Secondary batteries and secondary battery heating systems

Abstract

To provide a secondary battery and a secondary battery heating system, which suppress temperature unevenness, thereby capable of sufficiently suppressing a drop in output.SOLUTION: A secondary battery 10 includes a first current collector 1, a separator 3, and a second current collector 2 in order in a thickness direction. The first current collector 1 includes a first negative electrode active material layer 11, a first current collector layer 12, and a first positive electrode active material layer 13 in order in the thickness direction. The second current collector 2 includes a second negative electrode active material layer 21, a second current collector layer 22, and a second positive electrode active material layer 23 in order in the thickness direction. A first heater 15 is partially arranged on one side 12S of the first current collector layer 12. A second heater 24 is partially arranged on one side 22S of the second current collector layer 22. The second heater 24 is located on an opposite side of the first heater 15 with respect to the separator 3. The first heater 15 includes a non-overlapping area 15A. The non-overlapping area 15 is an area where the first heater 15 and the second heater 24 does not overlap with each other in the thickness direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a secondary battery and a secondary battery heating system.

Background Art

[0002] A secondary battery including a first current collector, a separator, and a second current collector in this order in the thickness direction is known (see, for example, Patent Document 1). In the secondary battery of Patent Document 1, the first current collector includes a first negative electrode active material layer, a first current collector layer, and a first positive electrode active material layer in this order in the thickness direction. The second current collector includes a second negative electrode active material layer, a second current collector layer, and a second positive electrode active material layer in this order in the thickness direction.

[0003] And in the secondary battery described in Patent Document 1, the first current collector includes a first heater. Thereby, a decrease in the output of the secondary battery is suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] There is a desire to further suppress a decrease in the output of a secondary battery. Therefore, it has been attempted to provide a second heater to the second current collector. When the second heater includes only a region overlapping with the first heater in the thickness direction, temperature unevenness occurs in the secondary battery. Then, there is a problem that a decrease in the output cannot be sufficiently suppressed.

[0006] The present invention provides a secondary battery and a secondary battery heating system that can suppress temperature unevenness and sufficiently suppress a decrease in output.

Means for Solving the Problems

[0007] The present invention [1] comprises a first current collector, a separator, and a second current collector in order in the thickness direction, the first current collector comprises a first negative electrode active material layer, a first current collector layer, and a first positive electrode active material layer in order in the thickness direction, the second current collector comprises a second negative electrode active material layer, a second current collector layer, and a second positive electrode active material layer in order in the thickness direction, the first current collector layer and the second current collector layer overlap when projected in the thickness direction, and the first current collector comprises one side or the other side of the first current collector layer in the thickness direction The secondary battery includes a partially arranged first heater which is capable of generating heat when the first current collector layer is energized, and the second current collector is a second heater which is partially arranged with respect to one or the other surface of the second current collector layer in the thickness direction and is capable of generating heat when energized, and is located in the thickness direction opposite to the first heater with respect to the separator, and the first heater includes a region that does not overlap with the second heater when projected in the thickness direction.

[0008] In the secondary battery of the present invention, the first heater includes a region that does not overlap with the second heater when projected in the thickness direction. Therefore, even when the first and second heaters are heated, temperature unevenness is suppressed. As a result, the secondary battery can sufficiently suppress a decrease in output.

