A sodium ion battery negative electrode material and its preparation method and application

Abstract

The present invention discloses a sodium ion battery negative electrode material, its preparation method, and application, belonging to the field of battery technology. The sodium ion battery negative electrode material comprises a porous material and a heterogeneous electron-accepting material composited with the porous material. The preparation method comprises providing a polyoxometalate; mixing the polyoxometalate with a porous material source solution, adjusting the system to alkaline, and stirring the reaction at room temperature to obtain the sodium ion battery negative electrode material. The sodium ion battery negative electrode material of the present invention separates the ion diffusion pathway from the electron conduction pathway by composited porous material with heterogeneous electron-accepting material. The sodium ion battery containing the negative electrode material has significantly improved battery capacity and long-cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a sodium ion battery negative electrode material and a preparation method and application thereof. Background Art

[0002] With the continuous growth of global energy demand and the urgent need for environmentally friendly energy storage technologies, potassium-ion batteries and sodium-ion batteries have become important research directions for next-generation energy storage systems within the alkali metal ion battery family due to their abundant resources and low cost compared to traditional lithium-ion batteries. Alkali metal ion batteries achieve charge storage and release through the insertion and extraction of alkali metal ions between the positive and negative electrodes. This process is primarily responsible for the negative electrode material, which is also considered one of the main factors limiting the development of battery power density. Improving the metal ion insertion and extraction process is the core of battery development.

[0003] According to the ion embedding / ejection theory, porous materials are widely used in negative electrodes because they can reduce the ion embedding / ejection energy barrier. Porous material negative electrodes can greatly improve the capacity and rate performance of batteries. Currently, the most widely reported negative electrode materials are transition metal compounds ( Figure 1 a) in the above is the main one. However, the stability of the porous material negative electrode battery widely used at present is difficult to meet the needs of industrialization. In the process of realizing the present invention, the inventors found that there are at least the following problems in the prior art: the early transition metals have strong reactivity, high coordination environment, and more empty non-bonding / anti-bonding orbitals, which provide sufficient orbital space for electron storage / release behavior. However, strong metal-non-metal interactions will mostly produce strong crystal field effects, energy level splitting, band gap widening, and limit electron storage / release behavior. Later transition metals are rich in d electrons and have low coordination numbers, which can provide action gaps for ion insertion / extraction, but their abundant d electrons will also occupy most of the non-bonding / bonding orbitals ( Figure 1 b- Figure 1 c in which M n+ (represents metal ions). The electronic behavior of charge and discharge can lead to a sharp increase in non-bonding interactions within the negative electrode material, reducing its stability. For porous materials, the storage and release of electrons is a key factor affecting material stability. This is especially true in high-current / high-capacity industrial environments, where the negative electrode material itself needs to store a large number of electrons / ions. This more intense electronic behavior poses even more severe challenges to negative electrode material stability. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a sodium ion battery negative electrode material, a preparation method and application thereof. The sodium ion battery negative electrode material separates the ion diffusion pathway from the electron conduction pathway by compounding a porous material with a heterogeneous electron accepting material. The sodium ion battery containing the negative electrode material has significantly improved battery capacity and long-cycle stability.

[0005] Compared with the prior art, the present invention has the following advantages:

[0006] 1. Aiming at the problem of coupled storage of electrons and ions in negative electrode materials, the present invention creatively proposes a new type of negative electrode material for sodium ion batteries based on the separation of ion diffusion pathways and electron transmission pathways. This specifically addresses the problem that in the charging and discharging process of traditional negative electrode materials, the simultaneous ion insertion / extraction and electron charging / discharging behavior of the negative electrode materials adversely affect the structure and orbit of the negative electrode materials. By compounding porous materials with heterogeneous electron-accepting materials, the separation of ion diffusion pathways and electron conduction pathways is achieved. The porous material does not store electrons, the negative electrode material has a high capacity, and the structure is stable in long-cycle electrochemical tests. The corresponding sodium ion battery still maintains a high capacity after 2000 charge and discharge cycles.

[0007] 2. In the sodium ion negative electrode material of the present invention, which is a composite of a porous material and a heterogeneous electron accepting material, the porous material is preferably Cu2NCN, which can fully combine its open crystal structure and low packing density, and [NCN] 2- The σ-donation and π-electron extraction of the ligand enable efficient diffusion of sodium ions and enhanced conductivity.

