JP2022030983A - Secondary battery quality determination method, and secondary battery manufacturing method - Google Patents

Abstract

To provide a secondary battery quality determination method capable of determining the quality of a secondary battery in a relatively short period of time.SOLUTION: A secondary battery quality determination method includes a correction information acquisition step for preliminarily measuring a correlation given to a sub reaction current value by a plurality of manufacturing conditions in the process of manufacturing a lithium iron secondary battery to record it as correction information, a manufacturing information acquisition step for acquiring the manufacturing conditions as manufacturing information, a reference voltage measuring step for measuring reference voltage at full charge by initial charge to be reference, an aging step, an actual descent voltage measuring step, a prediction descent voltage calculation step based on the acquired manufacturing information, and a quality determination step for determining the quality of the manufactured secondary battery in the case that difference between an actual descent voltage and a prediction descent voltage is a determination threshold or below.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for determining the quality of a secondary battery and a method for manufacturing a secondary battery. Specifically, the present invention relates to a method for determining the quality of a secondary battery and a method for determining the quality of the secondary battery more accurately based on manufacturing information. Regarding the method of manufacturing a battery.

Generally, a secondary battery such as a lithium ion secondary battery for a vehicle is repeatedly charged and discharged with a large current electric current and is used under severe conditions. Therefore, for example, a large self-discharge due to a minute short circuit is sufficient. Cannot demonstrate good performance. Therefore, it is desirable to discover such a secondary battery at the time of its manufacture and stop shipping.

Therefore, the quality determination method for the secondary battery disclosed in Patent Document 1 includes the following steps for determining the quality. First, it includes a charging step of charging the secondary battery, a pre-leaving voltage measuring step of measuring the opening voltage of the secondary battery after charging, and a leaving step of leaving the charged secondary battery under predetermined conditions. Next, the amount of voltage drop from the voltage measured in the pre-leaving voltage measuring step to the voltage measured in the post-leaving voltage measuring step is measured in the post-leaving voltage measuring step of measuring the opening voltage of the secondary battery after leaving. do. Then, it includes a determination step of determining that the product is defective when the voltage drop amount is larger than a predetermined value, and determining that the product is non-defective when the voltage drop amount is other than that.

According to such a quality determination method, a secondary battery that cannot exhibit sufficient performance can be found at the time of manufacture and the shipment can be stopped.

JP-A-2010-153275A

However, in the invention described in Patent Document 1, in order to significantly determine the quality, it is necessary to leave the battery for several days or more in the leaving step, so that there is a problem that the production efficiency of the secondary battery is lowered. there were.

In order to solve the above problems, the present invention provides a method for determining the quality of a secondary battery and a method for manufacturing the secondary battery, which can determine the quality of the secondary battery in a relatively short time.

In order to solve the above problems, in the method for determining the quality of a secondary battery of the present invention, each manufacturing condition and a plurality of manufacturing conditions in the manufacturing process of the secondary battery, which affect the side reaction current value of the secondary battery, are used. The step of acquiring correction information in which the correlation between the manufacturing conditions and the side reaction current value is measured in advance and recorded as correction information, and the manufacturing information acquisition in which the manufacturing conditions are acquired as manufacturing information in the secondary battery manufacturing process. Aging under the conditions of a step, a reference voltage measurement step of charging the manufactured secondary battery and measuring the reference voltage at the time of full charge by the charging as a reference, and a predetermined storage temperature and storage time. From the step of calculating the measured falling voltage and the step of calculating the measured falling voltage, which is the voltage difference from the measured voltage, while acquiring the measured voltage of the secondary battery after the step of aging and the step of the aging. With reference to the correction information based on the manufacturing information acquired in the manufacturing information acquisition step, the step of calculating the predicted falling voltage for calculating the predicted falling voltage after the aging step, and the actually measured falling voltage and the predicted falling voltage. It is characterized by comprising a step of quality determination for determining a manufactured secondary battery as a non-defective product when the difference is equal to or less than the determination threshold.

In the above invention, in the step of calculating the predicted falling voltage, the step of storing the lithium ion secondary battery under specific conditions and the amount of decrease in the full capacity of the stored lithium ion secondary battery before and after storage are determined. From the steps of measuring the capacity reduction amount to be measured, the self-discharge capacity measurement step of measuring the self-discharge capacity of the stored lithium ion secondary battery before and after storage, and the capacity reduction amount and the self-discharge capacity, at the time of storage. The self-discharge characteristic acquisition step may be provided including the step of obtaining the side reaction current values of the positive electrode and the negative electrode under the specific conditions of.

Further, in the present invention, in the step of calculating the predicted falling voltage, the storage temperature and the storage time in the aging step are referred to based on the side reaction current values of the positive electrode and the negative electrode acquired in the step of acquiring the self-discharge characteristic. Then, the integrated positive and negative electrode side reactions are referred to based on the manufacturing information acquired in the step of correcting the integrated positive and negative electrode side reaction current values and the manufacturing information acquisition step. Based on the step of correcting the current value and the corrected integrated side reaction current values of the positive and negative electrodes, the positive electrode has a positive electrode / negative electrode capacity-open potential relationship with reference to the positive and negative electrode capacity deviations. And the predicted falling voltage may be calculated from the step of obtaining the open potential of the negative electrode and the obtained open potential of the positive electrode and the negative electrode.

It is also preferable that the production conditions include any of the active material, the water content, and the temperature.
Further, it is desirable that the charging in the step of measuring the reference voltage is the initial charging performed after the assembly step of the secondary battery is completed.

The secondary battery can be preferably carried out in a lithium ion secondary battery.
It can be carried out as a method for manufacturing a secondary battery including the method for determining the quality of the secondary battery according to any one of the above.

According to the method for determining the quality of a secondary battery and the method for manufacturing a secondary battery of the present invention, the quality of a secondary battery can be determined in a relatively short time.

The schematic diagram which shows an example of the structure of a lithium ion secondary battery. The flowchart which shows the procedure of the manufacturing method of the lithium ion secondary battery of this embodiment. Flowchart for forecasting side reaction current values. The block diagram which shows the structure of the apparatus for the self-discharge characteristic acquisition of a lithium ion secondary battery. The flowchart which shows the procedure of self-discharge characteristic acquisition. An example of a correction map of manufacturing information regarding the specific surface area of an active material. An example of a correction map of manufacturing information regarding the mass of an active material. An example of a correction map for manufacturing information regarding moisture. An example of a correction map for manufacturing information regarding temperature. The graph which shows the capacity-OCP characteristic of the positive electrode and the negative electrode of the estimation method of the predicted down voltage _ΔVEST .

