Lithium supplementing method

Abstract

The invention discloses a lithium supplementing method, and relates to the field of lithium ion batteries. According to the specific implementation scheme, the method comprises the following steps: S1, mixing and flaking a positive electrode material and a negative electrode material, and laminating by using a diaphragm to obtain a dry battery cell with a positive electrode lug and a negative electrode lug; s2, introducing a third electrode on the side surface of the dry cell, wrapping the third electrode by using a diaphragm, and fixing the third electrode on the outer side of the dry cell by using an adhesive tape; s3, performing liquid injection on the packaged dry battery cell to obtain a battery cell before formation, and electrically connecting a negative electrode lug and a third electrode lug to two sides of an electric appliance respectively to form a primary battery loop; s4, after the first lithium supplement in the step S2, performing formation and capacity grading on the dry battery cell to obtain a battery cell finished product meeting the requirements; and after long-term work, the battery cell can be connected with the positive electrode lug and the third electrode to form a primary battery for supplementing active lithium, and a primary battery loop is disconnected after the lithium supplementing amount meeting the requirement is achieved. The method is simple and convenient to operate, the lithium precipitation phenomenon can be reduced, and the safety performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium replenishing method. Background Art

[0002] Unprecedented global warming and the depletion of fossil fuels have increased people's demand for renewable, clean and efficient energy, further promoting the development of energy storage systems. Since 1991, when Sony Corporation of Japan launched a commercial battery with LiCoO2 as the positive electrode and coke as the negative electrode, rechargeable lithium-ion batteries (LIBs) have become one of the most widely used electrochemical energy storage systems in portable devices and electric vehicles due to their high energy density, high operating voltage, no memory effect, strong high and low temperature adaptability and environmental friendliness. However, the existing technology can only replenish active lithium once, and cannot replenish lithium evenly and controllably, resulting in a decrease in the initial efficiency and energy density of lithium-ion batteries. Summary of the invention

[0003] Based on this, the present invention provides a lithium supplementation method to solve the problem that the prior art can only supplement active lithium once and cannot supplement lithium evenly and controllably.

[0004] The present invention provides a lithium supplementation method, comprising:

[0005] S1: After the positive electrode material and the negative electrode material are mixed and laminated, a diaphragm is used to laminate the sheets to obtain a dry battery cell with a positive electrode tab and a negative electrode tab;

[0006] S2: introducing a third electrode on the side of the dry cell, wrapping the third electrode with a separator and fixing the third electrode to the outside of the dry cell with tape, and encapsulating the dry cell;

[0007] S3: injecting liquid into the packaged dry battery cell to obtain a battery cell before formation, and electrically connecting the negative electrode tab and the third electrode tab to two sides of an electrical appliance to form a primary battery circuit;

[0008] S4: After the first lithium replenishment in step S2, the dry battery cell is subjected to chemical conversion to obtain a finished battery cell that meets the requirements; after long-term operation, the battery cell can be supplemented with active lithium by connecting the positive electrode tab and the third electrode to form a primary battery, and the primary battery circuit is disconnected after the required lithium replenishment amount is reached.

[0009] The third electrode is flush with the bottom of the dry cell.

[0010] The active material of the third electrode is a lithium sheet, and a copper sheet is used to lead the third electrode out of the battery cell casing.

[0011] The copper sheet and the lithium sheet are tightly attached by physical pressing and bonding, and the third electrode tab and the copper sheet are ultrasonically welded.

[0012] An ammeter for monitoring current is connected in series in the primary battery circuit, and a voltmeter for monitoring voltage is also connected in parallel in the primary battery circuit.

[0013] The electrical appliance of the primary battery circuit is a small light bulb of 0.1-15W.

[0014] When active lithium is supplemented before formation, the amount of lithium supplemented in the battery cell is controlled to be less than 6%.

[0015] When active lithium is supplemented before formation, the potential is monitored and the time when the original battery potential is greater than 2.0V is controlled to be less than 48 hours.

[0016] When the active lithium is replenished after the battery cell has been working for a long time, the amount of replenished lithium should be controlled to be less than 80% of the attenuated capacity.

