CN109786874B - Capacity grading method of lithium ion battery - Google Patents
Capacity grading method of lithium ion battery Download PDFInfo
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- CN109786874B CN109786874B CN201811595844.XA CN201811595844A CN109786874B CN 109786874 B CN109786874 B CN 109786874B CN 201811595844 A CN201811595844 A CN 201811595844A CN 109786874 B CN109786874 B CN 109786874B
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Abstract
The invention discloses a capacity grading method of a lithium ion battery, which comprises the following steps: step one, performing constant current discharge on a battery to be subjected to capacity grading, wherein the discharge current in a constant current discharge stage is 0.1-0.6C; step two, performing constant-current constant-voltage charging and constant-current discharging on the battery subjected to constant-current discharging in the step one, wherein the charging current in the constant-current constant-voltage charging stage in the step two is 0.3-0.6C, the cut-off voltage is 3.75V, the cut-off current is 0.02C, and the discharging current in the constant-current discharging stage in the step two is 0.3-0.6C; and step three, performing constant current charging and constant current discharging on the battery subjected to the constant current and constant voltage charging and constant current discharging in the step two, wherein the charging current in the constant current charging stage in the step three is 0.3-0.6C, the cut-off voltage is 3.55V, and the discharging current in the constant current discharging in the step three is 0.3-0.6C.
Description
Technical Field
The invention relates to a capacity grading method of a lithium ion battery.
Background
With the development of economic society, people have increasingly increased energy requirements, and the limited storage of traditional fossil fuels and the environmental harmfulness in the production and use process all force people to find, develop and utilize new clean energy sources, such as solar energy, wind energy and the like. The utilization of new clean energy is bound to use high-capacity energy storage equipment, and lithium ion batteries are subjected to extensive commercial research due to excellent performance, and particularly, the development of the lithium ion battery industry is promoted due to the rapid development of the electric automobile industry after 2010. The lithium ion battery is generally classified according to the anode material, and the common anode material includes lithium cobaltate, lithium manganate, lithium nickelate, ternary material, lithium iron phosphate, and the like. The lithium iron phosphate battery occupies a higher market share by virtue of excellent safety performance, longer cycle life, higher technical maturity and industrialization advantages. In general, a lithium battery undergoes a chemical conversion process to form a solid electrolyte phase interface film (SEI film) on the interface between a carbon negative electrode and an electrolyte solution, and the quality of the SEI film directly affects the electrochemical performance of the battery. In order to stabilize the SEI film, multiple charge-discharge cycles are usually required in the capacity grading stage, and the discharge capacity of the process is taken as the standard of pack packaging, so that battery manufacturers need to research and summarize proper capacity grading process flows and parameters to ensure that the battery obtains the maximum capacity, the best stability and the longest service life. The multiple charging and discharging cycles in the capacity grading stage can greatly increase the production period of the battery and increase the energy consumption, so that the time consumption of the capacity grading process needs to be shortened on the basis of meeting the electrochemical performance of the battery.
Disclosure of Invention
The invention provides a capacity grading method of a lithium ion battery, which can realize the step of charging to 3.75V at a constant current and a constant voltage in the second stage, and can increase the battery capacity and the consistency of the capacity in a shorter time and improve the performance of the battery through the stabilizing effect of the process on an SEI film.
The invention adopts the following technical scheme: a method of capacity grading a lithium ion battery, the method comprising the steps of: step one, performing constant current discharge on a battery to be subjected to capacity grading, wherein the discharge current in a constant current discharge stage is 0.1-0.6C; step two, performing constant-current constant-voltage charging and constant-current discharging on the battery subjected to constant-current discharging in the step one, wherein the charging current in the constant-current constant-voltage charging stage in the step two is 0.3-0.6C, the cut-off voltage is 3.75V, the cut-off current is 0.02C, and the discharging current in the constant-current discharging stage in the step two is 0.3-0.6C; and step three, performing constant current charging and constant current discharging on the battery subjected to the constant current and constant voltage charging and constant current discharging in the step two, wherein the charging current in the constant current charging stage in the step three is 0.3-0.6C, the cut-off voltage is 3.55V, and the discharging current in the constant current discharging in the step three is 0.3-0.6C.
