A high temperature pressure formation process for lithium ion capacitors

Abstract

The scheme discloses the technical field of lithium ion capacitor preparation, and relates to a lithium ion capacitor high-temperature pressure formation process, which comprises the following steps: (1) performing first charging on the battery after liquid injection and standing, charging the electric core to 40% SOC for the first time, the pressure of the first charging is 3000-4000N, the current is 0.02C-0.1C, and the temperature is 30-40 DEG C; (2) performing second charging on the electric core after the first charging and charging to 60% SOC, the pressure of the second charging is 1500-2500N, the current is 0.1C-0.2C, and the temperature is 30-40 DEG C; (3) performing third charging on the electric core after the second charging and charging to 80% SOC, the pressure of the third charging is 500-1000N, the current is 0.2C-0.4C, and the temperature is 40-50 DEG C. The process can significantly improve the cycle life and rate performance of the lithium ion capacitor.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion capacitor manufacturing technology, and specifically relates to a high-temperature pressure formation process for lithium-ion capacitors. Background Technology

[0002] Lithium-ion capacitors (LICs) are a new type of energy storage device. Compared to lithium-ion batteries, they have a relatively high specific power; and compared to traditional supercapacitors, they have a relatively high specific energy, thus showing excellent application prospects. Lithium-ion capacitors, as hybrid energy storage devices combining the advantages of both lithium-ion batteries and supercapacitors, have attracted widespread attention.

[0003] Before use, lithium-ion capacitors require a formation process. This formation serves two main purposes: firstly, it activates the active materials in the positive and negative electrodes, allowing the capacitor to reach its optimal charge / discharge state. Secondly, during formation, an SEI film (solid electrolyte interphase) forms on the negative electrode surface. Since the insertion / extraction of lithium ions inevitably passes through the SEI film covering the negative electrode, the uniformity and stability of this film significantly affect the capacity, cycle life, high and low temperature performance, self-discharge performance, stability, and safety of the lithium-ion capacitor, making it a crucial factor in determining its electrical performance. Traditional high-temperature pressure formation processes typically use high temperature (>35℃) and constant current (≥0.2C) to charge the battery to 100% SOC for formation. While this process can improve the electrochemical reaction rate and SEI film formation rate, the resulting SEI film is inconsistent, porous, and unstable. This significantly impacts the capacitor's cycle life, rate performance, and initial coulombic efficiency. Summary of the Invention

[0004] The present invention aims to provide a high-temperature pressure formation process for lithium-ion capacitors to improve the cycle life and rate performance of lithium-ion capacitors.

[0005] A high-temperature pressure formation process for lithium-ion capacitors in this solution includes the following steps:

[0006] (1) After the battery has been injected with liquid and allowed to stand, place it in a high-temperature pressure formation device for the first charge. The battery cell is charged to 40% SOC for the first charge. The pressure of the first charge is 3000-4000N, the current is 0.02C-0.1C, and the temperature is 30-40℃.

[0007] (2) Charge the battery cell after the first charge to 60% SOC. The pressure of the second charge is 1500-2500N, the current is 0.1C-0.2C, and the temperature is 30-40℃.

[0008] (3) Charge the battery cell after the second charge three times and charge it to 80% SOC. The pressure of the three charges is 500-1000N, the current is 0.2C-0.4C, and the temperature is 40-50℃.

[0009] The beneficial effects of this scheme are: by optimizing parameters such as pressure, current and charging degree, the prepared lithium-ion capacitor exhibits excellent coulombic efficiency, rate performance and extreme pulse discharge capability.

[0010] Furthermore, the battery cell is injected with electrolyte under conditions of 10–100 Pa and 30–50 °C, and then maintained under these conditions for 20–50 minutes after injection. This allows the electrolyte to quickly wet the diaphragm and electrode surfaces.

[0011] Furthermore, after electrolyte injection, the battery cell is placed in an environment of 30–50°C and left to stand for 4–8 hours before the first charge. This allows the electrolyte to completely wet the micropores of the electrode.

[0012] Furthermore, after the cell completes its first charge, lithium-rich electrolyte is added. The amount of lithium-rich electrolyte added is 9% to 15% of the amount of electrolyte injected during cell filling.

