JP2019192426A - Screening method of reusable nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a method capable of screening a nonaqueous electrolyte secondary battery more excellent in performance.SOLUTION: A screening method of a reusable nonaqueous electrolyte secondary battery includes a measurement step of measuring a resistance increase rate for the resistance of a provided nonaqueous electrolyte secondary battery in the initial state, a determination step of determining the temperature and time for preserving the nonaqueous electrolyte secondary battery on the basis of the measured resistance increase rate, a preservation step of preserving the nonaqueous electrolyte secondary battery for the determined time under the determined temperature conditions, and a determination step of determining whether or not reusable on the basis of the values of the I/O characteristics of the nonaqueous electrolyte secondary battery after the preservation step.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for selecting a reusable non-aqueous electrolyte secondary battery from used non-aqueous electrolyte secondary batteries.

  In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have been used as so-called portable power sources such as personal computers and portable terminals and power sources for driving vehicles. When a non-aqueous electrolyte secondary battery is used as a power source for driving a vehicle, a plurality of non-aqueous electrolyte secondary batteries (single cells) are used in the form of an assembled battery that is electrically connected. The demand for non-aqueous electrolyte secondary batteries is increasing year by year.

  Here, the non-aqueous electrolyte secondary battery that has been used (charged / discharged) a predetermined number of times needs to be replaced. However, as the demand for non-aqueous electrolyte secondary batteries increases, A large amount of secondary batteries are expected to be generated. Therefore, whether the non-aqueous electrolyte secondary battery can be reused by detecting the deterioration state of the used non-aqueous electrolyte secondary battery from the viewpoint of efficient use of resources and saving of running costs. A method for determining whether or not is used. For example, in Patent Document 1, a used nonaqueous electrolyte secondary battery is stored for a predetermined time under high temperature conditions (for example, 40 ° C. to 75 ° C.), and the internal resistance of the nonaqueous electrolyte secondary battery after storage is stored. A technique for determining whether or not it can be reused based on the above is disclosed.

Japanese Patent Laid-Open No. 2017-50115

  In the screening method disclosed in Patent Document 1, the non-aqueous electrolyte secondary battery is stored for a predetermined time in a thermostat set at a predetermined temperature. It has been found that there is an optimum storage temperature and an optimum storage time depending on the resistance increase rate with respect to the initial resistance of the liquid secondary battery. That is, it has been found that when the resistance increase rate is relatively large, the storage time tends to be long, and when the resistance increase rate is relatively small, the storage time tends to be short. Further, it has been found that when the storage temperature is relatively high, the storage time tends to be short, and when the storage temperature is relatively low, the storage time tends to be long. Here, when the storage temperature is high, the material used for the battery may deteriorate. The screening method described in Patent Document 1 can also appropriately select whether or not the non-aqueous electrolyte secondary battery can be reused. However, the screening method for the non-aqueous electrolyte secondary battery having better performance Establishment is required.

  This invention is made | formed in view of this point, The objective is to provide the method which can select the nonaqueous electrolyte secondary battery which was excellent in the performance.

  The reusable nonaqueous electrolyte secondary battery sorting method according to the present invention includes a preparation step of preparing a used nonaqueous electrolyte secondary battery having a positive electrode and a negative electrode, and the prepared nonaqueous electrolyte secondary battery. A measurement step of measuring a resistance increase rate with respect to the initial resistance of the battery; a determination step of determining a temperature and a time for storing the non-aqueous electrolyte secondary battery based on the measured resistance increase rate; A storage step of storing the non-aqueous electrolyte secondary battery for the determined time under the temperature condition and a value of input / output characteristics of the non-aqueous electrolyte secondary battery after the storage step And a determination step of determining whether or not it can be reused.

  According to the screening method according to the present invention, the non-aqueous electrolyte secondary battery is stored for the storage temperature and storage time determined based on the resistance increase rate of the used non-aqueous electrolyte secondary battery. Compared with storing non-aqueous electrolyte secondary batteries depending on storage temperature and storage time, while suppressing the decrease in capacity, the value of input / output characteristics due to uneven salt concentration in the electrode body and liquid drainage are reduced. You can recover better. Thereby, the nonaqueous electrolyte secondary battery with more excellent performance can be selected.

