KR20140005799A - Method of inspecting for lithium ion secondary battery - Google Patents

Abstract

The purpose of the present invention is to provide a test method of a lithium ion secondary battery capable of shortening a battery leaving time which is necessary for voltage variation measurement while improving quality determination accuracy of a battery. The test method comprises; an initial discharge step (S304) which initially discharges a lithium ion secondary battery after the manufacture (S301) of the lithium ion secondary battery; an additional charge step (S305) which charges the lithium ion secondary battery discharged in the initial discharge step; an additional discharge step (S306) which discharges the lithium ion secondary battery charged in the additional charge step; and a voltage measuring step (S308, S310) which measures voltage of the lithium ion secondary battery after the additional discharge step. [Reference numerals] (AA) Start; (BB) No; (CC) Yes; (DD) End; (S301) Production of a battery; (S302) Initial charge; (S303) Aging; (S304) Initial discharge; (S305) Additional charge; (S306) Additional discharge; (S307) Charge of predetermined amounts; (S308) Measurement of initial voltage; (S309) Predetermined time neglect; (S310) Measurement of transition voltage; (S311) Calculation of voltage variation; (S312) Is a battery superior goods?; (S313) Shipment of a battery; (S314) Disuse of a battery

Description

METHOD OF INSPECTING FOR LITHIUM ION SECONDARY BATTERY [0002]

The present invention relates to a method of inspecting a lithium ion secondary battery.

In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide is desperately desired. In the automobile industry, there is a growing expectation for reduction of carbon dioxide emissions by introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs), and development of motor-driven secondary batteries, which hold the key to practical use thereof, .

As secondary batteries for automobiles, it is demanded to have extremely high output characteristics and high energy as compared with lithium ion secondary batteries for civilian use for cellular phones, notebook computers and the like. Therefore, lithium ion secondary batteries having the highest theoretical energy among all the batteries have attracted attention, and development is currently progressing rapidly.

In a screening test such as a short-circuit failure of a lithium ion secondary battery, the voltage of a battery to be charged, which is charged a predetermined amount after the first charge-discharge after the battery is manufactured, is measured as an initial voltage, . Then, based on the voltage fluctuation amount, the battery is judged as good or bad.

However, in such a screening test, there is a problem that the time required for the battery to be left to maintain the voltage measurement accuracy of the battery becomes long.

In addition, since the initial voltage and the voltage fluctuation amount of the battery also fluctuate due to the manufacturing variation of the battery, there is a problem that the accuracy of the positive / negative determination of the battery is deteriorated.

As a conventional technique for increasing the voltage measurement accuracy of a battery to be inspected and reducing the time for which the battery is left to stand, there is as follows. That is, by using the reference battery, the voltage difference between the inspected battery and the reference battery is measured to lower the measurement level of the battery, and the measurement resolution of the voltage fluctuation of the inspected battery is increased, (Patent Document 1).

Japanese Patent Application Laid-Open No. 2009-145137

However, although the above-described conventional technique can improve the measurement accuracy of the voltage of the battery, the deviation time of the battery due to the deviation of the battery voltage due to the manufacturing deviation of the battery increases and the accuracy of the determination of the battery is deteriorated Can not solve the problem.

In order to solve the above problems, an inspection method of a lithium ion secondary battery according to the present invention has an initial discharge step, an additional charge step, an additional discharge step, and a voltage measurement step. The initial discharging step is a step of discharging the lithium ion secondary battery first after the production thereof. The additional charging step is a step of charging the discharged lithium ion secondary battery in the initial discharging step. The additional discharging step is a step of discharging the charged lithium ion secondary battery in the additional charging step. The voltage measuring step is a step of measuring the voltage of the lithium ion secondary battery after the additional discharging step.

According to the inspection method of a lithium ion secondary battery according to the present invention, further charge and discharge are performed after the first discharge of the battery after the production. By such additional charging and discharging, the variation of the battery voltage can be reduced by activating both electrodes by the exchange of lithium ions in each electrode and reducing the in-plane distribution deviation of lithium ions. As a result, it is possible to improve the accuracy of determining whether the battery is positive or negative, and shorten the battery leaving time required for the voltage fluctuation amount measurement.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external view of a stacked-layer type lithium ion secondary battery to be inspected in a method of inspecting a lithium ion secondary battery according to a first embodiment of the present invention. FIG.
2 is a sectional view of a stacked lithium ion secondary battery.
3 is a flowchart showing a method of inspecting a lithium ion secondary battery according to the first embodiment of the present invention.
FIG. 4 is a graph showing a voltage fluctuation amount of a lithium ion secondary battery when a method of inspecting a lithium ion secondary battery according to an embodiment of the present invention is performed, compared with the conventional example. FIG.
5 is a flowchart showing a method of inspecting a lithium ion secondary battery according to a second embodiment of the present invention.
6 is a flowchart showing a method of inspecting a lithium ion secondary battery according to a third embodiment of the present invention.
7 is a flowchart showing a method of inspecting a lithium ion secondary battery according to a fourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method of inspecting a lithium ion secondary battery according to the present invention will be described in detail with reference to the accompanying drawings.

