A sodium rhodiolanate / MXene composite material and its preparation method and application

Abstract

The present invention provides a sodium rhodiolanate / MXene composite material, a preparation method, and applications thereof. The sodium rhodiolanate / MXene composite material comprises MXene and sodium rhodiolanate supported between layers and / or on the surface of the MXene. The present invention prepares a three-dimensional sodium rhodiolanate / MXene composite material by combining sodium rhodiolanate and MXene. The sodium rhodiolanate is supported on the surface and / or between layers of the MXene, and the synergistic effect of the two increases the specific surface area and spatial structure of the material. A sodium ion battery prepared using the above-mentioned material exhibits a high reversible specific capacity and good cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a sodium rhodiolanate / MXene composite material and a preparation method and application thereof. Background Art

[0002] As demand for energy storage devices like electric vehicles and mobile devices continues to grow, resource consumption is also increasing. Consequently, sodium-ion batteries, which are abundant in natural resources, have attracted widespread attention from researchers. Sodium-ion batteries are low-cost, made from widely available and abundant raw materials, and have a similar electrochemical potential to lithium-ion batteries, making them a potential alternative.

[0003] Commonly used sodium ion battery positive electrode materials include transition metal oxides, Prussian blue analogs, and polyanion positive electrode materials. CN107093713A discloses an anion-doped sodium ion battery oxide positive electrode material, which contains a variable valence metal oxide and a doped anion. It is low-cost, has a simple synthesis method, and improves the cycle performance of the sodium ion battery. CN107978743B discloses a sodium ion battery positive electrode material and a preparation method thereof, which comprises dissolving a sodium source, an iron source, a manganese source, a vanadium source, and a phosphorus source in deionized water in a stoichiometric ratio, adding a mixed solution of tetraethylene glycol and ethylene glycol, stirring and heating at room temperature, and then freeze-drying and calcining at high temperature to obtain a sodium ion battery positive electrode material. This method has good repeatability, simple operation, low cost, and good industrial prospects. CN105226264B discloses a sodium-rich positive electrode material for a sodium ion battery. The material is prepared by mixing a nickel salt solution, a cobalt salt solution, a manganese salt solution, an oxalate solution, and a sodium salt solution under stirring, performing a hydrothermal reaction, and then cooling, solid-liquid separation, washing, drying, and calcining to obtain a sodium-rich positive electrode material. The material has low cost and the prepared sodium ion battery has good performance.

[0004] The prior art provides a variety of positive electrode materials for sodium ion batteries, which achieves the goal of reducing costs. However, the specific capacity and cycle stability of the above-mentioned positive electrode materials still need to be further improved. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention aims to provide a sodium rhodiolanate / MXene composite material, its preparation method, and application. The present invention combines sodium rhodiolanate with MXene to prepare a three-dimensional sodium rhodiolanate / MXene composite material. Sodium rhodiolanate is loaded on the surface and / or between the layers of the MXene, and the synergistic effect of the two increases the specific surface area and spatial structure of the material. The sodium ion battery prepared using the above material has a high reversible specific capacity and good cycle stability.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a sodium rhodiolanate / MXene composite material, wherein the sodium rhodiolanate / MXene composite material comprises MXene and sodium rhodiolanate supported between layers and / or on the surface of the MXene.

[0008] Sodium rhodiolanate (Na2C6O6) has a high theoretical specific capacity as a sodium-ion battery cathode material. It can be obtained from natural biomass and has low energy consumption, making it an attractive, low-cost, and sustainable organic cathode material for sodium-ion batteries. However, during the charge and discharge process, sodium rhodiolanate undergoes an irreversible phase transition due to its poor sodium removal ability, resulting in a significant decrease in specific capacity.

[0009] The present invention prepares a sodium rosette phosphate / MXene composite material by compounding sodium rosette phosphate and MXene, thereby improving the reversible specific capacity and cycle stability of the material. First, MXene is a two-dimensional inorganic layered compound whose stacking presents an accordion-like layered morphology. When sodium rosette phosphate is loaded between its layers and on its surface, the two act synergistically to form a three-dimensional sodium rosette phosphate / MXene composite material. The overall surface area of ​​the material is increased, the spatial structure is improved, the diffusion rate of sodium ions during the charge and discharge process is accelerated, and the stability of the material is improved. Second, the conjugation effect formed between MXene and sodium rosette phosphate nanoparticles reduces the occurrence of irreversible phase transitions in the entire material during the charge and discharge cycle, further improving the stability of the material. Third, the MXene end group contains a group (such as a hydroxyl group), which works together with sodium rosette phosphate to improve the wettability of the electrolyte and simultaneously improve the reversible specific capacity and cycle stability of the material.

