JP6363529B2 - Battery control device - Google Patents

Description

  A battery control device that controls a lithium ion secondary battery, and estimates a state of the lithium ion secondary battery based on a heat flux generated by charging and discharging.

  For example, as in the configuration described in Patent Document 1, there is known a device that detects the heat flow on the surface of the battery and detects the state of the battery based on the detected value of the heat flow. This device measures changes in heat flux due to battery deterioration and predicts battery life.

JP 2014-92428 A

  The inventors have discovered that in a lithium ion secondary battery, when one of high rate discharge or high rate charge is repeatedly performed and an excessive discharge state or an excessive charge state occurs, the lithium ion concentration in the electrode is biased. Here, the high rate discharge is to perform discharge by increasing the current flowing in the lithium ion secondary battery compared to the normal discharge, and the high rate charge is lithium ion secondary compared to the normal charge. Charging is performed by increasing the current flowing through the secondary battery.

  There is a concern that when the concentration of lithium ions is biased, lithium ions reaching the negative electrode from the positive electrode decrease, and the output voltage of the lithium ion secondary battery decreases. This bias of the lithium ion concentration is temporary and is different from the battery deterioration of the above-mentioned patent document.

  The main object of the present invention is to estimate a lithium ion concentration distribution generated in an excessive discharge state or an excessive charge state in a lithium ion secondary battery.

  The present invention provides a battery control device (41) for a lithium ion secondary battery (10, C1 to C8) including stacked electrodes (16, 17), wherein the lithium ion secondary battery includes the lithium ion secondary battery. A plurality of heat flux sensors (S1 to S3, SA to SD) for detecting a heat flux from the secondary battery to the outside of the lithium ion secondary battery are provided in the lithium ion secondary battery parallel to the stacking direction of the electrodes. The heat generation distribution of the lithium ion secondary battery is calculated based on detection values of the plurality of heat flux sensors, and is provided so as to cover at least one of the two surfaces. An estimation means (40) for estimating the lithium ion concentration distribution is provided.

  In the electrode of the lithium ion secondary battery, the resistance value is higher at a location where the lithium ion concentration is low than at a location where the lithium ion concentration is high. Since a voltage is uniformly applied between the positive electrode and the negative electrode, a large current flows in a portion having a small resistance value compared to a portion having a large resistance value. For this reason, the calorific value becomes large in the location where the lithium ion concentration is high compared to the location where the lithium ion concentration is low. The heat flux from the lithium ion battery toward the outside of the lithium ion battery increases as the heat generation amount increases. Therefore, it is possible to calculate the heat generation distribution in the lithium ion secondary battery based on the detection value of the heat flux sensor, and to estimate the lithium ion concentration distribution based on the calculation result.

The figure showing the structure of a secondary battery. The figure showing the structure of an electrode body. The figure showing the voltage change at the time of discharge in a different lithium ion density | concentration. The figure showing a lithium ion concentration distribution estimation system. The figure showing lithium ion concentration distribution, internal resistance distribution, and current distribution in an overcharge state. The figure showing the change of the emitted-heat amount in each area | region in an overcharge state, and the change of the emitted-heat amount deviation. The figure showing lithium ion concentration distribution, internal resistance distribution, and current distribution in an excessive discharge state. The figure showing the change of the emitted-heat amount in each area | region in an excessive discharge state, and the change of the emitted-heat amount deviation. The figure showing the structure of an assembled battery. The flowchart showing the lithium ion concentration distribution estimation control. The figure showing how to provide the heat flux sensor in a modification. The figure showing how to provide the heat flux sensor in a modification.

(First embodiment)
FIG. 1 shows a structure of a secondary battery 10 as a laminate type lithium ion secondary battery. The electrode body 11 and the electrolytic solution 12 are sealed by the laminate film 13, and the positive electrode terminal 14 and the negative electrode terminal 15 connected to the electrode body 11 protrude from the laminate film 13. The positive electrode terminal 14 is provided on a predetermined side of the rectangular plate-shaped secondary battery 10, and the negative electrode terminal 15 is provided on one side facing the predetermined side. The laminate film 13 is configured by, for example, using aluminum as a core material and laminating a resin such as polypropylene.

