WO2024036906A1

WO2024036906A1 - Lithium-ion battery positive electrode material and preparation method therefor

Info

Publication number: WO2024036906A1
Application number: PCT/CN2023/077442
Authority: WO
Inventors: 余海军; 谢英豪; 李爱霞; 张学梅; 李长东
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司
Priority date: 2022-08-19
Filing date: 2023-02-21
Publication date: 2024-02-22
Also published as: CN115224262A; FR3138969A1

Abstract

The present application relates to the field of battery materials, and disclosed thereby are a lithium-ion battery positive electrode material and a preparation method therefor. The preparation method comprises the following steps: (1) using water to prepare a solution A of manganese sulfate monohydrate and polyvinylpyrrolidone, adding a potassium ferricyanide solution into the solution A in a titration form, stirring, and reacting, and after the reaction is complete, aging, filtering, and washing to obtain manganese ferricyanide; and (2) using water to uniformly disperse the manganese ferricyanide, a nickel source, a lithium source, a polyimide, and an anionic surfactant, carrying out ball milling, then maintaining at 750-950° for 15-20 h, and obtaining the lithium-ion battery positive electrode material. The material has a multi-layer sheet-like structure that promotes sufficient contact with an electrolyte. The material may also effectively relieve the stress caused by the change in volume of the positive electrode material during charging and discharging processes. In addition, an iron phase in the material may be effectively stabilized in an oxide ion framework and maintain a high valence state, and the charge and discharge capacity may be improved when used in cooperation with a highly conductive nitrogen-containing carbon coating layer.

Description

Lithium-ion battery cathode material and preparation method thereof

Technical field

The present application relates to the field of battery materials, and specifically to a lithium-ion battery cathode material and a preparation method thereof.

Background technique

Lithium cobalt oxide is the earliest commercialized cathode material for lithium-ion batteries. It has high energy density and performance. However, due to the high toxicity of cobalt itself and low resource content, in order to reduce the cost of the material, nickel and manganese elements are used. Lithium cobalt oxide is doped and modified to reduce the relative content of cobalt element. At the same time, the three metal elements can have a synergistic effect, and the prepared ternary material can also produce good electrochemical performance.

As people's research gradually deepens, people begin to use iron element to completely replace the cobalt element in ternary materials. The prepared Li-Fe-Ni-Mn-O material has properties comparable to commercial ternary materials, and at the same time, the production cost is higher. Low, higher security. However, the introduction of iron element will directly cause the morphology of the ternary material to change, making it impossible to maintain a good layered structure, resulting in the inability to guarantee its electrochemical stability during use; at the same time, the iron element itself is also unstable to a certain extent. properties, impurities are prone to appear during the product preparation process, affecting product performance.

Contents of the invention

The following is an overview of the topics described in detail in this article. This summary is not intended to limit the scope of the claims.

Based on the shortcomings of the existing technology, the purpose of this application is to provide a preparation method for a lithium-ion battery cathode Li-Fe-Ni-Mn-O composite material with a layered structure. The preparation method uses ferricyanide with special morphology. Manganese oxide is used as the basic structure, and a cross-linked nitrogen-containing polymer polyimide and a specific surfactant are introduced to mix the precursors. Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe-Li-Fe from a multi-layer sheet-like structure can be obtained through a high-temperature solid-phase method. Ni-Mn-O composite material, the synthesis route of this material is simple, and the multi-layered sheet structure is conducive to electrolysis Full contact with the liquid can also effectively alleviate the stress caused by the volume change of the cathode material during the charge and discharge process; in addition, through the doping and stabilization of the nickel phase and the manganese phase, the iron phase in the material can be effectively stabilized in the oxide ion framework It maintains a higher valence state, and the nitrogen-containing coating carbon layer with high conductivity can achieve higher charge and discharge capacity.