(1st embodiment)

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an external view of a lithium ion secondary battery to be inspected in a lithium ion secondary battery inspection method according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the lithium ion secondary battery shown in Fig. Hereinafter, the stacked lithium ion secondary battery will be described as an example of the battery to be inspected according to the present embodiment, but the present embodiment can also be applied to the inspection of a lithium ion secondary battery other than the stacked lithium ion secondary battery. For example, this embodiment can also be applied to the inspection of a wound lithium ion secondary battery.

1, the lithium ion secondary battery 10 has, for example, a flat rectangular shape and has a positive electrode tab 110A and a negative electrode tab 110B for extracting electric power from both sides thereof, . The power generating element 120 is surrounded by a casing 130 (for example, a laminated film) of the lithium ion secondary battery 10 and the periphery thereof is thermally fused so that the positive electrode tab 110A and the negative electrode tab 110B are drawn out.

2, the power generating element 120 of the lithium ion secondary battery 10 includes a positive electrode active material layer 210 constituting the positive electrode and a negative electrode active material layer 220 constituting the negative electrode, 230 for a plurality of stacked battery electrodes 260 formed on the respective faces of the stacked battery cells 260. Each stacked battery electrode 260 is laminated via an electrolyte layer 240 to form a power generating element 120. The adjacent positive electrode active material layer 210, the electrolyte layer 240 and the negative electrode active material layer 220 constitute one unit cell 200. Therefore, the lithium ion secondary battery 10 has a structure in which the unit cells 200 are laminated. A sealing member 250 for insulating the adjacent current collectors 230 is provided on the outer periphery of each of the opposing surfaces of the current collectors 230.

Next, each member of the lithium ion secondary battery 10 will be described.

[Electrode for laminated battery]

The electrode for a laminated battery has a current collector 230 and active material layers 210 and 220 provided on the surface thereof. More specifically, the positive electrode active material layer 210 is formed on one surface of one collector and the negative electrode active material layer 220 is formed on the other surface.

Each active material layer is made of a slurry material obtained by dispersing and stirring an active material in a solvent. The slurry material further includes other additives as required. As the solvent, for example, N-methylpyrrolidone (NMP) may be used.

The positive electrode active material layer includes a positive electrode active material. Examples of the positive electrode active material include lithium-transition metal oxides such as LiMn ₂ O ₄ and LiNiO ₂ , lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. Two or more kinds of positive electrode active materials may be used in combination. A positive electrode active material other than the above may be used.

The negative electrode active material layer contains a negative electrode active material. Examples of the negative electrode active material include a carbon material such as graphite, soft carbon, and hard carbon, a lithium-transition metal compound, a metal material, and a lithium-metal alloy material as described above. Two or more kinds of negative electrode active materials may be used in combination. A negative electrode active material other than the above may be used.

The average particle diameter of each active material contained in the active material layer of the positive electrode and the negative electrode is not particularly limited, but is preferably 0.01 to 100 占 퐉, and more preferably 1 to 50 占 퐉. However, a shape deviating from this range may be employed.

[Whole house]

The current collector 230 may be a thin film having conductivity and may be made of an aluminum foil, a stainless steel foil, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals But are not limited to these. For example, the current collector 230 may be a resin current collector.

[Electrolyte Layer]

The electrolyte constituting the electrolyte layer is not particularly limited and a polymer electrolyte such as a liquid electrolyte, a polymer gel electrolyte and a polymer solid electrolyte can be used.

[Seal member]

In the lithium ion secondary battery 10, the sealing member 250 is usually provided on the outer periphery of each of the facing surfaces of the collectors 230, that is, around each unit cell layer 200. This sealing member 250 is a member that prevents short-circuiting due to contact between the adjacent current collectors 230 in the battery and slight inconsistency of the ends of the unit cell layer 200 in the power generation element 120 And to prevent it. By providing the seal member 250, reliability and safety for a long period of time can be ensured, and a lithium ion secondary battery 10 of high quality can be provided.

