JP2019185845A - Filling member, battery pack and method for controlling heat transfer - Google Patents

Abstract

To suitably control heat transfer between single cells via a cooling member.SOLUTION: Disclosed is a filling member having a thickness direction and a surface direction, and a first surface and a second surface along the surface direction, which is in contact with a plurality of single cells constituting a battery pack on the first surface and also in contact with a cooling member capable of cooling the plurality of single cells. When temperature of any one or more of the plurality of single cells exceeds the temperature in an abnormal heat generation state, the heat transfer sensitivity S is 0.5≤S≤ 4.0.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a filling member, an assembled battery, and a heat transfer control method.

  In recent years, the use of secondary batteries as power sources for vehicles and the like has increased rapidly. The study of increasing the energy density of secondary batteries is underway for the purpose of improving the degree of freedom when mounting in a limited space such as a vehicle and extending the cruising range that can be driven for a single charge. It has been.

  The safety of the secondary battery tends to conflict with the energy density, and the safety of the secondary battery tends to decrease as the energy density increases. For example, in a secondary battery mounted on an electric vehicle having a cruising range of several hundred kilometers, the battery surface temperature when the secondary battery is damaged due to overcharging or internal short circuit exceeds several hundred degrees Celsius, It may be close.

  A secondary battery used for a power source of a vehicle or the like is generally used as an assembled battery including a plurality of single batteries (hereinafter also referred to as “cells”). For this reason, when one of the cells constituting the assembled battery is damaged and reaches the above temperature range, the adjacent battery may be damaged by the heat generation, and the damage may spread to the entire assembled battery in a chained manner. .

  By the way, an assembled battery configured by connecting a large number of single cells generates heat by a charging / discharging current. In particular, the amount of heat generated by an assembled battery used as a power supply device for a vehicle increases due to the extremely large charge / discharge current. An increase in temperature due to heat generation causes a decrease in the electrical characteristics of the battery. Further, in an assembled battery for a vehicle in which a large number of single cells are connected to increase the output voltage, it is extremely important to minimize the temperature difference between individual single cells constituting the assembled battery. This is because the temperature difference between the single cells breaks the balance of the electric characteristics of the cells, makes the remaining capacity non-uniform, and shortens the life of a specific single cell. For this reason, a power supply device for a vehicle is usually provided with a device for cooling a battery in order to reduce a temperature rise during charging and discharging. In such a cooling device, it is important to cool a large number of connected unit cells as efficiently and evenly as possible.

  For example, as described in Patent Document 1, the cooling device is usually made of a metal having good thermal conductivity. However, if the battery and the cooling device are in direct contact with each other, there is a risk of energization. Therefore, an insulating member is installed in the gap between the battery and the cooling device. Further, in order to prevent a gap between the battery and the cooling device and a decrease in cooling efficiency, a filler is also installed for the purpose of bringing the battery and the cooling device into close contact with each other.

  In Patent Document 2, the following method is proposed. A power supply device for a vehicle in which a plurality of single cells are connected includes a separator formed between the single cells and in contact with the surface of the single cells in a thermally coupled state. Further, the power supply device includes a blower mechanism that provides cooling gaps between the single cells and is fixed so as to be stacked via a separator, and forcibly blows cooling gas into the cooling gaps. Furthermore, the power supply device includes a temperature equalizing plate that is thermally coupled to the outer peripheral surface of each unit cell, and the thermal conductivity of the temperature equalizing plate is determined from the thermal conductivity of the separator provided between the unit cells. Also make it bigger.

Special table 2014-505333 gazette JP 2010-272430 A

  However, the cooling device as described in Patent Document 1 promotes the transfer of heat to adjacent batteries even when one of the cells constituting the assembled battery is damaged and reaches a high temperature. There is a risk that. That is, as a result of the cooling device promoting heat conduction to the other unit cells, the other unit cells may be damaged.

  On the other hand, in Patent Document 2, when one of the unit cells constituting the assembled battery is damaged, the amount of heat transmitted to the adjacent battery through the cooling member, the calorific value of the unit cell constituting the assembled battery, A sufficient study has not been made after quantitatively considering the influence of heat transfer by members other than the battery constituting the assembled battery. In addition, no examination has been made on the assumption that the refrigerant flow of the cooling device stops at the time of abnormality. If the refrigerant flow of the cooling device stops at the time of abnormality, the heat removal efficiency to the outside of the assembled battery by the cooling device decreases, and the contribution to heat transfer to the adjacent cells via the cooling device increases, so there is a risk of more fire spread There is. For this reason, it is extremely important to establish a measure for safety in consideration of a state where the refrigerant flow of the cooling device is stopped.

