Manufacturing method of regenerated secondary battery

Abstract

To provide a manufacturing method of a rechargeable secondary battery that can provide a rechargeable secondary battery, in which a rechargeable secondary battery manufactured by combining a plurality of used secondary batteries can be adapted to the application as a product, a warranty period, etc., and that can be charged and discharged by efficiently using the capacity of each of the plurality of used secondary batteries constituting the rechargeable secondary battery.SOLUTION: In a method of manufacturing a rechargeable secondary battery 10 by combining a plurality of used battery cells C1 to Cn, the degree of deterioration of used battery cells C1 to Cn is estimated, the used battery cells C1 to Cn are classified into a plurality of groups according to the estimated degree of deterioration, and multiple used battery cells C1 to Cn classified into the same group are combined to manufacture the plurality of groups of rechargeable secondary batteries 10.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for producing a regenerated secondary battery. [Background technology]

[0002] Various methods are known for reusing used secondary batteries (see, for example, Patent Documents 1 to 3). In the methods described in Patent Documents 1 to 3, the electrical characteristics of a used secondary battery are obtained from testing, a usage history, or the like, and whether or not the used secondary battery can be reused is determined based on the obtained electrical characteristics. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-216328 A [Patent Document 2] JP 2017-33802 A [Patent Document 3] JP 2017-134894 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when manufacturing a battery pack by reusing a plurality of used secondary batteries, the performance and quality required for the battery pack differs depending on the application of the battery pack as a product, the warranty period, etc. Furthermore, it is required to configure the battery pack so that all the battery cells can be discharged without leaving any capacity. Here, in a battery pack containing battery cells with different degrees of deterioration, the more deteriorated battery cell will be fully charged or fully discharged first during charging and discharging. In this case, even if the other battery cells have a spare capacity, charging and discharging must be stopped, and it is not possible to discharge all the capacity of the battery cells from the battery pack without leaving any capacity.

[0005] In view of the above circumstances, the present invention has an object to provide a method for manufacturing a recycled secondary battery that can adapt the recycled secondary battery manufactured by combining a plurality of used secondary batteries to the intended use and warranty period of the product, and that can provide a recycled secondary battery that can be charged and discharged by efficiently using the capacity of each of the plurality of used secondary batteries that make up the recycled secondary battery. [Means for solving the problem]

[0006] The method for producing a recycled secondary battery of the present invention is a method for producing a recycled secondary battery by combining a plurality of used secondary batteries, estimating the deterioration degree of the used secondary batteries, classifying the used secondary batteries into a plurality of groups according to the estimated deterioration degree, and combining a plurality of the used secondary batteries classified into the same group to produce a plurality of groups of the recycled secondary batteries. The deterioration degree is a ratio between a cycle deterioration degree, which is a degree of deterioration due to repeated charging and discharging of the used secondary battery, and a temperature deterioration degree, which is a degree of deterioration due to temperature. do.

[0008] Method for producing a regenerated secondary battery according to the present invention A method for manufacturing a recycled secondary battery by combining a plurality of used secondary batteries, comprising: estimating a degree of deterioration of the used secondary batteries; classifying the used secondary batteries into a plurality of groups according to the estimated degree of deterioration; and combining a plurality of the used secondary batteries classified into the same group to manufacture a plurality of groups of the recycled secondary batteries. The deterioration degree is a ratio between a cycle deterioration degree, which is a degree of deterioration due to repeated charging and discharging of the used secondary battery, and a storage deterioration degree, which is a degree of deterioration due to being left in a high-temperature environment. R . Effect of the Invention

[0009] According to the present invention, when combining a plurality of used secondary batteries to manufacture a recycled secondary battery, the used secondary batteries are classified into a plurality of groups according to their degree of deterioration, and a plurality of secondary batteries classified into the same group are combined to manufacture a plurality of groups of recycled secondary batteries. This makes it possible to provide a plurality of groups of recycled secondary batteries, each group adapted to the product's intended use, warranty period, etc., and to provide a recycled secondary battery that can be charged and discharged efficiently by using the capacity of each of the plurality of used secondary batteries. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a regenerated secondary battery produced by a method for producing a regenerated secondary battery according to one embodiment of the present invention. [Diagram 2]FIG. 2 is a diagram showing an outline of a method for producing a regenerated secondary battery according to one embodiment of the present invention. [Diagram 3] FIG. 3 is a flowchart illustrating a method for producing a regenerated secondary battery according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described below along with preferred embodiments. Note that the present invention is not limited to the embodiments shown below, and can be modified as appropriate within the scope of the present invention. In addition, in the embodiments shown below, some configurations are omitted from illustration and description, but it goes without saying that publicly known or well-known technologies are appropriately applied to the details of the omitted technologies within the scope of no contradiction with the contents described below.