As the material of the sealing member 250, a material having insulation property, sealing property against dropout of the solid electrolyte, sealing property (sealing property) against moisture permeation from the outside, and heat resistance under battery operating temperature is used. For example, a urethane resin, an epoxy resin, a polyethylene resin, a polypropylene resin, a polyimide resin, and a rubber may be used. Among them, a polyethylene resin or a polypropylene resin can be suitably used from the viewpoints of corrosion resistance, chemical resistance, ease of fabrication (film formability), economy and the like.

[Positive electrode tab and negative electrode tab]

(Positive electrode tab 110A and negative electrode tab 110B) electrically connected to the current collector 230 having the maximum electric potential and the minimum electric potential in the battery element 120 for the purpose of taking out electric power to the outside of the battery So as to be drawn out to the outside of the casing (130) of the battery.

A high-conductive material is used for the material constituting the tab. As the high-conductive material, for example, it is preferable to use metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof. Further, it is more preferable to use aluminum or copper from the viewpoints of light weight, corrosion resistance, and high electrical conductivity.

[Exterior]

As the exterior material 130, a bag-shaped case using a laminate film containing aluminum may be used. As the laminate film, for example, a laminate film of a three-layer structure formed by laminating polypropylene, aluminum and nylon in this order can be used.

3 is a flowchart showing a method of inspecting a lithium ion secondary battery according to the present embodiment.

Hereinafter, the testing method of the lithium ion secondary battery according to the present embodiment will be described by specifying the step numbers in Fig.

The lithium ion secondary battery 10 is manufactured (S301), and the initial charging of the lithium ion secondary battery 10 is performed (S302). The initial charging is usually carried out until the SOC (State Of Charge) reaches 100%, and is usually performed in the inspection of a conventional lithium ion secondary battery. Also, the initial charge may be a charge whose SOC is less than 100%.

After initial charging, the lithium ion secondary battery 10 is aged (S303). Aging is performed by leaving the lithium ion secondary battery 10 in place. Aging is performed as a preparation for dissolving and inspecting foreign substances such as metals incorporated into the lithium ion secondary battery 10 at the time of manufacturing the lithium ion secondary battery 10. By aging and leaving the lithium ion secondary battery, the moving state of lithium ions moving in the electric field liquid can be stabilized. This makes it possible to further reduce the deviation of the battery voltage and to improve the accuracy of determination of the battery. In addition, by removing the foreign substances in the lithium ion secondary battery 10, the deviation of the voltage of the lithium ion secondary battery 10 can be further reduced, and the accuracy of determining whether the battery is good can be improved.

After the aging, an initial discharge which is the first discharge of the lithium ion secondary battery 10 is performed (S304). The initial discharge is a charge performed until the SOC becomes 0%, and is usually performed in the inspection of a conventional lithium ion secondary battery. The initial discharge may not be a discharge until the SOC becomes 0%, or may be a discharge until the SOC becomes 50%, for example.

After the initial discharge is performed, the second charge is further charged (S305).

The reason for performing the additional charging is that the negative electrode can be activated mainly by the reaction of the lattice by insertion of lithium ions into the lattice of the negative electrode material in the negative electrode at the time of the additional charging, so that the lithium ion can be electrically stabilized.

The following formula is a chemical formula showing the reaction in the negative electrode by lithium ion insertion. In the following equation, the reaction of the negative electrode in charging and the reaction of the negative electrode in discharging are also shown.

In addition, by performing additional charging with the additional discharging described later, it is possible to distribute the in-plane distribution (hereinafter simply referred to as " in-plane distribution ") between the positive electrode tab 110A and the negative electrode tab 110B of the lithium ion secondary battery 10 ) It is possible to reduce the in-plane distribution deviation of lithium ions by moving lithium ions.

The additional charging is preferably performed until the SOC reaches 100% (full charge). By performing the additional charging until the SOC reaches 100%, the negative electrode can be sufficiently activated to become electrically stable. However, even if the SOC is further charged up to less than 100%, the negative electrode can be activated to be electrically stable. For example, additional charging may be performed until the SOC reaches 50%.

After additional charging is performed, additional discharge, which is the second discharge, is performed (S306). The additional discharge is preferably performed until the SOC becomes 0%.

The reason why the additional discharge is performed is that the positive electrode can be activated mainly by the reaction of the lattice due to the diffusion of lithium ions into the lattice of the positive electrode material in the positive electrode at the time of the additional discharge to make it electrically stable.

