Lithium-ion batteries and their management methods

Abstract

This invention provides a lithium-ion battery suitable for long-term storage while keeping the size of the battery module, which is assembled from individual cells, to a minimum. [Solution] The lithium-ion battery comprises an electrode body, a case, a sealed bag, and an electrolyte. The electrode body includes a positive electrode, a negative electrode, and a separator. The case houses the electrode body. The sealed bag is placed inside the case. The sealed bag contains lithium salt. The electrolyte is filled inside the case. The electrolyte does not contain lithium salt. The sealed bag has the property of dissolving at a predetermined temperature or higher. The predetermined temperature is lower than the heat resistance temperature of the other components of the lithium-ion battery, excluding the sealed bag.

Description

Technical Field

[0001] The present disclosure relates to a lithium-ion battery and a method for managing the same.

Background Art

[0002] Patent Document 1 discloses a technique for performing a battery formation process in which, for the purpose of long-term storage of a lithium-ion battery, a plate group composed of a positive electrode, a negative electrode, and a separator and a non-aqueous electrolyte are separated and housed in separate spaces within a single cell, and the non-aqueous electrolyte is fed into the plate group when forming the battery. Specifically, in Patent Document 1, the periphery of the plate group constituting the single cell and the periphery of the non-aqueous electrolyte are each surrounded and sealed with a laminate film. The plate group and the non-aqueous electrolyte are arranged adjacent to each other, and the sealing strength of the laminate film at these boundary portions is weakened compared to the sealing strength of other portions. In the battery formation process, an external force is applied from above the laminate film covering the non-aqueous electrolyte, whereby the boundary portion with weak sealing strength opens and the non-aqueous electrolyte is fed into the plate group.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique of Patent Document 1, it is necessary to apply an external force to the laminate film covering the non-aqueous electrolyte in the battery formation process for all of the single cells. Therefore, when performing the battery formation process for each single cell, it takes time for the battery formation process. In this regard, the technique of Patent Document 1 includes an example in which a loading mechanism for performing the battery formation process for all single cells is incorporated for each single cell after assembling the battery module. However, in this example, since it is necessary to increase the size of the internal space of the single cell by the size of the loading mechanism, this leads to an increase in the size of the battery module.

[0005] One objective of this disclosure is to provide a lithium-ion battery suitable for long-term storage while keeping the size of the battery module small when the individual cells are assembled. Another objective of this disclosure is to provide a method for managing such lithium-ion batteries. [Means for solving the problem]

[0006] The first aspect of this disclosure is a lithium-ion battery, which has the following characteristics: The lithium-ion battery comprises an electrode body, a case, a sealed bag, and an electrolyte. The electrode body includes a positive electrode, a negative electrode, and a separator. The case houses the electrode body. The sealed bag is placed inside the case. The sealed bag contains lithium salt. The electrolyte is filled inside the case. The electrolyte does not contain lithium salt. The sealed bag has the property of melting at a predetermined temperature or higher. This predetermined temperature is lower than the heat resistance temperature of the other components of the lithium-ion battery, excluding the sealed bag.

[0007] The second aspect of this disclosure is a method for managing lithium-ion batteries, which has the following characteristics: The aforementioned management method includes: placing an electrode assembly including a positive electrode, a negative electrode, and a separator inside a case; placing a sealed bag containing a lithium salt inside the case in which the electrode assembly is placed; and injecting an electrolyte solution that does not contain a lithium salt into the case in which the electrode assembly and the sealed bag are placed and sealing it. The sealed bag has the property of melting at a predetermined temperature or higher. This predetermined temperature is lower than the heat resistance temperature of the other components of the lithium-ion battery, excluding the sealed bag. [Effects of the Invention]

[0008] According to this disclosure, it is possible to manage lithium-ion batteries in a separated state within the battery case, containing both the electrolyte and lithium salt. As long as this separated state is maintained, the lithium-ion battery will not function as a battery, thus enabling long-term storage. Furthermore, since the sealed bag containing the lithium salt has the property of dissolving at a predetermined temperature or higher, it is possible to assemble the battery by, for example, simultaneously heating all the individual cells after assembly into a battery module, and a load mechanism like that described in Patent Document 1 is not required. Therefore, it is possible to provide a lithium-ion battery suitable for long-term storage while keeping the size of the battery module down, and it is also possible to provide a method for managing such lithium-ion batteries. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the configuration of a lithium-ion battery according to the present disclosure. [Figure 2] This figure shows an example of the configuration of a lithium-ion battery after battery processing. [Figure 3] This figure shows an example of a method for managing a lithium-ion battery according to the present invention. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. However, structures and the like described in the embodiments below are not necessarily essential to this disclosure unless specifically stated or clearly defined in principle.

