Battery system

Abstract

This battery system comprises: a battery pack obtained by stacking a plurality of pouch-type battery cells in which battery materials, including electrodes and an electrolyte, are sealed in an exterior casing having a flat shape; a plurality of heat exchangers having a flat shape, each of which is disposed between a corresponding battery cell among the plurality of battery cells and which exchanges heat with the corresponding battery cell; a plurality of thermoelectric conversion elements, each of which is connected to a corresponding heat exchanger among the plurality of heat exchangers; and a control device that, on the basis of the temperatures of the plurality of battery cells, controls the amount of electric charge passed through each of the plurality of thermoelectric conversion elements.

Description

Battery System

[0001] The present disclosure relates to a battery system.

[0002] The drive batteries of electric vehicles need to be properly temperature-controlled to ensure they perform at their best.

[0003] For example, Patent Document 1 discloses a battery module having at least two batteries, a thermoelectric conversion element disposed between the two batteries and having a first surface and a second surface that perform opposing functions of heat dissipation and heat absorption depending on the polarity of current flow, and a heat exchanger disposed between at least one of the two batteries and the thermoelectric conversion element and performs heat exchange with an inflowing heat medium, the first surface being thermally connected to one of the two batteries and the second surface being thermally connected to the heat exchanger.

[0004] JP 2013-161710 A

[0005] Cooling methods for battery packs used to power electric vehicles are mainly classified as air-cooling and water-cooling. In air-cooling, air channels are provided between the multiple battery cells in the battery pack, and cooled air passes through these channels. To ensure the air passes through at the lowest possible temperature, cooled air is often drawn in from the bottom of the vehicle cabin or from an air conditioner. After cooling the battery cells, the air is exhausted outside the vehicle. Space is required outside the battery pack to accommodate a cooling fan and intake / exhaust ducts. To improve cooling capacity, it is necessary to widen the channel through which the cooled air passes and increase the cooling fan's output, but this increases the space required for the battery system and the power consumption of the cooling fan. In contrast, in water-cooling, a cooling plate, which is kept cooler than the battery cells by coolant, is placed under the battery pack, and the battery pack is placed on it, or a jacket through which coolant passes is placed in contact with the sides of the battery cells. A water pump, radiator, water piping, reserve tank, and other components are provided outside the battery pack and filled with coolant. As a result, the size and weight of the battery system are often larger than in the case of air cooling.

[0006] Similar to cooling a battery pack, methods for heating a battery pack often use air or water as a heat exchange medium. When heating air, warm air from an air conditioner is used as the air drawn into the battery pack, or an electric heater is installed inside the battery pack to heat the air inside the battery pack. However, because it takes a long time to heat a battery pack using air, time management is required to heat the battery pack during plug-in charging and ensure that the battery pack is sufficiently warm when the vehicle starts moving. On the other hand, when water is used, the water used for heat exchange is heated by a heater, and a mechanism to bypass the radiator is added to prevent the heated water from cooling. Because it also takes time to heat water, time management is required to start heating the battery pack before the vehicle starts moving, just as when air is used.

[0007] Here, lithium-ion batteries, which have excellent energy density and power density, have often been used to drive electric vehicles. However, because lithium-ion batteries only perform well within a narrow temperature range, a shift from lithium-ion batteries to all-solid-state batteries is predicted. Accordingly, battery packs made of stacked pouch-type battery cells, which enable thinner and lighter batteries and have excellent shape flexibility and heat dissipation properties, have been attracting attention.

[0008] However, when constructing a battery pack using pouch-type battery cells, it is difficult to use water as a heat exchange medium. Furthermore, although pouch-type battery cells are sealed with an exterior body such as a laminate film, it is necessary to prevent water from coming into contact with the solid electrolyte even if the seal of the exterior body is broken by some external force. On the other hand, when air is used as a heat exchange medium, the following points must be considered: (i) the intake air temperature during cooling must be kept sufficiently lower than the target temperature of the battery cells by coordinating with an air conditioner; (ii) the intake air temperature during heating must be kept sufficiently higher than the target temperature of the battery cells by coordinating with an air conditioner or plug-in charging; and (iii) because variations in battery cell temperature affect battery output limits and variations in battery degradation, it is necessary to design the air flow path and air volume so that the temperatures of all battery cells in the battery pack quickly converge to the target temperature.

[0009] One possible solution to these problems is to use a thermoelectric conversion element such as a Peltier element to manage the temperature of the battery pack. However, when a configuration in which a thermoelectric conversion element is placed between two batteries, as in Patent Document 1, is applied to a pouch-type battery cell, the battery cell expands and contracts during charging and discharging, causing fluctuations in the load on the thermoelectric conversion element. The thermoelectric conversion element does not have a high load capacity, which can lead to damage and abnormal operation, as well as the risk of short-circuiting the power supply. Furthermore, when a thermoelectric conversion element is directly attached to a portion of a pouch-type battery cell, load variations occur on the surface of the battery cell, which can lead to imbalances in the current density inside the battery cell. One possible solution is to make the contact surface of the thermoelectric conversion element as large as the surface of the battery cell, but this would result in over-specified temperature regulation performance and increase the size, weight, and cost of the battery pack.

[0010] Furthermore, when fins are used as heat exchangers as in Patent Document 1, the fins must be enlarged to increase the thermal capacity in order to improve the cooling capacity, making it difficult to configure a compact battery system. In particular, pouch-type battery cells are thinner than cylindrical or prismatic battery cells, and arranging a thermoelectric conversion element and fins between two pouch-type battery cells significantly increases the size of the battery cells in the stacking direction.

[0011] In view of the above circumstances, an object of the present disclosure is to provide a technology for improving the accuracy of temperature management in a compact battery system formed by stacking pouch-type battery cells.

[0012] A battery system according to one embodiment of the present disclosure includes: an assembled battery formed by stacking a plurality of pouch-shaped battery cells in which battery materials including electrodes and an electrolyte are sealed in a flat-shaped outer casing; a plurality of flat-shaped heat exchangers, each of which is disposed between corresponding ones of the plurality of battery cells and exchanges heat with the corresponding one of the plurality of battery cells; a plurality of thermoelectric conversion elements, each of which is connected to a corresponding one of the plurality of heat exchangers; and a control device that controls the amount of current flowing through each of the plurality of thermoelectric conversion elements based on the temperature of the plurality of battery cells.

[0013] According to one embodiment of the present disclosure, it is possible to improve the accuracy of temperature management in a compact battery system formed by stacking pouch-type battery cells.

[0014] FIG. 1 is a schematic diagram showing a configuration example of a vehicle including a control device according to an embodiment of the present disclosure. FIG. 2 is a diagram showing an assembled battery included in a battery system according to a first embodiment, as viewed from above the vehicle body. FIG. 3 is a diagram explaining the arrangement of a cooling heat exchanger and a cooling thermoelectric conversion element shown in FIG. 2. FIG. 4 is a diagram explaining the arrangement of a heating heat exchanger and a heating thermoelectric conversion element shown in FIG. 2. FIG. 5 is a circuit diagram of the battery system shown in FIG. 2. FIG. 6 is a diagram explaining cooling of battery cells by the battery system shown in FIG. 5. FIG. 7 is a diagram explaining temperature rise of battery cells by the battery system shown in FIG. 5. FIG. 8 is a diagram explaining temperature distribution of battery cells when no current is applied to thermoelectric conversion elements. FIG. 9 is a diagram explaining temperature distribution of battery cells when the amount of current applied to the thermoelectric conversion elements is constant. FIG. 10 is a diagram explaining an example of temperature equalization of battery cells by the battery system shown in FIG. 5. FIG. 11 is a diagram explaining an example of temperature equalization of battery cells by the battery system shown in FIG. 5. FIG. 12 is a diagram explaining an air-cooling system applicable to a battery system according to an embodiment of the present disclosure. FIG. 13 is a diagram explaining a setting range of a load on a spring member. FIG. 14 is a block diagram showing a configuration example of a control device included in a battery system according to a first embodiment. 1 is a flowchart illustrating an example of operation of a control device provided in a battery system according to a first embodiment. FIG. 2 is a diagram illustrating cooling of battery cells by a battery system according to a second embodiment. FIG. 3 is a diagram illustrating temperature rise of battery cells by a battery system according to a second embodiment. FIG. 4 is a diagram illustrating an example of temperature equalization of battery cells by a battery system according to a second embodiment. FIG. 5 is a diagram illustrating an example of temperature equalization of battery cells by a battery system according to a second embodiment. FIG. 6 is a diagram illustrating an example of temperature equalization of battery cells by a battery system according to a second embodiment.

