Composite sodium supplement as well as preparation method and application thereof

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to a composite sodium supplementing agent as well as a preparation method and application thereof. The composite sodium supplementing agent comprises a metal-organic framework / covalent-organic framework hybrid material and sodium oxalate nanoparticles dispersed in the metal-organic framework / covalent-organic framework hybrid material. The metal-organic framework / covalent-organic framework hybrid material in the composite sodium supplementing agent provided by the invention has an efficient conductive channel and photocatalytic characteristics, and can reduce the sodium removal energy barrier of sodium oxalate through visible light irradiation, so that the sodium removal voltage of the composite sodium supplementing agent is reduced, more active sodium is released, the utilization efficiency of sodium oxalate is effectively improved, and the service life of the composite sodium supplementing agent is prolonged. The composite sodium supplementing agent is applied to the sodium-ion battery, visible light is used for irradiating a positive electrode for sodium removal in the first charging process, the energy density of the sodium-ion battery can be effectively improved, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion batteries, and in particular to a composite sodium supplement agent, a preparation method thereof, and an application thereof. Background Art

[0002] During the first charging process of sodium-ion batteries, there is the same problem as that of lithium-ion batteries, that is, the formation of the SEI film, resulting in a large irreversible loss of active sodium, thereby causing a decrease in Coulombic efficiency. Therefore, it is urgent to explore a suitable sodium supplement method to compensate for the irreversible loss of active sodium in the first cycle.

[0003] At present, the sodium supplement methods are divided into positive electrode sodium supplement method, negative electrode sodium supplement method, separator sodium supplement method, etc. Among them, adding a sodium supplement agent to the positive electrode has simple operation and good sodium supplement effect, and has better development prospects. Currently, the positive electrode sodium supplement agents used more in the industry include sodium carbonate, sodium oxalate, and sodium squarate, etc., but these sodium supplement agents all have some problems, resulting in inability to be industrially applied. For example, the actual capacity of sodium carbonate is small; although the initial sodium deintercalation voltage (3.7V) of sodium squarate is suitable for the working voltage of sodium-ion batteries, its synthesis is difficult and the price is expensive; sodium oxalate is cheap, but its initial sodium deintercalation voltage is too high (4.2V), higher than the working voltage of sodium-ion batteries (generally <3.8V), and it cannot play a role.

[0004] Therefore, it is desired to provide a new positive electrode sodium supplement agent. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a composite sodium supplement agent, a preparation method thereof, and an application thereof. In the composite sodium supplement agent provided by the present invention, the metal-organic framework / covalent-organic framework hybrid material has efficient conductive channels and photocatalytic characteristics. Under visible light irradiation, it can reduce the sodium deintercalation energy barrier of sodium oxalate, thereby reducing the sodium deintercalation voltage of the composite sodium supplement agent, releasing more active sodium, effectively improving the utilization efficiency of sodium oxalate. Applying this composite sodium supplement agent to sodium-ion batteries and using visible light to irradiate the positive electrode for sodium deintercalation during the first charging process can effectively improve the energy density of sodium-ion batteries and reduce costs.

[0006] In a first aspect, the present invention provides a composite sodium supplement agent, which comprises a metal-organic framework / covalent-organic framework hybrid material and sodium oxalate nanoparticles dispersed therein.

[0007] The metal-organic framework / covalent-organic framework hybrid material in the composite sodium supplement provided by the present invention has efficient conductive channels and photocatalytic properties. Under visible light irradiation, it can reduce the sodium deintercalation energy barrier of sodium oxalate, thereby reducing the sodium deintercalation voltage of the composite sodium supplement, releasing more active sodium, effectively improving the utilization efficiency of sodium oxalate. Applying this composite sodium supplement to sodium-ion batteries and using visible light to irradiate the positive electrode during the first charging process for sodium deintercalation can effectively improve the energy density of sodium-ion batteries and reduce costs. Specifically:

