JP7061259B2 - How to recover the capacity of the secondary battery cell - Google Patents

Description

The present invention relates to a method for recovering the capacity of a secondary battery cell.

An assembled battery in which a plurality of secondary battery cells are electrically connected is widely used as a high-output power source for driving a vehicle or the like. The assembled battery generally has a configuration in which a plurality of secondary battery cells are assembled via a spacer having a refrigerant flow path (see, for example, Patent Document 1). The secondary battery cell has a structure in which an electrode body in which a positive electrode and a negative electrode are laminated via a separator is housed in a battery case. The spacer is provided with a plurality of convex ribs on the surface facing the secondary battery cell. A restraining load is applied to the assembled battery. Therefore, a load is applied to the side surface of the battery case by the ribs of the spacer, and the electrode body in the battery case is pressed so as to press the positive electrode and the negative electrode against each other.

It is known that the capacity of a secondary battery deteriorates as it is repeatedly charged and discharged. In an assembled battery, the degree of capacity deterioration differs for each secondary battery cell. Therefore, in Patent Document 2, whether or not the secondary battery can be reused by acquiring the AC internal resistance value of the used secondary battery and comparing it with a preset AC internal resistance threshold so that the secondary battery can be used for a longer period of time. (That is, a technique for determining whether or not the assembled battery can be applied to a reconstructed product) has been proposed.

Japanese Unexamined Patent Publication No. 2016-091665 JP-A-2015-222195

However, according to the studies by the present inventors, it has been found that there is room for improvement in the above-mentioned prior art from the viewpoint of long-term use of the secondary battery cell used in the form of an assembled battery.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for enabling a longer-term use of a secondary battery cell used in the form of an assembled battery.

The method disclosed herein is a step of disassembling a used assembled battery in which a plurality of secondary battery cells are assembled via a spacer having a refrigerant flow path, and recovering the secondary battery cell, and the recovery. This is a method for recovering the capacity of a secondary battery cell, which comprises a step of applying pressure to a region where the spacer was not in contact with the side surface of the secondary battery cell to which the spacer was in contact.
According to such a configuration, it is possible to eliminate the waviness of the electrode caused by repeated charging and discharging due to long-term use, and it is possible to recover the capacity deterioration caused by the long distance between the electrodes due to the waviness.

It is a flowchart which shows each step of the capacity recovery method of the secondary battery cell which concerns on one Embodiment of this invention. It is a perspective view which shows typically the used assembled battery which performs the capacity recovery method of the secondary battery cell which concerns on one Embodiment of this invention. It is a perspective view which shows typically the secondary battery cell of FIG. It is a vertical sectional view along the IV-IV line of FIG. It is a top view which shows the spacer of FIG. 2 schematically. It is a top view of the pressing plate used in the pressure application step of the capacity recovery method of the secondary battery cell which concerns on one Embodiment of this invention. It is a schematic diagram of the positive electrode, the negative electrode and the separator in the region where the spacer on the long side surface of the secondary battery cell constituting the assembled battery before use does not abut. It is a schematic diagram of the positive electrode, the negative electrode and the separator in the region where the spacer on the long side surface of the secondary battery cell constituting the used assembled battery did not abut.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention (for example, general configurations and manufacturing processes of assembled batteries that do not characterize the present invention) are related to the art. It can be grasped as a design matter of a person skilled in the art based on the prior art in. The present invention can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art. Further, in the following drawings, members / parts having the same action are described with the same reference numerals. Further, the dimensional relations (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relations.

FIG. 1 shows each step of the capacity recovery method of the secondary battery cell according to the present embodiment. In the method for recovering the capacity of the secondary battery cell according to the present embodiment, the used assembled battery in which a plurality of secondary battery cells are assembled via a spacer having a refrigerant flow path is disassembled, and the secondary battery cell is disassembled. A recovery step (disassembly step) S101 and a step of applying pressure to a region where the spacer was not in contact on the side surface of the recovered secondary battery cell with which the spacer was in contact (pressure application step) S102. Include.