[0010] Preferably, the MXene comprises Ti2CT x 、Ti3C2T x and Ti4C3T x Any one or a combination of at least two of x Including any one of -OH, -F and =O or a combination of at least two, for example, MXene may contain -OH and -F at the same time, -F and =O at the same time, or -OH, -F and =O at the same time.

[0011] In the present invention, MXene is preferably a carbon-containing two-dimensional inorganic layered material with specific groups. The presence of functional groups is beneficial to improving the wetting and contact ability of the composite material with the electrolyte, increasing the transmission rate of the electrolyte ions, and further improving the reversible specific capacity and cycle stability of the material.

[0012] Preferably, the mass ratio of the sodium rhodiolanate to the MXene is (6-8):3, for example, 6:3, 6.5:3, 7:3, 7.5:3 or 8:3.

[0013] In a second aspect, the present invention provides a method for preparing the sodium rhodiolanate / MXene composite material according to the first aspect, the preparation method comprising:

[0014] MXene and sodium rhodiolanate are mixed and subjected to an alcohol thermal reaction to obtain the sodium rhodiolanate / MXene composite material.

[0015] The present invention adopts a simple co-precipitation method to mix MXene and sodium rhodiolanate for alcohol thermal reaction. The preparation method is simple, and the prepared material has high reversible specific capacity and good cycle stability.

[0016] Preferably, the mass ratio of the sodium rhodiolanate to the MXene is (6-8):3, for example, 6:3, 6.5:3, 7:3, 7.5:3 or 8:3.

[0017] The present invention preferably uses a specific ratio of sodium rhodiolanate and MXene to prepare a sodium rhodiolanate / MXene composite material. Within this range, the combination effect of the two is optimal, and the synergistic effect of MXene and sodium rhodiolanate can be fully exerted to improve the specific capacity and cycle stability of the material.

[0018] Preferably, the mixing is carried out according to the following steps:

[0019] MXene is dispersed in the first solvent, and sodium rosinase is added after ultrasonication to obtain a mixed solution.

[0020] Preferably, the first solvent comprises anhydrous ethanol.

[0021] Preferably, the concentration of the mixed solution is 3-5 mg / mL, for example, 3 mg / mL, 3.5 mg / mL, 4 mg / mL, 4.5 mg / mL or 5 mg / mL.

[0022] The mixed solution of the present invention has an optimal concentration range. Within this range, the two substances are fully combined and evenly dispersed, giving full play to the synergistic effect of MXene and sodium rhodiolanate, and improving the electrochemical performance of the material.

[0023] Preferably, the ultrasound duration is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0024] In the present invention, after the mixed solution is prepared, the prepared mixed solution can be ultrasonicated again before the alcohol thermal reaction, and the ultrasonication time is 25 to 35 minutes, for example, 25 minutes, 28 minutes, 30 minutes, 32 minutes or 35 minutes, etc., which is conducive to the subsequent alcohol thermal reaction.

[0025] As a preferred technical solution of the preparation method of the present invention, the temperature of the alcohol thermal reaction is 150-180°C, for example, it can be 150°C, 155°C, 160°C, 165°C, 170°C, 175°C or 180°C.

[0026] Preferably, the alcohol thermal reaction time is 12 to 16 hours, for example, it can be 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours, 15 hours, 15.5 hours or 16 hours.

[0027] In the present invention, it is preferred to adopt a specific temperature and time for the alcohol thermal reaction. When the temperature is 150-180° C. and the time is 12-16 hours, the performance of the prepared material is better.

[0028] As a preferred technical solution of the preparation method of the present invention, the sodium rosehip acid is also pretreated before mixing;

[0029] Preferably, the pretreatment of the sodium rosehip is carried out as follows:

[0030] Sodium rosehip acid is dissolved to obtain a sodium rosehip acid dispersion, and a second solvent is added thereto, followed by ultrasonication, filtration and drying.

[0031] Illustratively, the ultrasonic time after sodium rhodiolanate is added to the second solvent is 10 to 20 minutes, for example, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, etc.

[0032] Preferably, the concentration of the sodium rhodiolanate dispersion is 3-5 mg / mL, for example, 3 mg / mL, 3.5 mg / mL, 4 mg / mL, 4.5 mg / mL or 5 mg / mL.