  FIG. 2 shows the structure of the electrode body 11. The electrode body 11 is configured by repeatedly laminating a positive electrode current collector foil 16, a separator 18, and a negative electrode current collector foil 17 in this order. The positive electrode current collector foil 16 is configured by holding a lithium ion compound, which is a positive electrode active material, on the surface of a current collector foil (for example, an aluminum foil). The negative electrode current collector foil 17 is configured by holding carbon as a negative electrode active material on the surface of the current collector foil. The positive electrode current collector foil 16 and the positive electrode active material, and the negative electrode current collector foil 17 and the negative electrode active material are specific examples of the “electrode”. The positive electrode terminal 14 is electrically connected to all the positive electrode current collector foils 16, and the negative electrode terminal 15 is electrically connected to all the negative electrode current collector foils 17.

  At the time of charging, lithium ions are released from the positive electrode active material of the positive electrode current collector foil 16, and the lithium ions are taken into the negative electrode active material of the negative electrode current collector foil 17 through the electrolytic solution 12. At the time of discharging, lithium ions are released from the negative electrode active material of the negative electrode current collector foil 17, and the lithium ions are taken into the positive electrode active material of the positive electrode current collector foil 16 through the electrolytic solution 12. The separator 18 prevents a short circuit due to contact between the positive electrode current collector foil 16 and the negative electrode current collector foil 17 and transmits lithium ions.

  Here, when charge and discharge are performed, lithium ions move from one of the electrodes (positive electrode active material and negative electrode active material) to the other. By releasing lithium ions, the electrode contracts, and by absorbing lithium ions, the electrode expands. By repeatedly performing charging and discharging, a deviation in lithium ion concentration around the center of the electrode occurs in the electrode. Due to the bias in the lithium ion concentration, there is a concern that during discharge, lithium ions reaching the positive electrode (positive electrode active material) from the negative electrode (negative electrode active material) will decrease, and the output voltage of the secondary battery will decrease.

  The inventors of the present application have found that the deviation of the lithium ion concentration is mainly caused by repeatedly performing either high rate discharge or high rate charge. Here, the high-rate discharge is to increase the current flowing through the secondary battery 10 to a predetermined value (for example, 10 times the current value) as compared with the normal discharge, and the high-rate charge is Compared with normal charging, charging is performed by increasing the current flowing through the secondary battery 10 to a predetermined value (for example, at a current value 10 times larger). The state in which the lithium ion concentration is biased by repeatedly performing high-rate discharge and normal charging is called an excessive discharge state, and the state in which the lithium ion concentration is biased by repeatedly performing high-rate charging and normal discharge is called. This is called an overcharged state.

  The bias of the lithium ion concentration in the overcharged state is eliminated by performing high-rate discharge, and the bias of the lithium ion concentration in the overcharged state is eliminated by performing high-rate charging.

  In order to verify the relationship between the lithium ion concentration and the output voltage of the secondary battery, the inventors of the present application manufactured a lithium ion concentration in the secondary battery that was increased and a lithium ion concentration that was decreased. And discharge was implemented in the secondary battery with a high lithium ion density | concentration, and the secondary battery with a low lithium ion density | concentration.

  FIG. 3 shows a voltage change during discharge (solid line) in a secondary battery having a high lithium ion concentration and a voltage change (broken line) during discharge in a secondary battery having a low lithium ion concentration. At the time of discharge, high rate discharge is performed.

  When discharging is performed in a secondary battery having a high lithium ion concentration, lithium ions that reach the positive electrode (positive electrode current collector foil 16) from the negative electrode (negative electrode current collector foil 16) do not run out, and the output voltage of the secondary battery The amount of decline is small. On the other hand, when discharging is performed in a secondary battery having a low lithium ion concentration, lithium ions reaching the positive electrode from the negative electrode gradually decrease. For this reason, when discharging is performed for a long time, the output voltage of the secondary battery rapidly decreases. The decrease in the output voltage of the secondary battery becomes significant during high rate discharge.

  In the actual usage environment of the secondary battery 10, the lithium ion concentration does not decrease over the entire area of the electrode, and thus it is considered that the output voltage does not decrease so much as shown in FIG. 3. However, there is a concern that the output voltage of the secondary battery may decrease due to the large deviation of the lithium ion concentration in the electrode.

  Here, in the part where the lithium ion concentration is low in the electrode, lithium ions are difficult to be supplied, so that the internal resistance at that part becomes large. Since almost the same voltage is applied between the positive electrode and the negative electrode in all portions, a large current flows in a portion where the internal resistance is small, and a small current flows in a portion where the internal resistance is large. The amount of heat generated at a portion where a large current flows increases, and the amount of heat generated at a portion where a small current flows decreases. For this reason, it is possible to acquire the lithium ion concentration distribution by detecting the heat generation distribution in the secondary battery.

  The inventors of the present application have verified the effectiveness of acquiring the lithium ion concentration distribution based on the above-described detection of the heat generation distribution using the configuration shown in FIG.

