A method for manufacturing a sodium-ion solid-state battery with improved electrochemical performance

Abstract

The application relates to a manufacturing method of a sodium ion solid-state battery with improved electrochemical performance. The specific scheme is as follows: taking a semi-finished product battery, a solid-state electrolyte precursor solution is injected into the battery by adopting a vacuum injection method; the precursor solution is fully infiltrated and a formation process is carried out by adopting a normal-temperature standing + high-temperature standing method; after vacuum pumping and packaging, a separate capacity process is carried out; after charging part of the electric quantity, an initiator solution is injected, then a constant current is applied to the battery to carry out solid-state electrolyte precursor solution polymerization, and after the solid-state electrolyte precursor solution is completed, a finished product solid-state battery is obtained. The application controls the manufacturing process of the solid-state battery and the solid-state electrolyte polymerization condition, controls the battery charge state and voltage, thereby improving the electrochemical performance of the solid-state battery, and solving the problem that the solid-state battery has poor electrochemical performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sodium ion batteries, in particular to a sodium ion solid-state battery manufacturing method for improving electrochemical performance. BACKGROUND

[0002] Due to the scarcity of lithium resources, the cost of lithium ion battery related energy storage materials is high, and sodium ion batteries have been widely concerned in recent years due to their wide range of raw materials and high cost performance. At present, most sodium ion batteries use flammable organic electrolyte and high-temperature shrinkable polyolefin separators, which provide high ionic conductivity, but also have safety problems such as electrolyte leakage and flammability. Solid-state batteries use solid electrolytes instead of traditional organic liquid electrolytes, and some types of solid-state batteries do not use polyolefin separators, which have good safety performance and high energy density, and are ideal chemical power sources.

[0003] Although solid-state batteries have the advantage of improving battery safety performance, the current solid-state sodium ion battery uses solid-state electrolyte, which has a certain influence on the formation of SEI film, which will lead to poor interface performance between the electrolyte and the electrode, resulting in the electrochemical performance of the solid-state battery being affected. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art and provide a sodium ion solid-state battery manufacturing method for improving electrochemical performance.

[0005] The technical scheme for achieving the purpose of the present application is to provide a sodium ion solid-state battery manufacturing method for improving electrochemical performance, comprising the following steps:

[0006] S1, taking polymer monomer material, solvent, sodium salt and initiator, uniformly stirring by magnetic stirring, to prepare a solid-state electrolyte precursor solution;

[0007] S2, taking a semi-finished battery, and injecting the solid-state electrolyte precursor solution into the battery by vacuum injection;

[0008] S3, the solid-state battery prepared in step S2 is placed at room temperature to allow the precursor solution to fully soak;

[0009] S4, the solid-state battery after room temperature standing in step S3 is installed on a clamp and subjected to high temperature standing to allow the precursor solution to further soak, and after cooling, a formation process is performed;

[0010] S5, the solid-state battery after formation in step S4 is removed from the clamp and placed for 6-8h, and after vacuum pumping and packaging, a capacity distribution process is performed;

[0011] S6. After partially charging the solid-state battery obtained from step S5, let it stand for 6-12 hours until the battery reaches a steady state, and then measure the internal resistance R1 of the battery.

[0012] S7. After magnetically stirring the initiator, sodium salt, and solvent until uniform, an initiator solution is obtained. The initiator solution is then injected into the solid-state battery obtained in step S6 and left to stand at room temperature for 12 hours.

[0013] S8. After installing the fixture, the solid battery obtained in step S7 is connected to the charge / discharge machine, a constant current is applied, and the solid battery is electrocatalyzed. By controlling the constant voltage, the solid electrolyte precursor solution is polymerized to form a solid electrolyte.

[0014] S9. After the solid electrolyte is formed, let it stand at room temperature for 4-8 hours, then remove the fixture and perform a second sealing process. After extracting the gas generated by polymerization, the finished solid battery is obtained.

[0015] S10. Test the solid-state battery capacity. After the capacity test is completed, charge the battery with the same amount of power as after capacity grading. Let it stand for 6-12 hours until the battery reaches a steady state. Then, measure the internal resistance R2 of the battery and calculate ΔR.

[0016] As a further improvement, the semi-finished battery described in S2 is made by Z-shaped stacking process of positive electrode sheet, negative electrode sheet and polyolefin separator, and then welded tabs and aluminum-plastic film encapsulation.

[0017] As a further improvement, the solid electrolyte precursor solution described in S1 includes polymer monomer material, solvent, sodium salt, and initiator, wherein the polymer monomer material and solvent are in a mass ratio of (30%-70%):(30%-70%), the sodium salt concentration is 1 mol / L-1.5 mol / L, and the initiator content is 0.3 wt.%-0.6 wt.% of the polymer monomer material.