It is sectional drawing which shows typically the internal structure of the reusable lithium ion secondary battery sorted out in one Embodiment. It is a flowchart which shows the flow of the selection method of the reusable lithium ion secondary battery which concerns on one Embodiment. It is a table which shows the relationship between the resistance increase rate which concerns on one Embodiment, storage temperature, and storage time. It is the graph which showed the relationship between the resistance increase rate in the predetermined | prescribed temperature which concerns on one Embodiment, and storage time. It is the graph which showed the relationship between the resistance increase rate in several temperature and storage time which concern on one Embodiment. It is the graph which showed the relationship between the capacity | capacitance maintenance factor in the some temperature and storage time which concern on one Embodiment. It is a table which shows the relationship between the resistance increase rate which concerns on one Embodiment, storage temperature, storage time, and a capacity | capacitance maintenance factor.

  Hereinafter, a method for selecting a reusable nonaqueous electrolyte secondary battery disclosed herein will be described in detail with reference to the drawings with specific embodiments. The embodiments described herein are, of course, not intended to limit the present invention in particular. Further, matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters for those skilled in the art based on the prior art in this field.

  In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a power storage element such as a so-called storage battery and an electric double layer capacitor. Further, in the present specification, the “lithium ion secondary battery” refers to a secondary battery that uses lithium ions as a charge carrier and is charged / discharged by movement of charges accompanying the lithium ions between the positive and negative electrodes.

  First, the structure of a nonaqueous electrolyte secondary battery (here, a lithium ion secondary battery) 10 applied to the selection method of the present embodiment will be briefly described with reference to FIG. In this embodiment, a rectangular lithium ion secondary battery having a wound electrode body is taken as an example, but the present invention is not limited to this. For example, a stacked electrode body in which a plurality of negative electrodes, a plurality of separators, and a plurality of positive electrodes are stacked may be used, or a cylindrical nonaqueous electrolyte secondary battery may be used.

  A lithium ion secondary battery 10 shown in FIG. 1 includes a rectangular battery case 30, a flat wound electrode body 20 accommodated in the battery case 30, and a non-aqueous electrolyte (not shown). The battery case 30 includes a box-shaped case main body 32 having an opening at one end, and a lid 34 that seals the opening of the case main body 32. As a material of the battery case 30, for example, a light metal material having a good thermal conductivity such as aluminum, stainless steel, or nickel-plated steel can be preferably used.

  As shown in FIG. 1, the lid 34 is provided with a positive terminal 42 and a negative terminal 44 for external connection, a safety valve 36, and an inlet (not shown) for injecting a non-aqueous electrolyte. . The safety valve 36 is set to release the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level.

  As shown in FIG. 1, the wound electrode body 20 includes a long positive electrode current collector 52 and a positive electrode 50 having a positive electrode active material layer 54 formed on the positive electrode current collector 52, and a long negative electrode. A laminate in which a current collector 62 and a negative electrode 60 having a negative electrode active material layer 64 formed on the negative electrode current collector 62 are stacked via two long separators 70 is wound in the longitudinal direction. And has a shape formed into a flat shape. A positive electrode current collector plate 42 a connected to the positive electrode terminal 42 is electrically connected to the positive electrode current collector 52. A negative electrode current collector plate 44 a connected to the negative electrode terminal 44 is electrically connected to the negative electrode current collector 62.

  As the positive electrode active material included in the positive electrode active material layer 54, it is preferable to use an oxide-based active material having a layered structure, an oxide-based active material having a spinel structure, or the like used for a positive electrode of a general lithium ion secondary battery. it can. Typical examples of such active materials include lithium transition metal oxides such as lithium cobalt oxides, lithium nickel oxides, and lithium manganese oxides.

