Composite electrode material, preparation method thereof and secondary battery

Abstract

The invention provides a composite electrode material, a preparation method thereof and a secondary battery. The composite electrode material comprises the following raw materials in parts by weight: 30-50 parts of transition metal salt, 25-45 parts of urea, 20-30 parts of biomass carbon and 5-20 parts of inorganic filler, wherein the core of the composite electrode material is a hydrotalcite material with a layered structure, and the shell layer is a carbon layer with a microporous structure. According to the composite electrode material, transition metal is used as an active site, the theoretical specific capacity of the composite electrode material is improved, the contact area between the composite electrode material and an electrolyte is increased by using the layered structure of the hydrotalcite-based material and the porous structure of the carbon layer, and meanwhile, a conductive network of the carbon layer also promotes rapid transfer of metal ions, so that the specific capacity of the composite electrode material is improved. Furthermore, excellent electrochemical performance is realized; and by introducing the inorganic filler, the inorganic filler can be distributed in the composite electrode material to further improve the structural stability of the composite electrode material, so that the capacity stability of the composite electrode material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, in particular to a composite electrode material, a preparation method thereof and a secondary battery. BACKGROUND

[0002] With the progress of science and technology and the acceleration of industrialization process, secondary batteries have been widely used in the fields of intelligent electronic products, electric vehicles and energy storage containers. However, the electrochemical performance of the electrode material of the commercial secondary battery negative electrode cannot meet the development needs of power batteries. Therefore, it is of great significance to develop a new type of electrode material for negative electrode with high specific capacity, rate performance and cycle stability, which can promote the development of high-performance secondary batteries.

[0003] In recent years, people have modified the electrode material of the secondary battery, aiming to improve the electrochemical performance of the material. For example, some researchers have obtained a composite electrode material by modifying graphene oxide and carbon nanotubes, which has excellent electrical conductivity. However, the double carbon modification leads to a too fast capacity decay rate of the electrode material, and the limited theoretical specific capacity of the carbon material cannot meet the market demand well. Therefore, it is of great significance to develop a low-cost and high-capacity composite electrode material to promote the development of secondary batteries. SUMMARY

[0004] The main purpose of the present application is to provide a composite electrode material, a preparation method thereof and a secondary battery, so as to solve the problems of too fast capacity decay rate and limited specific capacity of the electrode material modified by double carbon, which cannot meet the market demand well.

[0005] In order to achieve the above purpose, according to one aspect of the present application, a composite electrode material is provided. The raw materials of the composite electrode material include, in terms of weight fraction, 30-50 parts of transition metal salt, 25-45 parts of urea, 20-30 parts of biomass carbon and 5-20 parts of inorganic filler. The composite electrode material has a core-shell structure, the inner core is a hydrotalcite material with a layered structure, and the shell layer is a carbon layer with a microporous structure.

[0006] Further, the transition metal salt includes at least two of nickel nitrate, cobalt nitrate, aluminum nitrate or copper nitrate.

[0007] Further, the transition metal salt is a mixture of nickel nitrate and aluminum nitrate, and the molar ratio of the two is (1-4):1.

[0008] Further, the biomass carbon includes at least one of straw, sawdust or cellulose.

[0009] Further, the inorganic filler includes at least one of aluminum oxide, silicon dioxide and titanium dioxide.

[0010] Furthermore, the particle size of the inorganic filler is D50 of 2-6 μm.

[0011] To achieve the above objectives, according to another aspect of this application, a method for preparing the aforementioned composite electrode material is provided. The method includes: step S1, mixing a transition metal salt, urea, biomass carbon, and inorganic filler in water to carry out a hydrothermal reaction to obtain a composite electrode precursor material; and step S2, calcining the composite electrode precursor material to obtain the composite electrode material.

[0012] Further, in step S1, the hydrothermal reaction temperature is 120-180℃, and the hydrothermal reaction time is 9-12h.

[0013] Further, in step S2, the calcination temperature is 400-800℃, and the calcination time is 1-5h.

[0014] Further, in step S2, the calcination process is carried out under the protection of a protective gas, which includes at least one of nitrogen, argon, or helium.

[0015] Further, step S1 includes: adding transition metal salt, urea, biomass carbon and inorganic filler into water to carry out a hydrothermal reaction to obtain a hydrothermal product, and washing and drying the hydrothermal product in sequence to obtain a composite electrode precursor material.

[0016] Furthermore, deionized water or purified water is used for washing.

[0017] Furthermore, the drying temperature is 75-85℃, and the drying time is 10-15 hours.

