JP2011171032A - Method for recycling secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for reducing the number of useless secondary batteries when secondary batteries, which constitute a plurality of battery packs, collected from users or markets are assembled to reconstitute a new battery pack. <P>SOLUTION: Battery packs collected from the users or markets are recovered (S101) and disassembled to secondary batteries (S102); the characteristics such as full charge capacities of single cells are measured (S103); secondary batteries are classified by setting so that the tolerance of dispersion increases with decrease in full charge capacity (S104, S105); and a battery pack is reassembled with classified secondary batteries (S106). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for reusing a secondary battery, and more particularly, to a method for reconfiguring a new assembled battery by combining secondary batteries constituting a plurality of assembled batteries collected from a user.

  A battery pack composed of a plurality of secondary batteries is used as a power source for electric vehicles, hybrid vehicles, and the like. On the other hand, from the viewpoint of efficient use of resources, in assembled batteries used as power sources for vehicles, the assembled batteries collected from the user are reconfigured (rebuilt) into reusable assembled batteries and provided to the user again. Reuse technology is also being studied. When rebuilding, in an assembled battery with a history of use, battery characteristics, that is, overcharge, overdischarge, voltage variation due to memory effect, etc. change, so among the secondary batteries constituting a plurality of collected assembled batteries, In particular, it has been proposed to select and rebuild a secondary battery having excellent battery performance.

  In the following Patent Document 1, for a used secondary battery that has already been used, a process of obtaining the full charge capacity of each, and a group of used secondary batteries that have obtained the full charge capacity, There is disclosed a method for manufacturing an assembled battery, which includes a step of selecting a plurality of batteries each having a full charge capacity close to each other and a step of combining and rebuilding the selected plurality of used secondary batteries. In addition, among the selected used secondary batteries, the difference in full charge capacity between the battery with the largest full charge capacity and the battery with the smallest full charge capacity is calculated as the full charge capacity of the battery with the smallest full charge capacity. It is disclosed that it is within 10%.

JP 2009-4184 A

  When an assembled battery is used as a power source for an electric vehicle or a hybrid vehicle, the assembled battery is charged or discharged with a large current. Therefore, if the capacity of each secondary battery constituting the assembled battery is not sufficient, it deteriorates due to overcharge or overdischarge. Resulting in. Therefore, as described above, measures such as keeping the variation in the full charge capacity within 10% of the smallest full charge capacity will be taken, but since the usage history of the assembled battery collected from the user is various, It is not easy to select a secondary battery that satisfies this condition, and as a result, many secondary batteries are excluded from the rebuild target.

  An object of the present invention is to provide a method that can reduce the waste of a secondary battery when reconfiguring a new assembled battery by combining secondary batteries constituting a plurality of assembled batteries collected from a user or the market. It is in.

  The present invention relates to a secondary battery recycling method for reconfiguring an assembled battery from a plurality of used secondary batteries, with battery characteristics reflecting usage history and individual differences of the plurality of used secondary batteries. A measurement step for measuring a certain individual battery characteristic, and a step of classifying the assembled battery for reconfiguration based on the individual battery characteristic measured in the measurement step, the variation changing according to the individual battery characteristic A classification step of classifying using the permissible range, and an assembly step of reconfiguring the assembled battery for each secondary battery classified in the classification step.

  In one embodiment of the present invention, the individual battery characteristic is a full charge capacity of the secondary battery, and in the classification step, the smaller the full charge capacity of the secondary battery, the larger the tolerance of the variation. Set and classify.

  In another embodiment of the present invention, the individual battery characteristic is a voltage after self-discharge of the secondary battery, and in the classification step, the tolerance of the variation is smaller as the voltage of the secondary battery is smaller. Set a large value to classify.

  In another embodiment of the present invention, the individual battery characteristic is the weight of the secondary battery, and in the classification step, the tolerance of the variation is set to be larger as the weight of the secondary battery is smaller. Classify.

  In another embodiment of the present invention, in the classification step, the secondary battery having the individual battery characteristics equal to or greater than a threshold is classified as a vehicle-mounted battery, and the secondary battery having the individual battery characteristics less than the threshold is classified. Classify batteries as other uses. Other uses are, for example, power storage devices for wind power generation and solar power generation, or batteries for home appliances.

  According to the present invention, when reassembling (rebuilding) a new assembled battery by combining secondary batteries constituting a plurality of assembled batteries collected from a user or the market, the assembled battery is reduced in waste. Can be effectively provided to the market.

