Abstract
The present invention relates to a device for measuring the thermal characteristics of a pouch-type battery cell, specifically, the thermal conductivity of the battery cell, and a thermal conductivity measurement method using the same. When the battery cell thermal conductivity measurement device of the present invention is used, the thermal conductivity of a pouch-type battery cell exhibiting anisotropic thermal conductivity characteristics can be separated along each direction and measured, and thereby stability according to the thermal characteristics of a product, which uses a battery cell for a rechargeable battery, can be efficiently evaluated.
Claims
1. A method for measuring thermal conductivity of a battery cell by using an apparatus, comprising: calculating an amount of heat applied to the battery cell in an upward direction perpendicular to a hot plate; calculating an amount of heat applied to the battery cell in a downward direction perpendicular to the hot plate; and calculating a thermal conductivity of the battery cell using the amount of heat applied in the upward direction and the amount of heat applied in the downward direction, wherein the apparatus comprising: a hot plate including a heating element; and a guarded hot plate surrounding the hot plate, which is spaced from a side of the hot plate, wherein the apparatus has symmetrical structure about the hot plate by sequentially including a measuring plate, a cooling plate, and a cooling unit on an upper part and a lower part of the hot plate, respectively, in a direction perpendicular to the hot plate, and in a direction away from the hot plate, and wherein a battery cell is disposed between the cooling plate and the measuring plate of the upper part and the lower part, respectively.
2. The method of claim 1, wherein the amount of heat applied to the battery cell in the upward direction perpendicular to the hot plate is calculated by Equation 1 below: wherein in Equation 1 above, P.sub.up denotes an amount of heat applied to a battery cell in an upward direction, T.sub.1 denotes a temperature of one surface facing a hot plate of a measuring plate placed on a top of the hot plate, T.sub.2 denotes a temperature of the other surface facing the battery cell of the measuring plate placed on the top of the hot plate, T.sub.3 denotes a temperature of one surface facing the hot plate of the measuring plate disposed under the hot plate, T.sub.4 denotes a temperature of the other surface facing the battery cell of the measuring plate placed under the hot plate, i denotes a current applied to the hot plate, and V denotes a voltage applied to the hot plat.
3. The method of claim 1, wherein the amount of heat applied to the battery cell in the downward direction perpendicular to the hot plate is calculated by Equation 2 below: wherein in Equation 2 above, P.sub.down denotes an amount of heat applied to a battery cell in a downward direction, T.sub.1 denotes a temperature of one surface facing a hot plate of a measuring plate placed on a top of the hot plate, T.sub.2 denotes a temperature of the other surface facing the battery cell of the measuring plate placed on the top of the hot plate, T.sub.3 denotes a temperature of one surface facing the hot plate of the measuring plate disposed under the hot plate, T.sub.4 denotes a temperature of the other surface facing the battery cell of the measuring plate placed under the hot plate, i denotes a current applied to the hot plate, and V denotes a voltage applied to the hot plate.
4. The method of claim 1, wherein the thermal conductivity in the upward direction of the battery cell is calculated by Equation 3 below: wherein in Equation 3, k.sub.up denotes a vertical thermal conductivity from a bottom to a top of a battery cell, P.sub.up denotes an amount of heat applied to the battery cell in an upward direction, L.sub.top denotes a thickness of a battery cell, A denotes a unit area for measuring an amount of heat, T.sub.H denotes a temperature at a bottom of a battery cell close to a hot plate, and T.sub.C denotes a temperature at a top of a battery cell close to a cooling plate.
5. The method of claim 1, wherein the thermal conductivity in the downward direction of the battery cell is calculated by Equation 4 below: wherein in Equation 4, k.sub.down denotes a vertical thermal conductivity from a top to a bottom of a battery cell, P.sub.down denotes an amount of heat applied to the battery cell in a downward direction, L.sub.bottom denotes a thickness of a battery cell, A denotes a unit area for measuring an amount of heat, T.sub.H denotes a temperature at a top of a battery cell close to a hot plate, and T.sub.C denotes a temperature at a bottom of a battery cell close to a cooling plate.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 schematically shows a structure seen from the side of an apparatus for measuring thermal conductivity according to a conventional art.
(2) FIG. 2 schematically shows a structure seen from the side of another apparatus for measuring thermal conductivity according to a conventional art.
(3) FIG. 3 shows a structure seen from the side of an apparatus for measuring thermal conductivity according to an embodiment of the present invention.
(4) FIG. 4 is a three-dimensional view of the structure of an apparatus for measuring thermal conductivity according to an embodiment of the present invention.
(5) FIG. 5 shows a structure seen from the side of an apparatus for measuring thermal conductivity according to another embodiment of the present invention.
(6) FIG. 6 is a three-dimensional view of the structure of an apparatus for measuring thermal conductivity according to another embodiment of the present invention.
(7) Hereinafter, the structure of the thermal conductivity measuring apparatus of the present invention will be described in more detail with reference to each drawing.
(8) FIG. 1 shows a conventional thermal conductivity measuring apparatus 10, which is provided with a hot plate 11, a guarded hot plate 12, a measuring plate 13, a guarded plate 14, a cooling plate 16, a heat insulating material 17, a guarded plate 18. Herein, a test piece 15 is disposed on the cooling plate 16. Since the heat generated from the hot plate 11 moves vertically towards the cooling plate 16, heat transfer from the top to the bottom of the test piece 15 occurs. Therefore, this method is applicable only to isotropic materials. In addition, since the heat loss to the side is large, it is possible to grasp the approximate thermal characteristics, but precise measurement is impossible. In addition, the measuring plate 13 does not directly measure the amount of heat generated in the hot plate 11, but serves as a heat insulating material for preventing heat loss in measuring the amount of heat. Therefore, the measuring apparatus 10 of FIG. 1 does not measure the surface temperature in the vertical direction of the measuring plate 13. On the other hand, the measuring plate provided in the measuring apparatus of the present invention is provided in a vertically symmetrical structure unlike a conventional measuring apparatus, and it does not serve as a heat insulating material, but it is used to calculate the amount of heat that moves in the vertical direction of the hot plate as the surface temperature of the measuring plate is directly measured.