[0018] According to a third aspect of this application, a secondary battery is provided, comprising the composite electrode material provided in the first aspect or the composite electrode material obtained by the preparation method provided in the second aspect above.

[0019] Applying the technical solution of this application, a core-shell structured composite electrode material is prepared using transition metal salts, urea biomass, biomass carbon, and inorganic fillers as raw materials. The core is a layered hydrotalcite material, and the shell is a microporous carbon layer. The composite electrode material provided by this application not only utilizes transition metals as active sites, improving the theoretical specific capacity of the composite electrode material, but also increases the contact area between the composite electrode material and the electrolyte by utilizing the layered structure of the hydrotalcite-based material and the porous structure of the carbon layer. Simultaneously, the conductive network of the carbon layer promotes the rapid transfer of metal ions, thereby achieving excellent electrochemical performance. Furthermore, by introducing inorganic fillers, the inorganic fillers can be distributed throughout the composite electrode material to further improve its structural stability, thereby enhancing its capacity stability. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 A scanning electron microscope image of the composite electrode material provided in Example 2 is shown;

[0022] Figure 2 The diagram shows the charge-discharge cycle performance test results of the secondary battery prepared from the composite electrode material provided in Example 2. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0024] As described in the background section of this application, the electrochemical performance of commercial lithium-ion battery anode materials can no longer meet the development needs of power batteries. Although dual carbon modification can improve conductivity, the capacity decay rate is too fast and the specific capacity is limited, which cannot adequately meet market demands. To solve this problem, this application provides a composite electrode material, its preparation method, and a secondary battery.

[0025] In one typical embodiment of this application, a composite electrode material is provided. By weight, the raw materials of the composite electrode material include: 30-50 parts of transition metal salt, 25-45 parts of urea, 20-30 parts of biomass carbon, and 5-20 parts of inorganic filler. The composite electrode material has a core-shell structure, with the core being a layered hydrotalcite material and the shell being a carbon layer with a microporous structure.

[0026] The composite electrode material provided in this application uses a layered hydrotalcite-based material as the core and a microporous carbon layer as the shell. It not only utilizes transition metals as active sites to improve the theoretical surface capacity of the composite electrode material, but also increases the contact area between the composite electrode material and the electrolyte by utilizing the layered structure of the hydrotalcite-based material and the porous structure of the carbon layer. At the same time, the conductive network of the carbon layer promotes the rapid transfer of lithium ions, thereby achieving excellent electrochemical performance. Furthermore, by introducing inorganic fillers, the inorganic fillers can be distributed in the composite electrode material to further improve its structural stability, thereby improving its capacity stability.

[0027] This application utilizes transition metal salts as raw materials, which facilitates the complexation reaction between transition metal ions and urea. Under heating conditions, urea decomposes to form an alkaline system, and the transition metal ions precipitate to form a layered, hydrotalcite-like precipitate. Using biomass carbon as raw material further facilitates the formation of a microporous carbon layer through calcination, thereby increasing its contact area with the electrolyte and improving metal ion transport efficiency. The introduction of inorganic fillers further enhances the structural stability of the composite electrode material, thereby improving its capacity stability.

[0028] In the composite electrode material provided in this application, the raw materials, by weight, include transition metal salts in the range of 30, 35, 40, 45, 50 parts or any two of these values; urea in the range of 25, 30, 35, 40, 45 parts or any two of these values; biomass carbon in the range of 20, 22, 25, 28, 30 parts or any two of these values; and inorganic fillers in the range of 5, 8, 10, 12, 15, 18, 20 parts or any two of these values.

[0029] The aforementioned transition metal salt is preferably a soluble transition metal salt, which facilitates the formation of an alkaline system with urea in aqueous solution, thereby improving the efficiency of the complexation reaction. The aforementioned transition metal salt may be any two or more of nickel nitrate, cobalt nitrate, aluminum nitrate, or copper nitrate, which facilitates the formation of two or more metal active centers, further improving the specific capacity of the composite electrode material.

[0030] In some specific embodiments of this application, the transition metal salt is a mixture of nickel nitrate and aluminum nitrate, and the molar ratio of the two is 1:1 to 4:1, in order to further improve the specific capacity of the composite electrode material. Specifically, in the transition metal salt, the molar ratio of nickel nitrate and aluminum nitrate is 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or any range of two values.

[0031] The biomass carbon mentioned above is the biomass carbon commonly used in this field, including but not limited to any one or more of straw, sawdust, or cellulose.