[0013] Furthermore, after the battery cell completes its second charge, it is replenished with lithium-rich electrolyte. The amount of lithium-rich electrolyte replenished is 5% to 10% of the amount of electrolyte injected during the battery cell's electrolyte filling process.

[0014] This is because the hard carbon anode material used in lithium-ion capacitors has a large irreversible capacity, which consumes a significant amount of lithium ions during the initial charging process. Therefore, to compensate for the irreversible capacity of the anode, a lithium-rich electrolyte needs to be added during the lithium-ion capacitor formation process to make up for the irreversible loss of lithium ions and improve the initial coulombic efficiency and capacity of the lithium-ion capacitor. Attached Figure Description

[0015] Figure 1 This is a comparison diagram of the positive electrode of an ion capacitor. Detailed Implementation

[0016] The following detailed description illustrates the specific implementation method:

[0017] Hard carbon is used as the negative electrode, lithium cobalt oxide as the positive electrode, Celgard 2300 membrane (made in the USA) as the separator, and 1 mol / L LiPF6 / EC+DMC+EMC (made in Shenzhen, 1:1:1) as the electrolyte. Then, the cells are assembled and finally assembled into a soft-pack lithium-ion capacitor. The cell shape is designed to be square.

[0018] Example 1

[0019] (1) The battery cell was injected with electrolyte (1mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)) under negative pressure (100pa) and high temperature (40℃) conditions. After the electrolyte injection was completed, it was kept under these conditions for 50min.

[0020] (2) Place the battery cell after the above liquid injection is completed in an environment of 40°C and let it stand for 8 hours.

[0021] (3) First charge: After the battery has been left to stand, place it on a high-temperature pressure formation device and charge the cell to 40% SOC using a certain pressure, current and temperature. The pressure at this stage is 3000N, the current is 0.02C, the temperature is 40℃, and the charging time is 4h. Then add 4g of LiPF6 rich lithium electrolyte (2mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)).

[0022] (4) Secondary charging: Continue charging the cell to 60% SOC. The pressure at this stage is 2000N, the current is 0.1C, the temperature is 40℃, and the charging time is 1h. Then add 2.5g of LiPF6 rich lithium electrolyte (2mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)).

[0023] (5) Three charging cycles: Increase temperature and current to charge the cell to 80% SOC, with pressure set at 1000N, current at 0.2C, temperature at 40℃, and charging time at 20min.

[0024] Example 2

[0025] (1) The battery cell was injected with electrolyte (1mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)) under negative pressure (100pa) and high temperature (40℃) conditions. After the electrolyte injection was completed, it was kept under these conditions for 50min.

[0026] (2) Place the battery cell after the above liquid injection is completed in an environment of 40°C and let it stand for 8 hours.

[0027] (3) After the battery has been left to stand, place it on a high-temperature pressure formation device and charge the cell to 50% SOC using a certain pressure, current and temperature. The pressure at this stage is 4500N, the current is 0.15C, the temperature is 40℃, and the charging time is 3h.

[0028] (4) Continue charging until the cell reaches 65% SOC. The pressure at this stage is 3000N, the current is 0.2C, the temperature is 40℃, and the charging time is 1h.

[0029] (5) Reduce pressure. Increase temperature and current to charge the cell to 85% SOC. The pressure is set to 1500N, the current to 0.25C, the temperature to 40℃, and the charging time to 15min.

[0030] Example 3

[0031] (1) The battery cell was injected with electrolyte (1mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)) under negative pressure (100pa) and high temperature (40℃) conditions. After the electrolyte injection was completed, it was kept under these conditions for 50min.

[0032] (2) Place the battery cell after the above liquid injection is completed in an environment of 40°C and let it stand for 8 hours.

[0033] (3) First charge: After the battery has been left to stand, place it on a high-temperature pressure formation device and charge the cell to 40% SOC using a certain pressure, current and temperature. The pressure at this stage is 3000N, the current is 0.02C, the temperature is 40℃, and the charging time is 4h.

[0034] (4) Secondary charging: Continue charging to charge the cell to 60% SOC. The pressure at this stage is 2000N, the current is 0.1C, the temperature is 40℃, and the charging time is 1h.

[0035] (5) Three charging cycles: Increase temperature and current to charge the cell to 80% SOC, with pressure set at 1000N, current at 0.2C, temperature at 40℃, and charging time at 20min.