[0008] The composite sodium supplement provided by the present invention includes a metal-organic framework / covalent-organic framework hybrid material and sodium oxalate nanoparticles dispersed therein. Sodium oxalate is tightly combined with the metal-organic framework / covalent-organic framework hybrid material (MOF-COF hybrid material) and is evenly distributed in the MOF-COF hybrid material framework. Among them, the MOF-COF hybrid material combines the advantages of MOF hybrid materials and COF hybrid materials. The heterojunction connected by covalent bonds expands the visible light response range, promotes the migration and separation of photo-generated carriers, greatly improves the photocatalytic activity, has excellent visible light response and well-matched band gaps. Moreover, due to the existence of its framework structure, it also has efficient conductive channels. After being irradiated by visible light, it can reduce the sodium deintercalation energy barrier of sodium oxalate, thereby reducing the sodium deintercalation voltage of the composite sodium supplement to release more active sodium, effectively improving the utilization efficiency of sodium oxalate. Furthermore, applying this composite sodium supplement to sodium-ion batteries and using visible light to irradiate the positive electrode during the first charging process for sodium deintercalation can effectively improve the energy density of sodium-ion batteries. In addition, the composite sodium supplement provided by the present invention has uniform composition, stable structure, obvious catalytic effect, low cost, has the characteristic of low sodium deintercalation voltage, has high versatility in the field of sodium-ion batteries, is applicable to different types of sodium battery positive electrode materials, and helps to promote the industrialization and rapid development of sodium battery positive electrode materials.

[0009] As a preferred technical solution of the present invention, the metal-organic framework / covalent-organic framework hybrid material is selected from NH2-UiO-66 / TpPa-1-COF.

[0010] When the metal-organic framework / covalent-organic framework hybrid material is NH2-UiO-66 / TpPa-1-COF, it can be more tightly combined with sodium oxalate, and has more efficient conductive channels and photocatalytic properties. After being irradiated by visible light, it can more effectively reduce the sodium deintercalation energy barrier of sodium oxalate, thereby reducing the sodium deintercalation voltage of the composite sodium supplement to release more active sodium, effectively improving the utilization efficiency of sodium oxalate, and more effectively improving the energy density of the visible light-irradiated sodium-ion battery.

[0011] As a preferred technical solution of the present invention, based on the total mass of the composite sodium supplement being 100%, the content of the metal-organic framework / covalent-organic framework hybrid material is 0.1-1%, such as 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, etc., and the content of the sodium oxalate nanoparticles is 99-99.9%, such as 99%, 99.2%, 99.4%, 99.6%, 99.8%, 99.9%, etc.

[0012] As a preferred technical solution of the present invention, the D50 particle size of the composite sodium supplement is 50-500 nm, such as 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc.

[0013] In a second aspect, the present invention provides a preparation method of the composite sodium supplement described in the first aspect, and the preparation method includes:

[0014] Mix the metal-organic framework / covalent-organic framework hybrid material, sodium oxalate, dispersant and solvent evenly, and perform spray drying to obtain the composite sodium supplement.

[0015] In the preparation method provided by the present invention, due to the nano-scale insoluble size of the metal-organic framework / covalent-organic framework hybrid material, it can provide nucleation sites for sodium oxalate during the spraying process, enabling sodium oxalate to precipitate from the solution and grow by coating on the surface of its framework. As a result, the prepared composite sodium supplement has a stable structure and uniform composition, and the preparation method of the present invention has a simple process and can achieve mass production.

[0016] As a preferred technical solution of the present invention, the dispersant is selected from any one or more of polyethylene, pyrrolidone, polyethylene glycol or polyacrylic acid.

[0017] As a preferred technical solution of the present invention, the mass ratio of the dispersant to the metal-organic framework / covalent-organic framework hybrid material is 1-10:100, such as 1:100, 2:100, 4:100, 6:100, 8:100, 10:100, etc.

[0018] As a preferred technical solution of the present invention, the solvent is selected from deionized water.

[0019] As a preferred technical solution of the present invention, the method of mixing evenly is sand grinding, and the sand grinding time is 200-600 min, such as 200 min, 240 min, 300 min, 360 min, 420 min, 480 min, 540 min, 600 min, etc.

[0020] As a preferred technical solution of the present invention, the particle size of the mixed slurry obtained after sanding is 50 - 500 nm, such as 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc.

[0021] As a preferred technical solution of the present invention, the temperature of the spray drying is 120 - 200 °C, such as 120 °C, 140 °C, 160 °C, 180 °C, 200 °C, etc., and the time of the spray drying is 4 - 12 h, such as 4 h, 6 h, 8 h, 10 h, 12 h, etc.

