and conductive agent Super P were added to N-methylpyrrolidone at a mass ratio of 97:1.5:1.5 and stirred to form the first positive electrode slurry; then the first positive electrode slurry was uniformly coated on the positive electrode current collector aluminum foil, and after drying and rolling, the positive electrode sheet was obtained.

[0127] Graphite, conductive agent acetylene black, thickener CMC and binder SBR are mixed in a mass ratio of 96:1:1.5:1.5, and deionized water is added and stirred thoroughly to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on the negative electrode current collector copper foil, and after drying, cold pressing and slitting, a negative electrode sheet is obtained.

[0128] Ethylene carbonate EC, ethyl methyl carbonate EMC, and diethyl carbonate DEC were mixed in a volume ratio of 1:1:1. Then, fully dried lithium salt LiPF6 was dissolved in the mixed solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0129] The positive electrode, separator, and negative electrode are stacked in sequence, then wrapped with an aluminum-plastic film, dried, and injected with electrolyte. After encapsulation, settling, and formation processes, a lithium-ion battery is obtained. The separator is a PE porous membrane with a thickness of 11 μm, an air permeability of 280 s / 100 mL, and a porosity of 40%.

[0130] After the battery assembly was completed and aged for 12 hours, charge-discharge tests were conducted at different potentials. After activation at 2-4.2V voltage and 0.1C rate for 3 cycles, it was then cycled 100 times at 2C. The results are shown in Table 1.

[0131] Table 1

[0132]

[0133] As shown in Examples 1 to 3 of Table 1, the Nb and Mo dual-doped sodium cathode material precursor provided by this invention can achieve excellent cycle specific capacity and ultra-high capacity retention within the Nb and Mo doping amounts protected by the claims. This is because the ionic radii of Nb and Mo are close to those of Fe, and dual doping can stably occupy Fe sites without significantly changing the lattice parameters. At the same time, Nb increases the sodium ion mobility, and Mo reduces cation mixing. The synergistic effect of the two ensures the balanced optimization of material structural stability and electrochemical performance.

[0134] A comparison of Examples 4-5 with Example 1 shows that when the nickel-cobalt-manganese ratio is adjusted within the Ni content endpoint range defined in the claims, the material still maintains high cycle capacity and high capacity retention. This indicates that the Nb-Mo dual-doped system of the present invention has good compatibility with the nickel-cobalt-manganese ratio within the scope of the claims, and the stabilizing effect of dual doping on the structure can effectively offset the negative impact of Ni content fluctuations, thus broadening the process adaptability range of the material.

[0135] The comparison of Examples 6 to 9 shows that the pH value of the coprecipitation reaction has a significant impact on the material properties. When the pH value is at the preferred endpoint, the cycling specific capacity and capacity retention of the material are both higher than those at non-preferred endpoints. This is because the preferred pH value promotes uniform crystallization of the precursor and reduces lattice defects, while pH values ​​deviating from the preferred range can lead to precursor particle agglomeration or incomplete crystallization, thereby exacerbating structural damage and reducing capacity retention during cycling.

[0136] Comparisons of Comparative Examples 2 and 3 with Example 1 show that the electrochemical performance of materials with only Nb or Mo single doping is significantly worse than that with Nb and Mo dual doping. The cycle specific capacity of Nb-doped materials is 135 mAh / g with a capacity retention of 87.7%, and the cycle specific capacity of Mo-doped materials is 132 mAh / g with a capacity retention of 89.8%, both lower than the 140 mAh / g and 94.1% of Example 1. This is because single doping lacks synergistic effects: although Nb alone can improve sodium ion mobility, it cannot effectively suppress cation mixing, and lattice micro-distortions are prone to occur during long-term cycling; although Mo alone can reduce cation mixing, the sodium ion migration efficiency is insufficient, leading to increased impedance during charge and discharge. Ultimately, neither can simultaneously achieve high specific capacity and high cycle stability.

[0137] A comparison between Comparative Example 1 and Example 1 shows that excessively high Ni content leads to a significant decrease in the capacity retention of the material. The capacity retention of Comparative Example 1 is only 89.5%, far lower than the 94.1% of Example 1, even though its cycle specific capacity is close to that of Example 1. This is because high Ni content easily induces lattice distortion and cation mixing. Even with Nb and Mo dual doping, it is difficult to completely offset its destructive effect on structural stability, leading to increased irreversibility of phase transitions during cycling and accelerated capacity decay.

