CN117049611A - Sodium ion positive electrode precursor material and preparation method and application thereof - Google Patents

Abstract

The invention provides a sodium ion positive electrode precursor material and its preparation method and application. The preparation method includes the following steps: adding a nickel-copper-manganese mixed salt solution, a precipitant solution and a complexing agent solution in parallel, and performing a co-precipitation reaction under a protective atmosphere to obtain the nickel-copper-manganese mixed salt solution; wherein, The precipitant solution includes a carbonate system solution, and the complexing agent solution includes a sodium citrate solution. The present invention uses a carbonate system to perform a co-precipitation reaction, combined with a special sodium citrate complexing agent, to solve the problem of copper phase separation during the co-precipitation reaction in a nickel-copper-manganese system, and at the same time improves the sphericity of the precursor material. and consistency, improving the specific capacity and cycle stability of the cathode material.

Description

A kind of sodium ion cathode precursor material and its preparation method and application

Technical field

The invention belongs to the technical field of sodium ion batteries and relates to a sodium ion positive electrode precursor material and its preparation method and application.

Background technique

Due to its high specific capacity, matching with lithium battery equipment, mature production technology, and excellent overall performance, layered transition metal oxide NaTMO ₂ has aroused great interest as a cathode material for sodium ion batteries (SIB). TM is a third-period transition metal element (Ti, V, Cr, Mn, Fe, Co, Ni and Cu) that can be oxidized and reduced. By adjusting the element composition and proportion, it shows adjustable electrochemical activity and is used for Flexibly design new electrode compounds to improve electrochemical performance and meet the specific needs of downstream application scenarios.

For example, CN107706375A discloses a method for preparing manganese-based sodium ion composite oxide cathode materials. The general composition formula of the cathode material is Na _1-x Q _x Mn _1-y M _y O2, where 0≤x≤0.4, 0≤y<0.4, and Q and M are both modified elements. The specific method is as follows: after weighing the sodium source, manganese source, and the compounds of the modifying elements Q and M according to the Na:Q:Mn:M molar ratio of 0.1~1.0:0~0.9:0.5~1.0:0~0.5, After being loaded into equipment with crushing media and dispersants for crushing and uniform mixing, crystallization synthesis is carried out in the temperature range of 500 to 900°C for 3 to 30 hours, and then the temperature is lowered to the range of 200 to 500°C and then quenched at constant temperature for 1 to 5 hours. It is then naturally cooled to room temperature, and finally mixed and crushed in a mixing and grinding equipment to obtain a manganese-based sodium ion composite oxide cathode material.

The Jahn-Teller distortion of Mn3 ⁺ is considered to be one of the most important factors in the structural evolution of O3- _NaMnO2 , which generates a strong Na-ordered phase and creates a unique new high-pressure phase with high capacity. When Mn is mixed with other transition metal elements in layered oxides with a composition exceeding ~50%, it can act as a promoter and stabilizer for the P2 phase. This P2 phase generally has better cyclability and smoother voltage distribution compared to _NaMnO2 . For some Ni-containing NaTMO _cathodes , under a certain high-pressure cutoff, the redox process is more reversible and stable than that of lithium-ion-containing cathodes. It is particularly noteworthy that the environmentally friendly and cost-effective Cu element has been introduced into layered sodium-ion battery cathode materials in recent years, and the material exhibits reversible Cu ²⁺ / ³⁺ redox and capacity, rate performance and cycle stability Enhance.

After copper is added, it is easy to cause phase separation with nickel and manganese elements, resulting in poor sphericity and consistency of the product structure, as well as poor capacity and cycle performance. For example, CN114956211A involves a manganese-nickel-copper precursor with different morphologies. According to the selected chemical composition, soluble manganese source materials, nickel source materials and copper source materials are taken as raw materials, and in the presence of reducing agent and complexing agent, add The step of reacting with a precipitating agent, the reducing agent includes at least one of acetaldehyde, phenol or hydrazine hydrate, the complexing agent includes at least one of ammonia, sodium fluoride or hydroxyethylethylenediaminetriacetic acid, so The precipitant includes an alkaline solution (sodium hydroxide and potassium hydroxide). Copper in this reaction system is easily phase separated, resulting in uneven distribution of elements.