[0022] When the temperature and time of the spray drying are within the above ranges, sodium oxalate can be more evenly deposited on the surface of the framework of the MOF-COF hybrid material after precipitation from the solution, so that the structure of the prepared composite sodium supplement agent is more stable and uniform.

[0023] In a third aspect, the present invention provides the application of the composite sodium supplement agent described in the first aspect or the composite sodium supplement agent prepared by the preparation method described in the second aspect in a positive electrode sheet.

[0024] In a fourth aspect, the present invention provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector. The composition of the positive electrode active material layer includes the composite sodium supplement agent described in the first aspect or the composite sodium supplement agent prepared by the preparation method described in the second aspect, and the positive electrode current collector is selected from a transparent conductive oxide film.

[0025] The positive electrode sheet provided by the present invention uses a transparent conductive oxide film (TCO film) as the positive electrode current collector, which has good light transmittance and conductivity, facilitating subsequent visible light irradiation for sodium supplementation in a sodium ion battery.

[0026] As a preferred technical solution of the present invention, the composition of the positive electrode active material layer further includes a positive electrode active substance, and the positive electrode active substance is selected from any one or more of sodium iron pyrophosphate, sodium vanadium phosphate, and sodium ferrate.

[0027] As a preferred technical solution of the present invention, the mass ratio of the composite sodium supplement agent to the positive electrode active substance is 0.5 - 10:100, such as 0.5:100, 1:100, 2:100, 4:100, 6:100, 8:100, 10:100, etc.

[0028] In a fifth aspect, the present invention provides a sodium ion battery, which includes the positive electrode sheet described in the fourth aspect.

[0029] As a preferred technical solution of the present invention, the sodium-ion battery further includes a positive electrode housing, and the material of the positive electrode housing is selected from polymethyl methacrylate (acrylic).

[0030] The material of the positive electrode housing provided by the present invention has light transmittance, which is convenient for subsequent visible light irradiation to supplement sodium in the sodium-ion battery.

[0031] In a sixth aspect, the present invention provides a method for supplementing sodium in a sodium-ion battery as described in the fifth aspect. The method for supplementing sodium includes: during the first charging process of the sodium-ion battery, irradiating the positive electrode of the sodium-ion battery with visible light to cause the composite sodium supplementing agent to de-sodium and achieve sodium supplementation.

[0032] In the method for supplementing sodium provided by the present invention, the positive electrode of the sodium-ion battery is first charged under visible light irradiation, which stimulates the photocatalytic performance of the MOF-COF material in the composite sodium supplementing agent, reduces the decomposition voltage of sodium oxalate, releases more active sodium ions, and thus achieves an excellent sodium supplementation effect and effectively improves the first-cycle discharge capacity.

[0033] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art:

[0034] The metal-organic framework / covalent-organic framework hybrid material in the composite sodium supplementing agent provided by the present invention has efficient conductive channels and photocatalytic characteristics. After being irradiated with visible light, it can reduce the sodium de-sodium energy barrier of sodium oxalate, thereby reducing the de-sodium voltage of the composite sodium supplementing agent, releasing more active sodium, effectively improving the utilization efficiency of sodium oxalate. Applying this composite sodium supplementing agent to a sodium-ion battery and irradiating the positive electrode with visible light during the first charging process for de-sodium can effectively improve the energy density of the sodium-ion battery and reduce costs. Description of the Drawings

[0035] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments consistent with the present invention and used together with the specification to explain the principles of the present invention.

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0037] Figure 1 Charge curves of half-cells assembled with sodium supplementing agents prepared in Example 1 and Comparative Examples 1-4.

[0038] Figure 2 Charge-discharge curves of full-cells assembled with positive electrode sheets prepared in Application Example 1 and Comparative Application Examples 1-4. Detailed implementation mode

[0039] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the solution of the present invention will be further described below. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0040] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0041] Example 1

[0042] This example provides a compound sodium supplement and a preparation method thereof. The preparation method includes the following steps:

[0043] Disperse sodium oxalate, NH2-UiO-66 / TpPa-1-COF nanomaterial and polyethylene in deionized water to obtain a mixed slurry. Among them, the mass ratio of sodium oxalate to NH2-UiO-66 / TpPa-1-COF nanomaterial is 0.99:0.01, and the mass ratio of the dispersant polyethylene to NH2-UiO-66 / TpPa-1-COF nanomaterial is 3:100; sand the mixed slurry for 480 min to obtain a mixed slurry with a D50 of about 100 nm, and spray-dry the mixed slurry at 120 °C for 12 h to obtain the compound sodium supplement.