[0015] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0016] 1. First Embodiment (1-1. Overall Configuration of Vehicle) With reference to FIG. 1, an example of the overall configuration of a vehicle 1 equipped with a battery system 100 according to an embodiment of the present disclosure will be described.

[0017] The vehicle 1 is a two-wheel-drive four-wheel vehicle in which a drive motor 2 serving as a drive power source for generating a drive torque to be transmitted to the front wheels outputs a drive torque that is transmitted to the front wheels.

[0018] The combination of drive wheels and the drive method are not limited. For example, the vehicle 1 may be a rear-wheel drive vehicle or a four-wheel drive vehicle. The vehicle 1 may also be an electric vehicle equipped with two drive motors, including a front-wheel drive motor and a rear-wheel drive motor. The vehicle 1 may also be an electric vehicle equipped with drive motors corresponding to each wheel.

[0019] The drive motor 2 provided in the vehicle 1 outputs drive torque that is transmitted to the front wheels via the differential mechanism 3 and the front drive shaft 4F. The drive motor 2 may be configured as a three-phase AC motor. In this case, a rotor (not shown) is rotated by a rotating magnetic field formed by supplying three-phase AC current to a stator (not shown), and drive torque is output. The drive motor 2 may also have a function of performing regenerative power generation by receiving rotational torque from the front wheels transmitted via the front drive shaft 4F and causing the rotor to rotate when three-phase AC current is not supplied to the stator.

[0020] The vehicle 1 is equipped with brake devices 5LF, 5RF, 5LR, and 5RR (hereinafter, collectively referred to as "brake devices 5" unless a distinction is required). The brake devices 5 apply braking force to the respective wheels. The brake devices 5 may be, for example, hydraulic brake devices. In this case, the hydraulic pressure supplied to each brake device 5 is adjusted by controlling the drive of a hydraulic unit (not shown) by a vehicle control device 7 described later. The brake devices 5 may be used in combination with regenerative braking using the drive motor 2.

[0021] The electric steering device 6 provided in the vehicle 1 is provided on the front wheel drive shaft 4F. The electric steering device 6 includes an electric motor (not shown) and a gear mechanism (not shown), and is controlled by a vehicle control device 7 to adjust the steering angle of the front wheels. The vehicle control device 7 controls the electric steering device 6 based on the steering angle of the steering wheel by the driver of the vehicle 1. Here, if the vehicle 1 is a vehicle capable of executing automatic driving control, the vehicle control device 7 controls the electric steering device 6 based on the steering angle of the steering wheel by the driver during manual driving. On the other hand, during automatic driving, the vehicle control device 7 controls the electric steering device 6 based on the steering angle or steering angular velocity set by a publicly known or arbitrary method.

[0022] The vehicle control device 7 includes one or more electronic control units (ECUs) that control the drive motor 2, the brake device 5, and the electric steering device 6. Note that some or all of the components of the vehicle control device 7 may be provided in a control device 40, which will be described later.

[0023] In addition, the vehicle 1 may be equipped with surrounding environment sensors (not shown) including a front imaging camera and a rear imaging camera. The vehicle 1 may also be equipped with a vehicle state sensor (not shown) that detects the operating state and behavior of the vehicle 1. The vehicle 1 may also be equipped with a GNSS (Global Navigation Satellite System) sensor (not shown) that receives satellite signals from positioning satellites such as GPS (Global Positioning System) satellites. The vehicle 1 may also be equipped with a notification device (not shown) that notifies the driver of the vehicle 1 of various information.

[0024] (1-2. Configuration of Battery System) The battery system 100 provided in the vehicle 1 includes at least a battery pack 10, a plurality of heat exchangers 20, a plurality of thermoelectric conversion elements 30, and a control device 40. The battery system 100 will be described in detail below with reference to Figures 2 to 5.

[0025] (Battery Assembly) FIG. 2 shows the interior of a battery pack including a battery assembly 10 formed by stacking pouch-shaped battery cells 11a to 11n. The battery assembly 10 is formed by stacking a plurality of pouch-shaped battery cells 11a to 11n (hereinafter, sometimes referred to as "battery cells 11"), each of which has a flat outer casing and battery materials, including electrodes and electrolytes, sealed therein. In this embodiment, the outer casing of each of the plurality of battery cells 11 is made of a film, such as a laminate film, and includes a first main surface S1 and a second main surface S2 facing the first main surface S1. The shorter sides of the first main surface S1 and the second main surface S2 preferably extend along the vehicle height direction Z, and the longer sides of the first main surface S1 and the second main surface S2 preferably extend along the vehicle length direction X or the vehicle width direction Y.

[0026] The electrode tabs 12a to 12m (positive and negative electrode tabs) of the pouch-type battery cells 11 are arranged in positions facing each other, and all of the battery cells 11 are electrically connected in series. Each battery cell 11 is provided with a temperature sensor Ta to Tn (not shown), and the detection results of the temperature sensors Ta to Tn are transmitted to the control device 40. However, from the perspective of making the battery system 100 more compact, one temperature sensor may be provided for a group of battery cells 11 that can be considered to have substantially the same cell temperature.

[0027] The battery pack 10 supplies power to the drive motor 2. The battery pack 10 is a rechargeable secondary battery, such as an all-solid-state battery with a rated voltage of approximately 200 V to 800 V. Here, the all-solid-state battery is primarily composed of pouch-shaped battery cells 11 manufactured by a lamination method, rather than cylindrical or prismatic battery cells manufactured by a winding method. This is because the solid electrolyte of an all-solid-state battery may undergo minute deformation or expansion during charge / discharge cycles. If cylindrical or prismatic battery cells with relatively rigid cases are used, stress due to deformation or expansion may concentrate internally, potentially affecting the performance and lifespan of the battery pack 10. Furthermore, since solid electrolytes have lower thermal conductivity than electrolyte solutions, thermal management is difficult in cylindrical or prismatic battery cells. Therefore, pouch-shaped battery cells 11 are suitable for all-solid-state batteries. However, while the battery pack 10 in the present disclosure is preferably an all-solid-state battery, it is not necessarily limited to an all-solid-state battery; lithium-ion batteries and the like may also be used. The rated voltage of the battery pack 10 is not particularly limited as long as it is capable of supplying power to the drive motor 2. Although the number of battery cells 11 shown in Fig. 2 is 14, the number of battery cells 11 in the present disclosure is not particularly limited and can be set arbitrarily.

[0028] (Heat Exchanger) Each of the multiple heat exchangers 20 has a flat shape. Each heat exchanger 20 is disposed between corresponding battery cells 11 and exchanges heat with the corresponding battery cell. Each heat exchanger 20 transfers heat from the lower side (floor side) to the upper side (roof side) in the vehicle height direction Z.