[0008] 3. In the sodium ion negative electrode material of the present invention, which is a composite of a porous material and a heterogeneous electron-accepting material, polyoxometalate is preferably used as the heterogeneous electron-accepting material. Its anion-centered conjugated framework can accept electrons and can perform reversible electron transfer at various potentials by adjusting the oxidation state. Its unique three-dimensional cluster structure can effectively avoid the storage of sodium ions.

[0009] 4. The sodium ion negative electrode material of the present invention is a composite of a porous material and a heterogeneous electron accepting material. The crystal structure of the porous material is stable during the charge and discharge cycle, and the battery capacity retention rate after 2000 charge and discharge cycles is as high as 99.93%, which has the characteristics of long cycle life.

[0010] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A diagram showing the cycle life of a battery using a transition metal compound as a negative electrode material and the principle of negative electrode charge and discharge in the background art;

[0012] Figure 2 This is a schematic diagram of the charging and discharging principle of the negative electrode material of the sodium ion battery of the present invention;

[0013] Figure 3 This is a scanning electron microscope image of the sodium ion battery negative electrode material of Example 1 and the Cu2NCN obtained in step 2 of Comparative Example 1; Figure 3 a and Figure 3 b is a scanning electron microscope image of Cu2NCN obtained in step 2 of comparative example 1, Figure 3 c and Figure 3 d is a scanning electron microscope image of the sodium ion battery negative electrode material of Example 1;

[0014] Figure 4 This is an elemental surface scanning image of the negative electrode material of the sodium ion battery in Example 1;

[0015] Figure 5 The XRD pattern, FTIR pattern, transmission electron microscopy pattern before and after cycling of the negative electrode material of the sodium ion battery in Example 1 are shown; Figure 5 a is the XRD pattern, Figure 5 b is the FTIR graph, Figure 5 c is the transmission electron microscopy image before cycling, Figure 5 d is the transmission electron microscopy image after cycling;

[0016] Figure 6 This is a schematic diagram of the long cycle test results of a sodium ion battery assembled with the sodium ion battery negative electrode material of Example 1;

[0017] Figure 7 Schematic diagram of electrochemical performance test results of sodium ion battery corresponding to POM and Cu2NCN composite materials of Comparative Example 1 at different rates;

[0018] Figure 8 This is the electrochemical CV curve of the sodium battery assembled using POM as the negative electrode material in Comparative Example 2. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of this application to clearly and completely describe the technical solution. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0020] In the following description, the term "and / or" is used to describe the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural.

[0021] In the following description, the terms "include", "comprising", "having" and "containing" are open-ended terms, meaning including but not limited to.

[0022] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0023] It will be understood by those skilled in the art that the numerical ranges in the examples of the present application are to be understood as also specifically disclosing each intermediate value between the upper and lower limits of the ranges. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also included in the present application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0024] Unless otherwise indicated, the technical / scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application belongs. Although this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

[0025] The technical principle adopted by the present invention is as follows: The present invention creatively provides a sodium ion battery negative electrode material composed of two materials, each of which provides an ion transmission path and an electron conduction path respectively. Figure 2 As shown, the sodium ion battery negative electrode material is composed of a composite of a porous material and a heterogeneous electron accepting material. The heterogeneous electron accepting material is hydrolyzed under alkaline conditions, inducing self-assembly with the porous material to form a regular nanoflower structure. During the charge and discharge cycle, the porous material provides an ion transport pathway, and the heterogeneous electron accepting material performs reversible electron transfer.

[0026] In one aspect, a sodium ion battery negative electrode material is provided, comprising a porous material and a heterogeneous electron accepting material composited with the porous material.

[0027] In some embodiments, the porous material is a transition metal compound crystalline material; and / or, the heterogeneous electron accepting material is a polyoxometalate; in some preferred embodiments, the transition metal in the transition metal compound crystalline material is Cu; in some specific embodiments, the porous material is Cu2NCN; in some preferred embodiments, the polyoxometalate topological skeleton is a Keggin type, and the heteroatom includes P; in some specific embodiments, the polyoxometalate is [Ni4(H2O)2(PW9O 34 )2] 10- .

