Battery standing method after electrolyte injection, battery manufacturing method, and battery

Abstract

The application discloses a battery liquid injection post-static method, a battery manufacturing method and a battery. The battery liquid injection post-static method comprises the following steps: connecting a battery after liquid injection to an external circuit to make the battery discharge, the resistance value of the external circuit is X, and the X>0; and the battery is static. After electrolyte is injected into the battery, the battery is connected to the external circuit, so that the positive and negative electrodes of the battery can form electronic conduction through the external circuit, the electrolyte flow resistance can be reduced, and the infiltration efficiency can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and more specifically, to a method for allowing a battery to stand after electrolyte injection, a battery manufacturing method, and a battery. Background Technology

[0002] In related technologies, during the lithium-ion battery production process, after the electrolyte is injected into the battery casing, the battery needs to be left to stand to allow the electrolyte to wet the separator and the internal pores of the electrodes. However, current battery standing times are relatively long, resulting in low battery production efficiency.

[0003] Therefore, a new technical solution is needed to solve the above-mentioned technical problems. Summary of the Invention

[0004] One objective of this invention is to provide a new technical solution for a battery liquid filling and subsequent static storage method.

[0005] According to a first aspect of the present invention, a method for allowing a battery to stand after electrolyte filling is provided. This method includes: After the electrolyte injection is completed, the battery is electrically connected to an external circuit to discharge the battery. The resistance value of the external circuit is X, where X > 0. Let the battery rest. Optionally, 0 < X ​​≤ 9000Ω.

[0006] Optionally, the battery may be left to stand at a temperature of 35°C to 55°C.

[0007] Optionally, the battery is left to discharge for 10 to 100 hours.

[0008] Optionally, the battery includes one of liquid lithium iron phosphate battery, solid lithium iron phosphate battery, lithium cobalt oxide battery or ternary lithium battery.

[0009] Optionally, during the battery static discharge process, if the battery's termination voltage is greater than a first preset value within a first preset time period, the battery static discharge ends; or, if the battery static discharge time reaches the first preset time, the battery static discharge ends.

[0010] Optionally, the resistance value changes at intervals during the battery's static discharge process.

[0011] Optionally, the resistance value gradually increases.

[0012] Optionally, during the battery's static discharge process, if the battery's termination voltage is greater than a second preset value, the resistance value is increased; if the battery's termination voltage is greater than a first preset value, the battery static discharge process ends. Wherein, the first preset value is greater than the second preset value.

[0013] Optionally, during the battery's static discharge process, if the battery's discharge time is greater than a second preset time under the same resistance value, then the battery static discharge process ends.

[0014] According to a second aspect of this application, a battery manufacturing method is provided. The battery manufacturing method includes: allowing the battery to stand after electrolyte injection using the post-electrolyte-filling and settling method described in the above embodiments.

[0015] Optionally, after the battery has been left to stand, it is subjected to a formation and capacity testing process.

[0016] According to a third aspect of this application, a battery is provided. This battery is manufactured using the battery manufacturing method described in the above embodiments.

[0017] One technical advantage of this application is that after the electrolyte is injected into the battery, the battery is connected to an external circuit, so that the positive and negative electrodes of the battery can form electronic conduction through the external circuit, which can reduce the resistance to electrolyte flow and improve the wetting efficiency.

[0018] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0020] Figure 1 This is a flowchart of a battery liquid filling and subsequent standing method according to an embodiment of this application.

[0021] Figure 2 This is a schematic diagram of the external circuit of a battery according to one embodiment of this application.

[0022] Figure 3 This is a schematic diagram illustrating the relationship between the number of charge-discharge cycles and the battery capacity of a battery according to one embodiment of this application. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0024] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0025] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0026] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0028] According to one embodiment of this application, a method for allowing a battery to stand after electrolyte filling is provided. Figure 1 As shown, the method for allowing the battery to stand after electrolyte filling includes: S100. After the electrolyte is injected, the battery is electrically connected to an external circuit to discharge it. The resistance of the external circuit is X, where X > 0. After injecting the electrolyte into the battery casing, the battery is connected to the external circuit, for example, by connecting the positive and negative terminals of the battery with a wire. The resistance of the external circuit is X > 0.