First, the dismantling step S101 will be described. In the dismantling step S101, a used assembled battery in which a plurality of secondary battery cells are assembled via a spacer having a refrigerant flow path is disassembled, and the secondary battery cell is recovered. FIG. 2 is a perspective view schematically showing a used assembled battery 1 in which the capacity recovery method of the secondary battery cell according to the present embodiment is performed.

As shown in FIG. 2, the assembled battery 1 includes a plurality of secondary battery cells 10 as a cell, a plurality of spacers 40, a pair of end plates 50A and 50B, and a plurality of restraint bands 52. There is. The plurality of secondary battery cells 10 are arranged in a predetermined arrangement direction (X direction in FIG. 2). The pair of end plates 50A and 50B are arranged at both ends of the assembled battery 1 in the arrangement direction X. The plurality of spacers 40 are arranged between the secondary battery cells 10 and the end plates 50A and 50B and between the plurality of secondary battery cells 10 in the arrangement direction X, respectively. The plurality of restraint bands 52 are attached so as to bridge the pair of end plates 50A and 50B. The restraint band 52 is fixed to the end plates 50A and 50B by screws 54.

FIG. 3 is a perspective view schematically showing the secondary battery cell 10. FIG. 4 is a vertical cross-sectional view taken along the line IV-IV of FIG. The secondary battery cell 10 is typically a secondary battery (for example, a lithium ion secondary battery, a nickel hydrogen battery, an electric double layer capacitor, etc.) that can be repeatedly charged and discharged. The secondary battery cell 10 includes an electrode body 20, an electrolytic solution (not shown), and a battery case 30.

The battery case 30 is a housing that houses the electrode body 20 and the electrolytic solution. The battery case 30 is made of a metal such as aluminum or steel. The battery case 30 of the present embodiment has a bottomed square shape (rectangular parallelepiped shape) outer shape.

The battery case 30 has a top surface 30u, a bottom surface 30b facing the top surface 30u, a pair of short side surfaces 30n as side surfaces continuous from the bottom surface 30b, and a pair of long side surfaces 30w. The surface of the long side surface 30w is flat. The plurality of secondary battery cells 10 are arranged along the arrangement direction X so that the long side surface 30w of the battery case 30 faces the spacer 40.

A positive electrode terminal 12T and a negative electrode terminal 14T for external connection protrude from the upper surface 30u of the battery case 30. The positive electrode terminal 12T and the negative electrode terminal 14T of the adjacent secondary battery cells 10 are electrically connected by a bus bar 18. As a result, the assembled battery 1 is electrically connected in series.

As shown in FIG. 4, the electrode body 20 has a structure in which a sheet-shaped positive electrode 12 and a sheet-shaped negative electrode 14 are laminated in a state of being insulated by a sheet-shaped separator 16. In the electrode body 20, both surfaces of the positive electrode 12, the negative electrode 14, and the separator 16 perpendicular to the stacking direction are flat surfaces. The electrode body 20 may be either a laminated electrode body or a wound electrode body.

The positive electrode 12 includes a positive electrode current collector and a positive electrode active material layer 12a fixed to the surface thereof. The positive electrode active material layer 12a contains a positive electrode active material capable of reversibly storing and releasing charge carriers. The negative electrode 14 includes a negative electrode current collector and a negative electrode active material layer 14a fixed to the surface thereof. The negative electrode active material layer 14a contains a negative electrode active material capable of reversibly storing and releasing charge carriers. The separator 16 is a porous member that permeates the charge carrier and insulates the positive electrode active material layer 12a and the negative electrode active material layer 14a.