[0012] 1 is a schematic diagram showing a regenerated secondary battery 10 manufactured using a method for manufacturing a regenerated secondary battery according to one embodiment of the present invention. As shown in the diagram, the regenerated secondary battery 10 is an in-vehicle or stationary power source comprising n (n is an integer of 2 or more) battery cells C1 to Cn connected in series. The battery cells C1 to Cn are, for example, secondary batteries such as lithium ion batteries or lithium ion capacitors, which are supplied with power from a charging circuit (not shown) and charged, and discharge the charged power to supply power to a load L.

[0013] The regenerated secondary battery 10 may be an in-vehicle or stationary power source having n battery modules (n is an integer of 2 or more) connected in series. In this case, each battery module has multiple battery cells connected in series.

[0014] Here, the degradation levels of the n battery cells C1 to Cn included in the regenerated secondary battery 10 are made equal according to standards described below. This prevents differences in the characteristics of the battery cells C1 to Cn from occurring during use of the regenerated secondary battery 10. Therefore, the regenerated secondary battery 10 charges and discharges all of the battery cells C1 to Cn without leaving any capacity behind over a long period of time.

[0015] FIG. 2 is a diagram showing an outline of a method for manufacturing a regenerated secondary battery 10 according to an embodiment of the present invention. As shown in this figure, in the method for manufacturing a regenerated secondary battery 10 of this embodiment, a used secondary battery 1 including a plurality of battery cells C1-Cn or a plurality of battery modules (hereinafter simply referred to as battery cells C1-Cn) is disassembled to take out a plurality of used battery cells C1-Cn. Then, a charge / discharge test is performed on each of the taken out used battery cells C1-Cn to estimate the deterioration degree of each of the used battery cells C1-Cn. Then, the used battery cells C1-Cn are classified (classified) into a plurality of groups (for example, classes 1-9 as shown in the figure) according to the estimated deterioration degree. Then, the used battery cells C1-Cn classified into the same group (class) are combined to manufacture a regenerated secondary battery 10. That is, when manufacturing a plurality of groups of regenerated secondary batteries 10, the deterioration degrees of the used battery cells C1-Cn constituting the regenerated secondary battery 10 of each group (each class) are made equal.

[0016] The deterioration degree of a battery may be defined by a known method, for example, using at least one of various parameters that define the deterioration degree of a battery, such as a cycle deterioration degree indicating the relationship between the number of repeated charge / discharge cycles and deterioration of the battery, a temperature deterioration degree indicating the relationship between the battery temperature or the environmental temperature and deterioration of the battery, a storage deterioration degree indicating the relationship between the storage time when the battery is not used and deterioration of the battery, a capacity deterioration degree (SOH: State of Health) indicating the ratio of the full charge capacity of a battery when it is not deteriorated to the full charge capacity of a battery when it is not deteriorated, and a SOC deterioration degree indicating the relationship between the charging rate SOC (State of Charge) during storage and deterioration of the battery.

[0017] In this embodiment, the degree of deterioration of a battery is defined by the ratio between the cycle deterioration degree C and the temperature deterioration degree T (hereinafter referred to as the C / T ratio). The C / T ratio can be said to be the proportion (dominant ratio) of the cycle deterioration degree C and the temperature deterioration degree T in the deterioration factors of the battery.

[0018] Here, the C / T ratio may be calculated using history information of the used secondary battery 1 during use, or may be calculated by performing a charge / discharge test on the used battery cells C1-Cn collected from the used secondary battery 1. When calculating by charging / discharging the collected used battery cells C1-Cn, a database is created in advance by experimentally determining the relationship between the characteristic values ​​(such as the capacity degradation degree SOH, temperature, C rate, frequency, impedance, and internal resistance) of the used battery cells C1-Cn and the C / T ratio, and the characteristic values ​​of the used battery cells C1-Cn obtained by the charge / discharge test are compared with the information in the database to estimate the C / T ratio. An example of a method for estimating the C / T ratio will be described below.

[0019] First, a relational expression between the internal resistance and the capacity degradation degree SOH for used battery cells C1-Cn with a predetermined C / T ratio is obtained in advance. Furthermore, a relation between the charging rate SOC and the internal resistance at a plurality of different capacity degradation degrees SOH is obtained in advance for used battery cells C1-Cn (first reference battery) with a C / T ratio of 0.9 to 1.0 and used battery cells C1-Cn (second reference battery) with a C / T ratio of 0.1 to 0.2.

[0020] Next, the internal resistance of the used battery cells C1-Cn to be estimated is measured, and the tentative capacity degradation degree SOH of the used battery cells C1-Cn to be estimated is obtained by substituting the internal resistance into the above-mentioned relational expression between the internal resistance and the capacity degradation degree SOH. Furthermore, among the multiple capacity degradation degrees SOH obtained by measuring the relationship between the charging rate SOC and the internal resistance of the first reference battery and the second reference battery, the one closest to the tentative capacity degradation degree SOH is selected.

