JP7176416B2 - How to reuse secondary batteries - Google Patents

Description

The present disclosure relates to a method of reusing a secondary battery.

In general, a power storage device includes a plurality of secondary batteries arranged in one direction and a restraint that binds the arranged secondary batteries.

When the power storage device is used for a long period of time, gas may accumulate in the secondary battery, increasing the internal pressure. Therefore, when the restraint is removed in order to reuse the secondary battery of the used power storage device, the secondary battery may expand. As a result, even if the secondary battery has a performance that allows it to be reused, the expansion of the secondary battery may damage the case of the secondary battery. As a result, there is a possibility that the secondary battery cannot be reused.

Therefore, in the secondary battery inspection method described in Japanese Patent Application Laid-Open No. 2016-131076, the restraint load applied to the secondary battery by the restraint provided in the power storage device is measured, and the restraint load is smaller than a predetermined value. It is sometimes employed as a reusable battery.

JP 2016-131076 A

When the secondary battery is charged and discharged, it generates heat and deforms so that the electrode body expands.

On the other hand, in a state where the secondary battery is mounted in the power storage device, the portion of one secondary battery that is exposed to the outer surface has high heat dissipation, and the portion that is not exposed to the outside has high heat dissipation. Low heat dissipation. Therefore, the temperature does not easily rise in the portion with high heat dissipation, and the temperature tends to rise in the portion with low heat dissipation.

As a result, the electrode body has a portion that easily expands, shrinks, and deforms, and a portion that does not easily deform. accumulated.

On the other hand, when the secondary battery is incorporated in the power storage device, a large load is applied from the restraint to the storage case of the secondary battery, and the electrode body is deformed in the storage case. It is difficult to create a space for As a result, deformation of the electrode body is suppressed.

However, when the secondary battery is removed from the power storage device and stored for a predetermined period of time in order to reuse the secondary battery, the storage case expands or contracts according to changes in the ambient temperature. transform. As a result, a gap is formed between the electrode body and the storage case, and the electrode body may deform within the secondary battery over time.

When the electrode body is deformed, a spaced portion is generated in which the distance between the positive electrode mixture layer of the positive electrode sheet and the negative electrode mixture layer of the negative electrode sheet is increased.

If a secondary battery including an electrode body having such a spaced portion is reassembled in a power storage device and used, the spaced portion has a high electrical resistance. On the other hand, in the normal portion where the distance between the negative electrode mixture layer and the positive electrode mixture layer is normal, the current concentrates in the vicinity portion located near the separation portion.

As a result, lithium ions do not fully enter the negative electrode mixture layer in the adjacent portion, and lithium tends to deposit on the negative electrode mixture layer.

In addition, the electrolytic solution tends to enter the spaced portion, and a large amount of lithium ions tend to exist in the vicinity of the spaced portion, and lithium tends to deposit in the vicinity of the spaced portion.

The present disclosure has been made in view of the problems described above, and an object thereof is to provide a method for reusing a secondary battery that takes out a secondary battery that has been incorporated in a power storage device and incorporates it into the power storage device again. In the above, an object of the present invention is to provide a method for reusing a secondary battery in which harmful effects such as deposition of lithium are suppressed in the built-in secondary battery.

A secondary battery reuse method according to the present disclosure includes a step of preparing a first power storage device including a plurality of constrained secondary batteries, a step of releasing the constrained state of the secondary batteries, and a step of releasing the constrained state. a step of applying pressure to the secondary battery, a step of releasing the secondary battery from the pressure, and a step of mounting the secondary battery released from the pressure to the second power storage device.

According to the above-described secondary battery reuse method, pressure is applied to the secondary battery when storing the secondary battery taken out from the first power storage device. Therefore, the electrode body in the secondary battery is less likely to deform, and the formation of gaps in the electrode body can be suppressed. Accordingly, even if the secondary battery is incorporated in the second power storage device, it is possible to suppress the occurrence of adverse effects such as lithium deposition.

According to the method for reusing a secondary battery according to the present disclosure, when a secondary battery that has been incorporated in a power storage device is taken out and re-assembled into another power storage device, the re-installed secondary battery It is possible to suppress the occurrence of adverse effects such as deposition of lithium in the interior.