With reference to FIGS. 1 to 10, the method for determining the quality of the secondary battery and the method for manufacturing the secondary battery of the present invention will be described by exemplifying one embodiment of the method for manufacturing a lithium ion secondary battery.
<Outline of Embodiment>
The manufacturing method of the lithium ion secondary battery 1 provided with the quality determination method of the present embodiment affects the side reaction current of the secondary battery such as the electrode configuration, the dry state, and the temperature condition in the manufacturing of the secondary battery. Manufacturing condition PC is collected and stored as manufacturing information PI. This manufacturing information PI may be referred to as traceability information as information that can be traced and searched after manufacturing. On the other hand, a correction map MP (see FIGS. 6 to 9) in which the correlation between the manufacturing condition PC and the side reaction current is preliminarily related by an experiment is provided. The reference voltage _V0 is measured in the initial charge in the activation process of the lithium-ion secondary battery for which the assembly process has been completed, and the measured downward voltage ΔV _LER is measured after the aging process under the conditions of a constant storage temperature T and storage time AT thereafter. It is actually measured. On the other hand, if the aging process is performed under the conditions of the same temperature T and time AT with reference to the measured reference voltage V ₀ as a reference and the correction map MP based on the manufacturing information PI, how much voltage drop will occur. The predicted voltage drop ΔV _EST is calculated by accurately predicting the voltage. If it is determined in the pass / fail determination step that the difference between the measured downlink voltage ΔV _REL and the predicted downlink voltage ΔV _EST is equal to or less than the determination threshold value ΔV _THR , the manufactured secondary battery is determined to be a non-defective product, and the difference is determined. If exceeds the determination threshold value ΔV _THR , it is determined as a defective product. In this way, by obtaining an accurate predicted falling voltage ΔV _EST and comparing it with the actually measured falling voltage ΔV _REC , the initial charging process and the aging process conventionally performed in the manufacturing process of the lithium ion secondary battery In, the quality of the lithium ion secondary battery 1 can be determined. Therefore, it is not necessary to separately perform a quality determination that takes a long time such as several days, and the manufacturing process of the lithium ion secondary battery can be simplified.

<Lithium-ion secondary battery 1>
FIG. 1 is a schematic diagram showing an example of the structure of the lithium ion secondary battery 1 of the present embodiment. The lithium ion secondary battery 1 includes an electrolyte (not shown) and a cell in which the positive electrode 3, the negative electrode 4, and the separator 5 are enclosed inside the battery case 12. Then, a plurality of such cell batteries are stacked to form a battery pack, which is used as an in-vehicle power source for an electric vehicle or a hybrid vehicle.

Hereinafter, the configuration of such a lithium ion secondary battery 1 will be described. The positive electrode 3 and the negative electrode 4 are each formed in a sheet shape, and are laminated in a state of sandwiching the separator 5. By winding this laminated body, an electrode body 11 is formed in which positive and negative electrodes are alternately arranged in a state of being insulated by a separator 5 in the radial direction thereof. The electrode body 11 has a flat outer shape by pressing the wound positive electrode 3, the negative electrode 4, and the separator 5 from the outside in the radial direction. Then, the lithium ion secondary battery 1 houses such an electrode body 11 together with a non-aqueous electrolyte solution as an electrolyte, a non-aqueous electrolyte polymer, and the like in a battery case 12 constituting the outer shell of the cell battery.

The positive electrode 3 and the negative electrode 4 are formed by, for example, applying a paste containing an active material to the positive electrode current collector 13 and the negative electrode current collector 14, which have a sheet-like outer shape, and shaping and drying them, respectively. It is formed. Specifically, for example, an aluminum foil is used for the positive electrode current collector 13, and a lithium transition metal oxide is used as the positive electrode active material. Further, for example, a copper foil is used for the negative electrode current collector 14, and a carbon-based material such as graphite is used for the negative electrode active material. The battery case 12, which has been sufficiently dried and then filled with a non-aqueous electrolytic solution and sealed, is provided with a positive electrode terminal 15 and a negative electrode terminal 16 projecting to the outside thereof. The lithium ion secondary battery 1 is configured such that the positive electrode current collector 13 and the negative electrode current collector 14 corresponding to the positive electrode terminal 15 and the negative electrode terminal 16 are electrically connected to the positive electrode terminal 15 and the negative electrode terminal 16, respectively. There is.

<Self-discharge due to a minute short circuit>
Lithium-ion secondary batteries may cause a minute short circuit in which the positive electrode and the negative electrode are energized due to the precipitation of lithium metal, the mixing of fine metallic foreign substances, and the like. When a minute short circuit occurs, self-discharge increases. Therefore, after manufacturing the lithium ion secondary battery 1, it is necessary to inspect whether such self-discharge has occurred.

<Capacity shift of lithium ion secondary battery>
In the lithium ion secondary battery 1, the electrolyte is decomposed by a side reaction current to form a passive SEI film, and a capacity shift may occur due to a difference in the amount of the passive SEI film formed between the positive and negative electrodes. The thickness of the SEI coating is basically estimated by the side reaction current value [A] × the integrated value [Ah] which is a period in an arbitrary period.

<Specific surface area of active material>
The magnitude of the side reaction current varies depending on various factors other than the magnitude of the charge / discharge current. For example, if the specific surface area [cm ² / g] of the active material is large, the reaction area is large even with the mass of the same active material, and the side reaction current [A] is correspondingly large. Therefore, this specific surface area is measured by, for example, the BET method (Brunauer-Emmett-Teller method). Then, the specific surface area [cm ² / g] of this active material is recorded as the production information PI _BET .

<Mass of active substance>
Further, the larger the basis weight [g / cm ² ] indicating the amount of the paste applied to the electrode, the larger the mass of the active material, and the larger the side reaction current [A]. This basis weight [g / cm ² ] is also recorded as a manufacturing condition.

Similarly, the larger the electrode area [cm ² ], that is, the area of the mixture layer at the electrode, the larger the amount of active material, and the larger the side reaction current [A]. This electrode area [cm ² ] is also recorded as a manufacturing condition.

Then, the magnitude of the ratio of the grain [g / cm ² ] × the electrode area [cm ² ] × the active material in the paste is recorded as the manufacturing information PI _ACT regarding the total mass [g] of the active material in the electrode.

<Residual water>
Further, the non-aqueous electrolyte is indispensable for the lithium ion secondary battery 1, and it is desirable that the water content is completely removed. If residual water is present, the water reacts on the positive and negative electrodes, forming a film and increasing the side reaction current value. Therefore, in the production of the positive and negative electrodes in the source step (S2) in which the battery element is manufactured, a paste containing an active material is applied to the current collector, and hot air drying, heating drying in a drying furnace, and then vacuum drying are performed. Moisture is removed through such steps, and the amount of water remaining in the electrode body at this time is recorded as a manufacturing condition.

Further, in the assembly step (S3), the drying step (S4) is performed after the electrode body wound together with the separator is housed in the battery case 12. The state of water removal in this drying step (S4) affects the magnitude of the subsequent side reaction current of the lithium ion secondary battery 1. Therefore, the drying conditions such as the heating temperature and time of this drying step are determined. Recorded as a manufacturing condition.