[0021] Next, the internal resistances of the used battery cells C1 to Cn to be estimated are measured at n different types of charging rates SOC (n is an integer of 2 or more), and a first point with each internal resistance as the coordinate of each axis is plotted in an n-dimensional coordinate system. For the first reference battery at the selected capacity degradation level SOH, a second point with each axis as the coordinate of the internal resistance at the n types of charging rates is plotted in the n-dimensional space, and a third point is similarly plotted for the second reference battery. The closer the C / T ratio of the used battery cells C1 to Cn to be estimated is to the first reference battery, the smaller the distance between the first and second points, and the closer the C / T ratio of the used battery cells C1 to Cn to be estimated is to the second reference battery, the smaller the distance between the first and third points. Therefore, the C / T ratio can be estimated by calculating the ratio of the distances between each point.

[0022] Instead of the temperature degradation degree T indicating the relationship between the battery temperature or the environmental temperature and the degradation of the battery, the above-mentioned neglected degradation degree L, which is a parameter that defines the temperature degradation degree T plus the neglected time, may be used to define the degradation degree of the used battery cells C1 to Cn by the ratio of the cycle degradation degree C to the neglected degradation degree L (hereinafter referred to as the C / L ratio). Here, it is known that, for example, when cycle degradation is the dominant degradation factor, the internal resistance increases as the degradation of the battery progresses, and the internal resistance is approximately constant regardless of the state of charge SOC, whereas when neglected degradation is the dominant degradation factor, the internal resistance increases as the degradation of the battery progresses, and the internal resistance increases as the state of charge SOC increases (see, for example, JP 2016-38276 A). Based on this known relationship, the C / L ratio can be estimated.

[0023] In addition, it is known that the cycle degradation level C and the unused degradation level L have a relationship in which, for example, when cycle degradation is the dominant degradation factor, as degradation progresses, the voltage-charge rate curve at low charge rates becomes gentler, the voltage at a specified charge rate SOC decreases, and discharging becomes more difficult, whereas when unused degradation is the dominant degradation factor, as degradation progresses, the voltage-charge rate curve at low charge rates becomes steeper, the voltage at a specified charge rate increases, and discharging becomes easier (see, for example, JP 2016-45149 A). Based on this known relationship, the C / L ratio can be estimated.

[0024] In this embodiment, the degradation level (C / T ratio) of the used battery cells C1-Cn collected from the used secondary battery 1 is calculated by a degradation level analyzer 5, which is a computer, and then the collected multiple used battery cells C1-Cn are classified according to their degradation level (C / T ratio). For example, the collected multiple used battery cells C1-Cn are classified into classes such that the class changes every time the degradation level (C / T ratio) changes by 0.1, such as class 1 for used battery cells C1-Cn with a C / T ratio of 0.9 or more and less than 1.0, class 2 for used battery cells C1-Cn with a C / T ratio of 0.8 or more and less than 0.9, and class 3 for used battery cells C1-Cn with a C / T ratio of 0.7 or more and less than 0.8.

[0025] 3 is a flowchart for explaining a method for manufacturing a regenerated secondary battery 10 according to one embodiment of the present invention. As shown in this flowchart, in step 1, used secondary batteries 1 that have been used in electric vehicles, hybrid vehicles, vehicles with idling stop functions, etc. are collected. Next, in step 2, a simple evaluation such as an appearance inspection is performed on the used secondary batteries 1, and used secondary batteries 1 that are unsuitable for reuse, such as those that have dents or are at risk of causing defects in the electrodes, are removed.

[0026] Next, in step 3, the used secondary battery 1 suitable for reuse is disassembled to collect used battery cells C1-Cn. Next, in step 4, a charge / discharge test is performed on the collected used battery cells C1-Cn. In this step, a charge / discharge tester 2 (see FIG. 2) is used to charge / discharge the used battery cells C1-Cn, and the current value I and voltage value V during charging / discharging of the used battery cells C1-Cn are measured by a current sensor 3 and a voltage sensor 4 (both see FIG. 2). In the charge / discharge test in this step, for example, the combination of the charging rate SOC and the C rate is changed, and the current value I and voltage value V for each combination are measured.