  In addition to the above-described positive electrode active material, the positive electrode active material layer 54 may contain further optional components as necessary. Examples of the optional component include a binder, a conductive aid, a thickener, a dispersant, and a pH adjuster. Examples of the binder include a vinyl halide resin such as polyvinylidene fluoride (PVdF) and a polyalkylene oxide such as polyethylene oxide (PEO). Examples of the conductive assistant include carbon materials such as carbon black (typically acetylene black), activated carbon, graphite, and carbon fiber. Examples of the pH adjuster include acidic substances such as phosphoric acid.

  Examples of the negative electrode active material contained in the negative electrode active material layer 64 include carbon materials such as graphite (graphite), non-graphitizable carbon (hard carbon), and graphitizable carbon (soft carbon).

  In addition to the above-described negative electrode active material, the negative electrode active material layer 64 may contain further optional components as necessary. Examples of the optional component include a binder, a thickener, and a dispersant. Examples of the binder include rubbers such as styrene butadiene rubber (SBR). Examples of the dispersant include celluloses such as carboxymethyl cellulose (CMC).

  As the separator 70, for example, a porous sheet made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, polyamide, or a non-woven fabric can be used.

The non-aqueous electrolyte contained in the battery case 30 contains a supporting salt in a suitable non-aqueous solvent, and conventionally known non-aqueous electrolytes for lithium ion secondary battery applications are used without particular limitation. be able to. For example, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or the like can be used as the non-aqueous solvent. As the supporting salt, for example, a lithium salt such as LiPF ₆ can be suitably used. The nonaqueous electrolytic solution is present in the wound electrode body 20. The nonaqueous electrolytic solution is interposed between the positive electrode 50 and the negative electrode 60.

  Next, a procedure for selecting the reusable lithium ion secondary battery 10 will be described with reference to a flowchart. FIG. 2 is a flowchart according to an embodiment. A screening method for a reusable non-aqueous electrolyte secondary battery (here, lithium ion secondary battery 10) includes a preparation process, a measurement process, a determination process, a storage process, and a determination process. Hereinafter, each process is explained in full detail.

  First, in step S10, a used lithium ion secondary battery 10 including a wound electrode body 20 having a positive electrode 50 and a negative electrode 60 is prepared. For example, the lithium ion secondary battery 10 used as a portable power source, a vehicle driving power source, or the like is collected. The collected lithium ion secondary battery 10 can be used in the sorting method of the present embodiment in the form of an assembled battery or a single battery, but the collected lithium ion secondary battery 10 is accurately sorted and reused. From the viewpoint, it is preferably used for the sorting method of the present embodiment in the form of a unit cell. Step S10 of the present embodiment is an example of a preparation process.

  Next, in step S20, the resistance increase rate R with respect to the initial resistance of the prepared lithium ion secondary battery 10 is measured. Here, the resistance increase rate R is a ratio R1 / R0 between the initial resistance R0, which is the initial resistance of the lithium ion secondary battery 10, and the post-recovery resistance R1 of the lithium ion secondary battery 10 whose resistance has been increased by use. It is represented by The initial resistance R0 is measured and stored when the lithium ion secondary battery 10 is manufactured. The post-recovery resistance R1 is measured and stored in the prepared lithium ion secondary battery 10. The initial resistance R0 and the post-recovery resistance R1 can be measured by selecting a specific method from among known methods for measuring the resistance (for example, internal resistance) of the lithium ion secondary battery 10. Step S20 of the present embodiment is an example of a measurement process.

  Next, in step S30, based on the measured resistance increase rate R, the temperature (that is, storage temperature A) and time (that is, storage time B) for storing the prepared lithium ion secondary battery 10 are determined. Specifically, the storage temperature A and the storage time B are determined based on the measured resistance increase rate R and the table A (see FIG. 3). Table A stores the relationship between the resistance increase rate R and the storage temperature A and storage time B. As shown in FIG. 3, for example, when the resistance increase rate R is 1.03 in the table A, the storage temperature A is 60 ° C. and the storage time B is 35 hours, or the storage temperature A is 25 ° C. In addition, it is recorded that the storage time B is 136 hours. For example, in Table A, when the resistance increase rate R is 1.05, after the storage temperature A is 60 ° C. and the storage time B is 10 hours, the storage temperature A is 40 ° C. and the storage time B is 20 Time is recorded. For example, in Table A, when the resistance increase rate R is 1.07, after the storage temperature A is 60 ° C. and the storage time B is 10 hours, the storage temperature A is 40 ° C. and the storage time B is 30. Time is recorded. Further, for example, when the resistance increase rate R is 1.1 in Table A, after the storage temperature A is set to 60 ° C. and the storage time B is set to 15 hours, the storage temperature A is set to 40 ° C. and the storage time B is set to 60 Time is recorded. Note that the table A shown in FIG. 3 is merely an example, and actually, the above relationship is recorded in increments of 0.1 when the value of the resistance increase rate R is within a range of, for example, 1.01 to 1.2. . Step S30 of the present embodiment is an example of a determination process.