[0017] The positive electrode material is selected from one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide and lithium manganese iron phosphate; the negative electrode material is selected from one of graphite, hard carbon, lithium titanate and silicon.

[0018] Beneficial effects: The present invention connects an ammeter in series in the primary battery circuit to monitor the current, and connects a voltmeter in parallel to monitor the voltage, so as to quantitatively determine the amount of lithium replenishment; after the first lithium replenishment, the battery cell is divided into different capacities to obtain a finished battery cell that meets the requirements; after long-term work, the battery cell can be connected to the positive electrode tab and the third electrode to form a primary battery for replenishing active lithium; when the required amount of lithium replenishment is reached, the primary battery circuit can be disconnected immediately, which is convenient to operate.

[0019] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to better understand the present invention and do not constitute a limitation of the present invention.

[0021] Figure 1 is a schematic diagram of a three-electrode structure provided according to the present invention;

[0022] Figure 2 is a schematic diagram of a primary battery circuit provided according to the present invention;

[0023] Figure 3 It is a line graph of data of embodiments and comparative examples provided according to the present invention. DETAILED DESCRIPTION

[0024] The following is a description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and conciseness, the description of well-known functions and structures is omitted in the following description.

[0025] The present invention provides a lithium supplementation method, comprising:

[0026] S1: After the positive electrode material and the negative electrode material are mixed and laminated, a separator is used to laminate the sheets to obtain a dry battery cell 2 having a positive electrode tab 3 and a negative electrode tab 4. It should be noted that:

[0027] The positive electrode material is selected from one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide and lithium manganese iron phosphate; the negative electrode material is selected from one of graphite, hard carbon, lithium titanate and silicon.

[0028] S2: Introduce a third electrode on the side of the dry cell 2, wrap the third electrode with a separator and fix the third electrode to the outside of the dry cell 2 with tape, and package the dry cell 2. It should be noted that:

[0029] The third electrode is flush with the bottom of the dry battery cell 2 .

[0030] When the lithium sheet 5a is flush with the bottom of the dry battery cell 2, the deformation of the dry battery cell 2 in the subsequent manufacturing process can be reduced, thereby reducing the thickness of the battery and improving the energy density; it helps to reduce the uneven stress inside the dry battery cell 2, thereby reducing the occurrence of side reactions inside the battery, reducing internal resistance, reducing lithium plating, and improving the safety performance of the battery.

[0031] The active material of the third electrode is a lithium sheet 5a, and a copper sheet 5b is used to lead the third electrode out of the battery cell housing 1.

[0032] The lithium sheet 5a is to be selected as a rectangle with a thickness of 0.1-1mm, a width of 10-50mm, and a length of 100-500mm, and is attached to the outermost layer of the dry battery cell 2 in a winding manner, flush with the bottom of the dry battery cell 2. This ensures that the overall space is occupied to the minimum and meets the needs of lithium replenishment;

[0033] The copper sheet 5b and the lithium sheet 5a are closely attached to each other by physical pressing and bonding, and the third electrode tab 5c and the copper sheet 5b are ultrasonically welded.

[0034] Physical pressing and bonding can ensure close contact between the copper sheet 5b and the lithium sheet 5a, and improve the electrical connection stability of the battery; ultrasonic welding completes welding through the heat generated by vibration friction, avoiding such damage and ensuring the quality and performance of the third electrode tab 5c.

[0035] S3: injecting liquid into the packaged dry cell 2 to obtain a cell before formation, and electrically connecting the negative electrode tab 4 and the third electrode tab 5c to both sides of the electrical appliance to form a primary battery circuit. It should be noted that:

[0036] An ammeter for monitoring current is connected in series in the primary battery circuit, and a voltmeter for monitoring voltage is also connected in parallel in the primary battery circuit.

[0037] An ammeter is connected in series in the loop to monitor the current, and a voltmeter is connected in parallel to monitor the voltage, so as to quantitatively determine the amount of lithium replenishment.