[0029] In this embodiment, the multiple heat exchangers 20 include multiple cooling heat exchangers 21a to 21h (hereinafter sometimes referred to as "cooling heat exchangers 21") and multiple heating heat exchangers 22a to 22g (hereinafter sometimes referred to as "heating heat exchangers 22"). Referring also to FIG. 6, the main surface of a corresponding cooling heat exchanger 21b among the multiple cooling heat exchangers 21 is in thermal contact with the first main surface S1 of the exterior body of the battery cell 11c. Hereinafter, "corresponding" means, for example, that the corresponding cooling heat exchanger 21b is disposed corresponding to the battery cell 11c that is to be cooled by the cooling heat exchanger 21b. Referring also to FIG. 7, the main surface of a corresponding heating heat exchanger 22b among the multiple heating heat exchangers 22 is in thermal contact with the second main surface S2 of the exterior body of the battery cell 11c. Hereinafter, "corresponding" means, for example, that the corresponding heating heat exchanger 22b is disposed corresponding to the battery cell 11c that is to be heated by the heating heat exchanger 22b. The first main surface S1 and the second main surface S2 are defined to face each other in the same battery cell 11c that is to be cooled or heated, and the order along the vehicle length direction X or vehicle width direction Y can be defined for each battery cell 11. The same applies to the cooling heat exchangers 21a, 21c to 21h and the heating heat exchangers 22a, 22c to 22g. That is, in this embodiment, when viewing the vehicle 1 from above, the main surfaces of the cooling heat exchanger 21 (preferably in the short-side direction of the main surface) and the main surfaces of the heating heat exchanger 22 (preferably in the short-side direction of the main surface) are alternately arranged along the vehicle height direction Z. Furthermore, one or more battery cells 11 are arranged between the cooling heat exchanger 21 and the heating heat exchanger 22 so that the first main surface S1 (preferably the short-side direction of the first main surface S1) and the second main surface S2 (preferably the short-side direction of the second main surface S2) of each battery cell 11 are aligned along the vehicle height direction Z. This allows the cooling heat exchanger 21 to cool the battery cells 11 arranged on both sides thereof. Meanwhile, the heating heat exchanger 22 can heat the battery cells 11 arranged on both sides thereof.

[0030] The cooling heat exchanger 21 can be, for example, a flat cooling heat pipe. The heating heat exchanger 22 can be, for example, a flat heating heat pipe. By disposing flat heat pipes between the battery cells 11, the battery system 100 can be configured with minimal increase in size (mainly in the stacking direction of the battery cells 11). Here, a heat pipe is a component that can transfer heat from one location to another by utilizing latent heat absorbed when a liquid changes to a gas or released when a gas changes to a liquid. Specifically, the heat pipe is a thermosiphon type heat pipe, for example, in which a working fluid is sealed inside a metal pipe. It can operate without power and can operate even in conditions with a relatively small temperature difference. In the case of a thermosiphon type, thermoelectric conversion elements 30 can be disposed above and below the battery cells 11. Therefore, although the length of the battery pack in the vehicle height direction Z increases, the length of the battery pack in the vehicle length direction X or the vehicle width direction Y can be reduced. This allows the battery pack to be disposed inside the center tunnel of the vehicle 1. The flat heat pipe has a flat shape, and is formed by arranging and fixing a plurality of the heat pipes in a direction perpendicular to the longitudinal direction of each heat pipe, with the evaporator at one end and the condenser at the other end. However, the heat exchanger 20 in the present disclosure is not limited to a heat pipe, and metal plates, graphite sheets, ceramic plates, vapor chambers, etc. can also be used.

[0031] (Thermoelectric Conversion Element) Each of the plurality of thermoelectric conversion elements 30 is connected to a corresponding one of the plurality of heat exchangers 20. Note that, although a Peltier element can be adopted as the thermoelectric conversion element 30 shown in Fig. 2, the present disclosure is not limited thereto, and a thermoelectric conversion element using a carbon nanotube may also be adopted.

[0032] 3 and 6, the heat absorption surface 33 of a corresponding cooling thermoelectric conversion element 31b among the plurality of cooling thermoelectric conversion elements 31 is in thermal contact with the corresponding cooling heat exchanger 21b among the plurality of cooling heat exchangers 21. More specifically, the heat absorption surface 33 of a corresponding cooling thermoelectric conversion element 31b among the plurality of cooling thermoelectric conversion elements 31 is in thermal contact with the condenser section 24 of the corresponding cooling heat exchanger 21b among the plurality of cooling heat exchangers 21. Here, the evaporator section 23 of the cooling heat exchanger 21b is in thermal contact with the second main surface S2 of the exterior body of the battery cell 11b and the first main surface S1 of the exterior body of the battery cell 11c. Referring also to FIG. 2, from the viewpoint of reducing contact resistance, the heat absorption surface 33 of the cooling thermoelectric conversion element 31b and the condenser section 24 of the cooling heat exchanger 21b may be in close contact with each other via a heat conductive member 75 such as a silicone sheet. Furthermore, from the viewpoint of further reducing the temperature of the heat absorption surface 33 of the cooling thermoelectric conversion element 31b, the heat sink 71b may be attached so that the heating surface 34 of the cooling thermoelectric conversion element 31b is in contact with the heat sink 71b. In this case, too, from the viewpoint of reducing contact resistance, the heating surface of the cooling thermoelectric conversion element 31b and the heat sink 71b may be brought into close contact with each other via a heat conductive member 75 such as a silicone sheet. Note that the same can be applied to the cooling thermoelectric conversion elements 31a, 31c to 31h and the heat sinks 71a, 71c to 71h other than the cooling thermoelectric conversion element 31, and therefore a description thereof will be omitted.

[0033] 4 and 7 , the heating surface 36 of a corresponding heating thermoelectric conversion element 32b among the plurality of heating thermoelectric conversion elements 32 is in thermal contact with a corresponding heating heat exchanger 22b among the plurality of heating heat exchangers 22. More specifically, the heating surface 36 of a corresponding heating thermoelectric conversion element 32b among the plurality of heating thermoelectric conversion elements 32 is in thermal contact with the evaporator section 25 of the corresponding heating heat exchanger 22b among the plurality of heating heat exchangers 22. Here, the condenser section 26 of the heating heat exchanger 22b is in thermal contact with the second main surface S2 of the exterior body of the battery cell 11c and the first main surface S1 of the battery cell 11d. Referring also to FIG. 2 , from the viewpoint of reducing contact resistance, the heating surface 36 of the heating thermoelectric conversion element 32b and the evaporator section 25 of the heating heat exchanger 22b may be in close contact with each other via a heat conductive member 75 such as a silicone sheet. Furthermore, from the viewpoint of further reducing the temperature of the heating surface 36 of the heating thermoelectric conversion element 32b, the heat sink 72b may be attached so that the heat absorption surface 35 of the heating thermoelectric conversion element 32b is in contact with the heat sink 72b. In this case, from the viewpoint of reducing contact resistance, the heat absorption surface 35 of the heating thermoelectric conversion element 32b and the heat sink 72b may be brought into close contact with each other via a heat conductive member 75 such as a silicone sheet. Note that the same can be applied to the heating thermoelectric conversion elements 32a, 32c to 32g and the heat sinks 72a, 72b to 72g, and therefore a description thereof will be omitted.

[0034] The thermoelectric conversion element 30 may be switched on and off by an electronic switch such as a semiconductor switch, or by a mechanical switch such as a relay, but is not limited to these. As will be described in detail later, the amount of current flowing through the thermoelectric conversion element 30 is controlled by the control device 40, for example, by PWM drive. While one thermoelectric conversion element 30 is used for two battery cells 11 in FIGS. 5 to 7 , the present disclosure is not limited to this. For example, if there are battery cell groups in which three or more battery cells 11 are arranged in succession and the temperature of the battery cells 11 can be considered to be substantially the same even if the current of the battery cells 11 or the ambient temperature changes, one thermoelectric conversion element 30 may be assigned to each battery cell group.