[0029] In this example, such as Figure 2 The diagram shows a battery connected to an external circuit. Uo is the battery's output voltage, which can be monitored in real-time using a voltage detection device. Uocv is the battery's open-circuit voltage. R Ω This is the resistance of the external circuit. U R Rp is the ohmic voltage drop across the resistor in the external circuit. Cp is the polarization resistor. Up is the polarization voltage across the polarization resistor. i is the current flowing through the battery.

[0030] S200. Allow the battery to stand. After connecting the battery to the external circuit, allow it to stand so that the electrolyte can fully wet the separator and the pores inside the electrode.

[0031] In this example, after the electrolyte is injected into the battery, the battery is connected to an external circuit, so that the positive and negative electrodes of the battery can form an electronic connection through the external circuit. This changes the charge balance in the electrodes when the external circuit is not connected, thereby changing the contact angle between the liquid and solid phases. This reduces the electrolyte flow resistance and helps to improve the wetting efficiency.

[0032] In one example, the resistance value of the external circuit is 0 < X ​​≤ 9000Ω. For example, the resistance value can be 100Ω, 1000Ω, 3000Ω, 6000Ω, or 9000Ω, etc. Those skilled in the art can determine the value according to the actual situation, and no specific limitation is made here.

[0033] In one example, the battery is left to stand at a temperature of 35°C to 55°C. For instance, after connecting the battery to an external circuit, it is left to stand in an environment of 35°C to 55°C; that is, the battery's standing temperature is 35°C to 55°C. This helps to further reduce the electrolyte flow resistance and improve the wetting efficiency. The standing temperature can further be 35°C to 45°C.

[0034] For example, the static temperature of the battery can be 35°C, 40°C, 45°C, 50°C or 55°C, etc., which can be determined by those skilled in the art according to the actual situation, and no specific limitation is made here.

[0035] In one example, the battery is left to discharge for 10 to 100 hours. After connecting the battery to an external circuit, it is left to stand for 10 to 100 hours; that is, the battery can be left to stand for 10 to 100 hours. This allows the electrolyte to better wet the internal structure of the battery. For example, the battery can be left to stand for 10, 20, 40, 50, 60, 80, or 100 hours, etc. Those skilled in the art can determine the appropriate timeframe based on the specific circumstances, and no specific limitation is made here.

[0036] In one example, the battery includes one of a liquid lithium iron phosphate battery, a solid lithium iron phosphate battery, a lithium cobalt oxide battery, or a ternary lithium battery. That is, when the liquid lithium iron phosphate battery, solid lithium iron phosphate battery, lithium cobalt oxide battery, or ternary lithium battery is at rest, it can be connected to an external circuit, thereby reducing the resistance to electrolyte flow and improving wetting efficiency.

[0037] In one example, during the battery's static discharge process, if the battery's termination voltage is greater than a first preset value within a first preset time period, then the battery static discharge ends; or, if the battery's static discharge time reaches the first preset time, then the battery static discharge ends.

[0038] In this example, the battery discharge termination voltage is determined by connecting the battery to an external circuit after electrolyte injection and allowing it to stand. The battery will continue to discharge. An output voltage curve is obtained by monitoring the output voltage Uo in real time. The voltage before the output voltage curve begins to decline after a stable upward trend is the termination voltage. By collecting termination voltage data from multiple batteries, a normal distribution of the termination voltage is statistically analyzed using Minitab. Upper and lower limits of the termination voltage are set according to LSL = μ - 3σ and USL = μ + 3σ (where μ is the process mean and σ is the process standard deviation). Specifically, LSL represents the lower limit of the termination voltage, and USL represents the upper limit. USL is greater than LSL. The first preset value is the upper limit of the termination voltage (USL), and the second preset value is the lower limit of the termination voltage (LSL).

[0039] For example, taking a 300mAh lithium iron phosphate cylindrical battery with a steel casing, 32 batteries after electrolyte filling were placed at 35℃~55℃ with an external circuit resistance of 9000Ω for 72 hours of static discharge. The discharge curves yielded 32 termination voltage data points. Minitab was then used to statistically analyze the normal distribution of the termination voltages, and the upper and lower limits of the termination voltages were set according to LSL = μ - 3σ and USL = μ + 3σ (where μ is the process mean and σ is the process standard deviation). Of course, the type and number of batteries, as well as the static discharge conditions, can be determined by those skilled in the art based on actual circumstances, and are not specifically limited here.

