Potassium rhenate doped layered oxide sodium battery positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of preparation of sodium-ion battery positive electrode materials, in particular to a potassium rhenate doped layered oxide sodium-ion battery positive electrode material and a preparation method and application thereof. The preparation method of the potassium rhenate doped layered oxide sodium battery positive electrode material comprises the following steps: uniformly mixing a layered oxide precursor, a sodium source and potassium rhenate, and carrying out first sintering treatment to obtain a first sintered material; and uniformly mixing the primary sintering material with a coating agent, and carrying out secondary sintering treatment to obtain the ceramic material. According to the invention, the potassium rhenate is used as a doping agent, and the coating agent is used for coating the material subjected to potassium rhenate doping modification, so that the prepared sodium battery positive electrode material not only has relatively high specific capacity, but also shows good cycle performance, and has good commercialization prospects.

Description

Technical Field

[0001] The invention relates to the technical field of sodium ion battery positive electrode material preparation, and in particular to a potassium rhenate-doped layered oxide sodium battery positive electrode material and a preparation method and application thereof. Background Art

[0002] Due to the advantages of low price and wide distribution of sodium resources, the research of sodium-ion batteries and their key electrode materials has attracted widespread attention in recent years. However, compared with lithium, the ionic radius of sodium is much larger, which makes its migration speed in sodium storage materials too slow, which seriously limits the improvement of sodium-ion battery rate performance and the expression of sodium storage capacity. In addition, the higher relative atomic mass of sodium also theoretically limits the energy density of sodium-ion batteries.

[0003] At present, the cathode materials used in sodium ion batteries mainly include transition metal oxide systems, polyanion compounds (phosphate systems, fluorophosphate systems, NASICON structures) and Prussian blue systems. Among them, transition metal oxide cathode materials have attracted widespread attention and research, but the specific capacity of such cathode materials is relatively low. If the working cut-off voltage is increased to obtain a higher specific capacity, it will cause a larger phase change of the material, which will lead to poor cycle performance of the material. Therefore, how to achieve the improvement of cycle performance while ensuring good electrochemical properties such as specific capacity needs to be solved urgently. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the existing transition metal oxide positive electrode materials are difficult to achieve improved cycle performance under the condition of good specific capacity, thereby providing a potassium rhenate-doped layered sodium oxide positive electrode material and its preparation method and application that solve the above problem.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a potassium rhenate-doped layered oxide sodium positive electrode material comprises: uniformly mixing a layered oxide precursor, a sodium source and potassium rhenate, and then performing a first sintering treatment to obtain a sintered material;

[0007] The first sintered material is mixed with the coating agent and then subjected to a second sintering treatment to obtain the product.

[0008] Preferably, the chemical formula of the layered oxide precursor is Ni x Fe y Mn z (OH)2; wherein 0.1≤x≤0.6, 0.1≤y≤0.5, 0.1≤z≤0.5, x+y+z=1;

[0009] And / or, the sodium source comprises sodium carbonate.

[0010] Preferably, the molar ratio of the metal element in the layered oxide precursor to the sodium element in the sodium source is 1:(0.90-1.06).

[0011] Preferably, the mass ratio of the layered oxide precursor to potassium rhenate is 1:(0.01-0.05).

[0012] Preferably, the temperature of the first sintering treatment is 950-1050°C, preferably 1000°C;

[0013] And / or, the duration of the first sintering treatment is 10-14 hours, preferably 12 hours;

[0014] And / or, the atmosphere of the first sintering treatment is air and / or oxygen.

[0015] Preferably, after the first sintering treatment, a coating agent is added and mixed, and then a second sintering treatment is performed.

[0016] Preferably, the coating agent is at least one of TiO2, Al2O3, Al(OH)3, Co(OH)2, and H3BO3; the coating agent is preferably TiO2.

[0017] Preferably, the coating amount of the coating agent is 0.5-1.5wt% of the mass of the sintered material, preferably 1wt%.

[0018] Preferably, the temperature of the second sintering treatment is 650-750°C, preferably 700°C;

[0019] And / or, the duration of the second sintering treatment is 5-7 hours, preferably 6 hours;

[0020] And / or, the atmosphere of the second sintering treatment is air and / or oxygen.

[0021] The present invention also provides a potassium rhenate-doped sodium layered oxide positive electrode material, which is prepared by the above-mentioned method for preparing the potassium rhenate-doped sodium layered oxide positive electrode material.

[0022] The present invention also provides application of the potassium rhenate-doped layered oxide sodium positive electrode material in a sodium ion battery.