The following formula is a chemical formula showing the reaction in the positive electrode by lithium ion diffusion. In the following equation, the reaction of the positive electrode in discharging and the reaction of the positive electrode in charging are also shown.

In addition, by performing the above-described additional charging and additional discharging, it is possible to reduce the in-plane distribution deviation of lithium ions by moving the in-plane distributed lithium ions. This is because, by performing the additional charging and the additional discharging, it is possible to reduce the in-plane distribution deviation of the lithium ion due to the delay of the lithium ion whose movement is delayed by being located at a position distant from the tabs 110A and 110B.

Further, by performing the additional discharging until the SOC reaches 0%, the positive electrode can be activated sufficiently to be electrically stable. However, it is possible to activate the positive electrode and make it electrically stable, without performing additional discharging until the SOC reaches 0%. For example, additional discharging may be performed until the SOC reaches 20%.

As described above, the lithium ion secondary battery 10 is subjected to the additional charging and the additional discharging, and the exchange of lithium ions is experienced in each electrode to activate both electrodes. As a result, it is possible to smoothly exchange lithium ions in both electrodes, so that the electrode voltage can be stabilized and the variation of the battery voltage can be reduced.

Further, by carrying out the additional charging and the additional discharging, it is possible to reduce the in-plane distribution deviation of the lithium ions by moving the lithium ions distributed in the plane. By reducing the in-plane distribution deviation of the lithium ions, it is possible to reduce the deviation of the battery voltage.

Further, additional charging and additional discharging can be performed plural times. By performing the additional charging and the additional discharging a plurality of times, it is possible to further activate both electrodes of the lithium ion secondary battery to further reduce the in-plane distribution deviation of the lithium ion, thereby further reducing the variation in the battery voltage.

After the additional discharge is performed, a predetermined amount of the lithium ion secondary battery 10 is charged (S307). The charging of the predetermined amount in this way is for generating an initial voltage to be described later by charging and measuring the amount of fluctuation of the initial voltage with time.

Charging of a predetermined amount of the lithium ion secondary battery 10 can be performed by, for example, charging with an SOC of 20%. The charging amount in step S307 can be set to an appropriate value in consideration of the measurement accuracy of the measuring device for measuring the battery voltage and the time required for charging, for example.

The voltage of the lithium ion secondary battery 10 when charged in step S307 is measured as an initial voltage (S308). The initial voltage can be, for example, the voltage of the lithium ion secondary battery 10 at the time of leaving for 24 hours after being charged in a predetermined amount in step S307. The initial voltage may be the voltage of the lithium ion secondary battery 10 immediately after charging in step S307.

After the initial voltage is measured, the lithium ion secondary battery 10 is left for a predetermined time (S309). The reason why the lithium ion secondary battery 10 is allowed to remain for a predetermined time in this way is to generate a voltage fluctuation due to a micro short-circuit to a measurable extent when a minute short-circuit is generated in the lithium ion secondary battery 10 to be.

The predetermined time for leaving the lithium ion secondary battery 10 in step S309 may be, for example, 96 hours (four days). The predetermined time for leaving the lithium ion secondary battery 10 in step S309 can be set to a suitable time in consideration of the measurement accuracy of the measuring device for measuring the battery voltage and the inspection process time.

The voltage of the lithium ion secondary battery 10 left for a predetermined time in step S309 is measured as a transition voltage (S310).

The difference between the initial voltage of the lithium ion secondary battery 10 measured in step S308 and the transition voltage of the lithium ion secondary battery 10 measured in step S310 is calculated as a voltage variation amount (S311).

Selection of the lithium ion secondary battery 10 is performed by determining whether the lithium ion secondary battery 10 is a good or defective product based on the voltage fluctuation amount calculated in step S311 (S312). The selection is made such that if the voltage fluctuation amount of the lithium ion secondary battery 10 is a value within the width of the screening specification, the lithium ion secondary battery 10 is a good product, and in other cases, the lithium ion secondary battery 10) as a defective product.

The lithium ion secondary battery 10 determined to be a good product is shipped (S313), and the lithium ion secondary battery 10 determined to be a defective product is discarded (S314).

(Example)

An embodiment of the present embodiment will be described.

The voltage variation? V of the lithium ion secondary battery 10 was measured, and the deviation was compared between the embodiment of the present embodiment and the conventional example. In this example and the comparative example, the variation of the voltage variation? V was obtained by using the same type of lithium ion secondary battery cell by the following conditions and methods.

[Conditions and Methods]

The conditions of the present embodiment and the conventional example are as follows.