[0033] Preferably, the second solvent is anhydrous ethanol.

[0034] Preferably, the volume ratio of the sodium rhodiolanate dispersion to the second solvent is 1:(9-11), for example, 1:9, 1:9.5, 1:10, 1:10.5 or 1:11.

[0035] Illustratively, the drying temperature of sodium rhodiolanate after adding the second solvent is 60-80°C, for example, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, and the drying time is 3-6h, for example, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, etc.

[0036] In the present invention, the sodium rosehip acid salt is pretreated before mixing to reduce the size of the material and improve the size distribution of the sodium rosehip acid salt raw material.

[0037] As a preferred technical solution of the preparation method of the present invention, the MXene is also pretreated before mixing.

[0038] Preferably, the pretreatment of the MXene is carried out as follows:

[0039] The MXene is dispersed in a third solvent to obtain a MXene dispersion, and the MXene dispersion is heated and stirred, ultrasonicated, centrifuged, washed, and dried.

[0040] Preferably, the third solvent is dimethyl sulfoxide.

[0041] Preferably, the concentration of the MXene dispersion is 0.05 to 0.15 g / mL, for example, 0.05 g / mL, 0.08 g / mL, 0.1 g / mL, 0.12 g / mL or 0.15 g / mL.

[0042] Preferably, the temperature of the heating and stirring is 35-45°C, for example, 35°C, 38°C, 40°C, 42°C or 45°C, and the time is 22-26h, for example, 22h, 23h, 24h, 25h or 26h.

[0043] In the present invention, MXene is pretreated to obtain intercalated and exfoliated MXene nanosheets, which can expand the interlayer spacing of MXene, increase the specific surface area, and provide more active sites for the embedding of other active substances.

[0044] Illustratively, after the alcohol thermal reaction in the present invention, vacuum filtration and drying steps are further performed, and the drying temperature is 60-80°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, and the time is 3-6h, for example, it can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, etc.

[0045] In a third aspect, the present invention provides a sodium ion battery, wherein the positive electrode of the sodium ion battery comprises the sodium rhodiolanate / MXene composite material according to the first aspect.

[0046] The sodium ion battery prepared by the present invention has good specific capacity and cycle stability.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention prepares a sodium rosehip phosphate / MXene composite material by compounding sodium rosehip phosphate and MXene. First, sodium rosehip phosphate is loaded between the layers and on the surface of the MXene, and synergistically forms a sodium rosehip phosphate / MXene composite material with a three-dimensional structure. The overall surface area of ​​the material is increased, the spatial structure is improved, the diffusion rate of sodium ions during the charge and discharge process is accelerated, and the stability of the material is improved. Second, the conjugation effect formed between the MXene and sodium rosehip phosphate nanoparticles reduces the occurrence of irreversible phase transitions of the entire material during the charge and discharge cycle, further improving the stability of the material. Third, the MXene end group contains a group (such as a hydroxyl group), which works together with the sodium rosehip phosphate to improve the wettability of the electrolyte and improve the reversible specific capacity and cycle stability of the material. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0050] The MXenes used in the specific embodiments of the present invention are all from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd. (CAS: 12363-89-2).

[0051] Example 1

[0052] This embodiment provides a sodium rhodiolanate / MXene composite material, comprising MXene and sodium rhodiolanate supported between layers and / or on the surface of the MXene, wherein the MXene is Ti2CT x , where T x It is -OH, -F and =O.

[0053] This embodiment also provides a method for preparing the sodium rhodiolanate / MXene composite material, comprising:

[0054] (1) Pretreatment of sodium rhodiolanate: Sodium rhodiolanate (Na2C6O6) powder was dissolved in deionized water to prepare a 4 mg / mL sodium rhodiolanate dispersion, which was then mixed with anhydrous ethanol at a volume ratio of 1:10. After ultrasonic treatment at room temperature for 15 min, the precipitate was collected by vacuum filtration and dried in a vacuum oven at 70 °C for 5 h. The treated Na2C6O6 was recorded as sample M1.

[0055] (2) Pretreatment of MXene: The MXene sample was dispersed in dimethyl sulfoxide solvent to obtain a MXene dispersion with a concentration of 0.1 g / mL. The dispersion was stirred at 40 °C for 24 h, and then an appropriate amount of deionized water was added. The sample was placed in an ultrasonic cleaner for 4 h. Finally, the intercalated and exfoliated MXene nanosheets were obtained after centrifugation, washing, and drying, which was labeled as sample M2.