It is a flowchart which shows the reuse method of the secondary battery of embodiment. It is a graph which shows the time change of the battery characteristic of a secondary battery. It is the capacity distribution histogram of the collect | recovered secondary battery, and allowable range explanatory drawing of the dispersion | variation of embodiment. It is the capacity distribution histogram of the collect | recovered secondary battery, and allowable range explanatory drawing of the dispersion | variation of a prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. First, an assembled battery mounted as a power source for an electric vehicle or a hybrid vehicle will be briefly described as a premise of this embodiment. The following description is based on an assembled battery configured from a rectangular secondary battery (battery module) having a flat rectangular parallelepiped shape, but the present invention can also be applied to an assembled battery configured from a cylindrical secondary battery.

  The assembled battery is configured by electrically connecting a plurality of secondary batteries in series in a state of being constrained by end plates at both ends. Each secondary battery is arranged in parallel with the long side surfaces facing each other, and is electrically connected in series through a connection member. Each secondary battery is a sealed nickel-metal hydride battery made of, for example, a resin-made integral battery case. In the integrated battery case, a plurality of single cells (cells) are connected in series to form a battery module. Each unit cell is, for example, a nickel metal hydride battery, and the capacity of the negative electrode is often set larger than that of the positive electrode at the time of design, that is, in the initial state. The unit cell includes a positive electrode containing nickel hydroxide as a positive electrode active material, a hydrogen storage alloy as a negative electrode active material, and a charge reserve that is an excess capacity provided in advance when the positive electrode is not charged when it is fully charged. And a negative electrode having a discharge reserve corresponding to a previously provided excess capacity in a charged state when the positive electrode finishes discharging, and having a capacity larger than the theoretical capacity of the positive electrode.

  When mounted on a vehicle, the battery pack is monitored by a battery ECU. The battery ECU is configured to include a processor, a ROM, and a RAM, and controls charging / discharging of the assembled battery, and monitors the voltage, current, and temperature of the assembled battery to determine normality / abnormality of the assembled battery.

  In assembled batteries, it is known that the assembled battery characteristics are different from each other depending on the usage history, and the variation characteristics of the battery characteristics are also different among individual secondary batteries constituting the assembled battery due to individual differences. Accordingly, when rebuilding a new assembled battery by combining secondary batteries constituting a plurality of assembled batteries collected from the user or the market, it is necessary to select at least secondary batteries whose battery characteristics approximate each other. is there.

2. Outline of Rebuilding Next, an outline of rebuilding will be described.

  As described above, at the time of rebuilding, it is necessary to select a secondary battery whose battery characteristics are similar to each other and to assemble a new assembled battery with the selected secondary battery. As a battery characteristic used for selection, for example, there is a full charge capacity. The full charge capacity can be measured by charging and discharging the secondary battery in a predetermined pattern. For example, in a constant temperature environment of 25 ° C., the secondary battery is first discharged at a current value of 0.3 C until the battery voltage reaches 1.0 V, then left for 3 minutes, and then at a current value of 0.35 C. 3. Charge the secondary battery at a constant current for 2 hours. Next, after leaving for 3 minutes, the battery is discharged at a current value of 0.3 C until the battery voltage reaches 1.0 V, and the amount of electricity discharged at this time is defined as the full charge capacity. Note that a charge amount (for example, 6.5 AH) that satisfies the nominal capacity of the secondary battery is set to 1 C as a current amount (for example, 6.5 A) that can be completely discharged in one hour.

  When rebuilding, select a secondary battery whose variation in full charge capacity is within the allowable range, but within the allowable range of variation when rebuilding, the assembled battery is first assembled and provided to the user or the market. It is preferable to make the variation of the full charge capacity of the secondary battery smaller by making it narrower than the initial allowable range, in addition to setting it to the same level as the allowable range of this (this is the initial allowable range). The reason for this is that the battery characteristics of the assembled battery change according to the usage history as described above, and there are individual differences between the secondary batteries that make up the assembled battery. Even if it is the same level, there is a possibility that the difference in battery characteristics will become obvious and increase in use after rebuilding due to the usage history of the assembled battery to which the secondary battery belonged and the individual difference of the secondary battery itself. Because there is.

