A composite cathode material applied to a sodium ion battery and a preparation method thereof

Abstract

The application discloses a composite positive electrode material applied to a sodium ion battery and a preparation method thereof, which is obtained through one-step reaction sintering of five phases of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate and manganese dioxide by a planetary ball mill, drying, sieving and calcining. The composite positive electrode material can obtain two phases through a precursor one-step method, the product is more uniform, the operation is simple and easy to implement, the time consumption is short, the method is economic and environment-friendly, and is beneficial to industrialized production. The composite material can be applied to a sodium ion battery, and the cycle stability of the composite material is better than that of a pure phase Na 0.7 MnO 2.05 .

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and specifically to a composite cathode material for sodium-ion batteries and its preparation method. Background Technology

[0002] my country's energy production and consumption are primarily coal-based, supplemented by other energy sources such as natural gas, hydropower, nuclear power, and other power generation methods. However, the continuous consumption of non-renewable energy and increasing human concern for the environment urgently require optimization of my country's energy structure, especially accelerating the replacement of traditional energy sources with new energy sources. Electrochemical energy storage, compared to other energy storage technologies, offers large capacity and fast response. Currently, lithium-ion batteries are the most widely used, with applications in computers, communications, and consumer electronics. However, with the production of new energy vehicles and the construction of advanced energy storage devices in recent years, although lithium-ion batteries have higher specific capacity and energy density, their high cost is due to the uneven global distribution and decreasing reserves of the raw materials used (Li, Co, etc.), and the immature resource recycling technology. In contrast, sodium, as a group-agent element, has a similar charging and discharging principle to lithium-ion batteries, but sodium is abundant in my country. Under the premise of ensuring safety and cycle life, its cost has a significant advantage, making it particularly suitable for static energy storage devices to improve stable power supply.

[0003] Currently, cathode materials for sodium-ion batteries include layered transition metal oxides, polyanionic compounds such as phosphates, pyrophosphates, and fluorophosphates, and sulfides and other cathode materials including Prussian blue, organic compounds, and tunnel-type transition metal oxides. Among these, layered transition metal oxides have higher theoretical specific capacity, but their cycle stability is also seriously challenged. Manganese-based cathode materials are non-toxic and lower in cost, among which Na... 0.7 MnO 2.05 The preparation of this material often involves time-consuming and labor-intensive methods such as hydrothermal, solvothermal, and sol-gel methods, which not only result in complex preparation processes but also relatively poor electrochemical performance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies. To address the problems of complex preparation processes and poor cycle stability in existing technologies, this invention provides a composite cathode material for sodium-ion batteries and its preparation method. This composite cathode material exhibits good cycle stability and rate performance. Furthermore, the preparation method for the cathode material is simple and inexpensive, which will be highly beneficial to the development of advanced energy storage devices and the development of new energy sources.

[0005] The technical objective of this invention is achieved through the following technical solution.

[0006] A composite cathode material for sodium-ion batteries and its preparation method are disclosed, comprising the following steps: Step 1: Mix sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, manganese dioxide, and anhydrous ethanol (as dispersion solvent) thoroughly and then ball-mill. The ratio of the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide to the mass of the grinding ball is (1-1.1):8; with the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide being 100wt%, the mass percentage of NaMnO2 being 50-70wt%, and Na3Zr2Si2PO4 being... 12 The mass percentage is 30-50%, based on which the amount of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate and manganese dioxide used is calculated; In step 1, the ratio of the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide to the mass of the grinding ball is (1.07-1.1):8.

[0007] In step 1, ball milling is performed using zirconium dioxide balls and a grinding jar.

[0008] In step 1, the silicon dioxide particles have a size of 7-40 nm, and the zirconium dioxide particles have a size of 50 nm.

[0009] In step 1, the ball milling speed is 200~220 r / min, and the ball milling time is 10~12 h.

[0010] Step 2: Dry the precursor dispersion (i.e., precursor solution) obtained in Step 1; In step 2, the precursor dispersion (i.e., precursor solution) obtained in step 1 is poured into a petri dish and dried by air drying at a temperature of 100~120℃ for 10~12h.

[0011] Step 3: Grind and sieve the powder dried in Step 2 to obtain uniform particles; In step 3, the sieve mesh size is 100 mesh.

[0012] Step 4: Sinter the powder obtained in Step 3 by heating it in air from room temperature (20-25 degrees Celsius) to 950±5 °C. o C, heating rate is 3-5 o The temperature was set at 10°C / min, and the holding time was 10-12 hours, followed by natural cooling to obtain a composite cathode material containing Na. 0.7 MnO 2.05 and Na4Zr2Si3O 12 .