In order to achieve the above purpose, the technical solutions adopted by this application are:

A method for preparing cathode materials for lithium-ion batteries, including the following steps:

(1) Prepare solution A with manganese sulfate monohydrate and polyvinylpyrrolidone with water. Add potassium ferricyanide solution to solution A in titration form and stir the reaction. After the reaction is complete, age, filter, and wash to obtain ferricyanide. manganese;

(2) Disperse manganese ferricyanide, nickel source, lithium source, polyimide and anionic surfactant evenly with water and perform ball milling treatment, and then maintain the temperature at 750-950°C for 15-20 hours to obtain the lithium ions Battery cathode material.

In the preparation method of the lithium-ion battery cathode material described in the present application, in addition to being an iron source and a manganese source, the manganese ferricyanide obtained by the method has a special cubic nanostructure. At the same time, the structure is hollow inside. When it is combined with When the nickel source and lithium source contact and react, the reaction diffusion degree of lithium ions can be effectively improved. When the final Li-Fe-Ni-Mn-O composite material is sintered and synthesized, the cubic hollow nanostructure collapses due to stress and gradually transforms into The multi-layer flake structure layer fragments effectively increase the area of the product when in contact with the electrolyte and alleviate the volume change stress of the material during charge and discharge; in addition, the existing iron-doped Li-Fe-Ni-Mn-O or Li-Fe -The iron phase in the Co-Ni-Mn-O material is difficult to maintain a high valence state. However, in the technical solution of this application, the iron source is introduced in the form of manganese ferricyanide, and the iron phase can be made possible through the combination of manganese and nickel in the raw material. Effectively maintained in the oxide ion framework, the charge and discharge capacity of the overall material is effectively improved.

On the other hand, in the process of synthesizing ternary materials or Li-Fe-Ni-Mn-O materials using traditional solid-phase methods, the lithium source is usually introduced into the precursor by ball milling. Although this method is simple to operate, it can easily lead to a uniform mixture. The degree is poor and causes more loss of raw materials. The existing solutions mostly involve the introduction of organic solvents and some surface Surfactants serve as dispersants to alleviate particle agglomeration, but for components dissolved in the solvent, they will be lost as the solvent evaporates or is lost, while for insoluble components, they will still gradually disappear during the ball milling process. Staying at the bottom of the reaction vessel, the improvement in dispersion is limited. Therefore, the preparation method of the product of this application uses polyimide as the intermediary. When water is used as the dispersed phase, polyimide can effectively cross-link or entrap each Li-Fe - Ni-Mn-O ternary cathode material precursor, and maintains good dispersion under the action of hydrophobic groups generated by anionic surfactants (because anionic surfactants easily generate hydrophobic groups in water, for water-soluble Polyimide can effectively cross-link precursor sources when dissolved in water. Oil-soluble polyimide can also be stably dispersed in water in the form of molecules under the action of hydrophobic groups. And enveloping each precursor source, both modes of action can effectively improve the dispersion of the precursor source during mixing). After high-temperature sintering, the polyimide is converted into a nitrogen-containing conductive carbon layer. In addition to playing a role in the material structure In addition to being protective, it can also effectively improve the conductivity of the overall material.

Optionally, the ratio of the moles of manganese sulfate monohydrate to the mass of polyvinylpyrrolidone in the solution A is (0.0025~0.0035) mol: (1~5)g, and the concentration of the solution A is 10~15g/L .

Optionally, the concentration of the potassium ferricyanide solution is 5-10 g/L.

Optionally, the molar ratio of the sum of iron elements and manganese elements in the manganese ferricyanide to the nickel element in the nickel source is n(Mn+Fe): n(Ni)=(9:1)～(8:2) .

Optionally, the molar ratio of manganese element, iron element, nickel element in the manganese ferricyanide, nickel source and lithium element in the lithium source is: n(Mn+Fe+Ni):n(Li)=1:( 1~1.05).

The Li-Fe-Ni-Mn-O composite material prepared through the above raw material ratio has a relatively high manganese element content, which can effectively improve the discharge capacity and cycle stability of the overall material.

Optionally, the nickel source is at least one of nickel acetate and nickel carbonate; the lithium source is at least one of lithium acetate and lithium carbonate.

