A method for preparing a sodium-ion battery negative electrode material

Abstract

The application belongs to the technical field of batteries, and particularly relates to a preparation method of a sodium ion battery negative electrode material. x The surface of the product is modified by adding graphene (GO), so that the product is a composite nanomaterial of amorphous vanadium oxide and graphene, and the product is used as a negative electrode material of a sodium ion battery. The amorphous vanadium oxide and graphene composite material prepared by the method has excellent cycle stability, high rate performance, long service life and an environment-friendly simple preparation method, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically a method for preparing a negative electrode material for sodium-ion batteries. Background Technology

[0002] Sodium-ion batteries are expected to replace lithium-ion batteries in the future, but due to Na... + radius The large size of sodium-ion batteries leads to problems such as poor cycle stability, low specific capacity, and low diffusion coefficient. Therefore, finding ideal electrode materials is crucial for sodium-ion batteries to exhibit excellent electrochemical performance. Graphite is a commercial anode material for lithium-ion batteries, but it is not ideal as an anode material for sodium-ion batteries because of the large sodium content (Na₂O₃). + If the material is too large, it cannot be fully embedded within the graphite layer. Therefore, exploring suitable anode materials is of greater interest.

[0003] Vanadium is one of the rock-forming elements, abundant in the Earth's crust. Almost all vanadium compounds are multivalent, ranging from +2 to +5, which signifies the ability to perform multiple electron transfers and high capacity. This provides endless possibilities and choices for researching emerging electrode materials for sodium-ion batteries. Vanadium-based oxides have many advantages and can serve as a substitute for graphite. They are also one of the most promising electrode materials for next-generation advanced electrochemical energy storage technologies. However, using this electrode material as a negative electrode in sodium-ion batteries presents the following problems:

[0004] 1) Low electronic and ionic conductivity results in generally poor rate capability, which greatly affects large-scale applications;

[0005] 2) The material aggregates and pulverizes during charging and discharging, resulting in large volume changes that affect the cycle stability of the battery. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a method for preparing a sodium-ion battery anode material. By adding graphene (GO) to modify its surface, a composite nanomaterial of amorphous VOx and graphene is obtained. This product is then used as the anode material for sodium-ion batteries, resulting in low cost and greater environmental friendliness.

[0007] The technical solution of this invention is described below in conjunction with the accompanying drawings:

[0008] This invention provides a method for preparing a sodium-ion battery anode material, comprising the following steps:

[0009] Step 1: Weigh 0.001 mol of vanadium acetylacetone;

[0010] Step 2: Measure 20 mL of isopropanol and 5 mL of glycerol, pour them into a beaker and stir magnetically;

[0011] Step 3: During the stirring process in Step 2, add the acetylacetone vanadium oxide powder weighed in Step 1 and continue stirring to form a mixture;

[0012] Step 4: Sonicate the mixture from Step 3 until it becomes clear and transparent in green. At this point, the mixture is referred to as Solution A.

[0013] Step 5: Weigh 1.105 mmol of graphene (GO) and add it to 4 mL of deionized water for ultrasonic treatment to obtain GO dispersion B;

[0014] Step 6: Add the dispersion B obtained in Step 5 dropwise to the green solution A prepared in Step 4 and stir magnetically to obtain a dark yellow suspension;

[0015] Step 7: Pour the dark yellow suspension obtained in Step 6 into a stainless steel reactor with a volume of 50 mL and a PTFE liner. Then place the reactor in a constant temperature drying oven and heat it at 180°C for 12 hours.

[0016] Step 8: Remove the reaction vessel from Step 7, allow it to cool naturally to room temperature, wash it with deionized water and ethanol, centrifuge it several times, and then place the obtained product in a freeze dryer for vacuum drying.