  FIG. 2 conceptually shows the time change of the full charge capacity of the secondary battery. In the figure, the horizontal axis is time, and shows the initial time when the product is first shipped, the rebuilt time, and the future time before the rebuilt time. The vertical axis represents the full charge capacity of the secondary battery. In the figure, changes with time of the full charge capacities of two different secondary batteries A and B are indicated by a and b, respectively. In the figure, for the sake of explanation, it is assumed that the full charge capacities of the secondary batteries A and B change linearly with time. Due to individual differences including the usage history of the secondary batteries A and B, the degree of time change of the full charge capacity of the secondary batteries A and B is different, and the secondary battery A is fully charged more rapidly than the secondary battery B. Capacity is reduced. Therefore, even if the full charge capacities of the two secondary batteries A and B are similar to each other at the time of rebuilding, there is a possibility that a large difference will occur between the full charge capacities of both in the future after rebuilding. Considering such a possibility, at least at the time of rebuilding, it is necessary to make the allowable range of variation in the full charge capacity between the secondary batteries smaller than at the initial time. For example, if the allowable range of variation at the initial time is 5%, the allowable range of variation at the time of rebuilding is set to 2%.

  By the way, if the allowable range of variation at the time of rebuilding is reduced in this way, secondary batteries that are outside the allowable range of this variation may appear, and if these are uniformly excluded from the targets of rebuilding, The battery cannot be used effectively.

  Therefore, in the present embodiment, the assembled battery obtained by rebuilding is obtained by rebuilding in consideration of other uses besides the assembled battery that is mounted on a vehicle and used as a power source for driving the vehicle. The use of the assembled battery is not limited to in-vehicle use, but other uses are actively allowed, and the fact that the allowable range of variation in full charge capacity may change depending on the use makes it possible to The allowable range of variation in charge capacity is changed according to the full charge capacity.

3. Rebuilding Method of Embodiment FIG. 1 shows a flowchart of the rebuilding method in the present embodiment. First, a plurality of assembled batteries are collected from the user or the market (S101). Specifically, when an electric vehicle or a hybrid vehicle becomes a scrapped vehicle, the assembled battery mounted on the vehicle is collected. Alternatively, when the battery pack is replaced with a new battery pack due to some malfunction of the secondary battery constituting the battery pack, the old battery pack is collected. This is because other secondary batteries other than the secondary battery in which the malfunction has occurred can operate normally.

  Next, the collected assembled battery is disassembled for each secondary battery (S102). When disassembling each secondary battery, it can be disassembled using a dedicated instrument, and it is preferable to disassemble in a state where a predetermined pressure is applied so as to compress the assembled battery from both ends of the assembled battery. .

  Next, the full charge capacity of each secondary battery obtained by disassembly is measured (S103). The method for measuring the full charge capacity is as described above. That is, in a constant temperature environment of 25 ° C., the secondary battery is first discharged at a current value of 0.3 C until the battery voltage reaches 1.0 V, then left for 3 minutes, and then at a current value of 0.35 C. 3. Charge the secondary battery at a constant current for 2 hours. Next, after leaving for 3 minutes, the battery is discharged at a current value of 0.3 C until the battery voltage reaches 1.0 V, and the amount of electricity discharged at this time is defined as the full charge capacity. Note that this method is an example, and the full charge capacity may be measured using another method with the secondary battery fully charged. For example, when the secondary battery is a lithium ion battery, constant current charging is performed in the first half of charging, and constant voltage charging is performed in the second half of charging.

  Next, for each full charge capacity of the secondary battery, an allowable range of variation in full charge capacity when rebuilding is set (S104). Specifically, the allowable range of variation is not set to a constant value, but the allowable range of variation is set larger as the full charge capacity is smaller. In other words, the larger the full charge capacity, the smaller the allowable range of variation.