[0028] In the present invention, the preferred polyoxometalate is [Ni4(H2O)2(PW9O 34 )2] 10- It contains an anion center composed of a high oxidation state transition metal and has a highly conjugated framework structure formed by oxygen bridges. It can absorb electrons to stabilize the charge distribution. Under potential, the oxidation state of the anion center changes, absorbing or releasing electrons to achieve reversible electron transfer.

[0029] In some embodiments, the sodium ion battery negative electrode material has a morphology of nanoflowers, and the thickness of the petal layer of the nanoflowers is 1.5-2.0 nm.

[0030] In one aspect, a method for preparing the above-mentioned sodium ion battery negative electrode material is provided, comprising:

[0031] Step 1: providing a polyoxometalate;

[0032] Step 2: Mix the polyoxometalate with a porous material source solution, adjust the system to alkaline, and stir at room temperature to obtain a sodium ion battery negative electrode material.

[0033] In some specific embodiments, the method for preparing the negative electrode material for a sodium ion battery specifically includes:

[0034] Step 1: providing a polyoxometalate, comprising:

[0035] Step 101, dissolving Na2WO4·2H2O, NaHPO4·7H2O, and Ni(NO3)2·6H2O in deionized water at a mass ratio of 1:(0.02-0.2):(0.05-0.5), and adjusting the pH to 6-8 with hydrochloric acid to obtain a light green suspension;

[0036] Step 102: reflux the light green suspension; in some specific embodiments, the reflux temperature is 80-100° C., and the reflux time is 0.5-5 h;

[0037] Step 103: After the reflux is completed, the mixture is filtered and the filtrate is crystallized to obtain a polyoxometalate;

[0038] Step 2: mixing the polyoxometalate with a porous material source solution, adjusting the system to alkaline, and stirring at room temperature to obtain a sodium ion battery negative electrode material, comprising:

[0039] Step 201: Under room temperature, dissolve CuCl2·2H2O and the polyoxometalate in deionized water at a mass ratio of 1:(0.1-1), then sequentially add a KOH solution and a cyanamide aqueous solution, stir, and then add hydrazine hydrate, and continue stirring to react; the mass of the deionized water is 100-1000 times the mass of the polyoxometalate; the volume (mL) of the KOH solution is 5-50 times the mass (g) of the polyoxometalate, and the concentration of the KOH solution is 1-5M; the volume (mL) of the cyanamide aqueous solution is 5-50 times the mass (g) of the polyoxometalate, and the concentration of the cyanamide aqueous solution is 1-5M; sequentially add the KOH solution and the cyanamide aqueous solution, and stir for 3 minutes to ensure sufficient reaction; the volume (mL) of the hydrazine hydrate is 10-80 times the mass (g) of the polyoxometalate; and continue stirring the reaction for 0.5-3 hours;

[0040] Step 202: centrifuge the system after the reaction, wash, centrifuge again, and freeze-dry to obtain a Cu2NCN / POM composite material.

[0041] The method for preparing the Cu2NCN / POM composite material of the present invention preferably comprises the following steps: CuCl2·2H2O and polyoxometalate in a mass ratio of 1:(0.1-1) are reacted with an alkaline cyanamide aqueous solution in the presence of hydrazine hydrate for 0.5-3 hours under stirring, so as to form a nanoflower structure with a clear interface between Cu2NCN and POM and a stable Cu2NCN crystal phase.

[0042] On the other hand, a sodium ion battery is provided, comprising the above-mentioned sodium ion battery negative electrode material.

[0043] The present invention has been subjected to a series of experiments before the application is filed. Some of the experimental results are listed below to further describe the invention in detail, and the following embodiments are used to describe the invention in detail.

[0044] Example 1

[0045] This embodiment provides a sodium ion battery negative electrode material, comprising a porous material and a heterogeneous electron accepting material composited with the porous material, wherein the porous material is Cu2NCN and the heterogeneous electron accepting material is a polyoxometalate.

[0046] This embodiment also provides a method for preparing the above-mentioned sodium ion battery negative electrode material, comprising:

[0047] Step 1: Provide polyoxometalate Ni4(H2O)2(PW9O 34 )2] 10-,include:

[0048] Step 101: Dissolve 17.81 g of Na2WO4·2H2O, 1.61 g of NaHPO4·7H2O, and 3.48 g of Ni(NO3)2·6H2O in 50 mL of deionized water, and adjust the pH to 7.0 with hydrochloric acid to obtain a light green suspension.

