A composite sodium ion positive electrode precursor and preparation method thereof

Abstract

A composite sodium ion positive electrode precursor and its preparation method, the general formula of the precursor is Na x Ni y1 Fe z1 Mn 1‑y1‑z1 (CO3) 1+x / 2+ a Ni y2 Fe z2 Mn 1‑y2‑z2 (OH)2. Preparation method: Use aqueous solution to prepare a mixed quaternary salt solution of nickel salt, iron salt and manganese salt, prepare sodium carbonate precipitant solution; prepare a mixed ternary salt solution of nickel salt, iron salt and manganese salt; prepare ammonia solution and sodium hydroxide solution; prepare carbonate-based quaternary material slurry by spraying in the first reactor, and when the slurry density in the reactor reaches 1.35~1.5g / cm 3 The ternary salt solution and sodium hydroxide solution are then introduced into the second reactor as the initial base liquid for a wet coprecipitation reaction. The ternary salt solution and sodium hydroxide solution are then introduced into the second reactor using a bottom-inlet method to prepare the precursor shell layer. The product is then centrifuged, washed, dried, and sieved to remove iron, thereby obtaining a composite sodium ion positive electrode precursor. The product of the present invention is uniform, has a controllable morphology, and reduces production costs.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and in particular to a composite sodium ion positive electrode precursor and a preparation method thereof. Background Art

[0002] With the pursuit of cost and environmental benefits, the demand for sodium-ion batteries is getting higher and higher. Layered oxides, NaNi x Fe y Mn z O2 is considered one of the most promising cathode materials due to its environmentally friendly and low-cost advantages. However, existing technologies primarily utilize solid-phase sintering to prepare ternary materials by physically mixing a ternary precursor with a sodium source (sodium carbonate or sodium hydroxide). This method suffers from shortcomings such as uneven mixing of the ternary precursor and the sodium source, high sintering temperatures, and uneven morphology.

[0003] Therefore, how to solve the above-mentioned deficiencies in the prior art has become the subject to be studied and solved by the present invention. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite sodium ion positive electrode precursor and a preparation method thereof.

[0005] In order to achieve the above objectives, the technical solutions adopted by the present invention at the product level are:

[0006] A composite sodium ion ternary cathode precursor, the general formula of which is Na x Ni y1 Fe z1 Mn 1-y1-z1 (CO3) 1+x / 2+ a Ni y2 Fe z2 Mn 1-y2-z2 (OH)2; among them, 0 <x<1、0<y1<1、0<z1<1、0<y2<1、0<z2<1、0<y1+z1<1、0<y2+z2<1、0.1≤a≤10;

[0007] The composite sodium ion cathode precursor is a core-shell structure, the core of which is a carbonate-based quaternary material with the general formula of Na x Ni y1 Fe z1 Mn 1-y1-z1 (CO3) 1+x / 2 ;

[0008] The shell is a ternary material with the general formula of Ni y2 Fe z2 Mn 1-y2-z2 (OH)2.

[0009] Further technical solutions, the D50 of the precursor is 4.5~5.5μm, the core radius occupies 40~50% of the precursor radius; the tap density of the precursor is 1.30~1.60g / m 3 , specific surface area is 15~25m 2 / g.

[0010] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention at the method level is:

[0011] A method for preparing a composite sodium ion positive electrode precursor, comprising:

[0012] Step 1: Prepare a mixed quaternary salt solution of sodium salt, nickel salt, iron salt and manganese salt with an aqueous solution, and prepare a sodium carbonate precipitant solution; prepare a mixed ternary salt solution of nickel salt, iron salt and manganese salt; prepare an ammonia solution and a sodium hydroxide solution;

[0013] Step 2: Prepare carbonate-based quaternary material slurry in the first reactor by spraying with sodium carbonate precipitant solution; the reaction temperature is 40-70°C, and after 1-2 hours of reaction, the overflow and circulation of the first reactor and the concentration device are opened. When the slurry density in the reactor reaches 1.35-1.5 g / cm 3 The reaction is stopped at this time. The slurry in the kettle is used as the core slurry, and its D50 is 1.8~2.5μm;

[0014] Step 3: The core slurry is transferred as the initial bottom liquid into the second reactor for a wet coprecipitation reaction; the ternary salt solution, the sodium hydroxide solution, and the ammonia solution are all introduced into the second reactor by a bottom-inlet method, the reaction temperature in the reactor is controlled to be 40-70°C, the pH in the reactor is controlled to be 8.6-9.55 by the sodium hydroxide solution, and the ammonia solution is used as a complexing agent; the reaction process is carried out under stirring and nitrogen or inert gas is introduced throughout the process to prepare a shell layer of the precursor, and the reaction is stopped when the slurry D50 grows to the target particle size;

[0015] Step 4: The product of step 3 is centrifuged, washed, dried, and sieved to remove iron to obtain a composite sodium ion positive electrode precursor.