[0023] The technical solution of the present invention has the following advantages:

[0024] A method for preparing a potassium rhenate-doped layered oxide sodium positive electrode material comprises: mixing a layered oxide precursor, a sodium source and potassium rhenate, and then performing a first sintering treatment to obtain a sintered material; mixing the sintered material with a coating agent and performing a second sintering treatment to obtain the sintered material. The present invention uses potassium rhenate as a dopant to allow Re to be doped into the transition metal layer of the layered oxygen structure, and the larger atomic radius forms a pinning effect, thereby achieving the technical effect of inhibiting crystal phase change. At the same time, the large-radius K ions doped in the sodium layer also play a supporting role for the transition metal layer, and the K0 strong bond significantly enhances the attraction between the transition metal layers, optimizes the lattice structure, and enables the prepared positive electrode material to exhibit good cycle performance under high voltage. At the same time, the present invention also uses a coating agent to coat the material after potassium rhenate doping and modification, so that the coating agent reacts with the residual alkali (sodium hydroxide, sodium carbonate, etc.) on the surface of the material, thereby achieving the purpose of reducing the residual alkali on the surface of the material. At the same time, the coating layer formed by the coating agent on the surface of the material can effectively isolate the direct contact between the electrolyte and the positive electrode material, thereby reducing the probability of harmful side reactions on the surface of the material during charging and discharging. Combining the above technical means, the sodium positive electrode material prepared by the present invention not only has a higher specific capacity, but also exhibits good cycle performance, and has good commercial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a SEM morphology of the potassium rhenate-doped layered sodium oxide cathode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0028] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0029] Example 1

[0030] This embodiment provides a method for preparing a potassium rhenate-doped layered sodium oxide positive electrode material, and the specific steps are as follows:

[0031] 1) 5.0 kg of precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 was mixed with 3.0 kg sodium carbonate and 0.05 kg potassium rhenate K2ReO4 in a high-speed mixer and then heated in a box furnace at 1000 °C in an air atmosphere (5 m 3 / h), sintering for 12h, and then crushing to obtain a burnt material;

[0032] 2) Weigh 500g of the calcined material and 5g of TiO2 and add them into a high-speed mixer to mix them evenly. Then, heat them in a box furnace at 700℃ and air atmosphere (5m 3 / h), sintered for 6h for secondary sintering coating, after sintering, potassium rhenate doped layered sodium oxide positive electrode material was obtained, and its SEM morphology is as follows Figure 1 shown.

[0033] Example 2

[0034] This embodiment provides a method for preparing a potassium rhenate-doped layered sodium oxide positive electrode material, and the specific steps are as follows:

[0035] 1) 5.0 kg of precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 was mixed with 3.0 kg sodium carbonate and 0.05 kg potassium rhenate K2ReO4 in a high-speed mixer and then heated in a box furnace at 1000 °C in an air atmosphere (5 m 3 / h), sintering for 12h, and then crushing to obtain a burnt material;

[0036] 2) Weigh 500g of the calcined material and 5g of Al2O3 and add them into a high-speed mixer to mix them evenly. Then, heat them in a box furnace at 700℃ and air atmosphere (5m 3 / h), sintering for 6h for secondary sintering coating, after the sintering is completed, the potassium rhenate doped layered sodium oxide positive electrode material is obtained.

[0037] Example 3

[0038] This embodiment provides a method for preparing a potassium rhenate-doped layered sodium oxide positive electrode material, and the specific steps are as follows:

[0039] 1) 5.0 kg of precursor Ni 0.1 Fe 0.5 Mn 0.4(OH)2 was mixed with 2.7kg sodium carbonate and 0.15kg potassium rhenate K2ReO4 in a high-speed mixer and then heated in a box furnace at 1000°C in an air atmosphere (5m 3 / h), sintering for 12h, and then crushing to obtain a burnt material;

[0040] 2) Weigh 500g of the calcined material and 5g of TiO2 and add them into a high-speed mixer to mix them evenly. Then, heat them in a box furnace at 700℃ and air atmosphere (5m 3 / h), sintering for 6h for secondary sintering coating, after the sintering is completed, the potassium rhenate doped layered sodium oxide positive electrode material is obtained.

[0041] Example 4

[0042] This embodiment provides a method for preparing a potassium rhenate-doped layered sodium oxide positive electrode material, and the specific steps are as follows:

[0043] 1) 5.0 kg of precursor Ni 0.6 Fe 0.1 Mn 0.3 (OH)2 was mixed with 3.07kg sodium carbonate and 0.25kg potassium rhenate K2ReO4 in a high-speed mixer and then heated in a box furnace at 1000°C in an air atmosphere (5m 3 / h), sintering for 12h, and then crushing to obtain a burnt material;

[0044] 2) Weigh 500g of the calcined material and 5g of TiO2 and add them into a high-speed mixer to mix them evenly. Then, heat them in a box furnace at 700℃ and air atmosphere (5m 3 / h), sintering for 6h for secondary sintering coating, after the sintering is completed, the potassium rhenate doped layered sodium oxide positive electrode material is obtained.