[0040] In this example, during the battery's static discharge process, if the battery's termination voltage is greater than a first preset value within a first preset time, the static discharge ends and the battery immersion is deemed unqualified. Alternatively, after the battery's static discharge time reaches the first preset time, the static discharge also ends, and if the battery's termination voltage is greater than or equal to a second preset value and less than or equal to a first preset value, the battery immersion is deemed qualified.

[0041] As shown in Table 1, Table 1 illustrates the static discharge process of a battery in one embodiment. Step 1 is static discharge, Step 2 is the end, and USL is a first preset value. The first preset time is the battery's static discharge time, set to 48 hours. The resistance value of the external circuit is X, which can be 3000Ω. If the battery's termination voltage is greater than USL within the 48-hour static discharge time, the process proceeds to the next step, i.e., ends. Once the battery's static discharge time reaches 48 hours, the static discharge process also ends.

[0042] Table 1

[0043] In one example, the resistance value changes intermittently during the battery's static discharge process. During this process, the resistance value of the external circuit changes intermittently. That is, at a certain resistance, the battery is allowed to discharge for a period of time, then the resistance value is adjusted, and the battery is allowed to discharge again. This helps to improve the wetting effect of the electrolyte.

[0044] For example, the initial resistance of the external circuit is 1000Ω. After the battery is left to discharge for 10 hours, the resistance is adjusted to 2000Ω, and then the battery is left to discharge for another 10 hours. The resistance can be adjusted multiple times, for example, 2, 3, 4, or 5 times. The discharge time for each resistance value can be the same or different, as can be determined by those skilled in the art based on the actual situation, and no specific limitation is made here.

[0045] In one example, the resistance value gradually increases.

[0046] For example, the resistance value can be gradually increased, initially using low resistance to accelerate wetting, and then switching to high resistance to stabilize the interface. For example, the resistance value can be gradually increased in the order of 1000Ω, 2000Ω, 3000Ω, 5000Ω, 6000Ω, and 9000Ω. Those skilled in the art can determine this according to the actual situation, and no specific limitation is made here.

[0047] Alternatively, the resistance value can be gradually decreased. Those skilled in the art can determine this based on the specific circumstances, and no specific limitations are made here.

[0048] In one example, during the battery's static discharge process, if the battery's termination voltage is greater than a second preset value, the resistance value is increased; if the battery's termination voltage is greater than a first preset value, the static discharge process ends; wherein, the first preset value is greater than the second preset value.

[0049] In this example, during the battery's static discharge process, if the battery's termination voltage is greater than the second preset value, the resistance value is increased; if the battery's termination voltage is greater than the first preset value, the static discharge process ends. At the end of the static discharge, if the termination voltage is less than or equal to the first preset value and greater than or equal to the second preset value, the battery is considered to have passed the immersion test.

[0050] As shown in Table 2, Table 2 illustrates the static discharge process of a battery in another embodiment. LSL is the second preset value, USL is the first preset value, steps 1 to 5 represent static discharge, and step 6 is the end. In step 1, the resistance of the external circuit is 1000Ω, and the battery static time is set to 10 hours. If the termination voltage is greater than LSL, then proceed to step 2. In step 2, the resistance of the external circuit is adjusted to 2000Ω, and the battery static time is set to 10 hours. If the termination voltage is greater than LSL, then proceed to step 3. This process continues until step 5. In step 5, if the termination voltage is greater than USL, then proceed to step 6, which is the end. At the end of the static discharge, if the termination voltage is less than or equal to USL and greater than or equal to LSL, then the battery immersion is qualified.

[0051] In the battery's static discharge process, if the conditions for proceeding to the next step are not met in any of steps 1 to 5, the step will end directly after the static discharge time is over.

[0052] It should be noted that the number of steps can also be set to more, for example, 7, 8 or 9 steps, etc. Those skilled in the art can decide according to the actual situation, and no specific limitation is made here.

[0053] In this example, the sum of the resting times for each step is the total resting time of the battery, which ranges from 10 hours to 100 hours. The resting time for each step can be determined by those skilled in the art based on actual circumstances, and is not specifically limited here.

[0054] In this example, the resistance value can be gradually increased in steps 1 to 5. The specific resistance value for each step can be determined by those skilled in the art based on the actual situation, and is not specifically limited here.

[0055] Table 2

[0056] In one example, during the battery's static discharge process, if the battery's discharge time is greater than a second preset time at the same resistance value, then the battery static discharge ends.