[0018] As a further improvement, the amount of initiator used in S7 is the same as the amount of initiator in the precursor solution in S1.

[0019] As a further improvement, the room temperature standing parameters in S3 are 25℃ for 24-48 hours, and the high temperature standing parameters in S4 are 40-50℃ for 12-24 hours.

[0020] As a further improvement, the formation process described in S4 uses a clamping plate to apply a certain pressure to the battery during the formation process, so that the interface can make full contact and effectively form an SEI film. The charge during the formation process is controlled at 40%-60% of the rated capacity, and the formation charging current is charged in a multi-stage, current-increasing manner.

[0021] As a further improvement, the range of charge capacity after battery capacity grading in S6 is 10%-60% of the rated capacity.

[0022] As a further improvement, the solid electrolyte precursor polymerization described in S8 is carried out by electrocatalysis, and the battery is polymerized using a constant current, wherein the constant current is 0.001-0.003C.

[0023] As a further improvement, the capacity detection in S10 is performed by charging with a multi-stage current. First, the battery is activated by charging at 0.005C for 6 hours. Then, it is charged sequentially at 0.01C for 2 hours, 0.05C for 2 hours, and 0.1C until the battery is fully charged. Finally, the battery is discharged at a constant current of 0.1C to detect the battery capacity.

[0024] As a further improvement, the ΔR value mentioned in S10 is used as a criterion for determining solid-state batteries, and the calculation method is ΔR = R2 - R1.

[0025] After adopting the above technical solution, the present invention has the following positive effects:

[0026] (1) In the battery polymerization process of this invention, the volume of the electrolyte system shrinks during polymerization, applying a certain pressure to the battery, which can shorten the distance between molecules and is beneficial to the polymerization of solid electrolyte. Since solid electrolyte is a solid material, it may lead to poor formation of SEI film during the formation process. By performing the formation process of solid electrolyte in the form of precursor solution first, the negative electrode SEI film can be formed stably. In addition, since sodium-ion batteries generate a certain amount of gas during the formation and capacity testing process, performing the formation and capacity testing process first can remove the gas in advance, allowing the solid electrolyte precursor solution to be more immersed in the electrode, which is beneficial to the interfacial contact between the electrode and the solid electrolyte after the solid electrolyte is formed. If the solid electrolyte is formed by polymerization first and then the formation and capacity testing process is performed, the generated gas will be discharged through the solid electrolyte, resulting in pores in the solid electrolyte. This causes discontinuity between some solid electrolytes, affecting the transport of sodium ions in the solid electrolyte. Furthermore, the uneven distribution of solid electrolyte due to pores will lead to poor interfacial stability between the solid electrolyte and the electrode, thereby affecting the electrochemical performance of the battery.

[0027] (2) The initiator in this invention is added in two parts. The first part is added to the solid electrolyte precursor solution, and the second part is added before polymerization. By adding it in two parts, the efficiency of the initiator can be improved, the loss of the initiator during the battery manufacturing process can be avoided, and the uneven formation of solid electrolyte can be prevented.

[0028] (3) The battery of the present invention performs electrocatalytic polymerization in the range of 10%-60% of the charge, and the open circuit voltage of the battery is between 3.15-3.35V. A constant current of 0.001-0.003C is applied to the battery. At this time, the current is extremely small, which can effectively ensure that the battery maintains a relatively stable voltage during the polymerization time, so that the polymerization reaction maintains a stable reaction rate, which is conducive to the formation of a solid electrolyte with a good structure.

[0029] (4) During the charging process, sodium ions are inserted into the negative electrode, which will cause the structure to expand. When 10%-60% of the charge is added, the negative electrode structure will expand to a certain extent, but the structural change is small. After the charging is stopped and the open circuit voltage is stabilized, the expansion volume of the negative electrode tends to stabilize. At this time, the solid electrolyte is polymerized, which is beneficial to increase the interfacial contact area between the solid electrolyte material and the electrode, and is beneficial to improve the interfacial performance.

[0030] (5) In hard carbon electrodes, irreversible sodium loss is mainly concentrated during the first charge and discharge process. After the first charge and discharge, the amount of irreversible sodium remaining in the hard carbon electrode tends to stabilize. Therefore, solid electrolyte polymerization is carried out after the first charge and discharge to avoid affecting the efficiency of the first charge and discharge and thus the amount of irreversible sodium in the battery after pre-polymerization.

[0031] (6) The ΔR value can determine the change in the interfacial performance between the solid electrolyte and the electrode during the conversion from the precursor solution to the solid electrolyte. It can make a preliminary judgment on the performance of the solid battery and effectively select the best solid battery. Attached Figure Description

[0032] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0033] Figure 1 This is the AC impedance test curve of the solid-state battery of the present invention. Detailed Implementation

[0034] Example 1

[0035] A method for fabricating a sodium-ion solid-state battery with improved electrochemical performance includes the following steps:

[0036] S1. Take 30 wt.% polymer monomer material, 70 wt.% solvent, 1 mol / L sodium salt, and 0.15 wt.% initiator, and stir magnetically until homogeneous to obtain a solid electrolyte precursor solution.

