Sodium-ion battery positive electrode precursor having core-shell structure, manufacturing method therefor, and use thereof

Abstract

Provided in the present application are a sodium-ion battery positive electrode precursor having a core-shell structure, a manufacturing method therefor, and the use thereof. Said precursor comprises a core and a shell on the surface of the core, the core comprising NiaFebMn1-a-b-cMc(OH)2, wherein 0.3≤a≤0.5, 0.2≤b≤0.4 and 0≤c≤0.01, and the shell comprising NixCuyFezMn1-x-y-z-vNv(OH)2, wherein 0.1≤x<0.3, 0.02≤y≤0.2, 0.2≤z≤0.4 and 0≤v≤0.01, and the shell containing pores. In said precursor of the present application, primary particles of the core are of a dense packing while primary particles of the shell are of a loose packing, so that compaction density, energy density, porosity and specific surface area of the material are improved, thus improving properties of the material.

Description

A core-shell structure sodium battery positive electrode precursor, a preparation method and application thereof TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and relates to a core-shell structure sodium battery positive electrode precursor, a preparation method and application thereof. BACKGROUND

[0002] With the rapid development and popularization of renewable energy such as solar energy and wind energy, people's demand for energy storage to cope with the volatility and intermittency of renewable energy is increasing. Traditional power systems are difficult to cope with such volatility, so large-scale energy storage technology is needed to balance the supply-demand difference. At present, lithium ion batteries are one of the most common commercial energy storage technologies. However, the scarcity of lithium resources and the instability of the supply chain have led to high costs of lithium batteries, and lithium batteries also have certain safety hazards. Therefore, it is crucial to find alternative energy storage technologies.

[0003] Sodium and lithium are adjacent elements in the same main group, and have similar physical and chemical properties. Therefore, sodium ion batteries have similar structure and working principle to lithium ion batteries, and sodium resources on earth are abundant and widely distributed, and are considered to be a high-performance lithium ion battery alternative in the field of large-scale energy storage. Developing high-performance electrode materials is the focus of sodium ion battery research. Transition metal layered oxides as positive electrode materials for sodium ion batteries have high specific capacity, are easy to industrialize, and are attracting more and more attention. However, layered oxides still face many challenges, such as irreversible phase transition, storage instability, insufficient performance, etc., which seriously restrict the commercialization process of sodium ion batteries. Preparing high-quality precursor materials is the key to solving this problem.

[0004] CN115196691A discloses a nickel-iron-manganese ternary precursor for sodium ion batteries, a preparation method and application thereof. The preparation method comprises: making a ferrous salt, a nickel salt, a manganese salt and a hydroxide co-precipitate in a solvent in the presence of a complexing agent to generate a nickel-iron-manganese ternary precursor; and making the co-precipitation reaction under the condition of a first pH value (11.3-11.5) to form new crystal nuclei; after the formation of new crystal nuclei is completed, the pH value is adjusted, and the co-precipitation reaction is carried out under the condition of a second pH value (10.5-11.0) until it grows to a preset median particle size, and the difference between the first pH value and the second pH value and the concentration of the complexing agent are controlled within a certain range. However, the air stability of the prepared sodium nickel-iron-manganese oxide positive electrode material is poor, which is not conducive to the production, transportation and storage of the material, and the high nickel content increases the manufacturing cost.

[0005] Therefore, the sodium-ion battery layered oxide positive electrode material still faces problems such as irreversible changes in electrochemical processes, instability in air storage, and poor interface stability, and although the sodium resource is relatively abundant, some metal resources such as nickel used for the preparation of layered oxides are still limited and expensive, and further reducing the cost is an inevitable requirement to improve the market competitiveness of sodium-ion batteries. SUMMARY

[0006] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0007] The present application provides a core-shell structure sodium battery positive electrode precursor and a preparation method and application thereof, the core of the core-shell structure sodium battery positive electrode precursor is once particle accumulation dense, which is beneficial to improve the compaction density and energy density of the material, the shell adds copper element, which can improve the stability while reducing the cost, and the once particle of the shell adopts loose accumulation, which improves the porosity and specific surface area, thereby promoting the capacity of the material.

