WO2018173360A1 - Method for charging non-aqueous secondary cell - Google Patents

Abstract

Provided is a method for charging a non-aqueous secondary cell in which the charging time is reduced and degradation is suppressed. A value corresponding to the thickness of a non-aqueous secondary cell 2 is detected by a detection sensor 5, and the cell 2 is subjected to constant-current charging with a predetermined high current until the value ΔT corresponding to the thickness reaches a first prescribed value ΔT1.

Description

Non-aqueous secondary battery charging method

The present disclosure relates to a method for charging a non-aqueous secondary battery, a charging device, and a charging program.

In recent years, sealed secondary batteries having a non-aqueous electrolyte typified by lithium ion secondary batteries (hereinafter sometimes simply referred to as “non-aqueous secondary batteries”) are only mobile devices such as mobile phones and laptop computers. It is also used as a power source for electric vehicles such as electric vehicles and hybrid vehicles.

In non-aqueous secondary batteries, in particular, electric vehicle applications, there is an increasing need for rapid charging that charges a battery in a short time without promoting battery deterioration. As a general charging method for a non-aqueous secondary battery, a constant current constant voltage (CCCV; Constant Current Constant Voltage) method is known. In the constant current constant voltage method, constant current charging is performed in which a constant current is supplied to the battery until the voltage reaches a predetermined value. After the voltage reaches a predetermined value in constant current charging, the voltage reaches a predetermined value. Switch to constant voltage charging to control the current to maintain. In constant voltage charging, the charging current gradually decreases as the internal voltage of the battery increases.

In Patent Document 1, in the constant current constant voltage method, the remaining capacity of the battery is detected before starting charging, and when the remaining capacity is smaller than a certain value, the voltage setting value in constant current charging is further set. It is described to switch to a higher value. However, in this method, since the voltage setting value is increased, the charging period with a relatively large constant current is lengthened and the charging time can be shortened. However, there is a possibility that the battery deterioration may be caused by increasing the voltage setting value. is there.

In Patent Document 2, overcharge is suppressed by calculating the internal resistance of the battery from the temperature during charging and the value of the current, and adding the voltage drop due to the current to the voltage value used as the constant current charging termination condition. However, it is described that rapid charging is realized. However, in a battery that is being rapidly charged, a charge distribution is generated in the active material in the electrode, and there are active materials having different charge amounts even in the same electrode. Only the average value of the active material can be obtained from the battery terminal. That is, in this method, information on the active material that is most charged in the electrode cannot be obtained, and it is difficult to say that overcharge to the active material can be suppressed.

Patent Document 3 describes that pulse charging is performed after constant current charging. However, since on / off switching of pulse charging is controlled by voltage or time, it is difficult to say that both rapid charging and deterioration suppression are compatible.

Japanese Unexamined Patent Publication No. 6-78471 JP 2008-253129 A JP-A-6-113474

The present disclosure has been made paying attention to such circumstances, and an object thereof is to provide a method for charging a non-aqueous secondary battery that suppresses deterioration and reduces charging time.

This disclosure takes the following measures in order to achieve the above object.

The nonaqueous secondary battery charging method of the present disclosure detects a value corresponding to the thickness of the battery with a detection sensor, and has a predetermined size until the value corresponding to the thickness becomes the first set value. The battery is charged with a constant current with a current.

In this manner, constant current charging is performed with a predetermined current until the value corresponding to the thickness of the battery reaches the first set value, so that a predetermined large current compared to constant current constant voltage charging. Charging can be continued for a long time, and the charging time can be reduced. In addition, since the value corresponding to the thickness of the battery is referred to, the charging depth of the active material that is most charged can be considered, and deterioration of the battery can be suppressed.

The block diagram which shows an example of the system by which a secondary battery is mounted. FIG. 3 is a perspective view schematically showing a sealed secondary battery. FIG. 2B is a sectional view taken along line AA in FIG. 2A. The block diagram which shows the charging system of this indication. The flowchart which shows the conventional charging method. 6 is a flowchart illustrating a charging method according to the first embodiment of the present disclosure. 9 is a flowchart illustrating a charging method according to a second embodiment of the present disclosure. 10 is a flowchart illustrating a charging method according to a third embodiment of the present disclosure. 10 is a flowchart illustrating a charging method according to a fourth embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described.

FIG. 1 shows a system mounted on an electric vehicle such as an electric vehicle or a hybrid vehicle. This system includes a battery module 1 in which an assembled battery composed of a plurality of sealed secondary batteries 2 is housed in a casing. In the present embodiment, four secondary batteries 2 are connected in two parallel two series, but the number of batteries and the connection form are not limited to this. Although only one battery module 1 is shown in FIG. 1, the battery pack 1 actually includes a plurality of battery modules 1. In the battery pack, a plurality of battery modules 1 are connected in series, and they are housed in a casing together with various devices such as a controller. The casing of the battery pack is formed in a shape suitable for in-vehicle use, for example, a shape that matches the underfloor shape of the vehicle.