[0037] S2. Take the semi-finished battery and inject the solid electrolyte precursor solution into the battery using a vacuum injection method.

[0038] S3. The solid-state battery prepared in step S2 is left to stand at room temperature of 25°C for 24 hours to allow the precursor solution to fully impregnate it.

[0039] S4. After step S3, the solid battery that has been left to stand at room temperature for 24 hours is installed on the fixture and left to stand at 40°C for 24 hours to further wet the precursor solution. After cooling, the formation process is carried out and the battery is charged with 40% of its capacity.

[0040] S5. After the solid-state battery formed in step S4 is removed from the fixture, it is left to stand for 6-8 hours, then vacuumed and sealed before being subjected to a capacity testing process.

[0041] S6. After the solid-state battery in step S5 has been divided into different capacities, charge it to 60% capacity and let it stand for 6-12 hours until the battery reaches a steady state. Then measure the internal resistance R1 of the battery.

[0042] S7. Mix 0.15 wt.% initiator, 1 mol / L sodium salt and solvent with magnetic force to obtain an initiator solution. Inject the initiator solution into the solid battery obtained in step S6 and let it stand at room temperature for 12 hours.

[0043] S8. After installing the fixture, the solid battery obtained in step S7 is connected to the charge / discharge machine and a constant current of 0.001C is applied to electrocatalyze the solid battery. By controlling the constant voltage, the solid electrolyte precursor solution is polymerized to form a solid electrolyte.

[0044] S9. After the solid electrolyte is formed, let it stand at room temperature for 4-8 hours, then remove the fixture and perform a second sealing process. After extracting the gas generated by polymerization, the finished solid battery is obtained.

[0045] S10. Test the solid-state battery capacity. After completing the capacity test, charge it to 60% capacity and let it stand for 6-12 hours until the battery reaches a steady state. Then, measure the battery's internal resistance R2 and calculate ΔR.

[0046] Example 2

[0047] A method for fabricating a sodium-ion solid-state battery with improved electrochemical performance includes the following steps:

[0048] S1. Take 70 wt.% polymer monomer material, 30 wt.% solvent, 1.5 mol / L sodium salt, and 0.3 wt.% initiator, and stir magnetically until homogeneous to obtain a solid electrolyte precursor solution;

[0049] S2. Take the semi-finished battery and inject the solid electrolyte precursor solution into the battery using a vacuum injection method.

[0050] S3. The solid-state battery prepared in step S2 is left to stand at room temperature of 25°C for 48 hours to allow the precursor solution to fully impregnate it.

[0051] S4. After step S3, the solid battery that has been left to stand at room temperature for 48 hours is installed on the fixture and left to stand at 50°C for 12 hours to further wet the precursor solution. After cooling, the formation process is carried out and the battery is charged to 60% capacity.

[0052] S5. After the solid-state battery formed in step S4 is removed from the fixture, it is left to stand for 6-8 hours, then vacuumed and sealed before being subjected to a capacity testing process.

[0053] S6. After the solid-state battery in step S5 has been divided into different capacities, charge it to 10% capacity and let it stand for 6-12 hours until the battery reaches a steady state. Then measure the internal resistance R1 of the battery.

[0054] S7. Mix 0.3 wt.% initiator, 1.5 mol / L sodium salt and solvent with magnetic force to obtain an initiator solution. Inject the initiator solution into the solid battery obtained in step S6 and let it stand at room temperature for 12 hours.

[0055] S8. After installing the fixture, the solid battery obtained in step S7 is connected to the charge / discharge machine and a constant current of 0.003C is applied to electrocatalyze the solid battery. By controlling the constant voltage, the solid electrolyte precursor solution is polymerized to form a solid electrolyte.

[0056] S9. After the solid electrolyte is formed, let it stand at room temperature for 4-8 hours, then remove the fixture and perform a second sealing process. After extracting the gas generated by polymerization, the finished solid battery is obtained.

[0057] S10. Test the solid-state battery capacity. After completing the capacity test, charge it with 10% power and let it stand for 6-12 hours until the battery reaches a steady state. Then, measure the battery's internal resistance R2 and calculate ΔR.

[0058] Example 3: Solid-state battery electrochemical performance testing

[0059] 1. Rate performance test: The batteries of Examples 1 and 2 were tested at 0.1C and 1.0C rates at room temperature. The battery test range was 4.0V-1.5V.