[0009] The present invention [2] relates to a secondary battery as described in [1], a temperature sensor for measuring the surface temperature of the secondary battery, a first circuit including a first heater in the secondary battery, comprising a first power supply, a first resistor having an inherent voltage drop based on the drive of the first power supply, a first voltage sensor capable of measuring the voltage drop of the first resistor, and a first switch capable of opening and closing the first circuit, and a second circuit including a second heater in the secondary battery, comprising a second power supply, a second resistor having an inherent voltage drop based on the drive of the second power supply, and a second voltage sensor capable of measuring the voltage drop of the second resistor. A secondary battery heating system comprising: a second circuit comprising a second switch capable of opening and closing the second circuit; a control unit capable of opening and closing the first switch and the second switch, the control unit being connected to the temperature sensor, the first voltage sensor, the first switch, the second voltage sensor, and the second switch, wherein the control unit performs the steps of: (1) determining whether the surface temperature of the secondary battery measured by the temperature sensor is below a first temperature; and (2) determining whether the surface temperature of the secondary battery measured by the temperature sensor is below a first temperature. If it is determined that the temperature is lower, step (2) calculates the internal resistance of the first heater from the drive voltage of the first power supply and the voltage drop across the first resistor, and the internal resistance of the second heater from the drive voltage of the second power supply and the voltage drop across the second resistor, step (3) estimates the temperature of the first heater from the internal resistance of the first heater calculated in step (2), and the temperature of the second heater from the internal resistance of the second heater, and the temperature of the first heater estimated in step (3), and the temperature estimated by the estimation program (2) Step (4) to determine whether the temperature of the second heater is below a predetermined value; Step (5) to determine whether the temperature difference between the first heater and the second heater is greater than or equal to a predetermined value, if the temperature of the first heater and the second heater are determined to be below a predetermined value in step (4); Step (6) to open and close the first switch and the second switch so that the heater with the lower temperature is heated, if the temperature difference between the first heater and the second heater is determined to be greater than or equal to a predetermined value in step (5);The secondary battery heating system includes a step (7) in which, if the temperature difference between the first heater and the second heater is determined to be less than a predetermined value by step (5), the first switch and the second switch are closed so that both the first heater and the second heater are heated.

[0010] In the secondary battery heating system of the present invention, in step (6), if it is determined in step (5) that the temperature difference between the first heater and the second heater is greater than or equal to a predetermined value, the first switch and the second switch are opened and closed so that the heater with the lower temperature is heated. This makes it possible to keep the temperature difference between the first heater and the second heater below the predetermined value. As a result, temperature unevenness is suppressed. Consequently, the secondary battery heating system can sufficiently suppress the decrease in output. [Effects of the Invention]

[0011] The secondary battery and secondary battery heating system of the present invention can suppress temperature unevenness and sufficiently suppress the decrease in output. [Brief explanation of the drawing]

[0012] [Figure 1] This is an exploded perspective view of one embodiment of the secondary battery of the present invention. [Figure 2] Figure 1 is a cross-sectional view of the XX line of the secondary battery shown. [Figure 3] This is a schematic diagram of one embodiment of the secondary battery heating system of the present invention. [Figure 4] This is a flowchart of the control unit. [Figure 5] This is a partially disassembled perspective view of a modified secondary battery. [Figure 6] This is a disassembled perspective view of a modified secondary battery. [Figure 7] This is a disassembled perspective view of a modified secondary battery. [Figure 8] This is a disassembled perspective view of a modified secondary battery. [Modes for carrying out the invention]

[0013] 1. An embodiment of a secondary battery Referring to FIGS. 1 and 2, an embodiment of the secondary battery of the present invention will be described.

[0014] As shown in FIGS. 1 and 2, in this embodiment, the secondary battery 10 has a thickness. The secondary battery 10 extends in the plane direction. The plane direction is orthogonal to the thickness direction. The secondary battery 10 has a sheet shape. In this embodiment, the secondary battery 10 is, for example, a lithium secondary battery, and preferably a lithium ion secondary battery.

[0015] 1.1 Layer structure of the secondary battery 10 The secondary battery 10 includes a first current collector 1, a separator 3, and a second current collector 2 in this order in the thickness direction. In the secondary battery 10, the first current collector 1, the separator 3, and the second current collector 2 are arranged in this order toward one side in the thickness direction.

[0016] 1.2 The first current collector 1 The first current collector 1 extends in the plane direction. The first current collector 1 has a sheet shape. As shown in FIG. 2, the first current collector 1 includes a first negative electrode active material layer 11, a first current collector layer 12, and a first positive electrode active material layer 13 in this order toward one side in the thickness direction.

[0017] 1.2.1 The first negative electrode active material layer 11 The first negative electrode active material layer 11 is disposed at the other end of the first current collector 1 in the thickness direction. The first negative electrode active material layer 11 has a thin film shape. Examples of the material of the first negative electrode active material layer 11 include carbon.

