JP5609859B2 - Battery system - Google Patents

Description

  The present invention relates to a battery system, and more particularly to a battery system that can detect and evaluate an uneven charge state generated in an electrode body of a secondary battery.

Secondary batteries such as lithium ion secondary batteries are used on the other side of vehicles such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles, household electric devices such as laptop computers, and industrial devices such as impact drivers.
An index indicating the state of such a secondary battery (hereinafter also simply referred to as a battery) is SOC (State of Charge). The battery is normally used within the range of 0% (total discharge) to 100% (full charge) in terms of SOC. And in performing charge / discharge control of a battery, this SOC value is often used.
Therefore, Patent Document 1 discloses a method for estimating the SOC of a battery in accordance with the average concentration in the active material of the electrode in order to accurately estimate the SOC (see paragraph 0031).

The battery may be used without pressing (compressing) the electrode body. However, in order to stabilize battery characteristics, a battery having a flat wound electrode body or a stacked electrode body uses a compression structure. In many cases, these electrode bodies are used while being pressed in the thickness direction.
For example, specifically, a flat wound electrode body or a stacked electrode body is held in a substantially rectangular parallelepiped battery case, a battery is interposed between two compression plates, and the interval between the compression plates is reduced. By tightening the two compression plates with bolts spanning between the compression plates, the electrode body is pressed in the thickness direction through the wall portion (case main surface) of the battery case.
A battery group in which a plurality of such batteries are arranged in the thickness direction of the electrode body and the batteries are brought into contact with each other directly or via a spacer may be used as a compressed assembled battery. Also in this case, by interposing a battery group between the two compression plates and tightening the two compression plates with bolts spanned between the compression plates in a direction in which the interval between the compression plates decreases, for each battery, The electrode body is pressed in the thickness direction through the wall portion (case main surface) of the battery case.

  Thus, when the case main surface of the battery is compressed in the thickness direction of the electrode body, the thickness direction battery portion in which the positive electrode plate and the negative electrode plate overlap with each other via the separator in the thickness direction of the electrode body, Compressed in the thickness direction. That is, a surface pressure is applied to the thickness direction battery portion of the electrode body.

By the way, in the battery compressed in this way, with respect to the surface pressure applied to the battery body in the thickness direction of the electrode body, the surface pressure received by each part of the thickness direction battery section (hereinafter also referred to as local surface pressure Pp). Can think.
Similarly to this, the battery can be considered the SOC of the whole battery described above (the whole SOC: hereinafter also referred to as SOCh), and for each part obtained by subdividing the thickness direction battery part of the electrode body, It is also possible to consider the SOC of a local battery (local SOC: hereinafter also referred to as SOCp).

Further, in the battery, the electrode body expands and contracts due to charge / discharge (increase / decrease in SOC). For this reason, in each battery constituting a battery or an assembled battery compressed using the compression structure as described above, the local surface pressure applied to each part in the battery portion in the thickness direction of the electrode body also increases or decreases.
In addition, due to charging / discharging of the battery, the overall SOCh of the battery and the local SOCp of each part in the battery portion in the thickness direction of the electrode body also increase or decrease.

  However, at the initial use of the battery, the local surface pressure Pp applied to each part in the thickness direction battery portion of the electrode body is substantially uniform in the thickness direction battery portion. Further, the local SOCp of each part of the thickness direction battery part is also substantially uniform in the thickness direction battery part, and is substantially the same as the entire SOCh.

JP 2008-243373 A

However, when the battery continues to be used, particularly when uneven charge / discharge is continued, such as repeatedly performing high-rate discharge, local SOCp in each part of the battery body in the thickness direction of the electrode body is gradually unevenly distributed. It has been found that there is. In this case, the overall SOCh is roughly the average of the local SOCp of each part, but there is variation (unevenness) in the distribution of the local SOCp of each part.
When the battery in such a state is charged, the local SOCp becomes 100% or a value that exceeds this value at an early stage at a portion where the local SOCp is high, so that the inter-terminal voltage also increases as a whole battery. For this reason, although other parts can still be charged, it is determined that the total SOCh is also an upper limit (for example, full charge). On the contrary, when the battery in such a state is discharged, the local SOCp becomes 0% or a value that is lower than the local SOCp at a part where the local SOCp is low. For this reason, it is determined that the total SOCh is also a lower limit (for example, total discharge) even though other parts can still be discharged. Thus, in such a battery, there is a problem that the battery capacity that can actually be used decreases.

  On the other hand, it has been found that in such a battery having variations in local SOCp, the local surface pressure Pp of each part in the battery portion in the thickness direction of the electrode body also varies. Specifically, it has been found that in a battery in which the local SOCp of each part varies, the local surface pressure Pp is a distribution that is roughly inverted with respect to the local SOCp distribution. In other words, it has been found that the local SOCp is low in the region where the local surface pressure is high, and conversely, the local SOCp is high in the region where the local surface pressure is low.

  The present invention has been made on the basis of such knowledge, and it is an object of the present invention to provide a battery system capable of detecting variations in local surface pressure Pp at each part in the battery portion in the thickness direction of the electrode body.

