Preparation and application of a hybrid battery cathode material capable of potassium-sodium dual-ion extraction

Abstract

The present invention discloses the preparation of a mixed positive electrode material capable of realizing the release of sodium-potassium dual ions from a battery and its application in a secondary battery. The positive electrode sheet is prepared by mixing sodium vanadium acid and Prussian blue, and the sodium-potassium liquid alloy is adsorbed on carbon cloth as the negative electrode material. When preparing the battery, the mixed electrolyte is added dropwise to prepare a mixed ion sodium-potassium alloy full battery. The mixed ion full battery of the present invention has a 100% sodium-potassium alloy utilization rate and the retention of the sodium-potassium liquid alloy of the negative electrode, which greatly improves the stability of the sodium-potassium liquid alloy battery, has high coulomb efficiency, and cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary battery positive electrode materials, and specifically to a preparation method of a full battery mixed with a potassium storage positive electrode material and an intelligent sodium storage positive electrode material, a study of its dual ion release characteristics, and an application in secondary batteries. Background Art

[0002] Decades ago, the burning of a large amount of chemical fuels caused irreversible environmental pollution. At the same time, fossil fuels began to deplete, and the energy crisis became the cusp. Therefore, how to create an efficient and environmentally friendly energy storage system has become a common direction for the world to work on, and the development of efficient energy storage batteries is a key step in achieving this direction. In the past decade, lithium batteries have stood out due to their high energy density, convenience, and fast charging and discharging, and are considered to be a promising battery. Lithium batteries have also developed rapidly, but at this stage, the demand for lithium has increased greatly, the distribution of lithium mines is uneven, the pressure on lithium prices has gradually increased, and the cost of lithium batteries has increased. At the same time, the battery performance limit that lithium batteries cannot break through has also been criticized. So people's attention has gradually shifted to sodium, potassium, and sodium-potassium alloys. Compared with lithium, the battery cost of these three is relatively low, and the source is wide, and the physical and chemical properties of the same first main group are also similar. Among them, sodium-potassium alloy as the negative electrode often releases single ions, which depends on its matching positive electrode material. This means that the sodium-potassium alloy battery wastes a part of the metal material, and this waste is undoubtedly a failure to make full use of it. Therefore, the research of a sodium-potassium alloy full battery that is a mixture of a potassium storage positive electrode material and an intelligent sodium storage positive electrode material is of great significance to the development of sodium-potassium alloy batteries.

[0003] At present, in addition to continuously improving the positive electrode material, i.e., the modification of the positive electrode material, and preparing a positive electrode material with a better structure to increase the battery performance, the research on sodium-potassium alloy batteries at home and abroad also includes the research on sodium-potassium synergistic reaction dual-ion batteries to improve the performance of sodium-potassium alloy batteries. Therefore, the concept of dual-ion extraction is extremely fresh and promising. The research on a sodium-potassium alloy full battery that is a mixture of a potassium storage positive electrode material and an intelligent sodium storage positive electrode material is also a major direction for the development of sodium-potassium alloy batteries. Summary of the invention

[0004] In view of the problems in the background technology, the purpose of the present invention is to provide a method for realizing the release of sodium-potassium dual ions from a battery by using a mixed positive electrode material of sodium vanadium phosphate and Prussian blue and its application in the field of secondary batteries.

[0005] A method for realizing sodium-potassium dual ion release from a battery using a positive electrode material mixed with a sodium-based positive electrode and a potassium-based positive electrode comprises the following steps:

[0006] 1) Mix the positive electrode material for potassium storage and the positive electrode material for sodium storage in a certain proportion.

[0007] 2) After the mixed positive electrode material is mixed with the conductive agent and the binder in a certain proportion, a certain volume of organic solvent is added dropwise to prepare a mixed slurry, which is then coated on a current collector to obtain a mixed positive electrode sheet.

[0008] 3) Match the positive electrode sheet with a certain proportion of sodium-potassium alloy negative electrode, add mixed electrolyte, or mixed solid electrolyte to prepare a mixed ion full battery.

[0009] The potassium storage cathode material described in step 1) is a cathode material that preferentially reacts with potassium ions, and may be a metal oxide, sulfur, Prussian blue, etc., preferably a Prussian blue material.

