Sodium ion battery formation method

Abstract

The invention relates to the technical field of sodium-ion battery formation processes, and particularly discloses a sodium-ion battery formation method which comprises the following steps: performing vacuum baking on a positive plate and a negative plate at a first temperature, and then assembling into a battery cell; performing vacuum baking on the battery cell at a second temperature, injecting liquid, and ensuring that the second temperature is greater than the first temperature and the moisture of the battery cell before liquid injection is less than or equal to 200ppm; standing the battery cell at a third temperature after liquid injection, and ensuring that the third temperature is lower than the first temperature; and forming the well-stood battery cell at a fourth temperature, and ensuring that the fourth temperature is lower than the third temperature, and the formation mode is that charging and discharging current multiplying power and cut-off conditions are allocated for multiple times for the battery cell. According to the invention, the formed SEI film is more stable and lower in internal resistance by adjusting the charge and discharge current multiplying power and cut-off conditions, the multiplying power performance and the cycling stability of the battery cell are improved, the formation time can be greatly shortened, and the energy consumption can be reduced; in addition, the formation mode is suitable for any system of the sodium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion battery formation process, in particular to a sodium ion battery formation method. BACKGROUND

[0002] With the continuous growth of global energy demand and the increasing awareness of environmental protection, developing efficient and sustainable energy storage technology has become one of the current hotspots of scientific research. Sodium ion batteries (SIBs) are considered as a strong candidate for the next generation of energy storage technology due to their abundant sodium resources and low cost, and have gradually attracted attention and been applied in electric vehicles and power grid systems.

[0003] Similar to lithium ion batteries, when the battery is charged and discharged, many reactions occur between the electrode material and the electrolyte at the solid-liquid interface, and a protective layer is formed on the surface of the electrode material, which is called the solid electrolyte interface (SEI) film. The SEI film plays a crucial role in the performance of hard carbon as a negative electrode material for sodium ion batteries, and its formation mechanism, characteristics and stability directly affect the performance and life of the battery. Therefore, developing a suitable formation system for formation is a crucial step in the battery manufacturing process.

[0004] NaF is one of the important components of the SEI film of sodium ion batteries, and has an important influence on the performance of the SEI film. Some documents have confirmed that formation at a higher rate can result in fewer NaF products, a thinner SEI film, a smaller RCT, and better cycle performance. In addition, the activation energy barrier for Na+ migration in NaF is high, so the SEI film should form a thin NaF component.

[0005] Compared with the SEI film formed by lithium batteries, the sodium ion battery has the following characteristics:

[0006] Table 1 Sodium battery SEI vs. lithium battery SEI

[0007]

[0008]

[0009] Based on this technical background, the present application studies a sodium ion battery formation method. SUMMARY

[0010] In view of the shortcomings of the prior art, the present application provides a sodium ion battery formation method, which adjusts the charge and discharge current rate and the cutoff condition to make the formed SEI film more stable and have lower internal resistance, improve the rate performance and cycle stability of the battery, and at the same time greatly shorten the formation time and reduce the energy consumption. In addition, the charge and discharge cutoff condition of this formation system is based on the state of charge, and this method is suitable for any sodium ion battery system, such as the layer oxygen system and the polyanion system.

[0011] To achieve the above object, the first aspect of the present application provides a sodium-ion battery formation method, comprising:

[0012] The positive electrode sheet and the negative electrode sheet are assembled into a battery cell after vacuum baking at a first temperature;

[0013] The battery cell is injected with liquid after vacuum baking at a second temperature, and the second temperature is greater than the first temperature, and the moisture of the battery cell before injection is ≤200ppm;

[0014] The battery cell is placed at a third temperature after injection, and the third temperature is less than the first temperature;

[0015] The battery cell is formed at a fourth temperature, and the fourth temperature is less than the third temperature, and the formation method is to adjust the charge and discharge current ratio and the cutoff condition of the battery cell multiple times, so that the solid-state electrolyte interface film is more stable and the internal resistance is lower.