  An object of the present invention is to provide a filling member that suitably controls heat transfer between single cells via a cooling member in an assembled battery including a plurality of single cells.

  The present inventor paid attention to the amount of heat transferred between the cells via the cooling member, which has not been sufficiently studied in the above-described prior art, and conducted a detailed study on the effect. As a result, with respect to the filling member interposed between the unit cell constituting the assembled battery and the cooling member, the heat transfer resistance of the filling member is suppressed within an appropriate range, thereby causing the first abnormality. The present inventors have found that it is important to appropriately control the amount of heat transferred from the single cell to the second single cell via the cooling device, and have reached the present invention. The present invention is as follows.

[1] It has a thickness direction and a surface direction perpendicular to the thickness direction, and has a first surface and a second surface along the surface direction, and an assembled battery is configured on the first surface. A filling member that contacts a plurality of unit cells and that contacts a cooling member capable of cooling the unit cells on the second surface,
When any one of the unit cells constituting the assembled battery is a first unit cell, the heat generated from the first unit cell is transferred to the first unit via the filling member and the cooling member. The heat transfer sensitivity S of the filling member when moving to a second unit cell adjacent to the unit cell is defined by the following formula 1,
Heat transfer sensitivity S [W / K] of the filling member =
Thermal conductivity k [W / m · K] of the filling member × contact area A [m ² ] between the filling member and the first and second unit cells / thickness d [m] of the filling member (Formula 1)
The heat transfer sensitivity when the temperature of the first unit cell is equal to or higher than the temperature of the abnormal heat generation state satisfies the following formula 2.
0.5 ≦ S ≦ 4.0 (Formula 2)
The filling member characterized by the above-mentioned.

[2] The assembled battery member according to [1], wherein a thermal conductivity in a thickness direction of the filling member is 2.0 × 10 ⁻² W / m · K or more and 50.0 W / m · K or less.

[3] The assembled battery member according to [1] or [2], wherein the filling member has a thickness of 5.0 × 10 ⁻⁵ m or more and 5.0 × 10 ⁻² m or less.

  [4] An assembled battery including the filling member according to any one of [1] 1 to [3].

  The heat transfer sensitivity S of the filling member according to any one of [1] to [3] satisfies the formula (1) and suppresses the amount of heat transmitted from the first unit cell via the filling member. A method of controlling heat transfer including:

  According to the present invention, in an assembled battery including a plurality of unit cells, heat transfer between the unit cells via the cooling member can be suitably controlled.

Drawing 1 is a figure explaining the heat transfer sensitivity of a filling member while explaining composition of a filling member and a cooling member concerning an embodiment. FIG. 2 is a top view illustrating an example of the assembled battery according to the embodiment. FIG. 3 is a side view schematically showing the side surface of the assembled battery shown in FIG. 2 with the front side plate removed. FIG. 4 is a diagram illustrating an example of a unit cell. FIG. 5 is a front view of the unit cell shown in FIG. 6 is a side view of the cell shown in FIG. FIG. 7 is an explanatory diagram of the partition member. FIG. 8 is a diagram schematically showing a transmission path of heat generated inside the unit cell.

  Hereinafter, a filling member, an assembled battery, and a heat transfer control method according to an embodiment of the present invention will be described with reference to the drawings. Description of embodiment described below is an example, and this invention is not limited to the structure demonstrated by embodiment.

The filling member according to the present embodiment has a thickness direction and a surface direction orthogonal to the thickness direction, and has a first surface and a second surface along the surface direction, and the assembled battery in the first surface. Is a filling member that contacts a cooling member capable of cooling the unit cell on the second surface.
When any one of the cells constituting the assembled battery is a first cell, the heat generated from the first cell is adjacent to the first cell via the filling member and the cooling member. The heat transfer sensitivity S of the filling member when moving to the second unit cell is defined by the following formula 1,
Heat transfer sensitivity S [W / K] =
Thermal conductivity k [W / m · K] of the filling member × contact area A [m ² ] between the filling member and the first and second unit cells / thickness d [m] of the filling member (Equation 1 )
The heat transfer sensitivity S when the temperature of the first unit cell is equal to or higher than the temperature of the abnormal heat generation state satisfies the following formula 2.
0.5 ≦ S ≦ 4.0 (Formula 2)
It is characterized by that.

  Here, in the present invention, a part or all of chemical substances constituting an electrode or an electrolyte constituting a unit cell cause a decomposition reaction with heat generation inside the unit cell. A state in which the temperature rises and a part or all of the unit cell reaches 200 ° C. or higher is called “abnormal heat generation state”.

  Regarding the filling member according to the present embodiment, the heat transfer sensitivity S of the filling member when the heat generated from the first unit cell moves to the second unit cell via the filling member and the cooling member is expressed by the above equation (1). ).