[0008] In a first aspect, the present application provides a core-shell structure sodium battery positive electrode precursor, the core-shell structure sodium battery positive electrode precursor comprises a core and a shell on the surface of the core, the core comprises Ni a Fe b Mn 1-a-b-c M c (OH)2, wherein 0.3≤a≤0.5, 0.2≤b≤0.4, and 0≤c≤0.01; the shell comprises Ni x Cu y Fe z Mn 1-x-y-z-v N v (OH)2, wherein 0.1≤x<0.3, 0.02≤y≤0.2, 0.2≤z≤0.4, and 0≤v≤0.01; M and N independently comprise a doped metal element, and the shell contains pores.

[0009] The main component elements of the core of the present application are nickel, iron and manganese, the once particle is accumulated dense, which is beneficial to improve the compaction density and energy density of the material; the shell adds copper element to reduce the content of nickel element, so as to improve the air stability of the material and reduce the overall cost of the material, and the once particle of the shell adopts loose accumulation, which improves the porosity and specific surface area, and is beneficial to the capacity of the material during charging and discharging, especially at high rate.

[0010] The core comprises Ni a Fe b Mn 1-a-b-c M c(OH)2, wherein 0.3≤a≤0.5, for example, it can be 0.3, 0.4 or 0.5, 0.2≤b≤0.4, for example, it can be 0.2, 0.3 or 0.4, 0≤c≤0.01, for example, it can be 0, 0.005 or 0.01, the shell comprises Ni x Cu y Fe z Mn 1-x-y-z-v N v (OH)2, wherein 0.1≤x<0.3, for example, it can be 0.1, 0.2 or 0.28, 0.02≤y≤0.2, for example, it can be 0.02, 0.1 or 0.2, 0.2≤z≤0.4, for example, it can be 0.2, 0.3 or 0.4, 0≤v≤0.01, for example, it can be 0, 0.005 or 0.01, but not limited to the listed values, other values not listed in the value range are also applicable.

[0011] In one embodiment, the core is a dense structure, and the shell is a loose porous structure.

[0012] In one embodiment, the doping metal elements of M and N are different.

[0013] The present application uses different doping elements in the core and shell structure, effectively improving the comprehensive performance of the material.

[0014] In one embodiment, the M comprises any one or a combination of at least two of Zn, Mg or Sr.

[0015] In one embodiment, the N comprises any one or a combination of at least two of Ti, Al or Zr.

[0016] In one embodiment, the particle size D50 of the core is 4-6 μm, for example, it can be 4 μm, 5 μm or 6 μm, but not limited to the listed values, other values not listed in the value range are also applicable.

[0017] In one embodiment, the particle size D50 of the core-shell structure sodium battery positive electrode precursor is 8-12 μm, for example, it can be 8 μm, 10 μm or 12 μm, but not limited to the listed values, other values not listed in the value range are also applicable.

[0018] In a second aspect, the present application provides a preparation method of the core-shell structure sodium battery positive electrode precursor according to the first aspect, the preparation method comprising the following steps:

[0019] (1) passing a first mixed metal salt solution, a precipitant and a complexing agent into a bottom liquid to perform a first co-precipitation reaction;

[0020] The first mixed metal salt solution comprises a core formula amount of a Ni source, a Fe source, a Mn source, and a M source.

[0021] (2) After the first coprecipitation reaction of step (1) is completed, the first mixed metal salt solution is replaced with a second metal salt solution into the reaction system, a second coprecipitation reaction is performed, and the core-shell structure sodium battery positive electrode precursor is obtained.

[0022] The second mixed metal salt solution comprises a shell formula amount of a Ni source, a Cu source, a Fe source, a Mn source, and a N source.

[0023] In an embodiment, the bottom solution comprises pure water, a precipitant, and a complexing agent.

[0024] In an embodiment, in the reaction system of the first coprecipitation reaction of step (1), the concentration of the complexing agent is 4-8 g / L, for example, it can be 4 g / L, 6 g / L, or 8 g / L, and the pH is 10.0-11.0, for example, it can be 10.0, 10.5, or 11.0, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0025] The present application prepares a core-shell structure sodium ion battery layered oxide positive electrode material precursor by precisely controlling the reaction conditions in the coprecipitation process, and the inner core and the outer shell have different element compositions and microstructures; in particular, by controlling the concentration of the complexing agent and / or the pH of the reaction, the structure of the inner core and the outer shell is regulated.