[0049] Step 102, reflux the light green suspension at 100° C. for 2 hours;

[0050] Step 103: After the reaction is completed, the precipitate is removed by filtration, and 20 g of sodium chloride is added to the filtrate to promote crystallization;

[0051] Step 104: Recrystallize the crystalline product in 50 mL of hot water to purify it to obtain a light green product, which is recorded as POM;

[0052] Step 2: mixing the polyoxometalate with a porous material source solution, inducing self-assembly under alkaline conditions, and synthesizing a Cu2NCN / POM composite material, comprising:

[0053] Step 201: Dissolve 426.6 mg of CuCl2·2H2O and 100 mg of the POM in 45 mL of deionized water at room temperature, then add 2.5 mL of a 3.5 M KOH solution and 3 mL of a 2 M cyanamide aqueous solution in sequence. After stirring for 3 minutes, quickly add 5 mL of hydrazine hydrate, and continue stirring to react for 2 hours.

[0054] Step 202: centrifuge the reaction product, wash with deionized water, centrifuge again, and freeze-dry to obtain a Cu2NCN / POM composite material.

[0055] Comparative Example 1

[0056] This comparative example examines the effect of POM bonding mode on the structure and performance of sodium ion battery negative electrode materials. The preparation method is as follows:

[0057] Step 1: Provide polyoxometalate Ni4(H2O)2(PW9O 34 )2] 10- ,include:

[0058] Step 101: Dissolve 17.81 g of Na2WO4·2H2O, 1.61 g of NaHPO4·7H2O, and 3.48 g of Ni(NO3)2·6H2O in 50 mL of deionized water, and adjust the pH to 7.0 with hydrochloric acid to obtain a light green suspension.

[0059] Step 102, reflux the light green suspension at 100° C. for 2 hours;

[0060] Step 103: After the reaction is completed, the precipitate is removed by filtration, and 20 g of sodium chloride is added to the filtrate to promote crystallization;

[0061] Step 104: Recrystallize the crystalline product in 50 mL of hot water to purify it to obtain a light green product, which is recorded as POM;

[0062] Step 2: Providing Cu2NCN, including:

[0063] Step 201: Dissolve 426.6 mg of CuCl2·2H2O in 45 mL of deionized water at room temperature, then add 2.5 mL of 3.5 M KOH solution and 3 mL of 2 M cyanamide aqueous solution in sequence. After stirring for 3 minutes, quickly add 5 mL of hydrazine hydrate and continue stirring to react for 2 hours.

[0064] Step 202: centrifuging the reaction product, washing with deionized water, centrifuging again, and freeze-drying to obtain Cu2NCN;

[0065] Step 3: Evenly mix the POM described in step 1 and the Cu2NCN described in step 2 at a mass ratio of 1:1 to obtain a POM and Cu2NCN composite material.

[0066] Comparative Example 2

[0067] This comparative example provides a method for preparing a polyoxometalate, comprising:

[0068] Step 1: Dissolve 17.81 g of Na2WO4·2H2O, 1.61 g of NaHPO4·7H2O, and 3.48 g of Ni(NO3)2·6H2O in 50 mL of deionized water, and adjust the pH to 7.0 with hydrochloric acid to obtain a light green suspension.

[0069] Step 2: reflux the light green suspension at 100° C. for 2 hours;

[0070] Step 3: After the reaction is completed, filter to remove the precipitate, and add 20g of sodium chloride to the filtrate to promote crystallization;

[0071] Step 4: Recrystallize the crystalline product in 50 mL of hot water and purify it to obtain a light green product, which is POM.

[0072] Performance evaluation

[0073] 1. Structure and performance evaluation of sodium ion battery anode materials

[0074] The scanning electron microscope images of the Cu2NCN obtained in step 2 of Example 1 and Comparative Example 1 are as follows: Figure 3 As shown, it can be seen that the Cu2NCN obtained in step 2 of comparative example 1 is a dispersed nanosheet ( Figure 3 a), at small scale ( Figure 3 b) It can be observed that the nanosheets are irregularly arranged with unclear edges. The Cu2NCN / POM composite material of Example 1 is a nanoflower structure ( Figure 3 c), at small scales ( Figure 3 d) It can be observed that the petal-shaped nanosheets aggregate to form a nanoflower structure. The petal layer is about 1.7 nm thick and the overall thickness is uniform. Example 1 Element surface scanning imaging of sodium ion battery negative electrode material is shown in Figure 2. Figure 4 As shown, Cu, N and C elements come from Cu2NCN, and P, W and Ni elements come from POM, indicating that the present invention successfully prepares the Cu2NCN / POM composite material.