[0018] 1.2.2 The first current collector layer 12 The first current collector layer 12 is disposed on one surface of the first negative electrode active material layer 11 in the thickness direction. In other words, the first negative electrode active material layer 11 is disposed on the other surface of the first current collector layer 12 in the thickness direction. The first current collector layer 12 contacts one surface of the first negative electrode active material layer 11 in the thickness direction.

[0019] The first current collector layer 12 has a sheet shape. The first current collector layer 12 extends in the planar direction. In this embodiment, the first current collector layer 12 has a rectangular shape. Examples of materials for the first current collector layer 12 include aluminum, copper, stainless steel, and nickel.

[0020] 1.2.3 First positive electrode active material layer 13 As shown in Figure 2, the first positive electrode active material layer 13 is positioned on one side of the first current collector layer 12 in the thickness direction. The first positive electrode active material layer 13 is positioned on the opposite side of the first negative electrode active material layer 11 from the first current collector layer 12. The first positive electrode active material layer 13 is in contact with a portion of one side of the first current collector layer 12 in the thickness direction. The first positive electrode active material layer 13 has a pattern that ensures space for the first heater 15, which will be described later, to be positioned on the first current collector layer 12. The first positive electrode active material layer 13 has a thin film shape. Examples of materials for the first positive electrode active material layer 13 include lithium composite oxides. Examples of lithium composite oxides include lithium manganese oxide, lithium nickelate, lithium iron phosphate, and lithium cobaltate.

[0021] 1.3 Separator 3 The separator 3 is positioned on one side of the first positive electrode active material layer 13 in the thickness direction. The separator 3 is located on the opposite side of the first current collector layer 12 from the first positive electrode active material layer 13. The separator 3 is in contact with one side of the first positive electrode active material layer 13 in the thickness direction. The separator 3 has a sheet shape. The separator 3 extends in the planar direction. Examples of materials for the separator 3 include glass, cellulose, polyolefin, and polyester.

[0022] 1.4 Second current collector 2 The second current collector 2 is positioned on one side of the separator 3 in the thickness direction. The second current collector 2 is positioned on one side of the separator 3 in the thickness direction. The second current collector 2 comprises, in order in the thickness direction, a second negative electrode active material layer 21, a second current collector layer 22, and a second positive electrode active material layer 23.

[0023] 1.4.1 Second negative electrode active material layer 21 The second negative electrode active material layer 21 is positioned at the other end of the second current collector 2 in the thickness direction. The second negative electrode active material layer 21 is positioned on one side of the separator 3 in the thickness direction. The second negative electrode active material layer 21 is positioned on the opposite side of the separator 3 from the first positive electrode active material layer 13. The second negative electrode active material layer 21 is in contact with one side of the separator 3 in the thickness direction. The material of the second negative electrode active material layer 21 is the same as the material of the first negative electrode active material layer 11.

[0024] 1.4.2 Second current collector layer 22 The second current collector layer 22 is positioned on one side of the second negative electrode active material layer 21 in the thickness direction. In other words, the second negative electrode active material layer 21 is positioned on the other side of the second current collector layer 22 in the thickness direction. The second current collector layer 22 is in contact with one side of the second negative electrode active material layer 21 in the thickness direction. The second current collector layer 22 is positioned on the opposite side of the separator 3 from the second negative electrode active material layer 21. The second current collector layer 22 extends in the plane direction. The first current collector layer 12 and the second current collector layer 22 overlap when projected in the thickness direction. The first current collector layer 12 includes a region (or only a region) that overlaps with the second current collector layer 22 in the thickness direction. The shape of the second current collector layer 22 is the same as the shape of the first current collector layer 12.

[0025] 1.4.3 Second positive electrode active material layer 23 The second positive electrode active material layer 23 is positioned on one side of the second current collector layer 22 in the thickness direction. The second positive electrode active material layer 23 is positioned on the opposite side of the second negative electrode active material layer 21 from the second current collector layer 22. The second positive electrode active material layer 23 is in contact with a portion of one side of the second current collector layer 22 in the thickness direction. The second positive electrode active material layer 23 has a pattern that ensures space for the second heater 24, which will be described later, to be positioned on the second current collector layer 22. The material of the second positive electrode active material layer 23 is the same as the material of the first positive electrode active material layer 13.