One aspect of the present invention is a rectangular battery case including a flat wound or stacked electrode body and a pair of plate-like case main surfaces orthogonal to the thickness direction of the electrode body and accommodating the electrode body. One or more secondary batteries and one of the secondary batteries, or each of the plurality of secondary batteries arranged in a form in which the main surface of the case is parallel to each other, A configuration in which a positive electrode plate and a negative electrode plate overlap in the thickness direction of the electrode body via the separator through the pair of case main surfaces to perform a battery action, and compress the thickness direction battery portion in the thickness direction. The compressed structure and the one of the secondary batteries, or the secondary battery of any one of the plurality of secondary batteries, disposed in contact with the case main surface of the battery case, and the compressed structure To the body Ri, through the casing main surface, for detecting respectively the magnitude of the local surface pressure applied to each site in the thickness direction battery portion of the electrode body, a plate-shaped surface pressure sensor, detected by the upper Symbol surface pressure sensor, A battery system comprising: an acquisition unit that acquires the local surface pressure applied to each part in the thickness direction battery part of the electrode body; and a distribution evaluation unit that evaluates a distribution situation of the local surface pressure of each part. is there.

This battery system includes an acquisition unit that acquires a local surface pressure applied to each part in the battery portion in the thickness direction of the electrode body, and a distribution evaluation unit that evaluates the distribution state of the local surface pressure.
Thereby, the local surface pressure of each part is acquired, and the distribution situation (for example, the presence or absence of variation, the magnitude of variation, etc.) of local surface pressure can be evaluated using this. Therefore, the distribution state of the local SOCp can be grasped from the distribution state of the local surface pressure.
Furthermore, it responds according to the distribution state of local surface pressure (and therefore local SOCp), for example, changes in driving conditions (charge / discharge conditions) when using the battery, and variations in distribution of local surface pressure (local SOCp) are alleviated. Appropriate measures can be taken, such as performing a charge / discharge operation on the battery with a pattern, and sending a warning.

The “thickness direction battery part” refers to a portion of the flat wound type or stacked type electrode body in which the positive electrode plate and the negative electrode plate overlap each other via a separator in the thickness direction to perform a battery action.
In the flat wound electrode body, the belt-like positive electrode plate and the negative electrode plate are wound through a separator, while being flattened in the thickness direction. Therefore, in this flat wound electrode body, there are parts that perform the battery action in addition to the part where the positive electrode plate and the negative electrode plate overlap each other in the thickness direction via the separator (thickness direction battery part). Thus, a portion where the positive electrode plate, the negative electrode plate and the separator are curved and overlapped is included in a semi-cylindrical shape (R shape).
On the other hand, in the laminated electrode body, generally, the portion that performs the battery action coincides with the thickness direction battery portion in which the positive electrode plate and the negative electrode plate overlap in the thickness direction via the separator.

As the compression structure, for example, two plate-shaped members sandwich one or a plurality of secondary batteries arranged in a row, and a plate with bolts, bolts and nuts, or a metal binding band that spans between the plate-shaped members. For example, each secondary battery may be configured to compress the thickness direction battery portion in the thickness direction by tightening so as to compress between the members. In addition, when sandwiching a plurality of secondary batteries, a spacer may be interposed between the secondary batteries.
The surface pressure sensors, via one of the case main face of the battery case, the magnitude of the local surface pressure applied to each portion in the thickness direction battery unit surface, measurably multiplexing the surface pressure sensors independently It is a thing. Measuring local surface pressure by using a surface pressure sensor this, as the measurement position in the thickness direction battery unit, it is preferable to measure the local surface pressure for a number of sites within the surface in the thickness direction battery unit. For example, the local surface pressure may be measured for each measurement position arranged in the form of a vertical and horizontal grid over the entire surface of the thickness direction battery unit. Further, the local surface pressure may be measured for each of a plurality of measurement positions arranged on a straight line along the axis of the wound electrode body.

  Furthermore, in the battery system according to any one of the above, the distribution evaluation unit is a determination unit that determines the size of the variation in the distribution of the local surface pressure. In the determination unit, the distribution of the local surface pressure is When it is determined that the variation of the local battery is large, the battery system may include a relaxation charging / discharging unit that charges and discharges the secondary battery in a pattern that relaxes the variation of the local surface pressure distribution.

  As described above, the distribution of the local surface pressure in each part in the thickness direction battery portion has a large variation (the unevenness is large. That is, the size of the local surface pressure is not uniform and varies greatly depending on the location. ), It is estimated that the distribution of local SOCp also varies greatly. In this case, the substantial capacity of the battery is not preferable.

On the other hand, in the battery system described above, when the determination means determines that the variation in local surface pressure distribution is large, charging / discharging in a pattern that reduces the variation in local surface pressure distribution by the relaxation charging / discharging means. To do.
For this reason, the variation in the local surface pressure distribution of the battery is alleviated. At the same time, the variation in the local SOCp distribution of the battery is also alleviated, and the capacity of the battery can be recovered.