1. Both the present embodiment and the conventional example set the SOC to 100% by the initial charging.

2. In both of the present embodiment and the conventional example, aging was performed after the initial charging.

3. SOC was set to 0% by the initial discharge in both the present embodiment and the conventional example.

4. In the present embodiment, the SOC was set to 100% by additional charging.

5. In the present embodiment, the SOC was set to 0% by the additional discharge.

6. In both the present embodiment and the conventional example, after the charge / discharge, charging was performed until the SOC became 5%.

7. After the battery was charged until the SOC reached 5%, the battery voltage at the time of leaving for 1 hour was measured as the initial voltage.

8. After the initial voltage measurement, the ambient temperature was 20 to 30 ° C, and the battery voltage at the elapsed time of 4 days was measured as the transition voltage.

9. The difference between the measured initial voltage and the transition voltage was calculated as the voltage variation? V.

[result]

Fig. 4 is a diagram showing the voltage fluctuation amount of the lithium ion secondary battery when the inspecting method of the lithium ion secondary battery according to the present embodiment is performed, in comparison with the conventional example. Fig. 4A shows a voltage variation amount measured by a conventional lithium ion secondary cell inspection method, and FIG. 4B shows a voltage variation amount measured by an inspection method of a lithium ion secondary battery according to the present embodiment .

4A and 4B show the relationship between the number of cells of the lithium ion secondary battery 10 and the voltage variation amount DELTA V, respectively.

According to FIG. 4A, in the conventional example of the inspection method of the lithium ion secondary battery, the variation? Of the voltage variation? V of the lithium ion secondary battery 10 is 2.413 mV. On the other hand, according to FIG. 4B, in the embodiment of the inspection method of the lithium ion secondary battery according to the present embodiment, the variation? Of the voltage variation? V of the lithium ion secondary battery 10 is 0.8287 mV. Here, the deviation? Of the voltage variation? V represents a standard deviation of the voltage variation? V.

According to this embodiment, it has been verified that the variation? Of the voltage variation? V is reduced by the inspection method of the lithium ion secondary battery according to the present embodiment.

Step S304 corresponds to the initial discharging step of the present invention, step S305 corresponds to the additional charging step, step S306 corresponds to the additional discharging step, and steps S308, S310, and S311 correspond to the voltage measuring step . Step S308 corresponds to the initial voltage measurement step, steps S309 and S310 correspond to the transition voltage measurement step, and step S312 corresponds to the selection step.

The inspection method of the lithium ion secondary battery according to the present embodiment exerts the following effects.

By performing additional charging and discharging after the initial discharge of the battery after the production, the activation of both electrodes by the exchange of lithium ions in each electrode and the reduction of the in-plane distribution deviation of the lithium ions are realized and the initial voltage of the battery, Thereby reducing the variation of the voltage fluctuation amount. As a result, it is possible to improve the accuracy of determining whether the battery is positive or negative, and shorten the battery leaving time required for the voltage fluctuation amount measurement.

Furthermore, by performing the additional charging and the additional discharging a plurality of times, it is possible to sufficiently activate both electrodes of the lithium ion secondary battery to further reduce the in-plane distribution deviation of lithium ions. As a result, it is possible to further improve the accuracy of determining whether the battery is positive or negative, and to further shorten the battery leaving time required for the voltage fluctuation amount measurement.

Furthermore, after the initial charging, the lithium ion secondary battery is allowed to stand to perform aging, thereby stabilizing the moving state of lithium ions moving the electric field liquid, thereby further reducing the voltage deviation of the battery, It is possible to further improve the accuracy of determination of both sides.

Further, the additional charging is performed until the lithium ion secondary battery is fully charged, so that the negative electrode can be sufficiently activated to be electrically stable. Thereby, the deviation of the voltage of the battery can be further reduced, and the accuracy of determination of the battery can be further improved.

Also, by performing sorting on the basis of the difference between the initial voltage measured by charging a predetermined amount after the additional discharge and the transition voltage measured after the predetermined period of time, the measurement accuracy and the process time of the voltage measuring instrument can be optimized Therefore, it is possible to further improve the determination accuracy of the positive and negative sides of the battery and further shorten the inspection time.

(Second Embodiment)

A method of inspecting a lithium ion secondary battery according to a second embodiment of the present invention will be described.

In this embodiment, the lithium ion secondary battery is left for a predetermined time after the initial discharge, before the additional charge, and after the additional charge and before the additional discharge. Regarding the points other than the above, the present embodiment is the same as the first embodiment, and thus duplicated description is omitted.