  In the configuration shown in FIG. 4, rubber plates 32 for adjusting the surface pressure are provided on both surfaces of the secondary battery 10. Then, heat flux sensors S1, S2, and S3 as heat flux detecting means are sandwiched between the secondary battery 10 and the rubber plate 32 so that the heat flux generated in the secondary battery 10 and directed to the outside can be detected. Is provided. Further, a restraining member 31 is provided so as to sandwich both rubber plates 32. The restraining member 31 is fastened by bolts 33 so that pressure is applied to both the rubber plates 32, the secondary battery 10, and the heat flux sensor S.

  Here, one of both surfaces (surface perpendicular to the electrode stacking direction) of the plate-like secondary battery 10 is divided into three equal parts in the longitudinal direction (the direction of the negative electrode terminal 15 with respect to the positive electrode terminal 14), and the three are divided into three equal parts. The heat flux sensors S1, S2, and S3 are provided in each of the regions A1, A2, and A3.

  The heat flux sensors S1, S2, and S3 are provided so as not to overlap each other and cover one surface of the secondary battery 10 by the three heat flux sensors S1, S2, and S3. The heat flux sensors S1, S2, S3 have the same area. The heat flux sensor S1 is provided in a region A1 around the positive electrode terminal 14 of the secondary battery 10, the heat flux sensor S2 is provided in a center region A2 of the secondary battery 10, and the heat flux sensor S3 is a secondary battery. It is provided in a region A3 around the negative electrode terminal 15 of the battery 10. That is, the heat flux sensors S <b> 1 and S <b> 3 detect the heat flux at the end of the secondary battery 10, and the heat flux sensor S <b> 2 detects the heat flux at the center of the secondary battery 10.

  Furthermore, voltage sensors 37, 38, 39 for detecting voltage values output from the heat flux sensors S1, S2, S3 are provided. The voltage value output by the heat flux sensors S1, S2, S3 is a value based on the temperature difference between both surfaces of the heat flux sensors S1, S2, S3. The battery control unit 40 acquires the detection values of the heat flux sensors S1, S2, and S3 based on the voltage values acquired from the voltage sensors 37, 38, and 39. Then, based on the detected value, the heat generation distribution of the secondary battery 10 is calculated. Here, the battery control unit 41 and the heat flux sensors S1 to S3 constitute a battery control device 41.

  In addition, a load 34 is connected to both terminals 14 and 15 of the secondary battery 10, and a current flows from the secondary battery 10 to the load 34. A current sensor 35 is provided as a current detection means on a path through which the current flows. In addition, a voltage sensor 36 is provided as voltage detection means so that the voltage between the terminals 14 and 15 (voltage between terminals of the secondary battery 10) can be detected. The detection values of the current sensor 35 and the voltage sensor 36 are acquired by the battery control unit 40. The battery control unit 40 performs charge / discharge control of the secondary battery 10 based on the detection values of the current sensor 35 and the voltage sensor 36. Furthermore, the battery control unit 40 eliminates the bias of the lithium ion concentration by performing high-rate discharge in the excessive charge state, and biases the lithium ion concentration by performing high-rate charge in the excessive discharge state.

  FIG. 5 shows the lithium ion concentration distribution, internal resistance distribution, and current distribution in the overcharged state. Here, the horizontal axis represents the position in the longitudinal direction of the secondary battery 10 (the direction of the negative electrode terminal 15 relative to the positive electrode terminal 14).

  As shown in FIG. 5 (a), the lithium ion concentration is low at the ends (regions A1, A3) of the secondary battery 10, and the lithium ion concentration is high at the center (region A2) of the secondary battery 10. It has become. As a result, as shown in FIG. 5B, the internal resistance increases at the end of the secondary battery 10, and the internal resistance decreases at the center of the secondary battery 10. As a result, as shown in FIG. 5C, the current is small at the end of the secondary battery 10, and the current is large at the center of the secondary battery 10.

  FIG. 6 shows a change in the amount of heat generated in each of the regions A1, A2, and A3 and a change in the amount of deviation | ΔQ | in the regions A1 and A2 when charging is performed in the normal state and the overcharged state.

  As shown in FIGS. 6A and 6C, in regions A1 and A3, when high-rate charging is continued, the amount of heat generated is smaller in the overcharged state (solid line) than in the normal state (broken line). On the other hand, as shown in FIG. 6B, in the region A2, when high rate charging is continued, the amount of heat generation is larger in the overcharged state (solid line) than in the normal state (broken line).