[0056] (3) Synthesis of sodium rosehip phosphate / MXene composite material: Sample M2 was added to anhydrous ethanol and ultrasonicated for 2 h. Then, sample M1 was added and mixed evenly. The mass ratio of sample M1 to M2 was 7:3. A mixture with a concentration of 4 mg / ml was obtained. The mixture was ultrasonicated at room temperature for 30 min. Then, it was thermally reacted at 170 °C for 14 h and naturally cooled to room temperature. Finally, the precipitate was collected by vacuum filtration and dried in a vacuum oven at 70 °C for 5 h to prepare a sodium rosehip phosphate / MXene composite material, which was labeled as sample M3.

[0057] Example 2

[0058] This embodiment provides a sodium rhodiolanate / MXene composite material, comprising MXene and sodium rhodiolanate supported between layers and / or on the surface of the MXene, wherein the MXene is Ti3C2T x , where T x It is -OH, -F and =O.

[0059] This embodiment also provides a method for preparing the sodium rhodiolanate / MXene composite material, comprising:

[0060] (1) Pretreatment of sodium rhodiolanate: Sodium rhodiolanate (Na2C6O6) powder was dissolved in deionized water to prepare a 5 mg / mL sodium rhodiolanate dispersion, which was then mixed with anhydrous ethanol at a volume ratio of 1:10. After ultrasonic treatment at room temperature for 15 min, the precipitate was collected by vacuum filtration and dried in a vacuum oven at 80 °C for 4 h.

[0061] (2) Pretreatment of MXene: MXene samples were dispersed in dimethyl sulfoxide solvent to obtain a MXene dispersion with a concentration of 0.05 g / mL. The dispersion was stirred at 40 °C for 24 h, and then an appropriate amount of deionized water was added. The sample was placed in an ultrasonic cleaner for 4 h, and finally, the intercalated and exfoliated MXene nanosheets were obtained after centrifugation, washing, and drying.

[0062] (3) Synthesis of sodium rosehip phosphate / MXene composite material: MXene nanosheets were added to anhydrous ethanol and ultrasonicated for 2 h. Then, the pretreated sodium rosehip phosphate obtained in step (1) was added and mixed evenly. The mass ratio of the sample sodium rosehip phosphate to MXene nanosheets was 6:3. A mixture with a concentration of 5 mg / ml was obtained. The mixture was ultrasonicated at room temperature for 30 min, then subjected to alcohol thermal reaction at 180 °C for 14 h, and naturally cooled to room temperature. Finally, the precipitate was collected by vacuum filtration and dried in a vacuum oven at 60 °C for 6 h to prepare a sodium rosehip phosphate / MXene composite material.

[0063] Example 3

[0064] This embodiment provides a sodium rhodiolanate / MXene composite material, comprising MXene and sodium rhodiolanate supported between layers and / or on the surface of the MXene, wherein the MXene is Ti4C3T x , where T x It is -OH, -F and =O.

[0065] This embodiment also provides a method for preparing the sodium rhodiolanate / MXene composite material, comprising:

[0066] (1) Pretreatment of sodium rhodiolanate: Sodium rhodiolanate (Na2C6O6) powder was dissolved in deionized water to prepare a 3 mg / mL sodium rhodiolanate dispersion, which was then mixed with anhydrous ethanol at a volume ratio of 1:10. After ultrasonic treatment at room temperature for 15 min, the precipitate was collected by vacuum filtration and dried in a vacuum oven at 65 °C for 6 h.

[0067] (2) Pretreatment of MXene: MXene samples were dispersed in dimethyl sulfoxide solvent to obtain a MXene dispersion with a concentration of 0.15 g / mL. The dispersion was stirred at 40 °C for 24 h, and then an appropriate amount of deionized water was added. The sample was placed in an ultrasonic cleaner for 4 h, and finally, the intercalated and exfoliated MXene nanosheets were obtained after centrifugation, washing, and drying.

[0068] (3) Synthesis of sodium rosilicate / MXene composite material: MXene nanosheets were added to anhydrous ethanol and ultrasonicated for 2 h. Then, the pretreated sodium rosilicate obtained in step (1) was added and mixed evenly. The mass ratio of sodium rosilicate to MXene nanosheets was 8:3. A mixture with a concentration of 3 mg / ml was obtained. The mixture was ultrasonicated at room temperature for 30 min, and then subjected to alcohol thermal reaction at 150 °C for 16 h. The mixture was naturally cooled to room temperature. Finally, the precipitate was collected by vacuum filtration and dried in a vacuum oven at 80 °C for 6 h to prepare a sodium rosilicate / MXene composite material.