  FIG. 3 shows the relationship between the full charge capacity histogram and the allowable range of variation in this embodiment. In the figure, the horizontal axis is the full charge capacity, and the vertical axis is the number of recovered secondary batteries. The number of recovered secondary batteries has a distribution with a peak at a certain full charge capacity, as shown in a graph 100. Then, assuming that allowable ranges of variation when rebuilt as a battery pack from a secondary battery having a large full charge capacity to a secondary battery having a small full charge capacity are c0, c1, c2, and c3, respectively, c0 <c1 <c2 <C3 is set. For example, c0 = 2%, c1 = 3%, c2 = 4%, c3 = 20%, and the like. Increasing the allowable range of variation as the full charge capacity becomes smaller is that the full charge capacity is large, that is, the secondary battery having a full charge capacity close to the initial full charge capacity is less affected by usage history and less deteriorated. As an excellent secondary battery, an assembled battery that can be used in a special environment (for example, a cold region where the output characteristics of the battery deteriorate) with only an excellent secondary battery, that is, a new assembled battery with excellent battery characteristics While it is necessary to reduce the tolerance of the variation sufficiently for rebuilding, a secondary battery with a small full charge capacity, that is, a battery that has deteriorated considerably from the initial full charge capacity, has a large influence on the usage history, and the deterioration is Since it is an advanced secondary battery, it only needs to be rebuilt as an assembled battery that is used only for a specific application. In order to get the.

  There is a threshold value for the full charge capacity required for a secondary battery used as an in-vehicle assembled battery. For example, it can be set to about 70% of the initial capacity, but FIG. 3 shows a threshold full charge capacity. Is shown as FCth. A secondary battery whose full charge capacity reaches the threshold full charge capacity is rebuilt as an in-vehicle assembled battery. Among them, the secondary battery has a relatively small full charge capacity and a relatively large tolerance range. An assembled battery obtained by rebuilding (for example, secondary batteries included in c1 and c2 whose allowable range of variation is not c0) is used for vehicles that are assumed to be used in a temperate region, for example. On the other hand, a secondary battery whose full charge capacity is less than the threshold full charge capacity (variation tolerance c3) is rebuilt as an assembled battery other than a vehicle, but does not need to be charged and discharged with a large current unlike a vehicle. Therefore, there is no practical problem even if the tolerance of variation is relatively large. An example of an application other than in-vehicle use is a storage application. In storage applications, the battery is often discharged in a short time and charged at a constant voltage. Therefore, even if there is a large variation in the full charge capacity of the secondary batteries constituting the assembled battery, problems are unlikely to occur. A storage application is generally defined as a power storage application when charging is performed at a constant voltage, discharged at a relatively small current compared to an electric vehicle or a hybrid vehicle, and less frequently left in an intermediate capacity range. Specifically, they are power storage devices such as wind power generation, solar power generation, and solar thermal power generation, or batteries for home appliances such as vacuum cleaners. Note that secondary batteries whose variation tolerance is other than c0 to c3 are discarded because they cannot be used for any application.

  Returning to FIG. 1 again, after setting the allowable range of variation according to the full charge capacity as described above, it is classified (distributed) within any allowable range of variation (S105). And an assembled battery is rebuilt as another use for every classification (S106). For example, in FIG. 3, if the secondary battery groups that fall within the variation tolerance ranges c0, c1, c2, and c3 are A0, A1, A2, and A3, respectively, the secondary battery groups A0, A1, and A2 are used as in-vehicle assembled batteries. Rebuild and A3 rebuild for storage use. The secondary battery groups A0 to A2 are both rebuilt into the in-vehicle assembled battery. However, since the full charge capacity and the allowable range of variation are different from each other, as described above, it is preferable for vehicles in different use environments. .

  For comparison with this embodiment, FIG. 4 shows the relationship between the histogram of the full charge capacity and the allowable range of variation in the prior art. The graph 100 in FIG. 4 is the same as the graph 100 in FIG. Conventionally, the allowable range of variation is constant at c (for example, 2%) regardless of the full charge capacity, and the assembled battery is rebuilt by selecting secondary batteries whose full charge capacities are close to each other. Since the allowable range of variation is constant as c, the number of secondary batteries for rebuilding to a certain assembled battery is limited, and as a result, there are cases where it cannot be reused as an assembled battery. Further, a secondary battery having a threshold full charge capacity less than FCth is discarded because it cannot be reused for in-vehicle use. On the other hand, in the present embodiment, since the allowable range of variation is set to be larger as the full charge capacity is smaller, there is a surplus in the number of secondary batteries to be rebuilt into the assembled battery, and from the user or the market The recovered secondary battery can be reused efficiently.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible.

  For example, in the present embodiment, the secondary battery is classified based on the full charge capacity, but the secondary battery may be classified using a voltage after self-discharge instead of the full charge capacity. Disassemble the assembled battery collected from the user or the market into secondary batteries, charge each secondary battery quantitatively, and then measure the voltage of the secondary battery after leaving it at a constant temperature, for example, at 40 ° C. . Secondary batteries are classified based on the voltage after self-discharge. Then, as the voltage after self-discharge is smaller, the allowable range of variation is set larger and the secondary batteries are classified. If the absolute value of the voltage after self-discharge or the amount of change (or the degree of change) from the initial state is greater than or equal to the threshold value, it will be rebuilt as an in-vehicle assembled battery. Rebuild as a storage application.