[0032] The aforementioned inorganic fillers are commonly used inorganic fillers in this field, including but not limited to any one or more of alumina, silicon dioxide, and titanium dioxide.

[0033] In a second typical embodiment of this application, a method for preparing a composite electrode material is also provided. The method includes: step S1, mixing a transition metal salt, urea, biomass carbon and inorganic filler in water to carry out a hydrothermal reaction to obtain a composite electrode precursor material; and step S2, calcining the hydrotalcite precursor material to obtain the composite electrode material.

[0034] The method for preparing the composite electrode material provided in this application involves first mixing transition metal salts with urea and inorganic fillers in water to carry out a complexation reaction. Under heating conditions, urea decomposes to form an alkaline system, and transition metal ions precipitate to form a layered hydrotalcite-like precipitate. This precipitate is then combined with biomass carbon to form a composite electrode precursor material with a hydrotalcite structure. Subsequently, calcination is performed to allow the transition metals in the hydrotalcite-like precipitate to form transition metal oxides. At the same time, hydrogen and oxygen elements in the biomass carbon are removed to form a carbon layer with a microporous structure that coats the surface of the hydrotalcite-based material, thereby obtaining a composite electrode material with a core-shell structure.

[0035] The composite electrode material provided in this application can be prepared by hydrothermal reaction and calcination. The process is simple, easy to operate, and can be mass-produced, which is conducive to reducing the preparation cost.

[0036] To promote uniform dispersion of inorganic fillers in electrode composite materials, the preferred particle size D50 of the inorganic fillers is 2-6 μm. Specifically, the particle size of the inorganic fillers can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or any combination of two values.

[0037] In some embodiments of this application, in step S1 above, the temperature of the hydrothermal reaction is 120-180°C, and the reaction time is 9-12 hours. Specifically, the temperature of the hydrothermal reaction can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or any range of two values; the reaction time can be 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, or any range of two values.

[0038] In some embodiments of this application, step S1 includes: first, adding transition metal salts, urea, biomass carbon, and inorganic fillers to water for a hydrothermal reaction to obtain a hydrothermal product; then, sequentially washing and drying the hydrothermal product to obtain a composite electrode precursor material. Specifically, the transition metal salts, urea, and inorganic fillers are dispersed and dissolved in water for a complexation reaction. Under heating conditions, urea decomposes to form an alkaline system, and transition metal ions precipitate to form a layered hydrotalcite-like precipitate (transition metal hydroxide). Then, biomass carbon and the hydrotalcite-like precipitate are combined to form a hydrothermal product with a core-shell structure.

[0039] In some embodiments of this application, in order to reduce impurities in the composite electrode material, step S2 includes: first washing and drying the composite electrode precursor material with water in sequence, and then calcining it.

[0040] The water used for the above washing is selected from deionized water or purified water, etc.

[0041] To further save energy, the preferred drying temperature is 75-85℃, and the drying time is 10-15 hours. Specifically, the drying temperature can be 75℃, 78℃, 80℃, 82℃, 85℃, or any combination of two values; the drying time can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or any combination of two values.

[0042] In some embodiments of this application, in step S2 above, the calcination temperature is 400-800℃, and the calcination time is 1-5h, to further improve the efficiency of the calcination process while saving energy. Specifically, the calcination temperature can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, or any range of two values, and the calcination time can be 1h, 1.5h, 2.0h, 2.5h, 3h, 4h, 5h, or any range of two values.

[0043] In order to avoid introducing impurities during the calcination process that could affect the performance of the composite electrode material, in some embodiments of this application, the calcination process is preferably carried out under the protection of a protective gas, which includes any one or more of nitrogen, argon or helium.

[0044] In a third typical embodiment of this application, a secondary battery is also provided, which includes the composite electrode material provided in the first aspect or the composite electrode material obtained by the preparation method provided in the second aspect.

[0045] In some embodiments of this application, the secondary battery is a lithium-ion battery or a sodium-ion battery.

[0046] The secondary battery provided in this application, by using the aforementioned composite electrode material as the negative electrode material, not only significantly improves the specific capacity but also exhibits superior cycle stability, thus better meeting market demands.

[0047] The superior effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0048] Example 1

[0049] This embodiment provides a composite electrode material comprising the following raw materials: 2.5g nickel nitrate, 1.6g aluminum nitrate, 3.6g urea, 2.0g straw powder, and 1.0g silicon dioxide.