[0016] In the above scheme, nitrogen or inert gas is introduced into the reaction process of step 3 to avoid oxidation of iron. Nitrogen or inert gas can also be introduced into the reaction process of step 1 to avoid oxidation of iron when preparing the ternary salt solution.

[0017] In a further technical solution, in step 1, the aqueous solution is hydroxide precursor mother liquor wastewater, and the pH is adjusted to 1 to 3 with sulfuric acid solution. If the pH is not within this range, the aging time will be prolonged and oxidation will occur.

[0018] According to a further technical solution, the mother liquor wastewater is a mixed solution containing ammonia nitrogen and sodium sulfate, with a pH of 10-13, a sodium sulfate concentration of 50-150 g / L, and an ammonia nitrogen concentration of 5-10 g / L.

[0019] According to a further technical solution, in step 1, the molar concentration of the metal ions in the quaternary salt solution is 1-2 mol / L, the molar concentration of the sodium carbonate precipitant solution is 1-4 mol / L, and the molar concentration of the metal ions in the ternary salt solution is 1-2 mol / L.

[0020] According to a further technical solution, in step 2, the spraying method is to use a pneumatic spray head to spray the sodium carbonate precipitant solution into the quaternary salt solution in the form of a spray to form the carbonate-based quaternary material slurry.

[0021] According to a further technical solution, in step 2, the inlet rate of the quaternary salt solution is 100-500 ml / min, and the ratio of the inlet flow rate of the sodium carbonate precipitant solution to the inlet flow rate of the quaternary salt solution is 1-3:1.

[0022] According to a further technical solution, in step three, the stirring speed is 550-650 rpm.

[0023] According to a further technical solution, the total reaction time of step 2 and step 3 is 10 to 34 hours.

[0024] In a further technical solution, in step four, the washing liquid is a Na2CO3 solution.

[0025] The working principle and advantages of the present invention are as follows:

[0026] The present invention provides a composite sodium ion positive electrode precursor and a method for preparing the precursor, which optimizes the mixing uniformity of the sodium component and the ternary precursor, realizes the mixing of the ternary precursor and sodium carbonate at a microscopic scale, and can form a composite ternary positive electrode precursor with uniform product and controllable morphology. From the perspective of material design to process optimization, the cost of precursor production and positive electrode material production is further reduced, and the electrochemical performance of the product is improved.

[0027] The characteristics of the present invention are:

[0028] 1. The ternary salt solution and sodium hydroxide solution of the present invention are both bottom-inlet

[0029] By symmetrically feeding the nickel-iron-manganese ternary salt solution and the sodium hydroxide solution from below, a more uniform synthesis can be achieved within the reactor under stirring at a single angle. If one is fed from above and the other from below, the solution from the upper feed will be dispersed upon entering the reactor. In the entire reaction system, some of the solution will fall into the slurry while some will fall into the aqueous solution, resulting in the formation of fine powder and uneven synthesis.

[0030] 2. The present invention adopts a spray method to prepare a carbonate-based quaternary material slurry

[0031] By atomizing the sodium carbonate precipitant solution and introducing it into the reactor, the water can be fully vaporized and evenly sprayed into the quaternary salt solution, helping to form a uniform core slurry. If it is added directly into the liquid, the precipitant may instantly combine with the quaternary salt solution, causing particle agglomeration and difficulty in dispersion, which is not conducive to the subsequent shell growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Attachment Figure 1 This is a SEM image of the core of the composite sodium ion positive electrode precursor of Example 1 of the present invention;

[0033] Attachment Figure 2 This is an SEM image of the composite sodium ion positive electrode precursor of Example 2 of the present invention;

[0034] Attachment Figure 3 This is an SEM image of the composite sodium ion positive electrode precursor of Comparative Example 1 of the present invention;

[0035] Attachment Figure 4 This is an SEM image of the composite sodium ion positive electrode precursor of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0037] The present invention will be clearly illustrated below with drawings and detailed descriptions. After understanding the embodiments of the present invention, any person skilled in the art will be able to make changes and modifications based on the techniques taught by the present invention without departing from the spirit and scope of the present invention.

[0038] The terms used herein are only for describing specific embodiments and are not intended to be limiting of the present invention. As used herein, "include," "comprising," "having," etc. are open-ended terms, meaning including but not limited to.

[0039] Unless otherwise noted, the terms used herein generally have their ordinary meanings in the art, in the context of this application, and in the specific context. Certain terms used to describe this application are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art regarding the description of this application. Example

[0040] A mixed quaternary salt solution of sodium salt, nickel salt, iron salt and manganese salt is prepared, wherein the molar ratio of sodium:nickel:iron:manganese is 1:1:1:1, and the total molar concentration of metal ions in the quaternary salt solution is 2 mol / L.