[0036] Comparative Example 1

[0037] Traditional high-temperature pressure formation processes typically involve charging the battery to 100% SOC using a high-temperature (>35℃) and constant-current (≥0.2C) method, as detailed below:

[0038] (1) The battery cell was injected with electrolyte (1mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)) under negative pressure (100pa) and high temperature (40℃) conditions. After the electrolyte injection was completed, it was kept under these conditions for 50min.

[0039] (2) Place the battery cell after the above liquid injection is completed in an environment of 40°C and let it stand for 8 hours.

[0040] (3) After the battery has been left to stand, place it on a high-temperature pressure formation device and charge the cell to 100% SOC using a certain pressure, current and temperature. The pressure at this stage is 3000N, the current is 0.2C, the temperature is 40℃, and the charging time is 8h.

[0041] Comparative Example 2

[0042] (1) The battery cell was injected with electrolyte (1mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)) under negative pressure (100pa) and high temperature (40℃) conditions. After the electrolyte injection was completed, it was kept under these conditions for 50min.

[0043] (2) Place the battery cell after the above liquid injection is completed in an environment of 40°C and let it stand for 8 hours.

[0044] (3) First charge: After the battery has been left to stand, place it on a high-temperature pressure formation device and charge the cell to 40% SOC using a certain pressure, current and temperature. The pressure at this stage is 3000N, the current is 0.02C, the temperature is 40℃, and the charging time is 4h. Then add 4g of LiPF6 rich lithium electrolyte (2mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)).

[0045] (4) Secondary charging: Continue charging the cell to 60% SOC. The pressure at this stage is 2000N, the current is 0.1C, the temperature is 40℃, and the charging time is 1h. Then add 2.5g of LiPF6 rich lithium electrolyte (2mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)).

[0046] (5) Three charging cycles: Increase temperature and current to charge the cell to 80% SOC, with pressure set at 2000N, current at 0.1C, temperature at 40℃, and charging time at 1h.

[0047] (6) Four charging cycles: The battery cell is charged to 100% SOC using a certain pressure, current and temperature. The pressure at this stage is 3000N, the current is 0.2C, the temperature is 40℃, and the charging time is 8h.

[0048] Comparative Example 3

[0049] (1) The battery cell was injected with electrolyte (1mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)) under negative pressure (100pa) and high temperature (40℃) conditions. After the electrolyte injection was completed, it was kept under these conditions for 50min.

[0050] (2) Place the battery cell after the above liquid injection is completed in an environment of 40°C and let it stand for 8 hours.

[0051] (3) First charge: Continue charging to charge the cell to 60% SOC. The pressure at this stage is 2000N, the current is 0.1C, the temperature is 40℃, and the charging time is 1h. Then add 2.5g of LiPF6 rich lithium electrolyte (2mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)).

[0052] (4) Secondary charging: Increase the temperature and current to charge the cell to 80% SOC. The pressure is set to 1000N, the current is 0.2C, the temperature is 40℃, and the charging time is 20min.

[0053] Comparative Example 4

[0054] (1) The battery cell was injected with electrolyte (1mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)) under negative pressure (100pa) and high temperature (40℃) conditions. After the electrolyte injection was completed, it was kept under these conditions for 50min.

[0055] (2) Place the battery cell after the above liquid injection is completed in an environment of 40°C and let it stand for 8 hours.

[0056] (3) First charge: After the battery has been left to stand, place it on a high-temperature pressure formation device and charge the cell to 40% SOC using a certain pressure, current and temperature. The pressure at this stage is 3000N, the current is 0.02C, the temperature is 40℃, and the charging time is 4h. Then add 4g of LiPF6 rich lithium electrolyte (2mol / L LiPF6 / EC+DMC+EMC (Shenzhen product, 1:1:1)).

[0057] (4) Secondary charging: Increase the temperature and current to charge the cell to 80% SOC. The pressure is set to 1000N, the current is 0.2C, the temperature is 40℃, and the charging time is 20min.

