JP2018116884A - Battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery system comprising a laminate type battery, capable of improving estimation accuracy of an inner resistance of the laminate type battery.SOLUTION: A battery system 90 includes a bipolar battery 1 and an ECU 100. The bipolar battery 1 includes a plurality of battery cells 10 in which a positive electrode plate 43 and a negative electrode plate 45 are laminated in a lamination direction Z through a separator 43. The ECU 100 is constructed so as to calculate an inner resistance R1 of a region from a temperature in each of a plurality of regions X1 to X10 obtained by virtually dividing the battery cells 10 along the laminate direction Z, and estimate the inner part resistance of each battery cell 10 by synthesizing an inner resistance R2 of the plurality of regions to be calculated.SELECTED DRAWING: Figure 7

Description

  The present disclosure relates to a battery system, and more specifically to a technique for estimating an internal resistance of a stacked battery.

  Generally, the internal resistance of a battery is used for battery abnormality detection and SOC (State Of Charge) estimation. In order to improve battery abnormality detection accuracy and SOC estimation accuracy, it is required to estimate the internal resistance of the battery with high accuracy.

  Since there is a correlation between the internal resistance of the battery and the temperature, the internal resistance can be estimated from the temperature of the battery. For example, a battery device disclosed in Japanese Patent Application Laid-Open No. 2007-311065 (Patent Document 1) includes a plurality of battery cells and a plurality of temperature sensors. According to this battery device, the internal resistance of the battery cell is acquired based on the temperature detected by the temperature sensor for each of a plurality of areas divided so as to include at least one of each of the battery cell and the temperature sensor. (For example, refer to FIG. 4 of Patent Document 1). Thereby, it is possible to estimate the internal resistance in consideration of the temperature variation between the plurality of battery cells.

JP 2007-311065 A

  In recent years, for example, it has been proposed to use a battery system including a stacked battery as a battery system for driving a vehicle. The stacked battery is, for example, a bipolar battery, and includes a plurality of battery cells in which a positive electrode plate and a negative electrode plate are stacked in a stacking direction via separators.

  In Patent Document 1, a general lithium ion secondary battery (that is, not having a laminated structure) is employed. In this case, the influence of temperature variation generated between a plurality of cells is significant. Therefore, it is effective to estimate the internal resistance of the battery cell based on the temperature of each battery cell.

  On the other hand, in many cases, in the stacked battery, the area of the battery cell is larger than that of a general battery, and can be, for example, several tens of cm square. Therefore, temperature distribution (temperature variation) may occur in the same battery cell. In the battery device disclosed in Patent Document 1, no consideration is given to the influence of the temperature distribution that may occur in such a stacked battery.

  The present disclosure has been made to solve the above-described problems, and an object thereof is to provide a technique capable of improving the estimation accuracy of internal resistance in a battery system including a stacked battery.

  A battery system according to an aspect of the present disclosure includes a stacked battery and an estimation device. A stacked battery includes a plurality of battery cells in which a positive electrode plate and a negative electrode plate are stacked in a stacking direction via a separator. The estimation device calculates the internal resistance of the region from the temperature of the region for each of the plurality of regions obtained by virtually dividing the battery cell along the stacking direction, and combines the calculated internal resistances of the plurality of regions. It is configured to estimate the internal resistance of the battery cell.

  According to the above configuration, the battery cell is virtually divided into a plurality of regions, and the temperature of each region is obtained. For each region, the internal resistance is calculated from the temperature, and the internal resistance of the entire battery cell is estimated by combining the internal resistances of a plurality of regions (for example, all regions). Thus, the estimation accuracy of the internal resistance of the battery cell can be improved by considering the temperature distribution in the battery cell.

  According to the present disclosure, it is possible to improve the estimation accuracy of internal resistance in a battery system including a stacked battery.