[0035] (Control Device) The control device 40 controls the amount of current flowing through each of the thermoelectric conversion elements 30 based on the temperatures of the battery cells 11. Here, an example of temperature management by the control device 40 will be described with reference to Figs. 6 to 12 .

[0036] In order to maximize the input / output performance of the battery pack 10 and suppress the progression of deterioration of each battery cell 11, it is important to properly manage the temperature of each battery cell 11. The temperature management is classified into three categories: cooling the battery cells 11, heating the battery cells 11, and equalizing the temperature of the battery cells 11. Below, the temperature management by the control device 40 in each case will be described.

[0037] First, the cooling of the battery cells 11 will be described. The amount of heat generated by the battery cells 11 varies depending on the current value and internal resistance of the battery cells 11, and the larger the current value, the greater the amount of heat generated. If the amount of heat generated by the battery cells 11 exceeds the amount of heat dissipated, the temperature of the battery cells 11 will rise over time. To prevent this, it is possible to reduce the current value of the battery cells 11, but this may result in a decrease in the driving performance of the vehicle 1 or an extension of the charging time of the battery pack, which may not meet user expectations. Therefore, by forcibly cooling the battery cells 11, a predetermined performance can be maintained.

[0038] In this embodiment, two battery cells 11 are cooled using one set of a cooling heat exchanger 21 such as a flat cooling heat pipe and a cooling thermoelectric conversion element 31 such as a Peltier element. As described above with reference to Figure 3, the first main surface S1 of the exterior body of the battery cell 11 comes into thermal contact with the evaporator section 23 of the cooling heat exchanger 21, so that heat from the battery cell 11 is transferred to the condenser section 24 of the cooling heat exchanger 21.

[0039] 6, when the switch SW1b of the cooling thermoelectric conversion element 31b is switched from the OFF state (broken line) to the ON state (solid line) by the control device 40, a temperature difference occurs between the heat absorption surface 33 and the heating surface 34 of the cooling thermoelectric conversion element 31b. Because the heat from the cooling heat exchanger 21b is absorbed by the heat absorption surface 33 of the cooling thermoelectric conversion element 31b, the temperatures of the cooling heat exchanger 21b and the battery cells 11b, 11c arranged on both sides of it decrease.

[0040] When a heat sink 71b is attached to the cooling thermoelectric conversion element 31b, the ambient temperature rises due to heat dissipation from the heat sink 71b. Because the temperature difference that the cooling thermoelectric conversion element 31b can generate is limited, an increase in the temperature of the heat sink 71b also increases the temperature of the heat absorption surface 33 of the cooling thermoelectric conversion element 31b. Therefore, the control device 40 may lower the temperature of the heat sink 71b by operating an air-cooling system 90 provided in the case 14 of the battery pack, as shown in FIG. 13 . The air-cooling system 90 includes an intake filter 91 provided at one end of the exterior of the case 14 and drawing air into the case 14, and a ventilation fan 93 provided at the other end opposite the one end of the exterior of the case 14 and discharging air to the outside of the case 14 through a duct 92. The intake filter 91, duct 92, and ventilation fan 93 may be of any known or arbitrary structure. This reduces the temperature of the heat absorption surface 33 of the cooling thermoelectric conversion element 31b, further improving the cooling performance of the battery cells 11b and 11c. Note that the control device 40 can also cool the battery cells 11a, 11d to 11n in addition to the battery cells 11b and 11c by controlling switches other than the switch SW1b in the same manner.

[0041] Next, the temperature rise of the battery cell 11 will be described. Although the operating temperature range of an all-solid-state battery is wider than that of a lithium-ion battery even at low temperatures, the input and output power available for starting (output, charging) in an extremely low-temperature environment is limited compared to that at room temperature. In electric vehicles, there are systems that use plug-in power to keep the battery cell 11 warm in preparation for driving in an extremely low-temperature environment. However, if water or air is used as the heat exchange medium, it takes a relatively long time for the battery cell 11 to reach the appropriate temperature after the start of temperature rise.

[0042] In contrast, in this embodiment, the temperatures of the two battery cells 11 are raised by a set of a heating heat exchanger 22 such as a flat heating heat pipe and a heating thermoelectric conversion element 32 such as a Peltier element. Specifically, referring to Fig. 7, when the switch SW2b of the heating thermoelectric conversion element 32b is turned on by the control device 40, a temperature difference is generated between the heat absorption surface 35 and the heating surface 36 of the heating thermoelectric conversion element 32b. The heat generated by the heating thermoelectric conversion element 32b heats the battery cells 11c and 11d through the heating heat exchanger 22b.

[0043] When a heat sink 72b is attached to the heating thermoelectric conversion element 32b, the temperature of the heat absorption surface 35 of the heating thermoelectric conversion element 32b gradually decreases due to the heat capacity of the heat sink 72b, and during this time, the temperature of the heating surface 36 also gradually decreases. While the temperature of the heat absorption surface 35 has not yet completely decreased, the temperature of the heating surface 36 also increases relatively, increasing the rate of temperature rise. When the heat exchange between the heat sink 72b and the surrounding air reaches equilibrium, the decrease in the heating surface 36 stops and heating is carried out stably. Note that the control device 40 can heat battery cells 11a, 11b, 11e to 11n in addition to battery cells 11c and 11d by similarly controlling switches other than switch SW2b.

[0044] When charging or discharging of the battery cell 11 begins, heat is generated inside the battery cell 11 due to the current and internal resistance of the battery cell 11, so the switches SW2a to SW2g of the heating thermoelectric conversion element 32b are switched to the off state by the control device 40.

[0045] Finally, we will explain temperature equalization of the battery cells 11. The temperature of the battery cells 11 affects the progression of deterioration. The higher the temperature of the battery cells 11, the faster the deterioration progresses. As the battery cells 11 deteriorate, differences occur in the rate of decrease in discharge capacity or the rate of increase in internal resistance. The temperature distribution is largely determined by the shape of the battery pack 10 and the arrangement of the battery cells 11, etc. In areas where the battery cells 11 are densely packed, such as the center of the battery pack 10, the temperature tends to rise easily during normal current flow and does not decrease easily even when current flow to each thermoelectric conversion element 30 is stopped. On the other hand, the battery cells 11 near the edge of the case 14 tend to dissipate heat more easily, so the temperature does not increase as easily as in the center of the battery pack 10 and the temperature tends to decrease easily when current flow to each thermoelectric conversion element 30 is stopped.

[0046] FIG. 8 shows an example of the temperature distribution of the battery cells 11 when the battery cells 11 are discharged without cooling. All battery cells 11 exceed the target temperature range. The temperatures of battery cells 11d to 11k near the center of the battery pack 10 are relatively high, while the temperatures of battery cells 11a and 11n near both ends of the battery pack 10 are lowest. FIG. 9 shows an example of the temperature distribution of the battery cells 11 when, in contrast to the state shown in FIG. 8, the cooling thermoelectric conversion elements 31 are driven by the control device 40 with the same amount of current. The black dots in FIG. 9 indicate the amount of current flowing through the cooling thermoelectric conversion elements 31 corresponding to each battery cell 11 (the same applies below). Although the temperature of the battery cells 11 has generally decreased compared to FIG. 8 , there is still variation in the temperature of the battery cells 11. That is, the temperatures of battery cells 11a and 11n among battery cells 11a to 11n are not within the target temperature range.