In addition, the dew point temperature as a working environment is recorded. Here, the "dew point" generally refers to the dew point temperature, which is the temperature at which dew condensation, that is, condensation occurs, when the gas is cooled. In the case of natural drying, the dew point affects the degree of drying, so it is recorded as a manufacturing condition. When an air dryer for pneumatic equipment is used, it refers to data that is also used as an index showing its performance. With an air dryer, the one with a lower rated dew point temperature can produce drier air, so this is recorded as a manufacturing condition as a drying condition. In the case of heat drying in a vacuum drying oven, the temperature and degree of vacuum of the drying oven are recorded as manufacturing conditions.

In the present embodiment, the manufacturing conditions such as the water content in the electrode, the drying condition, and the dew point are integrated and recorded as the manufacturing information _PIAQA regarding the water content.
<Temperature>
The manufacturing process of the lithium ion secondary battery 1 is affected by the process environment temperature [° C]. At the start of the initial charge of the aging step in the activation step immediately after the completion of the assembly step, the SEI film on the positive and negative electrodes is not formed. The SEI film is formed on the positive and negative electrodes by the initial charge of the lithium ion secondary battery 1. After that, when the temperature rises, the main reaction current and the side reaction current increase as the temperature rises, and the SEI film film is formed. As a result, the side reaction current value [A] decreases rapidly. Such a process environment temperature [° C] and a temperature [° C] during aging are recorded as manufacturing conditions and recorded as manufacturing information PI _TEP regarding the temperature.

<Other manufacturing information>
In the present embodiment, the above three elements are exemplified as manufacturing information, but of course, the present invention is not limited to these. That is, any element that can be quantified that contributes to the prediction of the side reaction current value can be grasped as manufacturing conditions and manufacturing information.

<Correction information>
As described above, when the manufacturing conditions are different, the magnitude of the side reaction current value also changes depending on the manufacturing conditions. The magnitude of the side reaction current affects the subsequent deterioration of the lithium ion secondary battery 1. Therefore, in order to predict the measured downward voltage ΔV _REL after the aging process under certain conditions from the reference voltage V ₀ immediately after the initial charge, which manufacturing condition is the magnitude of the side reaction current value [A]? You need to know if it will affect you.

Therefore, a map of the correlation between the manufacturing information and the side reaction current value is created in advance. Using this map as the "correction map MP", the magnitude of the side reaction current value [A] of the lithium ion secondary battery 1 during the aging process is predicted, and based on this, the side reaction current value [A] after the completion of the aging process is predicted. ] To calculate the integrated value [Ah]. Then, based on the integrated value [Ah] of this side reaction current value [A], the predicted downward voltage _ΔVEST after the completion of the aging step is calculated.

<Correction regarding the specific surface area of active materials>
FIG. 6 shows an example of a correction map MP _BET for manufacturing information regarding the specific surface area of an active material. The size of the specific surface area [cm ² / g] is recorded as the manufacturing information PI _BET . The specific surface area [cm ² / g] of the active material obtained here and the specific surface area [cm ² / g] of the active material, which is the design value of the lithium ion secondary battery 1, are plotted as reference values, and further, the specific surface area is plotted. A correction map was created by plotting the relationship with the side reaction current value [A] when [cm ² / g] increased or decreased by experiment. For example, when the specific surface area has a small error, this may be treated as a fixed value.

Therefore, the coefficient of how much the side reaction current value [A] increases or decreases is determined by the manufacturing information PI _BET of the specific surface area [cm ² / g] of the active material at the time of manufacturing the lithium ion secondary battery 1. Can be done. That is, by multiplying the design side reaction current value [A] by this coefficient, the corrected side reaction current value can be predicted. For example, when the side reaction current value in the manufacturing information PI _BET regarding the specific surface area of the active material is A ₁ [A], divide it by the reference value side reaction current value A ₀ [A], and then use A ₁ / A ₀ . , Find the correction factor. Then, the expected value is derived by multiplying the reference side reaction current value by this correction coefficient.

<Correction regarding the mass of active material>
FIG. 7 shows an example of a correction map MP _ACT for manufacturing information regarding the mass of the active material. The magnitude of the mass [g] is recorded as manufacturing information PI _ACT . The mass [g] of the active material obtained here and the mass [g] of the active material, which is the design value of the lithium ion secondary battery 1, are plotted as reference values, and the subordinate when the mass [g] further increases or decreases. A correction map was created by plotting the relationship with the reaction current value [A] experimentally. In the present embodiment, the mass [g] is calculated by the ratio of the grain [g / cm ² ] × the electrode area [cm ² ] × the active material in the paste, but any one of these three errors. If there are few, this may be treated as a fixed value.

Therefore, it is possible to determine the coefficient of how much the side reaction current value [A] increases or decreases from the manufacturing information PI _ACT of the mass [g] of the active material at the time of manufacturing the lithium ion secondary battery 1. That is, by multiplying the design side reaction current value [A] by this coefficient, the corrected side reaction current value can be predicted. For example, when the side reaction current value in the manufacturing information PI _ACT regarding the mass of the active material is A ₁ [A], divide it by the reference value side reaction current value A ₀ [A], and use A ₁ / A ₀ . Find the correction factor. Then, the expected value is derived by multiplying the reference side reaction current value by this correction coefficient.

<Correction regarding water content>
FIG. 8 shows an example of a correction map of manufacturing information regarding the water content. In the manufacturing process of the lithium ion secondary battery 1, manufacturing conditions such as the water content in the electrode, drying conditions, and dew point are stored, and these are integrated and recorded as manufacturing information PI _AQA regarding the remaining water content. A correction map was created by plotting the relationship between the water content obtained here, the water content which is the design value of the lithium ion secondary battery 1, and the side reaction current value [A] when this increased or decreased. ..

Therefore, the correction coefficient for how much the side reaction current value [A] increases or decreases can be determined from the production information of the water content [g] at the time of manufacturing the lithium ion secondary battery 1. That is, by multiplying the design side reaction current value [A] by this correction coefficient, the corrected side reaction current value can be predicted. In this embodiment, by multiplying the correction coefficient for the active material and the correction coefficient for the water content, it is possible to calculate the predicted value of the side reaction current value that incorporates both the active material and the water content.

<Temperature correction>
FIG. 9 shows an example of a correction map of the manufacturing information PI _TEP regarding the temperature. The manufacturing process of the lithium ion secondary battery 1 is affected by the process environment temperature [° C]. In particular, at the start of the initial charging of the aging step in the activation step, the SEI film is not formed on the positive and negative electrodes. After the formation of the SEI coating on the positive and negative electrodes, as the temperature rises, the formation of the SEI coating progresses rapidly according to Arrhenius's law, and as a result, the side reaction current value [A] decreases quickly. Such a process environment temperature [° C] and a temperature [° C] during aging are recorded as manufacturing conditions and recorded as manufacturing information PI _TEP regarding the temperature. For example, the aging temperature [° C] obtained here, the aging temperature [° C] based on the design value of the lithium ion secondary battery 1, and the side reaction current value [A] when the temperature increases or decreases. The relationships were plotted experimentally to create a correction map.

