Nano sodium supplementing agent for sodium ion battery and preparation method of nano sodium supplementing agent

Abstract

The invention discloses a sodium ion battery nanometer sodium supplement agent, which comprises an organic micron sodium salt, a conductive material and deionized water, the mass ratio of the organic micron sodium salt is 0.5-1, the mass ratio of the conductive material is 0.01-0.5, the mass ratio of the deionized water is 5-20 times of the mass of the conductive material, and the particle size of the organic micron sodium salt is 200-500 microns. The nano sodium supplementing agent is excellent in performance, and the charge-discharge capacity, the first-circle coulombic efficiency and the cycle stability of the high-voltage sodium ion battery can be obviously improved.

Description

Technical Field

[0001] The present invention relates to the field of sodium supplements, and in particular to a nano sodium supplement for sodium ion batteries and a preparation method thereof. Background Art

[0002] The uneven distribution of global lithium resources and the widespread commercial application of lithium-ion batteries have pushed lithium prices to new peaks. Sodium, a member of the same main group metal, is widely and evenly distributed in the Earth's crust, making sodium-ion batteries, which share the same energy storage mechanism, a promising alternative to lithium-ion batteries. When volumetric and gravimetric energy density are not considerations, such as in large-scale stationary energy storage applications, the economic advantages of sodium-ion batteries will undoubtedly secure their place.

[0003] Sodium-ion batteries (SIBs) have attracted attention due to their low cost and wide availability of materials. Currently, the cathode materials for high-voltage SIBs with the best commercial prospects are primarily layered oxide SIBs. However, these SIBs exhibit low capacity, low first-cycle coulombic efficiency, and poor cycling stability. The addition of organic nano-sodium supplements can provide an additional sodium source to replenish the SIB's capacity and improve its first-cycle coulombic efficiency. Furthermore, the decomposition products of some SIBs contribute to the stability of the intermediate layer between the electrolyte and the electrode, thereby enhancing the SIB's cycling stability.

[0004] In current work, there are three main methods for pre-sodiumization of sodium-ion batteries. The first is to use a sodium sheet to directly contact the negative electrode of the sodium-ion battery to form an SEI film, and then use this negative electrode to assemble the battery to improve the capacity and coulombic efficiency of the sodium-ion battery. However, the sodium activity is relatively high, and this method cannot be widely used commercially. The second is inorganic metal sodium salt sodium supplements. This type of sodium supplement can appropriately improve the capacity of the sodium-ion battery, but a large amount of substances remain after decomposition, which reduces the mass density of the sodium-ion battery and cannot be used on a large scale in automotive sodium-ion batteries. The third is organic micron sodium salt sodium supplements. After decomposition, sodium is released in the form of ions. During the battery formation process, carbon and hydrogen in the organic matter are released in the form of gas, which has little effect on the mass density and volume density of the battery and is suitable for use in the field of automotive sodium-ion batteries. However, existing organic micron sodium salt sodium supplements have the disadvantage of poor conductivity. Summary of the Invention

[0005] To solve the above problems, the present invention aims to provide a nano sodium supplement for sodium ion batteries and a preparation method thereof. The nano sodium supplement has excellent performance and can significantly improve the charge and discharge capacity, first-cycle coulombic efficiency and cycle stability of high-voltage sodium ion batteries.

[0006] The present invention is achieved through the following technical solutions:

[0007] A nano sodium supplement for sodium ion batteries, comprising an organic micron sodium salt, a conductive material, and deionized water, wherein the mass ratio of the organic micron sodium salt is 0.5-1, the mass ratio of the conductive material is 0.01-0.5, the mass of the deionized water is 5-20 times that of the conductive material, and the particle size of the organic micron sodium salt is 200-500 microns.

[0008] Organic micron sodium salts include one or more of sodium formate, sodium butyrate, sodium propionate, sodium malonate, sodium butyrate, and sodium succinate; conductive materials include conductive carbon, Ketjen black, graphite, graphene, carbon nanotubes, C 60 One or more of .

[0009] A positive electrode sheet includes the aforementioned nano sodium supplement.