  Further, in the filling member according to the present embodiment, the heat transfer sensitivity S when the temperature of the first unit cell (cell # 1) is equal to or higher than the temperature of the abnormal heat generation state (200 ° C. in the present embodiment) is expressed by the above formula. Satisfy (2).

[Heat transfer sensitivity]
FIG. 1 is a diagram for explaining the configuration of the filling member and the cooling member according to the embodiment of the present invention and explaining the heat transfer sensitivity of the filling member. The heat transfer sensitivity S of the filling member 10 will be described with reference to FIG. The heat transfer sensitivity S refers to the first single battery 200a (also referred to as cell # 1) constituting the assembled battery 100 and the second single battery 200b (also referred to as cell # 2) different from the first single battery 200a. When the heat that is in contact with the filling member 10 and is generated from the first unit cell 200a moves to the second unit cell 200b, the filling member 10, the first unit cell 200a, and the second unit cell 200b. It is a scale which shows the grade of the calorie | heat amount which moves via a contact part.

The heat transfer sensitivity S indicates the thermal conductivity (k [W / m · K]) in the thickness direction of the material used as the filling member 10, the filling member 10, the first unit cell 200a, and the second unit cell 200b. The area (A [m ² ]) of the contact portion and the thickness (d [m]) of the filling member 10 can be expressed.

  Here, the amount of heat transferred from the cell # 1 to the cell # 2 via the filling member 10 and the cooling member 400 is considered. Regarding the two surfaces in the thickness direction of the filling member 10 (two surfaces along the surface direction), the surface (upper surface) in contact with the cell # 1 and the cell # 2 is defined as a surface 10a, and the back surface (lower surface) is defined as a surface 10b. In FIG. 1, the thickness direction of the filling member 10 extends in the height direction of the paper surface of FIG. 1, and the surface direction of the filling member 10 extends in the left-right direction of the paper surface of FIG. In the example of FIG. 1, the cooling member 400 is formed in a plate shape having a flat surface that is in close contact with the surface 10 b of the filling member 10. Further, the thermal conductivity in the thickness direction of the filling member 10 is defined as k [W / m · K], and the thickness of the filling member 10 is d [m].

  Further, the average temperature of the region (referred to as region a1) where the surface 10a of the filling member 10 and the cell # 1 are in contact with each other is T1 [° C.], and the region on the surface 10b that is in plane symmetry with the region a1 (region b1). The average temperature of the region (referred to as region a2) where the surface 10a of the filling member 10 and the cell # 2 are in contact with each other is T4 [° C], and the region a2 has a plane-symmetric relationship. The average temperature of the region (region b2) is T3 [° C.].

When the average temperature T2 is lower than the average temperature T1, a surface temperature difference (T1-T2) is generated between the region a1 and the region b1 of the filling member 10. In this case, the heat flow rate (heat flux) q1 per unit cross-sectional area of the region a1 of the filling member 10 can be expressed by the following equation (3).
q1 = k (T1-T2) / d [W / m ² ] (3)

Further, when the average temperature T4 is lower than the average temperature T3, a surface temperature difference (T3-T4) is generated between the region b2 and the region a2 of the filling member 10. In this case, the heat flow rate (heat flux) q2 per unit cross-sectional area of the region b2 of the filling member 10 can be expressed by the following equation (4).
q2 = k (T3-T4) / d [W / m ² ] (4)

Here, the cooling member 400 can be comprised, for example with a metal with good heat conductivity. For this reason, when the heat removal efficiency from the cooling member 400 to the external environment is low and the environment around the cooling member 400 is close to an insulated environment, the temperature inside the cooling member 400 is considered to be substantially uniform. Can do. Under such conditions, the average temperature T2 and the average temperature T3 can be approximated to be approximately equal (T2≈T3). In this case, the heat flow rate (heat flux) q2 per unit cross-sectional area of the region b2 of the filling member 10 can be expressed by the following equation (4-2).
q2≈k (T2-T4) / d [W / m ² ] (4-2)

From the above, the heat quantity Q1 per contact area A [m ² ] moving from the cell # 1 to the cooling member 400 via the filling member 10 and the movement from the cooling member 400 to the cell # 2 via the filling member 10 The amount of heat Q2 per contact area A [m ² ] to be expressed can be expressed by the following equations (5) and (6).
Q1 = A × q1 = Ak (T1-T2) / d [W] (5)
Q2 = A * q2 = Ak (T2-T4) / d [W] (6)

The heat transfer sensitivity S of the filling member 10 passes through the contact portion of the filling member 10 when the heat transfer from one unit cell to another unit cell is in contact with the filling member 10. Therefore, it can be defined by the following formulas (7) and (8).
Q1 = S × (T1-T2) [W] (7)
Q2 = S * (T2-T4) [W] (8)