The secondary battery 2 shown in FIG. 2 is configured as a cell (single cell) in which an electrode group 22 is accommodated in a sealed outer casing 21. The electrode group 22 has a structure in which a positive electrode 23 and a negative electrode 24 are laminated or wound through a separator 25 therebetween, and the separator 25 holds an electrolytic solution. The secondary battery 2 of the present embodiment is a laminated battery using a laminated film such as an aluminum laminated foil as the outer package 21, and is specifically a laminated lithium ion secondary battery having a capacity of 1.44 Ah. The secondary battery 2 is formed in a thin rectangular parallelepiped shape as a whole, and the X, Y, and Z directions correspond to the length direction, the width direction, and the thickness direction of the secondary battery 2, respectively. The Z direction is also the thickness direction of the positive electrode 23 and the negative electrode 24.

The secondary battery 2 is provided with a detection sensor 5 that detects deformation of the secondary battery 2. The detection sensor 5 includes a polymer matrix layer 3 attached to the secondary battery 2 and a detection unit 4. The polymer matrix layer 3 contains a filler that disperses the external field according to deformation of the polymer matrix layer 3 in a dispersed manner. The polymer matrix layer 3 of the present embodiment is formed in a sheet shape from an elastomer material that can be flexibly deformed. The detector 4 detects a change in the external field. When the secondary battery 2 swells and deforms, the polymer matrix layer 3 is deformed accordingly, and a change in the external field accompanying the deformation of the polymer matrix layer 3 is detected by the detection unit 4. In this way, deformation of the secondary battery 2 can be detected with high sensitivity.

In the example of FIG. 2, since the polymer matrix layer 3 is attached to the outer package 21 of the secondary battery 2, the polymer matrix layer 3 can be deformed according to deformation (mainly swelling) of the outer package 21. it can. On the other hand, the polymer matrix layer 3 may be affixed to the electrode group 22 of the secondary battery 2. According to such a configuration, the polymer matrix layer 3 is deformed in accordance with deformation (mainly swelling) of the electrode group 22. be able to. The deformation of the secondary battery 2 to be detected may be any deformation of the outer package 21 and the electrode group 22.

The signal detected by the detection sensor 5 is transmitted to the control device 6, whereby information relating to the deformation of the secondary battery 2 is supplied to the control device 6.

<Charging system>
When charging the non-aqueous secondary battery 2, a charging system shown in FIG. 3 is used. The system includes a detection sensor 5 that detects a value corresponding to the thickness of the battery, and a charging device 8 that supplies current to the secondary battery 2 based on the detection result of the detection sensor 5.

The detection sensor 5 detects a value corresponding to the thickness of the battery. In the present embodiment, the detection sensor 5 is a sensor that detects deformation of the battery. Since the battery swells by charging and contracts by discharging, the thickness of the battery can be known by detecting the amount of deformation of the battery. In the present embodiment, the amount of change in battery thickness from the discharged state is detected as a value corresponding to the thickness of the battery. The change in thickness of the battery can be detected by the amount of deformation of the polymer matrix layer 3 attached to the battery.

In addition, a displacement sensor, a pressure sensor, etc. are mentioned as a sensor for detecting the thickness of a battery. Examples of the displacement sensor system include a contact type, an optical type, an eddy current type, and an ultrasonic type.

Next, a method for charging a non-aqueous secondary battery will be described. As a result of the study by the present inventors, the following has been found. The charging method of the present disclosure uses the following examination results.

1) A non-aqueous secondary battery is configured by disposing a positive electrode 23 and a negative electrode 24, on which active material particles are fixed on a metal current collector, separated by a porous membrane (separator 25) and impregnating with an electrolyte. ing. During rapid charging, the ion conduction path and the electron conduction path are different in each active material in the same electrode. Therefore, when charging with a large current used for rapid charging, the individual active materials are not reacted at the same charging rate, and the charge distribution is expanded. The expansion of the charge distribution means that active materials having different charge depths at the same time coexist in the same electrode. The voltage information obtained from the battery terminals connected to the metal current collector is information on the average voltage of all active materials, and it is difficult to grasp the state of each active material. The deterioration of the battery in rapid charging is caused by the fact that the part where the charging progresses fastest among the individual active materials is in an overcharged state in which the charging is performed more than the assumed charging state, so This is caused by reaction or precipitation of lithium metal. In other words, it is necessary to control the charging speed so that the active material having the fastest charging speed does not reach the charging depth causing battery deterioration during the rapid charging in which the charging distribution occurs.

2) Non-aqueous secondary batteries are charged and discharged by occluding or releasing ions in battery active materials such as graphite and silicon. In the case of a negative electrode active material, it is charged by occluding ions and discharged by discharging. And by occluding ions, the active material expands, and the expansion of the active material changes the thickness of the battery element.

3) When charging is performed at a low current that does not cause charge distribution in each active material in the electrode, the change in battery thickness according to the charge capacity is indicated. However, the present inventors have found that when charging is performed with a large current that causes a charge distribution, the change in battery thickness indicates the change in battery thickness according to the charge capacity of the active material with the fastest charging speed. It was.

4) In the case of a non-aqueous secondary battery, since the electrolytic solution is an organic solvent, the ionic resistance is several orders of magnitude greater than the electronic resistance, and the ion supply rate greatly affects the charge rate of the active material. That is, the charge rate on the surface of the active material particles, where ions are easily supplied, is increased, and conversely, the charge rate at the center is decreased. Since the expansion of the surface holding the shape of the active material particles affects the macroscopic size of the active material particles, the charging depth of the surface of the active material particles having the fastest reaction rate is reflected in the thickness of the battery.