5 is a flowchart showing a method of inspecting a lithium ion secondary battery according to the present embodiment.

In the present embodiment, after the initial discharge (S504), the lithium ion secondary battery 10 is left for a predetermined time before the additional charging (S506) (S505). The predetermined time for leaving the lithium ion secondary battery 10 may be, for example, one hour. However, it is possible to set a suitable time in consideration of the deviation of the initial voltage and the voltage fluctuation amount and the inspection process time.

After the additional charge (S506), the lithium ion secondary battery 10 is left for a predetermined time before the additional discharge (S508) (S507). The predetermined time for leaving the lithium ion secondary battery 10 may be, for example, one hour. However, it is possible to set a suitable time in consideration of the deviation of the initial voltage and the voltage fluctuation amount and the inspection process time.

It is also possible to perform only one of the step of leaving the lithium ion secondary battery 10 in step S505 and the step of leaving the lithium ion secondary battery 10 in step S507.

According to the present embodiment, the lithium ion secondary battery is left in at least one of the initial discharges, before the additional charging, after the additional charging, and before the additional discharging to stabilize the moving state of the lithium ions moving the electric field liquid . This makes it possible to further reduce the deviation of the battery voltage and to improve the accuracy of determination of the battery.

(Third Embodiment)

A method of inspecting a lithium ion secondary battery according to a third embodiment of the present invention will be described.

In the present embodiment, the initial discharge and the additional discharge are performed by CCCV (Constant Current Constant Voltage) discharge. With respect to the points other than the above, the present embodiment is the same as the first embodiment, and duplicated descriptions are omitted or simplified.

CCCV discharge refers to a discharge method in which discharging is performed by a constant current at the beginning of discharge and the voltage of the battery is kept constant after the voltage of the lithium ion secondary battery is lowered to a predetermined value.

6 is a flowchart showing a method of inspecting a lithium ion secondary battery according to the present embodiment.

In the present embodiment, the initial discharge by the CCCV discharge is performed on the lithium ion secondary battery 10 to which the initial charging (S602) and the aging (S603) by leaving in the thermostatic chamber have been performed (S604).

The initial discharge by the CCCV discharge can be performed until the SOC becomes 0 to 50%. The initial discharge is performed at a time point when the voltage of the lithium ion secondary battery 10 reaches an arbitrary value between 105% and 120% with respect to the discharge cadence target voltage To CV discharge (discharge by constant voltage). For example, when the target end voltage is 2.5 V, the CC discharge is performed until the voltage of the lithium ion secondary battery 10 reaches 2.625 V to 3.0 V, and thereafter, the CV discharge is performed, Discharge is performed. Here, the termination target voltage is the voltage of the target battery at the time when the discharge is finished.

The time for performing the CV discharge can be set arbitrarily, and can be set to any one of 0.1 hour to 3 hours, for example.

In the present embodiment, the discharge of the lithium ion secondary battery is performed by the CCCV discharge. Therefore, since the CV discharge in the CCCV discharge becomes the constant voltage discharge, it is possible to discharge uniformly as a single cell.

After the initial discharge by the CCCV discharge is performed, the lithium ion secondary battery 10 is further charged (S605). The additional charge can be performed, for example, until the SOC becomes 50 to 100%.

After the additional charging, additional discharging by the CCCV discharge is performed on the lithium ion secondary battery 10 (S606).

The additional discharge by the CCCV discharge can be performed until the SOC becomes 0 to 20%. When the voltage of the lithium ion secondary battery 10 reaches an arbitrary value between 105% and 120% with respect to the discharge cadence target voltage, the additional discharging by the CCCV discharge is performed at the CV Discharge. For example, when the target end voltage is 2.5 V, the CC discharge is performed until the voltage of the lithium ion secondary battery 10 reaches 2.625 V to 3.0 V, and thereafter, the CV discharge is performed. Discharge is performed.

The time for performing the CV discharge can be set arbitrarily, and can be set to any one of 0.1 hour to 3 hours, for example.

After the additional discharge by the CCCV discharge is performed, a predetermined amount of the lithium ion secondary battery 10 is charged (S607). The predetermined amount of charging can be, for example, a charging with an SOC of 0.1 to 20%.

The voltage of the lithium ion secondary battery 10 after a predetermined amount of charging is measured as an initial voltage (S608).

After the initial voltage is measured, the lithium ion secondary battery 10 is left for a predetermined time (S609). The ambient temperature at the time of leaving the lithium ion secondary battery 10 may be, for example, 20 to 30 占 폚.