It is a figure which shows typically the electric vehicle carrying the battery system which concerns on this Embodiment. It is sectional drawing of a bipolar battery. It is a disassembled perspective view of a bipolar battery. It is a figure which shows typically the assembly process of a laminated body. It is a perspective view which shows a cell. It is a top view which shows a cell. It is a flowchart for demonstrating the internal resistance estimation process in this Embodiment. It is a schematic diagram for demonstrating the division | segmentation method of the cell in this Embodiment. It is a figure which shows an example of the acquisition result of the temperature of the area | regions X1-X10 of a cell. It is a figure which shows an example of the correlation established between temperature and temperature resistance. It is a figure which shows an example of the estimation result of the internal resistance of the area | regions X1-X10 of a cell. It is a figure for demonstrating the division | segmentation method of the cell in a modification.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  Hereinafter, a configuration in which a battery system including a bipolar battery as an example of a stacked battery is mounted on an electric vehicle will be described as an example. An electric vehicle means a hybrid vehicle, an electric vehicle, or a fuel cell vehicle. However, the use of the battery system is not limited to vehicles, and may be stationary.

[Embodiment]
<Overall configuration of electric vehicle>
FIG. 1 is a diagram schematically showing an electric vehicle equipped with the battery system according to the present embodiment. A battery system 90 is mounted on the vehicle 9. The battery system 90 controls a plurality of bipolar batteries 1, a battery case 2 that houses the plurality of bipolar batteries 1, a fan 3 that supplies cooling air into the battery case 2, and charging / discharging of the plurality of bipolar batteries 1. An electronic control unit (ECU) 100 is provided.

  Each of the plurality of bipolar batteries 1 includes, for example, a plurality of cells 10 (see FIG. 2) of nickel metal hydride batteries. Each bipolar battery 1 stores electric power used for running the vehicle 9 and supplies the electric power to a power control device (not shown) of the motor generator as required.

  ECU 100 includes a CPU (Central Processing Unit), a memory, and an input / output buffer (none of which are shown). ECU 100 causes vehicle 9 to be in a desired state based on signals received from various sensors (all not shown) including a voltage sensor, a current sensor, and a temperature sensor, and a map and a program stored in memory. Control each device. A main process executed by the ECU 100 includes a process for estimating internal resistances of the plurality of bipolar batteries 1. This “internal resistance estimation process” will be described in detail later. The ECU 100 corresponds to an “estimation device” according to the present disclosure.

<Schematic configuration of bipolar battery>
Since each bipolar battery 1 has the same configuration, one bipolar battery 1 will be representatively described below.

  FIG. 2 is a cross-sectional view of the bipolar battery 1. FIG. 3 is an exploded perspective view of the bipolar battery 1. Referring to FIG. 2, bipolar battery 1 includes a stacked body 11 and a restraining tool 12.

  The stacked body 11 is formed by stacking a plurality of cells (battery cells) 10 in the stacking direction Z. The stacked body 11 includes an end surface 13 and an end surface 14 arranged in the stacking direction Z. The number of stacked cells 10 is, for example, about 50.

  The restraining tool 12 restrains the stacked body 11 in the stacking direction Z. The restraining tool 12 includes a metal pressing plate 20 that presses the end surface 13, a metal pressing plate 21 that presses the end surface 14, and a plurality of connection members 23 that connect the pressing plate 20 and the pressing plate 21.

  A plurality of through holes 24 are formed in the pressing plate 20, and a plurality of through holes 25 are also formed in the pressing plate 21.

  The connecting member 23 includes a connecting shaft 26 disposed between the pressing plate 20 and the pressing plate 21, a bolt 27 that connects one end of the connecting shaft 26 to the pressing plate 20, and the other end of the connecting shaft 26 to the pressing plate 21. A bolt 28 to be connected and insulating members 29 and 30 are included.

  The insulating member 29 is formed with a through hole into which the shaft portion of the bolt 27 is inserted. The insulating member 29 includes a cylindrical tube portion 31 that is inserted into the through hole 24, and a flange portion 32 that is formed at the lower end portion of the tube portion 31. The collar portion 32 is disposed on the lower surface of the pressing plate 20.

  The insulating member 29 is a member that insulates the pressing plate 20 and the bolt 27, the flange portion 32 insulates the pressing plate 20 and the head portion of the bolt 27, and the cylindrical portion 31 is the shaft of the pressing plate 20 and the bolt 27. Insulate between parts. The insulating member 30 is also configured in the same manner as the insulating member 29, and includes a cylindrical portion 33 that is inserted into the through hole 25 and a flange portion 34 that is disposed on the upper surface of the pressing plate 21. The insulating member 30 insulates the pressing plate 21 and the bolt 28.