Therefore, how to solve the phase separation problem of copper in the precursor of sodium ion cathode material in the nickel-copper-manganese system is a key issue that needs to be solved urgently.

Contents of the invention

The object of the present invention is to provide a sodium ion cathode precursor material and its preparation method and application. The present invention uses a carbonate system to perform a co-precipitation reaction, combined with a special sodium citrate complexing agent, to solve the problem of copper phase separation during the co-precipitation reaction in a nickel-copper-manganese system, and at the same time improves the sphericity of the precursor material. and consistency, improving the specific capacity and cycle stability of the cathode material.

In order to achieve the purpose of this invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a method for preparing a sodium ion cathode precursor material. The preparation method includes the following steps:

Add the nickel-copper-manganese mixed salt solution, the precipitant solution and the complexing agent solution in parallel, and perform a co-precipitation reaction under a protective atmosphere to obtain the nickel-copper-manganese mixed salt solution;

Wherein, the precipitant solution includes a carbonate system solution, and the complexing agent solution includes a sodium citrate solution.

The co-precipitation reaction provided by the present invention is carried out under a protective atmosphere (such as nitrogen atmosphere); in the present invention, the salts in the mixed salt solution include but are not limited to sulfate, nitrate or chloride salt.

The present invention uses a carbonate system to perform a co-precipitation reaction, combined with a special sodium citrate complexing agent. The precipitant and complexing agent work synergistically to solve the problem of copper phase separation during the co-precipitation reaction in a nickel-copper-manganese system. At the same time, the sphericity and consistency of the precursor material are improved, and the specific capacity and cycle stability of the cathode material are improved.

In the present invention, if the precipitant in a non-carbonate system is complexed with a sodium citrate complexing agent, uniform precipitation of Ni, Cu and Mn metal elements cannot be achieved; and if it is other precipitation systems, such as ammonia water and liquid Alkaline systems cannot solve the Cu phase separation problem;

Preferably, the total molar concentration of metal ions in the nickel-copper-manganese mixed salt solution is 0.5-2mol/L, such as 0.5mol/L, 0.75mol/L, 1mol/L, 1.25mol/L, 1.5mol/L, 1.75mol/L or 2mol/L, etc.

Preferably, the molar concentration of the precipitant solution is 0.5-2mol/L, such as 0.5mol/L, 0.75mol/L, 1mol/L, 1.25mol/L, 1.5mol/L, 1.75mol/L or 2mol/L. L et al.

Preferably, the molar concentration of the complexing agent solution is 0.25-1.5 mol/L, such as 0.25 mol/L, 0.5 mol/L, 0.75 mol/L, 1 mol/L, 1.25 mol/L or 1.5 mol/L, etc. .

Preferably, the carbonate system solution includes sodium carbonate solution and/or sodium bicarbonate solution.

Preferably, the flow rate of the nickel-copper-manganese mixed salt solution is 2 to 10L/h, such as 2L/h, 3L/h, 4L/h, 5L/h, 6L/h, 7L/h, 8L/h, 9L /h or 10L/h, etc.

Preferably, the flow rate of the precipitant solution is 2 to 8L/h, such as 2L/h, 3L/h, 4L/h, 5L/h, 6L/h, 7L/h or 8L/h, etc.

Preferably, the flow rate of the complexing agent solution is 1 to 3L/h, such as 1L/h, 1.25L/h, 1.5L/h, 1.75L/h, 2L/h, 2.25L/h, 2.5L/h. h, 2.75L/h or 3L/h, etc.

In the present invention, the flow rate of the nickel-copper-manganese mixed salt solution, the flow rate of the precipitant solution and the flow rate of the complexing agent solution work together to regulate the ion concentration of the system and inhibit the occurrence of side reactions in the system. If the flow rate of any party is not as described above, Within the range, impurities will appear.

Preferably, the pH value during the co-precipitation reaction is 7.5 to 9.5, such as 7, 7.5, 8, 8.5, 9 or 9.5, etc.

Preferably, the stirring speed of the co-precipitation reaction is 230 to 420 rpm, such as 230 rpm, 250 rpm, 280 rpm, 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm or 420 rpm, etc.