[0075] Figure 5 a is the XRD pattern of the sodium ion battery negative electrode material in Example 1, wherein the Cu2NCN spectrum is the spectrum of Cu2NCN prepared according to step 2 of Comparative Example 1. It can be seen that, compared with the Cu2NCN standard card, both the Cu2NCN / POM of Example 1 and the Cu2NCN of Comparative Example 1 have obvious peaks belonging to Cu2NCN, indicating that the Cu2NCN structure is generated and the crystallinity is good. Figure 5 b is the FTIR spectrum, with the peak at 2196 cm in Cu2NCN and Cu2NCN / POM. -1 , 2135 cm -1 、1185 cm -1 and 1998 cm -1 The characteristic peak at 1034 cm-1 in Cu2NCN / POM is attributed to cuprous cyanamide. -1 , 940 cm -1 and 887 cm -1 The characteristic peaks belong to POM, combined with the high-resolution transmission electron microscopy of the sodium ion battery negative electrode material in Example 1 ( Figure 5 c) It can be seen that there is a clear contact interface between Cu2NCN and POM in the Cu2NCN / POM of Example 1 (before cycling), and clear lattice fringes belonging to the (021) crystal plane appear in Cu2NCN, which is consistent with the XRD diffraction pattern ( Figure 5 a) Combined with the above, it can be seen that the Cu2NCN in the negative electrode material has good crystallinity. Figure 5 Figure d is a high-resolution transmission electron microscopy image of Cu2NCN / POM after 2000 cycles. Clear crystal plane stripes can still be observed in Cu2NCN. It can be seen that Cu2NCN / POM still has a stable crystal phase and structure after long cycles, indicating that the negative electrode material of the present invention is structurally stable during long charge and discharge cycles.

[0076] The method for assembling a button-type sodium half-cell using the sodium ion battery negative electrode material of Example 1 as a working electrode and a sodium foil as a counter electrode comprises: using the sodium ion battery negative electrode material of Example 1 as an active material, mixing it with Super P and sodium alginate in a mass ratio of 8:1:1, and then placing it in deionized water to prepare an anode slurry; coating the anode slurry on a copper foil, vacuum drying it at 90°C for 12 h, and punching it into a disc with a diameter of 12 mm, wherein the active material loading amount is 1.2 mgcm -2 The wafer was transferred to an argon atmosphere glove box, and sodium foil was used as the counter electrode, glass fiber GF / D was used as the separator, and 1.0 M sodium hexafluorophosphate DEGDME solution was used as the electrolyte. The charge-discharge cycle and constant current intermittent titration technique (GITT) test were performed using the LAND-CT2001A test system. In the GITT test, 100 mA g -1 The electrochemical performance was tested by CHI760E electrochemical workstation (Shanghai Chenhua) with a pulse current of 10 minutes and a relaxation of 40 minutes. Figure 6 As shown in Figure 2, it can be seen that during the 2000 cycles, the specific capacity of the battery corresponding to Example 1 remains stable at ~300 mAh·g -1 In the second step of comparative example 1, pure Cu2NCN is used as the negative electrode material, and the corresponding battery is from the initial ~180 mAh·g -1 Reduced to ~30 mAh·g -1 It can be seen that the battery cycle stability of the sodium ion battery negative electrode material of Example 1 is higher. After 2000 cycles, the battery capacity retention rate of pure Cu2NCN is 17.10%, and the battery capacity retention rate of the Cu2NCN / POM composite material of Example 1 is as high as 99.93%, which has significantly improved long-cycle stability. It shows that the Cu2NCN / POM composite material prepared by the method of the present invention can significantly accelerate the charge and discharge kinetic reaction process and improve the specific capacity and cycle performance of the battery. Figure 7 This is a schematic diagram of the electrochemical performance test results of the battery corresponding to the POM and Cu2NCN composite materials of Comparative Example 1 at different rates. It can be seen that the capacity of the battery corresponding to the POM and Cu2NCN composite materials of Comparative Example 1 is retained at about 85.3% after 80 cycles at a rate of 0.1C~5C, and its rate performance and reversibility are poor, indicating that the POM and Cu2NCN composite materials prepared by physical mixing are difficult to support stable battery cycling as negative electrode materials.

