Process for shortening capacity grading time of lithium battery

Abstract

The invention relates to a process for shortening capacity grading time of a lithium battery, which belongs to the field of polymer lithium ion batteries, and comprises the following steps: S1, first charging: adopting a stepped charging mode; s2, second-step discharging: changing low-current constant-current discharging into a large-current discharging and low-current discharging stacked processing step; and S3, third charging: firstly, 0.5 C constant current charging is performed for a specified time, then 0.2 C constant current discharging is performed for a small period of time, the battery voltage falling speed is increased, and finally the shipment voltages of the two working steps are consistent. According to the process for shortening the capacity grading time of the lithium battery, in order to ensure the consistency of the voltage of a shipment battery cell, a charging and discharging mode is adopted in a charging and discharging step, constant-current charging is firstly carried out to a certain value higher than the shipment voltage, then constant-current discharging is carried out for a small period of time, the battery voltage falling speed is increased, the time of a constant-voltage stage can be greatly shortened through the operation, and therefore the charging efficiency is improved; according to the invention, the stack processing step of large-current constant-current discharge and small-current constant-current discharge is adopted, so that the discharge time is shortened, and the capacity grading efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer lithium ion batteries, in particular to a process for shortening the capacity division time of lithium batteries. Background Art

[0002] The conventional capacity division process adopts the mode of charge-discharge-charge, first charge to the upper limit voltage at 0.5C constant current; discharge to the lower limit voltage (usually 3.0V) at 0.2C constant current; and finally discharge to the delivery voltage at 0.5C constant current. See Table 1-1 for details of the process steps.

[0003] "Charge for 5 minutes, talk for 2 hours", this slogan of VOVO has long been deeply rooted in people's hearts. The rapid increase of 44W-65W-125W charging power is inseparable from the adoption of FFC charging algorithm. FFC charging: increase the upper limit voltage of battery charging, and adjust the charging cut-off current accordingly, so that the charged amount is consistent with the conventional constant current process. Taking 4.45V pure cobalt battery as an example, it can be fast charged to 4.48V (the specific step current is determined by the battery system), and then charged at 4.48V constant voltage, with a cut-off current of about 0.08C (the specific value needs to be calibrated according to the battery system). Compared with conventional constant current charging, FFC charging has a larger cut-off current, which reduces the constant voltage time and greatly improves the charging efficiency.

[0004] For general soft-pack batteries, customers require the battery to be discharged at a constant current of 0.2C to 3.0V and the capacity to reach the nominal value. The discharge time of this process is as long as more than 300 minutes. For battery manufacturers, this is quite inefficient. To address this problem, the present invention adopts a superimposed process step of high-current constant-current discharge plus low-current constant-current discharge to shorten the discharge time and improve the capacity division efficiency. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a process for shortening the capacity division time of lithium batteries, which has the advantages of shortening the capacity division time, improving production and delivery efficiency, saving costs, etc. It solves the problem that general soft-pack batteries in the prior art require customers to discharge the battery at a constant current of 0.2C to 3.0V and the capacity reaches the nominal value. The discharge time of this process is as long as more than 300 minutes. For battery manufacturers, this is a problem of very low efficiency.

[0006] To achieve the above object, the present invention provides the following technical solution: A process for shortening the capacity division time of a lithium battery, comprising the following steps: S1 first step charging: using step charging method; S2 second step discharge: change from small current constant current discharge to large current discharge plus small current discharge superposition step; S3, the third step of charging: first charge at 0.5C constant current for a specified time, then discharge at 0.2C constant current for a short period of time to speed up the battery voltage drop, and finally make the shipping voltage of the two steps consistent.

[0007] Furthermore, steps S1, S2 and S3 are required to be completed in an environment with a temperature of 25 ± 5 degrees and a humidity dew point less than or equal to 70%.

[0008] Furthermore, in the step S1, the battery itself needs to be able to support 1.5C charging, 1.5C constant current charging to 4.1V, 1.3C to 4.25V, 1C to 4.45V, 0.7C constant current to 4.48V, and the cut-off current is 0.08C.

[0009] Furthermore, the cut-off current in step S1 is not fixed, and the cut-off current needs to be calibrated before determining the working step so that the amount of electricity charged in the two schemes remains consistent.

[0010] Furthermore, in step S2, the capacity division step is 0.2C discharge to 3.0V; the capacity division time step is shortened: 1C discharge to 3.0V, stand for one minute, wait for the voltage to rebound, and then 0.2C discharge to 3.0V.

[0011] Furthermore, in step S3, the battery is first charged at a constant current of 0.5C for a specified time, and then discharged at a constant current of 0.2C for a short period of time, so as to accelerate the battery voltage drop rate, and finally make the delivery voltage of the two steps consistent.

[0012] Furthermore, the time of the specified constant current charging time in step S3 is not fixed, and the charging time needs to be calibrated before determining the step so that the amount of electricity charged is slightly greater than that in the conventional capacity division step.