[0050] The above-mentioned composite battery material was prepared according to the following steps:

[0051] (1) 2.5g nickel nitrate, 1.6g aluminum nitrate, 3.6g urea, 1.0g silicon dioxide (particle size D50 is 3μm) and 2.0g straw powder (average size is 0.2mm×1mm) were added to 50mL of water and heated at 150℃ for 9h to obtain composite electrode precursor material.

[0052] (2) The composite electrode precursor material was washed with deionized water 5 times, dried at 80°C for 15 h, and then calcined at 600°C for 5 h under nitrogen atmosphere to obtain the composite electrode material.

[0053] Example 2

[0054] The difference between this embodiment and Embodiment 1 is that the amount of straw powder used is 2.5g.

[0055] Example 3

[0056] The difference between this embodiment and Embodiment 2 is that the raw materials of the composite electrode material include: 1.8g nickel nitrate, 1.2g aluminum nitrate, 2.5g urea, 3g straw powder and 2.0g silicon dioxide.

[0057] Example 4

[0058] The difference between this embodiment and Embodiment 2 is that the raw materials of the composite electrode material include: 3.0g nickel nitrate, 2.0g aluminum nitrate, 4.5g urea, 2g straw powder and 0.5g silicon dioxide.

[0059] Example 5

[0060] The difference between this embodiment and Embodiment 2 is that silicon dioxide is replaced with titanium dioxide, and the D50 of titanium dioxide is 3μm.

[0061] Example 6

[0062] The difference between this embodiment and Embodiment 2 is that cobalt nitrate is used instead of aluminum nitrate.

[0063] Example 7

[0064] The difference between this embodiment and Embodiment 2 is that copper nitrate is used instead of aluminum nitrate.

[0065] Example 8

[0066] The difference between this embodiment and Embodiment 2 is that the amounts of nickel nitrate and aluminum nitrate are adjusted so that the total mass of the two is 4.1g and the molar ratio of the two is 1:1.

[0067] Example 9

[0068] The difference between this embodiment and Embodiment 2 is that the amounts of nickel nitrate and aluminum nitrate are adjusted so that the total mass of the two is 4.1g and the molar ratio of the two is 4:1.

[0069] Example 10

[0070] The difference between this embodiment and Embodiment 2 is that the amounts of nickel nitrate and aluminum nitrate are adjusted so that the total mass of the two is 4.1g and the molar ratio of the two is 1:2.

[0071] Example 11

[0072] The difference between this embodiment and Embodiment 2 is that the amounts of nickel nitrate and aluminum nitrate are adjusted so that the total mass of both is 4.1g and the molar ratio of the two is 5:1.

[0073] Example 12

[0074] The difference between Comparative Example 1 and Example 2 is that the amount of nickel nitrate was adjusted to 4.1g, and aluminum nitrate was not added.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 2 is that no transition metal salts were added to the raw materials.

[0077] Comparative Example 2

[0078] The difference between this comparative example and Example 2 is that no biomass carbon was added to the raw materials.

[0079] Comparative Example 3

[0080] The difference between this comparative example and Example 2 is that asphalt is used to replace biomass carbon, and the molar amount of carbon in the asphalt is the same as the molar amount of carbon in the biomass.

[0081] Comparative Example 4

[0082] The difference between this comparative example and Example 2 is that silicon dioxide was not added to the raw materials.

[0083] Experimental Example 1

[0084] The composite electrode material provided in Example 2 above was subjected to scanning electron microscopy testing, and the results are as follows: Figure 1 As shown, from Figure 1 As can be seen, the composite electrode material provided in Example 2 has a distinct layered structure, which significantly increases the specific surface area of ​​the composite electrode material, promotes the contact between the electrode and the electrolyte, and accelerates the transport of metal ions.

[0085] Experimental Example 2

[0086] The composite electrode materials provided in the above embodiments and comparative examples were used to prepare secondary batteries. The electrochemical performance of the above secondary batteries was tested, and the results are shown in Table 1 below.

[0087] Among them, (1) the composition of the secondary battery is as follows: the composite electrode material and the binder (carboxymethyl cellulose) are mixed in a mass ratio of 9:1 and then ground and pressed into sheets to be used as the negative electrode; the electrolyte is a solution containing 1 mol / L LiPF6, wherein the solvent is a mixed organic solvent of ethylene ester and diethyl carbonate (volume ratio 1:1); the separator is a microporous polypropylene membrane, and the lithium metal sheet is used as the counter electrode.

[0088] (2) The specific capacity test method is as follows: the battery assembled with the composite electrode materials provided in the above examples and comparative examples is subjected to constant current charge and discharge test on a CT2001A tester (Wuhan, LANHE) and the specific capacity of the composite electrode material is calculated.