  For this reason, as shown in FIG. 6D, when the high rate charging is continued, the deviation | ΔQ | between the heat generation amount in the region A1 and the heat generation amount in the region A2 increases and exceeds the threshold Th. Based on the fact that the calorific value deviation | ΔQ | exceeds the threshold Th, it can be determined that the concentration of lithium ions is uneven.

  FIG. 7 shows a lithium ion concentration distribution, an internal resistance distribution, and a current distribution in an excessive discharge state. Here, the horizontal axis represents the position in the longitudinal direction of the secondary battery 10 (the direction of the negative electrode terminal 15 relative to the positive electrode terminal 14).

  As shown in FIG. 7A, the lithium ion concentration is high at the end portions (regions A1 and A3) of the secondary battery 10, and the lithium ion concentration is low at the center portion (region A2) of the secondary battery 10. It has become. Thereby, as shown in FIG. 5B, the internal resistance is reduced at the end of the secondary battery 10, and the internal resistance is increased at the center of the secondary battery 10. As a result, as shown in FIG. 5C, the current increases at the end of the secondary battery 10, and the current decreases at the center of the secondary battery 10.

  FIG. 8 shows a change in the amount of heat generated in each of the regions A1, A2, and A3 and a change in the deviation | ΔQ | in the amount of generated heat in the regions A1 and A2 when discharging is performed in the normal state and the excessive discharge state.

  As shown in FIGS. 8A and 8C, in the regions A1 and A3, when the high rate discharge is continued, the amount of heat generation is larger in the excessive discharge state (solid line) than in the normal state (broken line). On the other hand, as shown in FIG. 8B, in the region A2, when the high rate discharge is continued, the amount of heat generation is smaller in the excessive discharge state (solid line) than in the normal state (broken line).

  For this reason, as shown in FIG. 8D, when the high rate discharge is continued, the deviation | ΔQ | between the heat generation amount in the region A1 and the heat generation amount in the region A2 increases and exceeds the threshold Th. Then, based on the fact that the deviation | ΔQ | of the calorific value exceeds the threshold Th, it can be determined that the concentration of lithium ions is uneven.

  FIG. 9 shows a specific example in the case of using the method for estimating the lithium ion concentration distribution of the present embodiment for the configuration of the assembled battery 20 including a plurality of secondary batteries 10 (battery cells C1 to C8). The assembled battery 20 includes eight battery cells C1 to C8, and the battery cells C1 to C8 are stacked in the same direction as the stacking direction of the electrodes included in the battery cells C1 to C8. Moreover, the assembled battery 20 is restrained by sandwiching both end surfaces of the assembled battery 20 between the restraining members 21 in the electrode stacking direction. In addition, each battery cell C1-C8 is connected in series.

  In addition, for each of the two battery cells, a single heat conduction plate through which heat generated in the battery cells is conducted is provided. Specifically, the heat conduction plate BA between the battery cells C1 and C2, the heat conduction plate BB between the battery cells C3 and C4, the heat conduction plate BC and the battery cells C7 and C8 between the battery cells C5 and C6. A heat conduction plate BD is provided between each of them.

  The heat conductive plates BA to BD are provided so as to cover one surface of the adjacent battery cells C1 to C8. Further, the heat conductive plates BA to BD are connected to the cooler 22. The heat conductive plates BA to BD absorb heat from the two adjacent battery cells and dissipate the heat to the cooler 22 to cool the two battery cells. For example, the heat conducting plate BA absorbs heat from the adjacent battery cells C1 and C2. That is, heat generated in the battery cells C1 to C8 by charging and discharging in the battery cells C1 to C8 flows from the battery cells C1 to C8 to the cooler 22 via the heat conduction plates BA to BD. The cooler 22 is a cooling fin provided in the case of the assembled battery 20. The cooler 22 as the heat exchange device may be a water cooling jacket or the like.

  As described above, the heat generated in the battery cells C1 to C8 is transmitted to the cooler 22 via the heat conductive plates BA to BD. Therefore, heat flux sensors SA1 to SA3, SB1 to SB3, SC1 to SC3, SD1 to SD3 are provided so as to be sandwiched between the battery cells C1, C3, C6 and C8 and the heat conducting plates BA to BD. The heat flux sensors SA1 to SA3, SB1 to SB3, SC1 to SC3, SD1 to SD3 are provided so as to be in contact with the battery cells C1, C3, C6, and C8 and to face the electrodes of the battery cells C1, C3, C6, and C8. It has been. The heat flux sensors SA1 to SA3, SB1 to SB3, SC1 to SC3, SD1 to SD3 are arranged in the same manner as the heat flux sensors S1 to S3 of FIG. Hereinafter, for simplification of description, the heat flux sensors SA1 to SA3 are collectively referred to as a heat flux sensor group SA, and the heat flux sensors SB1 to SB3, SC1 to SC3, and SD1 to SD3 are similarly respectively heat flux sensors. Called groups SB, SC, SD.

