Formation and capacity grading process for power sodium ion battery

Abstract

The invention discloses a power sodium ion battery formation and capacity grading process, and belongs to the technical field of sodium ion batteries. A power sodium ion battery formation and capacity grading process comprises the following steps: S1, formation: performing three-stage charging on a sodium ion battery to be formed, and performing negative pressure pumping in each stage to obtain a formed sodium ion battery; and S2, capacity grading: placing the formed sodium ion battery at room temperature for 12 hours, firstly charging to 100% SOC, then discharging to 0% SOC, and finally charging to 59-61% SOC electric quantity, and performing negative pressure pumping at each stage to obtain the sodium ion battery. According to the invention, on the basis of not influencing the development and circulation of the capacity of the sodium ion battery, the overall time of the process is greatly shortened, the production efficiency is improved, and the manufacturing cost is reduced through the method of combining the formation step and the capacity grading step.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium ion batteries, and in particular relates to a formation and capacity separation process for a power sodium ion battery. Background Art

[0002] As lithium carbonate prices soar and the lithium battery industry chain is tense, sodium-ion batteries have lower costs, better safety performance, better low-temperature resistance, and longer cycle life. Therefore, current research tends to use sodium-ion batteries to replace lithium-ion batteries in the fields of power and energy storage secondary batteries. The formation and capacity separation processes of sodium-ion batteries play an important role in their manufacturing process. These two processes can not only improve the performance and quality of the battery, but also optimize the battery assembly and improve production efficiency. Therefore, in the manufacturing process of sodium-ion batteries, the quality and process of the formation and capacity separation processes must be strictly controlled.

[0003] Nowadays, in the production process of formation and capacity division of sodium ion batteries, in order to ensure the performance and film stability of sodium ion batteries, the battery formation adopts a method of first charging at a low rate and then charging in a step-by-step manner to a certain SOC, and the capacity division adopts a method of two charge and discharge cycles, which makes the entire formation and capacity division cycle longer. The longer production cycle also reduces production efficiency and increases manufacturing costs. Therefore, how to optimize the formation and capacity division process and improve the performance and production efficiency of sodium ion batteries is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The object of the present invention is to provide a power sodium ion battery formation and capacity separation process to solve the problems of long formation and capacity separation cycle and low production efficiency of sodium ion batteries in the background technology.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A power sodium ion battery formation and capacity separation process, comprising the following steps:

[0007] S1: formation: the sodium ion battery to be formed is charged in three stages, and negative pressure is drawn in each stage to obtain a formed sodium ion battery;

[0008] S2: Capacity division: After the formed sodium-ion battery is placed at room temperature for 12 hours, it is first charged to 100% SOC, then discharged to 0% SOC, and finally charged to 59%-61% SOC. Negative pressure is pumped at each stage to obtain a sodium-ion battery.

[0009] Further, in step S1, the specific steps of formation are: the sodium ion battery to be formed is allowed to stand for 5 to 10 minutes; 0.05C constant current charging to 9%-11% SOC power, the cut-off voltage is 3.0V, and then standing for 5 to 10 minutes; 0.1C constant current charging to 29%-31% SOC power, the cut-off voltage is 3.5V, and then standing for 5 to 10 minutes; 0.2C constant current charging to 64%-66% SOC power, the cut-off voltage is 3.95V, and the formed sodium ion battery is obtained.

[0010] The above steps are divided into three steps, namely, low current, medium current and high current. In the low current stage, by applying a gentle and stable current, it helps to gradually form a dense, structurally stable and low interfacial impedance solid electrolyte interface (SEI) film inside the battery. This layer of film is crucial to the performance of the battery. It can effectively isolate the direct contact between the electrolyte and the electrode material, reduce unnecessary side reactions, and thus extend the service life of the battery. In the following medium current stage, the current intensity is moderately increased to further consolidate and strengthen the formation of the SEI film. After entering the high current stage, the current intensity increases significantly. This strategy aims to quickly and effectively eliminate possible side reactions between the electrolyte and the negative electrode hard carbon. Through the flushing effect of the large current, the density of the SEI film can be improved again, making it tougher and more durable. At the same time, this stage also effectively inhibits the precipitation of sodium ions, avoiding the degradation of battery performance and safety hazards caused by sodium ion deposition.

[0011] Furthermore, in step S1, the temperature during the entire formation process is 32-38°C.

[0012] Furthermore, in step S1, the negative pressure value of each formation stage is -60 kPa to -70 kPa.