[0041] Prepare a sodium carbonate precipitant solution with a molar concentration of 4 mol / L.

[0042] The flow ratio of the quaternary salt solution to the sodium carbonate precipitant solution was controlled to be 1:1. The carbonate-based quaternary material slurry was prepared in the first reactor by the spray method (spray precipitation method). The slurry flowed into the concentration device for concentration. The slurry density reached 1.50 g / cm 3 When the slurry is gradually transferred to the wet coprecipitation reactor (second reactor) as the initial bottom liquid; a mixed ternary salt solution of nickel salt, iron salt and manganese salt is prepared, and an ammonia solution and a sodium hydroxide solution are prepared. The solution is pumped into the second reactor via a peristaltic pump. The molar ratio of nickel: iron: manganese is 1:1:1, the concentration of the ternary salt solution is 2 mol / L, the concentration of sodium hydroxide is 8 mol / L, and the ammonia solution is 2 mol / L. The ternary salt solution and the sodium hydroxide solution are both introduced into the reaction device in a bottom-inlet manner. The reaction temperature is controlled at 60°C and the pH is 8.6-9.5. The ammonia concentration of the slurry in the second reactor is 0.2 mol / L. The reaction process is carried out under stirring and nitrogen is introduced throughout the process. The reaction time is 32 hours to prepare the shell layer of the precursor.

[0043] Finally, centrifugal washing, drying, screening and iron removal steps are sequentially performed to obtain a composite sodium ion positive electrode precursor, wherein the washing water can be a saturated Na2CO3 solution.

[0044] The core of the quaternary precursor prepared in Example 1 has a particle size D50 of 2.3 μm and a spherical aggregate morphology (see Figure 1 ). Example

[0045] A mixed quaternary salt solution of sodium salt, nickel salt, iron salt and manganese salt is prepared, wherein the molar ratio of sodium:nickel:iron:manganese is 1:1:1:1, and the molar concentration of metal ions in the quaternary salt solution is 2 mol / L.

[0046] Prepare a sodium carbonate precipitant solution with a molar concentration of 4 mol / L.

[0047] The flow ratio of the quaternary salt solution to the sodium carbonate precipitant solution was controlled to be 1:3. The carbonate-based quaternary material slurry was prepared in the first reactor by the spray method (spray precipitation method). The slurry flowed into the concentration device for concentration. The slurry density reached 1.35 g / cm 3When the slurry is gradually transferred to the wet coprecipitation reactor (second reactor) as the initial bottom liquid; a mixed ternary salt solution of nickel salt, iron salt and manganese salt is prepared, and an ammonia solution and a sodium hydroxide solution are prepared. The solution is pumped into the reaction device via a peristaltic pump, wherein the molar ratio of nickel: iron: manganese is 1:1:1, the concentration of the ternary salt solution is 2 mol / L, the concentration of sodium hydroxide is 8 mol / L, and the ammonia solution is 2 mol / L. The ternary salt solution and the sodium hydroxide solution are both introduced into the reaction device from the bottom, the reaction temperature is controlled at 60°C and the pH is 8.6-9.5, the ammonia concentration of the slurry in the reactor is 0.2 mol / L, the reaction process is carried out under stirring and nitrogen is introduced throughout the process, and the reaction time is 32 hours to prepare the shell layer of the precursor.

[0048] Finally, centrifugal washing, drying, screening and iron removal steps are sequentially performed to obtain a composite sodium ion positive electrode precursor, wherein the washing water can be a saturated Na2CO3 solution.

[0049] The composite sodium ion positive electrode precursor prepared in Example 2 has a particle size D50 of 4.6 μm and a cauliflower-like particle morphology (see Figure 2 ).

[0050] Comparative Example 1:

[0051] The difference from Example 2 is that the nickel-iron-manganese mixed ternary salt solution is fed from the top and the sodium hydroxide is fed from the bottom. The rest is exactly the same as Example 2. After centrifugal washing, drying, and sieving to remove iron, a composite sodium ion positive electrode precursor is obtained. Figure 3 As shown, the precursor primary particles of Comparative Example 1 are coarse and fine and not uniform.

[0052] Table 1 is a comparison of the finished product data of the products obtained in each example.

[0053]

[0054] From the data of each Example and each Comparative Example in Table 1, it can be seen that in Comparative Example 1, the nickel-iron-manganese solution was added from the top, resulting in a decrease in the tap density of the precursor and reduced electrical performance. The sodium ion positive electrode precursor prepared by the present invention has a uniform morphology. After sintering, the precursor materials in Examples 1 and 2 have a discharge capacity of 140.2 mAh / g and 142.6 mAh / g, respectively, after 50 cycles at a current density of 0.1C.