[0010] The Prussian blue material includes a variety of derivative structures, such as iron-iron Prussian blue, iron-manganese Prussian blue, iron-nickel Prussian blue, and nickel-manganese Prussian blue, preferably iron-iron Prussian blue material.

[0011] The sodium storage positive electrode material described in step 1) is a positive electrode material that can only react with sodium ions but not potassium ions, and can be a metal oxide, sodium vanadium phosphate, metal sulfide, polymer material, etc., preferably sodium vanadium phosphate.

[0012] The sodium vanadium phosphate material has a variety of derivatives, such as sodium manganese vanadium phosphate, sodium iron vanadium phosphate, sodium zirconium vanadium phosphate, etc., preferably sodium vanadium phosphate.

[0013] The certain ratio in step 1) is obtained by converting the ratio of sodium to potassium in the sodium-potassium alloy and the theoretical capacity of sodium vanadium phosphate and Prussian blue material to obtain the capacity of sodium and potassium that can be released.

[0014] The mass ratio of the sodium and potassium released is calculated based on the specific capacity. This method calculates the mixing ratio of the positive electrode material according to the following formula:

[0015]

[0016] Where m1 is the mass of the sodium ion positive electrode material; m2 is the specific capacity of the sodium ion positive electrode material; C1 is the specific capacity of the sodium ion positive electrode material; C2 is the specific capacity of the potassium ion positive electrode material; p K M is the mass proportion of potassium in sodium-potassium alloy; Na is the relative atomic mass of sodium; M K is the relative atomic mass of potassium.

[0017] The ratio of the conductive agent (conductive carbon black): binder (polyvinylidene fluoride): positive electrode material (mixed sodium vanadium phosphate and iron-based Prussian blue) described in step 2) can be 1:1:8, 1:1:3, 1:1:16, preferably 1:1:8.

[0018] The certain volume of organic solvent described in step 2) can be dipropylene glycol dimethyl ether, butyrolactone, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, etc., preferably N-methylpyrrolidone.

[0019] The mixed slurry described in step 2) is prepared by mixing the positive electrode material, the conductive agent and the binder, adding NMP dropwise until the viscosity is moderate, and magnetically stirring at room temperature for 2-3 hours.

[0020] The sodium-potassium alloy in a certain proportion in step 3) may be 30-90% by mass fraction of potassium, preferably 60-80%, and most preferably 78%.

[0021] The sodium-potassium alloy electrode can be prepared by two methods: high-temperature adsorption and non-Newtonian fluid state.

[0022] The high temperature adsorption is to heat the sodium-potassium alloy to 400° C., place the carrier material close to the alloy for adsorption, and then cool it to form a sodium-potassium alloy composite electrode.

[0023] The non-Newtonian fluid state preparation method is to mechanically mix a powder material containing trace amounts of water with a sodium-potassium alloy.

[0024] The mixed electrolyte or mixed solid electrolyte described in step 3) refers to a mixture of (solid) electrolytes of Na and K, and the ratio thereof is the same as that of the positive electrode material.

[0025] The purpose of the method for realizing the sodium-potassium dual ion release of a battery by using a positive electrode material mixed with a sodium-based positive electrode and a potassium-based positive electrode is to utilize the limiting effect of the positive electrode material to ensure that the sodium ions and potassium ions can only enter the interior of a specific material, so that the sodium ions and potassium ions in the battery reaction react in a certain proportion, and ensure that the proportion of the negative electrode sodium-potassium alloy remains unchanged, thereby maintaining the dendrite-free characteristics unchanged.

[0026] Compared with the prior art, the present invention has the following advantages and outstanding effects:

[0027] The method for realizing the sodium-potassium dual ion release of a battery by using a mixed positive electrode material of sodium vanadium phosphate and Prussian blue prepared by the present invention has the following two advantages: 1) The battery prepared by the method can achieve sodium and potassium release according to the mass ratio of potassium to sodium in the sodium-potassium liquid alloy of 78:22 according to theoretical calculations because the positive electrode material and the electrolyte are mixed in an appropriate ratio, so the utilization rate of the sodium-potassium liquid alloy can be increased, and 100% utilization can be achieved, thereby reducing resource waste and improving energy utilization. Compared with the previous sodium-vanadium phosphate sodium-potassium liquid alloy battery and the sodium-potassium liquid alloy battery of Prussian blue, the sodium-potassium liquid alloy can be better utilized. 2) At the same time, because sodium and potassium are released according to the mass ratio of potassium to sodium in the sodium-potassium liquid alloy of 78:22, it means that during the reaction process, the remaining sodium-potassium alloy not only maintains the optimal ratio of 78:22, but also will not be converted from the sodium-potassium liquid alloy into a solid alloy due to the lack of a certain metal, thereby not generating dendrites, preventing the battery from short-circuiting, etc., to ensure that the performance of the battery is not affected. The previous sodium potassium vanadium phosphate liquid alloy battery and the sodium potassium liquid alloy battery of Prussian blue only release one metal, which eventually leads to the transformation of the negative electrode from liquid to solid, resulting in dendrites, short circuit of the battery, great impact on battery performance, and sharp decline in capacity retention. Compared with this phenomenon, the present invention avoids this situation and greatly improves the performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the preparation method of a mixed ion full battery;

[0029] Figure 2 This is the XRD diffraction pattern of sodium vanadium phosphate prepared by the gel removal method;

[0030] Figure 3 is the charge and discharge curve diagram of Example 1;

[0031] Figure 4 This is the charge and discharge curve diagram of Example 2. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the embodiments, but the present invention is not limited thereto.

[0033] Example 1

[0034] First, prepare a mixed positive electrode material by mixing sodium vanadium phosphate and iron-based Prussian blue in a ratio of 1:1.75, and then add an appropriate amount of NMP (N-methylpyrrolidone) to prepare a slurry with a ratio of 8:1:1 for the mixed positive electrode material: conductive agent (conductive carbon black): binder (polyvinylidene fluoride). After stirring for 2 to 3 hours, coat the prepared aluminum electrode sheet with one side polished with sandpaper. After drying overnight at 80°C in a vacuum drying oven, press the sheet. The pressed electrode sheet is vacuum dried at 80°C for at least 6 hours to obtain the positive electrode of the battery. Record the quality difference before and after the electrode sheet to calculate the active material parameters.

[0035] In a vacuum glove box, a sodium-potassium liquid alloy was prepared according to the mass ratio of potassium metal to sodium metal of 78:22. The sodium-potassium liquid alloy was adsorbed on a carbon cloth at 420° C. on a heating platform to obtain a negative electrode of a battery.

[0036] After obtaining the positive and negative electrodes of the battery, the battery is assembled in the order of positive electrode shell, positive electrode material, diaphragm, electrolyte, carbon cloth, gasket, and negative electrode shell. The electrolyte is a mixed electrolyte, and the ratio of the mixed electrolyte is the same as that of sodium vanadium phosphate: iron-based Prussian blue.

[0037] The preparation flow chart of the preparation method in Example 1 is as follows Figure 1 As shown in the figure, the XRD diagram of the sodium vanadium phosphate material prepared by the gel method is as follows Figure 2 shown.

[0038] Example 2

[0039] First, prepare a mixed positive electrode material by mixing sodium vanadium phosphate and iron-based Prussian blue in a calculated ratio of sodium vanadium phosphate: iron-based Prussian blue equal to 1:1, and then add an appropriate amount of NMP (N-methylpyrrolidone) to prepare a slurry with a mixed positive electrode material: conductive agent (conductive carbon black): binder (polyvinylidene fluoride) at a ratio of 8:1:1. After stirring for 2 to 3 hours, the prepared aluminum electrode sheet with one side polished with sandpaper is coated. After drying overnight at 80°C in a vacuum drying oven, the sheet is pressed. The pressed electrode sheet is vacuum dried at 80°C for at least 6 hours to obtain the positive electrode of the battery. Record the quality difference before and after the electrode sheet to calculate the active material parameters.

[0040] In a vacuum glove box, a sodium-potassium liquid alloy was prepared according to the mass ratio of potassium metal to sodium metal of 78:22. The sodium-potassium liquid alloy was adsorbed on a carbon cloth at 420° C. on a heating platform to obtain a negative electrode of a battery.

[0041] After obtaining the positive and negative electrodes of the battery, the battery is assembled in the order of positive electrode shell, positive electrode material, diaphragm, electrolyte, carbon cloth, gasket, and negative electrode shell. The electrolyte is a mixed electrolyte, and the ratio of the mixed electrolyte is the same as that of sodium vanadium phosphate: iron-based Prussian blue.