[0013] In step 4, the powder is poured into a crucible and sintered using a muffle furnace.

[0014] In step 4, the temperature is increased from room temperature (20-25 degrees Celsius) to 950 degrees Celsius in an air atmosphere. o C, heating rate is 3-5 o The composite cathode material was obtained by holding the material at a temperature of 10°C / min for 10 hours and then allowing it to cool naturally.

[0015] In the above technical solution, the planetary ball mill model is YXQM-0.4L, and the zirconia balls are of three sizes: large, medium, and small, with a mass ratio of 1:5:14. The diameters of the three types of balls are 10.88±0.30mm, 8.45±0.30mm, and 5.47±0.30mm, respectively, and the masses of the three types of balls are 4.12±0.10g, 2.13±0.10g, and 0.41±0.10g, respectively.

[0016] The composite cathode material of the present invention is used as a cathode material in sodium-ion batteries.

[0017] Compared with existing technologies, the composite cathode material of this invention, compared with pure Na, 0.7 MnO 2.05 In general, the stability of the battery is improved; this patent discloses a composite cathode material for sodium-ion batteries and its preparation method, which prepares Na through a one-step solid-state method. 0.7 MnO 2.05 and Na4Zr2Si3O 12 Na4Zr2Si3O 12 As an ionic conductor, it can facilitate the rapid transport of sodium ions in the positive electrode and improve its cycle stability.

[0018] This invention employs a one-step solid-state method to prepare cathode materials. Compared with traditional cathode preparation methods such as hydrothermal, solvothermal, and sol-gel methods, the one-step solid-state method produces materials with uniform particle size, and the slurry mixing is more uniform than mixing two phases separately. Furthermore, this method is simple and easy to implement, greatly simplifying the preparation process and reducing operation time, thus improving cost-effectiveness. This is beneficial for the development of sodium-ion batteries for advanced energy storage devices and the development of new energy sources. Attached Figure Description

[0019] Figure 1 These are the XRD patterns of Embodiments 1 and 2 of the present invention.

[0020] Figure 2 This is the XRD spectrum of Embodiment 3 of the present invention.

[0021] Figure 3 This is a SEM image of Embodiment 3 of the present invention.

[0022] Figure 4 This is the cyclic voltammetry curve of Embodiment 3 of the present invention.

[0023] Figure 5 These are charge-discharge curves at different rates in Embodiment 3 of the present invention.

[0024] Figure 6 This is the coulombic efficiency diagram of charging and discharging at 0.2C in Embodiment 3 of the present invention. Detailed Implementation

[0025] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. The sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide used in the embodiments are all powders with a purity of not less than 99%, and anhydrous ethanol is used as the solvent. The planetary ball mill model is YXQM-0.4L, and three types of zirconium dioxide balls are used, large, medium, and small, in a mass ratio of 1:5:14. The diameters of the three types of balls are 10.88±0.30mm, 8.45±0.30mm, and 5.47±0.30mm, respectively. The masses of the three types of balls are 4.12±0.10g, 2.13±0.10g, and 0.41±0.10g, respectively. Different specifications of grinding balls are selected in each set of embodiments, with a total mass of 60g of zirconium dioxide balls and 40mL of anhydrous ethanol.

[0026] Example 1 (1) Calculate the mass of the powder to be ball-milled based on the total mass of the zirconium dioxide balls and the proportional relationship. Then, take the mass of the powder as 100wt% and the mass percentage of NaMnO2 as x=70wt%. Calculate the amount of Na and Mn provided based on this. Weigh 2.2301g of Na2CO3 and 3.6890g of MnO2 and pour them into the ball mill jar containing anhydrous ethanol and zirconium dioxide balls. (2) According to Na3Zr2Si2PO 12 The mass percentage is x = 30wt%. Based on this, the amount of Zr, Si and P to be provided is calculated. The masses of Na3PO4, ZrO2 and SiO2 are weighed as 0.6176g, 0.9192g and 0.4491g respectively, and poured into a ball mill jar containing Na2CO3, MnO2, anhydrous ethanol and zirconium dioxide balls. (3) Place the ball milling jar from (2) into a planetary ball mill and mill at a speed of 200 revolutions per minute for 12 hours; (4) Slowly pour the solution from (3) into a petri dish and place it in a forced-air drying oven to dry at 100 degrees Celsius for 12 hours; (5) Pour the dried powder from (4) into a mortar and grind it through a 100-mesh sieve to obtain uniform particles; (6) Take the precursor powder and transfer it to a muffle furnace. Under an air atmosphere, the powder in the crucible is heated from room temperature (20-25 degrees Celsius) to 950 °C in the muffle furnace. o C, heating rate is 4 oC The temperature was maintained at a constant rate of 10 min for 10 hours, and then naturally cooled to obtain the composite cathode material.

