CN116014355A - Pre-sodium membrane and preparation method thereof - Google Patents
Pre-sodium membrane and preparation method thereof Download PDFInfo
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- CN116014355A CN116014355A CN202310116921.3A CN202310116921A CN116014355A CN 116014355 A CN116014355 A CN 116014355A CN 202310116921 A CN202310116921 A CN 202310116921A CN 116014355 A CN116014355 A CN 116014355A
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/10—Energy storage using batteries
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Abstract
The invention belongs to the field of sodium ion battery diaphragms, and particularly relates to a pre-sodification diaphragm and a preparation method thereof. The pre-sodium membrane provided by the invention can effectively improve the first effect of the sodium ion battery, thereby improving the energy density of the battery and not affecting the processing performance and structure of the positive pole piece. The preparation process is simple, the environmental requirement is low, and the production cost is low.
Description
Technical Field
The invention belongs to the field of sodium ion battery diaphragms, and particularly relates to a pre-sodium-modified diaphragm and a preparation method thereof.
Background
The sodium ion battery has wide application prospect in the fields of energy storage, low-speed vehicles and the like due to the advantages of rich sodium resources, low cost and the like. In the first charge and discharge process of the sodium ion battery, SEI films are generated on the surface of the negative electrode, and other impurities of the positive electrode material have side reactions, so that the first charge and discharge efficiency is low, and the energy density of the battery is reduced.
In order to increase the energy density of the sodium ion battery, it is necessary to supplement sodium to the sodium ion battery to compensate for irreversible sodium loss when the SEI film is formed. The sodium supplementation method commonly used at present is an additive method. The additive method does not need to change the existing production process and is simple and convenient to operate. At present, common positive electrode sodium supplement additives mainly comprise inorganic sodium salts, but the common sodium supplement additives have the problem that solid or gas residues exist after reaction, and the positive electrode structure is influenced.
For example, patent CN111834622a provides a multi-layer sodium ferric sulfate positive electrode sheet with lithium/sodium supplementing function, and a positive electrode material layer and a lithium/sodium supplementing material layer are disposed on both sides of a positive electrode current collector, but the following problems are caused: 1) The processing performance of the positive electrode is poor, and material dropping occurs; 2) The sodium supplement additive leaves a void in the pole piece after the first charge, resulting in non-uniformity of the lithium/sodium supplement material layer and the positive electrode material layer. Patent CN115117558A provides a method for supplementing sodium to a membrane, which transfers a sodium supplementing agent, a binder, a conductive agent and the like to the surface of a base membrane through homogenate coating, although the method can improve the initial effect of a sodium ion battery, the method needs to disperse the conductive agent and the binder, increases the cost for preparing a battery core, and can use an organic solvent, which is harmful to the environment to a certain extent, and after the sodium supplementing additive is decomposed and consumed in the reaction process, the residual conductive agent and the binder on the membrane can influence the air permeability of the membrane, so that the energy density of the battery core is reduced.
Therefore, how to develop a sodium supplementing method to solve the above-mentioned additive problems, so that it is necessary to improve the energy density and the performance of the sodium ion battery.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a pre-sodium-modified diaphragm, which solves the defects of the existing diaphragm, and the pre-sodium-modified active substance compensates for irreversible loss of the first-circle capacity of a sodium ion battery, so that the capacity of a battery core is improved by 3-10%, and the energy density is improved by 3-15%.
In order to achieve the technical purpose, the technical scheme of the invention is as follows:
a pre-sodium membrane is prepared from pre-sodium active substance as surface layer, membrane base membrane as covering carrier, and drying. The pre-sodified membrane is used as a sodium ion battery membrane.
The pre-sodium active substance adopts one or more of inorganic sodium salt, organic sodium salt and sodium oxide.
Further, the pre-sodium active substance adopts Na 2 C 2 O 4 、Na 2 C 4 O 4 、Na 2 C 4 O 6 、Na 2 CO 3 One or more of them.
The diaphragm base film adopts one or more of polyethylene, polypropylene and cellulose.