  Furthermore, in the battery system described above, the determination unit determines the distribution of the local surface pressure when the fluctuation range obtained by subtracting the minimum value from the acquired maximum value of the local surface pressure exceeds a threshold value. It is preferable to use a battery system which is a fluctuation range judging means for judging that the variation is large.

  In this battery system, the variation range determination means determines that the variation in the distribution of the local surface pressure is large when the variation range of the local surface pressure exceeds a threshold value. In this way, the process for obtaining the fluctuation range is easy, and the variation in the local surface pressure distribution can be easily and reliably determined.

  Further, in the battery system according to the above item 2, the relaxation charging / discharging unit causes the secondary battery to be discharged at a discharge current of 2 C or less from a predetermined starting SOC within a range of SOC = 20 to 50%. The battery system may be an overdischarge charging unit that performs overdischarge to the lower limit discharge SOC within the range of SOC = 0 to −30%, and then charges to the start SOC with a charging current of 2C or less.

  In this battery system, the overdischarge charging means, which is a relaxation charging means, is discharged to a state of overdischarge with a relatively small current, and further charged to a starting SOC with a relatively small current. For this reason, the variation in local surface pressure distribution generated in the electrode body can be reliably relaxed and uniformed, the variation in local SOCp distribution can also be alleviated, and the battery capacity can be recovered.

  Furthermore, in the battery system according to any one of the above, the SOC of the secondary battery is determined in advance within a range of SOC = 20 to 50% prior to the acquisition of the local surface pressure by the acquisition unit. It is preferable that the battery system includes a standardization unit that sets the standard SOC.

  In this battery system, since the SOC of the battery is set as the reference SOC prior to the acquisition of the local surface pressure by the standardization means, the local surface pressure in the same battery state can be acquired, and the evaluation of the distribution state of the local surface pressure can be performed. Easy to do.

It is explanatory drawing which shows schematic structure of the vehicle carrying the battery system concerning embodiment. It is explanatory drawing which shows connection relations between an assembled battery, a control apparatus, etc. concerning embodiment. It is explanatory drawing which concerns on embodiment and shows the assembled battery used with a battery system. It is a perspective view of the lithium ion secondary battery which concerns on embodiment and comprises an assembled battery. It is a graph which shows the local surface pressure distribution of the axial direction in the battery after a high-rate discharge cycle test. It is a graph which shows the local SOCp distribution of an axial direction in the battery after a high-rate discharge cycle test. It is a flowchart which shows the processing procedure of surface pressure distribution evaluation and relaxation charge / discharge among control in a control apparatus (ECU) concerning embodiment. It is a flowchart which shows the process sequence of a relaxation charging / discharging subroutine among control in an control apparatus (ECU) concerning embodiment. It is a graph which shows the example of distribution of local surface pressure before and after performing relaxation charge / discharge with respect to a battery.

  An embodiment in which a battery system of the present invention is applied to a plug-in hybrid vehicle (PHEV) will be described with reference to the drawings. First, a plug-in hybrid vehicle (hereinafter simply referred to as a vehicle) 100 equipped with the battery system 300 according to the present embodiment will be described with reference to FIGS. 1 and 2. The vehicle 100 includes an engine 110, a generator 120, a PCU (Power Control Unit) 130, an assembled battery 10, a motor 140, and an ECU (Electronic Control Unit) 150 that is communicably connected thereto. Among them, the PCU 130 controls charging / discharging between the generator 120 and the motor 140 and the assembled battery 10 according to an instruction from the ECU 150, and includes an inverter 131 and a converter 132. The PCU 130 also includes a charging device 133 that charges the assembled battery 10 with power supplied from an external power source (commercial power source). The assembled battery 10 is formed by connecting a number of batteries 1 in series as will be described later.

  In this vehicle 100, the power generated by the engine 110 is divided into two paths by a power distribution mechanism 180 constituted by planetary gears. One is a path for driving the wheel 200 via the speed reducer 190. The other is a path for driving the generator 120 to generate power. The power generator 120 generates power using the power of the engine 110 distributed by the power distribution mechanism 180. The power generated by the power generator 120 depends on the operating state of the vehicle 100 and the SOC value of the battery pack 10. Can be used properly. For example, during normal traveling or sudden acceleration, the power generated by the generator 120 is used as power for driving the motor 140 as it is. On the other hand, when the SOC of the battery pack 10 is lower than a predetermined value, the power generated by the generator 120 is converted from AC power to DC power by the inverter 131 of the PCU 130, and the voltage is adjusted by the converter 132. The battery pack 10 is charged.

  The motor 140 is a three-phase AC motor, and is driven by at least one of the electric power stored in the assembled battery 10 and the electric power generated by the generator 120. The driving force of the motor 140 is transmitted to the wheel 200 via the speed reducer 190. Accordingly, the motor 140 assists the engine 110 to cause the vehicle 100 to travel, or causes the vehicle 100 to travel only with the driving force of the motor 140.

  On the other hand, at the time of regenerative braking of vehicle 100, motor 140 is driven by wheel 200 via reduction gear 190, and this motor 140 is operated as a generator. As a result, the motor 140 acts as a regenerative brake that converts braking energy into electric power. The electric power generated by the motor 140 is charged into the assembled battery 10 via the inverter 131 and the converter 132 of the PCU 130.