  Moreover, you may classify | categorize using the weight of a secondary battery. When the secondary battery is used, the amount of the electrolyte decreases, so that its weight decreases. The amount of the reduction can change according to the usage history and the individual difference of the secondary battery. The smaller the weight of the secondary battery, the larger the allowable range of variation is set, and the assembled battery is rebuilt.

  The full charge capacity, the voltage after self-discharge, and the weight of the secondary battery are battery characteristics reflecting the use history of the secondary battery and individual differences, and can be said to be individual battery characteristics of each secondary battery. Therefore, in this sense, the method according to the present embodiment, when classifying the plurality of secondary batteries obtained by disassembling the assembled battery collected from the user or the market according to the individual battery characteristics, Accordingly, it can be expressed that the allowable range of variation when rebuilding to the same assembled battery is not a constant value, but is changed according to the value of the individual battery characteristics. The individual battery characteristics do not need to be any one, and the secondary batteries may be classified using a plurality of physical quantities such as a combination of the full charge capacity and the voltage after self-discharge.

  Further, in the present embodiment, according to the full charge capacity, the allowable range of variation is set larger as the full charge capacity is smaller, but the upper limit of the allowable range of variation when rebuilt as an in-vehicle assembled battery is the initial state In other words, it is preferable to set an allowable range of variation when the assembled battery is shipped. For example, if the allowable range of variation at the time of shipment of the assembled battery is within 5%, the allowable range of variation at the time of rebuilding is set to 2% to 5% in the in-vehicle assembled battery. Referring to FIG. 3, c0 = 2%, c1 = 3%, c2 = 4%, etc. For a secondary battery whose full charge capacity is less than the threshold value FCth, the allowable range of variation may be set regardless of the allowable range of variation at the time of battery pack shipment, for example, 20% to 30% or You may set more. The same applies to classification using voltage after self-discharge and others.

  Furthermore, in the present embodiment, the secondary battery is rebuilt by setting the allowable range of variation based on the basic technical idea that the allowable range of variation of the secondary battery varies depending on the use of the assembled battery. Although it is used effectively, it is natural that the allowable range of variation of the secondary battery varies depending on the economic factor of the assembled battery, and the present invention does not exclude such an aspect, The allowable range of variation may be further adjusted in consideration of the price of the assembled battery obtained in this way.

  100 Histogram of recovered secondary battery.

Claims (6)

A secondary battery recycling method for reconfiguring a battery pack from a plurality of used secondary batteries,
A measurement step for measuring individual battery characteristics, which are battery characteristics reflecting the use history and individual differences of a plurality of used secondary batteries;
A classification step for reconfiguring the assembled battery based on the individual battery characteristics measured in the measurement step, the classification step using a tolerance range of variation that varies according to the individual battery characteristics; ,
An assembly step of reconfiguring the assembled battery for each secondary battery classified in the classification step;
A method for reusing a secondary battery, comprising: The method of claim 1, wherein
The solid battery characteristic is a full charge capacity of the secondary battery,
In the classification step, the secondary battery is reused by classifying the secondary battery by setting a larger allowable range of variation as the full charge capacity of the secondary battery is smaller. The method of claim 1, wherein
The solid battery characteristic is a voltage after self-discharge of the secondary battery,
In the classifying step, as the voltage of the secondary battery is smaller, the allowable range of the variation is set to be larger for classification. The method of claim 1, wherein
The solid battery characteristic is the weight of the secondary battery,
In the classification step, the secondary battery is reused by classifying the secondary battery by setting a larger allowable range of variation as the weight of the secondary battery is smaller. The method of claim 1, wherein
In the classification step, the secondary battery having the individual battery characteristics equal to or higher than a threshold value is classified as an in-vehicle assembled battery, and the secondary battery having the individual battery characteristics less than the threshold value is classified as another application. Recycle method of secondary battery. The method of claim 5, wherein
The method for reusing a secondary battery, wherein an allowable range of variation for the in-vehicle assembled battery in the classification step is set to be equal to or less than an allowable range of variation at the time of initial shipment of the assembled battery.

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