[0138] A comparison of Comparative Example 4 and Example 1 shows that replacing Mo with Sb significantly degrades the material performance. Comparative Example 4 exhibits the lowest cycling specific capacity (130 mAh / g) and capacity retention (86.5%) among all tested samples. This is because the ionic radius of Sb differs significantly from that of Fe, making it unable to effectively replace Fe sites. Consequently, Sb cannot exert its inhibitory effect on cation mixing, nor can it form a synergistic stable structure with Nb. This results in severe phase transitions and structural damage during cycling, leading to electrochemical performance significantly inferior to the Nb-Mo dual-doped system of this invention.

[0139] In summary, the ionic radii of Nb and Mo are close to those of Fe. Co-doping with Nb and Mo can substitute for Fe sites without significantly altering the lattice parameters, thus maintaining the stability of the precursor material's crystal structure. Furthermore, Nb doping increases the mobility of sodium ions, while Mo doping reduces cation mixing in the lattice. The dual-doped sodium-based cathode material precursor provided by this invention, through the dual doping of Nb and Mo, not only reduces phase transitions in the corresponding cathode material during cycling, minimizing structural damage and improving the structural stability of the cathode material, but also enhances the reversibility of phase transitions during charge and discharge, suppressing the increase in cathode material impedance. This solves the problems of low structural stability, poor electrochemical performance, and the inability to achieve large-scale mass production and application of current iron-based sodium-based cathode materials.

[0140] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A double-doped sodium electro-positive cathode material precursor, characterized in that, The chemical formula of the double-doped sodium electric positive electrode material precursor is Ni a Fe b Mn c M d (OH) e Wherein, 0.1≤a≤0.35, 0.3≤b≤0.5, 0.15≤c≤0.6, 0.001≤d≤0.02, 1.8≤e≤2.2, and M is Nb and Mo.

2. The dual-doped sodium electro-positive cathode material precursor of claim 1, wherein, The molar ratio of nickel, ferrous and manganese in the double-doped sodium battery cathode material precursor is (2-3) : (2-4) : (2-4).

3. A method for preparing the double-doped sodium electro-positive cathode material precursor of claim 1 or 2, characterized in that, The preparation method comprises the following steps: The mixed metal salt solution, the doping salt solution, the complexing agent solution and the precipitant solution are subjected to a co-precipitation reaction to obtain the double-doped sodium battery cathode material precursor. The metal salt in the metal salt solution comprises formula amount of nickel salt, ferrous salt and manganese salt. The doping salt in the doping salt solution comprises formula amount of niobium salt and molybdenum salt.

4. The production method according to claim 3, characterized by, The nickel salt comprises any one or combination of at least two of nickel sulfate, nickel nitrate, nickel chloride or nickel acetate; Preferably, the ferrous salt comprises any one or combination of at least two of ferrous sulfate, ferrous nitrate, ferrous chloride or ferrous acetate; Preferably, the manganese salt comprises any one or combination of at least two of manganese sulfate, manganese nitrate, manganese chloride or manganese acetate.

5. The production method according to claim 3 or 4, characterized by, The niobium salt comprises any one or combination of at least two of niobium sulfate, niobium nitrate, niobium chloride or niobium acetate; Preferably, the molybdenum salt comprises any one or combination of at least two of molybdenum sulfate, molybdenum nitrate, molybdenum chloride or molybdenum acetate.

6. The method of any one of claims 3-5, wherein, The complexing agent in the complexing agent solution comprises any one or combination of at least two of ammonia, acetic acid, citric acid, ethylenediaminetetraacetic acid, salicylic acid or acetylacetone; Preferably, the precipitant in the precipitant solution comprises any one or combination of at least two of sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate.

7. The method of any one of claims 3-6, wherein, The temperature of the co-precipitation reaction is 30-80°C; Preferably, the pH value of the co-precipitation reaction is 6.5-13, preferably 8.5-12; Preferably, the complexing agent concentration during the co-precipitation reaction is 0.17-1 mol / L; Preferably, the target particle size D50 of the co-precipitation reaction is 3-15 μm.

8. The preparation method according to claim 7, characterized in that, The co-precipitation reaction is carried out under stirring at a stirring speed of 180-1200 rpm.

9. A double doped sodium electro-positive cathode material, characterized in that, The double-doped sodium electric positive electrode material is prepared from the double-doped sodium electric positive electrode material precursor of claim 1 or 2, and has a chemical formula of Na x Ni a Fe b Mn c M d O e , wherein 0.5≤x≤1.5, 0.1≤a≤0.35, 0.3≤b≤0.5, 0.15≤c≤0.6, 0.001≤d≤0.02, 1.8≤e≤2.2, and M is Nb and Mo.

10. The double doped sodium electro-positive cathode material of claim 9, wherein, The preparation method comprises the following steps: The sodium source and the double-doped sodium battery cathode material precursor of claim 1 or 2 are mixed in formula amount, and sintered to obtain the double-doped sodium battery cathode material.

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