[0016] The beneficial effects of the present application include:

[0017] (1) The sodium-ion battery formation method proposed by the present application adjusts the charge and discharge current ratio and the cutoff condition, so that the SEI film formed is more stable and the internal resistance is lower, which improves the rate performance and cycle stability of the battery cell, and at the same time, the formation time is greatly shortened and the energy consumption is reduced; In addition, the charge and discharge cutoff condition of this formation method is based on the state of charge, and this method is suitable for any sodium-ion battery system, such as layered oxide system and polyanion system.

[0018] (2) The sodium-ion battery formation method proposed by the present application first charges directly to the pre-film potential by a large current, which greatly shortens the formation time compared to starting with a small current; and the cutoff condition of each segment of the formation charge is based on the charge capacity, and this method is suitable for any sodium-ion battery system (such as layered oxide cutoff upper limit voltage ≥3.9V, polyanion system cutoff voltage only to ~3.4V).

[0019] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0020] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0021] Figure 1 The flowchart of the sodium-ion battery formation method proposed by the present application.

[0022] Figure 2Another specific embodiment of the sodium-ion battery formation method proposed in the present application is shown in the schematic diagram of the formation mode. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0024] The present application provides a sodium-ion battery formation method, as shown in Figure 1 comprising:

[0025] vacuum baking the positive electrode sheet and the negative electrode sheet at a first temperature, and then assembling the battery cell;

[0026] vacuum baking the battery cell at a second temperature, and then injecting liquid, and ensuring that the second temperature is greater than the first temperature, and the moisture of the battery cell before injection is ≤200ppm;

[0027] placing the battery cell after injection at a third temperature, and ensuring that the third temperature is less than the first temperature;

[0028] forming the battery cell at a fourth temperature, and ensuring that the fourth temperature is less than the third temperature, and the formation mode is to adjust the charge and discharge current ratio and the cutoff condition of the battery cell multiple times, so that the solid electrolyte interface film is more stable and the internal resistance is lower.

[0029] In the present application, by adjusting the charge and discharge current ratio and the cutoff condition, the SEI film formed is more stable and the internal resistance is lower, which improves the rate performance and cycle stability of the battery cell, and at the same time, the formation time is greatly shortened and the energy consumption is reduced; in addition, the charge and discharge cutoff condition of this formation mode is based on the state of charge, and this mode is applicable to any system of sodium-ion battery, such as layered oxygen system, polyanion system, etc.

[0030] According to the present application, the active material of the positive electrode sheet is layered oxide and / or polyanion;

[0031] The active material of the negative electrode sheet is hard carbon, or a mixture of P-based negative electrode and hard carbon;

[0032] The first temperature is 80-110℃, and the vacuum baking time at the first temperature is 8-12h.

[0033] According to the present application, the second temperature is 90-110℃, and the vacuum baking time at the second temperature is 12-24h.

[0034] According to the present application, the third temperature is 45-55℃, and the placing time at the third temperature is 12-48h.

[0035] According to the application, the fourth temperature is 22-28℃, and the pressure of the formation is 450-550kgf.

[0036] According to the application, the multiple adjustment of the charge-discharge current ratio and the cutoff condition of the battery cell are included:

[0037] After the battery cell is charged to the pre-film forming potential according to the first charging condition, the battery cell is rested for a first preset time, and the pre-film forming potential is the first formation condition;

[0038] After the battery cell is charged to the second formation condition according to the second charging condition, the battery cell is rested for a second preset time;

[0039] After the battery cell is charged to the third formation condition according to the third charging condition, the battery cell is rested for a third preset time;

[0040] After the battery cell is charged to the fourth formation condition according to the fourth charging condition, the battery cell is rested for a fourth preset time;

[0041] After the battery cell is discharged to the cutoff condition according to the discharge condition, the battery cell is rested for a fifth preset time.

[0042] According to the application, the first charging condition is to charge at a current of 0.33C-0.7C;

[0043] The first formation condition is 23%-28% SOC of the battery cell;

[0044] The first preset time is 3-5min.

[0045] According to the application, the second charging condition is to charge at a current of 0.03C-0.07C;

[0046] The second formation condition is 3.5%-12.0% SOC of the battery cell;

[0047] The second preset time is 3-5min.