Optionally, the anionic surfactant is a carboxylate anionic surfactant, a sulfonate anionic surfactant at least one of the sub-surfactants.

Optionally, the mass ratio of manganese ferricyanide, nickel source, lithium source, polyimide and anionic surfactant is: m (manganese ferricyanide + nickel source + lithium source): m (polyimide ): m (anionic surfactant)=1: (0.4～0.6): (0.4～0.6).

The introduction of appropriate amounts of polyimide and anionic surfactants can effectively improve the dispersion and uniformity of the raw materials during the dispersion process. At the same time, it will not cause the raw materials to be completely separated from the water system and adhere to the grinding wall.

Another object of the present application is to provide a lithium-ion battery cathode material prepared by the method for preparing a lithium-ion battery cathode material.

The lithium-ion battery cathode material Li-Fe-Ni-Mn-O composite material prepared by the method described in this application constructs an ideal multi-layered structure through special raw material selection and synthesis process, which effectively ensures that the product can deintercalate lithium ions. Stable performance in the process. At the same time, due to the introduction of iron source in the form of manganese ferricyanide and the use of N-containing polymers as auxiliary processing reagents, the iron phase in the obtained material has higher stability and the overall material purity is higher. At the same time, due to the nitrogen The introduction of elements significantly improves the conductivity of the overall material.

Another object of the present application is to provide a lithium-ion battery positive electrode sheet, which is prepared from the lithium-ion battery positive electrode material described in the present application.

The beneficial effect of this application is that it provides a method for preparing a lithium-ion battery cathode material with a layered structure. The preparation method uses manganese ferricyanide with special morphology as the basic structure and introduces cross-linked nitrogen-containing materials. By mixing polymer polyimide and specific anionic surfactants as precursors, a Li-Fe-Ni-Mn-O composite material with a multi-layered sheet structure can be effectively obtained through a high-temperature solid phase method. This material has multiple properties. The lamellar structure is conducive to full contact with the electrolyte, and can also effectively alleviate the stress caused by the volume change of the cathode material during the charge and discharge process; in addition, the iron phase in the material can be effectively stabilized in the oxide ion framework and maintained The higher valence state, combined with the high conductivity nitrogen-containing carbon layer, can increase the charge and discharge capacity. higher.

Other aspects will become apparent after reading and understanding the detailed description.

Detailed ways

In order to better explain the purpose, technical solutions and advantages of the present application, the present application will be further described below in conjunction with specific embodiments and comparative examples. The purpose is to understand the content of the present application in detail, but not to limit the present application. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of this application. The experimental reagents, raw materials and instruments designed for the implementation and comparative examples of this application are all commonly used common reagents, raw materials and instruments unless otherwise specified.

Example 1

An embodiment of the lithium-ion battery cathode material and its preparation method described in the present application includes the following steps:

(1) Prepare solution A with a concentration of 12g/L by adding 0.003mol manganese sulfate monohydrate and 3g polyvinylpyrrolidone with water and a small amount of ethanol. Add 12g/L potassium ferricyanide solution to solution A in titration form and stir the reaction until the solution The turbidity will no longer change. After the reaction is complete, it is aged at room temperature for 24 hours, filtered, washed with water and ethanol respectively, and dried to obtain manganese ferricyanide;

(2) Place manganese ferricyanide, nickel acetate, lithium acetate, polyimide and anionic surfactant dodecyl glycidyl ether DEG (Senfida Chemical) in a ball mill tank, and add 5 times the mass of water Disperse evenly and use a planetary ball mill to ball mill at a rate of 200 rpm for 24 hours. The resulting mixed slurry is dried at room temperature for 24 hours and then placed in an air atmosphere and kept at 850°C for 18 hours to obtain the lithium ion battery cathode material; wherein each mixture According to the theoretical reaction product formula of the metal elements in the material, Li(Mn _0.48 Fe _0.32 Ni _0.2 )O _2, the ratio of each element is calculated as n(Mn+Fe+Ni): n(Li)=1:1, n(Mn+Fe ): n (Ni) = 8:2; the mass ratio of manganese ferricyanide, nickel source, lithium source, polyimide and anionic surfactant is: m (manganese ferricyanide + nickel source + lithium source) :m (polyimide): m (anionic surfactant) = 1g: 0.5g: 0.5g.