Preferably, the temperature of the co-precipitation reaction is 30-70°C, such as 30°C, 40°C, 50°C, 60°C or 70°C.

Preferably, the co-precipitation reaction time is 40 to 120 h, such as 40 h, 50 h, 60 h, 70 h, 80 h, 90 h, 100 h, 110 h or 120 h, etc.

As a preferred technical solution, the preparation method includes the following steps:

Mix a nickel-copper-manganese mixed salt solution with a total molar concentration of metal ions of 0.5 to 2 mol/L, a precipitant solution with a molar concentration of 0.5 to 2 mol/L, and a molar concentration of 0.25 to 1.5 mol. /L complexing agent solution is added in parallel flow. During the parallel adding process, the flow rate of the nickel-copper-manganese mixed salt solution is 2-10L/h; the flow rate of the precipitant solution is 2-8L/h; the flow rate of the complexing agent solution is In an environment with a pH value of 1 to 3L/h and a pH value of 7.5 to 9.5, the co-precipitation reaction is carried out for 40 to 120 hours at a stirring speed of 230 to 420 rpm and a reaction temperature of 30 to 70°C to obtain the nickel, copper and manganese mixed salt solution;

Wherein, the precipitant solution includes sodium carbonate solution and/or sodium bicarbonate solution, and the complexing agent solution includes sodium citrate solution.

In a second aspect, the present invention provides a sodium ion cathode precursor material. The sodium ion cathode precursor material is prepared by the preparation method described in the first aspect. The chemical formula of the sodium ion cathode precursor material is: Mn _{1-x- y} Ni _x Cu _y CO ₃ ; 0.1≤x≤0.4, 0<y≤0.2, for example, x can be 0.1, 0.2, 0.3 or 0.4, etc., and y can be 0.01, 0.05, 0.1 , 0.15 or 0.2 etc.

In a third aspect, the present invention provides a sodium ion cathode material, which is obtained by mixing and sintering the sodium ion cathode precursor material and a sodium source as described in the second aspect.

In a fourth aspect, the present invention also provides a sodium ion battery, which includes the sodium ion cathode material as described in the third aspect.

Compared with the existing technology, the present invention has the following beneficial effects:

The present invention uses a carbonate system to perform a co-precipitation reaction, combined with a special sodium citrate complexing agent. The precipitant and complexing agent work synergistically to solve the problem of copper phase separation during the co-precipitation reaction in a nickel-copper-manganese system. At the same time, the sphericity and consistency of the precursor material are improved, and the specific capacity and cycle stability of the cathode material are improved.

Description of the drawings

Figure 1 is an SEM image of the sodium ion cathode precursor material provided in Example 1.

Figure 2 is an SEM image of the sodium ion cathode precursor material provided in Comparative Example 2.

Detailed ways

The technical solution of the present invention will be further described below through specific implementations. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

Example 1

This embodiment provides a homogeneously precipitated sodium ion cathode precursor material with a chemical formula of Mn _0.7 Ni _0.2 Cu _0.1 CO ₃ .

The preparation method of the precursor material is as follows:

Step 1. Dissolve manganese sulfate, nickel sulfate, and copper sulfate crystals in pure water, and prepare a solution A with a total metal molar concentration of 1 mol/L according to the molar ratio Mn:Ni:Cu=0.7:0.2:0.1. Add sodium carbonate. Dissolve in pure water to prepare a sodium carbonate solution with a molar concentration of 1mol/L. Dissolve sodium citrate in pure water to prepare a 0.7mol/L sodium citrate solution;

Step 2. At the same time, add solution A, sodium carbonate solution, and sodium citrate solution into the reaction kettle through a metering pump. At the same time, introduce nitrogen with a purity of 99.9% into the reaction kettle, and stir the materials in the reaction kettle through a stirring paddle. , the stirring speed is 350rpm, the flow rate of solution A is 6L/h, the flow rate of sodium carbonate solution is 5L/h, the pH of the reaction system is controlled = 8.5, the flow rate of sodium citrate solution is 2L/h, the reaction temperature is 50°C, and the reaction is 80h;

Step 3: Heat and dry after filtering. The drying temperature is 100°C and the drying time is 12 hours to obtain the chemical formula of Mn _0.7 Ni _0.2 Cu _0.1 CO ₃ manganese nickel copper sodium ion battery cathode material precursor.