[0038] The third electrode 5 is connected to the positive electrode tab 3 and the negative electrode tab 4 through a conductive wire, the conductive wire and the third electrode 5 are electrically connected by welding, and the conductive wire and the positive electrode tab 3 and the negative electrode tab 4 are connected and disconnected by a conductive clamp.

[0039] S4: After the first lithium replenishment in step S2, the dry battery cell 2 is subjected to capacity conversion to obtain a battery cell product that meets the requirements; after long-term operation, the battery cell can be supplemented with active lithium by connecting the positive electrode tab 3 and the third electrode to form a primary battery, and the primary battery circuit is disconnected after the required lithium replenishment amount is reached.

[0040] The electrical appliance of the primary battery circuit is a small light bulb of 0.1-15W, which can be used to identify whether the lithium replenishment work is in progress.

[0041] When replenishing active lithium before formation, the amount of lithium replenished in the battery cell is controlled to be less than 6%. This ensures that the active lithium content of the entire battery cell product does not precipitate due to excessive precipitation during the first charging process, which can greatly improve the initial energy density of the battery cell product;

[0042] When active lithium is supplemented before formation, the potential is monitored and the time when the original battery potential is greater than 2.0V is controlled to be less than 48 hours.

[0043] The time when the potential of the primary battery is greater than 2.0 V is controlled to be less than 48 hours, so as to avoid the negative electrode tab 4 from being damaged.

[0044] When the active lithium is replenished after the battery cell has been working for a long time, the amount of replenished lithium should be controlled to be less than 80% of the attenuated capacity.

[0045] The present invention can realize the characteristics of replenishing active lithium at any time under different SOH (battery health status, often used to indicate the remaining life of the battery), the amount of lithium replenishment is controllable, and the lithium replenishment is uniform, and no other device is needed for lithium replenishment operation. When replenishing lithium, it is only necessary to connect the original battery circuit of the negative electrode tab 4 and the third electrode 5 or the original battery circuit of the positive electrode tab 3 and the third electrode 5. This scheme can also be simply implemented in the PACK (battery pack); replenishing active lithium at any time under different SOH conditions is reflected in that it can not only make up for the loss of active lithium formed by the SEI (solid electrolyte interface membrane) film during the first charging process in the initial stage, but also can replenish the loss of active lithium caused by the damage and regeneration of the SEI film at any time during the life cycle; the controllable amount of lithium replenishment is reflected in the presence of a voltmeter and an ammeter to monitor the capacity and voltage, and the integral of the current flowing in the original battery over time is the capacity of lithium replenishment. The voltmeter can accurately identify the potential of the initial negative electrode, and avoid damage to the negative electrode by limiting its residence time at a high potential.

[0046] Embodiment: With lithium iron phosphate as the positive electrode and graphite as the negative electrode, after mixing and sheeting, the 30A LFP / C dry battery cell 2 with a size of 72*155*237 is obtained by laminating, and the lithium sheet 5a with a thickness of 0.5mm, a width of 25mm, and a length of 150mm is attached to the outermost layer of the dry battery cell 2 in a winding manner, and the dry battery cell 2 is pulled out through the copper sheet 5b, and the above system is encapsulated by an aluminum-plastic film, and then the pre-formation battery cell is obtained by liquid injection, and the original battery circuit between the third electrode 5 and the negative electrode ear 4 is closed, and the integral value of the calculated current over time is read. When it is 1Ah, the original battery circuit is disconnected. After the capacity is divided, the off-line finished battery cell is obtained. After the 1C / 1C cycle is performed for 1000 weeks, the original battery circuit between the third electrode 5 and the positive electrode ear 3 is closed, and the integral value of the calculated current over time is read. When it is 1Ah, the original battery circuit is disconnected. It is cycled 1C / 1C for 1000 weeks.

[0047] Comparative example: lithium iron phosphate was used as the positive electrode and graphite was used as the negative electrode. After mixing and sheeting, the sheets were stacked to obtain a 30A LFP / C dry battery cell 2 with a size of 72*155*237. The above system was encapsulated by an aluminum-plastic film, and then the finished battery cell was obtained after liquid injection and fractionation. The 1C / 1C cycle was performed for 2000 cycles.