[0017] Step 9: Place the dried sample from Step 8 into a tube furnace and heat it at 2°C / min. -1 The temperature was increased to 400℃ and held for 2 hours for calcination to prepare VO. x / rGO-5%;

[0018] Step 10: Take the VO prepared in step 9 x / rGO-5% was weighed with acetylene black and PVDF in a mass ratio of 7:2:1 and dissolved separately in NMP solvent. The mixture was stirred continuously for 4 hours to make the slurry uniformly mixed. After stirring, the slurry was uniformly coated onto the copper foil surface using a 75μm coater and dried in a vacuum oven at 60℃ for 12 hours.

[0019] Step 11: Take out the dried sample from Step 10, cut it into circular electrode sheets, weigh them, and mark them.

[0020] Step 12: Using the electrode from Step 11 as the negative electrode, the metallic Na sheet as the positive electrode, and the glass fiber as the separator, assemble a sodium-ion half-cell.

[0021] Furthermore, in step eight, the room temperature is 18℃-28℃.

[0022] Furthermore, in step eight, 400 ml of deionized water is used.

[0023] Furthermore, in step eight, 400 ml of ethanol is used.

[0024] Furthermore, in step eight, the washing and centrifugation are performed 15-20 times.

[0025] The beneficial effects of this invention are as follows:

[0026] 1) This invention employs a simple, rapid, and environmentally friendly hot solvent method and calcination treatment to prepare amorphous vanadium oxide (VO₂O₃). x ) and its graphene composite material (VO x / rGO-5%), in the preparation of VO x No chemical reductions or hazardous reducing agents are added during the hydrothermal reaction of the material. GO is added only in the presence of water, and after the reaction, GO is successfully reduced to rGO. VOx and its graphene composite material have an amorphous structure and do not have obvious and sharp diffraction peaks.

[0027] 2)VO x / rGO-5% composite material is composed of graphene sheets and solid nanospheres. The two have a synergistic effect, which reduces the re-stacking of graphene sheets and prevents problems such as agglomeration and crushing of nanospheres. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 For GO, VO x / rGO-5%, VO x / rGO-10%, VO x XRD pattern;

[0030] Figure 2 For VO x / rGO-5% SEM image;

[0031] Figure 3 For VO x SEM image;

[0032] Figure 4a For VO x TEM image;

[0033] Figure 4b For VO x / rGO-5% TEM image;

[0034] Figure 5aThe XPS graph is the full spectrum.

[0035] Figure 5b XPS graph for V 2p;

[0036] Figure 5c XPS graph for O1s;

[0037] Figure 5d XPS plot for C1s;

[0038] Figure 6 For 0.1A·g -1 A schematic diagram of the cycle and coulomb efficiency curves at time;

[0039] Figure 7a Schematic diagram of cycle and coulomb efficiency curves at different scaling ratios

[0040] Figure 7b Schematic diagram of charge-discharge curves at different rates;

[0041] Figure 7c For 0.5A·g -1 A schematic diagram of the long-cycle and Coulomb efficiency curves. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0044] Example 1

[0045] This embodiment provides a method for preparing VOx / rGO-5%, including the following steps:

[0046] Step 1: Weigh 0.001 mol of vanadium acetylacetone;

[0047] Step 2: Measure 20 mL of isopropanol and 5 mL of glycerol, pour them into a beaker and stir magnetically;

[0048] Step 3: During the stirring process in Step 2, add the acetylacetone vanadium oxide powder weighed in Step 1 and continue stirring to form a mixture;

[0049] Step 4: Sonicate the mixture from Step 3 until it becomes clear and transparent in green. At this point, the mixture is referred to as Solution A.

[0050] Step 5: Weigh 1.105 mmol of graphene (GO) and add it to 4 mL of deionized water for ultrasonic treatment to obtain GO dispersion B;

[0051] Step 6: Add the dispersion B obtained in Step 5 dropwise to the green solution A prepared in Step 4 and stir magnetically to obtain a dark yellow suspension;

[0052] Step 7: Pour the dark yellow suspension obtained in Step 6 into a stainless steel reactor with a volume of 50 mL and a PTFE liner. Then place the reactor in a constant temperature drying oven and heat it at 180°C for 12 hours.