[0069] Example 4

[0070] Except for not performing step (1), the rest is the same as Example 1.

[0071] Example 5

[0072] Except for not performing step (2), the rest is the same as Example 1.

[0073] Example 6

[0074] In addition to Ti2CT x Replaced by Ti2NT x Except for this, the rest are the same as in Example 1.

[0075] Example 7

[0076] Except that the mass ratio of samples M1 and M2 in step (3) is 10:3, the rest is the same as Example 1.

[0077] Example 8

[0078] Except that the mass ratio of samples M1 and M2 in step (3) is 5:3, the rest is the same as Example 1.

[0079] Example 9

[0080] Except that the temperature of the alcohol thermal reaction in step (3) is 130° C., the rest is the same as in Example 1.

[0081] Example 10

[0082] Except that the temperature of the alcohol thermal reaction in step (3) is 200° C., the rest is the same as in Example 1.

[0083] Comparative Example 1

[0084] Except that step (2) and step (3) are not performed, that is, the material contains only sodium rhodiolanate, the rest is the same as Example 1.

[0085] Comparative Example 2

[0086] Except for replacing MXene with graphene oxide, the rest is the same as Example 1.

[0087] 1. Assembly of sodium half-cell

[0088] The sodium rosehip palmitate / MXene composite material, Super P, and PVDF prepared in Examples 1-10 and Comparative Example 2 were mixed with an appropriate amount of NMP solvent in a mass ratio of 8:1:1 to prepare an electrode slurry, which was then evenly coated on an aluminum foil and then placed in a vacuum drying oven and dried at 80-120°C for 12 h. A slicer was used to prepare an electrode sheet with a diameter of 12 mm, and the sodium half-cell was assembled in a vacuum glove box filled with argon.

[0089] Comparative Example 1 was prepared in the same manner to obtain a sodium half-cell.

[0090] 2. Electrochemical performance test

[0091] The prepared sodium half-cell was placed in an electrochemical workstation and subjected to a 0.5 A / g constant current charge-discharge cycle test in a voltage range of 2.5 to 3.65 V. The initial specific capacity of the battery and the specific capacity after 150 cycles were recorded. The capacity retention rate was obtained by dividing the specific capacity after 150 cycles by the initial specific capacity. The test results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] From the above Examples 1-10, it can be seen that the present invention prepares a three-dimensional sodium rosehip acid / MXene composite material by compounding sodium rosehip acid and MXene. Sodium rosehip acid is loaded on the surface and / or between layers of MXene. The two act synergistically to increase the specific surface area and spatial structure of the material, thereby improving the reversible specific capacity and cycle stability of the material.

[0096] By comparing Example 1 and Examples 4-5, it can be seen that pre-treating sodium rosehip phosphate and MXene in the present invention is beneficial to improving the electrochemical properties of the materials. In Example 4, sodium rosehip phosphate was not treated, which resulted in a larger material size and difficulty in embedding between MXene layers. In Example 5, MXene was not treated, which resulted in stacking of MXene layers and a small specific surface area, making it difficult to accept embedding of other ions. Therefore, the cyclic temperature stability performance of Examples 4-5 is worse than that of Example 1.

[0097] By comparing Example 1 and Example 6, it can be seen that the preferred MXene of the present invention is used in combination with sodium rhodiolanate for better results. In Example 6, Ti2NT x , its specific capacity and cycle stability are worse than those of Example 1.

[0098] By comparing Example 1 with Examples 7-8, it can be seen that there is an optimal range for the ratio of sodium rhodiolanate and MXene in the present invention. When the sodium rhodiolanate content is on the high side, the conductivity of the material is low, and when the sodium rhodiolanate content is on the low side, the capacity of the material is low. Therefore, the specific capacity and cycle stability of Example 1 are better than those of Examples 7-8.

[0099] A comparison between Example 1 and Examples 9-10 shows that the temperature of the alcohol thermal reaction in the present invention affects the electrochemical properties of the material. When the temperature is low, less sodium rosilicate is adsorbed on the surface / interlayer of MXene, and the two are not effectively combined. When the temperature is high, MXene is partially oxidized. Therefore, the specific capacity and cycle stability of Example 1 are better than those of Examples 9-10.