[0013] Furthermore, the specific steps of step S2 are: 0.33C constant current charging to 100% SOC, cut-off voltage 4.25V, then standing for 5 to 10 minutes; 0.5C constant current discharge to 0% SOC, cut-off voltage 2.0V, then standing for 5 to 10 minutes; 0.33C constant current charging again to 59%-61% SOC, cut-off voltage 3.85V, standing for 5 to 10 minutes, to obtain a sodium ion battery.

[0014] Furthermore, in step S2, the negative pressure value of each stage of volume separation is -60 kPa to -70 kPa, and the temperature is 32 to 38°C.

[0015] Furthermore, the preparation method of the sodium ion battery to be formed is:

[0016] A1: Stack the positive electrode sheet, negative electrode sheet and separator in order to obtain a bare cell;

[0017] A2: Place the bare battery cell in an aluminum shell for sealing welding, and then dry it in an oven;

[0018] A3: After the moisture content of the electrode meets the requirements, liquid injection is carried out, and after liquid injection, the electrode is placed at high temperature to obtain the sodium ion battery to be formed.

[0019] Furthermore, in step A1, the material of the positive electrode sheet is sodium nickel manganese oxide, the material of the negative electrode sheet is hard carbon, the electrolyte is a carbonate electrolyte, and the diaphragm is a double-layer glue-coated ceramic diaphragm.

[0020] Furthermore, in step A2, the drying temperature is 85-95° C., and the drying time is 10-14 hours.

[0021] Furthermore, in step A3, the conditions for the moisture value of the electrode are: the moisture value of the positive electrode is ≤200ppm, and the moisture value of the negative electrode is ≤500ppm; the high temperature standing temperature is 35-45°C.

[0022] Beneficial effects of the present invention:

[0023] 1. The present invention adopts three-stage step-type constant current charging of small current, medium current and large current. The small current and medium current stages ensure that a dense, structurally stable, and low-interface impedance SEI film is formed inside the battery. The large current stage can eliminate the side reaction between the electrolyte and the negative electrode hard carbon, further improve the density of the SEI film, and inhibit the precipitation of sodium ions. Through negative pressure and high temperature volume separation, the gas generated inside the battery is further removed in time, so that the electrolyte can better penetrate into the electrode surface, which has a significant effect on forming a denser and more stable SEI film.

[0024] 2. The present invention significantly reduces the overall process time, improves production efficiency and reduces manufacturing costs by combining the formation and capacity separation steps without affecting the capacity and cycle of the sodium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] Figure 1 This is a process flow chart of formation and capacity separation of sodium ion batteries of the present invention;

[0027] Figure 2 It is a graph of the cycle capacity retention rate of sodium ion batteries of Examples 1-3 of the present invention and Comparative Examples 1-3. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] A power sodium ion battery formation and capacity separation process, comprising the following steps:

[0031] S1: Place the sodium-ion battery to be formed into the fixture in the formation cabinet and fix it, remove the process rubber plug, and lower the negative pressure row to align the negative pressure nozzle with the injection port.

[0032] S2: Set the chemical composition step: ① stand for 5 minutes; ② 0.05C constant current charging to 10% SOC power, cut-off voltage 3V, stand for 5 minutes; ③ 0.1C constant current charging to 30% SOC power, cut-off voltage 3.5V, stand for 5 minutes; ④ 0.2C constant current charging to 65% SOC power, cut-off voltage 3.95V, get the formed sodium ion battery; ⑤ put the formed sodium ion battery at room temperature for 12 hours; ⑥ 0.33C constant current charging to 100% SOC power, cut-off voltage 4.25V, stand for 5 minutes; ⑦ 0.5C constant current discharge to 0% SOC power, cut-off voltage 2.0V, stand for 5 minutes; ⑧ 0.33C constant current charging to 60% SOC power, cut-off voltage 3.85V, stand for 10 minutes. The negative pressure value of each stage of chemical composition is -60kPa, and the temperature is kept at 35℃ throughout the process.

[0033] The preparation method of the sodium ion battery to be formed is:

[0034] A1: Stack the positive electrode sheet, the negative electrode sheet and the separator in order to obtain a bare battery cell; wherein the material of the positive electrode sheet is sodium nickel manganese oxide, the material of the negative electrode sheet is hard carbon, the electrolyte is a carbonate electrolyte, and the separator is a double-layer glue-coated ceramic separator;

[0035] A2: Place the bare cell in an aluminum shell for sealing welding, and then dry it in an oven at 90°C for 12 hours;

[0036] A3: After the moisture value of the electrode meets the conditions (the moisture value of the positive electrode is ≤200ppm, the moisture value of the negative electrode is ≤500ppm), the liquid is injected. After the injection, it is allowed to stand at 40°C to obtain the sodium ion battery to be formed.