[0010] A method for preparing a nano-sodium supplement for sodium ion batteries is disclosed, wherein the preparation is performed by recrystallizing an organic micron sodium salt of a specific particle size, a conductive material, and deionized water. In the prior art, the organic micron sodium salt is first recrystallized alone to prepare a solid material, and then the conductive material is added to the solid material for processing to obtain the sodium supplement. The inventors employed a method for recrystallizing an organic micron sodium salt of a specific particle size, a conductive material, and deionized water together within a limited temperature range. During this process, the conductive agent provides ectopic nucleation sites for the recrystallization of the organic sodium salt of the specific particle size. The specific surface area of ​​the organic sodium salt of the specific particle size, together with the surface defects of the conductive agent, affects the nucleation rate of the nano-organic sodium salt. The selection of the particle size and the surface defects of the conductive agent balance each other's effects on the nucleation rate. The interaction between the organic sodium salt of the specific particle size and the conductive agent can steadily increase the nucleation rate, promote the rapid and stable nucleation of the organic sodium salt, and greatly slow the growth rate, thereby significantly reducing the particle size and obtaining a high-performance sodium supplement with excellent conductive properties. Scanning electron microscopy characterization of the sodium supplement prepared by the present invention shows that the grain size of the organic sodium salt adsorbed on the conductive material after recrystallization is on the order of tens of nanometers, and the particle morphology is petal-shaped.

[0011] A method for preparing a nano sodium supplement for sodium ion batteries comprises the following steps: dissolving an organic micron sodium salt and a conductive material in deionized water, ultrasonically mixing the mixture, and freeze-drying or drying the mixture at normal pressure to obtain the nano sodium supplement.

[0012] Another preparation method as described above is to dissolve the organic micron sodium salt and the conductive material in deionized water and mix them ultrasonically, then add alcohol to the mixed solution at a rate of 2 mL / min, the volume of the alcohol being 5-10 times the volume of the mixed solution, and then freeze-dry or dry at normal pressure to obtain the product.

[0013] Another preparation method as described above is to dissolve the organic micron sodium salt and the conductive material in deionized water, mix them uniformly with ultrasound, stir and heat them to form a gel, and then vacuum dry them.

[0014] The specific implementation methods are as follows:

[0015] Method 1

[0016] 1) According to the ratio of different components in the material, weigh an appropriate amount of conductive material and add it to a beaker, add an appropriate amount of deionized water to the beaker according to the volume ratio of deionized water to the conductive material 5-20 times, put it into a magnetic stirrer and stir for 0.1-10 hours, stir evenly and ultrasonicate at room temperature for 0.5-3 hours to ensure that the conductive material is fully dispersed in the deionized water. Ensure that the conductive material is fully dispersed in the deionized water. The organic micron sodium salt includes but is not limited to sodium formate, sodium butyrate, sodium propionate, sodium malonate, sodium butyrate, sodium succinate, and the conductive material includes but is not limited to conductive carbon, Ketjen black, graphite, graphene, carbon nanotubes, C 60 .

[0017] 2) Weigh an appropriate amount of organic micron sodium salt according to the ratio and add it to the mixed solution obtained in step 1). Ultrasonicate the mixed solution again at room temperature for 0.5-3 hours.

[0018] 3) The mixed solution obtained in step 2) is pre-cooled by adding liquid nitrogen and then placed in a freeze dryer for freeze drying at a temperature of -50-90°C and a pressure of 0.1 MPa until the mixed solution is fully dry. Alternatively, the mixed solution may be dried at 25-250°C under normal pressure.

[0019] Method 2

[0020] 1) According to the ratio of different components in the material, weigh an appropriate amount of conductive material and add it to a beaker. Add an appropriate amount of deionized water to the beaker at a volume ratio of 5-20 times that of the conductive material. Ultrasonicate at room temperature for 0.5-3 hours. Stir with a glass rod while ultrasonicating to ensure that the conductive material is fully dispersed in the deionized water. Organic micron sodium salts include but are not limited to sodium formate, sodium butyrate, sodium propionate, sodium malonate, sodium butyrate, sodium succinate, and conductive materials include but are not limited to conductive carbon, Ketjen black, graphite, graphene, carbon nanotubes, C 60 .

[0021] 2) Weigh an appropriate amount of organic micron sodium salt according to the ratio and add it to the mixed solution obtained in step 1). Ultrasonicate the mixed solution again at room temperature for 0.5-3 hours.

[0022] 3) Add 5-20 times the volume of alcohol into the mixed solution obtained in step 2) using a peristaltic pump at a rate of 2 mL / min.

[0023] 4) Pre-cool the mixed solution obtained in step 3) by adding liquid nitrogen and then freeze-dry it in a freeze dryer at a temperature of -50-90°C and a pressure of 0.1 MPa until the mixed solution is fully dry. Alternatively, dry it at 25-250°C under normal pressure.