[0100] By comparing Example 1 and Comparative Example 1, it can be seen that the sodium rhodiolanate / MXene composite material has excellent cycle performance and specific capacity. In the constant current charge and discharge cycle of 0.5 A / g, the initial specific capacity in Example 1 is 286.0 mAh / g, and the capacity retention rate after 150 cycles is 83.7%; while the initial capacity in Comparative Example 1 is 250.1 mAh / g, and the 150-cycle retention rate is 78.9%, indicating that the sodium rhodiolanate / MXene composite material prepared by the co-precipitation method of the present invention can effectively improve the specific capacity and cycle performance of a single material.

[0101] By comparing Example 1 and Comparative Example 2, it can be seen that the synergistic effect of sodium rhodiolanate and MXene in the present invention is more conducive to improving the electrochemical properties of the material. In Comparative Example 2, graphene oxide is used to prepare the sodium rhodiolanate / graphene oxide composite material, which has weaker wettability in the electrolyte than the sodium rhodiolanate / MXene composite material, and its specific capacity and cycle stability are worse than those of the present invention.

[0102] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A sodium rhodiolanate / MXene composite material, characterized in that: The sodium rhodiolanate / MXene composite material comprises MXene and sodium rhodiolanate supported between layers and / or on the surface of the MXene; The MXene is Ti2CT x 、Ti3C2T x and Ti4C3T x Any one or a combination of at least two of x Including any one or a combination of at least two of -OH, -F and =O; the mass ratio of the sodium rosehip palmitate to the MXene is (6-8):3; The MXene is an intercalated and exfoliated MXene nanosheet.

2. A method for preparing the sodium rhodiolanate / MXene composite material according to claim 1, characterized in that: The preparation method comprises: MXene and sodium rhodiolanate are mixed and subjected to an alcohol thermal reaction to obtain the sodium rhodiolanate / MXene composite material.

3. The preparation method according to claim 2, characterized in that The mass ratio of the sodium rosehip palmitate to the MXene is (6-8):

3.

4. The preparation method according to claim 2, characterized in that The mixing is carried out according to the following steps: MXene is dispersed in the first solvent, and sodium rosinase is added after ultrasonication to obtain a mixed solution.

5. The preparation method according to claim 4, characterized in that The first solvent includes anhydrous ethanol.

6. The preparation method according to claim 4, characterized in that The concentration of the mixed solution is 3-5 mg / mL.

7. The preparation method according to claim 4, characterized in that The ultrasonic time is 1 to 3 hours.

8. The preparation method according to claim 2, characterized in that The temperature of the alcohol thermal reaction is 150-180°C.

9. The preparation method according to claim 2, characterized in that The alcohol thermal reaction time is 12 to 16 hours.

10. The preparation method according to claim 2, characterized in that The sodium rosehip acid salt is also pretreated before mixing.

11. The preparation method according to claim 10, characterized in that: The pretreatment of the sodium roseate is carried out as follows: Sodium rosehip acid is dissolved to obtain a sodium rosehip acid dispersion, and a second solvent is added thereto, followed by ultrasonication, filtration and drying.

12. The preparation method according to claim 11, characterized in that The concentration of the sodium rhodiolanate dispersion is 3-5 mg / mL.

13. The preparation method according to claim 11, characterized in that The second solvent is anhydrous ethanol.

14. The preparation method according to claim 11, characterized in that The volume ratio of the sodium rosehip acid dispersion to the second solvent is 1:(9-11).

15. The preparation method according to claim 2, characterized in that The MXene is also pretreated before mixing.

16. The preparation method according to claim 15, characterized in that The pretreatment of the MXene is carried out as follows: The MXene is dispersed in a third solvent to obtain a MXene dispersion, and the MXene dispersion is heated and stirred, ultrasonicated, centrifuged, washed, and dried.

17. The preparation method according to claim 16, characterized in that The third solvent is dimethyl sulfoxide.

18. The preparation method according to claim 16, characterized in that The concentration of the MXene dispersion is 0.05 to 0.15 g / mL.

19. The preparation method according to claim 16, characterized in that The temperature of the heating and stirring is 35-45° C., and the time is 22-26 hours.

20. A sodium ion battery, characterized in that: The positive electrode of the sodium ion battery includes the sodium rhodiolanate / MXene composite material according to claim 1.

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