[0026] In an embodiment, the temperature of the first coprecipitation reaction of step (1) is 40-60°C, for example, it can be 40°C, 50°C, or 60°C, the stirring speed is 300-400 r / min, for example, it can be 300 r / min, 350 r / min, or 400 r / min, and it is carried out in a protective gas.

[0027] In an embodiment, the protective gas comprises any one or a combination of at least two of nitrogen, helium, or argon, which can be nitrogen.

[0028] The precipitant of step (1) comprises a sodium hydroxide solution and / or a potassium hydroxide solution.

[0029] In an embodiment, the complexing agent of step (1) comprises any one or a combination of at least two of ammonia, citric acid, or oxalic acid.

[0030] In an embodiment, the Ni source comprises any one or a combination of at least two of nickel sulfate, nickel chloride, or nickel nitrate, which can be nickel sulfate.

[0031] In one embodiment, the Fe source comprises any one or a combination of at least two of ferrous sulfate, ferrous chloride or ferrous nitrate, and optionally ferrous sulfate.

[0032] In one embodiment, the Mn source comprises any one or a combination of at least two of manganese sulfate, manganese chloride or manganese nitrate, and optionally manganese sulfate.

[0033] In one embodiment, the M source comprises any one or a combination of at least two of a sulfate, a chloride or a nitrate, and optionally a sulfate.

[0034] In one embodiment, the N source comprises any one or a combination of at least two of a sulfate, a chloride or a nitrate, and optionally a sulfate.

[0035] In one embodiment, after the second co-precipitation reaction of step (2) is completed, the reaction is stopped, and the precursor is obtained after aging, washing and drying.

[0036] In one embodiment, in the reaction system of the second co-precipitation reaction of step (2), the concentration of the complexing agent is 2-5 g / L, for example, it can be 2 g / L, 3 g / L, 4 g / L or 5 g / L, and the pH is 9.5-10.5, for example, it can be 9.5, 10.0 or 10.5, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0037] In one embodiment, the temperature of the second co-precipitation reaction of step (2) is 40-60°C, for example, it can be 40°C, 50°C or 60°C, the stirring speed is 300-400 r / min, for example, it can be 300 r / min, 350 r / min or 400 r / min, and it is carried out in a protective gas.

[0038] As an alternative to the preparation method described in the present application, the preparation method comprises the following steps:

[0039] (1) introducing a first mixed metal salt solution, a precipitant and a complexing agent into a bottom liquid, and carrying out a first co-precipitation reaction in a protective gas at a temperature of 40-60°C and a stirring speed of 300-400 r / min;

[0040] The first mixed metal salt solution comprises a core formula amount of a Ni source, an Fe source, a Mn source and an M source;

[0041] In the reaction system of the first co-precipitation reaction, the concentration of the complexing agent is 4-8 g / L, and the pH is 10.0-11.0;

[0042] (2) after the first co-precipitation reaction of step (1) is completed, the first mixed metal salt solution is replaced by a second metal salt solution which is introduced into the reaction system, and a second co-precipitation reaction is carried out in a protective gas at a temperature of 40-60°C and a stirring speed of 300-400 r / min, to obtain the core-shell structure sodium battery positive electrode precursor;

[0043] In the reaction system of the second co-precipitation reaction, the concentration of the complexing agent is 2-5 g / L, and the pH is 9.5-10.5.

[0044] The second mixed metal salt solution comprises a shell formula amount of a Ni source, a Cu source, an Fe source, an Mn source, and an N source.

[0045] In a third aspect, the present application provides a sodium ion battery positive electrode material, which is obtained by mixing and sintering a sodium source and the core-shell structure sodium battery positive electrode precursor according to the first aspect.

[0046] In a fourth aspect, the present application provides a sodium ion battery, which comprises the sodium ion battery positive electrode material according to the third aspect.

[0047] Compared with the related art, the present application has the following beneficial effects:

[0048] The main constituent elements of the core of the present application are nickel, iron, and manganese, and the primary particles are densely packed, which is beneficial to improve the compaction density and energy density of the material; the shell adds copper elements to reduce the content of nickel elements, so as to improve the air stability of the material and reduce the overall cost of the material, and the primary particles of the shell are loosely packed, which improves the porosity and specific surface area, and is beneficial to the capacity of the material during charging and discharging, especially at high rates.