  By acquiring the detection values of the heat flux sensor groups SA to SD, it is possible to calculate the lithium ion concentration distribution of each of the battery cells C1, C3, C6, and C8. The heat flux sensor groups SA to SD are provided so as to cover one surface of each of the battery cells C1, C3, C6, and C8. Specifically, the heat flux sensors SA1 to SA3 are sandwiched between the battery cell C1 and the heat conductive plate BA. Compared to the restraining member 21, the heat flux sensors SA1 to SA3 and the heat conduction plate BA have sufficiently large thermal conductivities, so that most of the heat generated in the battery cell C1 is the heat flux sensors SA1 to SA3 and the heat conduction plate BA. Flowing into. For this reason, the heat generation distribution of the battery cell C1 can be calculated from the detection values of the heat flux sensors SA1 to SA3.

  Further, the heat flux sensors SB1 to SB3 are sandwiched between the battery cell C3 and the heat conductive plate BB. Here, the battery cell C3 is in contact with the battery cell C2, but the temperature difference at the boundary between the battery cell C3 and the battery cell C2 is sufficiently smaller than the temperature difference between the battery cell C2 and the heat conduction plate BA. Therefore, the heat generated in the battery cell C2 flows to the heat conduction plate BA. That is, a heat insulation boundary is generated on the surface where the battery cell C2 and the battery cell C3 are in contact with each other. Thereby, only the heat generated in the battery cell C3 is conducted to the heat flux sensors SB1 to SB3. For this reason, the heat generation distribution of the battery cell C3 can be accurately estimated using the detection values of the heat flux sensors SB1 to SB3.

  Similarly, the heat flux sensors SC1 to SC3 are sandwiched between the battery cell C6 and the heat conduction plate BC, and detect the heat flux from the battery cell C6 toward the heat conduction plate BC. Further, the heat flux sensors SD1 to SD3 are sandwiched between the battery cell C8 and the heat conduction plate BD, and detect the heat flux from the battery cell C8 toward the heat conduction plate BD. The heat generation distribution of the battery cell C6 can be estimated using the detection values of the heat flux sensors SC1 to SC3, and the heat generation distribution of the battery cell C8 can be estimated using the detection values of the heat flux sensors SD1 to SD4.

  Here, similarly to the configuration shown in FIG. 4, the battery control unit 40 as the estimation means provided in the assembled battery 20 acquires the detection values of the heat flux sensor groups SA to SD. Based on this detection value, the battery control unit 40 calculates the amount of heat generated by the battery cells C1, C3, C6, and C8, and estimates the lithium ion concentration distribution based on the calculation result. Similarly to the configuration shown in FIG. 4, a voltage sensor 36 that detects the inter-terminal voltage V is provided for each of the battery cells C1, C3, C6, and C8. A current sensor 35 to be detected is provided, and the battery control unit 40 as charge / discharge control means performs charge / discharge control of the assembled battery 20. The heat flux sensor groups SA to SD and the battery control unit 40 constitute a battery control device 41.

  FIG. 10 is a flowchart showing lithium ion concentration distribution calculation control performed by the battery control unit 40.

  In step S1, it is determined whether high-rate discharge is being performed. If it is determined that high-rate discharge is being performed (S1: YES), the calorific value deviation | ΔQ | of each of the battery cells C1, C3, C6, and C8 is acquired in step S2. In step S3, it is determined whether any one of the calorific value deviations | ΔQ | of the battery cells C1, C3, C6, and C8 exceeds the threshold Th.

  If any one of the calorific value deviations | ΔQ | of the battery cells C1, C3, C6, and C8 exceeds the threshold value Th (S3: YES), it is determined in step S4 that the lithium ion concentration is biased. To do. In step S5, in order to eliminate the unevenness of the lithium ion concentration, a high rate charge is instructed, and then the process ends. Further, when the calorific value deviation | ΔQ | of all the battery cells C1, C3, C6, and C8 is equal to or less than the threshold value Th (S3: NO), the processing is ended as it is.

  If it is determined that high-rate discharge is not being performed (S1: NO), it is determined in step S6 whether high-rate charging is being performed. If it is determined that neither high-rate discharge nor high-rate charge is performed (S6: NO), the process is terminated as it is.