[0057] For example, as shown in Table 2, in step 1, the second preset time is the battery resting time in step 1, that is, the second preset time is 10 hours. When the battery has been resting and discharging in step 1 for 10 hours, the battery resting ends. At this time, the battery's termination voltage has not reached LSL, and the battery immersion is unqualified.

[0058] In this example, as shown in Table 3, which is a data sheet for lithium iron phosphate steel-cased cylindrical batteries, the battery's resting conditions refer to the conditions under which the battery is left to rest and discharge after electrolyte filling. Specifically, 40℃ + 1000Ω indicates that the external circuit resistance is 1000Ω, and the battery is left to rest at 40℃ after electrolyte filling. 40℃ + MΩ indicates that the external circuit resistance is greater than 9000Ω, for example, 1MΩ, 2MΩ, or 5MΩ. 40℃ + open circuit indicates that the battery is not connected to an external circuit during resting. The time to reach the termination voltage indicates the battery's resting time. The number of cycles indicates the number of charge-discharge cycles performed after battery manufacturing; as shown in Table 3, the battery has undergone 1000 charge-discharge cycles after manufacturing. The retention capacity is the capacity after 1000 charge-discharge cycles. The capacity retention rate is the ratio of the battery's capacity during the last charge-discharge cycle to its capacity during the first charge-discharge cycle.

[0059] As shown in Table 3, by connecting an external circuit with a resistor between 1000Ω and 9000Ω, the battery maintained a high capacity retention rate after 1000 cycles. Furthermore, by connecting an external circuit with a resistor, the capacity retention rate after 1000 cycles was improved from 18.33% to 87.97%, increasing cycle life by 15.79%.

[0060] Table 3

[0061] According to another embodiment of this application, a battery manufacturing method is provided. The battery manufacturing method includes allowing the battery to stand after electrolyte injection using the battery electrolyte injection and subsequent settling method described in the above embodiment. The battery electrolyte injection and subsequent settling method includes electrically connecting the battery after electrolyte injection to an external circuit to discharge the battery, wherein the resistance value of the external circuit is X, where X > 0; and then allowing the battery to stand.

[0062] In this example, after the electrolyte is injected into the battery, the battery is connected to an external circuit, so that the positive and negative electrodes of the battery can form an electronic connection through the external circuit. This changes the charge balance in the electrodes when the external circuit is not connected, thereby changing the contact angle between the liquid and solid phases. This reduces the electrolyte flow resistance and helps to improve the wetting efficiency.

[0063] In one example, after the battery has been left to stand, it undergoes a formation and capacity testing process. By setting the time limit for the standing discharge step and the termination voltage as a condition, if the battery is deemed to have passed the wetting test after standing, the process can automatically switch to the next step, i.e., automatically enter the battery formation process, thereby improving battery production efficiency.

[0064] According to another embodiment of this application, a battery is provided. This battery is manufactured using the battery manufacturing method described in the above embodiments.

[0065] Example: Step 1: Battery fabrication: 1. The prepared battery is a 300mAh lithium iron phosphate steel-cased cylindrical battery. The battery dimensions are: diameter φ = 11.5mm, height H = 39.5mm. As shown in Table 4, Table 4 lists the cell design parameters. In the positive electrode slurry, LFP is the active material lithium iron phosphate, used for energy storage and release; SP is superconducting carbon black, a conductive agent; CNT is carbon nanotubes, a conductive agent; PVDF is polyvinylidene fluoride, a binder; and PVP is polyvinylpyrrolidone, a dispersant. In the negative electrode slurry… Table 4

[0066] 2. Wind, assemble, and bake the positive and negative electrode sheets.

[0067] 3. Electrolyte filling of the battery cell.

[0068] Step 2: After electrolyte filling, allow the cells to stand: As shown in Table 5, Table 5 presents the standing procedure after battery electrolyte filling: Table 5

[0069] Step 3: Cell formation: Table 6 shows the battery formation process. The ambient temperature during formation is set to 26°C. The formation process is performed on the battery of scheme AF in Table 5.

[0070] Table 6

[0071] Step 4: Cell wetting performance test: 1. Perform cyclic charging and discharging of the battery at a temperature of 26℃. As shown in Table 7, this table illustrates the cyclic charging and discharging process. Perform the cyclic charging and discharging process on the battery of scheme AF in Table 5.