Example 2

The only difference between this embodiment and Example 1 is that the ratio of each element in each mixture is calculated as n(Mn+Fe+Ni) based on the theoretical reaction product formula Li(Mn _0.51 Fe _0.34 Ni _0.15 )O ₂ : n(Li)=1:1, n(Mn+Fe):n(Ni)=8.5:1.5.

Example 3

The only difference between this embodiment and Example 1 is that the ratio of each element of the metal elements in each mixture is n(Mn+Fe+Ni) _calculated based on the theoretical reaction product formula Li(Mn _0.54 Fe _0.36 Ni _0.1 )O 2: n(Li)=1:1, n(Mn+Fe): n(Ni)=9:1.

Example 4

The only difference between this embodiment and Example 1 is that the ratio of each element in each mixture is calculated as n(Mn+Fe+Ni) based on the theoretical reaction product formula Li(Mn _0.57 Fe _0.38 Ni _0.05 )O ₂ : n(Li)=1:1, n(Mn+Fe):n(Ni)=9.5:0.5.

Example 5

The only difference between this embodiment and Example 1 is that the mass ratio of manganese ferricyanide, nickel source, lithium source, polyimide and anionic surfactant is: m (manganese ferricyanide + nickel source + lithium source ): m (polyimide): m (anionic surfactant) = 1g: 0.6g: 0.6g.

Example 6

The only difference between this embodiment and Example 1 is that the mass ratio of manganese ferricyanide, nickel source, lithium source, polyimide and anionic surfactant is: m (manganese ferricyanide + nickel source + lithium source ): m (polyimide): m (anionic surfactant) = 1g: 0.8g: 0.8g.

Comparative example 1

A lithium-ion battery cathode material and a preparation method thereof, including the following steps:

Combine iron acetate, manganese acetate, nickel acetate, lithium acetate, polyimide and anionic surfactants. Place the dialkyl glyceryl ether in a ball milling tank, add 5 times the mass of water to disperse evenly, and use a planetary ball mill to conduct ball milling at a rate of 200 rpm for 24 hours. The resulting mixed slurry is dried at room temperature for 24 hours and then placed in an air atmosphere and heated at 850°C. The lithium-ion battery cathode material is obtained by keeping it incubated for 18 hours; wherein the ratio of each element of the metal elements in each mixture is calculated based on the theoretical reaction product formula Li(Mn _0.48 Fe _0.32 Ni _0.2 )O ₂ as n(Mn+Fe+ Ni): n(Li)=1:1, n(Mn+Fe): n(Ni)=8:2; iron source, manganese source, nickel source, lithium source, polyimide and anionic surfactant The mass ratio is: m (iron source + manganese source + nickel source + lithium source): m (polyimide): m (anionic surfactant) = 1g: 0.5g: 0.5g.

Comparative example 2

(2) Place manganese ferricyanide, nickel acetate, lithium acetate, and polyimide in a ball mill tank, add 5 times the mass of water to disperse evenly, and use a planetary ball mill to conduct ball milling at a rate of 200 rpm for 24 hours. The resulting mixture The slurry is dried at room temperature for 24 hours and then placed in an air atmosphere and kept at 850°C for 18 hours to obtain the lithium ion battery cathode material; the theoretical reaction product formula of the metal elements in each mixture is Li(Mn _0.48 Fe _0.32 Ni _0.2 )O ₂ calculates the ratio of each element as n(Mn+Fe+Ni): n(Li)=1:1, n(Mn+Fe): n(Ni)=8:2; manganese ferricyanide, nickel source, The mass ratio of lithium source and polyimide is: m (manganese ferricyanide + nickel source + lithium source): m (polyimide) = 1g: 0.5g.