[0048] According to the application, the third charging condition is to charge at a current of 0.08C-0.12C;

[0049] The third formation condition is 7.5%-24.0% SOC of the battery cell;

[0050] The third preset time is 3-5min;

[0051] The fourth charging condition is to charge at a current of 0.15C-0.5C;

[0052] The fourth formation condition is the cutoff SOC of the battery cell, the constant voltage cutoff current is 0.05C, and the entire charging capacity is ≥90% SOC;

[0053] The fourth preset time is 3-5 min.

[0054] According to the application, the discharging condition is constant current discharging at 0.3C-0.5C;

[0055] The cut-off condition is 40-60% SOC capacity of the battery cell;

[0056] The fifth preset time is 3-5 min.

[0057] In the application, the direct charging at a large current to the pre-film forming potential is used, which greatly shortens the formation time compared with the use of a small current at the beginning; and the cut-off condition of each formation charging section is the charging capacity, which is suitable for any sodium ion battery system (such as the upper limit voltage of the layered oxide is greater than or equal to 3.9V, and the cut-off voltage of the polyanion system is only about 3.4V).

[0058] The application will be described in more detail through examples.

[0059] Example 1

[0060] This embodiment proposes a sodium ion battery formation method, as shown in Figure 1 , which comprises:

[0061] The positive plate is baked at 100℃ for 12h, and the negative plate is baked at 80℃ for 12h before assembly; the assembled battery cell is baked at 105℃ for 12-24h, and the water content in the battery after baking is 113.2ppm; the electrolyte is injected and packaged, and the package is placed at 45℃ for 24h; after the standing is completed, the battery cell is placed on the formation cabinet, the formation temperature is set to 25±3℃, and the formation pressure is set to 500±50kgf, as shown in Figure 2 , the specific formation mode comprises:

[0062] A, constant current charging at 0.5C for 28min, the charging capacity is 23.4% SOC, and the standing time is 3min;

[0063] B, constant current charging at 0.05C for 3h, the charging capacity is 11.6% SOC, and the standing time is 3min;

[0064] C, constant current charging at 0.1C for 3h, the charging capacity is 23.3% SOC, and the standing time is 3min;

[0065] D, constant current and constant voltage charging to the full capacity cut-off voltage at 0.2C, to 100% SOC, the constant voltage cut-off current is 0.05C, and the standing time is 3-5min;

[0066] E, constant current discharging at 0.33C to 50% SOC capacity, standing for 3-5min, and the formation is completed.

[0067] Example 2

[0068] The embodiment provides a sodium ion battery formation method, as shown in the following table, which comprises the following steps. Figure 1

[0069] The positive electrode sheet is baked at 100 DEG C for 12 hours, and the negative electrode sheet is baked at 80 DEG C for 12 hours, and then the assembled battery is baked at 105 DEG C for 12-24 hours, and the water content of the electrode sheet in the battery after baking is 120.9 ppm; the electrolyte is injected and packaged, and the packaged battery is placed at 45 DEG C for 24 hours; after the placement, the battery is placed on a formation cabinet, the formation temperature is set to 25 DEG C + / - 3 DEG C, and the formation pressure is set to 500 + / - 50 kgf, as shown in the following table, and the specific formation mode comprises the following steps. Figure 2

[0070] A, 0.5C constant current charging for 28 min, the charging capacity is 23.4% SOC, and the standing time is 3 min;

[0071] B, 0.05C constant current charging for 2 hours, the charging capacity is 7.7% SOC, and the standing time is 3 min;

[0072] C, 0.1C constant current charging for 2 hours, the charging capacity is 15.6% SOC, and the standing time is 3 min;

[0073] D, 0.2C constant current and constant voltage charging to the full voltage, the charging capacity is 100% SOC, the constant voltage cutoff current is 0.05C, and the standing time is 3-5 min;

[0074] E, 0.33C constant current discharging for 50% SOC capacity, and the standing time is 3-5 min.