5) As described above, the cause of deterioration during rapid charging is a side reaction caused by overcharging in the active material region where charge distribution occurs during high current charging and the charging speed is the fastest. Therefore, by monitoring the thickness of the battery, it is possible to grasp the charging depth of the active material having the fastest charging speed, and if the current is stopped or reduced when the battery thickness reaches the predetermined thickness, the battery deterioration is prevented. Can be suppressed.

6) Moreover, the charge distribution formed at the time of quick charge is eased by stopping the charge. At that time, the battery thickness shrinks to a thickness corresponding to the charge capacity. This indicates that the charge distribution is canceled by the diffusion of electrons and ions by stopping the charge. That is, the relaxation time for eliminating the charge distribution is closely related to the diffusion rate of electrons and ions. The charge distribution is formed by charging at a rate higher than the diffusion rate of ions and electrons. In other words, in principle, the fastest charging speed is that charging is performed at the same speed as the diffusion speed of ions and electrons.

7) As described above, controlling the charging current so as to keep the thickness of the battery constant means charging at the same rate as the diffusion rate of ions and electrons, so in principle at the fastest charging rate. Can be charged.

In order to specifically show the charging method and effects of the present disclosure, the following evaluations were performed on the following examples.

<Battery>
Commercially available consumer lithium-ion batteries (3.0V to 4.3V rated capacity 1440 mAh) having the same voltage and rated capacity were prepared. The detection sensor 5 was affixed to this battery at the position shown in FIGS. 2A and 2B.

(1) Discharge capacity maintenance ratio The initial discharge capacity was measured, the discharge capacity after 500 cycles was measured, and the capacity maintenance ratio was calculated by the following formula.
Discharge capacity retention rate [%] = discharge capacity after 500 cycles / initial discharge capacity × 100
The discharge capacity was measured by constant-current / constant-voltage charging (finished at a current value of 72 mA) to 4.3 V with a current of 288 mA, and then discharging with a constant current to 3.0 V with a current of 288 mA. The discharge capacity at this time is employed.

Comparative Example 1
As shown in FIG. 4, constant current charging is performed until the battery voltage V reaches a threshold value V1 (4.3 V) with a current of a predetermined magnitude (4320 mA) (S1 to S3). After the battery voltage V reaches the threshold value V1 (S2: YES), the process proceeds to constant voltage charging (S4 to S7). In the constant voltage charging, the current value I is controlled so that the battery voltage V becomes the threshold value V1 (S4, S5). In the constant voltage charging, as the internal voltage of the battery increases, the current value to be controlled gradually decreases. Therefore, the charging is terminated when the charging current I decreases to the threshold value I1 (72 mA) (S6, S7).
After the completion of charging, the battery was discharged at a constant current of 288 mA to 3.0 V. Charging and discharging were repeated 500 times.

Comparative Example 2
The same charging as in Comparative Example 1 was performed. However, charging was terminated at a charging capacity of 1200 mAh.
After the completion of charging, the battery was discharged at a constant current of 288 mA to 3.0 V. Charging and discharging were repeated 500 times.

Example 1
As shown in FIG. 5, a value ΔT corresponding to the thickness of the battery 2 is detected by the detection sensor 5 (S11), and the value ΔT corresponding to the thickness of the battery becomes a first set value ΔT1 (70 μm) in advance. The battery 2 is charged with a constant current with a predetermined current (4320 mA) (S11 to S13). After the value ΔT corresponding to the battery thickness reaches the first set value ΔT1 (S12: YES), the charging is terminated.
After the completion of charging, the battery was discharged at a constant current of 288 mA to 3.0 V. Charging and discharging were repeated 500 times.

Example 2
As shown in FIG. 6, a value ΔT corresponding to the thickness of the battery 2 is detected by the detection sensor 5 (S21), and the value ΔT corresponding to the thickness of the battery becomes a first set value ΔT1 (70 μm) in advance. The battery 2 is charged with a constant current with a predetermined current (4320 mA) (S21 to S23). After the value ΔT corresponding to the battery thickness has reached the first set value ΔT1 (S22: YES), the process proceeds to constant voltage charging (S24 to S27). In the constant voltage charging, the current value I is controlled so that the battery voltage V becomes the threshold value V1 (4.3 V) (S24, S25). In the constant voltage charging, as the internal voltage of the battery increases, the current value to be controlled gradually decreases. Therefore, the charging is terminated when the charging current I decreases to the threshold value I1 (72 mA) (S26, S27).
After the completion of charging, the battery was discharged at a constant current of 288 mA to 3.0 V. Charging and discharging were repeated 500 times.

Example 3
As shown in FIG. 7, a value ΔT corresponding to the thickness of the battery 2 is detected by the detection sensor 5 (S31), and the value ΔT corresponding to the thickness of the battery becomes a first set value ΔT1 (70 μm) in advance. The battery 2 is charged with a constant current with a current having a predetermined magnitude (4320 mA) (S31 to S33). After the value ΔT corresponding to the thickness of the battery reaches the first set value ΔT1 (S32: YES), the charging proceeds to constant thickness charging (S34 to S37. In the constant thickness charging, the detection sensor 5 detects. The current value I is controlled so that the value ΔT corresponding to the thickness of the battery is maintained at the first set value ΔT1 (S34, S35) As charging progresses and the internal voltage of the battery increases, Since a certain current value I gradually decreases, charging is terminated when the charging current I decreases to the threshold value I1 (72 mA) (S36, S37).
After the completion of charging, the battery was discharged at a constant current of 288 mA to 3.0 V. Charging and discharging were repeated 500 times.