[0055] Comparative Example 2:

[0056] The difference from Example 1 is that the precipitant sodium carbonate is directly added to the liquid, and the core slurry is not prepared by spraying. The rest is exactly the same as Example 1. Figure 4 As shown, the core morphology of Comparative Example 2 is agglomerated and the core morphology is uneven.

[0057] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A composite sodium ion cathode precursor, characterized in that: Its general formula is Na x Ni y1 Fe z1 Mn 1-y1-z1 (CO3) 1+x / 2+ a Ni y2 Fe z2 Mn 1-y2-z2 (OH)2; among them, 0 <x<1、0<y1<1、0<z1<1、0<y2<1、0<z2<1、0<y1+z1<1、0<y2+z2<1、0.1≤a≤10; The composite sodium ion cathode precursor is a core-shell structure, the core of which is a carbonate-based quaternary material with the general formula of Na x Ni y1 Fe z1 Mn 1-y1-z1 (CO3) 1+x / 2 ; The shell is a ternary material with the general formula of Ni y2 Fe z2 Mn 1-y2-z2 (OH)2.

2. The composite sodium ion cathode precursor according to claim 1, characterized in that: The D50 of the precursor is 4.5~5.5μm, and the core radius occupies 40~50% of the precursor radius; the tap density of the precursor is 1.30~1.60g / m 3 , specific surface area is 15~25m 2 / g.

3. A method for preparing a composite sodium ion positive electrode precursor, characterized in that: For preparing the composite sodium ion positive electrode precursor according to claim 1 or 2, the preparation method comprises: Step 1: Prepare a mixed quaternary salt solution of sodium salt, nickel salt, iron salt and manganese salt with an aqueous solution, and prepare a sodium carbonate precipitant solution; prepare a mixed ternary salt solution of nickel salt, iron salt and manganese salt; prepare an ammonia solution and a sodium hydroxide solution; Step 2: Prepare carbonate-based quaternary material slurry in the first reactor by spraying with sodium carbonate precipitant solution; the reaction temperature is 40-70°C, and after 1-2 hours of reaction, the overflow and circulation of the first reactor and the concentration device are opened. When the slurry density in the reactor reaches 1.35-1.5 g / cm 3 The reaction is stopped at this time. The slurry in the kettle is used as the core slurry, and its D50 is 1.8~2.5μm; Step 3: The core slurry is transferred as the initial bottom liquid into the second reactor for a wet coprecipitation reaction; the ternary salt solution, the sodium hydroxide solution, and the ammonia solution are all introduced into the second reactor by a bottom-inlet method, the reaction temperature in the reactor is controlled to be 40-70° C., and the pH in the reactor is controlled to be 8.6-9.55 by the sodium hydroxide solution; the reaction process is carried out under stirring and nitrogen or inert gas is introduced throughout the process to prepare a shell layer of the precursor, and the reaction is stopped when the slurry D50 grows to the target particle size; Step 4: The product of step 3 is centrifuged, washed, dried, and sieved to remove iron to obtain a composite sodium ion positive electrode precursor.

4. The preparation method according to claim 3, wherein: In step 1, the aqueous solution is hydroxide precursor mother liquor wastewater, and the pH is adjusted to 1-3 with sulfuric acid solution.

5. The preparation method according to claim 4, characterized in that: The mother liquor wastewater is a mixed solution containing ammonia nitrogen and sodium sulfate, with a pH of 10-13, a sodium sulfate concentration of 50-150 g / L, and an ammonia nitrogen concentration of 5-10 g / L.

6. The preparation method according to claim 3, wherein: In step 1, the molar concentration of metal ions in the quaternary salt solution is 1-2 mol / L, the molar concentration of the sodium carbonate precipitant solution is 1-4 mol / L; and the molar concentration of metal ions in the ternary salt solution is 1-2 mol / L.

7. The preparation method according to claim 3, wherein: In step 2, the spraying method is to use a pneumatic spray head to spray the sodium carbonate precipitant solution into the quaternary salt solution in the form of a spray to form the carbonate-based quaternary material slurry.

8. The preparation method according to claim 3, wherein: In step 2, the inlet rate of the quaternary salt solution is 100-500 ml / min, and the ratio of the inlet flow rate of the sodium carbonate precipitant solution to the inlet flow rate of the quaternary salt solution is 1-3:

1.

9. The preparation method according to claim 3, wherein: In step 3, the stirring speed is 550-650 rpm.

10. The preparation method according to claim 3, characterized in that: The total reaction time of step 2 and step 3 is 10 to 34 hours.

11. The preparation method according to claim 3, characterized in that: In step 4, the washing liquid is Na2CO3 solution.

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