[0072] As shown in Table 7, step 1 is rest, step 2 is constant current and constant voltage charging, step 3 is rest, and step 4 is constant current discharging. Step 5 is 1000 cycles, that is, step 5 is 1000 cycles from step 1 to step 4.

[0073] Table 7

[0074] like Figure 3 As shown, the horizontal axis represents the number of charge-discharge cycles, and the vertical axis represents the battery capacity. Figure 3 It is known that during the post-electrolysis cooling process, connecting the battery to an external circuit with a resistance value between 1000Ω and 9000Ω significantly improves the battery's cycle life. At 1000 cycles, the battery capacity remains greater than or equal to 230mAh. However, during the post-electrolysis cooling process, if the battery is in an open circuit or the external circuit resistance is set too high, the battery capacity decays significantly. At less than 900 cycles, the battery capacity will drop below 200mAh.

[0075] Table 8 shows the rate performance of the battery. In the resting configuration, 1kΩ-40℃-36h indicates that the external circuit resistance is 1kΩ, the resting temperature is 40℃, and the resting time is 36 hours. 9kΩ-40℃-36h indicates that the external circuit resistance is 9kΩ, the resting temperature is 40℃, and the resting time is 36 hours. Open circuit-40℃-36h indicates that the battery is not connected to an external circuit during resting, the resting temperature is 40℃, and the resting time is 36 hours.

[0076] As shown in Table 8, by connecting the battery to an external circuit while it is at rest, the 3C rate performance of the battery cell can be optimized from 88.83% to 89.50%, an increase of 0.67%. The 5C rate performance can be optimized from 82.95% to 85.67%, an increase of 2.77%. The 6C rate performance can be optimized from 79.90% to 82.74%, an increase of 2.84%. The 8C rate performance can be optimized from 75.70% to 79.17%, an increase of 3.43%. The 3C rate performance improvement is 0.67%, the 5C rate performance improvement is 2.77%, the 6C rate performance improvement is 2.84%, and the 8C rate performance improvement is 3.43%.

[0077] Table 8

[0078] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0079] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A method for allowing a battery to stand after electrolyte filling, characterized in that, include: After the electrolyte injection is completed, the battery is electrically connected to an external circuit to discharge the battery. The resistance value of the external circuit is X, where X > 0. Let the battery stand still.

2. The battery electrolyte filling and subsequent standing method according to claim 1, characterized in that, 0 < X ​​≤ 9000Ω.

3. The battery electrolyte filling and subsequent standing method according to claim 1, characterized in that, The battery is left to stand at a temperature of 35°C to 55°C.

4. The battery electrolyte filling and subsequent standing method according to claim 1, characterized in that, The battery is left to discharge for 10 to 100 hours.

5. The battery electrolyte filling and subsequent standing method according to claim 1, characterized in that, The battery includes one of the following: liquid lithium iron phosphate battery, solid lithium iron phosphate battery, lithium cobalt oxide battery, or ternary lithium battery.

6. The battery electrolyte filling and subsequent standing method according to claim 1, characterized in that, During the battery's static discharge process, if the battery's termination voltage is greater than a first preset value within a first preset time period, the static discharge of the battery ends; or, if the battery's static discharge time reaches the first preset time, the static discharge of the battery ends.

7. The battery electrolyte filling and subsequent standing method according to claim 1, characterized in that, During the process of the battery being left to discharge, the resistance value changes at intervals.

8. The battery electrolyte filling and subsequent standing method according to claim 7, characterized in that, The resistance value gradually increases.

9. The battery electrolyte filling and subsequent standing method according to claim 7, characterized in that, During the battery's static discharge process, if the battery's termination voltage is greater than a second preset value, the resistance value is increased; if the battery's termination voltage is greater than a first preset value, the static discharge process ends. Wherein, the first preset value is greater than the second preset value.

10. The battery electrolyte filling and subsequent standing method according to claim 9, characterized in that, During the battery's static discharge process, if the battery's discharge time is greater than a second preset time at the same resistance value, the static discharge of the battery ends.

11. A method for manufacturing a battery, characterized in that, The battery after electrolyte injection is allowed to stand using the method described in any one of claims 1 to 10.

12. The battery manufacturing method according to claim 11, characterized in that, After the battery has been left to stand, it undergoes a formation and capacity testing process.

13. A battery, characterized in that, It is manufactured using the battery manufacturing method described in claim 11 or 12.

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