[0027] The composite cathode material prepared above was characterized by X-ray diffraction (XRD). When Na3Zr2Si2PO4 was used... 12 When the mass percentage is x=30wt%, XRD analysis revealed the formation of terminal NASICON (sodium ion ultrafast conductor Na) at x=3. 1+ x Zr2Si x P 3-x O 12 (0≤x≤3))Na4Zr2Si3O 12 and active material Na 0.70 MnO 2.05 (Two target products have been produced), therefore the material possesses certain ionic and electronic conductivity, such as Figure 1 As shown, a small amount of Na is also present. 0.91 MnO2, Na2ZrSiO5, Na3PO4 and ZrO2.

[0028] Example 2 (1) According to the mass percentage of NaMnO2 being x=60wt%, weigh 1.8584g of Na2CO3 and 3.0742g of MnO2, and pour them into a ball mill jar containing anhydrous ethanol and zirconium dioxide balls. (2) According to Na3Zr2Si2PO 12 With a mass percentage of x = 40 wt%, weigh 0.8007 g of Na3PO4, 1.1917 g of ZrO2 and 0.5823 g of SiO2, and pour them into a ball mill jar containing Na2CO3, MnO2, anhydrous ethanol and zirconium dioxide balls. (3) Place the ball milling jar from (2) into a planetary ball mill and mill at a speed of 220 revolutions per minute for 8 hours; (4) Slowly pour the solution from (3) into a petri dish and place it in a forced-air drying oven to dry at 120 degrees Celsius for 10 hours; (5) Pour the dried powder from (4) into a mortar and grind it through a 100-mesh sieve to obtain uniform particles; (6) Take the precursor powder and transfer it to a muffle furnace. Under an air atmosphere, the powder in the crucible is heated from room temperature (20-25 degrees Celsius) to 950 °C in the muffle furnace. oC, heating rate of 4°C / min, holding time of 10h, and natural cooling are used to obtain composite cathode material; The composite cathode material prepared above was characterized by X-ray diffraction (XRD). When Na3Zr2Si2PO4 was used... 12 When the mass percentage is x=40wt%, XRD analysis revealed the formation of terminal NASICON (sodium ion ultrafast conductor Na) at x=3. 1+ x Zr2Si x P 3-x O 12 (0≤x≤3))Na4Zr2Si3O 12 and active material Na 0.70 MnO 2.05 (Two target products have been produced), therefore the material possesses certain ionic and electronic conductivity, such as Figure 1 As shown, a small amount of Na is also present. 0.91 MnO2, Na2ZrSiO5, Na3PO4 and ZrO2.

[0029] Example 3 Preparation of composite cathode materials: (1) According to the mass percentage of NaMnO2 being x=50wt%, weigh 1.5930g of Na2CO3 and 2.6350g of MnO2, and pour them into a ball mill jar containing anhydrous ethanol and zirconium dioxide balls. (2) According to Na3Zr2Si2PO 12 With a mass percentage of x = 50 wt%, weigh 1.0298 g of Na3PO4, 1.5328 g of ZrO2, and 0.7489 g of SiO2, and pour them into a ball mill jar containing Na2CO3, MnO2, anhydrous ethanol, and zirconium dioxide balls. (3) Place the ball milling jar from (2) into a planetary ball mill and mill at a speed of 220 revolutions per minute for 10 hours; (4) Slowly pour the solution from (3) into a petri dish and place it in a forced-air drying oven to dry at 120 degrees Celsius for 10 hours; (5) Pour the dried powder from (4) into a mortar and grind it, then sieve it through a 100-mesh sieve to obtain uniform particles; (6) Take the precursor powder and transfer it to a muffle furnace. Under an air atmosphere, the powder in the crucible is heated from room temperature (20-25 degrees Celsius) to 950 °C in the muffle furnace. o C, heating rate is 4 o The composite cathode material was obtained by holding the material at a temperature of 10°C / min for 10 hours and then allowing it to cool naturally.