The preparation method of the pre-sodium membrane comprises the following steps: preparing a pre-sodium active substance into a coating liquid, covering the coating liquid on a diaphragm base film, and drying to obtain the pre-sodium diaphragm.
The coating liquid takes deionized water as a solvent.
The coating liquid is a solution or dispersion of a pre-sodified active material.
The mass ratio of the pre-sodium active substance to the deionized water in the coating liquid is 1:5-100.
The coating liquid contains sodium alginate, and the addition amount of the sodium alginate is 5-10% of the mass of the pre-sodium active substance.
The pre-sodium active material has a thickness of 0.2-2 μm and a coating layer density of 0.05-4mg/cm 2 。
The drying temperature is 45-85deg.C, and the drying time is 5-20min.
From the above description, it can be seen that the present invention has the following advantages:
1. the invention solves the defects of the existing diaphragm, and compensates the irreversible loss of the first-circle capacity of the sodium ion battery by pre-sodium modification of active substances, thereby improving the capacity of the battery core by 3-10% and improving the energy density by 3-15%.
2. According to the invention, sodium alginate is used as adhesion, so that the connectivity of the pre-sodium active substance and the diaphragm base film is effectively improved, the problem of poor connection stability of the pre-sodium active substance is solved, and meanwhile, the sodium alginate has a sodium ion structure and plays a certain sodium ion supplementing effect.
3. The invention utilizes the-COO of sodium alginate - The group shows polyanion characteristic in aqueous solution, has certain viscosity, can prevent the agglomeration and sedimentation of the sodium supplementing agent, improves the stability of the sodium supplementing slurry, and further increases the coating effect;
4. according to the invention, the gel structure of sodium alginate is utilized, a porous structure is formed after the gel structure is coated on the diaphragm and dried, the air permeability of the diaphragm is not affected, and the influence on the sodium ion conduction and the multiplying power of the battery cell is small.
4. The invention can effectively avoid the structural damage of the positive electrode plate caused by directly adding the sodium supplement additive into the positive electrode material, does not influence the processing performance of the positive electrode, and improves the stability of the battery cell.
5. The pre-sodium active substance provided by the invention is completely consumed in the formation process, the quality of a diaphragm and a battery cell is not additionally increased, and the energy density of the battery cell is improved.
6. The pre-sodium membrane provided by the invention takes water as a solvent, is environment-friendly, low in cost, simple in preparation process, low in drying temperature and high in production efficiency.
Drawings
Fig. 1 is a graph showing the charge-discharge gram capacity of half cells of example 1 of the present invention and comparative example 1.
Detailed Description
One embodiment of the present invention is described in detail with reference to fig. 1, but does not limit the claims of the present invention in any way.
Example 1
Pre-sodium treatment of active substance Na 2 C 2 O 4 Mixing with deionized water according to a mass ratio of 1:40, dissolving, adding sodium alginate with the mass of 8% of the pre-sodified active substance, stirring uniformly to obtain a dissolving solution, and then coating the dissolving solution on the surface of a polyethylene-based film with the thickness of 12 mu m in a spraying manner to form a coating, wherein the thickness of the coating is 1.5 mu m, and the areal density is 0.35mg/cm 2 Baking in an oven at 85 ℃ for 20min to obtain the pre-sodified membrane.
And preparing the ferric sodium sulfate positive electrode plate, the prepared pre-sodium membrane and the metal sodium plate into a button cell in sequence, wherein the pre-sodium layer on the membrane faces the positive electrode side, and injecting 20 mu L of electrolyte to obtain the button cell. The solvent of the electrolyte is EC-PC mixed solution with the volume ratio of 1:1, and the solute is sodium hexafluorophosphate with the concentration of 1 mol/L.
Preparing a bare cell from the sodium ferric sulfate positive electrode plate, the prepared pre-sodium membrane and the hard carbon negative electrode plate according to data, arranging the pre-sodium layer on the membrane towards the positive electrode side, placing the bare cell in an aluminum plastic film, injecting electrolyte, packaging and forming to prepare the sodium ion full battery. The solvent of the electrolyte is EC-PC mixed solution with the volume ratio of 1:1, and the solute is sodium hexafluorophosphate with the concentration of 1 mol/L.