[0037] Example 2

[0038] A power sodium ion battery formation and capacity separation process, comprising the following steps:

[0039] S1: Place the sodium-ion battery to be formed into the fixture in the formation cabinet and fix it, remove the process rubber plug, and lower the negative pressure row to align the negative pressure nozzle with the injection port.

[0040] S2: Set the chemical composition step: ① stand for 5 minutes; ② 0.05C constant current charging to 10% SOC power, cut-off voltage 3V, stand for 5 minutes; ③ 0.1C constant current charging to 30% SOC power, cut-off voltage 3.5V, stand for 5 minutes; ④ 0.2C constant current charging to 65% SOC power, cut-off voltage 3.95V, get the formed sodium ion battery; ⑥ 0.33C constant current charging to 100% SOC power, cut-off voltage 4.25V, stand for 5 minutes; ⑦ 0.5C constant current discharge to 0% SOC power, cut-off voltage 2.0V, stand for 5 minutes; ⑧ 0.33C constant current charging to 60% SOC power, cut-off voltage 3.85V, stand for 10 minutes. The negative pressure value of each stage of chemical composition is -65kPa, and the temperature is kept at 35℃ throughout the process.

[0041] The preparation method of the sodium ion battery to be formed is:

[0042] A1: Stack the positive electrode sheet, the negative electrode sheet and the separator in order to obtain a bare battery cell; wherein the material of the positive electrode sheet is sodium nickel manganese oxide, the material of the negative electrode sheet is hard carbon, the electrolyte is a carbonate electrolyte, and the separator is a double-layer glue-coated ceramic separator;

[0043] A2: Place the bare cell in an aluminum shell for sealing welding, and then dry it in an oven at 90°C for 12 hours;

[0044] A3: After the moisture value of the electrode meets the conditions (the moisture value of the positive electrode is ≤200ppm, the moisture value of the negative electrode is ≤500ppm), the liquid is injected. After the injection, it is allowed to stand at 40°C to obtain the sodium ion battery to be formed.

[0045] Example 3

[0046] A power sodium ion battery formation and capacity separation process, comprising the following steps:

[0047] S1: Place the sodium-ion battery to be formed into the fixture in the formation cabinet and fix it, remove the process rubber plug, and lower the negative pressure row to align the negative pressure nozzle with the injection port.

[0048] S2: Set the chemical composition step: ① stand for 5 minutes; ② 0.05C constant current charging to 10% SOC power, cut-off voltage 3V, stand for 5 minutes; ③ 0.1C constant current charging to 30% SOC power, cut-off voltage 3.5V, stand for 5 minutes; ④ 0.2C constant current charging to 65% SOC power, cut-off voltage 3.95V, get the formed sodium ion battery; ⑥ 0.33C constant current charging to 100% SOC power, cut-off voltage 4.25V, stand for 5 minutes; ⑦ 0.5C constant current discharge to 0% SOC power, cut-off voltage 2.0V, stand for 5 minutes; ⑧ 0.33C constant current charging to 60% SOC power, cut-off voltage 3.85V, stand for 10 minutes. The negative pressure value of each stage of chemical composition is -70kPa, and the temperature is kept at 35℃ throughout the process.

[0049] The preparation method of the sodium ion battery to be formed is:

[0050] A1: Stack the positive electrode sheet, the negative electrode sheet and the separator in order to obtain a bare battery cell; wherein the material of the positive electrode sheet is sodium nickel manganese oxide, the material of the negative electrode sheet is hard carbon, the electrolyte is a carbonate electrolyte, and the separator is a double-layer glue-coated ceramic separator;

[0051] A2: Place the bare cell in an aluminum shell for sealing welding, and then dry it in an oven at 90°C for 12 hours;

[0052] A3: After the moisture value of the electrode meets the conditions (the moisture value of the positive electrode is ≤200ppm, the moisture value of the negative electrode is ≤500ppm), the liquid is injected. After the injection, it is allowed to stand at 40°C to obtain the sodium ion battery to be formed.

[0053] Comparative Example 1

[0054] A power sodium ion battery formation and capacity separation process, comprising the following steps:

[0055] S1: Place the sodium-ion battery to be formed into the fixture in the formation cabinet and fix it, remove the process rubber plug, and lower the negative pressure row to align the negative pressure nozzle with the injection port.