  ECU 150 includes a CPU (Central Processing Unit) 151 and a memory 152. The CPU 151 operates the vehicle 100, the ON / OFF signal input from the drive switch 220, the accelerator opening detected by the accelerator opening sensor 210, the change rate of the accelerator opening, the shift position, the assembled battery 10 (this The calculation processing is performed based on the SOC of the battery 1) and the map and program stored in the memory 152. Thereby, ECU 150 controls various devices mounted on vehicle 100 so that vehicle 100 is in a desired driving state. The ECU 150 monitors the state of the assembled battery 10 and other various devices not only when the vehicle 100 is operated but also when the operation is completed (drive switch OFF period). The ECU 150, the assembled battery 10 (battery 1), the multiple surface pressure sensor 30, and the sensor connector 31 form a battery system 300.

  As shown in FIG. 2, the vehicle 100 further includes a voltmeter 160 that sequentially measures the charge / discharge voltage value Vb of the assembled battery 10 and an ammeter 170 that sequentially measures the charge / discharge current value Ib of the assembled battery 10. Have. The ECU 150 acquires (detects) the voltage value Vb measured by the voltmeter 160 and the charging / discharging current value Ib measured by the ammeter 170, integrates the charging / discharging current value, and the assembled battery 10 (the battery 1 forming this). ) Is calculated.

  As shown in FIG. 3, the assembled battery 10 has rectangular parallelepiped batteries 1, 1,... Stacked in its own thickness direction (left and right direction in FIG. 3), and substantially plate-shaped multiples stacked on the battery 1. A surface pressure sensor 30 and a compression structure 20 that compresses each battery 1 by sandwiching them in the stacking direction (left and right direction in the figure) are provided. The batteries 1 and 1 adjacent to each other are electrically connected via the bus bar 11, and the batteries 1 are electrically connected in series.

First, the battery 1 will be described. As shown in FIG. 4, the battery 1 includes an electrode body 2, a rectangular parallelepiped battery case 3 that accommodates the electrode body 2 and the like, one end of which is welded to the electrode body 2, and the other end of the battery case 3. It has a positive electrode terminal member 4 and a negative electrode terminal member 5 that extend outward.
Of these, the electrode body 2 is a flat plate formed by winding a belt-like positive electrode plate 6 and a belt-like negative electrode plate 7 around the axis 2X through a belt-like separator 8 and then compressing them to form a flat shape. This is a wound electrode body. A positive electrode active material layer (not shown) made of a positive electrode active material (for example, lithium-containing oxide) capable of reversibly occluding / releasing lithium ions is formed on the positive electrode plate 6. In addition, a negative electrode active material layer (not shown) made of a negative electrode active material (for example, graphite) capable of reversibly occluding / releasing lithium ions is formed on the negative electrode plate 7.

The electrode body 2 is accommodated in the battery case 3. The battery case 3 has a rectangular parallelepiped shape made of aluminum, and includes a rectangular parallelepiped case main body 3H having an open upper end and a lid 3F that hermetically closes the opening by laser welding. The positive terminal member 4 and the negative terminal member 5 penetrate through the lid 3F. Note that a seal insulator 9 is interposed between the lid 3F and the positive terminal member 4 and the negative terminal member 5 so as to be airtight. In the battery case 3, a nonaqueous electrolytic solution containing a lithium compound such as LiPF ₆ is held.
In the battery case 3, a pair of plate-like case main surfaces 3 </ b> A and 3 </ b> B orthogonal to the thickness direction DT of the electrode body 2 has a positive electrode plate 6 and a negative electrode plate 7 in the thickness direction DT of the electrode body 2. The thickness direction battery part 2B which overlaps through the separator 8 and performs a battery action is in contact from the inside.

  Next, the compression structure 20 will be described (see FIG. 3). The compression structure 20 includes a pair of generally rectangular flat plate-shaped compression plates 21 and 21, a plurality of restraining bolts 22 and 22 that connect them, and nuts 24 and 24. The compression plates 21 and 21 are respectively arranged on both sides of a plurality of batteries 1 and 1 arranged in a form in which the case main surfaces 3A and 3B of each battery 1 are parallel to each other. It is sandwiched. Using the compression bolts 22 and 22 and nuts 24 and 24, the compression plates 21 and 21 are tightened so that the interval between the compression plates 21 and 21 is narrowed, and the batteries 1 and 1 are also in the thickness direction (in FIG. Compressed horizontally. Thereby, among the electrode bodies 20 and 20 in each of the batteries 1 and 1, the thickness direction battery portion 3B is also compressed in the thickness direction DT (left and right direction in FIG. 3).