  When it is determined that high-rate discharge is being performed (S6: YES), in step S7, the calorific value deviation | ΔQ | of each of the battery cells C1, C3, C6, and C8 is acquired. In step S8, it is determined whether any one of the calorific value deviations | ΔQ | of the battery cells C1, C3, C6, and C8 exceeds the threshold Th. Further, when the calorific value deviation | ΔQ | of all the battery cells C1, C3, C6, and C8 is equal to or less than the threshold value Th (S3: NO), the processing is ended as it is.

  If any one of the calorific value deviations | ΔQ | of the battery cells C1, C3, C6, and C8 exceeds the threshold value Th (S8: YES), it is determined in step S9 that the lithium ion concentration is biased. To do. In step S10, in order to eliminate the unevenness of the lithium ion concentration, a high-rate discharge is instructed, and then the process ends.

  The effects of this embodiment will be described below.

  In the electrode of the secondary battery 10, the resistance value is higher at a location where the lithium ion concentration is low than at a location where the lithium ion concentration is high. Since the same voltage is applied between the positive electrode and the negative electrode, a larger current flows in a portion having a small resistance value than in a portion having a large resistance value. For this reason, the calorific value becomes large in the location where the lithium ion concentration is high compared to the location where the lithium ion concentration is low. The heat flux from the secondary battery 10 toward the outside of the secondary battery 10 increases as the amount of heat generation increases. Therefore, the heat flux sensors S1, S2, and S3 are provided on at least one of the two surfaces of the lithium ion secondary battery parallel to the electrode stacking direction. Then, it is possible to calculate the heat generation distribution in the secondary battery 10 based on the detection values of the heat flux sensors S1, S2, S3, and to estimate the lithium ion concentration distribution based on the calculation result.

  In the present embodiment, as shown in FIG. 9, heat conductive plates BA to BD are provided for each of the battery cells C1, C3, C6, and C8 that are targets for estimation of the lithium ion concentration distribution. By adopting such a configuration, most of the heat generated in the battery cells C1, C3, C6, and C8 is conducted to the heat conductive plates BA to BD, and cooling can be performed efficiently. . Further, the heat flux sensor groups SA to SD are provided so as to be sandwiched between the battery cells C1, C3, C6 and C8 and the heat conducting plates BA to BD. As a result, most of the heat generated in the battery cells C1, C3, C6, and C8 is conducted to the heat flux sensor groups SA to SD, respectively, and the heat generation distribution of the battery cells C1, C3, C6, and C8 is accurately determined. It becomes possible to detect well.

  The bias of the lithium ion concentration caused by the excessive charge state is eliminated by performing the high rate discharge, and the bias of the lithium ion concentration caused by the excessive discharge state is eliminated by performing the high rate charge. Then, based on the estimation result of the lithium ion concentration distribution using the detection values of the heat flux sensor groups SA to SD, the bias of the lithium ion concentration is eliminated by performing high rate discharge or high rate charge in the assembled battery 20. Can do.

  Specifically, in an overcharged state, the lithium ion concentration distribution at the center of the electrode is high, and as a result, when charging is performed, the amount of heat generated at the center of the electrode increases. In particular, when high-rate charging is performed in an overcharged state, the deviation | ΔQ | between the heat generation amount at the electrode end and the heat generation amount at the center of the electrode becomes significant. Therefore, during high-rate charging, when the deviation | ΔQ | between the amount of heat generated at the center of the electrode and the amount of heat generated at the electrode end is greater than a predetermined threshold Th, high-rate discharging is performed to eliminate the overcharged state. The configuration.

  Further, in the excessive discharge state, the lithium ion concentration distribution at the electrode end becomes high, and as a result, when the discharge is performed, the amount of heat generated at the electrode end becomes large. In particular, when high-rate discharge is performed in an excessive discharge state, the deviation between the amount of heat generated at the electrode end and the amount of heat generated at the center of the electrode becomes significant. Therefore, during the high-rate discharge, when the deviation | ΔQ | between the calorific value at the electrode end and the calorific value at the center of the electrode is larger than a predetermined threshold Th, high-rate charging is performed to eliminate the excessive discharge state. The configuration.

  When the assembled battery 20 is configured by stacking a plurality of battery cells C1 to C8, the cooling performance of the battery cells C1 to C8 becomes a problem. In the configuration of the present embodiment, since the heat conductive plates BA to BD are provided for the battery cells C1 to C8, the battery cells C1 to C8 are efficiently cooled. Furthermore, it becomes possible to detect a heat flux accurately for every battery cell C1-C8. Thereby, when excessive charge or excessive discharge has occurred in some battery cells, it becomes possible to estimate the deviation of the lithium ion concentration due to excessive charge or excessive discharge.