Example 4
As shown in FIG. 8, a value ΔT corresponding to the thickness of the battery 2 is detected by the detection sensor 5 (S42), and the value ΔT corresponding to the thickness of the battery becomes a first set value ΔT1 (70 μm) in advance. The battery 2 is charged with a constant current with a current having a predetermined magnitude (4320 mA) (S41 to S43). After the value ΔT corresponding to the battery thickness reaches the first set value ΔT1 (S43: YES), the process proceeds to on / off control (S41, S42, S43, S44, S47, S48). In the on / off control, the battery is set such that a value ΔT corresponding to the thickness exists between the first set value ΔT1 (70 μm) and the second set value ΔT2 (60 μm) lower than the first set value ΔT1. Turn on / off the supplied current. That is, when the value ΔT corresponding to the thickness is equal to or greater than the first set value ΔT1 (70 μm), the current is turned off (S43: YES, S44), and the value ΔT corresponding to the thickness is the second set value ΔT2 (60 μm). If the current falls below, the current is turned on (S48: YES, S41). The charging end condition is that the battery voltage V measured in the state where charging is stopped has reached the threshold value V1 (4.3 V) (S44, S45, S46: NO). This is because in a state where charging is stopped, the charge distribution is relaxed, and it can be determined whether the battery is fully charged based on the battery voltage. The battery voltage during charging cannot be used as a charge termination condition.
After the completion of charging, the battery was discharged at a constant current of 288 mA to 3.0 V. Charging and discharging were repeated 500 times.

 

 

In comparison with Comparative Examples 1 and 2, in Examples 1 to 4, both the SOC (State of charge) 80% charge and the SOC 100% charge are improved in charging speed. In Example 1, the discharge capacity retention rate is improved compared to Comparative Example 2 having the same capacity. In Examples 2 to 4, the discharge capacity retention rate is maintained as compared with Comparative Example 1 having the same capacity. Therefore, it can be seen that the charging method of the present disclosure can suppress deterioration and shorten the charging time.

As described above, in the charging method of the non-aqueous secondary battery according to the present embodiment, the value corresponding to the thickness of the battery 2 is detected by the detection sensor 5, and the value ΔT corresponding to the thickness becomes the first set value ΔT1. Until this time, the battery 2 is charged with a constant current with a predetermined current.

The charging system for a non-aqueous secondary battery according to this embodiment includes a detection sensor 5 that detects a value corresponding to the thickness of the battery, and a charging device 8 that supplies a current to the secondary battery based on the detection result of the detection sensor 5. . The charging device 8 charges the battery at a constant current with a predetermined current until the value ΔT corresponding to the thickness of the battery reaches the first set value ΔT1.

The first set value ΔT1 is a constant current / constant voltage charge to a rated voltage (full charge) at a low current (a current with a magnitude that makes the charging speed relatively slow) so that a charge distribution does not occur. A value corresponding to the thickness is preferably set. That is, the first set value ΔT1 is a value corresponding to the thickness of the battery when charging has progressed uniformly for all active materials. The “value corresponding to the thickness” may be a value corresponding to the value of the thickness as it is, or a value corresponding to a slightly reduced thickness by providing a predetermined amount of margin in the thickness for safety. As a method for setting the margin, for example, it is conceivable to use a thickness multiplied by a predetermined coefficient such as 0.9. In this embodiment, a value (no margin is provided) corresponding to the thickness of the battery when charged to 4.3 V with a current of 288 mA (0.2 C) is used. 1C is a current value at which discharge is completed in 1 hour after the battery is discharged at a constant current. Although it depends on the battery, the low current is 0.3 C or less, preferably 0.2 C or less, more preferably 0.1 C or less, still more preferably 0.05 C or less, 0.01 C or less.

The current of a predetermined magnitude in constant current charging is a large current for quick charging, and the value can be arbitrarily set. In this embodiment, it is 3C, but is not limited to this.

In the present disclosure, the constant current charging includes not only charging with a constant current value but also a slight fluctuation of the current value.

In this manner, constant current charging is performed with a predetermined current until the value corresponding to the thickness of the battery reaches the first set value, so that a predetermined large current compared to constant current constant voltage charging. Charging can be continued for a long time, and the charging time can be reduced. In addition, although the charging depth of the active material that is most charged is not considered at the voltage during charging, the value corresponding to the thickness of the battery is referred to as in the present disclosure, so that the active material that is most charged is The depth of charge can be taken into account and battery deterioration can be suppressed.

In the present embodiment, after the value ΔT corresponding to the thickness reaches the first set value ΔT1 by constant current charging, the value ΔT corresponding to the thickness is supplied to the battery so as to be maintained at the first set value ΔT1. Shift to constant thickness charging to change the current value. A specific example of control for changing the current value so that the value corresponding to the detected thickness is maintained at the first set value ΔT1 is to set a threshold value smaller than the first set value ΔT1, and to set this threshold value. On-off control, P control, I control, D control, PD control, PI control, PID control, pulse control, PWM control, PAM control, or a combination of these controls may be used as target values. Further, if it can be controlled so as not to exceed the first set value ΔT1, ΔT1 may be set as the target value.