Comparative example 3

(1) Prepare a concentrated mixture of 0.003 mol manganese sulfate monohydrate and 3 g polyvinylpyrrolidone with water and a small amount of ethanol. For solution A with a concentration of 12g/L, add 12g/L potassium ferricyanide solution to solution A in titration form and stir the reaction until the turbidity of the solution no longer changes. After the reaction is complete, age it at room temperature for 24 hours, filter, and mix with water and After washing separately with ethanol and drying, manganese ferricyanide is obtained;

(2) Place manganese ferricyanide, nickel acetate, lithium acetate, and anionic surfactant dodecyl glycidyl ether in a ball mill jar, add 5 times the mass of water to disperse evenly, and use a planetary ball mill at a rate of 200 rpm Perform ball milling treatment for 24 hours, dry the resulting mixed slurry at room temperature for 24 hours, then place it in an air atmosphere and keep it at 850°C for 18 hours to obtain the lithium-ion battery cathode material; wherein the theoretical reaction product formula of the metal elements in each mixture is Li (Mn _0.48 Fe _0.32 Ni _0.2 )O ₂ The calculated ratio of each element is n(Mn+Fe+Ni): n(Li)=1:1, n(Mn+Fe): n(Ni)=8:2; iron The mass ratio of manganese cyanide, nickel source, lithium source and anionic surfactant is: m (manganese ferricyanide + nickel source + lithium source): m (anionic surfactant) = 1g: 0.5g.

Comparative example 4

(2) Place manganese ferricyanide, nickel acetate, lithium acetate, polyimide and nonionic surfactant AEO-9 (Daixu Chemical) in a ball mill tank, add 5 times the mass of water to disperse evenly and use a planetary The ball mill was ball milled at a speed of 200 rpm for 24 hours, and the resulting mixed slurry was dried at room temperature for 24 hours and then placed in an air atmosphere and kept at 850°C for 18 hours to obtain the lithium-ion battery cathode material; wherein the metal elements in each mixture were According to the theoretical reaction product formula Li(Mn _0.48 Fe _0.32 Ni _0.2 )O ₂ , the ratio of each element is calculated as n (Mn+Fe+Ni): n(Li)=1:1, n(Mn+Fe): n(Ni)=8:2; manganese ferricyanide, nickel source, lithium source, polyimide and non- The mass ratio of ionic surfactants is: m (manganese ferricyanide + nickel source + lithium source): m (polyimide): m (nonionic surfactant) = 1g: 0.5g: 0.5g.

Effect example 1

In order to verify the electrochemical performance of the lithium-ion battery cathode materials described in this application, the materials of each example and comparative example were mixed with conductive carbon black and PVDF according to a mass ratio of 8:1:1, and an appropriate amount of NMP was added to adjust the slurry, and then coated The positive electrode piece was prepared by cutting it after drying on the aluminum foil. Lithium metal was used as the negative electrode piece and commercial polypropylene film was used as the separator to assemble the lithium ion button half battery. After the resulting battery was left to stand for 12 hours, it was heated for 2 to 2 hours at room temperature. 100 charge-discharge cycle tests were conducted under the condition of 4.5V voltage and 0.2C rate, then the rate was increased to 1C for 5 cycles, and finally returned to 0.2C for 5 cycles. The results are shown in Table 1.