[0024] Method 3

[0025] 1) According to the ratio of different components in the material, weigh an appropriate amount of conductive material and add it to a beaker. Add an appropriate amount of deionized water to the beaker at a volume ratio of 5-20 times that of the conductive material. Place it in a magnetic stirrer and stir for 0.1-10 hours. After stirring evenly, ultrasonicate at room temperature for 0.5-3 hours to ensure that the conductive material is fully dispersed in the deionized water. The organic micron sodium salt includes but is not limited to sodium formate, sodium butyrate, sodium propionate, sodium malonate, sodium butyrate, sodium succinate, and the conductive material includes but is not limited to conductive carbon, Ketjen black, graphite, graphene, carbon nanotubes, C 60 .

[0026] 2) Weigh an appropriate amount of organic micron sodium salt according to the ratio and add it to the mixed solution obtained in step 1). Ultrasonicate the mixed solution again at room temperature for 0.5-3 hours.

[0027] 3) The mixed solution obtained in step 2) is pre-cooled by adding liquid nitrogen and then placed in a freeze dryer for freeze drying at a temperature of -50-90°C and a pressure of 0.1 MPa until the mixed solution is fully dried. Alternatively, the mixed solution may be dried at 25-250°C under normal pressure.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) The sodium supplement prepared by the present invention has a wide range of adaptability and can be adapted to both low-voltage positive electrodes and high-voltage positive electrodes.

[0030] Selective.

[0031] (2) The method adopted by the present invention has strong controllability. The sodium supplement obtained by recrystallization of an organic micron sodium salt with an initial particle size of 200-500 microns, a conductive material and deionized water is characterized in that the organic micron sodium salt adsorbed on the conductive material is at the level of tens of nanometers, thereby improving the capacity and coulombic efficiency of the sodium ion battery, having little effect on the mass density or volume density of the battery, having a simple preparation process and good air stability.

[0032] (3) The organic nano sodium supplement prepared by the present invention has excellent performance and can significantly improve the charge and discharge capacity, first-cycle coulomb efficiency, and cycle stability of high-voltage sodium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0034] Figure 1 In Example 1 of the present invention, NaMn 0.33 Fe 0.33 Ni 0.33 O2 is used as the positive electrode material, and 5% nano-sodium formate mixed material is added, and the 1C rate stability cycle diagram.

[0035] Figure 2 In Example 2 of the present invention, Na 0.83 Ni 0.4 Mn 0.3 Fe 0.2 Zn 0.1 O2 is used as the positive electrode material, and 5% nano-sodium malonate is added to the mixed material at 1C rate stability cycle diagram.

[0036] Figure 3 In Example 3 of the present invention, Na 0.83 Ni 0.4 Mn 0.3 Fe 0.2 Zn 0.1 O2 is used as the positive electrode material, and 5% nano-sodium formate is added to the mixed material at 1C rate stability cycle diagram.

[0037] Figure 4 This is an SEM image of sodium formate adsorbed on Ketjen black conductive carbon in Example 1 of the present invention.

[0038] Figure 5 This is an SEM image of sodium formate adsorbed on carbon nanotube conductive carbon in Example 4 of the present invention.

[0039] Figure 6 1 and 2 are XRD patterns of sodium formate adsorbed on Ketjen black conductive carbon in Examples 1 and 2 of the present invention.

[0040] Figure 7 In comparative example 1 of the present invention, NaMn 0.33 Fe 0.33 Ni 0.33 O2 is the positive electrode material, 5% sodium formate is added, and the 1C rate stability cycle diagram.

[0041] Figure 8 In comparative example 2 of the present invention, Na 0.83 Ni 0.4 Mn 0.3 Fe 0.2 Zn 0.1 1C rate stability cycle diagram with O2 as the positive electrode material and 5% sodium malonate added.

[0042] Figure 9 For the comparative example 3 of the present invention, Na 0.83 Ni 0.4 Mn 0.3 Fe 0.2 Zn 0.1 1C rate stability cycle diagram with O2 as the positive electrode material and 5% sodium formate added.

[0043] Figure 10 This is the XRD pattern of sodium formate in Comparative Example 1 of the present invention.

[0044] Figure 11 This is the SEM image of sodium formate in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0046] Example 1 Nano-sodium formate (Ketjen Black) composite sodium supplement

[0047] 1) According to the ratio of the different components in the material, weigh 0.1g of Ketjen Black conductive material and add it to a beaker. Add an appropriate amount of deionized water to the beaker, with the volume ratio of deionized water to the conductive material being 20 times that of the conductive material. Place the beaker in a magnetic stirrer and stir for 6 hours. After stirring evenly, ultrasonicate at room temperature for 2 hours to ensure that the conductive material is fully dispersed in the deionized water. Ensure that the conductive material is fully dispersed in the deionized water.

[0048] 2) Weigh 0.5 g of sodium formate with a particle size of 200 μm and add it to the mixed solution obtained in step 1). Sonicate the mixed solution again at room temperature for 3 h.