Therefore, the correction coefficient for how much the side reaction current value [A] increases or decreases can be determined from the manufacturing information of the aging temperature [° C] at the time of manufacturing the lithium ion secondary battery 1. That is, by multiplying the design side reaction current value [A] by this correction coefficient, the corrected side reaction current value can be predicted. Similar to the correction coefficient for the active material and the correction coefficient for the water content, this correction coefficient can be superimposed and reflected in the prediction of the side reaction current value by multiplying it.

(Action of Embodiment)
<Manufacturing method of lithium ion secondary battery 1>
Here, a method for manufacturing the lithium ion secondary battery 1 of the present embodiment will be described. FIG. 2 is a flowchart showing the procedure of the manufacturing method of the lithium ion secondary battery 1.

<Delivery of materials (S1)>
We will deliver the necessary materials for the manufacture of the lithium-ion secondary battery 1 (S1). As the material of the positive electrode 3, the negative electrode 4, the separator 5, and the electrolytic solution constituting the electrode body 11, various conventionally known materials can be used. As an example of these materials, lithium cobalt oxide or lithium manganate is used as the active material of the positive electrode 3. Aluminum foil is used for the positive electrode current collector 13. Carbon (graphite) is used as the active material of the negative electrode 4. A copper foil is used for the negative electrode current collector 14. In addition, raw materials such as conductive materials and binders for pastes that form a mixture of electrodes are also delivered. A polyolefin sheet is used for the separator 5. The electrolytic solution contains an organic solvent, lithium ions, and an additive. A metal case 12 for the battery will also be delivered. In addition, terminals etc. will be delivered.

Upon delivery of this material, the characteristics of the raw material are inspected. For example, the physical properties of carbon (graphite), which is the active material of the negative electrode 4, are inspected. For example, the specific surface area is measured by the BET method (Brunauer-Emmett-Teller method). Further, the specific surface area of the active material of the positive electrode 3 is similarly measured by the BET method. The specific surface area [cm ² / g] of these active materials is recorded as manufacturing information PI _BET .

<Source process (S2)>
The source process is a process of manufacturing a positive electrode 3 and a negative electrode 4 which are elements of a lithium ion secondary battery.

For example, in the positive electrode 3, a conductive material, a binder, or the like is first added to the positive electrode active material and kneaded to form a paste. Next, the paste is applied to a predetermined range on the aluminum foil sheet to be the positive electrode current collector 13. The paste is made to have a uniform thickness with a doctor blade or the like, and is applied to a design basis weight [g / cm ² ]. Then, it is dried, pressed to have a uniform thickness, and then cut to a predetermined size. In this case, the range to which the paste is applied and the basis weight may be uneven, and the applied area and the thickness of the mixture layer may vary with respect to the design value. Therefore, in manufacturing the positive electrode 3, the basis weight [g / cm ² ] and the electrode area [cm ² ] are measured and stored as manufacturing conditions.

These are manufactured information PI regarding the total mass [g] of the active material in the positive electrode 3 by multiplying the size of the grain [g / cm ² ] × the electrode area [cm ² ] × the ratio of the active material in the paste. Recorded as _ACT .

In the production of the positive electrode 3 and the negative electrode 4 in the source process, the positive electrode current collector 13 and the negative electrode current collector 14 are coated with a paste containing an active material, dried by heating with hot air, and then vacuum dried. Moisture is removed through such steps, but water still remains in the electrode body. Then, the remaining water content [g] is recorded as the manufacturing information PI _AQA .

Further, although not performed in this embodiment, the thickness [mm] of the separator 5, the concentration and resistance of the electrolytic solution, and the like may be measured as the manufacturing information PI.
<Assembly process (S3)>
The assembly step (S3) is a step of assembling the battery element of the lithium ion secondary battery 1 manufactured in the source step (S2) as a cell battery.

A sheet-shaped positive electrode 3, a negative electrode 4, and a separator 5 are laminated and wound on the case 12 to form an electrode body 11. The molded electrode body 11 is shaped and inserted into the case 12. The positive electrode current collector 13 of the positive electrode 3 is electrically connected to the positive electrode terminal 15 outside the case. Similarly, the negative electrode current collector 14 of the negative electrode 4 is electrically connected to the negative electrode terminal 16 outside the case 12.

<Drying step (S4)>
The lithium ion secondary battery 1 whose accommodation of the electrode body 11 is completed in the assembly step (S3) is subjected to a drying step (S4) of removing the water remaining in the case 12 before filling the electrolytic solution. Basically, it is a dry room with dew point control, and dry air is circulated by an air dryer with a low rated dew point temperature. As the drying conditions, the rated dew point temperature of the air dryer used, the drying time, and the like are recorded as the manufacturing information PI _AQA .

<Electrolyte filling (S5)>
After the drying step (S4), the inside of the dried battery is filled with the electrolytic solution (S5).
<Sealing (S6)>
After the drying step (S4) is completed, the battery case 12 filled with the electrolytic solution (S5) is covered and welded.

This completes the physical assembly of the lithium ion secondary battery 1.
<First charge (S7)>
From here on, a procedure called conditioning of the lithium ion secondary battery 1 is performed, and its main purpose is to suppress decomposition of the electrolytic solution by forming an SEI film on the surface of the negative electrode 4. Therefore, after assembling the lithium ion secondary battery 1, the activation step by the initial charge (S7) is always performed.

<Measurement of reference voltage V ₀ (S8)>
The battery cell is fully charged by the initial charge (S7) until the SOC (State Of Charge) of the battery cell reaches 100%, and the cell voltage at that time is measured as the reference voltage _V0 . Since this reference voltage V ₀ is the first charge, it is the cell voltage in a state where there is almost no deterioration in the battery.

<Aging step (S9)>
The lithium ion secondary battery 1 fully charged in the initial charge (S7) is subjected to an aging step (S9) in which the lithium ion secondary battery 1 is stored at a constant temperature, for example, 70 ° C. for a certain period of time, for example, one day. During this time, an SEI film is formed. That is, as the lithium ion secondary battery 1, a side reaction current is generated, and even a slight deterioration progresses.

<Cooling (S10)>
After the aging step (S9) is completed, the battery is cooled and returned to room temperature so as not to expose the battery to a high temperature state more than necessary.

<Measurement voltage V _1REL measurement (S11)>
In the cooled lithium ion secondary battery 1, the measured voltage V _1REL , which is the cell voltage, is actually measured (S11). The measured voltage V _{1 REL} is lower than the reference voltage V ₀ due to the aging step (S9) for reasons such as self-discharge. This voltage drop is basically caused by the fact that when a side reaction current is generated, power is consumed according to the current value.