[0058] Figure 1 The images show dissected positive electrode photographs of lithium-ion capacitors obtained through two formation methods. The positive electrode in the left image was prepared in Example 1, and the positive electrode in the right image was prepared in Comparative Example 1. Figure 1 It can be seen that the surface of the positive electrode obtained by the formation process in Example 1 did not show significant changes, while the surface of the electrode obtained by the formation process in Comparative Example 1 showed mottled marks and turned light yellow. This indicates the presence of impurities on the positive electrode surface, which may be related to lithium delithiation in the positive electrode, indicating that the proportion of active lithium loss in the battery is gradually increasing. This shows that although the traditional formation process can improve the electrochemical reaction rate and SEI film formation rate, it will significantly affect the cycle life, rate performance, and initial coulombic efficiency of the capacitor.

[0059] Performance verification

[0060] Lithium-ion capacitor coulombic efficiency test

[0061] The coulombic efficiency of the lithium-ion capacitors prepared in Example 1, Example 2, and Comparative Example 1 was tested, and the results are shown in Table 1:

[0062] Table 1. Coulombic efficiency test of lithium-ion capacitors

[0063]

[0064]

[0065] As can be seen from Table 1, the battery prepared using Example 1 of the present invention exhibits excellent first-efficiency. Compared with the prior art (Comparative Example 1), this formation process can improve the coulombic efficiency of lithium-ion capacitors by about 15.5%.

[0066] Lithium-ion capacitor cycle life test

[0067] The lithium-ion capacitors prepared in Example 1, Example 2, and Comparative Example 1 were subjected to cycle life tests, and the results are shown in Table 1:

[0068] Table 2. Cycle life test of lithium-ion capacitors

[0069] Example 1 3568 80.4 Example 2 2905 80.2 Example 3 3362 80.4 Comparative Example 1 2301 80.3 Comparative Example 2 2856 80.3 Comparative Example 3 2537 80.2 Comparative Example 4 2692 80.3

[0070] As can be seen from Table 2, compared with the prior art (Comparative Example 1), the lithium-ion capacitor prepared by the formation process of Example 1 of the present invention has a significantly improved cycle life, which is increased by 55.1%.

[0071] Lithium-ion capacitor internal resistance test

[0072] The internal resistance of the lithium-ion capacitors prepared in Example 1, Example 2, and Comparative Example 1 was tested, and the results are shown in Table 1:

[0073] Table 3 Internal Resistance Test of Lithium-ion Capacitors

[0074]

[0075]

[0076] Lithium-ion capacitor rate performance test

[0077] The rate performance of the lithium-ion capacitors prepared in Example 1, Example 2, and Comparative Example 1 was tested, and the results are shown in Table 3:

[0078] Table 4. Rate Performance Test of Lithium-ion Capacitors

[0079]

[0080] As can be seen from Tables 3 and 4, the internal resistance of the lithium-ion capacitor prepared by Example 1 is significantly reduced, and the rate performance is greatly improved. The capacity retention rate is as high as 86.4% under the 200C rate condition, while the capacity retention rate using the traditional formation process is only 75.3%.

[0081] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A lithium-ion capacitor high-temperature pressure formation process, characterized by: Includes the following steps: (1) After the battery has been injected with electrolyte and allowed to stand, place it on a high-temperature pressure formation device for the first charge. The battery cell is charged to 40% SOC for the first charge. The pressure of the first charge is 3000-4000N, the current is 0.02C-0.1C, and the temperature is 30-40℃. After the battery cell has completed the first charge, add lithium-rich electrolyte. The amount of lithium-rich electrolyte added is 9%-15% of the amount of electrolyte injected when the battery cell was injected with electrolyte. (2) Continue to charge the cell a second time to 60% SOC. The pressure of the second charge is 1500-2500N, the current is 0.1C-0.2C, and the temperature is 30-40℃. After the cell completes the second charge, add lithium-rich electrolyte. The amount of lithium-rich electrolyte added is 5%-10% of the amount of electrolyte injected when the cell was injected. (3) Continue to charge the battery cell three times and charge it to 80% SOC. The pressure of the three charges is 500-1000N, the current is 0.2C-0.4C, and the temperature is 40-50℃.

2. The high temperature pressure formation process for lithium ion capacitors of claim 1, wherein: The battery cell is injected with electrolyte under conditions of 10–100 Pa and 30–50 °C, and then kept under these conditions for 20–50 min after the electrolyte injection is completed.

3. The high temperature pressure formation process for lithium ion capacitors of claim 2, wherein: After the electrolyte injection is completed, place the battery cell in an environment of 30-50℃ for 4-8 hours before the first charge.

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