Example 2

This embodiment provides a homogeneously precipitated sodium ion cathode precursor material with a chemical formula of Mn _0.7 Ni _0.2 Cu _0.1 CO ₃ .

The preparation method of the precursor material is as follows:

Step 1. Dissolve manganese sulfate, nickel sulfate, and copper sulfate crystals in pure water, and prepare a solution A with a total metal molar concentration of 2 mol/L according to the molar ratio Mn:Ni:Cu=0.7:0.2:0.1. Add sodium carbonate. Dissolve in pure water to prepare a sodium carbonate solution with a molar concentration of 2mol/L. Dissolve sodium citrate in pure water to prepare a 1.5mol/L sodium citrate solution;

Step 2. At the same time, add solution A, sodium carbonate solution, and sodium citrate solution into the reaction kettle through a metering pump. At the same time, introduce nitrogen with a purity of 99.9% into the reaction kettle, and stir the materials in the reaction kettle through a stirring paddle. , the stirring speed is 420rpm, the flow rate of solution A is 2L/h, the flow rate of sodium carbonate solution is 2L/h, the pH of the reaction system is controlled = 9.5, the flow rate of sodium citrate solution is 1L/h, the reaction temperature is 70°C, and the reaction is 120h;

Step 3: Heat and dry after filtering. The drying temperature is 100°C and the drying time is 12 hours to obtain the chemical formula of Mn _0.7 Ni _0.2 Cu _0.1 CO ₃ manganese nickel copper sodium ion battery cathode material precursor.

Example 3

This embodiment provides a homogeneously precipitated sodium ion cathode precursor material with a chemical formula of Mn _0.7 Ni _0.2 Cu _0.1 CO ₃ .

The preparation method of the precursor material is as follows:

Step 1. Dissolve manganese sulfate, nickel sulfate, and copper sulfate crystals in pure water, and prepare a solution A with a total metal molar concentration of 0.5 mol/L according to the molar ratio Mn:Ni:Cu=0.7:0.2:0.1. Add carbonic acid Dissolve sodium in pure water to prepare a sodium carbonate solution with a molar concentration of 0.5mol/L. Dissolve sodium citrate in pure water to prepare a 0.25mol/L sodium citrate solution;

Step 2. At the same time, add solution A, sodium carbonate solution, and sodium citrate solution into the reaction kettle through a metering pump. At the same time, introduce nitrogen with a purity of 99.9% into the reaction kettle, and stir the materials in the reaction kettle through a stirring paddle. , the stirring speed is 250rpm, the flow rate of solution A is 10L/h, the flow rate of sodium carbonate solution is 8L/h, the pH of the reaction system is controlled = 7.5, the flow rate of sodium citrate solution is 3L/h, the reaction temperature is 30°C, and the reaction is 40h;

Step 3: Heat and dry after filtering. The drying temperature is 100°C and the drying time is 12 hours to obtain the chemical formula of Mn _0.7 Ni _0.2 Cu _0.1 CO ₃ manganese nickel copper sodium ion battery cathode material precursor.

Example 4

The difference between this embodiment and Embodiment 1 is that in this embodiment, the precipitant is sodium bicarbonate, and the chemical formula of the precursor material is Mn _0.65 Ni _0.15 Cu _0.2 CO ₃ .

In the preparation method, the transition metal molar ratio is adaptively adjusted.

The remaining preparation methods and parameters are consistent with Example 1.

Example 5

The difference between this embodiment and Example 1 is that the molar concentration of the sodium carbonate solution in step 1 of this embodiment is 2.5 mol/L.

The remaining preparation methods and parameters are consistent with Example 1.

Example 6

The difference between this embodiment and Example 1 is that the total molar concentration of metals in solution A in step 1 of this embodiment is 0.3 mol/L.

Example 7

The difference between this embodiment and Example 1 is that the flow rate of the sodium citrate solution in step 2 of this embodiment is 4L/h.

The remaining preparation methods and parameters are consistent with Example 1.

Example 8

The difference between this embodiment and Example 1 is that the flow rate of the sodium carbonate solution in step 2 of this embodiment is 1.0L/h.