[0049] Other aspects can be apparent after reading and understanding the detailed description. DETAILED DESCRIPTION

[0050] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations on the present application.

[0051] Embodiment 1

[0052] The present embodiment provides a core-shell structure sodium battery positive electrode precursor, which comprises an inner core and a shell on the surface of the inner core, the inner core comprises Ni 0.33 Fe 0.33 Mn 0.33 Zn 0.01 (OH)2, and the shell comprises Ni 0.275 Cu 0.02 Fe 0.3 Mn0.4 Ti 0.005 (OH)2, and the shell contains pores;

[0053] The preparation method of the core-shell structure sodium battery positive electrode precursor includes the following steps:

[0054] (1) A reaction kettle is added with pure water, sodium hydroxide solution and ammonia water to prepare a reaction bottom solution, and nitrogen is introduced. After the bottom solution is qualified, a mixed salt solution I of nickel sulfate, ferrous sulfate, manganese sulfate and zinc sulfate with a molar ratio of Ni:Fe:Mn:Zn of 0.33:0.33:0.33:0.01, a sodium hydroxide solution and ammonia water are introduced into the reaction kettle in parallel to carry out a first-stage co-precipitation reaction. The reaction temperature is controlled at 40°C, the pH is 10.0, the ammonia water concentration is 4g / L, and the stirring speed is 300r / min. A zinc-doped precursor slurry with a particle size of 5μm is obtained;

[0055] (2) Stop introducing the mixed salt solution I, and introduce a mixed salt solution II of nickel sulfate, copper sulfate, ferrous sulfate, manganese sulfate and titanyl sulfate with a molar ratio of Ni:Cu:Fe:Mn:Ti of 0.275:0.02:0.3:0.4:0.005 to carry out a second-stage co-precipitation reaction. The reaction pH is controlled at 9.5, the ammonia water concentration is 2g / L, and the particle size is grown to 8μm to stop the reaction. After aging, washing and drying, a core-shell structure precursor is obtained.

[0056] Example 2

[0057] The present embodiment provides a core-shell structure sodium battery positive electrode precursor, which includes an inner core and a shell on the surface of the inner core. The inner core includes Ni 0.4 Fe 0.3 Mn 0.292 Mg 0.008 (OH)2, the shell includes Ni 0.248 Cu 0.1 Fe 0.35 Mn 0.3 Al 0.002 (OH)2, and the shell contains pores;

[0058] The preparation method of the core-shell structure sodium battery positive electrode precursor includes the following steps:

[0059] (1) into the reaction kettle pure water, sodium hydroxide solution and ammonia water preparation into the reaction liquid, and nitrogen, the bottom liquid qualified, the amount of substance ratio of Ni: Fe: Mn: Mg is 0.4: 0.3: 0.292: 0.008 of the mixed salt solution I of nickel sulfate, ferrous sulfate, manganese sulfate and magnesium sulfate, sodium hydroxide solution and ammonia water into the reaction kettle for the first stage of coprecipitation reaction, control the temperature of the reaction is 50 DEG C, pH is 10.5, ammonia water concentration is 6g / L, stirring speed is 350r / min, the particle size is 6 μm magnesium doped precursor slurry is obtained;

[0060] (2) stop the mixed salt solution I, mixed salt solution II of nickel sulfate, copper sulfate, ferrous sulfate, manganese sulfate and aluminum sulfate with the amount of substance ratio of Ni: Cu: Fe: Mn: Al is 0.248: 0.1: 0.35: 0.3: 0.002 is introduced for the second stage of coprecipitation reaction, control the pH of the reaction is 10, ammonia water concentration is 3g / L, the particle size is grown to 9 μm stop reaction, aging, washing, drying after the core-shell structure precursor is obtained.