Therefore, for example, if the specific surface area of the active material of the inspected lithium ion secondary battery 1 is large, the side reaction current increases by that amount and the voltage decrease becomes large.
For example, if a minute metal or the like is mixed in the battery, the positive electrode 3 and the negative electrode 4 may be short-circuited by penetrating the separator 5. If the degree of short circuit is large, a large self-discharge may occur during this aging process, and the voltage may drop sharply. When the voltage drops sharply in this way, the procedure is not described in the flowchart because it is not directly related to the present invention, but it is clearly excluded as a defective product. In addition, the impedance is measured after aging, and cell batteries with extremely high impedance are also excluded as defective products.

<Measured down voltage ΔV _REL calculation (S12)>
Reference voltage V ₀ Measured voltage V 1 _REL measured by the procedure of measurement voltage V _{1 REL} measurement (S11) subtracted from the reference voltage V ₀ at the time of initial charge measured in the procedure of measurement (S8) _. Is calculated.

<Manufacturing information acquisition (S15)>
When the aging step (S9) is completed, the predicted voltage V _1EST is predicted in parallel with the measurement of the measured voltage value (S11) (S17). Prior to the prediction (S17) of the voltage V _1EST , the manufacturing information PI is acquired as the data on which the prediction is based (S15). In the present embodiment, the manufacturing information PI stores information on the active material, residual moisture, and temperature.

<Predicting side reaction current value (S16)>
Following the procedure of manufacturing information acquisition (S15), the side reaction current value is predicted (S16). FIG. 3 is a flowchart showing a procedure for predicting a side reaction current value (S16). The procedure for predicting the side reaction current value (S16) will be described according to this flowchart.

<Acquisition of self-discharge characteristics (S161)>
First, the self-discharge characteristic is first acquired (S161). The "self-discharge characteristic" is a basic characteristic of the lithium ion secondary battery 1 to be judged as good or bad. In other words, it is for deriving the side reaction current value [A] generated in each of the positive electrode and the negative electrode, that is, the rate of deterioration peculiar to the lithium ion secondary battery 1 under predetermined storage conditions. Even if it is unique, it is data that can be used in common in the same production lot. By correcting the self-discharge characteristics obtained here with reference to the manufacturing information PI, the side reaction current value of the target lithium ion secondary battery 1 is predicted.

<Configuration of device 200 for acquiring self-discharge characteristics of lithium ion secondary battery>
FIG. 4 is a block diagram showing the configuration of the device 200 for acquiring the self-discharge characteristic of the lithium ion secondary battery 1. The configuration of the device 200 for acquiring the self-discharge characteristic of the lithium ion secondary battery 1 of the present embodiment includes a well-known charge / discharge device 203, a cell voltage measuring device 204, a cell current measuring device 205, a thermometer 206, and a heat retaining device 207. .. Further, a control device 208 including a well-known computer provided with an interface for controlling these is provided. The control device 208 includes a CPU 281 and a memory 282. The memory 282 includes a RAM and a ROM.

These function as a storage means for storing the lithium ion secondary battery 1 under specific conditions as a configuration of a device for acquiring the self-discharge characteristic of the lithium ion secondary battery 1. It also functions as a battery capacity reduction measuring means for measuring the capacity reduction amount Q _loss of the battery full capacity before and after storage of the stored lithium ion secondary battery 1. It also functions as a self-discharge amount measuring means for measuring the self-discharge capacity _QSD of the stored lithium ion secondary battery 1 before and after storage. In addition, the self-discharge capacity of the positive electrode and the self-discharge capacity of the negative electrode are calculated by using the measured capacity decrease Q _loss and self-discharge capacity _QSD , and the relationship between the pre-acquired side reaction rate and the usage environment. It functions as a discharge amount calculation means.

<Flow chart of self-discharge characteristic acquisition>
FIG. 5 is a flowchart showing the procedure for acquiring the self-discharge characteristic. The procedure for acquiring the self-discharge characteristic will be described with reference to this flowchart.

Here, first, prior to the explanation of this flowchart, the terms used in the explanation will be described in advance.
“T1 [° C]” is an arbitrary storage temperature (for example, 50 ° C).

“T1 [h]” is an arbitrary storage period (for example, 24 hours).
"V _dat 1 [V]" is derived from the voltage VB in which the cell voltage VB is completely discharged (in this embodiment, the cell voltage VB in the fully discharged state of the cell SOC 0% is referred to as "lower limit voltage"). This implementation is performed at a voltage (for example, 3.8 [V]) arbitrarily set between 4.1 [V] of full charge (cell SOC 0 to 100%, referred to as "upper limit voltage" in this embodiment). In the form, it is called "reference voltage". In this embodiment, it is used as a reference voltage for measuring the self-discharge capacity and is also an arbitrary initial cell voltage VB for storage.

"Q1 [Ah]" is a battery in which the cell voltage VB is changed from the lower limit voltage 3.0 [V] to the upper limit voltage (fully charged cell voltage VB = 4.1 [V] (here, the voltage of the cell SOC 100%)). It is the full capacity of the pre-storing battery whose capacity has been measured.

It is the section capacity before storage measured from the lower limit voltage 3.0 [V] of "Q2 [Ah]" at the reference voltage V _dat = 3.8 [V].
“Q3 [Ah]” is the residual capacity after storage in which the reference voltage V _dat = 3.8 [V] is discharged to the lower limit voltage of 3.0 [V] after storage.

"Q4 [Ah]" is the full capacity of the battery after storage measured from the lower limit voltage of 3.0 [V] to the upper limit voltage of 4.1 [V].
“ _QSD [Ah]” is the self-discharge capacity during the storage period obtained from the difference between the section capacity Q2 before storage and the remaining capacity Q3 after storage.

"Q _loss [Ah]" is a capacity decrease amount obtained from the difference between the battery full capacity before storage Q1 and the battery full capacity after storage.
“I _NE0 [A]” is a negative electrode side reaction current (velocity) determined by the self-discharge capacity _QSD [Ah] ÷ storage time t1 [h].

“I _PE0 [A]” is a positive electrode side reaction current obtained from the difference between the negative electrode side reaction current (velocity) _iNE0 and the quotient of the volume reduction amount Q _loss [Ah] ÷ storage time t1 [h]. Speed).

In this embodiment, it is defined as described above.
<Procedure of flowchart for self-discharge characteristic acquisition>
Next, using these definitions, the procedure for acquiring the self-discharge characteristic of the lithium ion secondary battery 1 will be described with reference to the flowchart of FIG.

First, when the process of acquiring the self-discharge characteristic is started (START), the battery is charged from the lower limit voltage 3.0 [V] of the cell SOC 0% at the time of complete discharge to the full charge of the upper limit voltage 4.1 [V] of the cell SOC 100%. The battery full capacity Q1 [Ah] before storage is measured (S101).