  The table A is created based on FIGS. 4 to 7 described below, for example. FIG. 4 is a graph showing the relationship between the resistance increase rate R and the storage time B at a predetermined temperature. The example shown in FIG. 4 represents the transition of the resistance increase rate R when discharged for 10 seconds at a predetermined storage time B, 25 ° C., SOC 60%, 200 A. As shown in FIG. 4, when the storage temperature A is constant, the larger the resistance increase rate R, the longer the storage time B required for the resistance to decrease. FIG. 5 is a graph showing the relationship between the resistance increase rate R and the storage time B at a plurality of temperatures. The example shown in FIG. 5 represents the transition of the resistance increase rate R when discharged for 10 seconds at an SOC of 60% and 200 A at a predetermined storage time B, 25 ° C., 40 ° C., and 60 ° C. As shown in FIG. 5, the higher the storage temperature A, the shorter the storage time B required for the resistance to decrease. FIG. 6 is a graph showing the relationship between the capacity retention rate D and the storage time B at a plurality of temperatures. Here, the capacity retention rate D [%] is the discharge capacity D1 after a predetermined discharge treatment with respect to the initial capacity D0 of the prepared lithium ion secondary battery 10 (that is, the recovered lithium ion secondary battery 10). It is represented by a ratio {(D1 / D0) × 100}. The example shown in FIG. 6 represents the transition of the capacity retention ratio D when discharged at a SOC of 60% and 200 A for 10 seconds in the temperature range of 25 ° C., 40 ° C. and 60 ° C. As shown in FIG. 6, the capacity maintenance rate D decreases as the storage temperature A increases. FIG. 7 is a table showing the relationship between the resistance increase rate R, the storage temperature A, the storage time B, and the capacity maintenance rate D. The table shown in FIG. 7 is created based on the graphs shown in FIGS. The table shown in FIG. 7 shows the relationship between the storage temperature A and the storage time B necessary to make the lithium ion secondary battery 10 reusable. For example, when the resistance increase rate R is 1.03, the storage temperature A is set to 60 ° C. and the storage time B is set to 35 hours, whereby the lithium ion secondary battery 10 can be recovered to a reusable state. . Based on the table shown in FIG. 7, the table A includes, for example, combinations in which the capacity maintenance rate D is 99.5% or more and the storage time B is within 168 hours (one week). In addition, the threshold value of the capacity maintenance rate D and the threshold value of the storage time B in the table A are not limited to those described above and can be set as appropriate.

  Next, in step S40, the lithium ion secondary battery 10 is stored for the determined time under the determined temperature condition. According to the study of the present inventor, when the lithium ion secondary battery 10 in which the salt concentration unevenness or the liquid withering occurred is stored under the condition determined in step S30, the wound electrode body is caused by the decrease in the viscosity of the electrolytic solution or convection. It was found that at least a part of the salt concentration unevenness and liquid withering produced within 20 can be recovered. Therefore, it is possible to reduce the resistance (for example, internal resistance) of the lithium ion secondary battery 10 that has increased due to uneven salt concentration or withered liquid. For example, when storing the lithium ion secondary battery 10, a known storage device such as a thermostatic bath can be used. For example, when the resistance increase rate R of the lithium ion secondary battery 10 is 1.1, the lithium ion secondary battery 10 is stored at 60 ° C. for 15 hours based on the table A shown in FIG. Store for 60 hours. Step S40 of the present embodiment is an example of a storage process.