In the first step of the invention, constant current discharge is performed twice, and the current of the constant current discharge is 0.3-0.5C and 0.1-0.2C in sequence. The constant-current constant-voltage charging current and the constant-current discharging current adopted in the second step of the invention are equal in magnitude. The cut-off voltage of the constant current discharge in the first step is 2.0-2.5V, and the constant current discharge is kept for 1-5 min before the constant current discharge in the first step.
In the second step of the invention, the cut-off voltage of constant current discharge is 2.0-2.5V, and the constant current discharge is set aside for 1-5 min before the step of constant current discharge in the second step. In the third step of the method, the cut-off voltage of constant current discharge is 2.0-2.5V, and the standing time before the constant current discharge step in the first step is 1-5 min. In the second step of the invention, the shelf time before the step of constant-current constant-voltage charging is 1-5 min. In the third step of the invention, the standing time before the constant current charging step is 1-5 min. The battery to be subjected to capacity grading is a square aluminum shell power battery with a positive electrode material of lithium iron phosphate and a negative electrode material of artificial graphite.
The invention has the following beneficial effects: after the technical scheme is adopted, the constant-current constant-voltage charging in the step two of the invention is carried out to 3.75V, and the battery capacity and the capacity consistency can be increased in a shorter time and the battery performance can be improved through the stabilizing effect of the process on the SEI film.
Drawings
Fig. 1 shows the cell capacity at different capacity-grading steps.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
The invention discloses a capacity grading method of a lithium ion battery, which comprises the following steps: step one, performing constant current discharge on a battery to be subjected to capacity grading, wherein the discharge current in a constant current discharge stage is 0.1-0.6C, the constant current discharge in the step one adopts two times of constant current discharge, the currents of the two times of constant current discharge are 0.3-0.5C and 0.1-0.2C in sequence, the cut-off voltage of the constant current discharge in the step one is 2.0-2.5V, and the battery is placed for 1-5 min before the constant current discharge in the step one; step two, performing constant-current constant-voltage charging and constant-current discharging on the battery subjected to constant-current discharging in the step one, wherein the charging current in the constant-current constant-voltage charging stage in the step two is 0.3-0.6C, the cut-off voltage is 3.75V, the cut-off current is 0.02C, the discharging current in the constant-current discharging stage in the step two is 0.3-0.6C, the constant-current constant-voltage charging current and the constant-current discharging current adopted in the step two are equal in magnitude, the cut-off voltage in the constant-current discharging stage in the step two is 2.0-2.5V, the battery is placed for 1-5 min before the constant-current discharging step in the step two, and the placing time before the constant-current constant-voltage charging step in the step two is 1-5 min; and step three, performing constant current charging and constant current discharging on the battery subjected to constant current and constant voltage charging and constant current discharging in the step two, wherein the charging current in the constant current charging stage in the step three is 0.3-0.6C, the cut-off voltage is 3.55V, the discharging current in the constant current discharging stage in the step three is 0.3-0.6C, the cut-off voltage in the constant current discharging stage in the step three is 2.0-2.5V, the standing time before the constant current discharging step in the step three is 1-5 min, and the standing time before the constant current charging step in the step three is 1-5 min.
In fig. 1, the batteries used in the following examples and comparative examples are lithium ion batteries using lithium iron phosphate as a positive electrode material and artificial graphite as a negative electrode material, and the lithium ion batteries are formed and sealed according to the conventional manufacturing process and procedures thereof, and then subjected to capacity grading. Wherein the batteries used are mass-produced batteries with the same batch stability.
Example 1
The formed and sealed battery is subjected to capacity grading at room temperature, and the specific steps are as follows:
(1) performing a first stage, discharging to 2.5V at 1/3C for 3min, discharging to 2.5V at 0.2C for 5 min;
(2) performing a second stage, namely performing constant-current constant-voltage charging with current of 1/3C, stopping the voltage of 3.75V and stopping the current of 0.02C for 5min, and then discharging with current of 1/3C, stopping the voltage of 2.5V for 5 min;
(3) and in the third stage, constant current charging is carried out at 1/3C with the cut-off voltage of 3.55V, standing for 5min, constant current discharging is carried out at 1/3C with the cut-off voltage of 2.5V, and the capacity of the step is taken as the capacity of the grading step and standing for 3 min.