[0061] Example 3

[0062] The present embodiment provides a core-shell structure sodium battery positive electrode precursor, the core-shell structure sodium battery positive electrode precursor includes the inner core and the surface of the inner core shell, the inner core includes Ni 0.394 Fe 0.2 Mn 0.4 Sr 0.006 (OH)2, the shell includes Ni 0.146 Cu 0.2 Fe 0.35 Mn 0.3 Zr 0.004 (OH)2, and the shell contains pores;

[0063] The preparation method of the core-shell structure sodium battery positive electrode precursor includes the following steps:

[0064] (1) into the reaction kettle pure water, sodium hydroxide solution and ammonia water preparation into the reaction liquid, and nitrogen, the bottom liquid qualified, the amount of substance ratio of Ni: Fe: Mn: Sr is 0.394: 0.2: 0.4: 0.006 of the mixed salt solution I of nickel sulfate, ferrous sulfate, manganese sulfate and strontium sulfate, sodium hydroxide solution and ammonia water into the reaction kettle for the first stage of coprecipitation reaction, control the temperature of the reaction is 60 DEG C, pH is 11.0, ammonia water concentration is 8g / L, stirring speed is 400r / min, the particle size is 4 μm strontium doped precursor slurry is obtained;

[0065] (2) stop feeding mixed salt solution I, and feed mixed salt solution II of nickel sulfate, copper sulfate, ferrous sulfate, manganese sulfate and zirconium sulfate with a molar ratio of Ni:Cu:Fe:Mn:Zr of 0.146:0.2:0.35:0.3:0.004 to perform the second-stage co-precipitation reaction, control the pH of the reaction to be 10.5, the ammonia water concentration to be 5 g / L, stop the reaction when the particle size grows to 8 μm, and obtain the core-shell structure precursor after aging, washing and drying.

[0066] Example 4

[0067] This example provides a core-shell structure sodium battery positive electrode precursor, which is the same as that in Example 1 except that the inner core comprises Ni 0.33 Fe 0.33 Mn 0.33 Ti 0.01 (OH)2.

[0068] The preparation method of the core-shell structure sodium battery positive electrode precursor is the same as that in Example 1 except for the adaptive changes.

[0069] Example 5

[0070] This example provides a core-shell structure sodium battery positive electrode precursor, which is the same as that in Example 1 except that the shell comprises Ni 0.275 Cu 0.02 Fe 0.3 Mn 0.4 Zn 0.005 (OH)2.

[0071] The preparation method of the core-shell structure sodium battery positive electrode precursor is the same as that in Example 1 except for the adaptive changes.

[0072] Example 6

[0073] This example provides a core-shell structure sodium battery positive electrode precursor, which is the same as that in Example 1 except that the inner core comprises Ni 0.33 Fe 0.33 Mn 0.34 (OH)2.

[0074] The preparation method of the core-shell structure sodium battery positive electrode precursor is the same as that in Example 1 except for the adaptive changes.

[0075] Example 7

[0076] This example provides a core-shell structure sodium battery positive electrode precursor, which is the same as that in Example 1 except that the shell comprises Ni 0.28Cu 0.02 Fe 0.3 Mn 0.4 Except for (OH)2, everything else is the same as in Example 1;

[0077] The preparation method of the core-shell structured sodium-ion cathode precursor is the same as that in Example 1, except for the adaptive changes.

[0078] Example 8

[0079] This embodiment provides a core-shell structured sodium-ion cathode precursor. Except for the pH of the reaction in step (2) of the preparation method being 9, which allows for adaptive changes in the core-shell structured sodium-ion cathode precursor, the rest of the core-shell structured sodium-ion cathode precursor is the same as in Example 1.

[0080] Example 9

[0081] This embodiment provides a core-shell structured sodium-ion cathode precursor. Except for the pH of the reaction in step (2) of the preparation method being 11.5 to adapt the core-shell structured sodium-ion cathode precursor to changes, the rest of the core-shell structured sodium-ion cathode precursor is the same as in Example 1.

[0082] Example 10

[0083] This embodiment provides a core-shell structured sodium-ion cathode precursor. Except for the pH of the reaction in step (1) of the preparation method being 9.5 to allow for adaptive changes in the core-shell structured sodium-ion cathode precursor, the rest of the core-shell structured sodium-ion cathode precursor is the same as in Example 1.

[0084] Example 11

[0085] This embodiment provides a core-shell structured sodium-ion cathode precursor. Except for the pH of the reaction in step (1) of the preparation method being 11.5 to allow for adaptive changes in the core-shell structured sodium-ion cathode precursor, the rest of the core-shell structured sodium-ion cathode precursor is the same as in Example 1.

[0086] Comparative Example 1

[0087] This comparative example provides a sodium-electric positive electrode precursor, which is the same as that in Example 1 except that it does not include a shell;

[0088] The preparation method of the sodium-ion cathode precursor is the same as that in Example 1, except that the reaction described in step (2) is not performed.