  Battery cells C1 to C8 are laminated lithium ion secondary batteries. Laminate type lithium ion secondary batteries are more easily deformed than square can type lithium ion secondary batteries. Therefore, it is easy to be in close contact with the heat flux sensor groups SA to SD. For this reason, heat is efficiently conducted from the battery cells C1, C3, C6, and C8 to the heat conduction plates BA to BD via the heat flux sensor groups SA to SD, and the heat flux is accurately detected. Cooling to C8 can be performed efficiently.

(Other embodiments)
In the above embodiment, one surface of the rectangular plate-shaped secondary battery 10 is divided into three regions A1, A2, and A3 as shown in FIG. 4, and the heat flux sensors S1, S2, and S3 are divided into the regions A1, A2, and A3, respectively. S3 is provided. By changing this, one surface of the rectangular plate-shaped secondary battery 10 may be divided into six regions as shown in FIG. 11, and the heat flux sensors S11 to S16 may be provided in each region. Here, one surface of the secondary battery 10 is divided into six regions by dividing it into three equal parts in the longitudinal direction and two equal parts in the short direction.

  Further, as shown in FIG. 12, one surface of the rectangular plate-shaped secondary battery 10 may be divided into nine regions, and the heat flux sensors S21 to S29 may be provided in each region. Here, one surface of the secondary battery 10 is divided into nine regions by dividing it into three equal parts in the longitudinal direction and three equal parts in the short direction.

  Since the deviation of the lithium ion concentration occurs radially around the center of the electrode, in addition to the heat generation distribution in the longitudinal direction, the calculation of the heat generation distribution in the short direction can be used to calculate the lithium ion concentration bias more accurately. It becomes possible to estimate.

  Moreover, it is good also as a structure which provides a heat flux sensor in any one area | region of area | region A1, A3 while providing a heat flux sensor in area | region A2 which is a predetermined area | region including the center of a rectangular plate.

  In the secondary battery 10 of the above embodiment, the positive electrode terminal 14 is provided on a predetermined side of the rectangular plate-shaped secondary battery 10, and the negative electrode terminal 15 is provided on one side facing the predetermined side. For example, the positive electrode terminal and the negative electrode terminal may be provided adjacent to each other on the same side of the rectangular plate-shaped secondary battery.

  In the above embodiment, the lithium ion concentration distribution is estimated when high rate discharge or high rate charge is performed. However, this may be changed. For example, the lithium ion concentration distribution may be estimated during normal discharge or normal charge. Further, in order to estimate the lithium ion concentration distribution, one of high rate discharge and high rate charge may be performed at a predetermined interval, and the lithium ion concentration distribution may be estimated during the execution.

  In the above-described embodiment, the heat flux sensor groups SA to SD are provided in the four battery cells C1, C3, C6, and C8 among the eight battery cells C1 to C8. , C3, C6, and C8, the heat flux sensor group may be provided on each of two surfaces perpendicular to the stacking direction. In addition, among the battery cells C1 to C8 included in the assembled battery 20, only C1, C3, C6, and C8 are targets for estimation of the lithium concentration distribution, but this is changed, and all the battery cells C1 to C8 are replaced with the lithium concentration distribution. It is good also as an estimation object.

  Further, one of the battery cells C1 to C8 may be an estimation target of the lithium concentration distribution. In this case, any one of the battery cells C3 to C6 at the center in the stacking direction of the battery cells C1 to C8 may be an estimation target of the lithium ion concentration distribution. In the battery cells C3 to C6 in the center in the stacking direction, the pressure generated by the restraining member 21 is equalized on a plane perpendicular to the stacking direction of the battery cells C1 to C8. For this reason, the adhesiveness between the heat flux sensor and the battery cell is good, the heat flux can be detected with high accuracy, and as a result, the lithium ion concentration distribution can be accurately estimated.

  -In the said embodiment, although the battery cells C1-C8 with which the assembled battery 20 were equipped were made into the object of lithium ion concentration distribution estimation, this was changed and the single battery comprised from one battery cell of lithium ion concentration distribution was changed. It may be an estimation target.

  -In 1st, 2nd embodiment, although it was set as the structure which provides one sheet of heat conductive plates so that it may be pinched | interposed into two adjacent battery cells, this is changed and 2 perpendicular | vertical to the lamination direction of battery cell C1-C8. It is good also as a structure which each provides a heat conductive board in both surfaces of a surface. In this case, it is preferable that a heat flux sensor group be provided on each of the two heat conductive plates in one battery cell.