1 is a plan view schematically showing power storage device 1 according to the present embodiment. FIG. 2 is a perspective view showing a secondary battery 2; FIG. FIG. 3 is a schematic diagram schematically showing each step of a method for recycling the secondary battery 2. FIG. 4 is a perspective view showing a storage device 40 and a positive electrode sheet 20; FIG. FIG. 3 is a schematic diagram schematically showing a method of recycling a secondary battery 2B according to a comparative example;

A method for recycling a secondary battery according to the present embodiment will be described with reference to FIGS. 1 to 5. FIG. Among the configurations shown in FIGS. 1 to 5, the same or substantially the same configurations are denoted by the same reference numerals, and overlapping descriptions are omitted. In addition, in the configurations described in the embodiments, configurations corresponding to configurations described in claims may be written together with the configurations in the claims in parentheses.

FIG. 1 is a plan view schematically showing a power storage device 1 according to this embodiment. Power storage device 1 includes a plurality of secondary batteries 2 , a restraint 3 , and a plurality of busbars 4 .

A plurality of secondary batteries 2 are provided so as to be arranged in the arrangement direction D1. A plate-like member made of resin or the like is arranged between the secondary batteries 2 .

FIG. 2 is a perspective view showing the secondary battery 2. FIG. In the present embodiment, an example in which a lithium ion battery is used as secondary battery 2 will be described, but secondary battery 2 may be a nickel-metal hydride battery.

The secondary battery 2 includes a housing case 10 , an electrode body 11 , a positive electrode terminal 12 , a negative electrode terminal 13 and an electrolytic solution 14 .

The storage case 10 includes main surfaces 17A and 17B, side surfaces 18A and 18B, a top surface 19A and a bottom surface 19B. The housing case 10 is formed in a flat shape and is formed thin in the arrangement direction D1.

The main surface 17A and the main surface 17B are arranged in the arrangement direction D1, and the side surfaces 18A and 18B are arranged in the width direction W.

The housing case 10 includes a case body 15 and a lid 16 . The case body 15 and the lid 16 are made of metal material such as aluminum or aluminum alloy.

The case body 15 is formed to open upward. The lid 16 is provided so as to close the opening of the case body 15 .

The electrode body 11 and the electrolytic solution 14 are housed in the housing case 10 . The electrode assembly 11 includes a positive electrode sheet 20 , a separator 21 and a negative electrode sheet 22 . In the example shown in FIG. 2, the electrode body is a wound electrode body in which a positive electrode sheet 20, a separator 21, and a negative electrode sheet 22 are superimposed and wound. is formed, and a negative electrode 24 is formed at the other end. A separator 21 is arranged between the positive electrode sheet 20 and the negative electrode sheet 22 .

The positive electrode sheet 20 includes a plate-shaped current collector and a positive electrode mixture layer formed on the current collector. A current collector of the positive electrode sheet 20 is made of aluminum or the like.

The positive electrode mixture layer is formed on at least one of the front and back surfaces of the current collector, and the positive electrode mixture layer includes a positive electrode active material, a conductive material, a binder, and the like. The positive electrode active material may contain, for example, at least one selected from the group consisting of lithium cobaltate, lithium nickelate, lithium manganate, nickel-cobalt lithium aluminate, nickel-cobalt lithium manganate and lithium iron phosphate. .

The separator 21 is a porous membrane such as non-woven fabric.
The negative electrode sheet 22 includes a plate-shaped current collector and a negative electrode mixture layer formed on the current collector. A current collector of the negative electrode sheet 22 is, for example, copper. The negative electrode mixture layer includes a negative electrode active material, a binder, and the like. The negative electrode active material is graphite, for example.

The electrode body 11 may be a laminate type electrode body in which a plurality of positive electrode sheets 20 , a plurality of separators 21 and a plurality of negative electrode sheets 22 are laminated.

The electrolytic solution 14 contains a supporting electrolyte and a solvent. The supporting salt is, for example, _LiPF6 . Unit size includes EC, DMC, and EMC. In addition, "EC" shows ethylene carbonate. "DMC" indicates dimethyl carbonate. "EMC" denotes ethyl methyl carbonate.

The positive terminal 12 and the negative terminal 13 are provided on the upper surface of the lid 16 . The positive electrode terminal 12 is electrically connected to the positive electrode 23 of the electrode assembly 11 , and the negative electrode terminal 13 is electrically connected to the negative electrode 24 of the electrode assembly 11 .