  At one end of the connection shaft 26, a female screw portion that is screwed with the shaft portion of the bolt 27 is formed. At the other end of the connecting shaft 26, a female screw portion that is screwed with the shaft portion of the bolt 28 is formed. The pressing plates 20 and 21 press the end surfaces 13 and 14 of the laminated body 11 by screwing the bolts 27 and 28 to the connecting shaft 26 and tightening the bolts 27 and 28.

  Since the insulating members 29 and 30 insulate the pressing plates 20 and 21 and the bolts 27 and 28, the connecting shaft 26 is insulated from the pressing plates 20 and 21. The pressing plate 20 and the pressing plate 21 are electrically connected to the laminate 11, while the connection shaft 26 is insulated from the pressing plates 20 and 21. Therefore, a short circuit between the pressing plate 20 and the pressing plate 21 is suppressed. In addition, the pressing plate 20 and the pressing plate 21 can be used as current collecting terminals.

  With reference to FIG. 3, the connection shafts 26 are arranged at intervals so as to surround the periphery of the stacked body 11. For this reason, the cooling air from the fan 3 passes between the connecting shafts 26 and reaches the laminated body 11 to cool the laminated body 11. That is, the laminate 11 is exposed to the outside air, and the heat of the laminate 11 can be directly radiated to the outside air.

  Returning to FIG. 2, the cell 10 is disposed on the current collector plate 40 including the upper surface 35 and the lower surface 36 arranged in the stacking direction Z, the electrode layer 41 disposed on the upper surface 35 of the current collector plate 40, and the upper surface 35. And a seal member 42 formed so as to surround the periphery of the electrode layer 41. The cell 10 further includes seal members 53 and 54 formed on the outer peripheral surface of the seal member 42 and hydrophobic insulating films 55 and 56 formed inside the seal member 42.

  The current collector plate 40 is, for example, a metal plate such as a nickel plate or a nickel-plated steel plate. Since the current collecting plate 40 has a certain thickness, even when the plurality of current collecting plates 40 are arranged at intervals, the outer peripheral edge portion of the current collecting plate 40 is suppressed from being bent.

  The electrode layer 41 includes a separator 44 including an upper surface 46 and a lower surface 47 arranged in the stacking direction Z, a negative electrode 45 disposed on the upper surface 46, and a positive electrode 43 disposed on the lower surface 47.

  FIG. 4 is a diagram schematically showing an assembly process of the laminate 11. As shown in FIG. 4, the laminate 11 is formed by alternately laminating bipolar electrodes 17 and separators 44. The bipolar electrode 17 includes a current collector plate 40, a positive electrode 43 formed on the upper surface 35 of the current collector plate 40, and a negative electrode 45 formed on the lower surface 36 of the current collector plate 40. Further, a seal member 42 and a hydrophobic insulating film 55 are formed on the upper surface 35 of each current collector plate 40. A hydrophobic insulating film 56 is formed on the lower surface 36 of each current collector plate 40.

  When the bipolar electrode 17 and the separator 44 are sequentially laminated, the positive electrode 43, the separator 44 disposed on the upper surface of the positive electrode 43, and the negative electrode disposed on the upper surface of the separator 44 between the current collecting plates 40 adjacent in the stacking direction Z. 45, the electrode layer 41 is formed. The cell 10 is formed by the electrode layer 41, the seal member 42, the hydrophobic insulating film 55, and the hydrophobic insulating film 56.

The positive electrode 43 includes a positive electrode active material, a conductive material, and a binder. The positive electrode active material is, for example, nickel hydroxide (Ni (OH) ₂ ). The conductive material is, for example, cobalt oxide (CoO) or cobalt hydroxide (Co (OH) ₂ ). The binder is, for example, carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), or polytetrafluoroethylene (PTFE). The negative electrode 45 includes a hydrogen storage alloy. The separator 44 is, for example, a polyolefin nonwoven fabric. The separator 44 is impregnated with an electrolytic solution. The electrolytic solution is, for example, a potassium hydroxide (KOH) aqueous solution.