[0013] Compared with the prior art, the technical solution of this application has the following beneficial effects: The process of shortening the lithium battery capacity division time adopts a charging and discharging mode in the power replenishment step to ensure the consistency of the shipped battery cell voltage. First, constant current charging is performed to a certain value higher than the shipping voltage, and then constant current discharge is performed for a short period of time to accelerate the battery voltage drop rate (or it can be left for a period of time to wait for the voltage to naturally decrease). This operation can greatly shorten the time of the constant voltage stage, thereby improving the charging efficiency. The present invention adopts the superposition step of large current constant current discharge and small current constant current discharge to shorten the discharge time and improve the capacity division efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the system flow of the present invention; Figure 2 This is a schematic diagram of the comparison of charging efficiency in the first step of the present invention; Figure 3 A schematic diagram showing the comparison of discharge efficiency in the second step of the present invention; Figure 4 This is a schematic diagram for comparing charging efficiency in the third step of the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] See also Figure 1-4 In this embodiment, a process for shortening the lithium battery capacity division time includes the following steps: S1 first step charging: using step charging method; S2 second step discharge: change from small current constant current discharge to large current discharge plus small current discharge superposition step; S3, the third step of charging: first charge at 0.5C constant current for a specified time, then discharge at 0.2C constant current for a short period of time to speed up the battery voltage drop, and finally make the shipping voltage of the two steps consistent.

[0017] The present invention is a summary of the background technical problems and their improvement solutions. For details, please refer to the following Table 1-1: Conventional volume separation steps and Table 1-2: Shortened volume separation time steps. The following volume separation steps are required to be completed in an environment with a temperature of 25±5℃ and a humidity dew point ≤70%: In this embodiment, the process steps are compared with the following table:

[0018] Table 1-1: Conventional volume separation steps

[0019] Table 1-2: Steps to shorten the capacity division time In this embodiment, steps S1, S2 and S3 are required to be completed in an environment with a temperature of 25 ± 5 degrees and a humidity dew point less than or equal to 70%.

[0020] In this embodiment, the battery itself needs to be able to support 1.5C charging in a step charging method in step S1, 1.5C constant current charging to 4.1V, 1.3C to 4.25V, 1C to 4.45V, 0.7C constant current to 4.48V, and a cut-off current of 0.08C. The cut-off current in step S1 is not fixed, and the cut-off current needs to be calibrated before determining the step to keep the amount of electricity charged in the two schemes consistent.

[0021] In this embodiment, the capacity division step in step S2 is 0.2C discharge to 3.0V; the capacity division time step is shortened: 1C discharge to 3.0V, leave for one minute, wait for the voltage to rebound, and then discharge to 3.0V at 0.2C. In step S3, first 0.5C constant current charging for a specified time, and then 0.2C constant current discharge for a short period of time to speed up the battery voltage drop speed, and finally make the shipping voltage of the two steps consistent.

[0022] In this embodiment, the time of the constant current charging specified time in step S3 is not fixed. The charging time needs to be calibrated before the determination step so that the charged amount is slightly larger than the conventional capacity division step. The charging step adopts a charging and discharging mode, first charging with constant current to a certain value higher than the delivery voltage, and then discharging with constant current for a short period of time to speed up the battery voltage drop (or leaving it for a period of time to wait for the voltage to drop naturally). This operation can greatly shorten the time of the constant voltage stage, thereby improving the charging efficiency.

[0023] In this embodiment, the improvement effects of the first step of charging, the second step of discharging and the third step of charging compared with the conventional process steps are shown in the following table:

[0024] The beneficial effects of the above embodiments are: The process of shortening the lithium battery capacity division time, in order to ensure the consistency of the shipped battery cell voltage, the power replenishment step of the present invention adopts a charging and discharging mode, firstly charging with a constant current to a certain value higher than the shipping voltage, and then discharging with a constant current for a short period of time to speed up the battery voltage drop rate (or leaving it for a period of time to wait for the voltage to drop naturally). This operation can greatly shorten the time of the constant voltage stage, thereby improving the charging efficiency.

[0025] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0026] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A process for shortening the capacity division time of a lithium battery, characterized in that: The following steps are involved: S1 first step charging: using step charging method; S2 second step discharge: change from small current constant current discharge to large current discharge plus small current discharge superposition step; S3, the third step of charging: first charge at 0.5C constant current for a specified time, then discharge at 0.2C constant current for a short period of time to speed up the battery voltage drop, and finally make the shipping voltage of the two steps consistent.

2. A process for shortening the lithium battery capacity division time according to claim 1, characterized in that: The steps S1, S2 and S3 are all required to be completed in an environment with a temperature of 25 ± 5 degrees and a humidity dew point less than or equal to 70%.

3. A process for shortening the lithium battery capacity division time according to claim 1, characterized in that: In the step S1, the battery itself needs to be able to support 1.5C charging using a step charging method, 1.5C constant current charging to 4.1V, 1.3C to 4.25V, 1C to 4.45V, 0.7C constant current to 4.48V, and a cut-off current of 0.08C.

4. A process for shortening the lithium battery capacity division time according to claim 3, characterized in that: The cut-off current in step S1 is not fixed, and the cut-off current needs to be calibrated before determining the working step to make the amount of electricity charged in the two schemes consistent.

5. A process for shortening the lithium battery capacity division time according to claim 1, characterized in that: The capacity division step in step S2 is to discharge the battery to 3.0V at 0.2C. The capacity division time is shortened by discharging the battery to 3.0V at 1C, leaving it for one minute to wait for the voltage to rebound, and then discharging the battery to 3.0V at 0.2C.

6. A process for shortening the lithium battery capacity division time according to claim 1, characterized in that: In step S3, firstly charge with a constant current of 0.5C for a specified time, and then discharge with a constant current of 0.2C for a short period of time, so as to accelerate the voltage drop of the battery, and finally make the delivery voltage of the two steps consistent.

7. A process for shortening the lithium battery capacity division time according to claim 6, characterized in that: The time of the constant current charging specified time in step S3 is not fixed. The charging time needs to be calibrated before determining the step so that the charged amount is slightly greater than the conventional capacity division step.

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