Preparation method of cathode composite material, cathode plate and sodium ion battery

Abstract

The invention provides a preparation method of a cathode composite material, a cathode plate and a sodium ion battery. Relates to the technical field of sodium-ion batteries. The preparation method of the cathode composite material comprises the following steps: adding a doped raw material into deionized water, and uniformly dispersing to obtain a dispersion liquid; performing low-temperature freezing treatment on the nickel salt solution and the sodium hydroxide solution to obtain solid nickel salt and solid sodium hydroxide, and melting the solid nickel salt and the solid sodium hydroxide at room temperature to a molten state to obtain molten nickel salt and molten sodium hydroxide; adding molten nickel salt and molten sodium hydroxide into the dispersion liquid, uniformly stirring and mixing to obtain mixed slurry, centrifuging, washing and drying to obtain a precursor material; and uniformly mixing the precursor material, sodium salt and sodium fluoride, grinding, sieving and calcining to obtain the cathode composite material. The cathode composite material prepared by the preparation method provided by the invention is applied to a cathode sheet, and the sodium ion battery obtained by assembling is excellent in cycle performance, good in conductivity and wide in application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a method for preparing a cathode composite material, a cathode sheet and a sodium ion battery. Background Art

[0002] Sodium-ion battery is a secondary battery with a working principle similar to that of lithium-ion battery. Research on sodium-ion batteries began around the 1980s. The electrochemical performance of the electrode materials designed and developed in the early days (such as MoS2, TiS2 and NaxMO2) was not ideal, and development was very slow. Finding suitable sodium-ion electrode materials is one of the keys to the practical application of sodium-ion energy storage batteries. Since 2010, a series of positive and negative electrode materials have been designed and developed based on the characteristics of sodium-ion batteries, such as hard carbon materials, transition metals and their alloy compounds as negative electrodes, polyanions, Prussian blue, oxide materials as positive electrodes, especially layered structures of Na x MO2 (M=Fe, Mn, Co, V, Ti) and its binary and ternary materials, etc.

[0003] Layered structure of Na x Although MO2 has broad application prospects in the fields of materials science and electrochemistry, its application is limited by its poor cycle performance and poor conductivity. Specifically, during the battery charge and discharge cycle, transition metal layered oxides are prone to phase transformation and structural rearrangement, resulting in poor cycle performance of the material; although the layered structure provides a path for the insertion and extraction of sodium ions, the ion transfer rate is still limited, the diffusion energy barrier of sodium ions is high, and the kinetic performance is low. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a cathode composite material, a cathode sheet and a sodium ion battery to solve the problem of Na x MO2 (M = Fe, Mn, Co, V, Ti) materials have poor cycle performance and poor conductivity.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In a first aspect, a method for preparing a cathode composite material comprises the following steps:

[0007] S1. The doping raw material is added to deionized water and dispersed evenly to obtain a dispersion;

[0008] S2. The nickel salt solution and the sodium hydroxide solution are cryogenically frozen to obtain a solid nickel salt and solid sodium hydroxide, which are melted at room temperature (25-30 ° C) to a molten state to obtain a molten nickel salt and molten sodium hydroxide;

[0009] S3. The molten nickel salt and molten sodium hydroxide are added to the dispersion, stirred and mixed, and the resulting mixed slurry is centrifuged, washed, and dried to obtain a precursor material;

[0010] S4. Evenly mix the precursor material, sodium salt, and sodium fluoride, grind and sieve, and calcine to obtain a cathode composite material.

[0011] As a further solution of the present invention, in S1, the solid content of the dispersion is 10-30%.

[0012] As a further solution of the present invention, in S1, the doping raw material consists of nano metal oxide and composite nano metal oxide in a mass ratio of 1:1.

[0013] Furthermore, the nano metal oxide is any one or more of nano titanium oxide, nano magnesium oxide, nano aluminum oxide, nano ruthenium oxide, nano palladium oxide, and nano rhodium oxide mixed in any proportion.

[0014] Furthermore, the preparation method of the composite nano-metal oxide comprises the following steps:

[0015] Compound A is mixed with magnesium nitrate solution, subjected to ultrasonic treatment, and the pH value is adjusted to 9.5-11.5. The mixture is dried and calcined to prepare a composite nano-metal oxide.