Next, the multiple surface pressure sensor 30 will be described (see FIG. 3). The multiple surface pressure sensor 30 includes a battery 1 (specifically, a battery 1 located at the left end in FIG. 3) and a compression plate 21 (specifically, a compression plate 21 on the right side in FIG. 3). Arranged between. The multiple surface pressure sensor 30 (sensor sheet Model 5101 manufactured by Nitta Corporation) has a shape in which a strip-shaped lead extends from a substantially rectangular plate-shaped detection unit. This multiple surface pressure sensor is provided with a large number of surface pressure sensors (44 × 44 = 1936) in a grid form at intervals of 1.0 mm within a measurement range of 44 × 44 mm. Thus, the surface pressure (local surface pressure Pp) applied to each part of the thickness direction battery part 2B of the electrode body 2 is detected.
As shown in FIG. 1, in the multiple surface pressure sensor 30, the measurement results of the local surface pressure Pp at a large number of measurement positions are input to the ECU 150 via the sensor connector (Versa Tek Handles) 31. Thus, the ECU 150 can use a large number of measurement results of the local surface pressure Pp.

  Next, a high rate is applied to a single battery 1 in which multiple surface pressure sensors 30 are stacked and compressed by the above-described compression structure 20 (the number of batteries constituting the assembled battery 10 shown in FIG. 3 is one). A cycle discharge test was performed to deteriorate the battery 1. The test conditions for this high-rate cycle discharge test are 10,000 cycles under the environment of 25 ° C., with the assembled battery 10 (or the battery 1) being 30C10 second discharge and 5C60 second charge as one cycle.

  FIG. 5 shows the result of investigating the distribution of the local surface pressure Pp applied to each part of the thickness direction battery part 2B of the electrode body 2 with the overall SOCh being SOCh = 30% for the battery 1 in this deteriorated state. . In FIG. 5, among the acquired many local surface pressures Pp, the axial direction DX along the axis 2 </ b> X of the axial part (not shown) through which the axis 2 </ b> X of the battery 2 </ b> B in the thickness direction of the electrode body 2 passes. The local surface pressure Pp for every axial position X (range X1-X2) about (refer FIG. 4) is shown. Of the axial position X, the positions X1 and X2 correspond to the end of the thickness direction battery portion 2B in the axial direction DX. The position X3 corresponds to the central portion of the thickness direction battery portion 2B in the axial direction DX.

  From the graph of FIG. 5, in the battery 1 deteriorated by the high-rate cycle discharge test, the local surface pressure Pp applied to each part of the thickness direction battery part 2B of the electrode body 2 is equal to both ends (positions X1, X2) of the axial direction DX. ) It is understood that the distribution is a substantially W-shaped distribution that is high in the vicinity of the central portion (position X3) and low in the vicinity thereof. In the battery 1 in the initial state before deterioration, the local surface pressure Pp was substantially uniform in the axial direction DX. Therefore, the local surface pressure Pp for the battery 1 has changed as described above due to the deterioration by the high rate cycle discharge test.

  Next, the battery 1 with SOCh = 30% was disassembled and the local SOCp was measured. The result is shown in FIG. 6 also shows the local SOCp for each axial position X (range X1 to X2) among the local SOCp.

  From the graph of FIG. 6, in the battery 1 deteriorated by the high-rate cycle discharge test, the local SOCp in each part of the thickness direction battery part 2B of the electrode body 2 is near both end parts (positions X1, X2) of the axial direction DX and It can be seen that the distribution is a substantially M-shaped distribution that is low near the center (position X3) and high between them. That is, it can be seen that the local surface pressure Pp has a vertically inverted distribution. In the battery 1 in the initial state before deterioration, it is known that the local SOCp is also substantially uniform in the axial direction DX. Therefore, the local SOCp for the battery 1 has changed as described above due to the deterioration by the high-rate cycle discharge test.

From this, it can be seen that in the battery 1 deteriorated by the high-rate cycle discharge test, the distribution of the local surface pressure Pp and the distribution of the local SOCp have an inverse correlation. Therefore, regarding the battery 1 and, as a result, the assembled battery 10 using the battery 1 (see FIG. 3), when the local surface pressure Pp varies (for example, a W-shaped distribution), Also, it can be inferred that the local SOCp distribution also varies (for example, an M-shaped distribution).
When there is a large variation in the distribution of local SOCp in this way, as described above, in such a battery, when the battery capacity that can be actually used (SOCh = 0% to 100%) is changed. , The amount of electricity that is actually charged or discharged) is reduced.

On the other hand, a technique for recovering (relaxing) the distribution of the local surface pressure Pp (local SOCp) in a uniform direction with respect to the battery 1 in which the distribution of the local surface pressure Pp (local SOCp) is greatly varied as described above. Has come to understand.
Specifically, first, the overall SOCh of the battery 1 is set to a relatively low value (20 to 50%, for example, 30%), and then slowly discharged with a discharge current of 2C or less. It is discharged to an overdischarge state of 0% to -30%, for example, -20%. Thereafter, the battery is slowly charged with a charging current of 2 C or less, and the total SOCh is returned to a state of 20 to 50%. Hereinafter, such charge / discharge may be referred to as relaxation charge / discharge.
In this way, the battery 1 in which the local surface pressure Pp distribution has a variation (for example, in a W shape), and thus the local surface pressure Pp distribution has a variation (for example, an M shape). , The size of the variation can be reduced.