Table 1

It can be seen from Table 1 that the initial discharge specific capacity of the products obtained in each embodiment is relatively high at low rates, reaching more than 155mAh/g, and the capacity retention rate after 100 cycles also reaches more than 80%. When the product undergoes high-rate cycles and returns to low-rate cycles, its discharge specific capacity is still considerable, reaching a maximum of 145mAh/g. It can be seen from Examples 1 to 4 that as the nickel content in the product decreases, its cycle stability improves to a certain extent, but the discharge capacity decreases. Based on comprehensive performance considerations, n(Mn+Fe) in the product: n(Ni ) is 9:1 to 8:2, the performance is better. From the comparison of the product performance of Example 1, Example 5 and Example 6, it can be seen that as the addition amount of polyimide and surfactant increases too much, the dispersion of each precursor of the product is better, and the nitrogen doping content It also becomes higher, but relatively speaking, it may cause each precursor to be completely separated from the water phase during the mixing process, and the degree of uniform mixing will become lower, and the cycle performance and rate performance of the product will also be affected. In contrast, the product of Comparative Example 1 uses ordinary raw materials to prepare the product. Although surfactant and polyimide are finally introduced, the overall effect is poor, the product has poor cycle performance, low initial capacity and The rate performance is poor. Comparative Examples 2 and 3 did not introduce surfactant and polyimide respectively during the grinding and mixing process of the precursor. Compared with the product of Example 1, its cycle performance and rate performance were significantly worse, while the initial discharge of the product of Comparative Example 3 was The specific capacity is low, indicating that the lack of nitrogen doping will also have an impact on the initial capacity of the product. The difference between the product of Comparative Example 4 and that of Example 1 during the preparation process is only the use of different types of surfactants. Obviously, its performance is equivalent to that of the product of Comparative Example 2 without the introduction of surfactants, indicating that nonionic surfactants are not effective. Helps the precursor materials to be mixed and dispersed evenly. This additive is not suitable for the preparation process system of the product described in this application.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and do not limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that The technical solution of this application can be modified or equivalently replaced, and without departing from the essence and scope of the technical solution of this application.

Claims

A method for preparing cathode materials for lithium-ion batteries, which includes the following steps:

(1) Prepare solution A with manganese sulfate monohydrate and polyvinylpyrrolidone with water. Add potassium ferricyanide solution to solution A in titration form and stir the reaction. After the reaction is complete, age, filter, and wash to obtain ferricyanide. manganese;

(2) Disperse manganese ferricyanide, nickel source, lithium source, polyimide and anionic surfactant evenly with water and perform ball milling treatment, and then maintain the temperature at 750-950°C for 15-20 hours to obtain the lithium ions Battery cathode material.
The preparation method of lithium ion battery cathode material according to claim 1, wherein the ratio of the moles of manganese sulfate monohydrate to the mass of polyvinylpyrrolidone in the solution A is (0.0025~0.0035) mol: (1~5) g , the concentration of solution A is 10-15g/L.
The method for preparing a lithium-ion battery cathode material according to claim 1, wherein the concentration of the potassium ferricyanide solution is 5-10 g/L.
The preparation method of lithium ion battery cathode material according to claim 1, wherein the molar ratio of the sum of iron element and manganese element in the manganese ferricyanide to the nickel element in the nickel source is n(Mn+Fe):n(Ni )=(9:1)～(8:2).
The preparation method of lithium ion battery cathode material according to claim 1, wherein the molar ratio of manganese element, iron element, nickel element in the manganese ferricyanide, nickel source and lithium element in the lithium source is: n(Mn+ Fe+Ni):n(Li)=1:(1～1.05).
The method for preparing positive electrode materials for lithium ion batteries according to claim 1, wherein the nickel source is at least one of nickel acetate and nickel carbonate; and the lithium source is at least one of lithium acetate and lithium carbonate.
The method for preparing positive electrode materials for lithium ion batteries according to claim 1, wherein the anionic surfactant is at least one of a carboxylate anionic surfactant and a sulfonate anionic surfactant.
The preparation method of lithium ion battery cathode material according to claim 1, wherein the mass ratio of manganese ferricyanide, nickel source, lithium source, polyimide and anionic surfactant is: m (manganese ferricyanide + Nickel source + lithium source): m (polyimide): m (anionic surfactant) = 1: (0.4～0.6): (0.4～0.6).
The lithium ion battery cathode material is prepared by the method for preparing a lithium ion battery cathode material according to any one of claims 1 to 8.
A lithium-ion battery positive electrode piece, wherein the positive electrode piece is prepared from the lithium-ion battery positive electrode material of claim 9.