Next, the section capacity Q2 [Ah] before storage is measured by charging in the voltage section from the lower limit voltage 3.0 [V] to the reference voltage V _dat = 3.8 [V] (S102).
Subsequently, after adjusting the voltage to the reference voltage V _dat = 3.8 [V], it is stored at an arbitrary temperature T1 (for example, 50 ° C.) for an arbitrary time t1 (for example, 24 hours) (S104). This procedure corresponds to the "save step".

After adjusting the voltage to the reference voltage V _dat = 3.8 [V] before storage, the battery is discharged to the lower limit voltage of 3.0 [V] after storage, and the remaining capacity Q3 [Ah] after storage is measured ( S105). Subsequently, the battery is fully charged from the lower limit voltage of 3.0 [V] to the upper limit voltage of 4.1 [V], and the battery full capacity Q4 [Ah] after storage is measured (S106). In this case, it is specified by the voltage. This is because after storage, the full charge capacity is lower than before storage due to deterioration of the active material / electrolyte, formation of a film, and the like.

Then, the difference between the section capacity Q2 [Ah] before storage and the remaining capacity Q3 [Ah] after storage is obtained. Compared to the section capacity Q2 before storage, the remaining capacity Q3 after storage has a decrease in capacity due to self-discharge. The remaining capacity when the capacity charged from the lower limit voltage 3.0 [V] to the reference voltage V _dat = 3.8 [V] is discharged to the lower limit voltage 3.0 [V] after storage is obtained. From this, the self-discharge amount of the storage time t1 can be obtained. By this procedure, the self-discharge capacity _QSD is calculated from the electric capacity reduced to the storage time t1 (S107). This procedure corresponds to the "step of self-discharge amount measurement".

Next, the self-discharge capacity _QSD [Ah] is divided by the storage time t1 [h], and the side reaction current value (film formation current) of the negative electrode corresponding to the growth rate of the film, that is, the deterioration rate is i _NE0 [A]. Is calculated (S108).

Further, the capacity decrease amount Q _loss [Ah] is calculated from the difference between the battery full capacity Q1 [Ah] before storage and the battery full capacity Q4 [Ah] after storage (S109).
Finally, from the difference between the negative electrode side reaction current value i _NE0 [A] and the quotient [A] obtained by dividing the capacity reduction amount Q _loss by the storage time t1 [h], the positive electrode side reaction current value i _PE0 [A]. ] Is calculated (S110).

As described above, the procedure for acquiring the self-discharge characteristics for measuring the side reaction current value i _NE0 [A] of the negative electrode of the lithium ion secondary battery and the side reaction current value i _PE0 [A] of the positive electrode in the predetermined storage section of the present embodiment. Ends (END).

By such a procedure, the adverse reaction current value i _PE0 [A] of the positive electrode and the negative electrode under the conditions of the reference voltage V _dat [V] for starting storage, the storage temperature T1 [° C], and the storage time t1 [h]. The side reaction current value i _NE0 [A] can be measured. That is, the self-discharge characteristic of this lithium ion secondary battery 1 is revealed. That is, the "self-discharge characteristic" is data that serves as a reference for determining deterioration from the cell voltage VB and the cell temperature TB. This procedure may be performed for each cell, but if the lithium ion secondary battery 1 has the same configuration, sampling inspection is sufficient without 100% inspection.

The above is the procedure for acquiring the self-discharge characteristics of the lithium ion secondary battery 1.
The self-discharge characteristics obtained in this way include the specific surface area [cm ² / g] of the design active material of the lithium ion secondary battery 1 to be determined, the active material mass [g], the residual moisture [g], and the like. , It is the original data corrected by the correction information of the temperature [° C].

<Acquisition of aging conditions (S162)>
The storage time [h], storage temperature [° C], etc. of the aging process are read, and from the relationship with the storage time [h] and storage temperature [° C] in the self-discharge characteristics, the side reaction current value of the self-discharge characteristics [° C] A] is corrected.

<Reading manufacturing information (S163)>
Subsequently, the manufacturing information acquired in the procedure of manufacturing information acquisition (S15) is read (S162). In the present embodiment, the manufacturing information PI stores the manufacturing information PI _BET regarding the specific surface area of the active material, the manufacturing information PI _ACT regarding the mass of the active material, the manufacturing information PI _AQA regarding the residual moisture, and the manufacturing information PI _TEP regarding the temperature. ..

<Reading correction information (S164)>
Subsequently, the correction information CI is read (S163). Here, FIG. 6 is a diagram conceptually showing a correction map MP _BET regarding the specific surface area of the active material. FIG. 7 is a diagram conceptually showing a correction map MP _ACT regarding the mass of the active material. FIG. 8 is a diagram conceptually showing a correction map _MPAQA regarding the amount of water. FIG. 9 is a diagram conceptually showing a correction map MP _TEP regarding temperature.

In the present embodiment, the manufacturing information PI has acquired the manufacturing information PI _BET regarding the specific surface area of the active material, the manufacturing information PI _ACT regarding the mass of the active material, the manufacturing information PI _AQA regarding the water content, and the manufacturing information PI _TEP regarding the temperature. .. Then, the correction map MP _BET regarding the specific surface area of the active material, the correction map MP _ACT regarding the mass of the active material, the correction map MP _AQA regarding the water content, and the correction map MP _TEP regarding the temperature corresponding to these are read.

<Vaccine side reaction current value prediction (S165)>
The side reaction current value corrected by the storage time AT [h] and the storage temperature T [° C] in the aging step acquired in the aging condition acquisition (S162) is corrected based on the manufacturing information PI.

Here, the side reaction current value is corrected based on the manufacturing information PI. Here, the manufacturing information PI _BET regarding the specific surface area of the active material and the correction map MP _BET regarding the specific surface area of the active material shown in FIG. 6 will be described as typical examples.

The size of the specific surface area [cm ² / g] is recorded as the manufacturing information PI _BET . The specific surface area [cm ² / g] of the active material obtained here, the specific surface area [cm ² / g] of the active material which is the design value of the lithium ion secondary battery 1, and the side reaction current when this increases or decreases. A correction map was created by plotting the relationship with the value [A] experimentally. Here, there is a correlation that the side reaction current value [A] increases according to the specific surface area [cm ² / g]. The side reaction current value [A] at the reference value [cm ² / g] of the design specific surface area of the lithium ion secondary battery 1 to be determined is A0. On the other hand, according to the manufacturing information PI _BET regarding the active material read in the procedure of reading the manufacturing information (S163), it can be seen from this correction map MP _BET that the side reaction current is A1.

Therefore, if A0 / A1 = 1.5, the side reaction current value will be the value multiplied by the correction coefficient 1.5. Here, the difference is made extremely large as an easy-to-understand example, but it can be corrected accurately by obtaining the correction coefficient.