For example, in FIG. 9, for another battery 1 deteriorated by the high-rate cycle discharge test, the local position for each axial position X (range X1 to X2) in the axial position in the state where the total SOCh is set to SOCh = 30%. The distribution of the surface pressure Pp is shown by a graph connected by thin lines.
On the other hand, this battery 1 was subjected to relaxation charge / discharge thereafter. Specifically, SOCh = 30%, and thereafter, discharging is performed at a discharge current Id = 1C, and the entire SOCh is discharged to an overdischarge state where SOCh = −20%. Thereafter, charging is performed with a charging current of charging current Ic = 1C, and the entire SOCh is returned to a state where SOCh = 30%. The subsequent distribution of the local surface pressure Pp is also shown in FIG. 9 as a graph connected with a thick line.

According to FIG. 9, after the relaxation charge / discharge (thick line), compared with before the relaxation charge / discharge (thin line), the variation in the distribution of the local surface pressure Pp is alleviated, and the uniform surface pressure distribution is achieved. It turns out that it is approaching. In addition, it has been found that the battery capacity that can be actually used increases (recovers) in the battery after the relaxation charge / discharge.
This is because, as shown in FIG. 9, the distribution of the local surface pressure Pp can be made closer to uniform by relaxation charging / discharging, and the distribution of the local SOCp is also made closer to uniform, so that the battery capacity that can actually be used is Seems to have recovered.
In addition, the graph shown in FIG.5, FIG6 and FIG.9 is a result at the time of compressing the single battery 1 with the compression structure 20. FIG. However, it was also found that each battery 1 in the assembled battery 10 using the plurality of batteries 1 and 1 shown in FIG.

Therefore, in the battery system 300 of the present embodiment, the ECU 150 performs the following detection of local surface pressure Pp distribution and execution and control of relaxation charge / discharge (see FIGS. 7 and 8).
When drive switch 220 is turned off to drive vehicle 100, ECU 150 starts executing the surface pressure distribution evaluation-relaxation charge / discharge routine shown in FIG. 7 in parallel with other controls.
First, in step S1, it is determined whether or not external charging has started. Specifically, the driver determines whether or not the so-called plug-in charging is started by connecting the charging device 133 to the external power source GD through the plug 134. If No, step S1 is repeated.

On the other hand, if it is determined Yes in step S1, the process proceeds to step S2, and it is determined whether or not it is time to inspect the distribution of the local surface pressure Pp. Specifically, it is determined whether or not three months have passed since the previous distribution inspection timing was performed. Note that the inspection timing may be determined based on the elapsed time from the previous inspection, the travel distance, the accumulated amount of electricity charged (or discharged) in the assembled battery 10 (battery 1), and the like.
In step S2, if No (inspection timing has not arrived), the process proceeds to step S14. This is because it is not necessary to measure the distribution of the local surface pressure Pp described later. On the other hand, if Yes (inspection timing has arrived), the process proceeds to step S3.

In step S3, the repetition number n is initialized to n = 0. Next, in steps S4 and S5, adjustment is made so that the total SOCh of the assembled battery 10 (battery 1) becomes the reference SOCh. Specifically, the assembled battery 10 (battery 1) is charged or discharged, and the entire SOCh of the assembled battery 10 is aligned with the reference SOCh. The reference SOCh may be a value within the range of SOCh = 20 to 50%, and in this embodiment, SOCh = 30%.
In step S5, when the total SOCh of the assembled battery 10 (battery 1) becomes the reference SOCh (Yes), the process proceeds to step S6, and the multiple surface pressure sensor 30 is connected to the multiple surface pressure sensor 30 through the sensor connector 31. The instruction | indication which measures the local surface pressure Pp in each site | part of the thickness direction battery part 2B is output. In step S7, the ECU 150 acquires the local surface pressure Pp of each part measured by the multiple surface pressure sensor 30 through the sensor connector 31, and proceeds to step S8.

In step S8, the distribution of the acquired local surface pressure Pp is evaluated. As an evaluation method, pass / fail (OK / NG) is evaluated based on whether or not the variation in the distribution of the acquired local surface pressure Pp is large. More specifically, the maximum value Ppmax and the minimum value Ppmin are selected from the acquired local surface pressures Pp, and the fluctuation range Dp (= Pmax−Pmin), which is the difference between the two, is smaller than the threshold value Dpt. (Dp <Dpt) is OK. On the other hand, when the magnitude is greater than or equal to the threshold (Dp ≧ Dpt), it is determined as NG. Here, when it determines with OK, it progresses to step S14.
In addition, as an evaluation method in S8, in addition, the standard deviation σ (or variance σ ² ) of variation of each acquired local surface pressure Pp is acquired, and OK when this standard deviation σ is smaller than a predetermined threshold value. It can also be judged.

On the other hand, if it is determined as NG in step S8, the process proceeds to step S9, where the repetition number n is incremented by one, and further, in step S10, it is determined whether the repetition number n is 3 or more.
Here, if n <3 (No), the process proceeds to the relaxation charge / discharge subroutine of step S11. On the other hand, if n ≧ 3, that is, if the distribution of local surface pressure Pp is NG (large variation) even after three times of relaxation charge / discharge described later, the process proceeds to step S13 and the local surface pressure Pp is increased. A signal for warning the distribution abnormality is output, and a lamp or the like for warning the abnormality (deterioration) of the assembled battery 10 mounted on the vehicle is turned on, and the process proceeds to step S14.