The heat transfer sensitivity S can be expressed by the following equation (9) from the equations (5), (6), (7), and (8).
S = Q1 / (T1-T2) = Q2 / (T2-T4)
= Ak / d [W / K] (9)

<Battery assembly>
An assembled battery 100 according to an embodiment of the present invention will be described. The assembled battery 100 includes, for example, an electric vehicle (EV), a hybrid electric vehicle (HEV, Hybrid Electric Vehicle), a plug-in hybrid electric vehicle (PHEV, Plug-in Hybrid Electric Vehicle), an electric heavy machine, an electric motorcycle, and an electric motorcycle. Assist bicycle, ship, aircraft, train, uninterruptible power supply (UPS), household power storage system, storage battery system for power system stabilization using renewable energy such as wind power / solar power / tidal power / geothermal power It is applied to battery packs mounted on However, the assembled battery 100 can also be used as a power source that supplies power to devices other than the EV described above.

  2 shows a top view of an example of an assembled battery 100 formed using a plurality of unit cells 200, and FIG. 3 schematically shows a state in which the side plate 300d is removed from the assembled battery 100 shown in FIG. It is a side view.

[Single cell]
4 is a diagram showing an example of the unit cell 200 constituting the assembled battery 100, FIG. 5 is a front view of the unit cell 200 shown in FIG. 4, and FIG. 6 is a right side view of the unit cell 200. . In the example shown in FIGS. 4, 5, and 6, the unit cell 200 is formed in a rectangular parallelepiped shape having a height direction (H), a width direction (W), and a thickness direction (D). 210 and a terminal 220 are provided. The unit cell 200 is, for example, a lithium ion secondary battery including a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. In addition to the lithium ion secondary battery, a secondary battery such as a lithium ion all solid battery, a nickel metal hydride battery, a nickel cadmium battery, or a lead storage battery can be applied.

[Battery]
2 and 3, the assembled battery 100 includes a housing 300 and a plurality of unit cells 200 accommodated in the housing 300. The plurality of unit cells 200 are arranged in a line in the thickness direction “D” (left and right direction in FIG. 2), and the partition member 1 is interposed between the unit cells 200. The housing 300 includes side plates 300a and 3 provided so as to surround the sides of the plurality of unit cells 200 arranged.
00b, 300c and 300d. Pressure is applied to the side plate 300a and the side plate 300b using a jig (not shown) so that the distance between the side plate 300a and the side plate 300b is reduced. Pressure) is maintained. 2 and 3 exemplify five unit cells 200 as an example, the number of unit cells can be selected as appropriate. 2 and 3 show an example in which the assembled battery 100 is arranged so that the terminal 210 and the terminal 220 face upward. In the assembled battery 100, the terminal 210 and the terminal 220 face sideways. May be arranged as follows.

  As described above, the plurality of single cells 200 are arranged in the thickness direction in the housing 300, and the partition member 1 is disposed between the single cells 200. A positive electrode terminal (for example, terminal 210) and a negative electrode terminal (for example, terminal 220) of the unit cells 200 that are adjacent (opposed) via the partition member 1 are electrically connected in series by the bus bar 301. Thereby, the assembled battery 100 outputs power of a predetermined voltage.

(Partition member)
As shown in FIG. 7, the partition member 1 has a parallel plate shape having a height direction (H), a width direction (W), and a thickness direction (D), or an overall shape of a sheet. The partition member 1 is used to partition between the unit cells 200 constituting the assembled battery 100 or between the unit cell 200 and a member other than the unit cell 200 in the thickness direction (D). The partition member 1 can be comprised with the heat insulating material 110 grade | etc.,. The thickness of the partition member 1 is usually in the range of L / 50 mm or more and L / 10 mm or less, preferably L / 30 mm or more and L / 15 mm or less when the thickness of the unit cell 200 is L [mm]. Range.

[Insulation]
The heat insulating material 110 is formed of a porous material or the like. Examples of the porous body include those formed from fibrous materials (also referred to as fibrous inorganic materials) and particles (also referred to as powdered inorganic materials). The heat insulating material 110 can be formed, for example, using a predetermined molding technique such as pressing and solidifying fibers and particles.

  The fibrous material (fibrous inorganic substance) is selected from the group consisting of paper, cotton sheet, polyimide fiber, aramid fiber, polytetrafluoroethylene (PTFE) fiber, glass fiber, rock wool, ceramic fiber, and biosoluble inorganic fiber, for example. And at least one selected from glass fiber, rock wool, ceramic fiber and biosoluble inorganic fiber is particularly preferable. The ceramic fiber is a fiber mainly composed of silica and alumina (silica: alumina = 40: 60 to 0: 100), and specifically, silica / alumina fiber, mullite fiber, and alumina fiber can be used.

