JP7598210B2 - Manufacturing method of regenerated secondary battery - Google Patents

Description

The present invention relates to a method for producing a recycled secondary battery.

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 or usage history, and whether or not the used secondary battery can be reused is determined based on the obtained electrical characteristics.

JP 2011-216328 A JP 2017-33802 A JP 2017-134894 A

When manufacturing a battery pack by reusing multiple 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, the battery pack must be configured so that all 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 some capacity to spare, 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.

In view of the above circumstances, the present invention aims to provide a method for manufacturing a recycled secondary battery that can adapt the recycled secondary battery manufactured by combining multiple used secondary batteries to the product's intended use, warranty period, etc., and can provide a recycled secondary battery that can be charged and discharged by efficiently using the capacity of each of the multiple used secondary batteries that make up the recycled secondary battery.

The method for manufacturing a recycled secondary battery of the present invention is a method for manufacturing a recycled secondary battery by combining a plurality of used secondary batteries, estimating the 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 manufacturing a plurality of groups of the recycled secondary batteries by combining a plurality of the used secondary batteries classified into the same group , wherein the degree of deterioration is the ratio of the cycle deterioration degree, which is the degree of deterioration due to repeated charging and discharging of the used secondary batteries, to the temperature deterioration degree, which is the degree of deterioration due to temperature .

The method for manufacturing a recycled secondary battery of the present invention is a method for manufacturing a recycled secondary battery by combining a plurality of used secondary batteries, estimating the 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 manufacturing a plurality of groups of the recycled secondary batteries by combining a plurality of the used secondary batteries classified into the same group, wherein the degree of deterioration is the ratio between the cycle deterioration degree, which is the degree of deterioration due to repeated charging and discharging of the used secondary batteries, and the storage deterioration degree, which is the degree of deterioration due to being left in a high-temperature environment.

According to the present invention, when manufacturing a recycled secondary battery by combining multiple used secondary batteries, the used secondary batteries are classified into multiple groups according to their degree of deterioration, and multiple secondary batteries classified into the same group are combined to manufacture multiple groups of recycled secondary batteries. This makes it possible to provide multiple 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 multiple used secondary batteries.

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. FIG. 2 is a diagram showing an outline of a method for producing a recycled secondary battery according to one embodiment of the present invention. FIG. 3 is a flow chart for explaining a method for producing a recycled secondary battery according to one embodiment of the present invention.

The present invention will be described below in accordance with a preferred embodiment. Note that the present invention is not limited to the embodiment described below, and can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiment described below, some configurations are omitted from illustration and description, but it goes without saying that publicly known or well-known technologies are used as appropriate for the details of the omitted technologies, within the scope of not causing any inconsistencies with the contents described below.

Figure 1 is a schematic diagram of 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 this figure, the regenerated secondary battery 10 is an in-vehicle or stationary power source that includes n battery cells C1 to Cn (n is an integer of 2 or more) 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 charged by power supplied from a charging circuit (not shown), and discharge the charged power to supply power to a load L.

The recycled 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.

The degree of deterioration of the n battery cells C1 to Cn in the regenerated secondary battery 10 is made equal according to the criteria 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 capacity of the battery cells C1 to Cn over a long period of time without leaving any waste.

Figure 2 is a diagram showing an outline of a method for manufacturing a regenerated secondary battery 10 according to one embodiment of the present invention. As shown in this figure, in the method for manufacturing a regenerated secondary battery 10 according to 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 remove a plurality of used battery cells C1-Cn. Then, a charge/discharge test is performed on each of the removed plurality of used battery cells C1-Cn to estimate the degree of deterioration of each of the plurality of used battery cells C1-Cn. Then, the plurality of 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 degree of deterioration. Then, the plurality of 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 degree of deterioration of the plurality of used battery cells C1-Cn constituting the regenerated secondary battery 10 of each group (each class) is made equal.

The degree of deterioration of a battery may be specified by a known method. For example, the degree of deterioration of a battery may be specified using at least one of various parameters that specify the degree of deterioration of a battery, such as the degree of cycle deterioration that indicates the relationship between the number of repeated charge/discharge cycles and the deterioration of the battery, the degree of temperature deterioration that indicates the relationship between the battery temperature or the environmental temperature and the deterioration of the battery, the degree of storage deterioration that indicates the relationship between the time left unattended and the deterioration of the battery, the degree of capacity deterioration (SOH: State of Health) that indicates 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 the degree of SOC deterioration that indicates the relationship between the charging rate SOC (State of Charge) during storage and the deterioration of the battery.