A positive electrode current collector exposed portion 12n is provided at one end (left end portion in the drawing) of the electrode body 20 in the width direction. A positive electrode current collector plate 12c for collecting foil is attached to the exposed portion 12n of the positive electrode current collector. The positive electrode 12 of the electrode body 20 is electrically connected to the positive electrode terminal 12T via the positive electrode current collector plate 12c. Further, a negative electrode current collector exposed portion 14n is provided at one end (right end portion in the drawing) of the electrode body 20 in the width direction. A negative electrode current collector plate 14c for collecting foil is attached to the negative electrode current collector exposed portion 14n. The negative electrode 14 of the electrode body 20 is electrically connected to the negative electrode terminal 14T via the negative electrode current collector plate 14c.

However, the shape, size, number, arrangement, connection method, etc. of the secondary battery cells 10 constituting the assembled battery 1 are not particularly limited and can be appropriately changed.

FIG. 5 is a plan view schematically showing the spacer 40. The spacer 40 is a plate-shaped member. The spacer 40 faces the long side surface 30w of the battery case 30. The spacer 40 has a plurality of convex ribs 42 on the surface facing the long side surface 30w. The plurality of convex ribs 42 abut on the long side surface 30w of the battery case 30. In the assembled battery 1, a plurality of secondary battery cells 10 are constrained by the restraint band 52. Therefore, a pressing load is applied to the long side surface 30w of the battery case 30 by the convex rib 42 of the spacer 40.

The convex rib 42 of the spacer 40 is formed linearly between the two long sides of the spacer 40. Thereby, the spacer 40 has a refrigerant flow path 44 between two adjacent convex ribs 42. The refrigerant flow path 44 is a space for circulating a cooling fluid (typically air) as a refrigerant. With the refrigerant flow path 44, the spacer 40 has a function as a heat sink for efficiently dissipating the heat generated inside the secondary battery cell 10 due to charging / discharging or the like. The spacer 40 is made of, for example, a resin material such as polypropylene (PP) or polyphenylene sulfide (PPS), or a metal material having good thermal conductivity.

The assembled battery 1 is a used one. Typically, the assembled battery 1 is used as a power source for driving a vehicle such as a plug-in hybrid vehicle (PHV), a hybrid vehicle (HV), or an electric vehicle (EV). The assembled battery 1 is typically collected when these vehicles are replaced or scrapped.

The assembled battery 1 can be disassembled by releasing the restraint of the assembled battery 1 and collecting the secondary battery cell 10 according to a known method. Specifically, for example, the screw 54 of the restraint band 52 is removed, and the restraint band 52 is removed. As a result, the restrained state of each secondary battery cell 10 is released. Next, each secondary battery cell 10 is collected from the pair of end plates 50A and 50B in the arranged state, the plurality of secondary battery cells 10, and the plurality of spacers 40.

Next, the pressure application step S102 will be described. In the pressure application step S102, pressure is applied to a region of the recovered secondary battery cell that the spacer is not in contact with on the side surface that the spacer is in contact with.

In the illustrated example, the spacer 40 is in contact with the long side surface 30w of the secondary battery cell 10. Since the spacer 40 has the convex rib 42, not all of the long side surfaces 30w of the secondary battery cell 10 are in contact with the spacer 40. On the long side surface 30w of the secondary battery cell 10, only the region pressed by the convex rib 42 of the spacer 40 is in contact with the spacer 40. Therefore, for example, in the long side surface 30w of the secondary battery cell 10, the region facing the refrigerant flow path 44 does not abut on the spacer 40. Further, in the illustrated example, even in the portion facing the end portion in the longitudinal direction of the spacer 40, there is a region not pressed by the convex rib 42, that is, a region not in contact with the spacer 40.

Therefore, in the pressure application step S102, specifically, for example, first, a pressing plate 60 as shown in FIG. 6 is prepared. The pressing plate 60 is a member for pressing the long side surface 30w of the secondary battery cell 10. Both main surfaces of the pressing plate 60 (that is, the two facing surfaces having the largest areas) have the same area as both main surfaces of the spacer 40. As shown in the figure, a plurality of convex portions 62 are provided on the surface of the pressing plate 60 facing the long side surface 30w of the secondary battery cell 10. The plurality of convex portions 62 of the pressing plate 60 are provided at locations in the spacer 40, such as the refrigerant flow path 44, corresponding to locations where the convex ribs 42 are not provided. Further, the portion of the pressing plate 60 corresponding to the convex rib 42 of the spacer 40 is a concave portion 64 sandwiched between the convex portions 62. Therefore, the pressing plate 60 and the spacer 40 have a relationship in which the convex portion and the concave portion are reversed.