[0030] Battery manufacturing methods: Positive electrode preparation: Take the synthesized composite positive electrode material, mix and grind 80wt% of positive electrode active material, 10wt% of conductive carbon black, and 10wt% of polyvinylidene fluoride (PVDF), and uniformly disperse them in N-methyl-2-pyrrolidone (NMP) to prepare a mixed slurry. Then, coat the slurry onto the current collector aluminum foil, dry it in a forced-air drying oven at 110℃ for 2-5 hours, and then dry it in a vacuum drying oven at 120℃ for 12 hours. Cut it into round pieces with a diameter of 12mm using a cutting clamp.

[0031] Battery assembly: Assembly was carried out in a glove box filled with argon atmosphere. A sodium sheet was used as the counter electrode. The cut sodium sheet was rolled into a thin sheet using a rolling pin, and a 0.9 cm sodium sheet was punched out using a punch. A 1M NaClO4 solution (solvent EC:DMC volume ratio 1:1 and 5% FEC) was used as the electrolyte. Glass fiber (Whatman) TM GF / D) is used as the separator; the coin cell model is CR2032.

[0032] Performance testing: X-ray diffraction (XRD) characterization: When Na3Zr2Si2PO 12 When the mass percentage is x=50wt%, XRD analysis revealed the formation of terminal NASICON (sodium ion ultrafast conductor Na) at x=3. 1+x Zr2Si x P 3-x O 12 (0≤x≤3))Na4Zr2Si3O 12 and active material Na 0.70 MnO 2.05 ,like Figure 2 Therefore, the material possesses certain ionic and electronic conductivity. In addition, small amounts of residual Na3PO4 and ZrO2 are also present.

[0033] Scanning electron microscopy (SEM) characterization: Figure 3 The image shown is a SEM image of the composite cathode material. It can be clearly seen from the image that the sample morphology consists of primary particles formed by the agglomeration of secondary particles.

[0034] Electrochemical testing: Cyclic voltammetry (CV) curves of the half-cell were measured at 25℃ using a CHI 760E electrochemical workstation (Shanghai Chenhua equipment). The sodium ion insertion / extraction process in the prepared sample was studied using cyclic voltammetry (CV) at a scan rate of 0.1 mV s between 2.0 and 4.3 V. −1 The following will proceed. (As...) Figure 4 Typically, the anodic / cathode peaks at 2.6 / 2.2 V correspond to Mn. 3+ / Mn 4+The redox reaction, with high-voltage peaks of 4.3 V / 4.2 V, represents the transition from the P2 to the O3 phase. Generally speaking, the sharp peaks and broad peaks represent the two-phase transition and single-phase evolution of sodium ion insertion / extraction, respectively, representing a complex multiphase transition process. To avoid excessive volume expansion and severe irreversible capacity loss due to the P2-O3 phase transition caused by the high-voltage peaks, the cutoff voltage during charge / discharge testing was set to 3.8 V. Figure 5 As shown, when charged and discharged using the Land CT3002A battery testing system at a rate of 0.2C within the range of 2–3.8V, its initial discharge capacity was 155.9 mAh g. -1 This demonstrates excellent sodium storage performance. For example... Figure 6 As shown, after cycling at 0.2C, 0.5C, 1C, 2C, and 5C at 25℃, and then undergoing charge-discharge testing at 0.2C in the 2–3.8V range, the discharge specific capacity after 100 cycles is 80.8 mAh g. -1 The capacity retention rate was 57.4%, demonstrating a higher efficiency than that of pure-phase Na, which has a more complex preparation process. 0.70 MnO 2.05 Better cycle stability.

[0035] Adjustments to the preparation process based on the content of this invention can achieve the preparation of composite cathode materials, exhibiting performance substantially consistent with that of this invention. The invention has been described above as exemplary. It should be noted that any simple modifications, alterations, or equivalent substitutions that can be made by those skilled in the art without creative effort, without departing from the core of this invention, fall within the protection scope of this invention.

Claims

1. A composite cathode material for use in sodium-ion batteries, characterized in that, Follow these steps: Step 1: Mix sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, manganese dioxide, and anhydrous ethanol evenly and then ball-mill them, wherein: The ratio of the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide to the mass of the grinding ball is (1-1.1):8; with the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide being 100wt%, the mass percentage of NaMnO2 being 50-70wt%, and Na3Zr2Si2PO4 being... 12 The mass percentage is 30-50%, based on which the amount of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate and manganese dioxide used is calculated; Step 2: Dry the precursor dispersion obtained in Step 1; Step 3: Grind and sieve the powder dried in Step 2 to obtain uniform particles; Step 4: Sinter the powder obtained in Step 3 by heating it in air from room temperature (20-25 degrees Celsius) to 950±5 °C. o C, heating rate is 3-5 o The temperature was set at 10°C / min, and the holding time was 10-12 hours, followed by natural cooling to obtain a composite cathode material containing Na. 0.7 MnO 2.05 and Na4Zr2Si3O 12 .