The voltage of the lithium ion secondary battery 10 after being left for a predetermined time is measured as a transition voltage (S610), and the difference between the voltage and the initial voltage measured in step S608 is calculated as a voltage variation (S611).

The lithium ion secondary battery 10 is sorted based on the calculated voltage variation amount (S612), and the shipment (S613) or the disposal (S614) of the lithium ion secondary battery 10 is performed.

According to the present embodiment, since the discharge of the lithium ion secondary battery is performed by the CCCV discharge, the constant voltage discharge is caused by the CCCV discharge, so that the uniform cell can be discharged. Thereby, the deviation of the battery voltage can be further reduced, and the accuracy of determining the battery can be improved.

(Fourth Embodiment)

A method of inspecting a lithium ion secondary battery according to a fourth embodiment of the present invention will be described.

In this embodiment, in the initial discharge and the additional discharge, a resting time for temporarily suspending the discharge is provided, and a discharge after the interruption of the discharge is performed by discharging at a low rate. With respect to the points other than the above, the present embodiment is the same as the first embodiment, and duplicated descriptions are omitted or simplified.

7 is a flowchart showing a method of inspecting a lithium ion secondary battery according to the present embodiment.

In the present embodiment, a first initial discharge is performed on the lithium ion secondary battery 10 to which the initial charging (S702) and the aging (S703) by leaving in the thermostatic chamber have been performed (S704).

In this embodiment, in the initial discharge, a resting time for temporarily suspending the discharge is provided, and an initial discharge after the interruption of the discharge is performed by discharging at a low rate. The first initial discharge is a discharge before the discharge is stopped in the initial discharge.

In the first initial discharge, the discharge by the discharge rate (first discharge rate) of 0.3 to 1.0C can be performed until the SOC becomes 0.1 to 50%.

After the first initial discharge, the discharge is temporarily stopped (S705). The time for stopping the discharge can be, for example, 1 to 24 hours.

After the discharge is temporarily stopped, a second initial discharge is performed (S706). In the second initial discharge, it is preferable to perform discharge at a low rate (second discharge rate) of 0.05 to 0.2C until the SOC becomes 0 to 10%. The second initial discharge is a low rate discharge after the discharge is stopped in the initial discharge.

After the second initial discharge, additional charging is performed on the lithium ion secondary battery 10 (S707). The additional charge can be performed, for example, until the SOC becomes 50 to 100%.

After the additional charge, the first additional discharge is performed on the lithium ion secondary battery 10 (S708).

In the present embodiment, in the additional discharge, a resting time for temporarily suspending the discharge is provided, and additional discharging after the discharge is stopped by discharging at a low rate. The first additional discharge is a discharge before the discharge is stopped in the additional discharge.

The first additional discharge is performed until the SOC reaches 0.1 to 20% by discharge at a discharge rate (third discharge rate) of 0.3 to 1.0C.

After the first additional discharge, the discharge is temporarily stopped (S709). The time for stopping the discharge can be, for example, 1 to 24 hours.

After the discharge is temporarily stopped, a second additional discharge is performed (S710). In the second additional discharge, it is preferable to perform discharge at a low rate (fourth discharge rate) of 0.05 to 0.2C until the SOC becomes 0 to 10%. The second additional discharge is a low rate discharge after the discharge is stopped in the additional discharge.

After the second additional discharge is performed, a predetermined amount of the lithium ion secondary battery 10 is charged (S711). The predetermined amount of charging can be, for example, a charging with an SOC of 0.1 to 20%.

The voltage of the lithium ion secondary battery 10 after a predetermined amount of charging is measured as an initial voltage (S712).

After the initial voltage is measured, the lithium ion secondary battery 10 is left for a predetermined time (S713). The ambient temperature at the time of leaving the lithium ion secondary battery 10 may be, for example, 20 to 30 占 폚.

The voltage of the lithium ion secondary battery 10 after being left for a predetermined time is measured as a transition voltage (S714), and the difference between the voltage and the initial voltage measured in step S712 is calculated as a voltage variation (S715).

The lithium ion secondary battery 10 is sorted based on the calculated voltage variation amount in step S716 and the shipment S717 or the disposal step S718 of the lithium ion secondary battery 10 is performed.

Step S704 in this embodiment corresponds to the first initial discharge step of the present invention, step S705 corresponds to the initial discharge stopping step, and step S706 corresponds to the second initial discharge step, respectively. In addition, step S708 corresponds to the first additional discharge step of the present invention, step S709 corresponds to the additional discharge stop step, and step S710 corresponds to the second additional discharge step, respectively.