The pressing plate 60 is arranged at the same position as the spacer 40 on the long side surface 30w of the secondary battery cell 10. By being arranged at the same position, the convex portion 62 of the pressing plate 60 abuts only on the region not pressed by the convex rib 42 of the spacer 40 on the long side surface 30w of the secondary battery cell 10. Then, the long side surface 30w of the secondary battery cell 10 is pressed via the pressing plate 60 by an appropriate restraining jig or a pressure applying device. The pressing is performed by applying a load such that the pressure is transmitted to the electrode body 20 through the battery case 30 of the secondary battery cell 10.

By doing so, the pressure can be applied only to the region where the spacer 40 on the long side surface 30w of the secondary battery cell 10 is not in contact with the spacer 40. As a result, the capacity of the secondary battery cell 10 can be recovered. The reason why the capacity of the secondary battery cell 10 is restored is as follows.

FIG. 7 schematically shows a positive electrode 12, a negative electrode 14, and a separator 16 in a region where the spacer 40 on the long side surface 30w of the secondary battery cell 10 constituting the assembled battery 1 before use does not abut. FIG. 8 schematically shows a positive electrode 12, a negative electrode 14, and a separator 16 in a region where the spacer 40 on the long side surface 30w of the secondary battery cell 10 constituting the used assembled battery 1 did not abut.

As shown in FIG. 7, before use, the positive electrode 12 and the negative electrode 14 facing each other via the separator 16 are located at equal distances from each other. When the secondary battery cell 10 is repeatedly charged and discharged, the negative electrode 14 repeats expansion and contraction. Since the region where the spacer 40 on the long side surface 30w of the secondary battery cell 10 is not in contact is not pressed by the convex rib 42 of the spacer 40, in this region, the negative electrode 14 is repeatedly expanded and contracted. Is transformed. The deformation of the negative electrode 14 occurs so as to generate undulations, as shown in FIG.

When undulation occurs in the negative electrode 14, a portion of the negative electrode 14 facing the positive electrode 12 is formed far from the positive electrode 12. That is, in the negative electrode 14, a portion having a long pole-to-pole distance is formed. If the distance between the poles is too long, the charge carrier (eg, lithium ion) cannot move between the poles, resulting in reduced capacitance.

On the other hand, in the capacity recovery method according to the present embodiment, the region not pressed by the convex rib 42 of the spacer 40 on the long side surface 30w of the secondary battery cell 10 is pressed. By this pressing, the negative electrode 14 is deformed so that the waviness is eliminated. As a result, the distance between the electrodes is optimized on the surface of the negative electrode 14 facing the positive electrode 12, the charge carrier (eg, lithium ion) can move between the electrodes again, and the deteriorated capacity is recovered.

The shape and arrangement of the convex rib 42 of the spacer 40 is not limited to the above. Therefore, the shape and arrangement of the refrigerant flow path 44 of the spacer 40 is not limited to the above.
Further, in the above, the pressure is applied only to the region where the spacer 40 on the long side surface 30w of the secondary battery cell 10 is not in contact with the spacer 40. However, in the pressure application step S102, the pressure may also be applied to the portion of the secondary battery cell 10 where the spacer 40 on the long side surface 30w is in contact. For example, as the pressing plate 60, a flat plate-shaped pressing plate may be used. At this time, pressure is applied to both the portion where the spacer 40 on the long side surface 30w of the secondary battery cell 10 does not abut and the portion where the spacer 40 on the long side surface 30w of the secondary battery cell 10 abuts. Even in this case, the waviness of the electrode can be eliminated.