2. The composite cathode material for sodium-ion batteries according to claim 1, characterized in that, In step 1, the ratio of the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide to the mass of the grinding balls is (1.07-1.1):8; the particle size of silicon dioxide is 7-40 nm, and the particle size of zirconium dioxide is 50 nm; ball milling is performed using zirconium dioxide balls and a ball milling jar, the ball milling speed is 200-220 r / min, and the ball milling time is 10-12 h.

3. The composite cathode material for sodium-ion batteries according to claim 1, characterized in that, In step 2, the precursor dispersion obtained in step 1 is poured into a petri dish and dried by air drying at a temperature of 100~120℃ for 10~12h; in step 3, it is sieved through a 100-mesh sieve.

4. The composite cathode material for sodium-ion batteries according to claim 1, characterized in that, In step 4, the temperature is increased from room temperature (20-25 degrees Celsius) to 950 degrees Celsius in an air atmosphere. o C, heating rate is 3-5 o The composite cathode material was obtained by holding the material at a temperature of 10°C / min for 10 hours and then allowing it to cool naturally.

5. The application of the composite cathode material as described in any one of claims 1-4 as a cathode material in sodium-ion batteries.

6. A method for preparing a composite cathode material for sodium-ion batteries, characterized in that, Follow these steps: Step 1: Mix sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, manganese dioxide, and anhydrous ethanol evenly and then ball-mill them, wherein: The ratio of the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide to the mass of the grinding ball is (1-1.1):8; with the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide being 100wt%, the mass percentage of NaMnO2 being 50-70wt%, and Na3Zr2Si2PO4 being... 12 The mass percentage is 30-50%, based on which the amount of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate and manganese dioxide used is calculated; Step 2: Dry the precursor dispersion obtained in Step 1; Step 3: Grind and sieve the powder dried in Step 2 to obtain uniform particles; Step 4: Sinter the powder obtained in Step 3 by heating it in air from room temperature (20-25 degrees Celsius) to 950±5 °C. o C, heating rate is 3-5 o The temperature was set at 10°C / min, and the holding time was 10-12 hours, followed by natural cooling to obtain a composite cathode material containing Na. 0.7 MnO 2.05 and Na4Zr2Si3O 12 .

7. The method for preparing a composite cathode material for sodium-ion batteries according to claim 6, characterized in that, In step 1, the ratio of the sum of the masses of sodium phosphate, zirconium dioxide, silicon dioxide, sodium carbonate, and manganese dioxide to the mass of the grinding ball is (1.07-1.1):8; the silicon dioxide particle size is 7-40 nm, and the zirconium dioxide particle size is 50 nm.

8. The method for preparing a composite cathode material for sodium-ion batteries according to claim 6, characterized in that, In step 1, the planetary ball mill model is YXQM-0.4L. Three types of zirconia balls are used, large, medium and small, with a mass ratio of 1:5:

14. The diameters of the three types of balls are 10.88±0.30mm, 8.45±0.30mm and 5.47±0.30mm, respectively, and the masses of the three types of balls are 4.12±0.10g, 2.13±0.10g and 0.41±0.10g, respectively. The ball milling is carried out using zirconia balls and a ball milling jar, with a ball milling speed of 200~220r / min and a ball milling time of 10~12h.

9. A method for preparing a composite cathode material for sodium-ion batteries according to claim 6, characterized in that, In step 2, the precursor dispersion obtained in step 1 is poured into a petri dish and dried by air drying at a temperature of 100~120℃ for 10~12h; in step 3, it is sieved through a 100-mesh sieve.

10. A method for preparing a composite cathode material for sodium-ion batteries according to claim 6, characterized in that, In step 4, the powder is poured into a crucible and sintered in a muffle furnace, with the temperature increased from room temperature (20-25 degrees Celsius) to 950 degrees Celsius in an air atmosphere. o C, heating rate is 3-5 o The composite cathode material was obtained by holding the material at a temperature of 10°C / min for 10 hours and then allowing it to cool naturally.

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