[0056] S2. Set the formation process: ① stand for 5 minutes; ② 0.05C constant current charging to 10% SOC power, cut-off voltage 3V, stand for 5 minutes; ③ 0.1C constant current charging to 30% SOC power, cut-off voltage 3.5V, stand for 5 minutes; ④ 0.2C constant current charging to 65% SOC power, cut-off voltage 3.95V, to obtain the formed sodium ion battery; set the negative pressure to -60kPa and the temperature to 35°C throughout the process.

[0057] S3. Place the formed battery in an aging room for 1 day.

[0058] S4. Set up the capacity division process: ① Leave the rested battery for 5 minutes; ② Charge to 100% SOC at 0.33C constant current, cut-off voltage 4.25V, leave for 5 minutes; ③ Discharge to 0% SOC at 0.5C constant current, cut-off voltage 2.0V, leave for 5 minutes; ④ Cycle the capacity division process ② to ③ once; ⑤ Charge to 60% SOC at 0.33C constant current, cut-off voltage 3.85V, leave for 10 minutes. Set the negative pressure to -60kPa and the temperature to 35℃ throughout the process.

[0059] The preparation method of the sodium ion battery to be formed is the same as that in Example 1.

[0060] Comparative Example 2

[0061] A power sodium ion battery formation and capacity separation process, comprising the following steps:

[0062] S1: Place the sodium-ion battery to be formed into the fixture in the formation cabinet and fix it, remove the process rubber plug, and lower the negative pressure row to align the negative pressure nozzle with the injection port.

[0063] S2. Set the formation process steps: ① stand for 5 minutes; ② 0.05C constant current charging to 10% SOC power, cut-off voltage 3V, stand for 5 minutes; ③ 0.1C constant current charging to 30% SOC power, cut-off voltage 3.5V, stand for 5 minutes; ④ 0.2C constant current charging to 65% SOC power, cut-off voltage 3.95V, to obtain the formed sodium ion battery; set the negative pressure to -65kPa and the temperature to 35°C throughout the process.

[0064] S3. Place the formed battery in an aging room for 1 day.

[0065] S4. Set up the capacity division process: ① Leave the rested battery for 5 minutes; ② Charge to 100% SOC at 0.33C constant current, cut-off voltage 4.25V, leave for 5 minutes; ③ Discharge to 0% SOC at 0.5C constant current, cut-off voltage 2.0V, leave for 5 minutes; ④ Cycle the capacity division process ② to ③ once; ⑤ Charge to 60% SOC at 0.33C constant current, cut-off voltage 3.85V, leave for 10 minutes. Set the negative pressure to -65kPa and the temperature to 35℃ throughout the process.

[0066] The preparation method of the sodium ion battery to be formed is the same as that in Example 1.

[0067] Comparative Example 3

[0068] A power sodium ion battery formation and capacity separation process, comprising the following steps:

[0069] S1: Place the sodium-ion battery to be formed into the fixture in the formation cabinet and fix it, remove the process rubber plug, and lower the negative pressure row to align the negative pressure nozzle with the injection port.

[0070] S2. Set the formation process: ① stand for 5 minutes; ② 0.05C constant current charging to 10% SOC power, cut-off voltage 3V, stand for 5 minutes; ③ 0.1C constant current charging to 30% SOC power, cut-off voltage 3.5V, stand for 5 minutes; ④ 0.2C constant current charging to 65% SOC power, cut-off voltage 3.95V, to obtain the formed sodium ion battery; set the negative pressure to -70kPa and the temperature to 35°C throughout the process.

[0071] S3. Place the formed battery in an aging room for 1 day.

[0072] S4. Set up the capacity division process: ① Leave the rested battery for 5 minutes; ② Charge to 100% SOC at 0.33C constant current, cut-off voltage 4.25V, leave for 5 minutes; ③ Discharge to 0% SOC at 0.5C constant current, cut-off voltage 2.0V, leave for 5 minutes; ④ Cycle the capacity division process ② to ③ once; ⑤ Charge to 60% SOC at 0.33C constant current, cut-off voltage 3.85V, leave for 10 minutes. Set the negative pressure to -70kPa and the temperature to 35℃ throughout the process.

[0073] The preparation method of the sodium ion battery to be formed is the same as that in Example 1.