[0075] Embodiment 3

[0076] The embodiment provides a sodium ion battery formation method, as shown in the following table, which comprises the following steps. Figure 1

[0077] The positive electrode sheet is baked at 100 DEG C for 12 hours, and the negative electrode sheet is baked at 80 DEG C for 12 hours, and then the assembled battery is baked at 105 DEG C for 12-24 hours, and the water content of the electrode sheet in the battery after baking is 120.9 ppm; the electrolyte is injected and packaged, and the packaged battery is placed at 45 DEG C for 24 hours; after the placement, the battery is placed on a formation cabinet, the formation temperature is set to 25 DEG C + / - 3 DEG C, and the formation pressure is set to 500 + / - 50 kgf, as shown in the following table, and the specific formation mode comprises the following steps. Figure 2

[0078] A, 0.5C constant current charging for 28 min, the charging capacity is 23.4% SOC, and the standing time is 3 min;

[0079] B, 0.05C constant current charging for 2 hours, the charging capacity is 7.7% SOC, and the standing time is 3 min;​​​​

[0080] C, 0.1C constant current charging for 1h, the charge capacity is 8.5% SOC, and standing for 3min;

[0081] D, 0.2C constant current and constant voltage charging to the full voltage cut-off, to 100% SOC, the constant voltage cut-off current is 0.05C, and standing for 3-5min;

[0082] E, 0.33C constant current discharging 50% SOC capacity, standing for 3-5min, and the formation ends.

[0083] Example 4

[0084] This embodiment proposes a sodium ion battery formation method, as shown in Figure 1 , which comprises:

[0085] The positive plate is baked at 100℃ for 12h, and the negative plate is baked at 80℃ for 12h before assembly; the assembled cell is baked at 105℃ for 12-24h, and the water content of the plate in the battery after baking is 105.6ppm; the electrolyte is injected and packaged, and standing for 24h at 45℃; after standing, the cell is placed on the formation cabinet, and the formation temperature is set to 25±3℃, and the formation pressure is 500±50kgf, as shown in Figure 2 , the specific formation mode comprises:

[0086] A, 0.5C constant current charging for 28min, the charge capacity is 23.4% SOC, and standing for 3min;

[0087] B, 0.05C constant current charging for 2h, the charge capacity is 7.6% SOC, and standing for 3min;

[0088] C, 0.1C constant current charging for 2h, the charge capacity is 15.7% SOC, and standing for 3min;

[0089] D, 0.2C constant current and constant voltage charging to the specified capacity, the constant voltage cut-off current is 0.05C, and the total capacity is 90% SOC, and standing for 3-5min;

[0090] E, 0.33C constant current discharging 50% SOC capacity, standing for 3-5min, and the formation ends.

[0091] Example 5

[0092] This embodiment proposes a sodium ion battery formation method, as shown in Figure 1 , which comprises:

[0093] The positive electrode sheet is baked at 100°C for 12h, and the negative electrode sheet is baked at 80°C for 12h before assembly; the assembled battery is baked at 105°C for 12-24h, and the moisture content of the electrode sheet in the battery after baking is 108.2ppm; the electrolyte is injected and packaged, and the battery is placed at 45°C for 24h; after standing, the battery is placed on the formation cabinet, the formation temperature is set to 25±3°C, and the formation pressure is set to 500±50kgf, as shown in Figure 2 The specific formation method includes:

[0094] A, 0.5C constant current charging for 28min, the charging capacity is 23.4% SOC, and the standing time is 3min;

[0095] B, 0.05C constant current charging for 2h, the charging capacity is 7.5% SOC, and the standing time is 3min;

[0096] C, 0.1C constant current charging for 2h, the charging capacity is 15.6% SOC, and the standing time is 3min;

[0097] D, 0.33C constant current and constant voltage charging to 100% SOC, the constant voltage cutoff current is 0.05C, and the standing time is 3-5min;

[0098] E, 0.33C constant current discharging to 50% SOC, and the standing time is 3-5min, and the formation is completed.