[0053] Step 8: Remove the reaction vessel from Step 7, allow it to cool naturally to room temperature, wash it with deionized water and ethanol, centrifuge it several times, and then place the obtained product in a freeze dryer for vacuum drying.

[0054] The process involved: room temperature 18℃-28℃; 400ml deionized water; 400ml ethanol; washing and centrifugation 15-20 times.

[0055] Step 9: Place the dried sample from Step 8 into a tube furnace and heat it at 2°C / min. -1 The temperature was increased to 400℃ and held for 2 hours for calcination to prepare VO. x / rGO-5%. Because 1.105 mmol of graphene was added during the hydrothermal process, representing 5% by mass, the resulting product was named VO. x / rGO-5%.

[0056] Example 2

[0057] This embodiment provides a sodium-ion battery, wherein the active material in the negative electrode material of the sodium-ion battery is VO prepared in Example 1. x / rGO-5%, details are as follows:

[0058] The VO prepared in step nine of Example 1 x / rGO-5% was weighed with acetylene black and PVDF in a mass ratio of 7:2:1 and dissolved separately in NMP solvent. The mixture was stirred continuously for 4 hours to make the slurry uniformly mixed. After stirring, the slurry was uniformly coated onto the copper foil surface using a 75μm coater and dried in a vacuum oven at 60℃ for 12 hours.

[0059] Step 11: Take out the dried sample from Step 10, cut it into circular electrode sheets, weigh them, and mark them.

[0060] Step 12: Using the electrode from Step 11 as the negative electrode, the metallic Na sheet as the positive electrode, and the glass fiber as the separator, assemble a sodium-ion half-cell.

[0061] Comparative Example 1 VO x Preparation of / rGO-10%;

[0062] The difference between this comparative example and Example 1 is that the amount of GO added during the hydrothermal process in step five is 2.21 mmol, which accounts for 10% of the total mass. Therefore, the product obtained is named VOx / rGO-10%. The rest is the same as in Example 1.

[0063] Comparative Example 2 VO x Preparation of;

[0064] The difference between this comparative example and Example 1 is that no GO dispersion was added during the experiment, and steps five and six were omitted, thus obtaining amorphous vanadium oxide, which was named VOx. The rest is the same as in Example 1.

[0065] Characterization test

[0066] XRD characterization tests and analyses were performed on Example 1, Comparative Example 1, and Comparative Example 2, as follows: Figure 1 As shown, VO x It lacks a crystalline phase and has an amorphous structure. VO x The unique peak intensity of GO in the characteristic peaks of the composite material disappeared, and no sharp peaks existed. However, there was a broad and diffuse peak in the range of 2θ of 15-30°, which proved that GO was successfully reduced to rGO during the hydrothermal reaction process, and that both composite materials were also amorphous structures.

[0067] SEM and TEM characterization tests were performed on Example 1 and Comparative Example 2, such as... Figure 2 As shown in Figure 4, GO undergoes a reduction reaction during hydrothermal treatment to generate rGO, and the presence of VO in the composite material structure with added graphene is clearly visible. x It exhibits more complete and well-dispersed nanospheres, with a diameter of approximately 600-800 nm, and is interwoven with graphene sheets, VO x Agglomeration, fragmentation, and stacking between graphene sheets are effectively mitigated, resulting in a non-oriented wrinkled surface with high flexibility and overall structural integrity. At the same time, the conductive transmission distance is greatly shortened, which is conducive to exhibiting excellent electrochemical performance.