[0026] 1.5 First heater 15 and second heater 24 The first current collector 1 further comprises a first heater 15. The second current collector 2 further comprises a second heater 24.

[0027] The first heater 15 is partially positioned on one side 12S or the other side of the first current collector layer 12 in the thickness direction. In this embodiment, the first heater 15 is partially positioned on one side 12S of the first current collector layer 12 in the thickness direction. The first heater 15 is also positioned on the other side of the separator 3 in the thickness direction. The first heater 15 is capable of generating heat when energized. The first heater 15 is, for example, a heating wire. As shown in Figure 1, in this embodiment, the first heater 15 has a roughly cross shape when projected in the thickness direction. The central part 15C of the first heater 15 is positioned in the central part of one side 12S of the first current collector layer 12.

[0028] In this embodiment, the first heater 15 comprises a first rib portion 151 and a second rib portion 152. The first rib portion 151 is positioned in the center of one surface 12S in a first direction. The first direction is perpendicular to the thickness direction. The first rib portion 151 is aligned with a second direction. The second direction is perpendicular to both the thickness direction and the first direction.

[0029] The second crossbar 152 is positioned in the center of one surface 12S in the second direction. The second crossbar 152 is aligned with the first direction. The first crossbar 151 has an intersection with the second crossbar 152. At the intersection, the first crossbar 151 and the second crossbar 152 overlap in the thickness direction. The intersection is located in the central part 15C of the first heater 15.

[0030] The second heater 24 is partially positioned on one side 22S or the other side of the second current collector layer 22 in the thickness direction. In this embodiment, the second heater 24 is partially positioned on one side 22S of the second current collector layer 22 in the thickness direction. The second heater 24 is positioned on one side of the separator 3 in the thickness direction. The second heater 24 is capable of generating heat when energized. In this embodiment, the second heater 24 is, for example, a heating wire. As shown in Figure 2, the second heater 24 is located on the opposite side of the first heater 15 from the separator 3 in the thickness direction. In a projection plane projected in the first direction (or second direction), the first heater 15, the separator 3, and the second heater 24 are arranged in order in the thickness direction.

[0031] In this embodiment, the second heater 24 has a substantially grid shape when projected in the thickness direction. The second heater 24 is positioned at the peripheral end of one side 22S of the second current collector layer 22. As shown in Figure 1, in this embodiment, the second heater 24 comprises two third struts 241, 242 and two fourth struts 243, 244.

[0032] The third rib section 241 is positioned at one end of one surface 22S in the first direction. The third rib section 241 is aligned with the second direction.

[0033] The third rib section 242 is positioned at the other end of one surface 22S in the first direction. The third rib section 242 is spaced apart from the third rib section 241 in the first direction. The third rib section 241 is aligned in the second direction.

[0034] The fourth rib section 243 is positioned at one end of one surface 22S in the second direction. The fourth rib section 243 is aligned with the first direction.

[0035] The fourth rib section 244 is positioned at the other end of one surface 22S in the second direction. The fourth rib section 244 is spaced apart from the fourth rib section 243 in the second direction. The fourth rib section 244 is aligned with the first direction.

[0036] The third crossbar 241 has an intersection with the fourth crossbar 243. The intersection of the third crossbar 241 overlaps with the fourth crossbar 243 in the thickness direction.

[0037] The third rib section 241 has an intersection with the fourth rib section 244. The intersection of the third rib section 241 overlaps with the fourth rib section 244 in the thickness direction.

[0038] The third crossbar 242 has an intersection with the fourth crossbar 243. The intersection of the third crossbar 242 overlaps with the fourth crossbar 243 in the thickness direction.

[0039] The third rib section 242 has an intersection with the fourth rib section 244. The intersection of the third rib section 242 overlaps with the fourth rib section 244 in the thickness direction.

[0040] The four intersection points mentioned above are located at the four corners of one side 22S.

[0041] The first heater 15 includes a non-overlapping region 15A and an overlapping region 15B. The non-overlapping region 15A is shown by hatching in Figure 1. The non-overlapping region 15A is the region in the thickness direction where the first heater 15 and the second heater 24 do not overlap. In other words, the first heater 15 has a different arrangement from the second heater 24. The non-overlapping region 15A includes the central portion 15C. The non-overlapping region 15A includes the intermediate portion of the first rib portion 151 in the second direction and the intermediate portion of the second rib portion 152 in the first direction. The intermediate portion is the region between the ends of each rib portion.