Comparative example 1
The formed and sealed battery is subjected to capacity grading at room temperature, and the specific steps are as follows:
(1) performing constant current discharge, discharging with 0.5C current with cutoff voltage of 2.5V for 3min, and standing with 0.2C with cutoff voltage of 2.5V for 5 min;
(2) And in the third stage, charging with a constant current of 0.5C and a cut-off voltage of 3.55V for 5min, then discharging with a constant current of 0.5C and a cut-off voltage of 2.5V, and taking the capacity of the step as the capacity of the grading step for 3 min.
Comparative example 2
(1) Performing a first stage, discharging to 2.5V with current of 1/3C, standing for 3min, discharging to 2.5V with current of 0.2C, and standing for 5 min;
(2) performing a second stage, namely, performing constant-current constant-voltage charging with current of 1/3C, stopping voltage of 3.55V and stopping current of 0.02C, standing for 5min, and then discharging with current of 1/3C, stopping voltage of 2.5V, and standing for 5 min;
(3) and in the third stage, constant current charging is carried out at 1/3C with the cut-off voltage of 3.55V, standing for 5min, constant current discharging is carried out at 1/3C with the cut-off voltage of 2.5V, and the capacity of the step is taken as the capacity of the grading step and standing for 3 min.
Comparative example 3
(1) Performing a first stage, discharging to 2.5V at 1/3C for 3min, discharging to 2.5V at 0.2C for 5 min;
(2) performing a second stage, performing constant-current constant-voltage charging with current of 1/3C, stopping voltage of 3.65V, stopping current of 0.02C, standing for 5min, and then discharging with current of 1/3C, stopping voltage of 2.5V, and standing for 5 min;
(3) And in the third stage, constant current charging is carried out at 1/3C with the cut-off voltage of 3.55V, standing for 5min, constant current discharging is carried out at 1/3C with the cut-off voltage of 2.5V, and the capacity of the step is taken as the capacity of the grading step and standing for 3 min.
The same batch of 110Ah mass-produced batteries were used, 9 batteries were selected and subjected to capacity grading according to the steps in example 1 and comparative examples 1, 2 and 3, and the results are shown in fig. 1, and it is clear that the capacity results of the batteries obtained by the capacity grading method in example 1 are better.
Claims (1)
1. A method of capacity grading a lithium ion battery, the method comprising the steps of: performing constant current discharge on a battery to be subjected to capacity grading, wherein the battery to be subjected to capacity grading is a square aluminum shell power battery with a positive electrode material being lithium iron phosphate and a negative electrode material being artificial graphite, the constant current discharge adopts two times of constant current discharge, the current of the two times of constant current discharge is 0.3-0.5C and 0.1-0.2C in sequence, the cut-off voltage of the constant current discharge is 2.0-2.5V, and the battery to be subjected to constant current discharge is placed for 1-5 min before the step of constant current discharge; step two, performing constant current and constant voltage charging and constant current discharging on the battery subjected to constant current discharging in the step one, wherein the charging current in the constant current and constant voltage charging stage in the step two is 0.3-0.6C, the cut-off voltage is 3.75V, the cut-off current is 0.02C, the discharging current in the constant current discharging in the step two is 0.3-0.6C, the cut-off voltage in the constant current discharging in the step two is 2.0-2.5V, the standing time before the constant current discharging step in the step two is 1-5 min, the standing time before the constant current and constant voltage charging step is 1-5 min, the step three, performing constant current charging and discharging on the battery subjected to constant current and constant voltage discharging in the step two, the charging current in the constant current charging stage in the step three is 0.3-0.6C, the cut-off voltage is 3.55V, the discharging current in the constant current discharging step three is 0.3-0.6C, and the cut-off voltage in the constant current discharging step three is 2.0-2V, and in the third step, the standing time before the constant-current charging step is 1-5 min.
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| CN110911757B (en) * | 2019-10-25 | 2020-11-10 | 合肥国轩高科动力能源有限公司 | Safe capacity grading method for ternary lithium battery |
| CN112467240B (en) * | 2020-12-21 | 2022-04-29 | 潍坊聚能电池有限公司 | High-temperature capacity grading and matching process of lithium ion battery |
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