[0011] The lithium-ion battery according to this embodiment is installed in a vehicle that uses a battery as a power source, such as an electric vehicle. Figure 1 is a diagram showing an example of the configuration of the lithium-ion battery according to this embodiment. In the example shown in Figure 1, the lithium-ion battery 10 comprises a case 12, a lid 14, and a pair of negative terminals 16 and positive terminals 18. The case 12 has a rectangular parallelepiped shape. The lid 14 covers the opening of the case 12. Although not particularly limited, the case 12 and the lid 14 are made of metal. The negative terminals 16 and positive terminals 18 are electrically insulated from the case 12 and extend both inside and outside the case 12. The negative terminals 16 and positive terminals 18 are each made of a conductor such as metal.

[0012] An electrode assembly 20 is arranged inside the case 12. The electrode assembly 20 comprises a negative electrode, a positive electrode, and a separator. Each of the negative electrode, positive electrode, and separator is made of, for example, a long sheet material. The negative electrode, positive electrode, and separator are stacked in the order of negative electrode, separator, and positive electrode, and are wound around an axis at one end. The negative electrode is electrically connected to a negative electrode current collector terminal 22 inside the case 12, and this negative electrode current collector terminal 22 is electrically connected to a negative electrode terminal 16. The positive electrode is electrically connected to a positive electrode current collector terminal 24 inside the case 12, and this positive electrode current collector terminal 24 is electrically connected to a positive electrode terminal 18.

[0013] Case 12 is also filled with electrolyte 26. Electrolyte 26 is a solvent that does not contain lithium salts. Examples of solvents usable for electrolyte 26 include a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 30 / 40 / 30. Electrolyte 26 may contain additives. Examples of additives include lithium bisoxalate borate (LiBOB) or vinylene carbonate (VC). Any additive having a higher decomposition potential than fluoroethylene carbonate, such as vinylethylene carbonate (VEC), may also be included.

[0014] A sealed bag 28 is further placed inside case 12. The sealed bag 28 contains a lithium salt. Lithium hexafluoride phosphate (LiPF6) is an example of the lithium salt. In the example shown in Figure 1, the sealed bag 28 is placed above the electrode body 20 and between the negative electrode current collector terminal 22 and the positive electrode current collector terminal 24. However, the placement of the sealed bag 28 is not particularly limited and can be placed in any space within case 12.

[0015] The sealed bag 28 is made of a material that melts at a predetermined temperature (e.g., 50-60°C) or higher, and whose dissolved components do not adversely affect the electrolyte 26. Furthermore, the material used for the sealed bag 28 must melt at a temperature sufficiently lower than the heat resistance temperature of the other components of the lithium-ion battery 10 (e.g., rubber seal, insulating resin). Examples of such materials include polyvinyl alcohol (PVA), low-density polyethylene (LDPE), and other special synthetic resins.

[0016] The sealed bag 28 melts when the case is heated to a predetermined temperature or higher as described above during the battery formation process described later. Figure 2 shows an example of the configuration of a lithium-ion battery after the battery formation process. As the sealed bag 28 melts, the lithium salt is discharged to the outside of the sealed bag 28 and dissolves into the electrolyte 26. This allows the lithium-ion battery 10 to function as a battery. To improve the dispersibility of the lithium salt dissolved in the electrolyte 26, it is desirable to place the sealed bag 28 above the electrode body 20 and between the negative electrode current collector terminal 22 and the positive electrode current collector terminal 24. Furthermore, from the viewpoint of ease of placement of the sealed bag 28 during the manufacturing of the lithium-ion battery 10, it is desirable to place the sealed bag 28 in this position.