Returning to FIG. 1 , the restraint 3 includes end plates 30 and 31 and a restraint band 32 . End plate 30 is provided on one end side of power storage device 1 in arrangement direction D<b>1 , and end plate 31 is provided on the other end side of power storage device 1 . Restraint band 32 is provided to connect end plate 30 and end plate 31 .

A plurality of secondary batteries 2 are provided between end plates 30 and 31 . A binding force is applied to the plurality of secondary batteries 2 by a binding band 32 that connects the end plates 30 and 31, and the plurality of secondary batteries 2 are fixed between the end plates 30 and 31. there is The bus bar 4 electrically connects the secondary batteries 2 adjacent to each other in the arrangement direction D1 in series.

Power storage device 1 configured as described above is mounted, for example, in an electrically powered vehicle such as a hybrid vehicle or an electric vehicle. The power storage device 1 mounted on the electric vehicle is repeatedly charged and discharged, and each secondary battery 2 is also repeatedly charged and discharged.

In FIG. 2, when the secondary battery 2 is charged and discharged, the temperature of the electrode body 11 rises. When the temperature of the electrode body 11 rises, the electrode body 11 expands and deforms. At this time, both end sides of the electrode body 11 in the width direction W are likely to radiate heat to the outside through the side surfaces 18A and 18B of the housing case 10 . On the other hand, since the main surfaces 17A and 17B of the housing case 10 are in contact with the insulating plates adjacent to each other in the arrangement direction D1, the central portion of the electrode body 11 in the width direction W is difficult to dissipate heat to the outside. Temperature rises easily.

Therefore, at the central portion of the electrode body 11 in the width direction W, greater deformation is repeated than at both end sides of the electrode body 11 .

As a result, the electrode body 11 is repeatedly charged and discharged for a long period of time, and an internal stress is generated that causes the electrode body 11 to deform within the housing case 10 . Therefore, when the electrode body 11 is placed in a natural state, the electrode body 11 tends to deform due to the internal stress.

On the other hand, since each containing case 10 is pressed by the restraining force applied from the end plates 30 and 31, a gap is formed between the containing case 10 and the electrode body 11 for deformation of the electrode body 11. hard. As a result, deformation of the electrode body 11 is suppressed when the secondary battery 2 is attached to the power storage device 1 .

Here, for example, it is assumed that the restrained state by the restraint 3 is released and the secondary battery 2 is stored for a predetermined period. During storage, the storage case 10 may be deformed to expand due to the surrounding ambient temperature. At this time, a gap is formed between the housing case 10 and the electrode body 11, and the electrode body 11 is deformed by the internal stress. During the storage period, the storage case 10 is repeatedly deformed so as to expand according to the ambient temperature, so that the electrode body 11 is gradually deformed inside the storage case 10 .

When the electrode body 11 is deformed, gaps are likely to occur in the electrode body 11 . When a gap occurs in the electrode body 11, the distance between the positive electrode mixture layer of the positive electrode sheet 20 and the negative electrode mixture layer of the negative electrode sheet 22 increases in the gap.

Next, a method for reusing the secondary battery 2 by taking out the secondary battery 2 from the power storage device 1 configured as described above and incorporating the taken out secondary battery 2 into another power storage device 1A again. explain.

FIG. 3 is a schematic diagram schematically showing each step of the method for recycling the secondary battery 2. As shown in FIG. The reuse method of the secondary battery 2 includes a preparation step S1, a separation step S2, a storage step S3, a release step S4, and an assembly step S5.

The preparation step S<b>1 is a step of preparing the power storage device 1 . For example, it is a step of removing from the electric vehicle the power storage device 1 that has been mounted on the electric vehicle and has been used for a long period of time.

The separation step S<b>2 is a step of taking out the secondary battery 2 from the power storage device 1 . Specifically, it includes a step of removing the restraint 3 from the power storage device 1 , a step of releasing the plurality of secondary batteries 2 from the restricted state, and a step of removing each secondary battery 2 from the power storage device 1 .

The storage step S<b>3 is a step of storing the secondary battery 2 using the storage device 40 . In general, it often takes a considerable amount of time to incorporate the secondary battery 2 removed from the power storage device 1 into another power storage device. This is because, for example, the battery performance of the secondary battery 2 that has been taken out may be inspected, or the presence or absence of defects in the containing case 10 of the secondary battery 2 may be checked. Furthermore, this is because there may be a situation where a power storage device to be newly incorporated has not been selected.