[0089] Comparative Example 2

[0090] This comparative example provides a sodium-ion battery cathode precursor, wherein the sodium-ion battery cathode precursor is Ni. 0.275 Cu0.02 Fe 0.3 Mn 0.4 Ti 0.005 (OH)2;

[0091] The method for preparing the sodium-ion cathode precursor includes the following steps:

[0092] Pure water, sodium hydroxide solution, and ammonia were added to the reactor to prepare a reaction base solution, and nitrogen gas was introduced. After the base solution was qualified, a mixed salt solution II of nickel sulfate, copper sulfate, ferrous sulfate, manganese sulfate, and titanium oxysulfate with a molar ratio of Ni:Cu:Fe:Mn:Ti of 0.275:0.02:0.3:0.4:0.005 was introduced to carry out a coprecipitation reaction. The pH of the reaction was controlled at 9.5, the ammonia concentration at 2 g / L, the temperature at 40℃, and the stirring speed at 300 r / min. The reaction was stopped when the particle size grew to 8 μm. After aging, washing, and drying, the precursor was obtained.

[0093] The precursors described in the above examples and comparative examples were used to prepare sodium-ion battery cathode materials: the precursor powder was mixed with sodium carbonate at a sodium content to transition metal molar ratio of 0.9:1, heated to 600°C at a heating rate of 5°C / min and held for 5 hours in air, then heated to 800°C at a heating rate of 3°C / min and held for 10 hours, and then naturally cooled to obtain the sodium-ion battery cathode material. The sodium-ion battery cathode materials obtained in each example were used to prepare sodium-ion batteries, wherein the negative electrode was a sodium sheet, the separator was a polyethylene separator, and the electrolyte was a sodium hexafluorophosphate electrolyte; the specific capacity, cycle capacity retention rate, and rate performance of the obtained sodium-ion batteries were tested, and the test results are shown in Table 1.

[0094] The specific capacity test method is as follows: using the Blue Battery Test System, at 25℃, the sodium-ion battery is charged and discharged three times in a voltage range of 2V to 4.1V with a charge and discharge rate of 0.04A / g (calculated based on the mass of positive electrode material), and the specific capacity of the battery is measured.

[0095] The test method for cycle capacity retention rate is as follows: under 25℃ conditions, the battery is cycled with a charge-discharge cycle of 0.19A / g (calculated based on the mass of the positive electrode material). After 100 cycles, the discharge capacity of the battery at this time is divided by the discharge capacity of the first cycle, which is the battery's 100-cycle capacity retention rate.

[0096] The test method of rate performance is as follows: under the condition of 25 DEG C, 0.04 A / g (calculated by the mass of the positive electrode material) of charge and discharge mode, three times of charge and discharge are carried out in the voltage range of 2V to 4.1V, to obtain the discharge capacity C0 of the last cycle; then, 0.04 A / g (calculated by the mass of the positive electrode material) of charge mode is used to charge the battery to 4.1V, 0.12 A / g (calculated by the mass of the positive electrode material) of discharge mode is used to discharge the battery to 2V, to obtain the discharge capacity C2 of the last cycle; the ratio of C2 / C0 is the rate performance.

[0097] Table 1

[0098] As can be seen from Table 1:

[0099] As can be seen from Example 1 and Comparative Examples 1-2, the comprehensive performance of the battery can be significantly improved by the design of the core-shell structure; as can be seen from Example 1 and Examples 4-7, the doping of specific elements in the inner core and the shell can improve the comprehensive performance of the battery; as can be seen from Example 1 and Examples 8-11, the change of pH in the first and second co-precipitation stages will affect the compactness of the inner core and the looseness of the shell, thereby affecting the performance of the battery.

[0100] In summary, the present application provides a core-shell structure sodium battery positive electrode precursor and its preparation method and application, the inner core of the core-shell structure sodium battery positive electrode precursor is once particle accumulation compact, which is beneficial to improve the compaction density and energy density of the material, the shell adds copper element, which improves the stability while reducing the cost, and the once particle of the shell is loose accumulation, which improves the porosity and specific surface area, thereby promoting the capacity of the material.

[0101] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed in the present application, which can be easily thought by those skilled in the art, falls within the protection scope and disclosure scope of the present application.