Next, the subroutine of step S11 will be described with reference to FIG. First, in step S111, it is determined whether 10 minutes have elapsed. That is, it waits for 10 minutes after the entire SOCh of the assembled battery 10 is set to the reference SOCh (in this embodiment, the reference SOCh = 30%).
This is to temporarily settle the state of the assembled battery 10 (battery 1).

Next, in step S112, from the state of the starting SOCh = 30%, the battery pack 10 (battery 1) is discharged at a constant current with a discharge current Id of Id = 1C. 1C indicates the magnitude of the discharge current Id (or charge current Ic) that can discharge (or charge) the amount of electricity of the rated capacity (SOCh = 100 to 0%) in one hour.
In step S113, the total SOCh of the assembled battery 10 becomes the voltage value Vb of the battery 1 corresponding to a value of overdischarge SOCh = 0 to −30% (specifically, −20% in the present embodiment). In the case of No, the process returns to step S112, and the assembled battery 10 is overdischarged until the total SOCh of the assembled battery 10 reaches the lower limit discharge SOCh = −20%.

  Thereafter, in step S114, the battery pack 10 is charged with a constant current with a charging current Ic of Ic = 1C. Furthermore, in step S115, whether or not the total SOCh of the assembled battery 10 has reached the voltage value Vb of the battery 1 corresponding to a value of SOCh = 20 to 50% (specifically, 30% in the present embodiment). Check out. In No, it returns to step S114 and performs constant current charge to the assembled battery 10 until the total SOCh of the assembled battery 10 reaches the start SOCh = 30%.

In this relaxation charging / discharging subroutine S11, the assembled battery 10 (battery 1) is once discharged to a state of overdischarge (lower limit discharge SOCh) with a relatively low discharge current Id, and thereafter with a relatively low charge current Ic. , Temporarily charge / discharge is performed to return to the original state of charge (start SOCh).
Thereby, about each battery 1 of the assembled battery 10, the variation in distribution of local surface pressure Pp can be approximated to a uniform state (refer FIG. 9).

  When the subroutine of step S11 is completed, the process returns to step S6, the local surface pressure Pp is measured again (step S7), and the distribution is evaluated (step S8). If it is determined as NG in step S8, as described above, the above-described relaxation charge / discharge is performed up to three times. On the other hand, as described above, if it is determined in step S8 that the evaluation is OK (local surface pressure variation is small), the process proceeds to step S14.

In step S14, normal external charging is performed. That is, since the vehicle 100 is a plug-in hybrid vehicle, charging is performed until SOCh = 100%.
In the present embodiment, the ECU 150 that executes steps S4 and S5 corresponds to the standardization means. Moreover, ECU150 which performs step S7 is equivalent to an acquisition means. In addition, the ECU 150 that executes step S8 corresponds to a distribution evaluation unit, a determination unit, and a fluctuation range determination unit. Further, the ECU 150 that executes step S11 (steps S111 to S115) corresponds to a relaxation charge / discharge unit and an overdischarge charge unit.

As described above, the battery system 300 includes the acquisition unit S7 that acquires the local surface pressure Pp applied to each part in the thickness direction battery unit 2B, and the distribution evaluation unit S8 that evaluates the distribution state of the local surface pressure Pp. ing.
Thereby, the local surface pressure Pp of each site | part can be acquired, and the distribution condition (for example, the presence or absence of variation, the magnitude of variation etc.) of local surface pressure Pp can be evaluated using this. Therefore, the distribution state of the local SOCp can be grasped from the distribution state of the local surface pressure Pp.
Furthermore, appropriate measures such as a response according to the distribution state of the local surface pressure Pp (therefore, the local SOCp), for example, relaxation charging / discharging described in step S11 and a distribution abnormality warning described in step S13 are taken. be able to.
In addition, as a countermeasure, the drive condition (charge / discharge condition) when using the assembled battery 10 (battery 1) is changed to a pattern in which the variation in the distribution of the local surface pressure Pp is difficult to progress or a pattern in which the variation is recovered. It is also possible to do.

  In addition, in the battery system 300 described above, when the determination unit S8 determines that the variation in the distribution of the local surface pressure Pp is large, the pattern for reducing the variation in the distribution of the local surface pressure Pp by the relaxation charge / discharge unit S11. Charge and discharge at. For this reason, the variation in the distribution of the local surface pressure Pp of the assembled battery 10 (battery 1) is alleviated. At the same time, the variation in the distribution of the local SOCp of the battery 1 is also mitigated, and the capacity of the assembled battery 10 (battery 1) is recovered. Can be made.

  Furthermore, in the battery system 300, when the fluctuation range Dp of the local surface pressure Pp exceeds the threshold value Dpt, the fluctuation range determination unit S8 determines that the variation in the distribution of the local surface pressure Pp is large. In this way, the process for obtaining the fluctuation range Dp is easy, and the variation in the distribution of the local surface pressure Pp can be easily and reliably determined.