[0048] As shown in Table 1, short parameter data and interface comparison of the cell products during the manufacturing process and after the production line of the embodiment and the comparative example are shown. The lithium content of the embodiment before formation is one order of magnitude higher than that of the comparative example, the first efficiency is 3.5% higher, the energy density is 5.7Wh / kg higher, and the fully charged disassembly interface is uniform without lithium precipitation, indicating that the lithium-ion battery proposed by the present invention is uniformly replenished with lithium without concentrated lithium replenishment.

[0049] Table 1: Comparison of parameters of lithium-supplemented and non-lithium-supplemented battery cells

[0050] Negative electrode lithium content before formation / ppm First effect / % Energy densityWh / kg Offline full power disassembly interface Example 2297.5 95.2 191 Uniform interface, no lithium deposition Comparative Example 178.4 91.7 185.3 Uniform interface, no lithium deposition

[0051] like Figure 3 The data of the embodiment and the comparative example after they are offline are shown. The capacity retention rate curves of the two cells in the first 1000 cycles are basically overlapped, indicating that the placement of the device inside the cell has basically no effect on the cycle. After 1000 cycles, the capacity retention rate of the embodiment cell has a leap-like increase after the active lithium is supplemented, indicating that the lithium-ion battery provided by the present invention has obvious lithium supplementation effect, and can still be effectively cycled for 1000 cycles after the lithium supplementation is completed.

[0052] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A lithium supplementation method, characterized in that: include: S1: After the positive electrode material and the negative electrode material are mixed and laminated, a diaphragm is used to laminate the sheets to obtain a dry battery cell with a positive electrode tab and a negative electrode tab; S2: introducing a third electrode on the side of the dry cell, wrapping the third electrode with a separator and fixing the third electrode to the outside of the dry cell with tape, and encapsulating the dry cell; S3: injecting liquid into the packaged dry battery cell to obtain a battery cell before formation, and electrically connecting the negative electrode tab and the third electrode tab to two sides of an electrical appliance to form a primary battery circuit; S4: After the first lithium replenishment in step S2, the dry battery cell is subjected to chemical conversion to obtain a finished battery cell that meets the requirements; after long-term operation, the battery cell can be supplemented with active lithium by connecting the positive electrode tab and the third electrode to form a primary battery, and the primary battery circuit is disconnected after the required lithium replenishment amount is reached.

2. A lithium supplementation method according to claim 1, characterized in that: The third electrode is flush with the bottom of the dry cell.

3. A lithium supplementation method according to claim 2, characterized in that: The active material of the third electrode is a lithium sheet, and a copper sheet is used to lead the third electrode out of the battery cell casing.

4. A lithium supplementation method according to claim 3, characterized in that: The copper sheet and the lithium sheet are tightly attached by physical pressing and bonding, and the third electrode tab and the copper sheet are ultrasonically welded.

5. A lithium supplementation method according to claim 4, characterized in that: An ammeter for monitoring current is connected in series in the primary battery circuit, and a voltmeter for monitoring voltage is also connected in parallel in the primary battery circuit.

6. A lithium supplementation method according to claim 5, characterized in that: The electrical appliance of the primary battery circuit is a small light bulb of 0.1-15W.

7. A lithium supplementation method according to claim 6, characterized in that: When active lithium is supplemented before formation, the amount of lithium supplemented in the battery cell is controlled to be less than 6%.

8. A lithium supplementation method according to claim 7, characterized in that: When active lithium is supplemented before formation, the potential is monitored and the time when the original battery potential is greater than 2.0V is controlled to be less than 48 hours.

9. A lithium supplementation method according to claim 1, characterized in that: When the active lithium is replenished after the battery cell has been working for a long time, the amount of replenished lithium should be controlled to be less than 80% of the attenuated capacity.

10. A lithium supplementation method according to claim 1 or 9, characterized in that: The positive electrode material is selected from one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide and lithium manganese iron phosphate; the negative electrode material is selected from one of graphite, hard carbon, lithium titanate and silicon.

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