[0074] The sodium ion batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were placed in a thermostat for long cycle testing, and the cycle test steps were set as follows: ① 5 minutes of standby; ② 1C constant current charging to a cut-off voltage of 4.1V, and 5 minutes of standby; ③ 0.33C constant current charging to a cut-off voltage of 4.25V, and 5 minutes of standby; ④ 1C constant current discharge to 2.5V, and 5 minutes of standby; ⑤ 0.33C constant current discharge to a cut-off voltage of 2.0V, and 10 minutes of standby; 500 cycles from steps ② to ⑤. The capacity can be obtained by testing the capacity cabinet, and the capacity retention rate in the nth week = (capacity in the nth cycle / capacity in the first cycle) * 100%. The test results are shown in Tables 1 and Figure 2 As shown:

[0075] Table 1

[0076]

[0077] From Table 1 and Figure 2 It can be seen that the fractional capacity and capacity retention rate of the sodium ion batteries prepared in Examples 1 to 3 are similar to those of the sodium ion batteries prepared in Comparative Examples 1 to 3.

[0078] Comparative Examples 1 to 3 are different from Examples 1 to 3 in that the batteries after formation are placed in an aging room for one day. The time is longer than that of Examples 1 to 3, but the fractional capacity and capacity retention rate are similar. It can be seen that the present invention greatly reduces the overall process time, improves production efficiency and reduces manufacturing costs by combining the formation and fractional capacity steps without affecting the capacity and circulation of the sodium ion battery.

[0079] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0080] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sodium ion battery formation and capacity separation process, characterized in that: The steps include: S1: formation: the sodium ion battery to be formed is charged in three stages, and negative pressure is drawn in each stage to obtain a formed sodium ion battery; S2: Capacity division: After the formed sodium-ion battery is placed at room temperature for 12 hours, it is first charged to 100% SOC, then discharged to 0% SOC, and finally charged to 59%-61% SOC. Negative pressure is pumped at each stage to obtain a sodium-ion battery.

2. A power sodium ion battery formation and capacity separation process according to claim 1, characterized in that: In step S1, the specific steps of formation are: allowing the sodium ion battery to be formed to stand for 5 to 10 minutes; charging at a constant current of 0.05C to 9%-11% SOC power, with a cut-off voltage of 3.0V, and then standing for 5 to 10 minutes; charging at a constant current of 0.1C to 29%-31% SOC power, with a cut-off voltage of 3.5V, and then standing for 5 to 10 minutes; charging at a constant current of 0.2C to 64%-66% SOC power, with a cut-off voltage of 3.95V, to obtain a formed sodium ion battery.

3. A power sodium ion battery formation and capacity separation process according to claim 1, characterized in that: In step S1, the temperature during the entire formation process is 32-38°C.

4. A power sodium ion battery formation and capacity separation process according to claim 1, characterized in that: In step S1, the negative pressure value of each formation stage is -60 kPa to -70 kPa.

5. A power sodium ion battery formation and capacity separation process according to claim 1, characterized in that: The specific steps of step S2 are: 0.33C constant current charging to 100% SOC, cut-off voltage 4.25V, then standing for 5 to 10 minutes; 0.5C constant current discharge to 0% SOC, cut-off voltage 2.0V, then standing for 5 to 10 minutes; 0.33C constant current charging again to 59%-61% SOC, cut-off voltage 3.85V, standing for 5 to 10 minutes, to obtain a sodium ion battery.

6. A power sodium ion battery formation and capacity separation process according to claim 1, characterized in that: In step S2, the negative pressure value of each stage of volume separation is -60kPa to -70kPa, and the temperature is 32 to 38°C.

7. A power sodium ion battery formation and capacity separation process according to claim 1, characterized in that: The preparation method of the sodium ion battery to be formed is: A1: Stack the positive electrode sheet, negative electrode sheet and separator in order to obtain a bare cell; A2: Place the bare battery cell in an aluminum shell for sealing welding, and then dry it in an oven; A3: After the moisture content of the electrode meets the requirements, liquid injection is carried out, and after liquid injection, the electrode is placed at high temperature to obtain the sodium ion battery to be formed.

8. A power sodium ion battery formation and capacity separation process according to claim 7, characterized in that: In step A1, the material of the positive electrode sheet is sodium nickel manganese oxide, the material of the negative electrode sheet is hard carbon, the electrolyte is a carbonate electrolyte, and the diaphragm is a double-layer glue-coated ceramic diaphragm.

9. A power sodium ion battery formation and capacity separation process according to claim 7, characterized in that: In step A1, the drying temperature is 85-95° C., and the drying time is 10-14 hours.

10. A power sodium ion battery formation and capacity separation process according to claim 7, characterized in that: In step A3, the conditions for the moisture value of the electrode are: the moisture value of the positive electrode is ≤200ppm, and the moisture value of the negative electrode is ≤500ppm; the high temperature static temperature is 35-45°C.

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