[0068] XPS characterization analysis was performed on Example 1 to further investigate its chemical composition and surface elemental valence states, as shown in Figure 5. Figure 5aThe full spectrum of the example shows that the characteristic peaks of V 2p, O 1s and C 1s are sharp and obvious, indicating the presence of the three elements V, O and C. Figure 5b The graph shows the V 2p peak of vanadium. The broad V 2p peak indicates the presence of multiple vanadium valence states. The graph shows that V 2p... 3 / 2 With V 2p 1 / 2 The electron binding energies at 516.2 and 523.5 eV, and 525.1 and 517.9 eV, respectively, correspond to V0. 4+ and V 5+ . Figure 5c The diagram depicts the O1s spectrum, with three peaks at 532.5, 531.7, and 530.4 eV corresponding to the CO, COV, and VO bonds, respectively. The C1s spectrum is then decomposed, as shown below. Figure 5d As shown, the peaks at 288.5, 285.7, and 284.7 eV correspond to O=CO, CO, and C=C bonds, respectively. The relatively weak peaks at 288.5 and 285.7 eV, where oxygen-containing functional groups exist, indicate that GO was successfully reduced to rGO. In summary, the curve fitting results show that Example 1 is a composite material of vanadium oxide and rGO in mixed valence states.

[0069] Example 1 and Comparative Examples 1 and 2 were used as the negative electrode active materials for sodium-ion batteries. The preparation method of the negative electrode sheet is as follows: The active material, acetylene black (conductive agent), and PVDF (binder) were weighed at a mass ratio of 7:2:1 and dissolved separately in NMP solvent. The mixture was stirred continuously for 4 hours to ensure uniform mixing of the slurry. After stirring, the slurry was uniformly coated onto the surface of copper foil using a 75μm coater and dried in a vacuum oven at 60℃ for 12 hours. After drying, the foil was removed, cut into circular electrode sheets, weighed, and marked for later use.

[0070] Assemble a button cell of model 2035: using the prepared electrode sheet as the negative electrode, the metal Na sheet as the positive electrode, the glass fiber as the separator, and a mixed solution containing 1M NaClO4 (solvent: EC:DMC:EMC=1:1:1 vol%+5% FEC) as the electrolyte, and assemble it into a sodium-ion half cell.

[0071] Performance testing

[0072] 1. The sodium-ion coin cell prepared in the embodiments of the present invention was subjected to a 0.1 A·g test. -1 Cyclic and coulombic efficiency tests at current density yielded the following results: Figure 6 As shown in the figure, the example exhibits excellent cycle stability when used as the negative electrode in a sodium-ion battery. (0.1 A·g) -1 It provides 613 mAh·g at current density -1High initial capacity, maintaining 254 mAh·g after 100 cycles. -1 It has a reversible discharge specific capacity and a coulombic efficiency close to 100%.

[0073] 2. Cyclic tests were conducted on the embodiments of the present invention at different magnification rates, demonstrating excellent magnification capability. The results are as follows: Figure 7a As shown in the figure. It can be seen from the figure that the examples were performed at 0.1, 0.2, 0.5, and 1 Å·g. -1 At different rates, the reversible discharge specific capacities were 336, 258, 230, and 211 mAh·g, respectively. -1 Even in 2A·g -1 Its reversible capacity can still reach 189 mAh·g under high current density. -1 When the current density returns to 0.1 A·g -1 The reversible discharge specific capacity can still be maintained at 286 mAh·g. -1 The Coulomb efficiency is close to 100%. Comparative Examples 1 and 2 at 0.1 A·g -1 The reversible specific capacities at current densities are 286 and 257 mAh·g, respectively. -1 After cycling at various current densities, it returned to 0.1 A·g. -1 Its reversible capacity remained at 252 and 256 mAh·g, respectively. -1 It can be seen that, at different discharge rates, the embodiment still maintains the highest reversible discharge specific capacity. Figure 7b The figures show the charge-discharge curves of the embodiment at different rates. As can be seen from the figures, the charge-discharge curves have similar shapes, indicating that the reaction processes are similar at different current densities. Furthermore, the material does not have a distinct charge-discharge plateau, suggesting that the energy storage mechanism is dominated by capacitive behavior.