[0060] 2. AC Impedance Testing: AC impedance tests were performed on the batteries of Examples 1 and 2 before and after the rate test to compare the battery changes. The positive electrode of the battery was the working electrode, and the negative electrode was the auxiliary electrode and reference electrode. The test range was 10. 5 -0.01Hz, amplitude of 5mV, test temperature of 25℃.

[0061] Test results:

[0062] The solid-state batteries fabricated using Examples 1 and 2 showed no significant increase in impedance before and after rate performance testing, indicating that the solid-state batteries fabricated using this method can still maintain good interface performance under high current testing conditions. Comparing the rate performance tests, the capacity retention rate of the battery in Example 1 at 1.0C / 0.1C was 95.58%, and that of the battery in Example 2 at 1.0C / 0.1C was 95.29%, demonstrating good high-rate performance. This indicates that solid-state batteries exhibit good performance at high current densities. This demonstrates that solid-state batteries fabricated using this method possess excellent electrochemical performance and good interfacial performance between the electrode and the solid electrolyte.

[0063] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a sodium-ion solid-state battery with improved electrochemical performance, the method comprising: The method comprises the following steps: ​ S1, taking a polymer monomer material, a solvent, a sodium salt, and an initiator, and stirring them uniformly by magnetic force to prepare a solid electrolyte precursor solution; S2, taking a semi-finished battery, and injecting the solid electrolyte precursor solution into the battery by vacuum injection; the semi-finished battery is prepared by Z-type stacking process of a positive electrode sheet, a negative electrode sheet, and a polyolefin separator, and is packaged after welding of the tab and an aluminum plastic film; S3, placing the solid-state battery prepared in the step S2 at room temperature to allow the precursor solution to be fully infiltrated; S4, installing a clamp on the solid-state battery after the step S3, and placing the battery at high temperature to allow the precursor solution to be further infiltrated, and then performing a formation process after cooling; the high-temperature standing parameters are 40-50 DEG C and 12-24 h; S5, taking off the clamp after the formation of the solid-state battery in the step S4, and placing the battery at room temperature for 6-8 h, and then performing a capacity matching process after vacuum pumping and packaging; S6, after the capacity matching of the solid-state battery in the step S5, charging a part of the capacity, and placing the battery for 6-12 h until the battery reaches a steady state, and then measuring an internal resistance R1 of the battery; S7, preparing an initiator solution by stirring an initiator, a sodium salt, and a solvent uniformly by magnetic force, and injecting the initiator solution into the solid-state battery obtained in the step S6, and placing the battery at room temperature for 12 h; S8, installing a clamp on the solid-state battery prepared in the step S7, connecting the battery to a charge-discharge machine, applying a constant current, and performing electrocatalytic polymerization on the solid-state battery to form a solid electrolyte; the constant current is 0.001-0.003 C; S9, after the formation of the solid electrolyte, placing the battery at room temperature for 4-8 h, taking off the clamp to perform a second packaging process, and then pumping out the gas generated in the polymerization to obtain a finished solid-state battery; S10, testing the capacity of the solid-state battery, charging the same amount of capacity as that after the capacity matching, placing the battery for 6-12 h until the battery reaches a steady state, and then measuring an internal resistance R2 of the battery to calculate a value of AR; the value of AR is used as a judgment condition of the solid-state battery, and the calculation method is AR=R2-R1.

2. The method of claim 1, wherein: The solid electrolyte precursor solution in the step S1 comprises a polymer monomer material, a solvent, a sodium salt, and an initiator, wherein the mass ratio of the polymer monomer material to the solvent is (30%-70%):(30%-70%), the concentration of the sodium salt is 1 mol / L-1.5 mol / L, and the content of the initiator is 0.3 wt.%-0.6 wt.% of the polymer monomer material.

3. The method of manufacturing a sodium-ion solid-state battery according to claim 1, wherein: The amount of the initiator in the step S7 is the same as the content of the initiator in the precursor solution in the step S1.

4. The method of claim 1, wherein: The room temperature standing parameters in the step S3 are 25 DEG C and 24-48 h.

5. The method of claim 1, wherein: The formation process in the step S4 adopts a clamp formation, a certain pressure is applied to the battery during the formation process, the interfaces are fully contacted, and an SEI film is effectively formed, the charging capacity during the formation process is controlled to be 40%-60% of the rated capacity, and a multi-stage charging current is used to charge in an incremental manner.

6. The method of manufacturing a sodium-ion solid-state battery of claim 1, wherein: The charging capacity after the capacity matching of the battery in the step S6 is 10%-60% of the rated capacity.

7. The method of manufacturing a sodium-ion solid-state battery of claim 1, wherein: The capacity detection in S10 is a charging test using multi-stage current. First, 0.005C is used to charge for 6h to activate the battery, then 0.01C is used for 2h, 0.05C is used for 2h, 0.1C is used to charge to full capacity of the battery, then 0.1C constant current is used for discharging to detect the capacity of the battery.

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