  Further, the particles (powdered inorganic substance) are, for example, at least one selected from the group consisting of silica particles, alumina particles, calcium silicate, clay mineral, vermiculite, mica, cement, pearlite, fumed silica, and airgel. Among these, at least one selected from silica particles, alumina particles, calcium silicate and vermiculite is particularly preferable. The clay minerals are mainly magnesium silicate (including talc and sepiolite), montmorillonite and kaolinite.

[Filling member and cooling member]
As shown in FIG. 3, a cooling member (also referred to as a cooling device) 400 is disposed at the bottom of the housing 300. The bottom surfaces of the plurality of unit cells 200 are in contact with the upper surface (surface 10a: corresponding to the first surface) of the parallel plate-shaped filling member 10, and the lower surface (surface 10b: equivalent to the second surface) of the filling member 10. ) Is in contact with the cooling member 400. Heat from each unit cell 200 can be transmitted to the cooling member 400 via the filling member 10.

  The cooling member 400 is, for example, a heat sink. The cooling member 400 may or may not move (circulate) the fluid (refrigerant) within the cooling member 400. The filling member 10 is formed of, for example, one or more kinds of materials, for example, one or more kinds of plastics, plastic compounds, plastic / metal composite materials, or the like alone or in an appropriate combination.

  FIG. 8 schematically shows a transmission path of heat generated inside the unit cell 200. Heat generated inside the unit cell 200 is transmitted to other unit cells 200 through various transmission paths. In the example of FIG. 8, a heat transfer path from the single battery 200a (cell # 1), which is one of the plurality of single batteries 200, is schematically shown. For example, the heat generated in the cell # 1 can be transmitted to the other unit cell 200b (cell # 2) via the partition member 1. In addition, heat from each of the unit cells 200 is radiated to the outside through the bus bar 301. Further, heat from each of the unit cells 200 is transmitted to the cooling member 400 via the filling member 10 and can be radiated from the cooling member 400 to the outside.

<Heat generation and heat transfer in battery pack>
Here, heat generation and heat transfer in the assembled battery 100 will be described. A part or all of the chemical substances constituting the electrodes, electrolyte, and the like constituting the unit cell 200 cause a decomposition reaction with heat generation inside the unit cell 200, thereby increasing the temperature of the unit cell 200, and the unit cell 200. Some or all of 200 may be 200 ° C. or higher. That is, the unit cell 200 may be in an abnormal heat generation state.

In general, it is known that the stability of the crystal structure after delithiation by charging greatly affects the safety of the positive electrode material among the materials constituting the unit cell 200. Materials such as LiCoO ₂ , Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ , Li (Ni _0.8 Co _0.15 Al _0.05 ) O _{2 that} are generally used as positive electrode materials are charged. In the state, crystal collapse accompanied with oxygen release occurs at high temperature. Oxygen released from the positive electrode causes oxidation of the electrolytic solution and is accompanied by a rapid exothermic reaction. According to structural analysis using synchrotron radiation, it has been reported that a crystal phase transition occurs at around 200 ° C. in the positive electrode material type. For this reason, when a part or all of the unit cell 200 reaches 200 ° C. or higher, it means that the crystal collapse of the positive electrode is progressing, that is, the unit cell 200 is in a thermal runaway state (Reference 1: Lithium). High Safety Technology and Materials for Ion Batteries CMC Publishing, P. 44 / Reference 2: J. Dahn et al., Electrochemistry Communication, 9, 2534-2540 (2007) / Reference 3: Hironori Kobayashi Evaluation and analysis technology of positive electrode material for lithium ion secondary battery used ”Spring-8 Utilization Promotion Council Glass and Ceramics Study Group (2nd) (2011)).

In addition, regarding the safety of the negative electrode material among the materials constituting the unit cell 200, the charged negative electrode (lithium-inserted carbon negative electrode) basically exhibits a strong reducibility similar to that of lithium metal, and reacts with the electrolytic solution on the negative electrode surface. It is known that a film is formed on the surface, thereby suppressing further reaction. Therefore, the chemical composition, structure, and thermal stability of the protective coating greatly affect the thermal stability of the charging negative electrode when the temperature rises. Usually, the reaction between the charging negative electrode and the electrolytic solution is explained by the formation of a protective coating followed by an explosive reductive decomposition reaction by destruction of the coating. In general, it has been reported that the protective film formation reaction on the negative electrode proceeds from around 130 ° C., and the subsequent film decomposition reaction proceeds at around 200 ° C., eventually leading to an explosive reductive decomposition reaction. Therefore, when a part or all of the unit cell 200 is 200 ° C. or more, it means that the coating film destruction on the negative electrode surface has progressed, that is, the unit cell 200 is in a thermal runaway state (Reference Document 4: Battery Handbook 1st Edition Ohm Co., P.591 / Reference 5: Frontier of High Safety Technology and Evaluation Technology for Lithium Ion Batteries CMC Publishing, P.90).