  The threshold value Th used for the determination of the excessive charge state and the threshold value Th used for the determination of the excessive discharge state may be different values.

  -It is good also as a structure which abbreviate | omits the high-rate discharge after determining with an overcharge state, and the high-rate charge after determining with an excessive discharge state.

  In the above embodiment, the heat flux sensor is provided so as to cover one surface of the battery cells C1, C3, C6, and C8, but this may be changed. For example, one surface of the battery cells C1, C3, C6, and C8 may be divided into three regions, and a heat flux sensor may be provided in a part of each region. In this case, on one surface of the battery cells C1, C3, C6, and C8 provided with the heat flux sensor, an auxiliary plate having the same thickness and the same thermal conductivity as the heat flux sensor is provided in a region where the heat flux sensor is not provided. It may be configured. The battery cells C1, C3, C6, and C8 can be cooled by the heat conductive plates BA to BD through the auxiliary plate. In this configuration, the amount of heat generated in each region can be calculated by correcting the output value of the heat flux sensor according to the areas of the heat flux sensor and the auxiliary plate.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery (lithium ion secondary battery), 16 ... Positive electrode current collector foil, 17 ... Negative electrode current collector foil, 40 ... Battery control part (estimation means), 41 ... Battery control apparatus, C1-C8 ... Battery cell ( Lithium ion secondary battery), S1 to S3 ... heat flux sensor, SA to SD ... heat flux sensor group.

Claims (9)

A battery control device (41) for a lithium ion secondary battery (10, C1-C8) including stacked electrodes (16, 17),
The lithium ion secondary battery includes a plurality of heat flux sensors (S1 to S3, SA to SD) for detecting a heat flux from the lithium ion secondary battery to the outside of the lithium ion secondary battery. Provided on at least one of the two surfaces of the lithium ion secondary battery parallel to the stacking direction;
An estimation means (40) for calculating a heat generation distribution of the lithium ion secondary battery based on detection values of the plurality of heat flux sensors and estimating a lithium ion concentration distribution in the electrode based on the calculation result. A battery control device. The lithium ion secondary battery includes
A heat conduction plate (BA to BD) provided on at least one of the two surfaces of the lithium ion secondary battery parallel to the stacking direction of the electrodes to conduct heat generated in the lithium ion secondary battery is provided. And
The plurality of heat flux sensors (SA to SD) are sandwiched between the lithium ion secondary battery and the heat conduction plate, respectively, and measure the heat flux from the lithium ion secondary battery toward the heat conduction plate. The battery control device according to claim 1, wherein each of the battery control devices is detected.   Charge / discharge control means (40) for performing charge / discharge in the lithium ion secondary battery by increasing the current flowing in the lithium ion secondary battery based on the estimation result of the lithium ion concentration distribution by the estimation means. The battery control device according to claim 1, comprising the battery control device.   The charge / discharge control means is configured to charge a current flowing in the lithium ion secondary battery when a deviation between a heat generation amount at a center portion of the electrode and a heat generation amount at an end portion of the electrode is larger than a predetermined threshold during charging. The battery control device according to claim 3, wherein the secondary battery is discharged by increasing   The charge / discharge control means is configured to discharge a current flowing through the lithium ion secondary battery when a deviation between a heat generation amount at a center portion of the electrode and a heat generation amount at an end portion of the electrode is larger than a predetermined threshold during discharge. The battery control device according to claim 3, wherein the secondary battery is charged by increasing the value.   The battery control device according to claim 1, wherein the plurality of secondary batteries are stacked in the stacking direction of the electrodes to form an assembled battery (20).   The battery control apparatus according to any one of claims 1 to 6, wherein the lithium ion secondary battery is a laminated lithium ion secondary battery. The lithium ion secondary battery has a rectangular plate shape, a positive electrode terminal (14) is provided on a predetermined side of the rectangular plate, and a negative electrode terminal (15) is provided on a side opposite to the predetermined side,
In at least one of the two surfaces of the lithium ion secondary battery parallel to the electrode stacking direction, each of a predetermined region (A2) including the center of the rectangular plate and another region (A1.A3) On the other hand, the battery control device according to claim 7, wherein the heat flux sensor is provided.   In at least one of the two surfaces of the lithium ion secondary battery parallel to the electrode stacking direction, a region (A1) around the positive terminal, a region (A3) around the negative terminal, and the rectangle The battery control device according to claim 8, wherein the heat flux sensor is provided for each of the central regions (A2) of the plate.

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