(9) FIG. 2 shows another conventional thermal conductivity measuring apparatus 20 which has been further improved compared to the thermal conductivity measuring apparatus 10 of FIG. 1. It includes a hot plate 21, a measuring plate 22, a measuring instrument 23, a guarded plate 24, a guarded hot plate 25, a cooling plate 27, a cooling unit 28 and a heat insulating member 29. A test piece 26 is disposed on the cooling plate 27, and the heat transfer occurs from top to bottom. The heat loss is more suppressed than the thermal conductivity measuring device 10 of FIG. 1. but likewise, only the thermal conductivity in one direction can be measured, so it is not suitable for measuring the thermal conductivity of the battery cell.
(10) FIGS. 3 and 4 show an embodiment of the thermal conductivity measuring apparatus 100 of the present invention. The heat moves vertically upward and downward from the central hot plate 110, and the guarded hot plate 120 is spaced apart from the side of the hot plate 110 to prevent loss in the lateral direction. In addition, an upper measuring plate 131 and a lower measuring plate 132 are provided adjacent to the hot plate in the vertical direction, and the temperatures of the respective surfaces of the upper measuring plate 131 and the lower measuring plate 132 are measured, from which the ratio of the amount of heat transferred in the vertical direction can be checked. Next, an upper cooling plate 141 and a lower cooling plate 142 are disposed, and an upper cooling unit 151 and a lower cooling unit 152 are disposed adjacent thereto to thereby maintain a low temperature of the cooling plate. The upper battery cells 101 and the lower battery cell 102 are disposed in the upward direction and the downward direction, respectively, and the same type of battery cells should be disposed in the same direction in order to separately calculate the thermal conductivity from the lower surface to the upper surface direction and the thermal conductivity from the upper surface to the lower surface direction. Also, a heat insulating member 160 is disposed, covering the side surfaces of the guarded hot plate 120, the upper measuring plates 131, the lower measuring plates 132, the upper cooling plate 141, the lower cooling plate 142, the upper cooling unit 151, the lower cooling unit 152, the upper battery cell 101, and the lower battery cell 102, in a spaced state.
(11) FIGS. 5 and 6 show another embodiment of the thermal conductivity measuring apparatus 200 of the present invention. The heat moves vertically upward and downward from the central hot plate 210, and the guarded hot plate 220 is spaced apart from the side surface of the hot plate 210 to prevent loss in the lateral direction. In addition, an upper measuring plate 231 and a lower measuring plate 232 are provided adjacent to the hot plate in the vertical direction, and the temperatures of the respective surfaces of the upper measuring plate 231 and the lower measuring plate 232 are measured, from which the ratio of the amount of heat transferred in the vertical direction can be checked. In addition, guarded measuring plates 241 and 242 are spaced apart from each side of the upper measuring plate 231 and the lower measuring plate 232, respectively. Through this, it is possible to further reduce the heat loss in the measuring plate, and it is possible to maintain the heat transfer characteristics uniformly. Next, an upper cooling plate 251 and a lower cooling plate 252 are disposed, and an upper cooling unit 261 and a lower cooling unit 262 are disposed adjacent thereto to thereby maintain a low temperature of the cooling plate. The upper battery cell 201 and the lower battery cell 202 are disposed in the upward direction and the downward direction, respectively, and the same type of battery cells should be disposed in the same direction in order to separately calculate the thermal conductivity from the lower surface to the upper surface direction and the thermal conductivity from the upper surface to the lower surface direction. Also, a heat insulating member 270 is disposed, covering the side surfaces of the guarded hot plate 220, the upper guarded measuring plate 241, the lower guarded measuring plate 242, the upper cooling plate 251, the lower cooling plate 252, the upper cooling unit 261, the lower cooling unit 262, the upper battery cell 201, and the lower battery cell 202, in a spaced state.
DESCRIPTION OF REFERENCE NUMERALS
(12) 10: thermal conductivity measuring apparatus 11: hot plate 12: guarded hot plate 13: measuring plate 14: guarded plate 15: test piece 16: cooling plate 17: heat insulating material 18: guarded plate 20: thermal conductivity measuring apparatus 21: hot plate 22: measuring plate 23: measuring instrument 24: guarded plate 25: guarded hot plate 26: test piece 27: cooling plate 28: cooling unit 29: heat insulating material 100: thermal conductivity measuring apparatus 101: upper battery cell 102: lower battery cell 110: hot plate 120: guarded hot plate 131: upper measuring plate 132: lower measuring plate 141: upper cooling plate 142: lower cooling plate 151: upper cooling unit 152: lower cooling unit 160: heat insulating member 200: thermal conductivity measuring apparatus 201: upper battery cell 202: lower battery cell 210: hot plate 220: guarded hot plate 231: upper measuring plate 232: lower measuring plate 241: upper guarded measuring plate 242: lower guarded measuring plate 251: upper cooling plate 252: lower cooling plate 261: upper cooling unit 262: lower cooling unit 270: heat insulating member