[0049] 3) The mixed solution obtained in step 2) was placed on a magnetic heating stirring device and stirred at a speed of 300 r / min and a temperature of 300° C. until the solution became gel-like and then transferred to a vacuum oven for drying.

[0050] Example 2

[0051] Similar to Example 1, the difference is that 0.3 g of Ketjen black and 0.6 g of organic micron sodium salt sodium malonate with a particle size of 300 μm are weighed as the conductive material.

[0052] The only difference from Example 1 is that the organic micron sodium salt is sodium malonate and the positive electrode material is Na 0.83 Ni 0.4 Mn 0.3 Fe 0.2 Zn 0.1O2, a premixed powder of the positive electrode material, conductive carbon, and nano-sodium malonate (Ketjen Black) was uniformly mixed in proportion, applied and cut into electrode sheets. A coin cell battery was assembled using the material prepared in this example as the positive electrode, sodium metal as the negative electrode, glass fiber as the separator, and a 1M NaClO4 solution in PC / FEC (95:5 wt%) as the electrolyte. Charge and discharge tests were conducted in the rate mode over a voltage range of 2-4.2 V. The first-cycle charge capacity was 293.92 mAh / g, and the first-cycle discharge capacity was 152.45 mAh / g.

[0053] Example 3 Preparation of freeze-dried nano sodium formate (graphene) sodium supplement

[0054] 1) According to the ratio of different components in the material, weigh 0.5g of graphene and add it to a beaker. Add an appropriate amount of deionized water to the beaker at a volume ratio of 10 times that of the conductive material. Place the beaker in a magnetic stirrer and stir for 6 hours. After stirring evenly, ultrasonicate at room temperature for 3 hours to ensure that the conductive material is fully dispersed in the deionized water.

[0055] 2) Weigh 1 g of organic micronized sodium formate with a particle size of 500 μm and add it to the mixed solution obtained in step 1). Sonicate the mixed solution again at room temperature for 3 h.

[0056] 3) Pre-cool the mixed solution obtained in step 2) by adding liquid nitrogen and then freeze-dry it in a freeze dryer at a temperature of -70°C and a pressure of 0.1 MPa until the mixed solution is fully dry. Alternatively, dry it at 25-250°C under normal pressure.

[0057] Example 4

[0058] Similar to Example 1, the difference is that 0.1 g of carbon nanotubes and 0.5 g of organic micron sodium salt sodium malonate with a particle size of 300 μm are weighed as the conductive material.

[0059] Comparative Example 1

[0060] Similar to Example 1, the difference is that 0.1 g of Ketjen black and 0.5 g of sodium formate (particle size 600 μm) are weighed as the conductive material.

[0061] Comparative Example 2

[0062] Similar to Example 2, except that 0.3 g of Ketjen black and 0.6 g of sodium malonate (particle size 600 μm) were weighed as the conductive material.

[0063] Comparative Example 3

[0064] Similar to Example 2, except that 0.3 g of Ketjen black and 0.6 g of sodium malonate with a particle size of 150 μm were weighed as the conductive material.

[0065] Comparative Example 4

[0066] Similar to Example 2, except that 0.6 g of micronized sodium malonate with a particle size of 300 μm is first recrystallized to obtain a solid material, and then 0.3 g of Ketjen Black is mixed with the solid material to obtain the obtained product.

[0067] 2. Extensive Experiment on the Selection of Sodium Supplements

[0068] The sodium supplement of Example 1 was combined with different positive electrode materials to prepare batteries, and discharge tests were performed.

[0069] The positive electrode material, the nano sodium formate (Ketjen Black) composite material prepared in Example 1, was used as a sodium supplement, metallic sodium was used as the negative electrode, glass fiber was used as the separator, and a 1M NaClO4 PC / FEC (95:5wt%) solution was used as the electrolyte. A button cell was assembled with a voltage range of 2-4 V. The charge and discharge test was performed in rate mode. The results are shown in Table 1 below:

[0070] Table 1

[0071] cathode materials Voltage range First cycle charging capacity / mAh / g First cycle discharge capacity / mAh / g <![CDATA[NaMn 0.33 Want 0.33 In 0.33 O2]]> 2-4 V 152.85 118.25 <![CDATA[NaMn 0.4 Fe 0.3 Ni 0.2 Zn 0.1 O2]]> 2-4 V 293.92 152.45 <![CDATA[Na 0.83 Ni 0.4 Mn 0.3 Fe 0.2 Zn 0.1 O2]]> 2-4 V 197.02 124.20 <![CDATA[Na 0.83 Ni 0.4 Mn 0.3 Fe 0.2 Zn 0.1 O2]]> 2-4 V 205.03 123.10

[0072] It can be seen from the above selective experiments that the adaptable voltage range of the battery prepared by the sodium supplement prepared by the present invention is 2-4V.