[0089] (3) The method for testing the capacity retention rate after 100 charge-discharge cycles is as follows: The batteries assembled with the composite electrode materials provided in the above examples and comparative examples are subjected to 100 constant current charge-discharge tests on a CT2001A tester (Wuhan, LANHE), and the capacity retention rate of the composite electrode materials is calculated.

[0090] Table 1

[0091]

[0092] Figure 2 The graph shows the charge-discharge cycle performance of the secondary battery prepared from the composite electrode material provided in Example 2. Figure 2 It can be seen that the composite electrode material prepared in Example 2 has a high specific capacity. After 100 charge-discharge cycles, its specific capacity can still be maintained at 96.7%, with almost no capacity loss.

[0093] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0094] As can be seen from the comparison between Examples 1-12 and Comparative Examples 1-4, this application uses transition metal salts, urea biomass, biomass carbon, and inorganic fillers as raw materials to prepare a composite electrode material with a core-shell structure. Not only does it utilize transition metals as active sites to improve the theoretical specific capacity of the composite electrode material, but it also utilizes the layered structure of the hydrotalcite-based material and the porous structure of the carbon layer to increase the contact area between the composite electrode material and the electrolyte. At the same time, the conductive network of the carbon layer also promotes the rapid transfer of lithium ions, thereby achieving excellent electrochemical performance. Furthermore, by introducing inorganic fillers, the inorganic fillers can be distributed in the hydrotalcite-based material to further improve its structural stability, thereby improving its capacity stability.

[0095] A comparison of Examples 1-9 and Examples 10-11 shows that when the transition metal salt is a mixture of nickel nitrate and aluminum nitrate, and the molar ratio of the two is (1~4):1, it is more conducive to improving the specific capacity of the composite electrode material.

[0096] A comparison of Examples 1-9 with Example 12 shows that when the transition metal salt is a mixture of nickel nitrate and aluminum nitrate, it is more conducive to the formation of bimetallic active centers in the composite electrode material, which in turn is more conducive to improving the specific capacity of the composite electrode material.

[0097] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A composite electrode material, characterized in that, The raw materials of the composite electrode material, by weight, include: 30-50 parts of transition metal salt, 25-45 parts of urea, 20-30 parts of biomass carbon, and 5-20 parts of inorganic filler; the composite electrode material has a core-shell structure, with the core being a layered hydrotalcite material and the shell being a carbon layer with a microporous structure.

2. The composite electrode material according to claim 1, characterized in that, The transition metal salt includes at least two of nickel nitrate, cobalt nitrate, aluminum nitrate, or copper nitrate. And / or, the transition metal salt is a mixture of nickel nitrate and aluminum nitrate, and the molar ratio of the two is (1~4):

1.

3. The composite electrode material according to claim 1, characterized in that, The biomass carbon includes at least one of straw, wood chips, or cellulose; And / or, the inorganic filler includes at least one of alumina, silicon dioxide, and titanium dioxide; And / or, the particle size D50 of the inorganic filler is 2-6 μm.

4. A method for preparing a composite electrode material according to any one of claims 1 to 3, characterized in that, The preparation method includes: Step S1: The transition metal salt, urea, biomass carbon and inorganic filler are mixed in water to carry out a hydrothermal reaction to obtain the composite electrode precursor material. Step S2: The composite electrode precursor material is calcined to obtain the composite electrode material.

5. The preparation method according to claim 4, characterized in that, In step S1, the temperature of the hydrothermal reaction is 120-180℃, and the time of the hydrothermal reaction is 9-12h.

6. The preparation method according to claim 4, characterized in that, In step S2, the calcination temperature is 400-800℃ and the calcination time is 1-5h.

7. The preparation method according to claim 4, characterized in that, In step S2, the calcination process is carried out under the protection of a protective gas, which includes at least one of nitrogen, argon, or helium.

8. The preparation method according to any one of claims 4 to 7, characterized in that, Step S1 includes: adding the transition metal salt, urea, biomass carbon and inorganic filler to water to carry out the hydrothermal reaction to obtain hydrothermal products, and washing and drying the hydrothermal products in sequence to obtain the composite electrode precursor material.

9. The preparation method according to claim 8, characterized in that, The water washing is performed using deionized water or purified water. And / or, the drying temperature is 75-85℃, and the drying time is 10-15h.

10. A secondary battery, characterized in that, The secondary battery comprises the composite electrode material according to any one of claims 1 to 3 or the composite electrode material obtained by the preparation method according to any one of claims 4 to 9.

Images