[0016] Furthermore, the compound A is any one or more of nano zinc oxide, nano aluminum oxide, nano titanium oxide, nano cerium oxide, and nano barium titanate mixed in any proportion;

[0017] The mass ratio of compound A to magnesium nitrate is 1:(5-10).

[0018] Furthermore, the calcination temperature is 600-800° C., and the calcination time is 2-4 hours.

[0019] As a further solution of the present invention, in S2, the concentration of the nickel salt solution is 5-10 wt%, and the nickel salt is any one of nickel nitrate, nickel chloride or nickel sulfate.

[0020] As a further embodiment of the present invention, in S2, the concentration of the sodium hydroxide solution is 5-10 wt%.

[0021] As a further embodiment of the present invention, the mass ratio of the doping raw material, the nickel salt and the sodium hydroxide is (0.01-0.2):1:1.

[0022] As a further solution of the present invention, in S4, the mass ratio of the precursor material, sodium salt and sodium fluoride is (0.8-2.0):1:(0.001-0.03).

[0023] As a further embodiment of the present invention, in S4, the sodium salt is any one of sodium carbonate, sodium bicarbonate or sodium dihydrogen phosphate.

[0024] As a further solution of the present invention, in S4, the calcination temperature is 350-450° C., the calcination time is 1-2 h, and the calcination atmosphere is oxygen.

[0025] In a second aspect, a cathode sheet includes a cathode composite material, wherein the cathode composite material is prepared by the preparation method of the first aspect.

[0026] In a third aspect, a sodium ion battery comprises the cathode sheet described in the second aspect.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention provides a method for preparing a cathode composite material. During the preparation process, a doping raw material composed of nanometal oxides and composite nanometal oxides is introduced as nuclei for the growth of transition metal layered oxide crystals. This not only changes the crystal structure, improving the battery's cycle performance and conductivity, but also effectively increases the dispersion of the doping elements, achieving maximum atomic utilization. The cathode composite material prepared using the preparation method provided by the present invention is applied to cathode sheets, and the resulting sodium-ion battery assembled therefrom exhibits excellent cycle performance and good conductivity, and has broad application prospects.

[0029] 2. The doping raw material in the present invention is composed of nano metal oxide and composite nano metal oxide in a mass ratio of 1:1. On the one hand, the high specific surface area of ​​the nanoparticles is used to increase the contact area of ​​the electrode / electrolyte and shorten the Na +The diffusion path of the electrode material is improved, thereby improving the reaction kinetics. At the same time, when nano-metal oxides are introduced into the prepared cathode composite material, they can serve as the nuclei for the growth of transition metal layered oxide crystals, change the crystal structure, and thus improve the cycle performance of the sodium ion battery and improve its conductivity. Composite nano-metal oxides are to embed other nano-metal oxide particles into nano-magnesium oxide, while combining the advantages of the stability of nano-magnesium oxide and introducing the advantages of other materials. Specifically, nano-magnesium oxide has high mechanical strength and chemical stability. As a matrix, it can alleviate the volume expansion of the electrode material during charging and discharging and prevent structural collapse. At the same time, due to the introduction of other nano-metal oxide particles into nano-magnesium oxide, a porous structure is formed, which further improves the stress resistance of the electrode and extends its cycle life. In addition, the introduction of other nano-metal oxide particles into nano-magnesium oxide can achieve a balance between high capacity and long cycle. Through the combination of nano-metal oxides and composite nano-metal oxides, the key bottlenecks of sodium ion batteries (such as poor cycle performance, poor conductivity, etc.) can be synergistically solved, providing new ideas for low-cost, high-performance energy storage materials.