<About positive and negative electrodes>
In the above description, the positive electrode and the negative electrode are described without distinction, but in the procedure of self-discharge characteristic acquisition (S161), the side reaction current value i _PE0 [A] of the positive electrode and the side reaction current value i of the negative electrode _NE0 [A] can be calculated individually. In addition, a correction map MP _ACT for active materials, a correction map MP _AQA for water content, and a correction map MP _TEP for temperature are also created by distinguishing the positive electrode and the negative electrode, respectively. Therefore, based on these data, in the procedure of the side reaction current value prediction (S165), the side reaction current value corrected based on the aging conditions and the manufacturing information PI can be accurately calculated for each of the positive electrode and the negative electrode.

<Predicted expected voltage V _1EST (S17)>
Here, the process returns to the flowchart of FIG. 2 to continue the description. For each of the positive and negative electrodes calculated in the procedure of predicting the side reaction current value (S16), the expected voltage _V1EST is predicted based on the side reaction current value corrected based on the aging conditions and the manufacturing information PI (S17). do.

<Relationship between positive and negative electrode capacities after film formation-OCP>
FIG. 10 shows the capacity of the positive electrode and the negative electrode after the film formation after the aging step for calculating the expected voltage V _1EST based on the side reaction current value calculated in the procedure of predicting the side reaction current value (S16). It is a graph which shows the relationship of an OCP (Open Circuit Potential).

The SEI film is formed by the aging step (S9). In other words, it can be said that the film formation has progressed by the aging step (S9) for the lithium ion secondary battery. The progress of the SEI film formation can be represented by the integrated side reaction current value.

In the lithium ion secondary battery 1, lithium ions move from the positive electrode to the negative electrode by charging. This movement of lithium ions lowers the open potential OCP [V] of the negative electrode. In the graph shown in FIG. 9, the negative electrode OCP moves to the right on the curve _UNE . When discharged, lithium ions move from the negative electrode to the positive electrode. This movement of lithium ions raises the open potential OCP [V] of the negative electrode. Speaking of the graph, it moves to the left on the curve _UNE of the negative electrode OCP.

When the positive / negative electrode capacity shift occurs in the lithium ion secondary battery 1, the full charge capacity [Ah] decreases from _Q0NE to _Q1NE . The decrease in the capacity Q at this time is ΔQ _NE and can be calculated by the side reaction current value [A] × time [h].

Therefore, under the conditions of the reference voltage V _dat [V] for starting storage of the lithium ion secondary battery 1 acquired in the procedure of self-discharge characteristic acquisition (S161), the storage temperature T1 [° C], and the storage time t1 [h]. The side reaction current value i _NE0 [A] of the negative electrode of the above can be used. Then, as shown in the procedure of the side reaction current value prediction (S165), the side reaction current value _iNE0 [A] of the negative electrode is stored at the storage temperature T [° C] and the storage time AT [h] in the aging step (S9). Correct with. Further, _ΔQNE can be calculated by referring to the correction map MP by the manufacturing information PI.

Similarly for the positive electrode, in the lithium ion secondary battery 1, lithium ions move from the positive electrode to the negative electrode by charging. This movement of lithium ions raises the open potential OCP [V] of the positive electrode. In the graph shown in FIG. 9, it moves to the right on the curve _UPE of the positive electrode OCP. When discharged, lithium ions move from the positive electrode to the negative electrode. This movement of lithium ions lowers the open potential OCP [V] of the positive electrode. In the graph, it moves to the left on the curve _UPE of the positive electrode OCP.

In the lithium ion secondary battery 1, when the capacity shift occurs due to the formation of a film on the positive and negative electrodes, the full charge capacity [Ah] decreases from Q _0PE to Q _{1 PE} . The decrease in the capacity Q at this time can be calculated by ΔQ _PE by the side reaction current value [A] × time [h].

Therefore, under the conditions of the reference voltage V _dat [V] for starting storage of the lithium ion secondary battery 1 acquired in the procedure of self-discharge characteristic acquisition (S161), the storage temperature T1 [° C], and the storage time t1 [h]. The side reaction current value i _PE0 [A] of the positive electrode of the above can be used. Then, as shown in the procedure of the side reaction current value prediction (S165), the side reaction current value i _PE0 [A] of the positive electrode is stored at the storage temperature T [° C] and the storage time AT [h] in the aging step (S9). Correct with. Further, the ΔQ _PE can be calculated by referring to the correction map MP by the manufacturing information PI.

As described above, the OCP of the negative electrode formed by the film formation in the aging step (S9) is the potential V _1NE in Q _1NE , and the OCP of the positive electrode is the potential V ₁ PE in Q _{1 PE} . Therefore, it can be obtained by the cell voltage V _1EST = V _1PE − V _1NE of the lithium ion secondary battery 1 that has undergone the aging step (S9).

<Predicted down voltage ΔV _EST calculation (S18)>
As described above, since the cell voltage V _1EST can be calculated in the predicted voltage V _1EST prediction (S17), the predicted falling voltage ΔV _EST is calculated by the predicted falling voltage ΔV _EST = reference voltage V ₀ -predicted voltage V _1EST . Will be done.

<ΔV _REL -ΔV _EST <ΔV _THR determination (S13)>
The predicted falling voltage ΔV _EST obtained in the procedure of the above predicted falling voltage ΔV _EST calculation (S18) is subtracted from the measured falling voltage ΔV _REL calculated in the procedure of the measured falling voltage ΔV _REL calculation (S12). Then, the result is compared with the determination threshold value ΔV _THR (S13). As a result, when (ΔV _REL − ΔV _EST <ΔV _THR ), the difference between the actually measured voltage drop and the theoretically assumed voltage drop is small, and the lithium ion secondary battery 1 Is determined to be a good product and proceeds to post-processing (S13: YES).

On the other hand, when it is not (ΔV _REL −ΔV _EST <ΔV _THR ), that is, when (ΔV _REL −ΔV _EST ≧ ΔV _THR ), the actually measured voltage drop and the theoretically assumed voltage The difference from the decrease is large, and it is judged to be defective. Then, it is determined that the lithium ion secondary battery 1 is a defective product, and the process is terminated as it cannot be shipped (S13: NO).

This completes the manufacturing method of the lithium ion secondary battery 1 of the present embodiment shown in the flowchart of FIG. 2 (end).
<Effect of embodiment>
(1) Since the quality judgment is made using the manufacturing information PI, the quality can be accurately judged even in the lithium ion secondary battery 1 under different manufacturing conditions.

(2) In the lithium ion secondary battery 1, since it is possible to determine the quality of the lithium ion secondary battery 1 in the initial charge of activation, which is an essential step, a storage step for inspection that takes a separate time, etc. The production efficiency of the lithium ion secondary battery 1 can be improved.

(3) By the procedure (S161) for acquiring the self-discharge characteristic, the unique self-discharge characteristic of the lithium ion secondary battery 1 to be judged as good or bad can be reflected, and the accuracy adapted to the lithium ion secondary battery 1 can be reflected. Judgment is possible.