  FIG. 5 is a perspective view showing the cell 10. As shown in FIG. 5, the separator 44 is the largest in the electrode layer 41, and the entire outer periphery of the separator 44 protrudes outward from the outer periphery of the positive electrode 43 and the negative electrode 45.

  The seal member 42 is formed in a loop shape so as to surround the periphery of the cell 10. The seal member 42 includes a loop-shaped resin frame 50, a loop-shaped resin frame 51 disposed inside the resin frame 50, and a gasket 52 disposed between the resin frame 50 and the resin frame 51.

  The gasket 52 is formed of a resin having long-term high airtightness, excellent heat resistance, chemical resistance, and electrical insulation. Examples of such a resin include a polyarylene sulfide resin, a thermoplastic elastomer, or a polyarylene sulfide resin.

  As described with reference to FIG. 2, the sealing member 42 is sandwiched between the two current collector plates 40 adjacent to each other in the stacking direction Z by the pressing force applied to the stacked body 11 by the restraining tool 12. The height of the gasket 52 is lower than the height in the natural state due to the clamping force applied from the two current collector plates 40, and the gasket 52 is in close contact with the current collector plates 40 adjacent in the stacking direction Z. ing. Thereby, it is suppressed that the electrolyte solution of the electrode layer 41 leaks outside.

  Further, the cell 10 includes seal members 53 and 54 formed on the outer peripheral surface of the resin frame 50. The resin frame 50 is sandwiched between two current collector plates 40 adjacent to each other in the stacking direction Z, and the seal member 53 is looped so as to fill a corner formed by the one current collector plate 40 and the resin frame 50. It is formed in a shape. The seal member 54 is formed so as to fill a corner formed by the other current collector plate 40 and the resin frame 50. Thereby, the sealing property of electrolyte solution is improved.

  FIG. 6 is a plan view showing the cell 10. More specifically, FIG. 6 shows a plan view when the current collector plate 40, the seal member 42, and the like are viewed from positions separated in the stacking direction Z. In FIG. 6, the negative electrode 45 is not shown. The length of the cell 10 in the X direction is, for example, about 40 cm, and the length in the Y direction is, for example, about 30 cm.

  As shown in FIG. 6, the cell 10 includes a hydrophobic insulating film 55 formed on the upper surface 35 so as to surround the electrode layer 41. The hydrophobic insulating film 55 is made of a hydrophobic material such as a fluoropolymer or a similar material.

  The outer peripheral edge portion of the hydrophobic insulating film 55 is located outside the outer peripheral edge portion of the separator 44, and the outer peripheral edge portion of the separator 44 is located on the hydrophobic insulating film 55. For this reason, even if the electrolytic solution oozes out from the outer peripheral edge of the separator 44 onto the hydrophobic insulating film 55, it is repelled by the hydrophobic insulating film 55 having hydrophobicity. As a result, the electrolyte impregnated in the separator 44 is difficult to leak from the separator 44, and the electrolyte can be prevented from reaching the seal member 42. Thereby, it can suppress that electrolyte solution leaks outside.

  The seal member 42 is formed in a square shape, and includes a side surface 60 and a side surface 61 arranged in the Y direction, and a side surface 62 and a side surface 63 arranged in the X direction. The current collector plate 40 includes a proximity portion 70 that extends along the side surface 60 and a proximity portion 71 that extends along the side surface 61. Furthermore, the current collector plate 40 includes an overhang portion 72 that projects outward from the side surface 62 and an overhang portion 73 that projects outward from the side surface 63.

<Internal resistance estimation processing>
In the bipolar battery 1 configured as described above, the area of the cell 10 is larger than that of a general battery. For this reason, not only the temperature distribution (temperature variation) among the plurality of cells 10 but also the influence of the temperature distribution can occur in the same cell 10.