[0073] III. Discharge Test of Button Batteries Prepared in Examples 1-4 and Comparative Examples

[0074] The sodium supplements of Examples 1-4 and Comparative Examples, NaMn 0.33 Fe 0.33 Ni 0.33 O2 positive electrode material, sodium metal as the negative electrode, glass fiber as the separator, 1M NaClO4 PC / FEC (95:5wt%, 0.5g sodium supplement, 0.95g positive electrode material) solution as the electrolyte, assembled button cells, and selected the rate mode for charge and discharge tests. The results are shown in Table 2:

[0075] Table 2

[0076] sample Voltage range First cycle charging capacity / mAh / g First cycle discharge capacity / mAh / g Example 1 2-4 V 152.85 118.25 Example 2 2-4 V 293.92 152.45 Example 3 2-4 V 197.02 124.20 Example 4 2-4 V 205.03 123.10 Comparative Example 1 2-4 V 137.85 117.13 Comparative Example 2 2-4 V 117.39 102.61 Comparative Example 3 2-4 V 129.24 97.71 Comparative Example 3 2-4 V 118.34 110.64

[0077] As can be seen from Table 1, the first-cycle charge and discharge capacity of Examples 1-4 is significantly superior to that of Comparative Examples 1-3. Comparison between Examples 1-3 shows that the best performance is achieved when 5% nano sodium malonate (Ketjen Black) sodium supplement is added. Comparison between Examples 1-3 and Comparative Examples 1-3 shows that the nanostructured sodium supplement can significantly improve the first-cycle charge and discharge capacity of the sodium ion battery compared to conventional sodium supplements during the pre-sodium treatment. By comparing Implementation Case 1 and Implementation Case 2, it can be concluded that the increase in the proportion of sodium content in the pre-sodium treatment has a significant effect on the pre-sodium treatment of the sodium ion battery. By comparing different drying methods, it can be concluded that freeze-drying has its unique advantages.

[0078] It can be seen from the electron microscope photos that the particle size of the sodium supplement after recrystallization is significantly smaller than that of the non-recrystallized sodium supplement. The XRD data proves that the unconverted sodium supplement after recrystallization is not limited to other products.

[0079] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A nano sodium supplement for sodium ion batteries, characterized in that: Its formula includes organic micron sodium salt, conductive material and deionized water, wherein the mass ratio of organic micron sodium salt is 0.5-1, the mass ratio of conductive material is 0.01-0.5, the mass of deionized water is 5-20 times the mass of conductive material, and the particle size of organic micron sodium salt is 200-500 microns.

2. A sodium ion battery nano sodium supplement according to claim 1, characterized in that Organic micron sodium salts include one or more of sodium formate, sodium butyrate, sodium propionate, sodium malonate, sodium butyrate, and sodium succinate; conductive materials include conductive carbon, Ketjen black, graphite, graphene, carbon nanotubes, C 60 One or more of .

3. The method for preparing a nano sodium supplement for sodium ion batteries according to claim 1 or 2, wherein: First, the conductive material is put into deionized water and mixed to obtain a first mixed solution, and then the organic micron sodium salt is added to the first mixed solution and recrystallized together to obtain a first mixed solution, wherein the particle size of the organic micron sodium salt is 200-500 microns.

4. The method for preparing a nano sodium supplement for sodium ion batteries according to claim 3, wherein: The organic micron sodium salt and the conductive material are respectively dissolved in deionized water and ultrasonically mixed evenly, and then freeze-dried or dried at normal pressure to obtain the product.

5. The method for preparing a nano sodium supplement for sodium ion batteries according to claim 3, wherein: The organic micron sodium salt and the conductive material are respectively dissolved in deionized water and ultrasonically mixed, and then alcohol is dripped into the mixed solution at a rate of 2 mL / min. The volume of the alcohol is 5-10 times the volume of the mixed solution, and then freeze-dried or dried at normal pressure to obtain the product.

6. The method for preparing a nano sodium supplement for sodium ion batteries according to claim 3, wherein: The organic micron sodium salt and the conductive material are respectively dissolved in deionized water, ultrasonically mixed, stirred and heated to form a gel, and vacuum dried to obtain the gel.

7. An electrode plate, comprising a positive electrode material and conductive carbon, characterized in that: Also included is the nano sodium supplement according to claim 1 or 2.

8. A battery, characterized in that: Comprising the electrode plate as described in claim 6.

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