  Next, in step S50, it is determined whether or not it can be reused based on the value of the input / output characteristics of the lithium ion secondary battery 10 after the storage process. The value of the input / output characteristic of the lithium ion secondary battery 10 can be defined as a resistance value, for example. As the resistance value, it is possible to adopt a resistance value obtained by adjusting to a predetermined SOC at a predetermined temperature and discharging with a constant current at a predetermined current value for a predetermined time. Here, “SOC” is an abbreviation for “State of Charge” and means the state of charge of the lithium ion secondary battery 10. The SOC can be indicated by a value indicating the state of charge of the lithium ion secondary battery 10. Here, the state of charge at a predetermined lower limit voltage is SOC 0%, the state of charge at the upper limit voltage is SOC 100%, and the lithium ion secondary battery 10 charged from the lower limit voltage to the upper limit voltage is charged. It is shown as a value shown in 100% based on the amount.

  If the value of the input / output characteristic is equal to or greater than the predetermined threshold value, the process proceeds to step S60. On the other hand, if the value of the input / output characteristic is less than the predetermined threshold value, the process proceeds to step S70. The predetermined threshold value determined in advance is a value that is appropriately determined from the viewpoint of whether or not the lithium ion secondary battery 10 can be reused. Step S50 of the present embodiment is an example of a determination process.

  In step S60, since the lithium ion secondary battery 10 has a predetermined input / output characteristic value, it can be reused. That is, the lithium ion secondary battery 10 is conveyed to a reuse process, for example. Since the lithium ion secondary battery 10 determined to be reusable by the screening method of the present embodiment is stored at the optimized storage temperature A and storage time B, it has better performance (resistance is reduced). E) The lithium ion secondary battery 10 can be obtained.

  In step S70, since the lithium ion secondary battery 10 does not have a predetermined input / output characteristic value, it cannot be reused. That is, the lithium ion secondary battery 10 is discarded, for example, because it is not suitable for reuse.

  In addition, the lithium ion secondary battery 10 determined to be reusable by the screening method of the present invention can be reused for various applications. For example, if it is a lithium ion secondary battery that has been used for vehicles, it is preferably used for driving mounted on vehicles such as plug-in hybrid vehicles (PHV), hybrid vehicles (HV), and electric vehicles (EV). It can be reused as a power source.

  As mentioned above, although the selection method proposed here was variously demonstrated, unless it mentions especially, embodiment and the example which were mentioned here do not limit this invention.

  In the table A described above, the storage temperature A is 25 ° C., 40 ° C., and 60 ° C., but is not limited to this. The storage temperature A can be set to an arbitrary temperature. Further, the storage temperature A has three types, but may be four or more types.

  The threshold value set in step S50 of the above-described flowchart may be one or plural. When a plurality of threshold values are set, the method of reusing the lithium ion secondary battery 10 may be divided according to the degree of recovery of the deterioration of the performance of the lithium ion secondary battery 10.

10 Lithium ion secondary battery (non-aqueous electrolyte secondary battery)
20 Winding electrode body 30 Battery case 32 Case body 34 Lid 36 Safety valve 42 Positive electrode terminal 44 Negative electrode terminal 50 Positive electrode 52 Positive electrode current collector 54 Positive electrode active material layer 60 Negative electrode 62 Negative electrode current collector 64 Negative electrode active material layer 70 Separator

Claims (1)

Preparing a used non-aqueous electrolyte secondary battery including an electrode body having a positive electrode and a negative electrode;
A measuring step of measuring a resistance increase rate with respect to an initial resistance of the prepared nonaqueous electrolyte secondary battery;
A determination step of determining a temperature and a time for storing the non-aqueous electrolyte secondary battery based on the measured resistance increase rate;
A storage step of storing the non-aqueous electrolyte secondary battery for the determined time under the determined temperature condition;
A reusable nonaqueous electrolyte secondary battery comprising: a determination step of determining whether or not the reusable battery can be reused based on the input / output characteristic value of the nonaqueous electrolyte secondary battery after the storage step Sorting method.

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