  Further, in the present invention, a state in which a chemical substance that constitutes an electrode, an electrolytic solution, or the like that constitutes the unit cell 200 does not cause a decomposition reaction with a certain rate of heat generation within the unit cell 200 is referred to as a “normal state”. . Here, the heat generation state of the unit cell 200 is evaluated using ARC (Accelerating rate calibration), which is a means for quantitatively measuring the thermal behavior when the reactive chemical substance undergoes self-exothermic decomposition under adiabatic conditions. Can do. For example, Dahn et al. Define that a self-heating reaction proceeds inside the cell when the exothermic rate observed in ARC exceeds 0.04 ° C./min, and this can be imitated (reference). Reference 6: J. Dahn et al., Electrochimica Acta, 49, 4599-4604 (2004)).

Further, in the present invention, the unit cell 200 in the normal state is referred to as “unit cell that maintains the normal state”, and the unit cell 200 that deviates from the normal state and does not reach the abnormal heat generation state is referred to as “unit cell that deviates from the normal state”. " The upper limit of the surface average temperature assumed when the unit cell 200 does not deviate from the normal state is usually 80 ° C. Here, the boiling point of the general-purpose electrolyte component is 90 ° C. or higher as shown in Table 1 below. General-purpose electrolyte components are, for example, ethylene carbonate (EC), diethyl carbonate, dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). When the surface average temperature of the unit cell 200 is lower than 80 ° C., the general-purpose electrolytic solution itself constituting the unit cell 200 does not boil.

  For example, the upper limit value of the surface average temperature assumed when the unit cell 200 in contact with the partition member 1 deviates from the normal state and does not reach the abnormal heat generation state is 180 ° C. Here, it is assumed that the material of the partition member 1 is made of polyethylene or polypropylene which is a general-purpose separator material. In this case, the meltdown temperature is known to be 160-200 ° C. For this reason, when the surface average temperature of the unit cell 200 exceeds 180 ° C., a part of the general-purpose separator material constituting the unit cell 200 may melt down and an abnormal heat generation state may occur.

<Cooling of cells with abnormal heat generation>
In the assembled battery 100 according to the present embodiment, when one unit cell 200 (for example, the unit cell 200a (cell # 1)) of the plurality of unit cells 200 is in an abnormal heat generation state, the battery is emitted from the cell # 1. Part of the heat is transferred to the cooling member 400 via the filling member 10.

  In addition, a part of the heat transferred to the filling member 10 is transmitted to the single cells 200 other than the single cells 200 in an abnormal heat generation state via the filling member 10 and the cooling member 400. The unit cells 200 other than the unit cells 200 that are in an abnormal heat generation state are, for example, the unit cells 200 that are opposed to the unit cell 200 in an abnormal heat generation state via the partition member 1 (adjacent to each other with the partition member 1 in between). is there. For example, in the example shown in FIG. 8, when a single battery 200 a (cell # 1) that is one of the single batteries 200 is in an abnormal heat generation state, part of the heat from the cell # 1 is filled with the filling member 10 It is transmitted to the single battery 200b (cell # 2) via the cooling member 400.

[Filling material]
For this reason, the filling member 10 which concerns on embodiment is equipped with the structure shown in FIG. 1 as an example. In this embodiment, the filling member 10 is formed in a parallel plate shape, the thickness direction thereof is arranged in the height direction (H) of the partition member 1, and the surface direction of the filling member 10 is the thickness direction of the partition member 1. (D). The filling member 10 has a surface 10a corresponding to the first surface and a surface 10b corresponding to the second surface along the surface direction. The filling member 10 is in contact with the first and second unit cells 200a and 200b constituting the assembled battery 100 on the surface 10a. Moreover, the filling member 10 contacts the cooling member 400 that can cool the first and second unit cells 200a and 200b on the surface 10b.

<Example>
Next, specific embodiments of the filling member according to the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

  In Examples 1 to 5 and Comparative Examples 1 and 2 described below, heat transfer from the unit cell 200 (referred to as the unit cell 200a) in an abnormal heat generation state to another unit cell 200 (referred to as the unit cell 200b). Paying attention to the amount of heat transfer through the filling member 10 disposed between the unit cell 200a and the cooling member 400 in the path, the amount of heat transfer between the unit cell 200a and the unit cell 200b by the filling member 10 can be suppressed. The sex was examined.

