Lithium capacitor constant-high-temperature electrochemical lithium pre-embedding activation method

Abstract

The invention relates to a lithium capacitor constant-high-temperature electrochemical lithium pre-embedding activation method which specifically comprises the following steps: S1, manufacturing a lithium capacitor cell: winding a negative plate, a copper foil, a lithium foil, a diaphragm and a positive plate into a flat shape, forming a winding cell unit with a plurality of layers of negative plates and positive plates, and combining a plurality of winding cell units into the lithium capacitor cell; s2, vacuum liquid injection; s3, lithium embedding activation: clamping the lithium capacitor cell subjected to liquid injection in the step S2 by adopting a clamping restraint, and enabling a positive electrode and a negative electrode to extend out; then, the whole lithium capacitor is placed in a constant-high-temperature box, the temperature is adjusted to 60-80 DEG C, a micro-current signal is sent to the lithium capacitor cell through an electrochemical workstation, and the lithium foil is embedded into the negative electrode through perturbation of the electrochemical signal; and outputting a voltage signal through the electrochemical workstation, and judging whether lithium intercalation is completed or not by utilizing a voltage value. According to the constant-high-temperature electrochemical lithium pre-embedding activation method for the lithium capacitor, the lithium pre-embedding state can be monitored in real time, the time spent on lithium pre-embedding is short, and the lithium embedding efficiency and the success rate are effectively improved.

Description

Technical Field

[0001] The invention relates to the field of lithium capacitor manufacturing, and in particular to a constant high temperature electrochemical pre-embedded lithium activation method for a lithium capacitor. Background Art

[0002] Lithium-ion capacitor (LIC) is a hybrid capacitor, a hybrid electrochemical energy storage device, and an asymmetric supercapacitor. It combines the embedding mechanism of the lithium-ion battery anode and the double-layer mechanism of the electric double-layer capacitor (EDLC) cathode, so the anode is the same as the positive electrode of the lithium-ion battery, and the cathode is the same as the negative electrode of the supercapacitor; the lithium-ion capacitor is assembled by placing the battery-type negative electrode and the capacitor-type positive electrode in an organic lithium salt solution. It has both the high power characteristics of supercapacitors and the high energy density of lithium-ion batteries, and has broad application prospects in smart grids, rail transit, new energy vehicles and other fields. Because lithium-ion capacitors combine high energy density and high power density, they do not require additional storage devices in various applications, thereby reducing costs.

[0003] Carbon materials are the preferred electrode materials for lithium-ion capacitors due to their wide availability, low price and stable performance. Therefore, carbon-based lithium-ion capacitors have competitive industrial prospects. Among them, negative electrode pre-lithium embedding technology has a decisive influence on the electrochemical performance of carbon-based lithium-ion capacitors.

[0004] The traditional negative electrode pre-embedded lithium is to place the lithium foil between the two coils and at the ends and close to the negative electrode after stacking, and then place it in a tray after the battery cell is filled and sealed. The tray with the battery cell is kept stationary in a constant temperature box, and then the tray is taken out every 24 hours. The voltage of the battery cell is tested one by one, and the completion of the pre-embedded lithium is judged based on the voltage situation. It usually takes at least a week to complete the pre-embedded lithium, and incomplete pre-embedded lithium may occur. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a constant high temperature electrochemical pre-lithium insertion activation method for lithium capacitors, which can monitor the pre-lithium insertion state in real time, and the pre-lithium insertion takes a short time, effectively improving the lithium insertion efficiency and success rate.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a constant high temperature electrochemical pre-embedded lithium activation method for lithium capacitors, which is specifically carried out in the following steps:

[0007] S1. Manufacturing lithium capacitor cells

[0008] The negative electrode sheet, copper foil, lithium foil, separator and positive electrode sheet are wound into a flat shape, and then a core unit is formed with several layers of negative electrode sheets and positive electrode sheets. Multiple core units are combined into a lithium capacitor cell.

[0009] S2, Vacuum injection

[0010] The lithium capacitor cell is placed in a sealed cavity, the sealed cavity is evacuated, and then a proper amount of electrolyte is injected; during the evacuation process, the lithium capacitor cell and the electrolyte are fully infiltrated;

[0011] S3, lithium insertion activation

[0012] The S2-filled lithium capacitor cell is clamped and restrained, with the positive and negative poles extending from both ends of the lithium capacitor cell; then, the whole is placed in a constant temperature box, the temperature is adjusted to 60-80°C, and a micro-current signal is given to the lithium capacitor cell through an electrochemical workstation. The lithium foil is quickly embedded into the negative electrode through electrochemical signal perturbation; during the process, a voltage signal is output through the electrochemical workstation, and the voltage value is used to determine whether the lithium embedding is completed.