[0074] 3. The embodiments of the present invention were subjected to a process at 0.5 A·g -1 The results of long-cycle testing at current density are as follows: Figure 7c As shown in the figure, the addition of graphene improves the overall conductivity of the material, with the initial discharge capacity of the example reaching as high as 461 mAh·g. -1 After 400 cycles, its reversible capacity can still be maintained at 185 mAh·g. -1 Higher than Comparative Example 1 (160mAh·g) -1 ) and Comparative Example 2 (159mAh·g -1 ).

[0075] The performance tests above show that the proportion of graphene added affects the overall performance of the battery. Comparative Example 1 exhibits higher cycle and rate performance at high current densities than Comparative Example 2, but its performance at low current densities is similar to or even lower than Comparative Example 2. This may be related to excessive graphene addition. Therefore, carefully controlling the amount of graphene used is crucial while improving the material's conductivity.

[0076] In summary, this invention prepares amorphous vanadium oxides and their graphene composites in different proportions. When used as anodes in sodium-ion batteries, they exhibit excellent cycle stability, high rate performance, long lifespan, and an environmentally friendly and simple preparation method, demonstrating broad application prospects.

[0077] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the invention. Further modifications can be readily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a sodium-ion battery anode material, characterized in that, Includes the following steps: Step 1: Weigh 0.001 mol of vanadium acetylacetone; Step 2: Measure 20 mL of isopropanol and 5 mL of glycerol, pour them into a beaker and stir magnetically; Step 3: During the stirring process in Step 2, add the acetylacetone vanadium oxide powder weighed in Step 1 and continue stirring to form a mixture; Step 4: Sonicate the mixture from Step 3 until it becomes clear and transparent in green. At this point, the mixture is referred to as Solution A. Step 5: Weigh 1.105 mmol of graphene (GO) and add it to 4 mL of deionized water for ultrasonic treatment to obtain GO dispersion B; Step 6: Add the dispersion B obtained in Step 5 dropwise to the green solution A prepared in Step 4 and stir magnetically to obtain a dark yellow suspension; Step 7: Pour the dark yellow suspension obtained in Step 6 into a stainless steel reactor with a volume of 50 mL and a PTFE liner. Then place the reactor in a constant temperature drying oven and heat it at 180°C for 12 hours. Step 8: Remove the reaction vessel from Step 7 after the reaction is complete, allow it to cool naturally to room temperature, wash it with deionized water and ethanol, centrifuge it several times, and then place the obtained product in a freeze dryer for vacuum drying. Step 9: Place the dried sample from Step 8 into a tube furnace and heat it at 2°C / min. -1 The temperature was increased to 400℃ and held for 2 hours for calcination to prepare VO. x / rGO-5%; Step 10: Take the VO prepared in step 9 x / rGO-5% was weighed with acetylene black and PVDF in a mass ratio of 7:2:1 and dissolved separately in NMP solvent. The mixture was stirred continuously for 4 hours to make the slurry uniformly mixed. After stirring, the slurry was uniformly coated onto the copper foil surface using a 75μm coater and dried in a vacuum oven at 60℃ for 12 hours. Step 11: Take out the dried sample from Step 10, cut it into circular electrode sheets, weigh them, and mark them. Step 12: Using the electrode from Step 11 as the negative electrode, the metallic Na sheet as the positive electrode, and the glass fiber as the separator, assemble a sodium-ion half-cell.

2. The method for preparing a sodium-ion battery negative electrode material according to claim 1, characterized in that, In step eight, the room temperature is 18℃-28℃.

3. The method for preparing a sodium-ion battery negative electrode material according to claim 1, characterized in that, In step eight, 400 ml of deionized water is used.

4. The method for preparing a sodium-ion battery negative electrode material according to claim 1, characterized in that, In step eight, 400 ml of ethanol is used.

5. The method for preparing a sodium-ion battery negative electrode material according to claim 1, characterized in that, In step eight, the product is washed and centrifuged 15-20 times.

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