[0047] Therefore, as shown in FIG. 10 , the control device 40 individually controls the amount of current flowing through each cooling thermoelectric conversion element 31 so that the temperature of each battery cell 11 falls within the target temperature range. The closer the battery cell 11 is to the end of the battery pack (the inner wall of the case 14), the easier it is for the battery cell 11 to dissipate heat. Therefore, the control device 40 may control the amount of current flowing through the cooling thermoelectric conversion element 31 for the battery cell 11 that is in thermal contact with the cooling thermoelectric conversion element 31 based on the distance between the battery pack case 14 and the battery cell 11. For example, the control device 40 may control the amount of current flowing through the cooling thermoelectric conversion element 31 that is in thermal contact with the battery cell 11 so that the closer the distance between the battery pack case 14 and the battery cell 11 becomes, the smaller the amount of current flowing through the cooling thermoelectric conversion element 31 that is in thermal contact with the battery cell 11 becomes. Similarly, as shown in FIG. 11 , during temperature rise, the control device 40 individually controls the amount of current flowing through each heating thermoelectric conversion element 32 so that the temperatures of all battery cells 11 fall within the target temperature range. 11 indicate the amount of current flowing through the heating thermoelectric conversion elements 32 arranged corresponding to each battery cell 11 (the same applies below). The closer the battery cell 11 is to the end of the battery pack (such as the inner wall of the case 14), the easier it is for the battery cell 11 to cool. Therefore, the control device 40 may control the amount of current flowing through the heating thermoelectric conversion elements 32 for the battery cells 11 that are in thermal contact with the heating thermoelectric conversion elements 32 based on the distance between the battery pack case 14 and the battery cells 11. For example, the control device 40 may control the amount of current flowing through the heating thermoelectric conversion elements 32 that are in thermal contact with the battery cells 11 so that the closer the distance between the battery pack case 14 and the battery cells 11 is, the greater the amount of current flowing through the heating thermoelectric conversion elements 32 that are in thermal contact with the battery cells 11. Furthermore, when there is a mixture of battery cells 11d to 11k that exceed the target temperature range and battery cells 11a, b, m, and n that are below the target temperature range, as shown in Figure 12, the control device 40 combines a cooling thermoelectric conversion element 31 and a heating thermoelectric conversion element 32 and controls the amount of current flowing to each, thereby converging the temperatures of all battery cells 11 within the target temperature range.

[0048] (Pressure Plate) Referring to FIG. 2 , the battery system 100 preferably further includes pressure plates 15 that apply a load to both ends of the battery pack 10 along the stacking direction of the multiple battery cells 11. Specifically, two pressure plates 15 are disposed on each end of the battery pack 10, which has a structure in which a heat exchanger 20 is sandwiched between the battery cells 11. One of the two pressure plates 15 is connected to a spring member 16 fixed to the case 14, for example. As a result, even if the thickness of the battery cells 11 fluctuates due to charging and discharging, or the battery cells 11 expand or compress due to temperature changes, the spring force of the spring member 16 keeps the entire battery pack 10 within a predetermined load range. The predetermined range can be adjusted as needed to avoid excessive loads that could damage the battery pack 10 due to dimensional changes in the stacking direction, or excessive load loss on the battery pack 10 that could reduce the heat transfer efficiency between the battery cells 11 and the heat exchanger 20. 14 , the length of the spring member 16 when the battery cell 11 is at its most contracted state is defined as L1, and the length of the spring member 16 when the battery cell 11 is at its most expanded state is defined as L2. The appropriate load range that ensures sufficient heat conduction without damaging either the battery cell 11 or the heat exchanger 20 is defined as Pa or more and Pb or less. The maximum allowable load of the spring member 16 is defined as Pmax, and the natural length of the spring member 16 is defined as L0. The predetermined ranges are adjusted so that both P1 and P2 fall within the range of Pa or more and Pb or less.

[0049] The battery pack 10 can be positioned within the case 14 by a pressure plate 15 and guide rods 17 fixed to the case 14. To prevent the stacked state of the battery pack 10 from being unable to be maintained when an impact is applied to the vehicle 1, it is preferable to attach a bracket having a known structure to one or more of the heat exchangers 20 and pass the guide rods 17 through it. It is preferable to arrange a thermally conductive member such as a silicone sheet between the battery cells 11 and the heat exchanger 20 (heat pipes) to absorb thickness variations in the battery cells 11, so that friction does not occur between the exterior body (e.g., laminate film) of the battery cells 11 and the heat exchanger 20 (heat pipe), which could damage the exterior body and cause a short circuit or poor insulation of the battery cells 11.

[0050] In addition to these, the battery system 100 includes an inverter 50 and a converter 60 as shown in FIG.

[0051] (Inverter) The inverter 50 converts DC power supplied from the battery pack 10 into, for example, three-phase AC power and supplies it to the traction motor 2. The inverter 50 also converts, for example, three-phase AC power generated by regeneration of the traction motor 2 into DC power and supplies it to the converter 60. The driving of the inverter 50 is controlled by the vehicle control device 7.

[0052] (Converter) The converter 60 boosts the voltage of the power regenerated by the drive motor 2 to at least the required charging voltage of the battery pack 10 and supplies it to the battery pack 10. The boost circuit may also have the function of at least boosting or lowering the output voltage of the battery pack 10 and supplying it to the inverter 50. The driving of the converter 60 is controlled by the vehicle control device 7.

[0053] (1-3. Details of the Control Device) The control device 40 according to this embodiment will be described in detail with reference to Fig. 15. Note that a part or all of the configuration of the control device 40 may be incorporated into a publicly known or arbitrary battery management system (BMS).

[0054] (1-3-1. Configuration Example) The control device 40 functions as a device that controls the battery system 100 by having one or more processors, such as CPUs (Central Processing Units), execute a computer program. The computer program is a computer program that causes the processor to execute the operations, described below, that should be performed by the control device 40. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) 46, described below, or may be recorded on a recording medium built into the control device 40 or any recording medium that can be externally attached to the control device 40.

[0055] The recording medium for recording a computer program may be a magnetic medium such as a hard disk, a floppy disk, or a magnetic tape; an optical recording medium such as a CD-ROM, a DVD, or a Blu-ray (registered trademark); a magneto-optical medium such as a floptical disk; a memory element such as a RAM or a ROM; a flash memory such as a USB memory or an SSD; or any other medium capable of storing a program.

[0056] Cooling thermoelectric conversion elements 31a to 31h, such as Peltier elements, are connected to the control device 40 via a known current adjustment circuit and switches SW1a to SW1h. Heating thermoelectric conversion elements 32a to 32g, such as Peltier elements, are also connected to the control device 40 via a known current adjustment circuit and switches SW2a to SW2g. Temperature sensors Ta to Tn are also connected to the control device 40 via a known analog input circuit. The control device 40 may be connected to the vehicle control device 7 via a dedicated line, a controller area network (CAN), a local internet (LIN), or other communication means, and some or all of the components of the control device 40 may be provided in the vehicle control device 7.

[0057] The control device 40 includes a processing unit 41 and a storage unit 46 .

[0058] (Processing Unit) The processing unit 41 includes one or more processors such as a CPU and various peripheral components. Part or all of the processing unit 41 may be configured with updatable components such as firmware, or may be a program module or the like that is executed by instructions from the CPU or the like.

[0059] (Storage Unit) The storage unit 46 is configured with one or more storage elements such as RAM or ROM connected to the processing unit 41 so as to be able to communicate with the processing unit 41. However, there are no particular limitations on the type and number of storage units 46. The storage unit 46 stores information such as computer programs executed by the processing unit 41, various parameters used in arithmetic processing, detection data, and arithmetic results.