In storage step S<b>3 of the present embodiment, storage device 40 is used to store secondary battery 2 . FIG. 4 is a perspective view showing the storage device 40 and the positive electrode sheet 20. FIG.

The storage device 40 includes a plurality of restraining plates 41, a plurality of bolts 42a, 42b, 42c and 42d, and a plurality of nuts 43a, 43b, 43c and 43d. The restraint plate 41 is formed in a plate shape and is made of metal such as iron, for example. Each constraining plate 41 is formed so as to be arranged in the arrangement direction D2 such that the main surfaces of each constraining plate 41 face each other.

In addition, in the example shown in FIG. 4, the restraint plate 41 is formed in a rectangular shape. A plurality of through holes 46 a , 46 b , 46 c and 46 d are formed in the restraining plate 41 , and the through holes 46 a , 46 b , 46 c and 46 d are formed near corners of the restraining plate 41 . The through holes 46a, 46b, 46c, and 46d formed in the restraining plates 41 adjacent to each other in the arrangement direction D2 are arranged in the arrangement direction D2.

Bolts 42 a , 42 b , 42 c , 42 d include heads 44 and shafts 45 . The shaft 45 is inserted through a plurality of through holes 46a, 46b, 46c, 46d arranged in the arrangement direction D2. Nuts 43a, 43b, 43c, 43d are attached to the lower ends of shafts 45 of bolts 42a, 42b, 42c, 42d.

In storage device 40 configured as described above, secondary battery 2 removed from power storage device 1 is placed between restraining plates 41 . By tightening the nuts 43 a , 43 b , 43 c and 43 d , the secondary battery 2 is sandwiched between the restraining plates 41 . Thereby, main surface 17A and main surface 17B of secondary battery 2 are pressed by restraining plate 41 .

By pressing main surface 17A and main surface 17B in this way, pressure is also applied to electrode body 11 in secondary battery 2, and deformation of electrode body 11 is suppressed. Specifically, formation of a gap between the housing case 10 and the electrode body 11 is suppressed, and deformation of the electrode body 11 can be suppressed.

In the separation step S2, it is preferable to apply pressure to the secondary battery 2 in the storage device 40 immediately after taking out the secondary battery 2. FIG. For example, it is preferable to restrain secondary battery 2 in storage device 40 within several hours.

There is no particular limitation on the period during which secondary battery 2 is stored in a restrained state in storage device 40, but storage is performed for several weeks to several months, for example.

Returning to FIG. 3, in the release step S4 after the storage step S3, the pressurized state of the secondary battery 2 by the storage device 40 is released. Specifically, in FIG. 4 , the nuts 43 a , 43 b , 43 c , 43 d are loosened to release the pressurized state of the secondary battery 2 by the restraining plate 41 .

The assembling step S<b>5 is a step of assembling the secondary battery 2 removed from the storage device 40 into a power storage device 1</b>A different from the power storage device 1 . It is preferable to incorporate the secondary battery 2 removed from the storage device 40 into the power storage device 1A within several hours.

According to the method for reusing the secondary battery 2 described above, it is possible to suppress the formation of gaps in the electrode body 11 in the storage step S3.

Next, a method for reusing the secondary battery according to the comparative example will be described and compared with the method for reusing the secondary battery 2 according to the present embodiment.

FIG. 5 is a schematic diagram schematically showing a reuse method of a secondary battery 2B according to a comparative example. A method for reusing the secondary battery 2B according to the comparative example includes a preparation step S1, a separation step S2, a storage step S3A, and an assembly step S5A. In the comparative example, there is no release step S4.

Also in the comparative example, the power storage device 1B is prepared in the preparation step S1. Then, in the separation step S2, the secondary battery 2B is taken out from the power storage device 1B.

Next, in the storage step S3A, the secondary battery 2B is stored without applying an external force. Then, for example, in the storage step S3A, it is stored for several weeks to several months.

Here, since the restraint state by the restraint 3 of the power storage device 1B is released, the secondary battery 2B is stored in a natural state during storage. Therefore, the housing case 10B of the power storage device 1B may expand and deform due to the ambient temperature, forming a gap between the housing case 10B and the secondary battery 2B.