As an assembled battery 100 to be evaluated, an assembled battery model in which five single cells 200 (cell # 1 to cell # 5) as shown in FIG. 8 are connected is constructed, and the cell # 1 generates heat corresponding to an abnormal heat generation state. An amount of 1.4 × 10 ⁹ [J / m ³ ] (total calorific value estimated from the calorific value evaluation of the cell # 2 using the NMC positive electrode) was given, and the following Examples 1 to 5 and Comparative Examples 1 and 2 In this condition, the temperature transition of the cell # 2 adjacent to the cell # 1 is estimated by solving the heat conduction equation by the finite element method, and the amount of heat transfer between the cells due to the change of the heat transfer sensitivity of the filling member 10 is reduced. The effect was evaluated. Here, for analysis, COMSOL Multiphysics, which is general-purpose physical simulation software manufactured by COMSOL AB, was used, and analysis was performed with reference to the following references 9 and 10. In addition, about the heat transfer path | route between cell # 1 and cell # 2, the path | route demonstrated in FIG. 8 is assumed (reference literature 9: Unexamined-Japanese-Patent No. 2006-010648, reference literature 10: RM. Spotnitz et al., J. Power Sources 163, 1080-1086 ((2007)).

Table 2 below shows the results of Examples 1 to 5 and Comparative Examples 1 and 2.

  In Examples 1 to 5 and Comparative Examples 1 and 2, the sizes of the cells # 1 to # 5 were PHEV2 sizes (91 mm long, 148 mm wide, 26.5 mm thick) defined by the German Automobile Manufacturers Association. . For simplicity, the cooling member 400 is assumed to be a plate-like material having a thickness of about 4 mm made of metal such as aluminum or aluminum alloy, and the thermal conductivity is 200 W / m · K. The filling member 10 installed between the cells # 1 and # 2 and the cooling member 400 was assumed to be a coating film such as an insulating paint or a plastic film. Regarding the filling member 10, the heat transfer resistance can be changed by the film thickness, the type and filling amount of the filler (stuffing into the filling member 10), or the type of plastic forming the structure of the filling member 10. The bus bar 301 was assumed to be made of aluminum, and the thermal conductivity was 237 W / m · K. Moreover, the partition member 1 installed between the cell # 1 and the cell # 2 is assumed to be a heat insulating material, the film thickness (dimension in the thickness direction) is 1 mm, and the thermal conductivity is 0.1 W / m · K. Further, regarding the cooling member 400, assuming that the refrigerant flow stopped, a heat transfer coefficient equivalent to natural convection was given to the environment around the cooling member 400. Under these conditions, the temperature transition in the cell # 2 was estimated for 300 seconds after the abnormality occurred in the cell # 1 and the abnormal heat generation state was reached.

  In Examples 1 to 5 and Comparative Examples 1 and 2, in order to clarify the degree of temperature rise caused by the heat transferred from the single battery 200 that reached the temperature of the abnormal heat generation state, other than the cell # 1 Regarding cell # 2 to cell # 5, temperature rise due to self-heating of the cells is not taken into consideration.

(Comparative Example 1)
A material having a thermal conductivity of 2.0 W / m · K was used for the filling member 10, and the film thickness was 1 mm. It was estimated that the maximum temperature inside the cell # 2 reached 212.4 ° C. 152 seconds after the abnormality occurred in the cell # 1. In this case, the heat transfer sensitivity S of the filling member 10 was 7.84 W / K.

Example 1
A material having a thermal conductivity of 1.0 W / m · K was used for the filling member 10 and the film thickness was 1 mm. It was estimated that the maximum temperature inside the cell # 2 reached 208.7 ° C. 168 seconds after the abnormality occurred in the cell # 1. In this case, the heat transfer sensitivity S of the filling member 10 was 3.92 W / K.

(Example 2)
A material having a thermal conductivity of 0.8 W / m · K was used for the filling member 10, and the film thickness was 1 mm. It was estimated that the maximum temperature inside the cell # 2 reached 207.9 ° C. 168 seconds after the abnormality occurred in the cell # 1. In this case, the heat transfer sensitivity S of the filling member 10 was 3.13 W / K.

(Example 3)
A material having a thermal conductivity of 0.6 W / m · K was used for the filling member 10, and the film thickness was 1 mm. It was estimated that the maximum temperature inside the cell # 2 reached 207.1 ° C. 175 seconds after the abnormality occurred in the cell # 1. In this case, the heat transfer sensitivity Sb of the filling member 10 was 2.35 W / K.