Claims

1. A core-shell structured sodium electric positive electrode precursor comprising an inner core and a shell on the surface of the inner core, the inner core comprising Ni a Fe b Mn 1-a-b-c M c (OH)2, wherein, 0.3≤a≤0.5, 0.2≤b≤0.4, and 0≤c≤0.01; the shell comprises Ni x Cu y Fe z Mn 1-x-y-z-v N v (OH)2, wherein 0.1≤x<0.3, 0.02≤y≤0.2, 0.2≤z≤0.4, and 0≤v≤0.01; M and N each independently comprise a doped metal element, and the shell contains pores.

2. The core-shell structured sodium battery cathode precursor of claim 1, wherein, The doping metal elements of M and N are different.

3. The core-shell structured sodium battery cathode precursor of claim 1 or 2, wherein, The M includes any one or a combination of at least two of Zn, Mg or Sr. Optionally, the N includes any one or a combination of at least two of Ti, Al or Zr.

4. The core-shell structured sodium battery cathode precursor of any one of claims 1-3, wherein, The particle size D50 of the inner core is 4-6 μm. Optionally, the particle size D50 of the core-shell structure sodium battery positive electrode precursor is 8-12 μm.

5. A preparation method of the core-shell structure sodium battery positive electrode precursor according to any one of claims 1-4, comprising the following steps: (1) introducing a first mixed metal salt solution, a precipitant and a complexing agent into a bottom liquid to perform a first co-precipitation reaction; The first mixed metal salt solution includes an inner core formula amount of a Ni source, a Fe source, a Mn source and a M source; (2) after the first co-precipitation reaction of step (1) is completed, a second metal salt solution is introduced into the reaction system to replace the first mixed metal salt solution to perform a second co-precipitation reaction, thereby obtaining the core-shell structure sodium battery positive electrode precursor; The second mixed metal salt solution includes an outer shell formula amount of a Ni source, a Cu source, a Fe source, a Mn source and a N source.

6. The production method according to claim 5, wherein In the reaction system of the first co-precipitation reaction of step (1), the concentration of the complexing agent is 4-8 g / L, and the pH is 10.0-11.0; Optionally, the temperature of the first co-precipitation reaction of step (1) is 40-60°C, the stirring speed is 300-400 r / min, and the reaction is performed in a protective gas.

7. The production method according to claim 5 or 6, wherein The precipitant of step (1) includes a sodium hydroxide solution and / or a potassium hydroxide solution.

8. The preparation method according to claims 5-7, wherein the complexing agent of step (1) includes any one or a combination of at least two of ammonia, citric acid or oxalic acid.

9. The method of making according to any one of claims 5-8, wherein, In the reaction system of the second co-precipitation reaction of step (2), the concentration of the complexing agent is 2-5 g / L, and the pH is 9.5-10.5; Optionally, the temperature of the second co-precipitation reaction of step (2) is 40-60°C, the stirring speed is 300-400 r / min, and the reaction is performed in a protective gas.

10. The method of making according to any one of claims 5-9, wherein, The preparation method comprises the following steps: (1) introducing a first mixed metal salt solution, a precipitant and a complexing agent into a bottom liquid to perform a first co-precipitation reaction in a protective gas at a temperature of 40-60°C and a stirring speed of 300-400 r / min; The first mixed metal salt solution includes an inner core formula amount of a Ni source, a Fe source, a Mn source and a M source; In the reaction system of the first co-precipitation reaction, the concentration of the complexing agent is 4-8 g / L, and the pH is 10.0-11.0; (2) after the first co-precipitation reaction of step (1) is completed, a second metal salt solution is introduced into the reaction system to replace the first mixed metal salt solution to perform a second co-precipitation reaction in a protective gas at a temperature of 40-60°C and a stirring speed of 300-400 r / min, thereby obtaining the core-shell structure sodium battery positive electrode precursor; In the reaction system of the second co-precipitation reaction, the concentration of the complexing agent is 2-5 g / L, and the pH is 9.5-10.5; The second mixed metal salt solution includes a shell formulation amount of a Ni source, a Cu source, a Fe source, a Mn source, and a N source. 11.A sodium-ion battery cathode material, which is obtained by mixing and sintering a sodium source and the core-shell structured sodium battery cathode precursor according to any one of claims 1-4. 12.A sodium-ion battery, which comprises the sodium-ion battery cathode material according to claim 11.

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