Therefore, in the pressure application step S102, it is advisable to appropriately select pressure application conditions (eg, load and time) such that the waviness of the electrode is eliminated.

In the above, the pressure application step S102 was carried out using the pressing plate, but the method of applying the pressure is not limited to the above. There is no particular limitation on the method of applying pressure as long as the method can eliminate the waviness of the electrode.

The usable period of the secondary battery cell 10 whose capacity has been restored as described above is extended. The rechargeable battery cell 10 whose capacity has been restored may be reused in the form of an assembled battery for the intended use, or may be reused in the form of an assembled battery or a cell for other purposes. good.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such specific examples.

<Test method>
An assembled battery in which a plurality of lithium ion secondary battery cells are assembled via a spacer having a refrigerant flow path is prepared. In this assembled battery, the spacer had the shape shown in FIG. The assembled battery was set to a SOC of 60% and stored at 60 ° C. for 120 days to deteriorate the capacity. The restraint state of the assembled battery was released, and the lithium ion secondary battery cell was recovered.
A flat plate-shaped pressing plate and a pressing plate having the shape shown in FIG. 6 were prepared. (Since the pressing plate having the shape shown in FIG. 6 has a comb-shaped cross section, the pressing plate having the shape shown in FIG. Is referred to as a "comb-shaped pressing plate").
A flat plate-shaped pressure plate and a comb-shaped pressure plate are placed on the side surface of the lithium ion secondary battery cell at the same position where the spacer was placed, and are shown in Table 1 in an environment of 25 ° C. Pressure was applied under the conditions shown (load and time). In this way, when the flat plate-shaped pressing plate is used, both the portion where the spacer on the side surface of the secondary battery cell does not abut and the portion where the spacer on the side surface of the secondary battery cell abuts are pressed. Was done. When the comb-shaped pressing plate was used, only the portion where the spacer on the side surface of the secondary battery cell did not abut was selectively pressed.
In the above, the capacity of the secondary battery cell before storage at 60% SOC and 60 ° C. for 120 days was measured as the initial capacity. Further, after applying pressure with the pressing plate, the battery capacity of the secondary battery cell was measured, and the ratio (percentage) of the initial capacity to the capacity at this time was determined as the capacity retention rate. For comparison, the capacity of the secondary battery cell (that is, the secondary battery cell without pressing) after storage at 60% SOC and 60 ° C. for 120 days was measured, and the ratio of the initial capacity to the capacity at this time was measured. (Percentage) was calculated as the capacity retention rate. The results are shown in Table 1.

From Table 1, it can be seen that the capacity of the secondary battery cell can be restored by applying pressure to the portion where the spacer on the side surface of the secondary battery cell does not abut. Further, it can be seen that the capacity can be recovered with a small load by selectively applying the pressure only to the portion where the spacer on the side surface of the secondary battery cell does not abut.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The techniques described in the claims include various modifications and modifications of the specific examples exemplified above.

1 set battery 10 secondary battery cell 12 positive electrode 14 negative electrode 16 separator 20 electrode body 30 battery case 40 spacer 42 convex rib 44 refrigerant flow path 50A, 50B end plate 52 restraint band 54 screw 60 pressing plate 62 convex part 64 concave

Claims (1)

A step of disassembling a used assembled battery in which a plurality of secondary battery cells are assembled via a spacer having a refrigerant flow path and collecting the secondary battery cell , wherein the spacer has a plurality of convex ribs. The surface on which the unevenness is formed is in contact with the side surface of the secondary battery cell, and the electrode included in the secondary battery cell is deformed and waviness occurs. On the side surface of the recovered secondary battery cell with which the spacer was in contact, the unevenness of the surface on which the unevenness of the spacer was formed is opposite to the region where the convex rib of the spacer was not in contact. A method for recovering the capacity of a secondary battery cell, which comprises a step of applying a pressure so as to eliminate the waviness of the electrode by using a pressing plate having the unevenness .

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