  Furthermore, in this battery system 300, the overdischarge charging means S11, which is a relaxation charging means, is discharged to a state of overdischarge with a relatively small current of 1C, and further charged to a start SOCh with a relatively small current of 1C. For this reason, the variation in local SOCp generated in the electrode body 2 can be reliably relaxed and uniformed, and the battery capacity can be recovered.

  In this battery system 300, since the SOCh of the battery 1 is set as the reference SOCh prior to the acquisition of the local surface pressure Pp by the standardization means S4, S5, the local surface pressure Pp in the same battery state can be acquired. The distribution status of the pressure Pp can be easily evaluated.

In addition, as described above, the plug-in hybrid vehicle (vehicle) 100 according to the present embodiment includes the battery system 300 (ECU 150 and the like), and includes the assembled battery 10 (batteries 1 and 1). The electric energy stored in 10 is used as all or part of the driving energy of the driving source (see FIG. 1).
Therefore, in this vehicle 100, it is possible to detect a variation in the distribution of the local surface pressure Pp of the assembled battery 10 (battery 1), and a vehicle that can take appropriate measures such as relaxation charge / discharge and output of a distribution abnormality warning corresponding thereto. It has become.

In the above, the electronic system of the present invention has been described according to the embodiment. However, the present invention is not limited to the above-described embodiment, and it can be applied as appropriate without departing from the spirit of the present invention. Nor.
For example, in the present embodiment, the battery 1 having the flat wound electrode body 2 is shown, but the present invention can also be applied to a stacked battery.
Moreover, in this embodiment, although the example which applied this invention about the example which comprised the some battery 1 and 1 as one assembled battery 10 was shown, you may apply this invention about the single battery 1. FIG. .

300 Battery system 1 Battery (secondary battery, battery system)
2 Electrode body 2B Thickness direction battery portion DT (Electrode body) Thickness direction DX Axial direction 3 Battery case 3A, 3B Case main surface 9 Seal insulator 10 Battery 11 Bus bar 20 Compression structure 21 Compression plate 22 Compression bolt 24 Nut 30 Multiple surface pressure sensor (surface pressure sensor)
31 Sensor connector X, X1, X2, X3 Axial direction position Pp Local surface pressure Ppmax (Local surface pressure) Maximum value Ppmin (Local surface pressure) Minimum value Dp Fluctuation width Dpt Threshold value Id Discharge current Ic Charge current 100 Plug In-hybrid vehicle (vehicle)
134 Plug 150 ECU (battery system)
153 Voltage value detection unit (voltage value detection means)
154 Current value detection unit (current value detection means)
15C Charge / Discharge Control Unit 160 Voltmeter 170 Ammeter 220 Drive Switch Vb Voltage Value Ib Current Value (Charge / Discharge Current Value)
GD External power supply n Number of repetitions

Claims (5)

One or a plurality of flat wound or stacked electrode bodies, and a rectangular parallelepiped battery case containing the electrode bodies, including a pair of flat plate case main surfaces orthogonal to the thickness direction of the electrode bodies A secondary battery,
About one secondary battery or each of the plurality of secondary batteries arranged in a form in which their case main surfaces are parallel to each other, through the pair of case main surfaces of the battery case, A compression structure that is configured to compress the thickness direction battery part that performs the battery action by overlapping the positive electrode plate and the negative electrode plate in the thickness direction through the separator in the thickness direction,
The case main surface is disposed in contact with the case main surface of the battery case in the one secondary battery or in any one of the plurality of secondary batteries, and the compression structure provides the case main surface. A plate-like surface pressure sensor that detects the magnitude of the local surface pressure applied to each part in the thickness direction battery part of the electrode body,
Detected by the upper Symbol surface pressure sensor, and obtaining means for obtaining the local surface pressure applied to each site in the thickness direction battery portion of the electrode body,
A battery evaluation system comprising: a distribution evaluation unit that evaluates a distribution state of the local surface pressure of each part. The battery system according to claim 1,
The distribution evaluation means includes
Determining means for determining the variation of the local surface pressure,
A battery system having relaxation charge / discharge means for charging / discharging the secondary battery in a pattern that reduces the variation of the local surface pressure when the determination means determines that the variation of the local surface pressure is large. . The battery system according to claim 2,
The determination means includes
A battery system which is a fluctuation range determination unit that determines that the variation of the local surface pressure is large when a fluctuation range obtained by subtracting a minimum value from the maximum value of the acquired local surface pressure exceeds a threshold value. The battery system according to claim 2 or claim 3,
The relaxation charge / discharge means
The secondary battery,
From a starting SOC predetermined within the range of SOC = 20-50%,
With a discharge current of 2C or less, overdischarge to the lower limit discharge SOC within the range of SOC = 0 to -30%,
Thereafter, the battery system is an overdischarge charging means for charging up to the start SOC with a charging current of 2C or less. The battery system according to any one of claims 1 to 4, wherein
Prior to the acquisition of the local surface pressure by the acquisition unit, a battery system including a standardization unit that sets the SOC of the secondary battery to a predetermined reference SOC within a range of SOC = 20 to 50%.

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