  Therefore, in the present embodiment, “internal resistance estimation processing” for estimating the internal resistance of bipolar battery 1 (or cell 10) in consideration of the influence of the temperature distribution peculiar to such a bipolar battery is executed. . Hereinafter, the internal resistance estimation process in the present embodiment will be described in detail.

  FIG. 7 is a flowchart for explaining the internal resistance estimation processing in the present embodiment. This flowchart is called from a main routine (not shown) and executed every time a predetermined condition is satisfied or every time a predetermined calculation cycle elapses. Each step (hereinafter abbreviated as “S”) included in this flowchart is basically realized by software processing by the ECU 100, but is realized by dedicated hardware (electric circuit) produced in the ECU 100. May be.

  In S10, the ECU 100 virtually divides the cell 10 (or the electrode layer 41) into a plurality of regions along the stacking direction Z. How to divide the cell 10 is determined in advance based on the results of experiments or simulations.

  FIG. 8 is a schematic diagram for explaining a cell 10 division method according to the present embodiment. In the present embodiment, an example will be described in which the cell 10 is virtually divided into 10 regions by a plurality of planes (not shown) extending in the Z direction and arranged in the X direction. As shown in FIG. 8, by assigning region numbers (X1 to X10), the divided regions are distinguished from each other. In the present embodiment, the regions X1 to X10 are divided so that all the regions X1 to X10 have the same volume. Note that the number of divisions of the region is not limited to 10, and any number of 2 or more can be adopted.

  Returning to FIG. 7, in S20, the ECU 100 acquires the temperatures of the respective regions X1 to X10. This temperature acquisition method will be described in more detail.

  In the regions X1 to X10 of the electrode layer 41, there are a region where the temperature easily changes and a region where the temperature hardly changes. For example, in a region (for example, X1 and X10) located at the end of the electrode layer 41, heat can be directly radiated to the outside air, and heat exchange with the outside tends to occur. Therefore, a temperature change is more likely to occur in the region located at the end of the electrode layer 41 than in the region located inside (for example, X5 and X6). Such a relative temperature relationship between the regions X1 to X10 can be obtained in advance by experiments or the like. Then, by actually measuring the temperature of several regions (for example, the end regions X1 and X10 and the central region X5) with a temperature sensor (not shown), The temperature of the remaining area can be estimated. For example, one temperature sensor may be provided for each of the regions X1 to X10, and the temperature of each region X1 to X10 may be directly measured.

  FIG. 9 is a diagram illustrating an example of an acquisition result of the temperatures of the regions X1 to X10 of the cell 10. In FIG. 9, the horizontal axis indicates region numbers (X1 to X10), and the vertical axis indicates the temperature of each region X1 to X10. For example, as shown in FIG. 9, the temperature distribution of each area | region X1-X10 is acquirable.

  Returning to FIG. 7, in S30, the ECU 100 estimates the internal resistance Ra of each of the regions X1 to X10 from the temperature of each of the regions X1 to X10. For this estimation, a map in which a correlation established between the temperature and the internal resistance is obtained in advance by experiments or the like can be used. FIG. 10 shows an example of a correlation established between temperature and temperature resistance.

  FIG. 11 is a diagram illustrating an example of an estimation result of the internal resistance Ra of the regions X1 to X10 of the cell 10. As illustrated in FIG. In FIG. 11, the horizontal axis represents region numbers (X1 to X10), and the vertical axis represents the internal resistance of each region X1 to X10. From the temperature distribution shown in FIG. 9 and the correlation shown in FIG. 10, the distribution of the internal resistance Ra in each of the regions X1 to X10 can be estimated as shown in FIG.

  Returning to FIG. 7, the internal resistance (synthetic resistance) Rb of the entire cell 10 can be considered as the internal resistances R1 of all the regions X1 to X10 being connected in parallel to each other. Therefore, in S40, the ECU 100 synthesizes the internal resistance Ra of each of the regions X1 to X10 calculated in S30 (more specifically, the reciprocal of the internal resistance of each region is added according to a known formula, and the reciprocal thereof The internal resistance Rb of the cell 10 is calculated.