[0044] Example 2

[0045] This example provides a compound sodium supplement and a preparation method thereof. The preparation method includes the following steps:

[0046] Disperse sodium oxalate, NH2-UiO-66 / TpPa-1-COF nanomaterial and polyethylene glycol in deionized water to obtain a mixed slurry. Among them, the mass ratio of sodium oxalate to NH2-UiO-66 / TpPa-1-COF nanomaterial is 0.995:0.005, and the mass ratio of the dispersant polyethylene glycol to NH2-UiO-66 / TpPa-1-COF nanomaterial is 2:100; sand the mixed slurry for 360 min to obtain a mixed slurry with a D50 of about 200 nm, and spray-dry the mixed slurry at 140 °C for 8 h to obtain the compound sodium supplement.

[0047] Example 3

[0048] This example provides a compound sodium supplement and a preparation method thereof. The preparation method includes the following steps:

[0049] Sodium oxalate, NH2-UiO-66 / TpPa-1-COF nanomaterial and pyrrolidone were dispersed in deionized water to obtain a mixed slurry. The mass ratio of sodium oxalate to NH2-UiO-66 / TpPa-1-COF nanomaterial was 0.997:0.003, and the mass ratio of the dispersant pyrrolidone to NH2-UiO-66 / TpPa-1-COF nanomaterial was 3:100. The mixed slurry was sanded for 420 min to obtain a mixed slurry with a D50 of about 150 nm. The mixed slurry was spray-dried at 200 °C for 4 h to obtain the composite sodium supplement agent.

[0050] Example 4

[0051] This example provides a composite sodium supplement agent and a preparation method thereof. The preparation method includes the following steps:

[0052] Sodium oxalate, NH2-UiO-66 / TpPa-1-COF nanomaterial and polyacrylic acid were dispersed in deionized water to obtain a mixed slurry. The mass ratio of sodium oxalate to NH2-UiO-66 / TpPa-1-COF nanomaterial was 0.999:0.001, and the mass ratio of the dispersant polyacrylic acid to NH2-UiO-66 / TpPa-1-COF nanomaterial was 5:100. The mixed slurry was sanded for 540 min to obtain a mixed slurry with a D50 of about 100 nm. The mixed slurry was spray-dried at 180 °C for 6 h to obtain the composite sodium supplement agent.

[0053] Comparative Example 1

[0054] This comparative example provides a sodium supplement agent and a preparation method thereof. The preparation method includes the following steps:

[0055] Sodium oxalate and polyethylene were dispersed in deionized water to obtain a mixed slurry. The mixed slurry was sanded for 480 min, and the mixed slurry was spray-dried at 120 °C for 12 h to obtain the sodium supplement agent.

[0056] Comparative Example 2

[0057] This comparative example provides a composite sodium supplement agent and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this comparative example, the NH2-UiO-66 / TpPa-1-COF nanomaterial is replaced by TiO2.

[0058] Comparative Example 3

[0059] This comparative example provides a composite sodium supplement agent and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this comparative example, the NH2-UiO-66 / TpPa-1-COF nanomaterial is replaced by NH2-UiO-66.

[0060] Comparative Example 4

[0061] This comparative example provides a composite sodium supplement and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this comparative example, the NH2-UiO-66 / TpPa-1-COF nanomaterial is replaced by TpPa-1-COF.

[0062] Performance Test 1

[0063] 1. Prepare the positive electrode sheets and assemble half-cells using the sodium supplements prepared in the examples and comparative examples respectively:

[0064] Mix the sodium supplements prepared in the examples and comparative examples with Super P, PVDF, and NMP respectively. The mass ratio of the sodium supplement to Super P and PVDF is 80%:10%:10%. Use a TCO film as the positive electrode current collector. Obtain the positive electrode sheets through homogenization, coating, drying, and rolling. Use a sodium metal sheet as the counter electrode, a propylene carbonate solution containing 1M NaClO4 and 5Vol% fluoroethylene carbonate as the electrolyte, a glass fiber as the separator, and select an acrylic material light-transmitting positive electrode case. Assemble a button cell in a glove box under a high-purity argon atmosphere.