[0042] The overlapping region 15B includes both ends of the first rib section 151 in the second direction and both ends of the second rib section 152 in the first direction.

[0043] 1.6 First insulating film, second insulating film, and exterior material 16 In addition to the first current collector 1, separator 3, and second current collector 2, the secondary battery 10 further comprises a first insulating film (not shown), a second insulating film (not shown), an outer casing material 16, and an electrolyte 4.

[0044] A first insulating film (not shown) is disposed on the surface of the first heater 15. The surface includes one side, the other side, and the circumferential side of the first heater 15 in the thickness direction. The first insulating film disposed on the other side of the first heater 15 insulates the first current collector layer 12 from the first heater 15.

[0045] A second insulating film, not shown, is disposed on the surface of the second heater 24. The surface includes one side, the other side, and the circumferential side of the second heater 24 in the thickness direction. The second insulating film disposed on the other side of the second heater 24 insulates the second current collector layer 22 from the second heater 24.

[0046] The outer casing 16 houses the first current collector 1, the second current collector 2, and the electrolyte 4, which will be described below. Parts of the first current collector layer 12 and the second current collector layer 22 may be exposed from the outer casing 16. These parts serve as terminals.

[0047] The electrolyte 4 is in contact with the first negative electrode active material layer 11, the first positive electrode active material layer 13, the separator 3, the second negative electrode active material layer 21, and the second positive electrode active material layer 23 described above. A first insulating film (not shown) is interposed between the electrolyte 4 and the first heater 15. A second insulating film (not shown) is interposed between the electrolyte 4 and the second heater 24. Examples of the electrolyte 4 include an organic electrolyte. The organic electrolyte includes, for example, an organic solvent and a lithium salt.

[0048] In the secondary battery 10, although not shown, one or more additional current collectors may be stacked on the other side of the first current collector 1 and on one side of the second current collector 2 in the thickness direction. One unit consisting of a positive electrode active material layer, a separator, and a negative electrode active material layer arranged sequentially in the thickness direction constitutes one cell. There may be multiple cells. This secondary battery 10 may have multiple cells.

[0049] 2. Secondary battery heating system 20 Referring to Figure 3, the secondary battery heating system 20, which includes the secondary battery 10 described above, will be explained.

[0050] As shown in Figure 3, the secondary battery heating system 20 comprises a secondary battery 10 (see Figures 1 and 2), a temperature sensor 5 (see Figure 2), a first circuit 6, a second circuit 7, and a control unit 8.

[0051] 2.1 Temperature Sensor 5 The temperature sensor 5 measures the surface temperature of the secondary battery 10. In this embodiment, the temperature sensor 5 is placed, for example, on the surface (outer surface) of the exterior material 16.

[0052] 2.2 First circuit 6 The first circuit 6 comprises a first power supply 61, a first heater 15, a first resistor 62, a first voltage sensor 63, and a first switch 64.

[0053] The first power supply 61 can supply power to the first heater 15.

[0054] The first heater 15 is connected in series to the first power supply 61 via the first line 65.

[0055] The first resistor 62 has an inherent voltage drop based on the drive of the first power supply 61. The resistance value of the first resistor 62 is lower than the internal resistance of the first heater 15. The first resistor 62 is connected in series with the first heater 15 and the first power supply 61 via the first line 65.

[0056] The first voltage sensor 63 is capable of measuring the voltage drop across the first resistor 62. The first voltage sensor 63 is connected in parallel to the first resistor 62 via the first line 65. The first voltage sensor 63 is, for example, a voltmeter.

[0057] The first switch 64 can open and close the first circuit 6. The first switch 64 is interposed between the first power supply 61 and the first heater 15.

[0058] 2.3 Second circuit 7 The second circuit 7 includes a second power supply 71, a second heater 24, a second resistor 72, a second voltage sensor 73, and a second switch 74.

[0059] The second power supply 71 can supply power to the second heater 24.