[0099] Example 6

[0100] This embodiment proposes a sodium ion battery formation method, as shown in Figure 1 The specific formation method includes:

[0101] The positive electrode sheet is baked at 100°C for 12h, and the negative electrode sheet is baked at 80°C for 12h before assembly; the assembled battery is baked at 105°C for 12-24h, and the moisture content of the electrode sheet in the battery after baking is 98.2ppm; the electrolyte is injected and packaged, and the battery is placed at 45°C for 24h; after standing, the battery is placed on the formation cabinet, the formation temperature is set to 25±3°C, and the formation pressure is set to 500±50kgf, as shown in Figure 2 The specific formation method includes:

[0102] A, 0.5C constant current charging for 28min, the charging capacity is 23.4% SOC, and the standing time is 3min;

[0103] B, 0.05C constant current charging for 2h, the charging capacity is 7.7% SOC, and the standing time is 3min;

[0104] C, 0.1C constant current charging for 2h, the charging capacity is 15.6% SOC, and the standing time is 3min;

[0105] D. 0.5C constant current and constant voltage charging to 90% SOC, constant voltage cutoff current is 0.05C, and standing for 3-5 min;

[0106] E. 0.33C constant current discharging to 50% SOC, standing for 3-5 min, and formation ending.

[0107] Example 7

[0108] This example proposes a sodium ion battery formation method, as shown in the following figure, which includes: Figure 1

[0109] The positive electrode sheet is baked at 100°C for 12h, and the negative electrode sheet is baked at 80°C for 12h before assembly; the assembled battery is baked at 105°C for 12-24h, and the water content in the electrode sheet in the battery after baking is 103.7ppm; the electrolyte is injected and packaged, and the battery is placed at 45°C for 24h; after standing, the battery is placed on the formation cabinet, the formation temperature is set to 25±3°C, and the formation pressure is set to 500±50kgf, as shown in the following figure, and the specific formation method includes: Figure 2

[0110] A. 0.5C constant current charging for 28min, the charging capacity is 23.4% SOC, and standing for 3min;

[0111] B. 0.05C constant current charging for 2h, the charging capacity is 7.5% SOC, and standing for 3min;

[0112] C. 0.1C constant current charging for 2h, the charging capacity is 15.5% SOC, and standing for 3min;

[0113] D. 0.5C constant current and constant voltage charging to 100% SOC, constant voltage cutoff current is 0.05C, and standing for 3-5 min;

[0114] E. 0.33C constant current discharging to 50% SOC, standing for 3-5 min, and formation ending.

[0115] Comparative Example 1

[0116] The positive electrode sheet is baked at 100°C for 12h, and the negative electrode sheet is baked at 80°C for 12h before assembly; the assembled battery is baked at 105°C for 12-24h, and the water content in the electrode sheet in the battery after baking is 102.5ppm; the electrolyte is injected and packaged, and the battery is placed at 45°C for 24h; after standing, the battery is placed on the formation cabinet, the formation temperature is set to 25±3°C, and the formation pressure is set to 500±50kgf, as shown in the following figure, and the specific formation method includes: Figure 2

[0117] ​​​A. 0.33C constant current and constant voltage charging to 90% SOC, constant voltage cutoff current is 0.05C, stand for 3-5min;

[0118] B. 0.33C constant current discharging to 50% SOC, stand for 3-5min, end of formation.

[0119] Comparative Example 2

[0120] The positive plate was baked at 100℃ for 12h, and the negative plate was baked at 80℃ for 12h before assembly; the assembled cell was baked at 105℃ for 12-24h, the moisture of the plate in the battery after baking was 96.5ppm; inject electrolyte and package, stand for 24h at 45℃; after standing, place the cell on the formation cabinet, set the formation temperature to 25±3℃, the formation pressure to 500±50kgf, as shown in the following table, the specific formation method includes: Figure 2

[0121] A. 0.5C constant current and constant voltage charging to 90% SOC, constant voltage cutoff current is 0.05C, stand for 3-5min;

[0122] B. 0.33C constant current discharging to 50% SOC, stand for 3-5min, end of formation.

[0123] The above examples 1-7 and comparative examples 1-2 are only different in the formation process, and the other steps are the same.

[0124] Test Example 1

[0125] The batteries formed by examples 1-7 and comparative examples 1-2 were tested for electrical performance under the same conditions, and the results are shown in Table 2.