(4) The predicted down voltage ΔV _EST can be calculated accurately by accurately estimating the side reaction current value. Therefore, even a slight self-discharge due to a minute short circuit can be discriminated even under different manufacturing conditions, and a defective product can be accurately discriminated.

(5) In particular, since the side reaction current value is calculated separately for the positive electrode and the negative electrode, it is possible to make a more accurate judgment of quality.
(Variation Example) The present invention is not limited to each of the above embodiments, and can be carried out as follows.

〇 In this embodiment, the predicted voltage V _1EST is predicted after the aging step (S9) (before the cooling step (S10)) (S17), but the manufacturing information is acquired after the cooling step (S10). , Prediction of predicted voltage V _1EST (S17), calculation of predicted down voltage ΔV _EST (S18) may be performed. Thereby, the influence of the cooling step (S10) can be taken into consideration, and the actual measured downward voltage ΔV _REL can be compared more accurately.

-In the present embodiment, the cell battery of the lithium ion secondary battery 1 for a vehicle formed in a plate shape has been described as an example, but the shape is not limited to the cylindrical shape or the like. Further, the secondary battery is not limited to the lithium ion secondary battery. Further, the present invention is not limited to the cell batteries that are stacked and mounted on the vehicle, and can be used as a single battery or as a battery fixed to a facility.

○ It goes without saying that the manufacturing conditions and manufacturing information are not limited to the examples. That is, any element that can be quantified that contributes to the prediction of the side reaction current value can be grasped as manufacturing conditions and manufacturing information.

○ In the embodiment, for example, the manufacturing information regarding the temperature is recorded as the manufacturing information regarding the temperature by integrating the process environment temperature [° C] and the temperature during aging [° C], but the process environment temperature [° C] Alternatively, the aging temperature [° C] may be treated as separate manufacturing information.

○ For example, in addition to the examples, the concentration of electrolyte, the injection amount, the resistance value and impedance of the cell battery, and the like can also be used as manufacturing conditions and manufacturing information.
○ Although the correction map MP is illustrated, it may be an approximate expression based on an inductive analysis of the measured values or a plot of the measured values. Alternatively, it may be in a format such as a tabular reference table.

○ Although the capacity-OCP graph was used for explanation, such a concrete graph is not essential for the implementation of the invention.
○ Furthermore, a map may be generated by machine learning or deep running. Furthermore, a correction map integrated by machine learning or deep running may be generated from a plurality of manufacturing information.

○ The flowcharts shown in FIGS. 2, 3, and 5 are examples, and the order can be changed, and steps can be added, deleted, or changed.
○ Further, it goes without saying that the present invention can be implemented as a device by a person skilled in the art by adding, deleting or changing its configuration, or by changing the category, as long as it does not deviate from the scope of claims.

1 ... Secondary battery 3 ... Positive electrode 4 ... Negative electrode 5 ... Separator PC ... Manufacturing conditions PI ... Manufacturing information PI _BET ... Manufacturing information on the specific surface area of the active material PI _ACT ... Manufacturing information on the amount of active material PI _AQA ... Manufacturing on the water content Information PI _TEP ... Manufacturing information about temperature V ₀ ... Reference voltage T ... Storage temperature AT ... Storage time V ₁ ... Measured voltage ΔV _LER ... Measured down voltage ΔV _EST ... Predicted down voltage ΔV _THR ... Judgment threshold CI ... Correction information MP ... Correction Map MP _BET ... (Regarding the specific surface area of the active material) Correction map MP _ACT ... (Regarding the active material) Correction map MP _AQA ... (Regarding the amount of water) Correction map MP _TEP ... (Regarding the temperature) Correction map

Claims (7)

Correction information for multiple manufacturing conditions in the secondary battery manufacturing process that affect the side reaction current value of the secondary battery by measuring in advance the respective manufacturing conditions and the correlation that the manufacturing conditions give to the side reaction current value. The steps for acquiring correction information to be recorded as
In the manufacturing process of the secondary battery, the step of acquiring the manufacturing information to acquire the manufacturing conditions as the manufacturing information, and
A reference voltage measurement step of charging the manufactured secondary battery and measuring a reference voltage at the time of full charge by the charging as a reference, and a step of measuring the reference voltage.
Aging steps for aging under predetermined storage temperature and storage time conditions,
The step of calculating the measured falling voltage, which is the voltage difference from the measured voltage while acquiring the measured voltage of the secondary battery after the aging step, and the step of calculating the measured falling voltage.
A step of calculating a predicted falling voltage for calculating a predicted falling voltage after the step of aging by referring to the correction information based on the manufacturing information acquired in the step of acquiring the manufacturing information from the reference voltage, and a step of calculating the predicted falling voltage.
A method for determining the quality of a secondary battery, which comprises a step of determining the quality of a secondary battery manufactured when the difference between the actually measured voltage drop and the predicted voltage drop is equal to or less than a determination threshold value. In the step of calculating the predicted falling voltage,
The storage step of storing the lithium-ion secondary battery under specific conditions,
The step of measuring the capacity reduction amount to measure the capacity reduction amount of the battery full capacity before and after the storage of the stored lithium ion secondary battery, and
The self-discharge capacity measurement step for measuring the self-discharge capacity of the stored lithium ion secondary battery before and after storage, and
The first aspect of the present invention is characterized in that it includes a step of acquiring self-discharge characteristics including a step of obtaining a side reaction current value of a positive electrode and a negative electrode under a specific condition at the time of storage from the capacity decrease amount and the self-discharge capacity. The method for determining the quality of the secondary battery described. In the step of calculating the predicted falling voltage,
Based on the positive and negative electrode side reaction current values acquired in the self-discharge characteristic acquisition step, the integrated positive and negative electrode side reaction current values are corrected with reference to the storage temperature and storage time in the aging step. Steps to do and
A step of correcting the integrated positive electrode and negative electrode side reaction current values by referring to the correction information based on the manufacturing information acquired in the manufacturing information acquisition step.
Based on the corrected integrated positive and negative electrode side reaction current values, the step of obtaining the positive and negative electrode open potentials with reference to the positive and negative electrode capacitance deviations in the positive electrode / negative electrode capacitance-open potential relationship. When,
The quality determination method for a secondary battery according to claim 2, wherein the predicted falling voltage is calculated from the obtained open potentials of the positive electrode and the negative electrode. The method for determining the quality of a secondary battery according to any one of claims 1 to 3, wherein the production condition includes any condition of an active material, a water content, and a temperature. The quality determination of the secondary battery according to any one of claims 1 to 4, wherein the charging in the step of measuring the reference voltage is the initial charging performed after the assembly step of the secondary battery is completed. Method. The method for determining the quality of a secondary battery according to any one of claims 1 to 5, wherein the secondary battery is a lithium ion secondary battery. A method for manufacturing a secondary battery, which comprises the method for determining the quality of a secondary battery according to any one of claims 1 to 6.

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