[0060] The second heater 24 is connected in series to the second power supply 71 via the second line 75.

[0061] The second resistor 72 has an inherent voltage drop based on the drive of the second power supply 71. The second resistor 72 is connected in series with the second heater 24 and the second power supply 71 via the second line 75.

[0062] The second voltage sensor 73 is capable of measuring the voltage drop across the second resistor 72. The second voltage sensor 73 is connected in parallel to the second resistor 72 via the second line 75. The second voltage sensor 73 is, for example, a voltmeter.

[0063] The second switch 74 can open and close the second circuit 7. The second switch 74 is interposed between the second power supply 71 and the second heater 24.

[0064] 2.5 Control Unit 8 The control unit 8 can open and close the first switch 64 and the second switch 74. The control unit 8 is, for example, an ECU (Electronic Control Unit). The control unit 8 is connected to the temperature sensor 5 (see Figure 2), the first voltage sensor 63, the first switch 64, the second voltage sensor 73, and the second switch 74.

[0065] As shown in Figure 4, the control unit 8 is capable of executing steps (1), (2), (3), (4), (5), (6), and (7). The control unit 8 includes a memory storing a program capable of executing steps (1) to (7), and an arithmetic unit capable of executing the program.

[0066] 2.5.1 Step (1) In step (1), it is determined whether the surface temperature of the secondary battery 10 measured by the temperature sensor 5 is below the first temperature T0 (S1). The first temperature T0 is the temperature at which the discharge performance of the secondary battery 10 decreases. The first temperature T0 is, for example, 10°C or higher and, for example, 25°C or lower.

[0067] 2.5.2. Step (2) In step (2), if it is determined in step (1) that the surface temperature of the secondary battery 10 measured by the temperature sensor 5 is less than or equal to the first temperature T0 (S1: Yes), the internal resistance of the first heater 15 and the internal resistance of the second heater 24 are calculated (S2).

[0068] The internal resistance of the first heater 15 is determined from the drive voltage of the first power supply 61 and the voltage drop across the first resistor 62. Specifically, the internal resistance of the first heater 15 is determined by subtracting the voltage drop across the first resistor 62 from the drive voltage of the first power supply 61. The drive voltage of the first power supply 61 is known. The voltage drop across the first resistor 62 is measured by the first voltage sensor 63.

[0069] The internal resistance of the second heater 24 is determined from the drive voltage of the second power supply 71 and the voltage drop across the second resistor 72. The internal resistance of the second heater 24 is determined by subtracting the voltage drop across the second resistor 72 from the drive voltage of the second power supply 71. The drive voltage of the second power supply 71 is known. The voltage drop across the second resistor 72 is measured by the second voltage sensor 73.

[0070] If the temperature sensor 5 determines that the surface temperature of the secondary battery 10 exceeds the first temperature T0 (S1: No), the control unit 8 does not control the temperatures of the first heater 15 and the second heater 24.

[0071] 2.5.3 Step (3) In step (3), the temperature H1 of the first heater 15 is estimated from the internal resistance of the first heater 15 calculated in step (2), and the temperature H2 of the second heater is estimated from the internal resistance of the second heater (S3).

[0072] The internal resistance of the first heater 15 and the temperature H1 of the first heater 15 are correlated. Specifically, as the temperature H1 of the first heater 15 decreases, the internal resistance of the first heater 15 decreases. Based on the correlation described above, the temperature H1 of the first heater 15 is estimated from the internal resistance of the first heater 15.

[0073] The internal resistance of the second heater 24 and the temperature H2 of the second heater 24 are correlated. Specifically, as the temperature H2 of the second heater 24 decreases, the internal resistance of the second heater 24 decreases. Based on the correlation described above, the temperature H2 of the second heater 24 is estimated from its internal resistance.

[0074] 2.5.4 Step (4) In step (4), it is determined whether the temperature H1 of the first heater 15 estimated in step (3) and the temperature H2 of the second heater 24 estimated by the estimation program (2) are less than or equal to the second temperature T2 (S4). The second temperature T2 is, for example, 10°C or higher and 25°C or lower.