[0017] FIG. 3 is a diagram showing an example of a method for managing a lithium ion battery according to an embodiment. In the example shown in FIG. 3, the processing blocks are shown divided into a left region and a right region. The processing blocks in the left region show the processing performed in a clean room, and the processing blocks in the right region show the processing performed outside the clean room. The processing blocks in the left region mainly show the processing related to the manufacture of the lithium ion battery, and the processing blocks in the right region mainly show the processing related to the shipment of the lithium ion battery. Note that the storage of the lithium ion battery after manufacture and before shipment may be performed in a clean room or outside the clean room (a general warehouse). However, even when stored outside the clean room, temperature and humidity management of the lithium ion battery is performed.

[0018] In the example shown in FIG. 3, first, the lithium ion battery 10 is manufactured. Specifically, the electrode body 20 is inserted into the case 12, and subsequently, the sealed bag 28 of the lithium salt is inserted into the case 12. Then, after the case 12 is dried and humidity adjustment inside the case 12 is performed, the electrolytic solution 26 is injected into the case 12 and the lid 14 and the case 12 are welded. Thereby, the case 12 is sealed. The lithium ion battery 10 after case sealing is stored.

[0019] In the example shown in FIG. 3, when the lithium ion battery 10 is shipped, the case 12 is heated. This heating is performed as part of the battery formation process of the lithium ion battery 10. The heating temperature is, for example, a temperature not less than the predetermined temperature described above and less than the heat resistance temperature of other components of the lithium ion battery 10. The heating time is appropriately set according to the size of the single cell or battery module and the heating temperature. After heating, first charging and activation are performed. First charging and activation are general processes in the battery formation process. After passing through the battery formation process, shipment is performed.

[0020] According to the embodiment described above, it is possible to manage the electrolyte 26 and lithium salt in a separated state within the case 12. Therefore, as long as this separated state is maintained, the lithium-ion battery will not function as a battery, and thus long-term storage is possible. Furthermore, since the sealed bag 28 containing the lithium salt has the characteristic of dissolving at a predetermined temperature or higher, it is possible to create a battery by, for example, heating all the individual cells simultaneously after the battery module has been assembled, and a load mechanism such as that described in Patent Document 1 is not required. Thus, it is possible to provide a lithium-ion battery suitable for long-term storage while suppressing the increase in size of the battery module, and it is also possible to provide a method for managing such a lithium-ion battery. [Explanation of symbols]

[0021] 10...Lithium-ion battery, 12...Case, 14...Lid, 16...Negative terminal, 18...Positive terminal, 20...Electrode body, 22...Negative current collector terminal, 24...Positive current collector terminal, 26...Electrolyte, 28...Lithium salt sealed bag

Claims

1. An electrode body including a positive electrode, a negative electrode, and a separator, A case for housing the electrode body, A sealed bag containing lithium salt is placed inside the aforementioned case, The case is filled with an electrolyte that does not contain lithium salts, Equipped with, The aforementioned sealed bag has the property of melting at a predetermined temperature or higher. The predetermined temperature is lower than the heat resistance temperature of the other components of the lithium-ion battery, excluding the sealed bag. A lithium-ion battery characterized by the following features.

2. A lithium-ion battery according to claim 1, A positive electrode current collector terminal electrically connected to the positive electrode, A negative electrode current collector terminal electrically connected to the negative electrode, Furthermore, The sealed bag is positioned above the electrode body and between the positive electrode current collector terminal and the negative electrode current collector terminal. A lithium-ion battery characterized by the following features.

3. A lithium-ion battery according to claim 1 or 2, The predetermined temperature includes a temperature range of 50 to 60 degrees Celsius. A lithium-ion battery characterized by the following features.

4. The electrode assembly, including the positive electrode, negative electrode, and separator, is placed inside the case. A sealed bag containing a lithium salt is placed inside the case in which the electrode body is arranged. The electrolyte solution, which does not contain lithium salt, is injected into the case in which the electrode body and the sealed bag are arranged and then sealed. Includes, The aforementioned sealed bag has the property of melting at a predetermined temperature or higher. The predetermined temperature is lower than the heat resistance temperature of the other components of the lithium-ion battery, excluding the sealed bag. A method for managing lithium-ion batteries, characterized by the following features.

5. A method for managing a lithium-ion battery according to claim 4, The process further includes heating the case for the purpose of battery formation, The heating temperature of the case is above the predetermined temperature and lower than the heat resistance temperature of the other components. A method for managing lithium-ion batteries, characterized by the following features.

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