[0045] Comparative Example 1

[0046] This comparative example provides a method for preparing a potassium rhenate-doped layered sodium oxide positive electrode material, and the specific steps are as follows:

[0047] 5.0 kg of precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 was mixed with 3.0 kg sodium carbonate and 0.05 kg potassium rhenate K2ReO4 in a high-speed mixer and then heated in a box furnace at 1000 °C in an air atmosphere (5 m 3 / h), sintered for 12h, and then crushed to obtain potassium rhenate-doped layered sodium oxide positive electrode material.

[0048] Comparative Example 2

[0049] This comparative example provides a method for preparing a layered sodium oxide positive electrode material, and the specific steps are as follows:

[0050] 1) 5.0 kg of precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 was mixed with 3.0 kg of sodium carbonate in a high-speed mixer and then heated in a box furnace at 1000 °C in an air atmosphere (5 m 3 / h), sintering for 12h, and then crushing to obtain a burnt material;

[0051] 2) Weigh 500g of the calcined material and 5g of TiO2 and add them into a high-speed mixer to mix them evenly. Then, heat them in a box furnace at 700℃ and air atmosphere (5m 3 / h), sintering for 6h for secondary sintering coating, and after the sintering is completed, the layered oxide sodium positive electrode material is obtained.

[0052] Comparative Example 3

[0053] This comparative example provides a method for preparing a potassium rhenate-doped layered sodium oxide positive electrode material, and the specific steps are as follows:

[0054] 1) 5.0 kg of precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 was mixed with 3.0 kg sodium carbonate and 0.05 kg sodium rhenate in a high-speed mixer and then heated in a box furnace at 1000 °C in an air atmosphere (5 m 3 / h), sintering for 12h, and then crushing to obtain a burnt material;

[0055] 2) Weigh 500g of the calcined material and 5g of TiO2 and add them into a high-speed mixer to mix them evenly. Then, heat them in a box furnace at 700℃ and air atmosphere (5m 3 / h), sintering for 6h for secondary sintering coating, after the sintering is completed, the potassium rhenate doped layered sodium oxide positive electrode material is obtained.

[0056] Test Example 1

[0057] The NFPP sodium positive electrode material obtained in the above examples and comparative examples was made into a battery, and the specific steps were as follows: a slurry was applied at a mass ratio of 95 (NFPP material): 2.5 (polytetrafluoroethylene (PVDF)): 2.5 (conductive carbon black SP) to form a pole piece, and the coating surface density was 7.4 mg / cm 2, using sodium metal as the counter electrode, glass fiber as the separator, and 1 mol / L NaPF6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 1:1) as the electrolyte, a CR2032 button cell was assembled. The prepared battery was placed in a blue power test system for electrical performance testing, with a voltage range of 2.0-4.2V, and its 0.1C charge and discharge specific capacity and first efficiency were tested, and its 50-cycle cycle retention rate was tested at a charge and discharge rate of 1C. The test results are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing a potassium rhenate-doped layered sodium oxide positive electrode material, characterized in that: include: The layered oxide precursor, the sodium source and potassium rhenate are mixed and then subjected to a first sintering treatment to obtain a sintered material; The first sintered material is mixed with the coating agent and then subjected to a second sintering treatment to obtain the product.

2. The preparation method according to claim 1, characterized in that: The chemical formula of the layered oxide precursor is Ni x Fe y Mn z (OH)2; wherein 0.1≤x≤0.6, 0.1≤y≤0.5, 0.1≤z≤0.5, x+y+z=1; And / or, the sodium source comprises sodium carbonate.

3. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the metal element in the layered oxide precursor to the sodium element in the sodium source is 1:(0.90-1.06).

4. The preparation method according to any one of claims 1 to 3, characterized in that The mass ratio of the layered oxide precursor to potassium rhenate is 1:(0.01-0.05).

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperature of the first sintering treatment is 950-1050°C, preferably 1000°C; And / or, the duration of the first sintering treatment is 10-14 hours, preferably 12 hours; And / or, the atmosphere of the first sintering treatment is air and / or oxygen.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The coating agent is at least one of TiO2, Al2O3, Al(OH)3, Co(OH)2, and H3BO3; the coating agent is preferably TiO2.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The coating amount of the coating agent is 0.5-1.5wt% of the mass of the sintered material, preferably 1wt%.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The temperature of the second sintering treatment is 650-750°C, preferably 700°C; And / or, the duration of the second sintering treatment is 5-7 hours, preferably 6 hours; And / or, the atmosphere of the second sintering treatment is air and / or oxygen.

9. A potassium rhenate-doped layered sodium oxide positive electrode material, characterized in that: The material is prepared by the method for preparing the potassium rhenate-doped layered sodium oxide positive electrode material according to any one of claims 1 to 8.

10. Use of the potassium rhenate-doped layered oxide sodium positive electrode material according to claim 9 in a sodium ion battery.

Images