[0077] Figure 8 The electrochemical CV curve of the battery obtained by assembling POM in comparative example 2 shows that POM has no capacity under the test conditions. Figure 6 and Figure 8It can be seen that the negative electrode material obtained by the preparation method of the present invention has a battery long cycle capacity retention rate of more than 99.3%, which is significantly higher than POM or Cu2NCN, indicating that the composite material with partitioned ion transmission paths and electron conduction paths obtained by the method of the present invention can significantly improve the electrochemical performance of the negative electrode material.

Claims

1. A sodium ion battery negative electrode material, characterized in that It includes a porous material and a heterogeneous electron-accepting material composited with the porous material; the porous material is a transition metal compound crystal material Cu2NCN, and the heterogeneous electron-accepting material is a polyoxometalate; the composite includes hydrolyzing the heterogeneous electron-accepting material under alkaline conditions to induce self-assembly with the porous material; the sodium ion battery negative electrode material morphology is a nanoflower, and the petal layer thickness of the nanoflower is 1.5~2.0 nm.

2. The sodium ion battery negative electrode material according to claim 1, characterized in that The polyoxometalate topological framework is Keggin type.

3. A method for preparing the negative electrode material for a sodium ion battery according to any one of claims 1 to 2, characterized in that: include: providing polyoxometalates; The polyoxometalate is mixed with a porous material source solution, the system is adjusted to be alkaline, and the reaction is stirred at room temperature to obtain a sodium ion battery negative electrode material.

4. The method according to claim 3, characterized in that The polyoxometalates provided specifically include: Step 101, dissolving Na2WO4·2H2O, NaHPO4·7H2O and Ni(NO3)2·6H2O in deionized water, and adjusting the pH to 6-8 with hydrochloric acid to obtain a light green suspension; Step 102, refluxing the light green suspension; Step 103: After the reflux is completed, the mixture is filtered and the filtrate is crystallized to obtain polyoxometalate.

5. The method according to claim 4, characterized in that In step 101, the mass ratio of Na2WO4·2H2O, NaHPO4·7H2O and Ni(NO3)2·6H2O is 1:(0.02-0.2):(0.05-0.5); and / or, in step 102, the reflux temperature is 80-100°C, and the reflux time is 0.5-5 h.

6. The method according to claim 3, characterized in that The polyoxometalate is mixed with a porous material source solution, the system is adjusted to be alkaline, and the reaction is stirred at room temperature to obtain a sodium ion battery negative electrode material, which specifically includes: Step 201: Dissolve CuCl2·2H2O and the polyoxometalate in deionized water at room temperature, then sequentially add KOH solution and cyanamide aqueous solution, stir, then add hydrazine hydrate, and continue stirring to react; Step 202: centrifuge the system after the reaction, wash, centrifuge again, and freeze-dry to obtain a negative electrode material for a sodium ion battery.

7. The method according to claim 6, characterized in that In step 201, the mass ratio of CuCl2·2H2O to the polyoxometalate is 1:(0.1-1); and / or, in step 201, the mass of the deionized water is 100-1000 times the mass of the polyoxometalate; and / or, in step 201, the volume of the KOH solution is 5-50 times the mass of the polyoxometalate, the volume unit of the KOH solution is mL, the mass unit of the polyoxometalate is g, and the concentration of the KOH solution is 1-5 M; and / or, in step 201, the volume of the cyanamide aqueous solution is 5-50 times the mass of the polyoxometalate, the volume unit of the cyanamide aqueous solution is mL, the mass unit of the polyoxometalate is g, and the concentration of the cyanamide aqueous solution is 1-5 M; and / or, in step 201, the volume of the hydrazine hydrate is 10 to 80 times the mass of the polyoxometalate, the volume of the hydrazine hydrate is in mL, and the mass unit of the polyoxometalate is in g; and / or, in step 201, the stirring reaction is continued for 0.5 to 3 h.

8. A sodium ion battery, characterized in that: The invention comprises the sodium ion battery negative electrode material according to any one of claims 1 to 2.

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