[0030] 3. The introduction of sodium fluoride can partially replace the O in the material 2- , which can achieve the stability of the crystal structure, thereby inhibiting phase change, forming a fluoride coating under high temperature conditions, and forming an MgO-MgF2 electrochemical composite inert coating layer with Mg doped in the composite nano-metal oxide, stabilizing the material surface and grain boundaries, reducing the corrosion of the electrolyte on the active material, and stabilizing the transmission of Na+. At the same time, both MgO and MgF2 can capture HF in the electrolyte (a common corrosive byproduct in lithium / sodium batteries), thereby extending the material life. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0032] The terms used in the examples of this application are for the purpose of describing specific implementation rules only and are not intended to limit this application. The singular forms "a", "an", "the" and "the" used in the implementation rules of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0033] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0034] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0035] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0037] The following is further explained with reference to specific embodiments.

[0038] Preparation Example 1

[0039] This preparation example provides a method for preparing a composite nano-metal oxide, wherein compound A is composed of a mixture of nano-zinc oxide and nano-barium titanate in a mass ratio of 1:1; compound A and magnesium nitrate are weighed in a mass ratio of 1:8;

[0040] The specific steps include:

[0041] Compound A was mixed with magnesium nitrate solution, and after ultrasonic treatment, the pH was adjusted to 10. After uniform mixing, the mixture was centrifuged and dried, and the mixture was calcined at 650° C. for 3 h to prepare a composite nano-metal oxide.

[0042] Preparation Example 2

[0043] This preparation example provides a method for preparing a composite nano-metal oxide, wherein compound A is composed of a mixture of nano-zinc oxide, nano-cerium oxide, and nano-barium titanate in a mass ratio of 1:1:1; compound A and magnesium nitrate are weighed in a mass ratio of 1:5;

[0044] The specific steps include:

[0045] Compound A was mixed with magnesium nitrate solution, and after ultrasonic treatment, the pH was adjusted to 10. After mixing evenly, the mixture was centrifuged and dried, and the mixture was calcined at 600° C. for 4 hours to prepare a composite nano-metal oxide.

[0046] Preparation Example 3

[0047] This preparation example provides a method for preparing a composite nano-metal oxide, wherein compound A is composed of a mixture of nano-zinc oxide and nano-barium titanate in a mass ratio of 1:1; compound A and magnesium nitrate are weighed in a mass ratio of 1:10;

[0048] The specific steps include:

[0049] Compound A is mixed with magnesium nitrate solution, and after ultrasonic treatment, the pH value is adjusted to 10. After uniform mixing, the mixture is centrifuged and dried, and the mixture is calcined at 800° C. for 2 h to prepare a composite nano-metal oxide.

[0050] Example 1

[0051] This embodiment provides a method for preparing a cathode composite material, wherein the doping raw material is composed of nano-magnesium oxide and the composite nano-metal oxide prepared in Preparation Example 1 in a mass ratio of 1:1;

[0052] The following steps are involved:

[0053] S1. 1.6g of the doping raw material was added to deionized water and dispersed evenly to obtain a dispersion having a solid content of 20%;

[0054] S2. 200g of 8wt% nickel nitrate solution and 200g of 8wt% sodium hydroxide solution were cryogenically frozen to obtain solid nickel nitrate and solid sodium hydroxide, which were melted to a molten state at room temperature to obtain molten nickel salt and molten sodium hydroxide;

[0055] S3. The molten nickel salt and molten sodium hydroxide are added to the dispersion, stirred and mixed, and the resulting mixed slurry is centrifuged, washed, and dried to obtain a precursor material;

[0056] S4. 10 g of the precursor material, 10 g of sodium carbonate, and 0.2 g of sodium fluoride were mixed evenly, ground through a 200-mesh sieve, placed in an oxygen atmosphere, and calcined at 400° C. for 1.5 h to obtain a cathode composite material.

[0057] Example 2

[0058] This embodiment provides a method for preparing a cathode composite material. The difference from Example 1 is that the amount of the doping raw material is replaced with 0.16 g (i.e., the mass ratio of the doping raw material, nickel nitrate, and sodium hydroxide is 0.01:1:1), and the other steps and parameters remain the same.

[0059] Example 3

[0060] This embodiment provides a method for preparing a cathode composite material. The difference from Example 1 is that the amount of the doping raw material is replaced with 3.2 g (i.e., the mass ratio of the doping raw material, nickel nitrate, and sodium hydroxide is 0.2:1:1), and the other steps and parameters remain the same.