[0013] In step S1, the number of positive electrode sheets and negative electrode sheets in each winding core unit is 8 to 12 layers.

[0014] In step S1, the lithium capacitor cell is composed of 2 to 4 winding core units.

[0015] In step S1, the copper foil and the lithium foil are respectively cut into rolls to form a copper foil roll and a lithium foil roll; the widths of the copper foil roll and the lithium foil roll are respectively 1 to 2 cm; the width of the copper foil roll is greater than the width of the lithium foil roll by 4 to 10 mm.

[0016] In step S1, the copper foil and the lithium foil are 2 to 5 mm inside the edge of the negative electrode sheet.

[0017] In step S2, the electrolyte is injected into the chamber 2 to 3 times, and vacuum is applied each time the electrolyte is injected.

[0018] In step S3, electric clamps are provided in the constant temperature box, which are in contact with the positive and negative electrodes of the lithium capacitor cell respectively; and the portion where the electric clamps contact the constant temperature box is sealed.

[0019] In step S3, the microcurrent is 0.05 to 1 mA.

[0020] Advantages of the present invention: The constant high temperature electrochemical pre-embedded lithium activation method of a lithium capacitor of the present invention can monitor the pre-embedded lithium state in real time, and the pre-embedded lithium takes a short time, thereby effectively improving the lithium embedding efficiency and success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A simplified flow chart of the process of manufacturing a lithium capacitor cell in a lithium capacitor constant-temperature electrochemical pre-embedded lithium activation method of this embodiment;

[0022] Figure 2 A simplified schematic diagram of the vacuum liquid injection process in a lithium capacitor constant-temperature electrochemical pre-embedded lithium activation method of this embodiment;

[0023] Figure 3 It is a simplified schematic diagram of the lithium insertion activation process in a lithium capacitor constant high temperature electrochemical pre-lithium insertion activation method of this embodiment. DETAILED DESCRIPTION

[0024] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0025] Example

[0026] Please refer to Figures 1 to 3 As shown, this embodiment provides a method for activating lithium capacitor pre-embedded with lithium at constant high temperature electrochemically, which is specifically performed in the following steps:

[0027] S1. Manufacturing lithium capacitor cells:

[0028] The negative electrode sheet, copper foil, lithium foil, separator and positive electrode sheet are wound into a flat shape, and then a core unit is formed with several layers of negative electrode sheets and positive electrode sheets. Multiple core units are combined into a lithium capacitor cell.

[0029] S2, Vacuum injection:

[0030] The lithium capacitor cell is placed in a sealed cavity, the sealed cavity is evacuated, and then a proper amount of electrolyte is injected; during the evacuation process, the lithium capacitor cell and the electrolyte are fully infiltrated;

[0031] S3, lithium insertion activation:

[0032] The S2-filled lithium capacitor cell is clamped and restrained, with the positive and negative poles extending from both ends of the lithium capacitor cell. Then, the whole cell is placed in a constant temperature box, the temperature is adjusted to 60-80°C, and a micro-current signal is given to the lithium capacitor cell through an electrochemical workstation. The lithium foil is quickly embedded into the negative electrode through electrochemical signal perturbation. During the process, a voltage signal is output through the electrochemical workstation, and the voltage value is used to determine whether the lithium insertion is completed. When the voltage signal reaches 2.5V, it is determined that the lithium insertion is completed and the activation is ended.

[0033] In step S1 of this embodiment, the number of positive electrode sheets and the number of negative electrode sheets in each winding core unit are 8 to 12 layers respectively.

[0034] In step S1 of this embodiment, the lithium capacitor cell is composed of 2 to 4 winding core units.

[0035] In step S1 of this embodiment, the copper foil and the lithium foil are respectively cut into rolls to form a copper foil roll and a lithium foil roll; the width of the copper foil roll and the lithium foil roll are 1 to 2 cm respectively; the width of the copper foil roll is greater than the width of the lithium foil roll by 4 to 10 mm. In order to fully dissolve the lithium foil and insert the lithium completely, the lithium foil needs to fully contact the electrolyte, which can only be achieved at the outer edge of the roll core, so the lithium foil is as narrow and long as possible, and the lithium foil must be completely attached to the copper foil. In order to prevent errors, the width of the copper foil is slightly larger than the width of the lithium foil.