As described above, for example, until reaching the first set value ΔT1 corresponding to the thickness of the charging depth of 100%, the charging time can be reduced without deteriorating by constant current charging with a large current, and thereafter the thickness is constant. This means that charging is performed at the same speed as the diffusion rate of ions and electrons, and in principle, charging can be performed at the fastest charging speed.

In the present embodiment, after the value ΔT corresponding to the thickness reaches the first set value ΔT1 by constant current charging, the first set value ΔT1 and the second set value ΔT2 lower than the first set value ΔT1 In the meantime, the on / off charging is switched to turn on / off the current supplied to the battery so that the value ΔT corresponding to the thickness exists.

In this way, by controlling the current on / off, charging is performed while relaxing the charge distribution caused by rapid charging, so that deterioration of the battery can be suppressed.

In the present embodiment, the constant voltage that changes the current value supplied to the battery so that the voltage of the battery is maintained at a predetermined voltage after the value ΔT corresponding to the thickness reaches the first set value ΔT1 by constant current charging. Transition to charging.

Thus, if the charging time is shortened without promoting deterioration by constant current charging, the charging time can be reduced even if constant voltage charging is applied.

In the present embodiment, the detection sensor 5 includes a polymer matrix layer 3 that contacts the battery 2 and a detection unit 4. The polymer matrix layer 3 contains a filler that changes the external field according to deformation. The detection unit 4 detects a value corresponding to the thickness of the battery 2 by detecting a change in the external field according to the deformation of the polymer matrix layer 3.

In this embodiment, the polymer matrix layer 3 contains a magnetic filler as a filler, and the detection unit 4 detects a value corresponding to the thickness of the battery 2 by detecting a change in the magnetic field as an external field.

As the active material used for the negative electrode of the lithium ion secondary battery, a material capable of electrochemically inserting and extracting lithium ions is used. In order to obtain the first curve L1 and the reference curve LS having the above-described unevenness, for example, a negative electrode containing graphite, hard carbon, soft carbon, silicon, sulfur or the like is preferably used, and among these, a negative electrode containing graphite Is more preferably used. Examples of the active material used for the positive electrode include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , Li (MnAl) ₂ O ₄ , Li (NiCoAl) O ₂ , LiFePO ₄ , and Li (NiMnCo) O _2. The

In the embodiment shown in FIG. 2, the polymer matrix layer 3 is affixed to the wall portion 28a of the outer package 21 facing the electrode group 22 in the thickness direction of the positive electrode 23 and the negative electrode 24, that is, the Z direction (vertical direction in FIG. 2B). Attached. The outer surface of the wall portion 28 a corresponds to the upper surface of the exterior body 21. The polymer matrix layer 3 is opposed to the electrode group 22 with the wall portion 28 a interposed therebetween, and is disposed in parallel with the upper surface of the electrode group 22. Since the electrode swelling is caused by the change in the thickness of the electrode group 22 accompanying the change in the volume of the active material, the action in the Z direction is large. Therefore, in the present embodiment in which the polymer matrix layer 3 is attached to the wall portion 28a, the electrode swelling can be detected with high sensitivity, and the remaining capacity of the secondary battery 2 can be accurately predicted.

Alternatively, the polymer matrix layer 3 may be attached to the electrode group 22 from the thickness direction of the positive electrode 23 and the negative electrode 24, that is, the Z direction. As a result, even when the exterior body is formed of a robust material such as a metal can, the swollenness of the electrode group 22, that is, the swollenness of the electrode can be detected with high accuracy, and the remaining of the secondary battery 2 is extended. Capacity can be accurately predicted.

The detection unit 4 is disposed at a location where a change in the external field can be detected, and is preferably affixed to a relatively rigid location that is not easily affected by the swelling of the secondary battery 2. In this embodiment, as shown in FIG. 2B, the detection unit 4 is attached to the inner surface of the casing 11 of the battery module facing the wall 28a. The casing 11 of the battery module is formed of, for example, metal or plastic, and a laminate film may be used. In the drawing, the detection unit 4 is disposed close to the polymer matrix layer 3, but may be disposed away from the polymer matrix layer 3.

In the present embodiment, an example is shown in which the polymer matrix layer 3 contains a magnetic filler as the filler, and the detection unit 4 detects a change in the magnetic field as the external field. In this case, the polymer matrix layer 3 is preferably a magnetic elastomer layer in which a magnetic filler is dispersed in a matrix made of an elastomer component.

Examples of the magnetic filler include rare earths, irons, cobalts, nickels, oxides, etc., but rare earths capable of obtaining higher magnetic force are preferable. The shape of the magnetic filler is not particularly limited, and may be spherical, flat, needle-like, columnar, or indefinite. The average particle size of the magnetic filler is preferably 0.02 to 500 μm, more preferably 0.1 to 400 μm, and still more preferably 0.5 to 300 μm. When the average particle size is smaller than 0.02 μm, the magnetic properties of the magnetic filler tend to be lowered, and when the average particle size exceeds 500 μm, the mechanical properties of the magnetic elastomer layer tend to be lowered and become brittle.