[0126] Table 2 Comparison of electrical performance test results of examples 1-7 and comparative examples 1-2

[0127]

[0128] As can be seen from Table 2, compared with comparative examples 1-2, the battery capacity, initial efficiency and capacity retention rate of the battery after formation are significantly improved, the DCR growth rate is significantly reduced, indicating that the SEI film formed is more stable and the internal resistance is lower by adjusting the charge and discharge current ratio and the cutoff condition of examples 1-7; at the same time, the formation time can be greatly shortened, and the energy consumption can be reduced; in addition, the charge and discharge cutoff condition of this formation method is based on the charge capacity, and this method is suitable for any system of sodium ion battery, such as layer oxygen system, polyanion system, etc.

[0129] ​Having described various embodiments of the application, it is to be understood that the above description is meant to be illustrative only, and that many modifications and variations of the embodiments are possible without departing from the scope and spirit of the described embodiments. Many modifications and variations of the described embodiments are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the described embodiments can be practiced otherwise than as specifically described.

Claims

1. A sodium-ion battery formation method, characterized in that, The application relates to a method for preparing a lithium ion battery, comprising the following steps: vacuum baking positive and negative electrode sheets at a first temperature, assembling the electrode sheets into a battery cell; vacuum baking the battery cell at a second temperature, injecting liquid electrolyte into the battery cell, and ensuring that the second temperature is higher than the first temperature, and the moisture content of the battery cell before injection is less than or equal to 200 ppm; staticly placing the battery cell at a third temperature after injection, and ensuring that the third temperature is lower than the first temperature; forming the battery cell at a fourth temperature, and ensuring that the fourth temperature is lower than the third temperature, and the forming method is to adjust the charge and discharge current ratio and the cutoff condition of the battery cell multiple times, so that the solid-state electrolyte interface film of the battery is more stable and the internal resistance is lower.

2. The method of claim 1, wherein, The active material of the positive electrode sheet is layered oxide and / or polyanion; the active material of the negative electrode sheet is hard carbon or a P-based negative electrode and hard carbon mixture; the first temperature is 80-110 DEG C, and the vacuum baking time at the first temperature is 8-12 h.

3. The method of claim 1, wherein, the second temperature is 90-110 DEG C, and the vacuum baking time at the second temperature is 12-24 h.

4. The method of claim 1, wherein, the third temperature is 45-55 DEG C, and the static placing time at the third temperature is 12-48 h.

5. The method of claim 1, wherein, the fourth temperature is 22-28 DEG C, and the forming pressure is 450-550 kgf.

6. The method of claim 1, wherein, the method for adjusting the charge and discharge current ratio and the cutoff condition of the battery cell multiple times comprises the following steps: after the battery cell is charged to a pre-film forming potential according to a first charging condition, the battery cell is statically placed for a first preset time, and the pre-film forming potential is a first forming condition; after the battery cell is charged to a second forming condition according to a second charging condition, the battery cell is statically placed for a second preset time; after the battery cell is charged to a third forming condition according to a third charging condition, the battery cell is statically placed for a third preset time; after the battery cell is charged to a fourth forming condition according to a fourth charging condition, the battery cell is statically placed for a fourth preset time; after the battery cell is discharged to a cutoff condition according to a discharging condition, the battery cell is statically placed for a fifth preset time.

7. The method of claim 6, wherein, the first charging condition is to charge the battery cell at a current of 0.33C-0.7C; the first forming condition is that the SOC of the battery cell is 23%-28%; the first preset time is 3-5 min.

8. The method of claim 6, wherein, the second charging condition is to charge the battery cell at a current of 0.03C-0.07C; the second forming condition is that the SOC of the battery cell is 3.5%-12.0%; the second preset time is 3-5 min.

9. The method of claim 6, wherein, the third charging condition is to charge the battery cell at a current of 0.08C-0.12C; the third forming condition is that the SOC of the battery cell is 7.5%-24.0%; the third preset time is 3-5 min. the fourth charging condition is to charge the battery cell at a current of 0.15C-0.5C; the fourth forming condition is that the cutoff SOC of the battery cell is 0.05C, and the entire charging capacity is greater than or equal to 90% SOC; the fourth preset time is 3-5 min.

10. The method of claim 6, wherein, the discharging condition is to discharge the battery cell at a current of 0.3C-0.5C; the cutoff condition is that the SOC of the battery cell is 40%-60%; the fifth preset time is 3-5 min.

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