[0075] 2.5.5. Step (5) In step (5), if it is determined in step (4) that the temperature H1 of the first heater 15 and the temperature H2 of the second heater 24 are both below a predetermined value (S4: Yes), it is determined whether the temperature difference (|H1-H2|) between the first heater 15 and the second heater 24 is greater than or equal to a predetermined value (S5). The predetermined value is, for example, 5°C or more and 20°C or less.

[0076] If step (4) determines that the temperature H1 of the first heater 15 and the temperature H2 of the second heater 24 are below a predetermined value (S4: No), the control unit 8 does not control the temperatures of the first heater 15 and the second heater 24.

[0077] 2.5.6 Step (6) In step (6), if it is determined in step (5) that the temperature difference between the first heater 15 and the second heater 24 is greater than or equal to a predetermined value (S5: Yes), the first switch 64 and the second switch 74 are opened and closed so that the heater with the lower temperature is heated (S6). Specifically, if temperature H1 is lower than temperature H2, the first switch 64 is closed and the second switch 74 is opened. If temperature H2 is lower than temperature H1, the first switch 64 is opened and the second switch 74 is closed.

[0078] 2.5.7 Step (7) In step (7), if it is determined in step (5) that the temperature difference between the first heater 15 and the second heater 24 is less than a predetermined value (S5: No), the first switch 64 and the second switch 74 are closed so that both the first heater 15 and the second heater 24 are heated (S7).

[0079] 3. Effects of one embodiment In this secondary battery 10, the first heater 15 includes a non-overlapping region 15A that does not overlap with the second heater 24 when projected in the thickness direction. Therefore, even when the first heater 15 and the second heater 24 are heated, temperature unevenness is suppressed. As a result, the secondary battery 10 can sufficiently suppress the decrease in output.

[0080] In this secondary battery heating system 20, in step (6), if it is determined in step (5) that the temperature difference (|H1-H2|) between the first heater 15 and the second heater 24 is greater than or equal to a predetermined value, the first switch 64 and the second switch 74 are opened and closed so that the heater with the lower temperature is heated. This makes it possible to keep the temperature difference between the first heater 15 and the second heater 24 below the predetermined value. As a result, temperature unevenness is suppressed. Consequently, the secondary battery heating system 20 can sufficiently suppress the decrease in output.

[0081] 4. Variations In the following modifications, the same reference numerals are used for components and processes as in the above-described embodiment, and their detailed descriptions are omitted. Furthermore, the modifications can achieve the same effects and advantages as the first embodiment, unless otherwise specified. Moreover, the first embodiment and its modifications can be combined as appropriate.

[0082] (1) Although not shown in the figures, the first heater 15 may be arranged on the other side of the first current collector layer 12 in the thickness direction.

[0083] The second heater 24 may be arranged on the other side of the second current collector layer 22 in the thickness direction.

[0084] (2) As shown in Figure 5, the secondary battery 10 may have a cylindrical shape. The first current collector 1 and the second current collector 2 are wound. In this modified secondary battery 10, the first current collector 1 and the second current collector 2 are arranged in a repeating sequence from the radial center outwards.

[0085] (3) As shown in Figure 6, the first heater 15 may have an X shape on one side 12S.

[0086] The first rib section 151 is aligned along the third direction. The third direction is included in the plane direction. The third direction intersects the first and second directions.

[0087] The second rib section 152 is aligned with the fourth direction. The fourth direction is included in the planar direction. The fourth direction intersects the first, second, and third directions. For example, the fourth direction is perpendicular to the third direction.

[0088] (4) As shown in Figure 7, each of the first heater 15 and the second heater 24 may have a sinusoidal shape. The phase of the second heater 24 is shifted from the phase of the first heater 15 when projected in the thickness direction. The period of the shift is not limited. In this modified example, the second heater 24 is, for example, shifted from the first heater 15 by half a period. In this case, the second heater 24 has a sinusoidal curve and the first heater 15 has a cosine curve.

[0089] (5) As shown in Figure 8, the first heater 15 is provided only by a plurality of first struts 151, and the second heater 24 is provided only by a plurality of fourth struts 243.

[0090] Each of the multiple first rails 151 extends in a first direction. The multiple first rails 151 are spaced apart from each other in a second direction.