The magnetic filler may be introduced into the elastomer after magnetization, but is preferably magnetized after being introduced into the elastomer. Magnetization after introduction into the elastomer facilitates control of the polarity of the magnet and facilitates detection of the magnetic field.

As the elastomer component, a thermoplastic elastomer, a thermosetting elastomer, or a mixture thereof can be used. Examples of the thermoplastic elastomer include styrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, polybutadiene-based thermoplastic elastomer, polyisoprene-based thermoplastic elastomer, A fluororubber-based thermoplastic elastomer can be used. Examples of the thermosetting elastomer include polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, polychloroprene rubber, nitrile rubber, diene synthetic rubber such as ethylene-propylene rubber, ethylene-propylene rubber, butyl rubber, acrylic rubber, Non-diene synthetic rubbers such as polyurethane rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, and natural rubber can be mentioned. Among these, a thermosetting elastomer is preferable because it can suppress the sag of the magnetic elastomer accompanying heat generation and overload of the battery. More preferred is polyurethane rubber (also referred to as polyurethane elastomer) or silicone rubber (also referred to as silicone elastomer).

Polyurethane elastomer is obtained by reacting polyol and polyisocyanate. When using a polyurethane elastomer as an elastomer component, an active hydrogen-containing compound and a magnetic filler are mixed, and an isocyanate component is mixed here to obtain a mixed solution. Moreover, a liquid mixture can also be obtained by mixing a magnetic filler with an isocyanate component and mixing an active hydrogen-containing compound. The mixed liquid is poured into a mold subjected to a release treatment, and then heated to a curing temperature and cured to produce a magnetic elastomer. When a silicone elastomer is used as an elastomer component, a magnetic elastomer can be produced by adding a magnetic filler to a silicone elastomer precursor, mixing it, putting it in a mold, and then heating and curing it. In addition, you may add a solvent as needed.

As the isocyanate component that can be used in the polyurethane elastomer, compounds known in the field of polyurethane can be used. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene Aromatic diisocyanates such as diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, nor It can be mentioned alicyclic diisocyanates such as Renan diisocyanate. These may be used alone or in combination of two or more. The isocyanate component may be modified such as urethane modification, allophanate modification, biuret modification, and isocyanurate modification. Preferred isocyanate components are 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, more preferably 2,4-toluene diisocyanate, 2,6-toluene diisocyanate.

As the active hydrogen-containing compound, those usually used in the technical field of polyurethane can be used. For example, polytetramethylene glycol, polypropylene glycol, polyethylene glycol, polyether polyol represented by copolymer of propylene oxide and ethylene oxide, polybutylene adipate, polyethylene adipate, representative of 3-methyl-1,5-pentane adipate Polyester polyol such as polyester polyol such as polyester polyol, polycaprolactone glycol, reaction product of polyester glycol such as polycaprolactone glycol and alkylene carbonate, ethylene carbonate is reacted with polyhydric alcohol, Polyester polycarbonate polyol reacted with organic dicarboxylic acid, polyhydroxyl compound and aryl carbonate It can be mentioned a high molecular weight polyol and polycarbonate polyols obtained by ester exchange reaction. These may be used alone or in combination of two or more.

In addition to the high molecular weight polyol component described above as the active hydrogen-containing compound, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, trimethylolpropane, glycerin, 1,2,6- Hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclohexanol, and triethanol Low molecular weight polyol component of such emissions, ethylenediamine, tolylenediamine, diphenylmethane diamine, may be used low molecular weight polyamine component of diethylenetriamine. These may be used alone or in combination of two or more. Further, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5-bis ( Methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6- Diamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane, 4,4'-diamino-3,3 ' -Diethyl-5,5'-dimethyldiphenylmethane, N, N'-di-sec-butyl-4,4'-diaminodiphenylmethane, 4,4'-diamy -3,3'-diethyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-diisopropyl-5,5'- Dimethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraisopropyldiphenylmethane, m-xylylenediamine, Polyamines exemplified by N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, p-xylylenediamine and the like can also be mixed. Preferred active hydrogen-containing compounds are polytetramethylene glycol, polypropylene glycol, a copolymer of propylene oxide and ethylene oxide, 3-methyl-1,5-pentane adipate, more preferably a copolymer of polypropylene glycol, propylene oxide and ethylene oxide. It is a coalescence.

As a preferred combination of the isocyanate component and the active hydrogen-containing compound, as the isocyanate component, one or more of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and 4,4′-diphenylmethane diisocyanate, active hydrogen Examples of the contained compound include polytetramethylene glycol, polypropylene glycol, a copolymer of propylene oxide and ethylene oxide, and one or more of 3-methyl-1,5-pentaneadipate. More preferably, a combination of 2,4-toluene diisocyanate and / or 2,6-toluene diisocyanate as the isocyanate component and polypropylene glycol and / or a copolymer of propylene oxide and ethylene oxide as the active hydrogen-containing compound. is there.