[0036] In step S1 of this embodiment, the copper foil and the lithium foil are 2 to 5 mm inside the edge of the negative electrode sheet. This design is also to enable the lithium foil to fully contact the electrolyte.

[0037] In step S2 of this embodiment, the electrolyte is injected into the chamber 2 to 3 times, and the chamber is vacuumed each time the electrolyte is injected.

[0038] In step S3 of this embodiment, electric clamps are provided in the constant temperature box, which are in contact with the positive and negative electrodes of the lithium capacitor cell respectively; and the portion where the electric clamps contact the constant temperature box is sealed.

[0039] In step S3 of this embodiment, the microcurrent is 0.05-1 mA. The microcurrent provides an electrical signal, which helps to deeply pre-embed lithium. A lower current can reduce the formation of lithium dendrites, but the pre-lithiation time will be significantly extended. Too high a current can increase the formation of lithium dendrites and cause serious capacity loss of lithium capacitors.

[0040] A constant high temperature electrochemical pre-embedded lithium activation method for a lithium capacitor of the present embodiment can monitor the pre-embedded lithium state in real time, and the pre-embedded lithium takes a short time, which effectively improves the lithium embedding efficiency and success rate; by adopting electrochemical activation, a stable SEI layer can be formed on the electrode surface by directly contacting lithium metal with the electrode material, thereby inhibiting volume expansion and reducing local stress.

[0041] The above embodiments should not limit the present invention in any way, and any technical solutions obtained by equivalent replacement or equivalent conversion shall fall within the protection scope of the present invention.

Claims

1. A method for activating lithium pre-embedded in a lithium capacitor at a constant high temperature electrochemically, characterized in that: Follow these steps: S1. Manufacturing lithium capacitor cells The negative electrode sheet, copper foil, lithium foil, separator and positive electrode sheet are wound into a flat shape, and then a core unit is formed with several layers of negative electrode sheets and positive electrode sheets. Multiple core units are combined into a lithium capacitor cell. S2, Vacuum injection The lithium capacitor cell is placed in a sealed cavity, the sealed cavity is evacuated, and then a proper amount of electrolyte is injected; during the evacuation process, the lithium capacitor cell and the electrolyte are fully infiltrated; S3, lithium insertion activation The S2-filled lithium capacitor cell is clamped and restrained, with the positive and negative poles extending from both ends of the lithium capacitor cell; then, the whole is placed in a constant temperature box, the temperature is adjusted to 60-80°C, and a micro-current signal is given to the lithium capacitor cell through an electrochemical workstation. The lithium foil is quickly embedded into the negative electrode through electrochemical signal perturbation; during the process, a voltage signal is output through the electrochemical workstation, and the voltage value is used to determine whether the lithium embedding is completed.

2. A lithium capacitor constant high temperature electrochemical pre-embedded lithium activation method according to claim 1, characterized in that: In step S1, the number of positive electrode sheets and negative electrode sheets in each winding core unit is 8 to 12 layers.

3. A lithium capacitor constant high temperature electrochemical pre-embedded lithium activation method according to claim 1, characterized in that: In step S1, the lithium capacitor cell is composed of 2 to 4 winding core units.

4. A lithium capacitor constant high temperature electrochemical pre-embedded lithium activation method according to claim 1, characterized in that: In step S1, the copper foil and the lithium foil are respectively cut into rolls to form a copper foil roll and a lithium foil roll; the widths of the copper foil roll and the lithium foil roll are respectively 1 to 2 cm; the width of the copper foil roll is greater than the width of the lithium foil roll by 4 to 10 mm.

5. A lithium capacitor constant high temperature electrochemical pre-embedded lithium activation method according to claim 1, characterized in that: In step S1, the copper foil and the lithium foil are 2 to 5 mm inside the edge of the negative electrode sheet.

6. A lithium capacitor constant high temperature electrochemical pre-embedded lithium activation method according to claim 1, characterized in that: In step S2, the electrolyte is injected into the chamber 2 to 3 times, and vacuum is applied each time the electrolyte is injected.

7. A lithium capacitor constant high temperature electrochemical pre-embedded lithium activation method according to claim 1, characterized in that: In step S3, electric clamps are provided in the constant temperature box, which are in contact with the positive and negative electrodes of the lithium capacitor cell respectively; and the portion where the electric clamps contact the constant temperature box is sealed.

8. A lithium capacitor constant high temperature electrochemical pre-embedded lithium activation method according to claim 1, characterized in that: In step S3, the microcurrent is 0.05 to 1 mA.

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