[0065] 2. Perform a charging test on the prepared button cell in a voltage window of 2.7 - 4.6V, and irradiate the positive electrode surface with a xenon lamp throughout the first charging process.

[0066] The test results are shown in Table 1 and Figure 1 as follows, where Figure 1 are the charging curves of the half-cells assembled with the sodium supplements prepared in Example 1 and Comparative Examples 1 - 4. The results in Table 1 are as follows:

[0067] Table 1

[0068]

[0069]

[0070] From Table 1 and Figure 1 the results, it can be found that the half-cell assembled with the composite sodium supplement provided by the present invention has a lower charging voltage and a higher charging capacity. This indicates that during the first charging process of the composite sodium supplement provided by the present invention, after being irradiated with visible light, the MOF-COF hybrid material effectively reduces the sodium removal energy barrier of sodium oxalate, thereby reducing the sodium removal voltage of the composite sodium supplement and releasing more active sodium ions, effectively improving the utilization efficiency of sodium oxalate and enhancing the sodium supplement effect.

[0071] Application Example 1

[0072] This application example provides a positive electrode sheet and a preparation method thereof, and uses the composite sodium supplement prepared in Example 1 to prepare the positive electrode sheet.

[0073] Sodium iron pyrophosphate (NFPP), Super P, and PVDF are mixed in a mass ratio of 8:1:1. Additionally, a composite sodium supplement accounting for 2.5% of the mass of sodium iron pyrophosphate is added. Then, the above mixture is mixed with NMP. Using a TCO film as the positive electrode current collector, a positive electrode sheet of sodium iron pyrophosphate is obtained through homogenization, coating, drying, and rolling.

[0074] Application Example 2

[0075] This application example provides a positive electrode sheet and a preparation method thereof. The preparation method is the same as that of Application Example 1. The difference from Application Example 1 is that in this application example, the composite sodium supplement is replaced with the composite sodium supplement prepared in Example 2, and the dosage of the composite sodium supplement is 5% of the mass of sodium iron pyrophosphate.

[0076] Application Example 3

[0077] This application example provides a positive electrode sheet and a preparation method thereof. The preparation method is the same as that of Application Example 1. The difference from Application Example 1 is that in this application example, the composite sodium supplement is replaced with the composite sodium supplement prepared in Example 3, sodium iron pyrophosphate is replaced with sodium vanadium phosphate, and the dosage of the composite sodium supplement is 7.5% of the mass of sodium vanadium phosphate.

[0078] Application Example 4

[0079] This application example provides a positive electrode sheet and a preparation method thereof. The preparation method is the same as that of Application Example 1. The difference from Application Example 1 is that in this application example, the composite sodium supplement is replaced with the composite sodium supplement prepared in Example 4, sodium iron pyrophosphate is replaced with sodium ferrate, and the dosage of the composite sodium supplement is 10% of the mass of sodium vanadium phosphate.

[0080] Comparative Application Example 1

[0081] This comparative application example provides a positive electrode sheet and a preparation method thereof. The preparation method is the same as that of Application Example 1. The difference from Application Example 1 is that in this comparative application example, the composite sodium supplement is replaced with the sodium supplement prepared in Comparative Example 1.

[0082] Comparative Application Example 2

[0083] This comparative application example provides a positive electrode sheet and a preparation method thereof. The preparation method is the same as that of Application Example 1. The difference from Application Example 1 is that in this comparative application example, the composite sodium supplement is replaced with the composite sodium supplement prepared in Comparative Example 2.

[0084] Comparative Application Example 3

[0085] This comparative application example provides a positive electrode sheet and a preparation method thereof. The preparation method is the same as that of Application Example 1. The difference from Application Example 1 is that in this comparative application example, the composite sodium supplement agent is replaced with the composite sodium supplement agent prepared in Comparative Example 3.

[0086] Comparative Application Example 4

[0087] This comparative application example provides a positive electrode sheet and a preparation method thereof. The preparation method is the same as that of Application Example 1. The difference from Application Example 1 is that in this comparative application example, the composite sodium supplement agent is replaced with the composite sodium supplement agent prepared in Comparative Example 4.