[0061] Example 4

[0062] This embodiment provides a method for preparing a cathode composite material. The difference from Example 1 is that the doping raw material is replaced by nano-magnesium oxide and the composite nano-metal oxide prepared in Preparation Example 2 in a mass ratio of 1:1; the other steps and parameters remain the same.

[0063] Example 5

[0064] This embodiment provides a method for preparing a cathode composite material. The difference from Example 1 is that the doping raw material is replaced by nano-magnesium oxide and the composite nano-metal oxide prepared in Preparation Example 3 in a mass ratio of 1:1; the other steps and parameters remain the same.

[0065] Example 6

[0066] This embodiment provides a method for preparing a cathode composite material. The difference from Example 1 is that in S4, the amount of sodium fluoride is replaced with 0.01 g (i.e., the mass ratio of the precursor material, sodium salt, and sodium fluoride is 1:1:0.001), and the remaining steps and parameters remain the same.

[0067] Example 7

[0068] This embodiment provides a method for preparing a cathode composite material. The difference from Example 1 is that in S4, the amount of sodium fluoride is replaced with 0.3 g (i.e., the mass ratio of the precursor material, sodium salt, and sodium fluoride is 1:1:0.02), and the remaining steps and parameters remain the same.

[0069] Example 8

[0070] This embodiment provides a method for preparing a cathode composite material. The difference from Example 1 is that in S4, the amount of the precursor material is replaced with 20 g (i.e., the mass ratio of the precursor material, sodium salt, and sodium fluoride is 2:1:0.02), and the remaining steps and parameters remain the same.

[0071] Example 9

[0072] This embodiment provides a method for preparing a cathode composite material. The difference from Example 1 is that in S4, the amount of the precursor material is replaced with 8 g (i.e., the mass ratio of the precursor material, sodium salt, and sodium fluoride is 0.8:1:0.02), and the remaining steps and parameters remain the same.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing a cathode composite material, which differs from Example 1 in that sodium fluoride is not added in S4, and the remaining steps and parameters remain the same.

[0075] Comparative Example 2

[0076] This comparative example provides a method for preparing a cathode composite material, which differs from Example 1 in that the doping raw material consists only of nano-magnesium oxide, and the other steps and parameters remain the same.

[0077] Comparative Example 3

[0078] This comparative example provides a method for preparing a cathode composite material, which differs from Example 1 in that the doping raw material consists only of the composite metal oxide prepared in Preparation Example 1, and the remaining steps and parameters remain the same.

[0079] Comparative Example 4

[0080] This comparative example provides a method for preparing a cathode composite material, which differs from Example 1 in that the doping raw material consists only of magnesium oxide, and the remaining steps and parameters remain the same.

[0081] Comparative Example 5

[0082] This comparative example provides a method for preparing a cathode composite material. The difference from Example 1 is that the doping raw material consists only of nano-magnesium oxide, and sodium fluoride is not added to S4. The other steps and parameters remain the same.

[0083] Comparative Example 6

[0084] This comparative example provides a method for preparing a cathode composite material. The difference from Example 1 is that the doping raw material consists only of the composite metal oxide prepared in Preparation Example 1, and sodium fluoride is not added in S4. The other steps and parameters remain the same.

[0085] Performance testing:

[0086] Cathode sheets were prepared using the cathode composite materials prepared in Examples 1-9 and Comparative Examples 1-6, and the cathode sheets were assembled into corresponding sodium ion batteries, and the performance of the assembled sodium ion batteries was tested.

[0087] The assembly method of the sodium ion battery is as follows:

[0088] The prepared cathode composite material was ground in a mortar and passed through a 200-mesh sieve. The cathode composite material, conductive carbon powder, and 12 wt% PVDF (wherein the solvent was NMP) were mixed in a mass ratio of 7:1:1, and then stirred with a magnetic stirrer for 2 h to prepare a slurry. The slurry was coated on aluminum foil using an automatic coating machine, dried in a 50°C oven, and then dried in a vacuum drying oven at 110°C for 12 h to obtain an aluminum foil sheet. The aluminum foil sheet was pressed by a small roller press and punched by a slicer to obtain a cathode sheet. The cathode sheet was placed in a glove box for 2 h. 032 battery assembly, specifically, the cathode sheet is placed in the middle of the positive electrode shell, and 35uL of electrolyte is measured and dripped on the electrode sheet; the glass fiber diaphragm sheet is covered on the sodium ion battery cathode sheet, and 35uL of electrolyte is dripped on the glass fiber diaphragm sheet. After the electrolyte completely soaks the glass fiber diaphragm sheet, the conductive steel sheet is placed on the reference electrode; the reference electrode is then placed in the center of the diaphragm, a metal gasket is added to the conductive steel sheet, and finally the negative electrode shell is covered, and the button battery packaging machine is used to seal it. After static activation for 10 hours, the sodium ion battery is prepared.

[0089] The electrolyte is a 1 mol / L sodium perchlorate PC solution, the diaphragm is a glass fiber diaphragm, and the reference electrode is a sodium sheet.

[0090] The prepared sodium ion battery was subjected to electrochemical performance tests at 0.3C and 2C rates, respectively. The test results are summarized in Table 1.

[0091] Table 1

[0092]

[0093] As can be seen from Table 1, by adopting a doping raw material composed of a mixture of nano-metal oxides and composite nano-metal oxides, further co-precipitating with molten titanium nickel salt to form a composite phase with a uniform structure, and then mixing and calcining with sodium salt and sodium fluoride, the synergistic effect of the trinity of nano-metal oxides and composite nano-metal oxides, sodium fluoride and composite nano-metal oxides is achieved.

[0094] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0095] The above disclosures are only a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a cathode composite material, characterized in that: The following steps are involved: S1. The doping raw material is added to deionized water and dispersed evenly to obtain a dispersion; S2. The nickel salt solution and the sodium hydroxide solution are cryogenically frozen to obtain a solid nickel salt and solid sodium hydroxide, which are melted at room temperature to a molten state to obtain a molten nickel salt and molten sodium hydroxide; S3. The molten nickel salt and molten sodium hydroxide are added to the dispersion, stirred and mixed, and the resulting mixed slurry is centrifuged, washed, and dried to obtain a precursor material; S4. Evenly mix the precursor material, sodium salt, and sodium fluoride, grind and sieve, and then calcine to obtain a cathode composite material.

2. The method for preparing a cathode composite material according to claim 1, wherein: In S1, the doping raw material is composed of nano metal oxide and composite nano metal oxide in a mass ratio of 1:

1.

3. The method for preparing a cathode composite material according to claim 2, wherein: The nano metal oxide is any one or more of nano titanium oxide, nano magnesium oxide, nano aluminum oxide, nano ruthenium oxide, nano palladium oxide, and nano rhodium oxide, mixed in any proportion.

4. The method for preparing a cathode composite material according to claim 2, wherein: The preparation method of the composite nano-metal oxide comprises the following steps: Compound A is mixed with magnesium nitrate solution, subjected to ultrasonic treatment, and the pH value is adjusted to 9.5-11.

5. The mixture is dried and calcined to prepare a composite nano-metal oxide.

5. The method for preparing a cathode composite material according to claim 4, wherein: The compound A is any one or more of nano zinc oxide, nano aluminum oxide, nano titanium oxide, nano cerium oxide, and nano barium titanate mixed in any proportion; The mass ratio of compound A to magnesium nitrate is 1:(5-10).

6. The method for preparing a cathode composite material according to claim 1, wherein: In S2, the concentration of the nickel salt solution is 5-10 wt%, and the nickel salt is any one of nickel nitrate, nickel chloride or nickel sulfate; the concentration of the sodium hydroxide solution is 5-10 wt%.

7. The method for preparing a cathode composite material according to claim 1, characterized in that: The mass ratio of the doping raw material, nickel salt and sodium hydroxide is (0.01-0.2):1:

1.

8. The method for preparing a cathode composite material according to claim 1, characterized in that: In S4, the mass ratio of the precursor material, sodium salt and sodium fluoride is (0.8-2.0):1:(0.001-0.03).

9. A cathode sheet, characterized in that: The cathode sheet includes a cathode composite material, and the cathode composite material is prepared by the preparation method according to claim 1.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the cathode sheet according to claim 9.

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