Comparative example 1
Preparing a button cell from the ferric sodium sulfate positive pole piece, the 12 mu m polyethylene-based film and the metal sodium piece in sequence, and injecting electrolyte to obtain the button cell. The solvent of the electrolyte is EC-PC mixed solution with the volume ratio of 1:1, and the solute is sodium hexafluorophosphate with the concentration of 1 mol/L.
Preparing a bare cell by using a sodium iron sulfate positive electrode plate, a 12 mu m polyethylene-based film and a hard carbon negative electrode plate according to data, placing the bare cell in an aluminum plastic film, injecting electrolyte, and packaging and forming to prepare the sodium ion full battery. The solvent of the electrolyte is EC-PC mixed solution with the volume ratio of 1:1, and the solute is sodium hexafluorophosphate with the concentration of 1 mol/L.
The first-cycle charging data of the sodium ion button cell prepared in example 1 and comparative example 1 are shown in fig. 1, and as can be seen from fig. 1, the first-cycle charging specific capacity of the button cell in example 1 is obviously better than that of comparative example 1, which shows that the pre-sodium modified diaphragm provided by the invention can contribute a certain gram capacity in the battery formation process.
The first charge and discharge data and cycle data of the sodium ion full cell prepared in example 1 and comparative example 1 are shown in the following table:
as can be seen from table 1, the battery of example 1 has higher first-cycle discharge specific capacity and first effect than those of comparative example 1, and the capacity retention rate after 2000 cycles is also better than that of comparative example 1, which indicates that the pre-sodified separator provided by the invention has good sodium supplementing capability.
Example 2
Pre-sodium treatment of active substance Na 2 C 4 O 4 Mixing and dissolving with deionized water according to a mass ratio of 1:5, adding sodium alginate with the mass of 5% of the pre-sodified active substance, stirring uniformly to obtain a dissolving solution, and then coating the dissolving solution on the surface of a polypropylene-based film with the thickness of 12 mu m in a spraying manner to form a coating, wherein the thickness of the coating is 2 mu m, and the surface density is 4mg/cm 2 Baking in an oven at 45 ℃ for 5min to obtain the pre-sodified membrane.
Preparing a bare cell from the sodium ferric sulfate positive electrode plate, the prepared pre-sodium membrane and the hard carbon negative electrode plate according to data, arranging the pre-sodium layer on the membrane towards the positive electrode side, placing the bare cell in an aluminum plastic film, injecting electrolyte, packaging and forming to prepare the sodium ion full battery. The solvent of the electrolyte is EC-PC mixed solution with the volume ratio of 1:1, and the solute is sodium hexafluorophosphate with the concentration of 1 mol/L.
Example 3
Pre-sodium treatment of active substance Na 2 C 4 O 6 Mixing with deionized water according to a mass ratio of 1:100, dissolving, adding sodium alginate with a mass of 10% of that of the pre-sodified active substance, stirring uniformly to obtain a dissolving solution, and coating the dissolving solution on the surface of a cellulose base film with a thickness of 12 mu m in a spraying manner to form a coating, wherein the thickness of the coating is 2 mu m, and the surface density is 4mg/cm 2 Baking in an oven at 85 ℃ for 20min to obtain the pre-sodified membrane.
Preparing a bare cell from the sodium ferric sulfate positive electrode plate, the prepared pre-sodium membrane and the hard carbon negative electrode plate according to data, arranging the pre-sodium layer on the membrane towards the positive electrode side, placing the bare cell in an aluminum plastic film, injecting electrolyte, packaging and forming to prepare the sodium ion full battery. The solvent of the electrolyte is EC-PC mixed solution with the volume ratio of 1:1, and the solute is sodium hexafluorophosphate with the concentration of 1 mol/L.