According to the present embodiment, in the initial discharge and the additional discharge, a resting time for temporarily suspending the discharge is provided, and a discharge after the interruption of the discharge is performed by discharging at a low rate. Thereby, it is possible to stabilize the moving state of the lithium ions moving the electric field liquid. This makes it possible to further reduce the deviation of the battery voltage and to improve the accuracy of determination of the battery.

The testing method of the lithium ion secondary battery according to the embodiment of the present invention has been described above, but the present invention is not limited to these embodiments.

For example, in the above-described embodiment, the initial voltage and the transient voltage are measured, and the cells are sorted based on the amount of fluctuation of the voltage. However, depending on the failure mode to be detected, . Further, screening of the battery based on only the initial voltage may be performed before sorting the cells based on the voltage fluctuation amount.

Further, in the embodiment, the additional charging and the additional discharging are performed after the aging, but they may be performed before the aging.

In addition, in the embodiment, a predetermined amount of charge is performed after the additional discharge. In the additional discharge, for example, discharge is performed until the SOC becomes 20% to 5%, and the battery voltage after the additional discharge is measured You can. In this case, a predetermined amount of charging performed after the additional discharge can be omitted.

In the fourth embodiment, the discharge rate of the second initial discharge should be lower than the discharge rate of the first initial discharge, and is not limited to the numerical range exemplified in the embodiment. Likewise, the discharge rate of the second additional discharge has to be lower than the discharge rate of the first additional discharge, and is not limited to the numerical range exemplified in the embodiment.

10: Lithium ion secondary battery
110A: positive electrode tab
110B: negative electrode tab
120: Power generation factor
130: exterior material
200: Single cell
210: positive electrode active material layer
220: Negative electrode active material layer
230: The whole house
240: electrolyte layer
250: seal member

Claims (7)

An initial discharge step of initially discharging after the production of the lithium ion secondary battery,
An additional charging step of charging the lithium ion secondary battery discharged in the initial discharging step;
An additional discharging step of discharging the charged lithium ion secondary battery in the additional charging step,
And a voltage measuring step of measuring a voltage of the lithium ion secondary battery after the additional discharging step. The method of inspecting a lithium ion secondary battery according to claim 1, wherein the additional charging step and the additional discharging step are performed a plurality of times. The method for inspecting a lithium ion secondary battery according to claim 1 or 2, wherein aging is performed by leaving the lithium ion secondary battery before the initial discharging step. The method for inspecting a lithium ion secondary battery according to claim 1 or 2, wherein the additional charging step is performed until the lithium ion secondary battery is fully charged. 3. The method according to claim 1 or 2, wherein the lithium ion secondary battery is left before the additional charging step after the initial discharging step, and after at least one of the additional charging step and before the additional discharging step Wherein the lithium ion secondary battery is inspected. The method according to claim 1 or 2, wherein the voltage measuring step comprises: an initial voltage measuring step of measuring an initial voltage, which is a voltage of the lithium ion secondary battery after a predetermined amount is charged in the lithium ion secondary battery; And a transition voltage measuring step of measuring a transition voltage which is a voltage of the lithium ion secondary battery when the lithium ion secondary battery is left for a predetermined time after measuring the initial voltage in the initial voltage measurement step,
Further comprising a selection step of selecting the lithium ion secondary battery based on a difference between an initial voltage measured in the initial voltage measurement step and a transition voltage measured in the transition voltage measurement step, Inspection method of battery. An initial discharge step of initially discharging after the production of the lithium ion secondary battery,
An additional charging step of charging the lithium ion secondary battery discharged in the initial discharging step;
An additional discharging step of discharging the charged lithium ion secondary battery in the additional charging step,
And a voltage measuring step of measuring a voltage of the lithium ion secondary battery after the additional discharging step,
The initial discharge step may include a first initial discharge step of discharging the lithium ion secondary battery at a first discharge rate and an initial discharge stop step of stopping the discharge of the lithium ion secondary battery after the first initial discharge step And a second initial discharging step of discharging the lithium ion secondary battery at a second discharging rate lower than the first discharging rate after the initial discharging stop step,
Wherein the additional discharging step includes a first additional discharging step of discharging the lithium ion secondary battery to a third discharging rate and an additional discharging suspending step of suspending the discharging of the lithium ion secondary battery after the first additional discharging step And a second additional discharging step of discharging the lithium ion secondary battery at a fourth discharging rate lower than the third discharging rate after the additional discharging stopping step.

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