[0060] (1-3-2. Functional Configuration of Processing Unit) The functional configuration of the processing unit 41 of the control device 40 will be described. The processing unit 41 includes an acquisition unit 42, a determination unit 43, a calculation unit 44, and a control unit 45. Each of these units is a function realized by execution of a computer program by one or more processors such as a CPU. However, some or all of the acquisition unit 42, determination unit 43, calculation unit 44, and control unit 45 may be configured using analog circuits.

[0061] (Acquisition Unit) The acquisition unit 42 acquires the target temperature range of the battery cell 11. Note that the target temperature range of the battery cell 11 is determined in advance according to the characteristics of the battery cell 11, and may be stored in the storage unit 46 in advance.

[0062] The acquisition unit 42 acquires the temperature of the battery cells 11. The temperature of the battery cells 11 can be acquired from a temperature sensor T provided in each of the battery cells 11.

[0063] (Determination unit) The determination unit 43 determines whether the temperature of the battery cell 11 acquired by the acquisition unit 42 is above the target temperature range. The determination unit 43 also determines whether the temperature of the battery cell 11 acquired by the acquisition unit 42 is below the target temperature range.

[0064] (Calculation Unit) The calculation unit 44 calculates the amount of deviation of the temperature of the battery cell 11 acquired by the acquisition unit 42 from the target temperature range.

[0065] (Controller) The controller 45 controls the amount of current flowing through each of the thermoelectric conversion elements 30 based on the determination result by the determiner 43. At this time, the controller 45 may also control the amount of current flowing through each of the thermoelectric conversion elements 30 based on the deviation amount calculated by the calculator 44.

[0066] (1-3-3. Example of Operation of Control Device) With reference to FIG. 16, an example of operation of the control device 40 according to this embodiment will be briefly described along a flowchart.

[0067] In step S10, the acquisition unit 42 acquires the target temperature range of each battery cell 11 by referring to the storage unit 46. After that, the process proceeds to step S11.

[0068] In step S11, the acquisition unit 42 acquires the temperature of each battery cell 11 from the temperature sensor T provided in each battery cell 11. After that, the process proceeds to step S12.

[0069] In step S12, the determination unit 43 determines whether the temperature of each battery cell 11 acquired in step S11 exceeds the target temperature range acquired in step S10. If it is determined that the temperature of each battery cell 11 exceeds the target temperature range (step S12: YES), the process proceeds to step S13. On the other hand, if it is determined that the temperature of each battery cell 11 does not exceed the target temperature range (step S12: NO), the process proceeds to step S14. In the following description of step S13, the temperatures of battery cells 11b and 11c exceed the target temperature range, but the present disclosure is not limited to this.

[0070] In step S13, the control unit 45 switches the switch SW1b of the cooling thermoelectric conversion element 31b from the OFF state to the ON state so that the temperatures of the battery cells 11b and 11c fall within the target temperature range. At this time, the control unit 45 controls the amount of current supplied to the cooling thermoelectric conversion element 31b based on the deviation of the temperatures of the battery cells 11b and 11c from the target temperature range calculated by the calculation unit 44. Then, the process ends.

[0071] In step S14, the determination unit 43 determines whether the temperature of the battery cell 11 acquired in step S11 is below the target temperature range acquired in step S10. If it is determined that the temperature of each battery cell 11 is below the target temperature range (step S14: YES), the process proceeds to step S15. On the other hand, if it is determined that the temperature of each battery cell 11 is not below the target temperature range (step S14: NO), the process ends. In the following step S15, the temperatures of the battery cells 11c and 11d are described as being below the target temperature range, but the present disclosure is not limited to this.

[0072] In step S15, the control unit 45 switches the switch SW2b of the heating thermoelectric conversion element 32b to the ON state so that the temperature of the battery cell 11 falls within the target temperature range. At this time, the control unit 45 controls the amount of current supplied to the heating thermoelectric conversion element 32b based on the deviation of the temperatures of the battery cells 11c and 11d from the target temperature range calculated by the calculation unit 44. Then, the process ends.

[0073] (Effects) As described above, the battery system 100 according to this embodiment includes a battery pack 10 formed by stacking a plurality of pouch-shaped battery cells 11, each of which has a flat exterior body and in which battery materials including electrodes and an electrolyte are sealed. The battery system 100 also includes a plurality of flat heat exchangers 20. Each heat exchanger 20 is disposed between a corresponding one of the plurality of battery cells 11 and exchanges heat with the corresponding battery cell. The battery system 100 also includes a plurality of thermoelectric conversion elements 30. Each thermoelectric conversion element 30 is connected to a corresponding one of the plurality of heat exchangers 20. The battery system 100 also includes a control device 40 that controls the amount of current flowing through each of the plurality of thermoelectric conversion elements 30 based on the temperature of the plurality of battery cells 11.

[0074] With this configuration, the heat exchanger 20 equipped with the thermoelectric conversion element 30 can be disposed between the battery cells 11. Therefore, by utilizing the excellent thermal conductivity of the heat exchanger 20 and controlling the amount of current flowing through the thermoelectric conversion element 30, the temperature of the battery cells 11 can be appropriately managed. Specifically, when cooling the battery cells 11, the heat of the battery cells 11 conducted to the condenser section 24 of the cooling heat exchanger 21 is cooled by the cooling thermoelectric conversion element 31. On the other hand, when heating the battery cells 11, the heat generated by the heating thermoelectric conversion element 32 is conducted from the evaporator section 25 to the condenser section 26 of the heating heat exchanger 22, thereby heating the battery cells 11. Furthermore, by combining these cooling and heating functions, the temperatures of all the battery cells 11 can be converged within a target temperature range. Therefore, the accuracy of temperature management can be improved in a compact battery system 100 in which pouch-type battery cells 11 are stacked.

[0075] In particular, the exterior housing of each battery cell 11 according to this embodiment includes a first main surface S1 and a second main surface S2 opposite the first main surface S1. The multiple heat exchangers 20 include multiple cooling heat exchangers 21 and multiple heating heat exchangers 22. The main surface of a corresponding one of the multiple cooling heat exchangers 21 is in thermal contact with the first main surface S1 of the exterior housing of the battery cell 11. The heat absorption surface 33 of the cooling thermoelectric conversion element 31 is in thermal contact with the corresponding cooling heat exchanger. Meanwhile, the main surface of a corresponding one of the multiple heating heat exchangers 22 is in thermal contact with the second main surface S2 of the exterior housing of the battery cell 11. The heating surface 36 of the heating thermoelectric conversion element 32 is in thermal contact with the corresponding heating heat exchanger. Heat from or to the battery cell 11 moves from the lower side to the upper side in the vehicle height direction Z. According to this configuration, a cooling heat exchanger 21 and a cooling thermoelectric conversion element 31, as well as a heating heat exchanger 22 and a heating thermoelectric conversion element 32, are provided for each battery cell 11, so that the temperature of the battery cells 11 can be equalized quickly and accurately.

[0076] 2. Second Embodiment Next, a battery system according to a second embodiment of the present disclosure will be described, focusing on differences from the first embodiment.

[0077] (2-1. Configuration of Battery System) Referring also to FIG. 17, the battery system 100 provided in the vehicle 1 includes at least a battery pack 10, a plurality of heat exchangers 20, a plurality of thermoelectric conversion elements 30, and a control device 40.