At this time, in the secondary battery 2B, which has been repeatedly charged and discharged for a long period of time, internal stress is accumulated in the secondary battery 2B due to the existence of portions where heat is easily dissipated and portions where heat is not easily dissipated. Therefore, when the secondary battery 2 is stored in a natural state, a gap is formed between the storage case 10B and the electrode body 11B, and the electrode body 11B is deformed by the internal stress. During the storage period, the electrode body 11B is gradually deformed in the storage case 10B by repeating the expansion and deformation of the storage case 10B according to the ambient temperature.

When the electrode body 11B is deformed in this manner, a gap is likely to occur in the electrode body 11B. When a gap occurs in the electrode body 11B, the distance between the positive electrode mixture layer of the positive electrode sheet and the negative electrode mixture layer of the negative electrode sheet is increased in the gap.

In the assembly step S5A, the secondary battery 2B stored in the release step S4A is assembled into the power storage device 1C. Specifically, the secondary battery 2B is restrained by the restraint 3 of the power storage device 1C.

At this time, even if the secondary battery 2B is restrained by the restraint 3, the gap formed in the electrode body 11B may remain.

If a gap remains in the electrode body 11B, a wide gap is generated between the positive electrode mixture layer of the positive electrode sheet 20 and the negative electrode mixture layer of the negative electrode sheet 22, and the electrolytic solution enters the gap.

A normal portion where the distance between the positive electrode mixture layer and the negative electrode mixture layer is normal is located around the separated portion.

Assume that the secondary battery 2B including the electrode body 11B as described above is incorporated in the power storage device 1C and is repeatedly charged and discharged.

At this time, since the electrical resistance of the spaced portion is high, the current is difficult to flow in the spaced portion, while the current concentrates in the normal portions located around the spaced portion. Therefore, in the normal portion located around the spaced portion, the negative electrode mixture layer may not be able to accept lithium ions, and lithium may be deposited.

In particular, since the electrolytic solution enters the spaced portion, many lithium ions are present around the normal portion located around the spaced portion, and the lithium ions are likely to be deposited in the normal portion.

In addition, when lithium deposits in the secondary battery 2B, lithium may deposit in a needle shape. As a result, needle-shaped lithium may penetrate through the separator 21 and short-circuit the positive electrode mixture layer and the negative electrode mixture layer.

On the other hand, according to the method for reusing secondary battery 2 according to the present embodiment, formation of gaps in electrode body 11 is suppressed in secondary battery 2 incorporated in power storage device 1A. Therefore, the occurrence of adverse effects such as those in the comparative example is suppressed.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, and is intended to include all changes within the meaning and range of equivalents to the claims.

Reference Signs List 1, 1A, 1B, 1C power storage device, 2, 2B secondary battery, 3, 3C restraint, 4 bus bar, 10 housing case, 11, 11B electrode assembly, 12 positive electrode terminal, 13 negative electrode terminal, 14 electrolyte solution, 15 case Main body 16 lid 17A, 17B main surface 18A, 18B side surface 19A upper surface 19B bottom surface 20 positive electrode sheet 21 separator 22 negative electrode sheet 23 positive electrode 24 negative electrode 30, 31 end plate 32 restraint band 40 storage device, 41 restraint plate, 42 bolt, 43 nut, 44 head, 45 shaft, 46a, 46b, 46c, 46d through hole, D1, D2 arrangement direction, S1 preparation process, S2 separation process, S3A, S3 storage process, S4A , S4 release step, S5A, S5 assembly step, W width direction.

Claims (1)

providing a first power storage device including a plurality of constrained secondary batteries;
releasing the restrained state of the secondary battery;
applying pressure to the secondary battery released from the restrained state;
releasing the secondary battery from the pressure;
assembling the secondary battery released from the pressure to a second power storage device;
with
The secondary battery includes a housing case and an electrode body housed in the housing case,
The storage case includes a first main surface and a second main surface arranged in a first direction,
The step of applying pressure to the secondary battery released from the restraint includes a first restraint plate having a flat surface that presses the first main surface and a second restraint plate having a flat surface that presses the second main surface. A method for recycling a secondary battery , comprising the step of constraining the secondary battery with a constraining plate .

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