In this embodiment, the degree of deterioration of the battery is determined by the ratio of the cycle deterioration degree C to 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.

Here, the C/T ratio may be calculated using historical information on the use of the used secondary battery 1, 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 (capacity degradation level SOH, temperature, C rate, frequency, impedance, internal resistance, etc.) 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 is described below.

First, the relationship between the internal resistance and the capacity degradation degree SOH for used battery cells C1-Cn with a predetermined C/T ratio is determined in advance. Furthermore, the relationship between the charging rate SOC and the internal resistance at multiple mutually different capacity degradation degrees SOH is determined 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.

Next, the internal resistance of the used battery cells C1 to Cn to be estimated is measured, and the tentative capacity degradation degree SOH of the used battery cells C1 to Cn to be estimated is calculated by substituting the internal resistance into the above-mentioned relational equation between the internal resistance and the capacity degradation degree SOH. Furthermore, of 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.

Next, the internal resistance of the used battery cells C1 to Cn to be estimated is measured at n different types (n is an integer of 2 or more) of charging rates SOC, 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 being the coordinate of the internal resistance at the n types of charging rates is plotted in 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 finding the ratio of the distances between each point.

In addition, 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 the 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, as an 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 an approximately constant value independent of the charging rate 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 charging rate SOC increases (see, for example, JP 2016-38276 A). Based on this known relationship, the C/L ratio can be estimated.

It is also known that the cycle degradation degree C and the unused degradation degree 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 given 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 given charge rate increases, and discharging becomes easier (see, for example, JP 2016-45149 A). The C/L ratio can be estimated based on this known relationship.

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.

Figure 3 is a flowchart for explaining a method for manufacturing a recycled 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 with dents that may cause defects in the electrodes, are excluded.

Next, in step 3, the used secondary battery 1 suitable for reuse is disassembled to collect the used battery cells C1 to Cn. Next, in step 4, a charge/discharge test is performed on the collected used battery cells C1 to Cn. In this step, the used battery cells C1 to Cn are charged and discharged using a charge/discharge tester 2 (see Figure 2), and the current value I and voltage value V during charging and discharging of the used battery cells C1 to Cn are measured by a current sensor 3 and a voltage sensor 4 (both see Figure 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.

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 that 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 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 voltage value V measured by the current sensor 3 and the voltage sensor 4.

Next, in step 6, it is determined whether the collected used battery cells C1-Cn satisfy a predetermined recycling standard. For example, it is determined whether the internal resistance and capacity degradation level SOH of the collected used battery cells C1-Cn are within an acceptable range, and whether the degradation 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 recycling standard in step 6 are classified by degradation level (C/T ratio) and stored in step 7. On the other hand, batteries that are determined not to satisfy the recycling standard in step 6 are sorted out as batteries for recycling in step 9.

In step 8 following step 7, the used battery cells C1 to Cn stored for each class are combined to manufacture a regenerated secondary battery 10. Here, for example, it becomes possible to sell a regenerated secondary battery 10 made up of Class 1 batteries with a C/T ratio of 0.9 or more and less than 1.0, and a regenerated secondary battery 10 made up of Class 2 batteries 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.

As described above, in the method for manufacturing a regenerated secondary battery 10 according to this embodiment, the deterioration level 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 level, 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. Also, since the differences in the characteristics of the multiple used battery cells C1-Cn that make up the regenerated secondary battery 10 can be suppressed, it is possible to provide a regenerated secondary battery 10 that can be charged and discharged over a long period of time by using the capacity of all the used battery cells C1-Cn without any waste.

In addition, 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.

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

The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and modifications may be made without departing from the spirit of the present invention, and publicly known or well-known technologies may be appropriately combined.

10: Regenerated secondary battery C1 to Cn: Battery cell (used secondary battery)
C: Degree of cycle deterioration T: Degree of temperature deterioration L: Degree of deterioration due to neglect

Claims (2)

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 . 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 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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