[0088] Performance Test 2

[0089] 1. Assemble full cells using the positive electrode sheets prepared in the application examples and comparative application examples respectively:

[0090] Use the positive electrode sheets prepared in the application examples and comparative application examples as the positive electrode sheets respectively, use commercial hard carbon to prepare the negative electrode sheet, use a propylene carbonate solution containing 1M NaClO4 and 5Vol% fluoroethylene carbonate as the electrolyte, use glass fiber as the separator, and select an acrylic material light-transmitting positive electrode shell to assemble full cells in a glove box under a high-purity argon atmosphere.

[0091] 2. Perform electrochemical tests on the prepared full cells in a voltage window of 1.8 - 4.2V, and irradiate the positive electrode surface with a xenon lamp throughout the first charging process.

[0092] The test results are as Figure 2 and shown in Table 2, where Figure 2 are the charge-discharge curves of the full cells assembled with the positive electrode sheets prepared in Application Example 1 and Comparative Application Examples 1 - 4. The results of Table 2 are as follows:

[0093] Table 2

[0094] Sample Charge specific capacity (mAh / g) Discharge specific capacity (mAh / g) Application Example 1 137.00 114.71 Application Example 2 134.32 112.22 Application Example 3 133.57 113.17 Application Example 4 135.06 112.35 Comparative Application Example 1 117.90 108.48 Comparative Application Example 2 118.51 110.21 Comparative Application Example 3 131.65 111.41 Comparative Application Example 4 116.53 103.33

[0095] From Table 2 and Figure 2 the results, it can be found that applying the composite sodium supplement agent provided by the present invention to sodium-ion batteries can effectively improve the energy density of sodium-ion batteries.

[0096] It should be noted that in this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0097] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments described herein, but rather will conform to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A compound sodium supplement, characterized in that, The composite sodium supplement agent includes a metal-organic framework / covalent-organic framework hybrid material and sodium oxalate nanoparticles dispersed therein.

2. The compound sodium supplement according to claim 1, wherein The metal-organic framework / covalent-organic framework hybrid material is selected from NH2-UiO-66 / TpPa-1-COF.

3. The compound sodium supplement according to claim 1 or 2, characterized in that, Based on the total mass of the composite sodium supplement agent being 100%, the content of the metal-organic framework / covalent-organic framework hybrid material is 0.1-1%, and the content of the sodium oxalate nanoparticles is 99-99.9%.

4. The compound sodium supplement according to any one of claims 1-3, characterized in that The D50 particle size of the composite sodium supplement agent is 50-250 nm.

5. The preparation method of the compound sodium supplement according to any one of claims 1-4, characterized in that, The preparation method includes: Mixing the metal-organic framework / covalent-organic framework hybrid material, sodium oxalate, a dispersant and a solvent, and spray drying to obtain the composite sodium supplement agent.

6. The preparation method according to claim 5, characterized in that, The dispersant is selected from any one or more of polyethylene, pyrrolidone, polyethylene glycol or polyacrylic acid; and / or, the mass ratio of the dispersant to the metal-organic framework / covalent-organic framework hybrid material is 1-10:100; and / or, the mixing method is sand grinding, and the sand grinding time is 200-600 min; and / or, the temperature of the spray drying is 120-200 °C, and the spray drying time is 4-12 h.

7. Application of the composite sodium supplement agent according to any one of claims 1-4 or the composite sodium supplement agent prepared by the preparation method according to claim 5 or 6 in a positive electrode tab.

8. A positive electrode plate, characterized in that, The positive electrode tab includes a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector. The composition of the positive electrode active material layer includes the composite sodium supplement agent according to any one of claims 1-4 or the composite sodium supplement agent prepared by the preparation method according to claim 5 or 6, and the positive electrode current collector is selected from a transparent conductive oxide film.

9. A sodium-ion battery, characterized in that, The sodium ion battery includes the positive electrode tab according to claim 8.

10. A method for supplementing sodium in a sodium-ion battery as described in claim 9, characterized in that, The sodium supplement method includes: during the first charging process of the sodium ion battery, irradiating the positive electrode of the sodium ion battery with visible light to cause the composite sodium supplement agent to desodium and achieve sodium supplementation.

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