The remaining preparation methods and parameters are consistent with Example 1.

Comparative example 1

This comparative example provides a sodium ion precursor cathode material in a hydroxide system. The preparation method is as follows:

Step 1. Dissolve manganese sulfate, nickel sulfate, and copper sulfate crystals in pure water, prepare a solution A with a total metal molar concentration of 1 mol/L according to the molar ratio Mn:Ni:Cu=0.7:0.2:0.1, and oxidize the hydrogen. Dissolve sodium in pure water to prepare a sodium hydroxide solution with a molar concentration of 1 mol/L, and prepare a 0.7 mol/L ammonia solution;

Step 2. At the same time, add solution A, sodium hydroxide solution, and ammonia solution into the reaction kettle through a metering pump. At the same time, introduce nitrogen with a purity of 99.9% into the reaction kettle, and stir the materials in the reaction kettle through a stirring paddle. The stirring speed is 350rpm, the flow rate of solution A is 6L/h, the flow rate of sodium hydroxide solution is 5L/h, the reaction system pH is controlled to be 10, the flow rate of ammonia solution is 1L/h, the reaction temperature is 50°C, and the reaction is 80h;

Step 3: Heat and dry after filtering. The drying temperature is 100°C and the drying time is 12 hours to obtain the cathode material precursor for manganese nickel copper sodium ion battery with the chemical formula of Mn _0.7 Ni _0.2 Cu _0.1 (OH) ₂ .

Comparative example 2

The difference between this comparative example and Example 1 is that the complexing agent solution in this comparative example is an ammonia solution.

The remaining preparation methods and parameters are consistent with Example 1.

The sodium ion precursor material sodium carbonate provided in Examples 1-8 and Comparative Example 1-2 was mixed and sintered at 1000°C for 12 hours. The obtained material was pulverized to obtain a sodium ion oxide cathode material.

Figure 1 shows the SEM image of the sodium ion cathode precursor material provided in Example 1, and Figure 2 shows the SEM image of the sodium ion cathode precursor material provided in Comparative Example 2. From the comparison between Figure 1 and Figure 2, it can be It can be seen that the sodium ion precursor material structure obtained by the preparation method provided by the present invention is denser and the tap density is higher, which indicates that the problem caused by copper phase separation is overcome, while the product structure in Comparative Example 2 has loose particles. , and the morphology is uneven, indicating that there is a serious copper phase separation problem.

Use the provided sodium ion cathode material as the main material, homogenize it at the ratio of 95 (main material): 2.5 (PVDF): 2.5 (SP), then lay the aluminum foil flat on the coater for coating, and place it at 120°C Dry in the blast drying oven for 3 hours; then punch, weigh, bake the pole pieces, and make CR2032 button batteries. Finally, put the batteries into the blue battery test system for electrical performance testing.

The batteries provided in Examples 1-8 and Comparative Examples 1-2 were tested for electrochemical performance. The test conditions were charge and discharge voltages of 2.0-4.0V. The first cycle was charged and discharged at 0.1C/0.1C, and then at 0.5C/1C. After 50 cycles, the cycle stability is expressed as the percentage of the discharge capacity of the 50th cycle divided by the discharge capacity of the first cycle. The test results are shown in Table 1.

Table 1

First discharge capacity (mAh/g) Cycling stability Example 1 142.8 95.34% Example 2 141.3 94.26% Example 3 140.2 94.67% Example 4 137.9 93.98% Example 5 129.4 87.65% Example 6 126.4 89.42% Example 7 130.5 89.51% Example 8 131.7 88.92% Comparative example 1 115.6 67.68% Comparative example 2 110.3 70.39%

It can be seen from the data results of Example 1 and Examples 5-8 that in the present invention, the molar concentration and flow rate of metal ions, precipitant solution and complexing agent solution in the nickel-copper-manganese mixed sulfate solution can be realized by collaboratively regulating the Ni, Uniform precipitation of Cu and Mn elements, and if either is too large or too small, side reactions will occur and inactive by-products will be generated.