[0042] Example 3

[0043] First, prepare a mixed positive electrode material by mixing sodium vanadium phosphate and iron-based Prussian blue in a ratio of 1:1.5, and then add an appropriate amount of NMP (N-methylpyrrolidone) to prepare a slurry with a ratio of 8:1:1 for the mixed positive electrode material: conductive agent (conductive carbon black): binder (polyvinylidene fluoride). After stirring for 2 to 3 hours, coat the prepared aluminum electrode sheet with one side polished with sandpaper. After drying overnight at 80°C in a vacuum drying oven, press the sheet. The pressed sheet is vacuum dried at 80°C for at least 6 hours to obtain the positive electrode of the battery. Record the quality difference before and after the electrode sheet to calculate the active material parameters.

[0044] In a vacuum glove box, a sodium-potassium liquid alloy is prepared according to the mass of potassium metal and the mass of sodium metal of 78:22. The sodium-potassium liquid alloy is adsorbed on a carbon cloth at 420°C on a heating platform to obtain the negative electrode of the battery. After obtaining the positive and negative electrodes of the battery, the battery is assembled in the order of positive electrode shell, positive electrode material, diaphragm, electrolyte, carbon cloth, gasket, and negative electrode shell. The electrolyte is a mixed electrolyte, and the ratio of the mixed electrolyte is the same as that of sodium vanadium phosphate: iron-based Prussian blue.

[0045] Performance Testing

[0046] The sodium-potassium alloy mixed ion button cells assembled in Examples 1 to 3 were first placed on a blue-electricity tester for more than 12 hours and then charged at 20 mA·g -1 , 50mA·g -1 The electrochemical test was carried out by cycling 200 times at a current density of 1.5 V and a voltage upper and lower limit of 2.5 to 3.8 V.

[0047] Performance test results such as Figure 3 , 4 , at 20mA·g -1 At a current density of 30 mAh / g, it has a specific capacity of 30 mAh / g and good cycle stability.

[0048] This is because the sodium-potassium alloy hybrid battery with dual ion release can improve resource utilization, theoretically reaching 100%.

[0049] Therefore, a sodium vanadium phosphate and Prussian blue hybrid battery that can achieve potassium-sodium dual ion release has extremely high resource utilization and stability, and has far-reaching significance for achieving dual ion release in sodium-potassium alloy batteries.

Claims

1. A method for realizing the release of sodium-potassium dual ions from a battery using a positive electrode material mixed with a sodium-based positive electrode and a potassium-based positive electrode, characterized in that: The following steps are involved: 1) Mixing a potassium storage cathode material and a sodium storage cathode material in a certain ratio, that is, sodium vanadium phosphate: iron-based Prussian blue = 1:1.75, 1:1 or 1:1.5 to prepare a mixed cathode material; 2) After the mixed positive electrode material is mixed with the conductive agent and the binder in a certain proportion, a certain volume of organic solvent is added dropwise to prepare a mixed slurry, and the mixed slurry is applied on the current collector to obtain a mixed positive electrode sheet; 3) Match the positive electrode with a certain proportion of sodium-potassium alloy negative electrode, add mixed electrolyte to prepare a mixed ion full battery, the mass ratio of the alloy is potassium: sodium equal to 78:22, the mixed electrolyte refers to a mixture of sodium and potassium electrolytes, and the ratio of the mixed electrolyte is the same as the ratio of sodium vanadium phosphate: iron-based Prussian blue.

2. The method according to claim 1, characterized in that: The sodium storage positive electrode material described in step 1) is a positive electrode material that can only react with sodium ions but not potassium ions, and is sodium vanadium phosphate.

3. The method according to claim 1, characterized in that: The ratio of the conductive agent: the binder: the positive electrode material described in step 2) is 1:1:

8.

4. The method according to claim 1, characterized in that: The certain volume of organic solvent in step 2) is N-methylpyrrolidone.

5. The method according to claim 1, characterized in that: The mixed slurry described in step 2) is prepared by magnetic stirring for 2 to 3 hours.

6. The method according to claim 1, characterized in that: The certain proportion of sodium-potassium alloy described in step 3) is 78% by mass of potassium.

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