  In S50, the ECU 100 determines whether an abnormality in the internal resistance Rb of the cell 10 has occurred based on the internal resistance Rb calculated in S40. Specifically, ECU 100 determines that cell 10 is normal (S70) when internal resistance Rb calculated in S40 is less than a predetermined threshold value Rth (NO in S50), and internal resistance Rb is If it is equal to or greater than threshold value Rth (YES in S50), it is determined that an abnormality has occurred in cell 10 (S60).

  As described above, according to the present embodiment, the cell 10 (electrode layer 41) is divided into the plurality of regions X1 to X10, and the temperature distribution in the cell 10 is obtained. From the temperature distribution, the internal resistance Ra of each of the regions X1 to X10 is further calculated, and the internal resistance Rb of the entire cell 10 is estimated by combining the internal resistances of all the regions X1 to X10. Thus, the estimation accuracy of the internal resistance of the cell 10 (and consequently the bipolar battery 1) can be improved by taking into account the temperature distribution in the cell 10.

  In addition, a technique for estimating the SOC from the open circuit voltage (OCV) of the battery is widely used. In this technique, the OCV is obtained by taking the difference between the terminal voltage measured by the voltage sensor and the overvoltage. Is calculated. The overvoltage is obtained by the product of current and internal resistance. In S50, the SOC of the cell 10 may be estimated instead of detecting the abnormality of the cell 10. That is, the overvoltage may be calculated from the input / output current measured by the current sensor and the internal resistance Rb calculated in S40, thereby calculating the OCV. The SOC can be estimated from the OCV by preparing a map showing the correlation between the OCV and the SOC in advance.

[Modification]
Although FIG. 8 illustrates an example in which the cell 10 is virtually divided equally so that the volumes of all the regions X1 to X10 are equal, the cell dividing method is not limited to this.

  FIG. 12 is a diagram for explaining a cell 10A division method according to the modification. As described above, in the region (X1 or X10) located at the end portion, heat exchange with the outside is likely to occur compared to the region (eg, X5, X10) located in the center portion, and thus a temperature change is likely to occur ( A temperature gradient is likely to occur). Therefore, in the modified example, the cell 10A is divided so that the volume of the region becomes smaller from the center to the end.

  In this modification, as shown in FIG. 12, the volume of one or a plurality of regions located at the end where temperature change is likely to occur is relatively reduced, in other words, a diagram showing the temperature distribution for each region (FIG. 9) is made smaller toward the end. Thereby, it becomes possible to reflect the temperature change of the said area | region in the temperature distribution of the whole area | region in detail. As a result, the temperature estimation accuracy can be improved, and consequently the internal resistance estimation accuracy can be improved.

  From another point of view, the improvement in the estimation accuracy of the internal resistance compared to the division method described in FIG. 8 means that the number of divisions required to achieve the equivalent estimation accuracy of the internal resistance is reduced. Means that it is possible. Therefore, the calculation load on the ECU 100 can be reduced.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present disclosure is shown not by the above description of the embodiments but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

  DESCRIPTION OF SYMBOLS 1 Bipolar battery, 2 Battery case, 3 Fan, 9 Vehicle, 10 cell, 11 Laminated body, 12 Restraint tool, 13, 14 End surface, 17 Bipolar electrode, 20, 21 Press plate, 23 Connection member, 24, 25 Through-hole, 26, connecting shaft, 27, 28 bolt, 29, 30 insulating member, 31, 33 tube, 32, 34 collar, 35, 46 upper surface, 36, 47 lower surface, 40 current collector plate, 41 electrode layer, 42, 53, 54 Seal member, 43 Positive electrode, 44 Separator, 45 Negative electrode, 50, 51 Resin frame, 52 Gasket, 55, 56 Hydrophobic insulating film, 60-63 Side surface, 70, 71 Proximity part, 72, 73 Overhang part, 90 Battery system.

Claims (1)

A stacked battery including a plurality of battery cells in which a positive electrode plate and a negative electrode plate are stacked in a stacking direction via a separator;
By calculating the internal resistance of the region from the temperature of the region for each of a plurality of regions virtually divided the battery cells along the stacking direction, and by combining the calculated internal resistance of the plurality of regions A battery system comprising: an estimation device configured to estimate an internal resistance of a battery cell.