It can be seen from the data results of Example 1 and Comparative Examples 1-2 that in the present invention, the precipitant and the complexing agent cooperate synergistically and are indispensable to realize the homogeneous precipitation of copper in the nickel-copper-manganese system and avoid Cu separation. Phase generation, and the combination of other systems cannot obtain a precursor product that is uniformly precipitated and has no phase separation.

In summary, the present invention uses a carbonate system to carry out a co-precipitation reaction, combined with a special sodium citrate complexing agent, the synergistic effect of the precipitating agent and the complexing agent, to solve the problem of copper in the co-precipitation reaction process under the nickel-copper-manganese system. Phase separation problem, while improving the sphericity and consistency of the precursor material, improving the specific capacity and cycle stability of the cathode material.

The applicant declares that the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the technical field should understand that any person skilled in the technical field will not use the invention disclosed in the present invention. Within the technical scope, changes or substitutions that can be easily imagined fall within the protection scope and disclosure scope of the present invention.

Claims (10)

1. A method for preparing a sodium ion positive electrode precursor material, which is characterized by comprising the following steps:

adding a nickel-copper-manganese mixed salt solution, a precipitator solution and a complexing agent solution in parallel, and carrying out coprecipitation reaction in a protective atmosphere to obtain the nickel-copper-manganese mixed salt solution;

wherein the precipitant solution comprises a carbonate system solution and the complexing agent solution comprises a sodium citrate solution.

2. The method for preparing a sodium ion positive electrode precursor material according to claim 1, wherein the total molar concentration of metal ions in the nickel-copper-manganese mixed salt solution is 0.5-2 mol/L;

preferably, the molar concentration of the precipitant solution is 0.5-2 mol/L;

preferably, the molar concentration of the complexing agent solution is 0.25-1.5 mol/L;

preferably, the carbonate system solution comprises a sodium carbonate solution and/or a sodium bicarbonate solution.

3. The method for preparing a sodium ion positive electrode precursor material according to claim 1 or 2, wherein the flow rate of the nickel-copper-manganese mixed salt solution is 2-10L/h.

4. The method for preparing a sodium ion positive electrode precursor material according to any one of claims 1 to 3, wherein the flow rate of the precipitant solution is 2 to 8L/h;

preferably, the flow rate of the complexing agent solution is 1-3L/h.

5. The method for preparing a sodium ion positive electrode precursor material according to any one of claims 1 to 4, wherein the pH value during the coprecipitation reaction is 7.5 to 9.5;

preferably, the stirring speed of the coprecipitation reaction is 230-420 rpm.

6. The method for producing a sodium ion positive electrode precursor material according to any one of claims 1 to 5, wherein the temperature of the coprecipitation reaction is 30 to 70 ℃;

preferably, the time of the coprecipitation reaction is 40 to 120 hours.

7. The method for producing a sodium ion positive electrode precursor material according to any one of claims 1 to 6, comprising the steps of:

adding nickel-copper-manganese mixed salt solution with the total molar concentration of metal ions of 0.5-2 mol/L, precipitant solution with the molar concentration of 0.5-2 mol/L and complexing agent solution with the molar concentration of 0.25-1.5 mol/L in parallel, wherein the flow rate of the nickel-copper-manganese mixed salt solution is 2-10L/h in the parallel flow adding process; the flow rate of the precipitant solution is 2-8L/h; the flow rate of the complexing agent solution is 1-3L/h, and the coprecipitation reaction is carried out for 40-120 h at the stirring speed of 230-420 rpm and the reaction temperature of 30-70 ℃ in the environment with the pH value of 7.5-9.5, so as to obtain the nickel-copper-manganese mixed salt solution;

wherein the precipitant solution comprises sodium carbonate solution and/or sodium bicarbonate solution, and the complexing agent solution comprises sodium citrate solution.

8. A sodium ion positive electrode precursor material, wherein the sodium ion positive electrode precursor material is prepared by the preparation method according to any one of claims 1 to 7, and has a chemical formula of Mn _{1-x- y} Ni _x Cu _y CO ₃ ；0.1≤x≤0.4、0＜y≤0.2。

9. A sodium ion positive electrode material, which is obtained by mixing and sintering the sodium ion positive electrode precursor material according to claim 8 and a sodium source.

10. A sodium ion battery comprising the sodium ion positive electrode material of claim 9.