[0078] (Battery Assembly) The battery assembly 10 is formed by stacking multiple pouch-shaped battery cells 11, each of which has a flat exterior housing and battery materials, including electrodes and an electrolyte, sealed therein. In this embodiment shown in FIGS. 17 and 18 , the exterior housing of each of the multiple battery cells 11a to 11p includes a first main surface S1 and a second main surface S2 facing the first main surface S1. The shorter sides of the first main surface S1 and the second main surface S2 preferably extend along the vehicle height direction Z, and the longer sides of the first main surface S1 and the second main surface S2 preferably extend along the vehicle length direction X or the vehicle width direction Y. The electrode tabs 12 of each battery cell 11 are preferably of a type in which the positive and negative terminals protrude from the same side. The number of battery cells 11 can be set arbitrarily.

[0079] (Heat Exchanger) Each of the heat exchangers 20 has a flat shape. Each heat exchanger 20 is disposed between corresponding battery cells 11 among the plurality of battery cells 11 and exchanges heat with the corresponding battery cell 11. In this embodiment, each of the heat exchangers 20 is in thermal contact with a first main surface S1 of a battery cell 11a corresponding to a first battery cell among the plurality of battery cells 11 and a second main surface S2 of a battery cell 11b corresponding to a second battery cell among the plurality of battery cells 11. Here, the corresponding heat exchanger 20a is disposed between the battery cell 11a corresponding to the first battery cell and the battery cell 11b corresponding to the second battery cell. In this embodiment shown in FIGS. 17 and 18 , it is preferable to position the heat exchangers 20a to 20h horizontally to reduce the height of the battery pack. Therefore, a wick-type flat heat pipe is preferably used as the heat exchanger 20, rather than a thermosiphon-type heat pipe. In the case of the wick type, the thermoelectric conversion elements 30 can be arranged on the side surfaces (surfaces perpendicular to the first main surface S1 and the second main surface S2) of the battery cells 11, thereby reducing the height of the battery pack. This allows the battery pack to be arranged in the floor portion of the vehicle 1. The number of heat exchangers 20 can be set arbitrarily.

[0080] (Thermoelectric Conversion Element) Each of the plurality of thermoelectric conversion elements 30 is connected to a corresponding one of the plurality of heat exchangers 20. In the present embodiment shown in Figures 17 and 18, Peltier elements are used as the plurality of thermoelectric conversion elements 30a to 30h, but the present disclosure is not limited thereto. The number of thermoelectric conversion elements 30 can be set arbitrarily.

[0081] (Heat Absorber) The heat absorber 70 is connected to the plurality of thermoelectric conversion elements 30. In the present embodiment shown in Figures 17 and 18, the heat absorber 70 may include a heat sink 73 connected to the plurality of thermoelectric conversion elements 30a to 30h, and a heat sink 74 connected to the plurality of thermoelectric elements 81, which will be described later.

[0082] (Recovery Device) The recovery device 80 recovers the heat absorbed by the heat absorber 70 as electric power. In the present embodiment shown in FIGS. 17 and 18 , the recovery device 80 may include a plurality of thermoelectric elements 81 connected in series, a DC-DC converter 82 connected to the plurality of thermoelectric elements 81, and an auxiliary battery 83 connected to the DC-DC converter 82. The recovery of electric power is performed, for example, when the ignition is ON, Ready-ON, plug-in charging, or quick charging is performed. The auxiliary battery 83 is, for example, a lead-acid battery or the like with a rated voltage of 12 V to 24 V that supplies electric power to auxiliary devices mounted on the vehicle 1, but is not limited thereto.

[0083] (Control Device) The control device 40 controls the amount of current flowing through each of the plurality of thermoelectric conversion elements 30 based on the temperatures of the plurality of battery cells 11. Unlike the first embodiment, the control device 40 further controls the direction of current flowing through the plurality of thermoelectric conversion elements 30 based on the temperatures of the plurality of battery cells 11. As will be described in detail below, the plurality of heat exchangers 20 transfer heat along a direction (X direction or Y direction) perpendicular to the vehicle height direction Z and in a direction corresponding to the current flow direction.

[0084] First, the cooling of the battery cells 11 will be described. Referring to FIG. 17 , when the control device 40 switches SW1a and SW4a of the H-bridge circuit to the ON state and the control device 40 switches SW2a and SW3a to the OFF state, positive power is supplied to the power line (solid line) of the thermoelectric conversion element 30a corresponding to the H-bridge circuit, and negative power is supplied to the power line (dashed line). At this time, the heat exchanger 20a side of the thermoelectric conversion element 30a becomes the heat absorption surface, and the heat sink 73 side becomes the heating surface. Then, as indicated by the arrows in FIG. 17 , heat from the battery cells 11a and 11b is conducted to the heat sink 73 via the thermoelectric conversion element 30a. The heat conducted to the heat sink 73 is then released into the surrounding air. Note that this embodiment is not limited to an H-bridge circuit, as long as the direction of current can be changed. The same applies below.

[0085] Here, a plurality of thermoelectric elements 81 connected in series are attached to the heat sink 73. The contact surface of each thermoelectric element 81 on the heat sink 73 side receives heat from the heat sink 73 and increases in temperature. Meanwhile, the surface of each thermoelectric element 81 opposite the heat sink 73 is cooled by the heat sink 74 and decreases in temperature. As a result, a temperature difference occurs between the two surfaces of each thermoelectric element 81. This temperature difference generates an electromotive voltage in the output wire of each thermoelectric element 81. The output voltage of the plurality of thermoelectric elements 81 connected in series is input to an insulated DC-DC converter 82. The output power of the DC-DC converter 82 charges an auxiliary battery 83. This reduces the power down-converted from high voltage to auxiliary voltage, leading to improved power efficiency.

[0086] Next, the temperature rise of the battery cell 11 will be described. Referring to FIG. 18 , when the control device 40 switches the switches SW2a and SW3a of the H-bridge circuit to the ON state and the control device 40 switches the switches SW1a and SW4a to the OFF state, positive power is supplied to the power line (solid line) of the thermoelectric conversion element 30a corresponding to the H-bridge circuit, and negative power is supplied to the power line (dashed line). In other words, the direction of power during heating and the direction of power during cooling are opposite to each other. At this time, the side of the thermoelectric conversion element 30a facing the heat exchanger 20a becomes the heating surface, and the side of the heat sink 73 becomes the heat absorption surface. Then, as indicated by the arrows in FIG. 18 , heat from the heat sink 73 is conducted to the heat exchanger 20a via the thermoelectric conversion element 30a. The heat conducted to the heat exchanger 20a heats the battery cell 11a, raising the temperature of the battery cell 11a.

[0087] Here, the contact surfaces of the thermoelectric elements 81 attached to the heat sink 73 that are closest to the heat sink 73 are cooled by the heat sink 73 and their temperature drops. Meanwhile, the surfaces of each thermoelectric element 81 opposite the heat sink 73 are heated by the heat sink 74 absorbing heat from the surrounding air, causing the temperature to rise. This creates a temperature difference between the two surfaces of each thermoelectric element 81. This temperature difference generates an electromotive voltage in the output wire of each thermoelectric element 81. However, the polarity of the electromotive voltage is usually opposite to that when the battery cell 11 is cooling. As with cooling the battery cell 11, the output voltage of the multiple thermoelectric elements 81 connected in series is input to an isolated DC-DC converter 82. The subsequent process is similar to that during cooling. However, the polarity of the output voltage of the thermoelectric elements 81 is opposite when the battery cell 11 is cooling and when it is heating up. However, by providing a diode bridge circuit 84 before the DC-DC converter 82 as shown in FIG. 18 , the polarity of both voltages can be made the same.

[0088] The cooling and heating of the battery cells 11 have been described above using the example in which the control device 40 controls the thermoelectric conversion element 30a, but the present disclosure is not limited to this. When the control device 40 controls the thermoelectric conversion elements 30b to 30h other than the thermoelectric conversion element 30a, the control device 40 controls the switches SW1b to SW1h, SW2b to SW2h, SW3b to SW3h, and SW4b to SW4h in the corresponding H-bridge circuits in the same manner as described above. This causes the cooling or heating of the battery cells 11c to 11p corresponding to the thermoelectric conversion elements 30b to 30h, respectively.