The polymer matrix layer 3 may be a foam containing dispersed filler and bubbles. A general resin foam can be used as the foam, but it is preferable to use a thermosetting resin foam in consideration of characteristics such as compression set. Examples of the thermosetting resin foam include a polyurethane resin foam and a silicone resin foam. Among these, a polyurethane resin foam is preferable. The above-mentioned isocyanate component and active hydrogen-containing compound can be used for the polyurethane resin foam.

The amount of the magnetic filler in the magnetic elastomer is preferably 1 to 450 parts by weight, more preferably 2 to 400 parts by weight with respect to 100 parts by weight of the elastomer component. If it is less than 1 part by weight, it tends to be difficult to detect a change in the magnetic field, and if it exceeds 450 parts by weight, the magnetic elastomer itself may become brittle.

For the purpose of rust prevention of the magnetic filler, a sealing material for sealing the polymer matrix layer 3 may be provided to the extent that the flexibility of the polymer matrix layer 3 is not impaired. As the sealing material, a thermoplastic resin, a thermosetting resin, or a mixture thereof can be used. Examples of the thermoplastic resin include styrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polybutadiene-based thermoplastic elastomers, polyisoprene-based thermoplastic elastomers, Fluorine-based thermoplastic elastomer, ethylene / ethyl acrylate copolymer, ethylene / vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, fluororesin, polyamide, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polybutadiene Etc. Examples of the thermosetting resin include polyisoprene rubber, polybutadiene rubber, styrene / butadiene rubber, polychloroprene rubber, diene-based synthetic rubber such as acrylonitrile / butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, butyl rubber, Non-diene rubbers such as acrylic rubber, polyurethane rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, natural rubber, polyurethane resin, silicone resin, epoxy resin and the like can be mentioned. These films may be laminated, or may be a film including a metal foil such as an aluminum foil or a metal vapor deposition film in which a metal is vapor deposited on the film.

The polymer matrix layer 3 may be one in which fillers are unevenly distributed in the thickness direction. For example, the polymer matrix layer 3 may have a structure composed of two layers of a region on one side with a relatively large amount of filler and a region on the other side with a relatively small amount of filler. In the region on one side containing a large amount of filler, the change in the external field with respect to the small deformation of the polymer matrix layer 3 becomes large, so that the sensor sensitivity to a low internal pressure can be enhanced. Further, the region on the other side with relatively little filler is relatively flexible and easy to move. By attaching this region, the polymer matrix layer 3 (especially the region on one side) is likely to be deformed.

The filler uneven distribution ratio in the region on one side is preferably more than 50, more preferably 60 or more, and further preferably 70 or more. In this case, the filler uneven distribution rate in the other region is less than 50. The filler uneven distribution rate in the region on one side is 100 at the maximum, and the filler uneven distribution rate in the region on the other side is 0 at the minimum. Therefore, a laminate structure of an elastomer layer containing a filler and an elastomer layer not containing a filler may be used. For the uneven distribution of the filler, after introducing the filler into the elastomer component, it can be allowed to stand at room temperature or at a predetermined temperature, and then spontaneously settled according to the weight of the filler, by changing the temperature and time of standing. The filler uneven distribution rate can be adjusted. The filler may be unevenly distributed using a physical force such as centrifugal force or magnetic force. Alternatively, the polymer matrix layer may be constituted by a laminate composed of a plurality of layers having different filler contents.

The filler uneven distribution rate is measured by the following method. That is, the cross section of the polymer matrix layer is observed at a magnification of 100 using a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDS). The area of the entire cross section in the thickness direction and the two areas obtained by dividing the cross section into two in the thickness direction are each subjected to elemental analysis of a metal element specific to the filler (for example, Fe element in the case of the magnetic filler of this embodiment). Find the abundance. For this abundance, the ratio of one area to the entire area in the thickness direction is calculated, and this is used as the filler uneven distribution rate in the one area. The filler uneven distribution rate in the other region is the same as this.

The other region with relatively little filler may have a structure formed of a foam containing bubbles. Thereby, the polymer matrix layer 3 is further easily deformed and the sensor sensitivity is enhanced. Moreover, the area | region of one side may be formed with the foam with the area | region of the other side, and the polymer matrix layer 3 in that case becomes a foam entirely. Such a polymer matrix layer in which at least a part in the thickness direction is a foam is composed of a laminate composed of a plurality of layers (for example, a non-foamed layer containing a filler and a foamed layer not containing a filler). It doesn't matter.

For example, a magnetoresistive element, a Hall element, an inductor, an MI element, a fluxgate sensor, or the like can be used as the detection unit 4 that detects a change in the magnetic field. Examples of the magnetoresistive element include a semiconductor compound magnetoresistive element, an anisotropic magnetoresistive element (AMR), a giant magnetoresistive element (GMR), and a tunnel magnetoresistive element (TMR). Among these, the Hall element is preferable because it has high sensitivity over a wide range and is useful as the detection unit 4. As the Hall element, for example, EQ-430L manufactured by Asahi Kasei Electronics Corporation can be used.

Since the secondary battery 2 in which the gas expansion has progressed may lead to troubles such as ignition and rupture, in this embodiment, when the expansion amount when the secondary battery 2 is deformed is greater than or equal to a predetermined amount, charging and discharging are performed. It is configured to be blocked. Specifically, the signal detected by the detection sensor 5 is transmitted to the control device 6, and the control device 6 transmits a signal to the switching circuit 7 when a change in the external field exceeding the set value is detected by the detection sensor 5. Then, the current from the power generation device (or charging device) 8 is cut off, and charging / discharging to the battery module 1 is cut off. Thereby, the trouble resulting from gas bulging can be prevented beforehand.