Example 4
A material having a thermal conductivity of 0.4 W / m · K was used for the filling member 10 and the film thickness was 1 mm. It was estimated that the maximum temperature inside the cell # 2 reached 207.3 ° C. 188 seconds after the abnormality occurred in the cell # 1. In this case, the heat transfer sensitivity S of the filling member 10 was 1.57 W / K.

(Example 5)
A material having a thermal conductivity of 0.2 W / m · K was used for the filling member 10, and the film thickness was 1 mm. It was estimated that the maximum temperature inside the cell # 2 reached 208.1 ° C. 179 seconds after the abnormality occurred in the cell # 1. In this case, the heat transfer sensitivity S of the filling member 10 was 0.78 W / K.

(Comparative Example 2)
A material having a thermal conductivity of 0.1 W / m · K was used for the filling member 10, and the film thickness was 1 mm. It was estimated that the maximum temperature inside the cell # 2 reached 211.0 ° C. 208 seconds after the abnormality occurred in the cell # 1. In this case, the heat transfer sensitivity S of the filling member 10 was 0.39 W / K.

  From the results of Examples 1 to 5 and Comparative Examples 1 and 2, the following can be understood. About the filling member 10 installed between the unit cell 200 constituting the assembled battery 100 and the cooling member 400 provided for cooling and equalizing the battery temperature, the heat transfer resistance (thermal conductivity k) of the filling member 10 ) Within an appropriate range, the temperature rise of the cell # 2 (second unit cell) due to the amount of heat transferred through the cooling member 400 from the cell # 1 (first unit cell) in which an abnormality has occurred That is, according to Examples 1 to 5 and Comparative Examples 1 and 2, it was shown that there is a possibility that the heat transfer between the single cells 200 via the cooling member 400 may be suitably controlled. . In Examples 1 to 5, the maximum temperature of the cell # 2 can be set to a value lower than 210 ° C, whereas in Comparative Examples 1 and 2, the maximum temperature exceeded 210 ° C. From these, the range (0.5 ≦ S ≦ 4.0) of the formula (2) could be obtained as the heat transfer sensitivity S capable of suitably suppressing the temperature of the cell # 2. From the results of Examples 1 to 5, it can be said that the heat transfer sensitivity S is preferably 0.7 or more and 3.2 or less, and more preferably 1.5 or more and 2.4 or less.

Here, in Examples 1 to 5 and Comparative Examples 1 and 2, the thickness (film thickness) of the filling member 10 was fixed to 1 mm, but the thickness of the filling member 10 was 5.0 × 10 ⁻⁵ m or more. It may be 0 × 10 ⁻² m or less. For this reason, from the results of Examples 1 to 5 and Comparative Examples 1 and 2, the thermal conductivity k in the thickness direction of the filling member 10 is 2.0 × 10 ⁻² W / m · K or more and 50.0 W / m · K. It was found that the following is preferable.

DESCRIPTION OF SYMBOLS 1 Partition member 10 Filling member 10a, 10b Surface 100 Battery assembly 110 Heat insulating material 200 Single battery 300 Case 400 Cooling member

Claims (5)

A plurality of single units that have a thickness direction and a surface direction orthogonal to the thickness direction, and that have a first surface and a second surface along the surface direction, and that form an assembled battery on the first surface. A filling member that contacts a battery and contacts a cooling member capable of cooling the unit cell on the second surface;
When any one of the unit cells constituting the assembled battery is a first unit cell, the heat generated from the first unit cell is transferred to the first unit via the filling member and the cooling member. The heat transfer sensitivity S of the filling member when moving to a second unit cell adjacent to the unit cell is defined by the following formula 1,
Heat transfer sensitivity S [W / K] of the filling member =
Thermal conductivity k [W / m · K] of the filling member × contact area A [m ² ] between the filling member and the first and second unit cells / thickness d [m] of the filling member (Formula 1)
The heat transfer sensitivity when the temperature of the first unit cell is equal to or higher than the temperature of the abnormal heat generation state satisfies the following formula 2.
0.5 ≦ S ≦ 4.0 (Formula 2)
The filling member characterized by the above-mentioned. The filling member according to claim 1, wherein the filling member has a thermal conductivity in the thickness direction of 2.0 × 10 ⁻² W / m · K or more and 50.0 W / m · K or less. The filling member according to claim 1 or 2, wherein a thickness of the filling member is 5.0 x ^10-5 m or more and 5.0 x ^10-2 m or less.   The assembled battery containing the filling member of any one of Claim 1 to 3. The heat transfer including the heat transfer sensitivity S of the filling member according to any one of claims 1 to 3 satisfying the formula 1 and suppressing the amount of heat transferred from the first unit cell through the filling member. Control method.

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