[0027] Next, in step 5, the deterioration level (C / T ratio) of the battery is estimated based on the current value I and voltage value V measured in step 4. The deterioration level (C / T ratio) of the battery is estimated using a deterioration level analyzer 5. The deterioration level analyzer 5 is a computer and executes a deterioration level estimation program. For example, when the combination of the charging rate SOC and the C rate is changed as described above and the current value I and the voltage value V are measured for each combination, the deterioration level analyzer 5 calculates the internal resistance value of the used battery cells C1 to Cn based on the difference in the current value I and the difference in the voltage value V between each combination, and estimates the deterioration level (C / T ratio) of the used battery cells C1 to Cn based on the calculated internal resistance value. Note that the deterioration level analyzer 5 may estimate the deterioration level (C / T ratio) of the used battery cells C1 to Cn using cycle history information and temperature history information during use of the used secondary battery 1 in addition to or instead of the current value I and the voltage value V measured by the current sensor 3 and the voltage sensor 4.

[0028] Next, in step 6, it is determined whether the collected used battery cells C1-Cn satisfy a predetermined reuse standard. For example, it is determined whether the internal resistance and capacity deterioration level SOH of the collected used battery cells C1-Cn are within an allowable range, and whether the deterioration level (C / T ratio) of the collected used battery cells C1-Cn is a value that allows them to be used as products. Batteries that are determined to satisfy the reuse standard in step 6 are classified according to their deterioration level (C / T ratio) and stored in step 7. On the other hand, batteries that are determined not to satisfy the reuse standard in step 6 are sorted out as batteries for recycling in step 9.

[0029] In step 8 following step 7, the used battery cells C1 to Cn stored by class are combined to manufacture a regenerated secondary battery 10. Here, it becomes possible to sell, for example, a regenerated secondary battery 10 made up of a Class 1 battery with a C / T ratio of 0.9 or more and less than 1.0, and a regenerated secondary battery 10 made up of a Class 2 battery with a C / T ratio of 0.8 or more and less than 0.9, as regenerated secondary batteries 10 with different models, grades, warranty periods, etc.

[0030] As described above, in the manufacturing method of the regenerated secondary battery 10 according to this embodiment, the deterioration degree of the multiple used battery cells C1-Cn is estimated, the multiple used battery cells C1-Cn are classified into multiple groups (classes 1-9) according to the estimated deterioration degree, and the multiple used battery cells C1-Cn classified into the same group are combined to manufacture multiple groups of regenerated secondary batteries 10. This makes it possible to provide multiple groups of regenerated secondary batteries 10, each group adapted to the intended use as a product, warranty period, etc. In addition, since the difference in characteristics between the multiple used battery cells C1-Cn constituting the regenerated secondary battery 10 can be suppressed, it is possible to provide a regenerated secondary battery 10 that can be charged and discharged using the capacity of all the used battery cells C1-Cn without waste over a long period of time.

[0031] Furthermore, by manufacturing multiple groups of regenerated secondary batteries 10 according to the degree of deterioration of the used battery cells C1 to Cn, it is possible to set a capacity margin for the regenerated secondary batteries 10 in anticipation of the deterioration of the regenerated secondary batteries 10, and to set a warranty period for the deterioration of the regenerated secondary batteries 10 in anticipation of the deterioration of the regenerated secondary batteries 10.

[0032] Furthermore, it is possible to acquire the battery characteristics of the used battery cells C1 to Cn and estimate the degree of deterioration (C / T ratio, C / L ratio) of the used battery cells C1 to Cn without requiring the usage history of the secondary battery in use.

[0033] The present invention has been described above based on an embodiment, but the present invention is not limited to the above embodiment, and modifications may be made without departing from the spirit of the present invention, and known or well-known technologies may be appropriately combined. [Explanation of symbols]

[0034] 10:Recycled secondary battery C1 to Cn: Battery cells (used secondary batteries) C: Degree of cycle deterioration T: Temperature deterioration degree L: Degree of deterioration due to neglect

Claims

1. A method for manufacturing a recycled secondary battery by combining a plurality of used secondary batteries, comprising the steps of: Estimating a degree of deterioration of the used secondary battery; classifying the used secondary batteries into a plurality of groups according to the estimated deterioration degree; manufacturing a plurality of groups of the regenerated secondary batteries by combining a plurality of the used secondary batteries classified into the same group; A method for manufacturing a regenerated secondary battery, wherein the degree of deterioration is a ratio of a cycle deterioration degree, which is the degree of deterioration due to repeated charging and discharging of the used secondary battery, to a temperature deterioration degree, which is the degree of deterioration due to temperature.

2. A method for manufacturing a recycled secondary battery by combining a plurality of used secondary batteries, comprising: Estimating a degree of deterioration of the used secondary battery; classifying the used secondary batteries into a plurality of groups according to the estimated deterioration degree; manufacturing a plurality of groups of the regenerated secondary batteries by combining a plurality of the used secondary batteries classified into the same group; A method for manufacturing a regenerated secondary battery, wherein the degree of deterioration is a ratio between the cycle deterioration degree, which is the degree of deterioration due to repeated charging and discharging of the used secondary battery, and the storage deterioration degree, which is the degree of deterioration due to being left in a high-temperature environment.

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