In the above-described embodiment, an example in which the secondary battery is a lithium ion secondary battery has been described. The secondary battery used may be a non-aqueous electrolyte secondary battery.

In the above-described embodiment, the example in which the change in the magnetic field due to the deformation of the polymer matrix layer is detected by the detection unit has been described. For example, the polymer matrix layer may contain conductive fillers such as metal particles, carbon black, and carbon nanotubes as fillers, and the detector may detect changes in the electric field (changes in resistance and dielectric constant) as external fields. It is done.

The structure employed in each of the above embodiments can be employed in any other embodiment. The specific configuration of each unit is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present disclosure.

For example, in the embodiment described above, a sensor that detects a value corresponding to the thickness of the battery is used, and constant current charging is performed with a predetermined amount of current until the value corresponding to the thickness becomes the first set value. However, it is thought that it can be replaced with another parameter by prior measurement. For example, it may be possible to replace the battery state information obtained from an ammeter and a voltmeter with a combination of charging up to a predetermined charging capacity with a predetermined current value. The battery state information includes at least one of battery voltage, charge / discharge depth, DC resistance, or AC resistance. That is, the charging method includes a database creation step and a charging step.

In the database creation process, battery state information is acquired based on the measurement results of the ammeter and the voltmeter, and the charging current having a predetermined magnitude is determined until the value corresponding to the battery thickness becomes the first set value. Current charging is performed, the charging capacity at that time is measured, and the obtained battery state information, charging current value and charging capacity are stored in a database. This operation is performed with various battery states and various charging current values, and a plurality of battery states and a plurality of charging patterns (current values and charging capacities) are stored in the database.

In the charging process, battery state information is acquired by an ammeter and a voltmeter, a charging current value and a charging capacity corresponding to the acquired battery state are acquired from a database, and constant current charging is performed with the charging current value and charging capacity.

In other words, the non-aqueous secondary battery charging method is based on battery state information based on an ammeter and a voltmeter and a constant charging current value until a value corresponding to the battery thickness reaches a first set value. The charging capacity when the current is charged is referred to a database associated in advance, the charging current value and the charging capacity corresponding to the battery state information based on the ammeter and the voltmeter are obtained, and the charging current value and the charging capacity are Perform constant-current charging.

The charging current value and the charging capacity corresponding to the battery state in the database are constant current charged until the value corresponding to the thickness becomes the first set value using a sensor that detects the value corresponding to the thickness of the battery. Charging current value and charging capacity. Even if a sensor that detects the value corresponding to the thickness of the battery is not installed, if the charging current value and the charging capacity corresponding to the battery state and the battery state can be obtained from the database, the sensor that detects the value corresponding to the thickness is used. The same effect as charging can be reproduced.

2 ... Sealed secondary battery 3 ... Polymer matrix layer 4 ... Detection unit 5 ... Detection sensor

Claims (8)

A method for charging a non-aqueous secondary battery,
A charging method in which a value corresponding to the thickness of the battery is detected by a detection sensor, and the battery is charged at a constant current with a predetermined current until the value corresponding to the thickness reaches a first set value. A current value to be supplied to the battery so that the value corresponding to the thickness is maintained at the first set value after the value corresponding to the thickness reaches the first set value by the constant current charging. The method according to claim 1, wherein the method shifts to constant thickness charging to be changed. After the value corresponding to the thickness reaches the first set value due to the constant current charging, the thickness is between the first set value and a second set value lower than the first set value. The method according to claim 1, wherein the method shifts to on-off charging for turning on and off a current supplied to the battery so that a value corresponding to the current value exists. After the value corresponding to the thickness reaches the first set value by the constant current charging, the constant voltage charging changes the current value supplied to the battery so that the voltage of the battery is maintained at a predetermined voltage. The method of claim 1, wherein the transition is performed. The detection sensor has a polymer matrix layer that contacts the battery, and a detection unit,
The polymer matrix layer contains dispersed fillers that change the external field according to deformation,
The method according to any one of claims 1 to 4, wherein the detection unit detects a value corresponding to the thickness of the battery by detecting a change in an external field according to deformation of the polymer matrix layer. The polymer matrix layer contains a magnetic filler as the filler, and the detection unit detects a value corresponding to the thickness of the battery by detecting a change in the magnetic field as the external field. The method described. There is a charging system for non-aqueous secondary batteries,
A detection sensor for detecting a value corresponding to the thickness of the battery;
A charging device for supplying a current to the secondary battery based on a detection result of the detection sensor,
The charging device is a charging system in which the battery is charged at a constant current with a predetermined current until a value corresponding to the thickness of the battery reaches a first set value. A method for charging a non-aqueous secondary battery,
Battery state information based on an ammeter and a voltmeter is associated in advance with a charge capacity when a constant current charge is performed at a certain charge current value until a value corresponding to the thickness of the battery reaches a first set value. A charging method of referring to a database, acquiring a charging current value and a charging capacity corresponding to battery state information based on an ammeter and a voltmeter, and performing constant current charging with the charging current value and the charging capacity.

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