[0091] Each of the multiple fourth bars 243 extends in a first direction. The multiple fourth bars 243 are spaced apart from each other in a second direction.

[0092] Furthermore, the first heater 15 has a non-overlapping region 15A and no overlapping region 15B. When projected in the thickness direction, the first rib portion 151 and the fourth rib portion 243 are aligned sequentially in the second direction. [Explanation of symbols]

[0093] 10 Secondary battery 1. First current collector 11 First negative electrode active material layer 12. First current collector layer 13 First positive electrode active material layer 14 Separator 15. First heater 15A Non-overlapping area 2. Second current collector 21 Second negative electrode active material layer 22 Second current collector layer 23 Second positive electrode active material layer 24. Second heater 5. Temperature sensor 6 1st circuit 61 1st power supply 62 1st resistance 63. First voltage sensor 64. First switch 7 Second circuit 71 2nd power supply 72 2nd resistor 73. Second voltage sensor 74 Second switch 8 Control Unit T0 1st temperature H1 Temperature (First heater) H2 Temperature (Second Heater)

Claims

1. The device is provided with a first current collector, a separator, and a second current collector in order in the thickness direction. The first current collector comprises, in order in the thickness direction, a first negative electrode active material layer, a first current collector layer, and a first positive electrode active material layer. The second current collector comprises, in the thickness direction, a second negative electrode active material layer, a second current collector layer, and a second positive electrode active material layer, in that order. The first current collector layer and the second current collector layer overlap when projected in the thickness direction. The first current collector further comprises a first heater which is partially arranged with respect to one or the other surface of the first current collector layer in the thickness direction, and which is capable of generating heat when the first current collector layer is energized. The second current collector is a second heater partially arranged on one or the other surface of the second current collector layer in the thickness direction, and is a second heater capable of generating heat when energized, further comprising a second heater located on the opposite side of the first heater from the separator in the thickness direction. The first heater includes a region that does not overlap with the second heater when projected in the thickness direction, and is a secondary battery.

2. The secondary battery according to claim 1, A temperature sensor for measuring the surface temperature of the secondary battery, A first circuit including a first heater in the secondary battery, comprising: a first power supply; a first resistor having a unique voltage drop based on the drive of the first power supply; a first voltage sensor capable of measuring the voltage drop across the first resistor; and a first switch capable of opening and closing the first circuit, A second circuit including a second heater in the secondary battery, comprising: a second power supply; a second resistor having an inherent voltage drop based on the drive of the second power supply; a second voltage sensor capable of measuring the voltage drop across the second resistor; and a second switch capable of opening and closing the second circuit. A secondary battery heating system comprising a control unit capable of opening and closing the first switch and the second switch, the temperature sensor, the first voltage sensor, the first switch, the second voltage sensor, and a control unit connected to the second switch, The control unit, Step (1) to determine whether the surface temperature of the secondary battery measured by the temperature sensor is below a first temperature, If, in step (1), it is determined that the surface temperature of the secondary battery measured by the temperature sensor is below the first temperature, step (2) is performed to calculate the internal resistance of the first heater from the drive voltage of the first power supply and the voltage drop across the first resistor, and the internal resistance of the second heater from the drive voltage of the second power supply and the voltage drop across the second resistor. Step (3) involves estimating the temperature of the first heater from the internal resistance of the first heater calculated in step (2), and the temperature of the second heater from the internal resistance of the second heater, Step (4) is to determine whether the temperature of the first heater estimated in step (3) and the temperature of the second heater estimated by the estimation program (2) are each less than or equal to a predetermined value. If, in step (4), it is determined that the temperature of the first heater and the temperature of the second heater are each below a predetermined value, then step (5) is to determine whether the temperature difference between the first heater and the second heater is above a predetermined value, If step (5) determines that the temperature difference between the first heater and the second heater is greater than or equal to a predetermined value, step (6) is to open and close the first switch and the second switch so that the heater with the lower temperature is heated, A secondary battery heating system capable of performing the step (7) of closing the first switch and the second switch so that both the first heater and the second heater are heated, if it is determined by step (5) that the temperature difference between the first heater and the second heater is less than a predetermined value.

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