Example 4
Pre-sodium treatment of active substance Na 2 CO 3 Mixing with deionized water according to a mass ratio of 1:50, dissolving, adding sodium alginate with the mass of 8% of the pre-sodified active substance, stirring uniformly to obtain a dissolving solution, and coating the dissolving solution on the surface of a polyethylene-based film with the thickness of 12 mu m in a spraying manner to form a coating, wherein the thickness of the coating is 1 mu m, and the surface density is 2mg/cm 2 Baking in an oven at 65 ℃ for 10min to obtain the pre-sodified membrane.
Preparing a bare cell from the sodium ferric sulfate positive electrode plate, the prepared pre-sodium membrane and the hard carbon negative electrode plate according to data, arranging the pre-sodium layer on the membrane towards the positive electrode side, placing the bare cell in an aluminum plastic film, injecting electrolyte, packaging and forming to prepare the sodium ion full battery. The solvent of the electrolyte is EC-PC mixed solution with the volume ratio of 1:1, and the solute is sodium hexafluorophosphate with the concentration of 1 mol/L.
The first charge and discharge data and cycle data of the sodium ion full batteries prepared in examples 1-4 are shown in the following table:
it is to be understood that the foregoing detailed description of the invention is merely illustrative of the invention and is not limited to the embodiments of the invention. It will be understood by those of ordinary skill in the art that the present invention may be modified or substituted for elements thereof to achieve the same technical effects; as long as the use requirement is met, the invention is within the protection scope of the invention.
Claims (10)
1. A pre-sodified membrane, characterized by: and taking the pre-sodiumized active substance as a surface layer, taking a membrane base membrane as a covering carrier, and drying to obtain the pre-sodiumized membrane, wherein the pre-sodiumized membrane is used as a sodium ion battery membrane.
2. The pre-sodified membrane of claim 1, wherein: the pre-sodium active substance adopts one or more of inorganic sodium salt, organic sodium salt and sodium oxide.
3. The pre-sodified membrane of claim 2, wherein: the pre-sodium active substance adopts Na 2 C 2 O 4 、Na 2 C 4 O 4 、Na 2 C 4 O 6 、Na 2 CO 3 One or more of them.
4. The pre-sodified membrane of claim 1, wherein: the diaphragm base film adopts one or more of polyethylene, polypropylene and cellulose.
5. The pre-sodified membrane of claim 1, wherein: the preparation method of the pre-sodium membrane comprises the following steps: preparing a pre-sodium active substance into a coating liquid, covering the coating liquid on a membrane base membrane, and drying to obtain the pre-sodium membrane, wherein the drying temperature is 45-85 ℃ and the drying time is 5-20min.
6. The pre-sodified membrane of claim 5, wherein: the coating liquid takes deionized water as a solvent.
7. The pre-sodified membrane of claim 5, wherein: the coating liquid is a solution or dispersion of a pre-sodified active material.
8. The pre-sodified membrane of claim 5, wherein: the mass ratio of the pre-sodium active substance to the deionized water in the coating liquid is 1:5-10.
9. The pre-sodified membrane of claim 5, wherein: the coating liquid also contains sodium alginate, and the addition amount of the sodium alginate is 5-10% of the mass of the pre-sodium active substance.
10. The pre-sodified membrane of claim 5, wherein: the pre-sodium active material has a thickness of 0.2-2 μm and a coating layer density of 0.05-4mg/cm 2 。
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| CN202310116921.3A CN116014355A (en) | 2023-02-15 | 2023-02-15 | Pre-sodium membrane and preparation method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117352954A (en) * | 2023-12-06 | 2024-01-05 | 天津力神电池股份有限公司 | Sodium-supplementing electrolyte diaphragm, preparation method and battery |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117352954A (en) * | 2023-12-06 | 2024-01-05 | 天津力神电池股份有限公司 | Sodium-supplementing electrolyte diaphragm, preparation method and battery |
| CN117352954B (en) * | 2023-12-06 | 2024-04-19 | 天津力神电池股份有限公司 | Sodium-supplementing electrolyte diaphragm, preparation method and battery |
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