[0089] Finally, temperature equalization of the battery cells 11 will be described. The control device 40 controls the amount and direction (positive or negative) of current flow through the thermoelectric conversion elements 30 so that the temperature of each battery cell 11 falls within the target temperature range. The control device 40 turns on switches SW1 and SW4 in the H-bridge circuit for battery cells 11 that are above the target temperature range. As a result, the drive current of the thermoelectric conversion elements 30 becomes positive, as shown in FIG. 19 , so that the heat exchanger 20 side of the thermoelectric conversion elements 30 becomes the heat absorption surface and the heat sink 73 side becomes the heating surface, thereby cooling the battery cells 11 that are above the target temperature range. Meanwhile, the control device 40 turns on switches SW2 and SW3 in the H-bridge circuit for battery cells 11 that are below the target temperature range. 20, the drive current of the thermoelectric conversion element 30 becomes negative, so that the side of the thermoelectric conversion element 30 facing the heat exchanger 20 becomes the heating surface and the side facing the heat sink 73 becomes the heat absorption surface, thereby heating the battery cells 11 whose temperatures are below the target temperature range. The drive current of the thermoelectric conversion element 30 is controlled by PWM drive.

[0090] When some battery cells 11 are above the target temperature range and others are below the target temperature range, the control device 40 individually controls the amount and direction (positive / negative) of current flow through the thermoelectric conversion elements 30, as shown in FIG. 21 . Also referring to FIG. 22 , consider a case where the temperature of the battery cells 11a and 11b is increased and the temperature of the battery cells 11c and 11d is decreased. Here, the heat sinks 73 connected to the thermoelectric conversion elements 30a to 30h are shared (integrated). This allows, for example, the heat of the heating surface of the heat exchanger 20b on the thermoelectric conversion element 30b side to be conducted to the heat sink 73, while the heat absorption surface of the heat exchanger 20a on the thermoelectric conversion element 30a side to absorb heat from the heat sink 73. This allows the temperatures of the battery cells 11a to 11d to be equalized with minimal heat loss.

[0091] (2-2. Example of operation of control device) The differences between the example of operation of the control device 40 according to this embodiment and the first embodiment are as follows. That is, when the determination unit 43 determines that the temperature of the battery cell 11 exceeds the target temperature range, the control unit 45 turns on the switches SW1 and SW4 of the H-bridge circuit and turns off the switches SW2 and SW3 so that the temperature of the battery cell 11 that exceeds the target temperature range falls within the target temperature range. At this time, the control unit 45 appropriately controls the amount of current flowing through the thermoelectric conversion element 30 based on the amount of deviation of the temperature of the battery cell 11 from the target temperature range calculated by the calculation unit 44.

[0092] On the other hand, when the determination unit 43 determines that the temperature of the battery cell 11 is below the target temperature range, the control unit 45 turns on the switches SW2 and SW3 in the H-bridge circuit and turns off the switches SW1 and SW4 so that the temperature of the battery cell 11 falls within the target temperature range. At this time, the control unit 45 appropriately controls the amount of current flowing through the thermoelectric conversion element 30 based on the deviation of the temperature of the battery cell 11 from the target temperature range calculated by the calculation unit 44.

[0093] As described above, the battery system 100 according to this embodiment differs from the first embodiment mainly in the following respects. Specifically, the exterior housing of each of the plurality of battery cells 11 includes a first main surface S1 and a second main surface S2 facing the first main surface S1. The heat exchanger 20 is in thermal contact with the first main surface S1 of a corresponding first battery cell among the plurality of battery cells 11 and the second main surface S2 of a corresponding second battery cell among the plurality of battery cells 11. The control device 40 further controls the current flow direction of the plurality of thermoelectric conversion elements 30 based on the temperatures of the plurality of battery cells 11. The plurality of heat exchangers 20 transfer heat along a direction (X or Y) perpendicular to the vehicle height direction Z and in a direction corresponding to the current flow direction.

[0094] With this configuration, the direction of current flow in the thermoelectric conversion elements 30 is also controlled, so that one thermoelectric conversion element 30 has both cooling and heating functions, making it possible to freely select cooling or heating of the battery cells 11. As a result, the number of heat exchangers 20 and thermoelectric conversion elements 30 can be reduced compared to the first embodiment, making it possible to provide a more compact battery system 100 at low cost.

[0095] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art to which the present disclosure pertains can conceive of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. For example, the functions included in each component or step can be rearranged so as not to be logically inconsistent, and multiple components or steps can be combined or divided into one.

[0096] The technology disclosed herein can also be realized as a vehicle 1 equipped with the control device 40 described in the above-mentioned embodiment, a control method executed by the control device 40, a computer program that causes a computer to function as the above-mentioned control device 40, and a non-temporary tangible recording medium on which the computer program is recorded.

[0097] 1: vehicle, 100: battery system, 10: battery pack, 11: battery cell, 15: pressure plate, 20: heat exchanger, 21: cooling heat exchanger, 22: heating heat exchanger, 30: thermoelectric conversion element, 31: cooling thermoelectric conversion element, 32: heating thermoelectric conversion element, 40: control device, 41: processing unit, 42: acquisition unit, 43: determination unit, 44: calculation unit, 45: control unit, 46: memory unit, 70: heat absorber, 80: recovery device

Claims

1. A battery system comprising: an assembled battery formed by stacking a plurality of pouch-shaped battery cells, each of which has a flat exterior body and in which battery materials including electrodes and electrolytes are sealed; a plurality of flat heat exchangers, each of which is disposed between corresponding ones of the plurality of battery cells and exchanges heat with the corresponding one of the plurality of battery cells; a plurality of thermoelectric conversion elements, each of which is connected to a corresponding one of the plurality of heat exchangers; and a control device that controls the amount of current flowing through each of the plurality of thermoelectric conversion elements based on the temperatures of the plurality of battery cells.

2. The battery system according to claim 1, wherein the exterior body of each of the plurality of battery cells includes a first main surface and a second main surface opposite the first main surface, the plurality of heat exchangers include a plurality of cooling heat exchangers and a plurality of heating heat exchangers, the main surface of a corresponding one of the plurality of cooling heat exchangers is in thermal contact with the first main surface of the exterior body, and the heat absorption surface of the thermoelectric conversion element is in thermal contact with the corresponding cooling heat exchanger, the main surface of a corresponding one of the plurality of heating heat exchangers is in thermal contact with the second main surface of the exterior body, and the heating surface of the thermoelectric conversion element is in thermal contact with the corresponding heating heat exchanger, and the plurality of heat exchangers transfer heat from the lower side to the upper side in the vehicle height direction.

3. The battery system described in claim 1, wherein the exterior body of each of the plurality of battery cells includes a first main surface and a second main surface opposite the first main surface, the heat exchanger is in thermal contact with the first main surface of a corresponding first battery cell among the plurality of battery cells and the second main surface of a corresponding second battery cell among the plurality of battery cells, the control device further controls the current flow direction of the plurality of thermoelectric conversion elements based on the temperatures of the plurality of battery cells, and the plurality of heat exchangers transfer heat along a direction perpendicular to the vehicle height direction and in a direction corresponding to the current flow direction.

4. The battery system according to claim 1, further comprising a pressure plate that applies a load from both ends of the battery pack in the stacking direction of the plurality of battery cells.

5. The battery system according to claim 1, further comprising: a heat absorber connected to the thermoelectric conversion element; and a recovery device that recovers the heat absorbed by the heat absorber as electric power.

Images