KR102263457B1 - Battery Cell of Improved Cooling Efficiency - Google Patents

Abstract

According to the present invention, an electrode assembly having a positive electrode/separator/negative electrode structure is mounted inside a battery case made of a laminate sheet, and at least one first heat dissipation member for dissipating heat generated inside the electrode assembly when charging/discharging or short circuit occurs. mounted in contact with at least one of an inner surface of the electrode assembly and an outer surface of the electrode assembly;
a second heat dissipation member is positioned outside the battery case;
The first heat dissipating member and the second heat dissipating member are thermally connected by one or more connecting members extending from one end of the first heat dissipating member to the outside of the battery case. do.

Description

Battery Cell of Improved Cooling Efficiency}

The present invention relates to a battery cell with improved cooling efficiency, and in particular, a first heat dissipation member located inside the battery case and a second heat dissipation member located outside the battery case are thermally connected by a connecting member. It relates to a battery cell with significantly improved cooling efficiency.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, lithium secondary batteries exhibiting high energy density and operating potential, long cycle life, and low self-discharge rate. has been commercialized and widely used.

In addition, as interest in environmental issues grows, research on electric vehicles and hybrid electric vehicles that can replace vehicles using fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, is being conducted. . Although nickel-metal hydride secondary batteries are mainly used as power sources for such electric vehicles and hybrid electric vehicles, research using lithium secondary batteries with high energy density and discharge voltage is being actively conducted, and some are in the commercialization stage.

While one or two or three battery cells are used per device in small mobile devices, medium-to-large battery modules electrically connecting a plurality of battery cells are used in mid-to-large devices such as automobiles due to the need for high output and large capacity.

These battery cells are composed of secondary batteries capable of charging and discharging, and during the charging and discharging process, the battery temperature rises due to heat generated by the internal resistance of the battery. In particular, since the heat of exothermic reaction inside the battery is added during discharging, the degree of heat generation is greater, and the temperature rises accordingly. When the temperature of the battery rises, the lifespan characteristics of the battery deteriorate and problems such as gas generation due to side reactions occur, so cooling the battery acts as an important factor.

Furthermore, since the laminate sheet of the pouch-type battery, which is widely used recently, is coated with a polymer material having low thermal conductivity, it is difficult to effectively cool the temperature of the entire battery cell.

In particular, as in the case of an electric vehicle, when a large current is used to generate a high output, the heat of the battery is greater, and if the heat of the battery module generated during the charging and discharging process is not effectively removed, heat accumulation occurs, as a result, the battery It accelerates the deterioration of the module, and in some cases may cause fire or explosion. Accordingly, the battery pack, which is a high-output, large-capacity battery, requires a cooling system for cooling the battery cells contained therein.

In addition, in order to increase the capacity of the battery and lower the price in recent years, the capacity of the individual battery is increasing, and accordingly, the problem of heat generation of the battery is also serious.

In addition, when an internal short circuit occurs due to penetration of the needle-shaped conductor, etc., the temperature rise cannot be uniformly suppressed, and the strength of the battery against external impact is also low, so there is a limit in terms of securing the safety of the battery.

In order to solve the above problems, an inefficient direct air cooling method, an indirect air cooling method using a heat sink that improves efficiency but is expensive, and a water cooling method in which a water channel is made in the heat sink and cooled by flowing cooling water has been used.

However, in the method that relies on external cooling of the battery cell, when the thickness of the battery is increased, the temperature of the entire battery cell is lowered because the temperature increased from the center of the battery cell is not easily transferred to the heat sink outside the battery cell. It cannot be cooled uniformly.

Accordingly, a heat transfer method by conduction has been developed in the form of mounting a heat sink inside the battery and taking it out of the battery, but this also does not achieve sufficient cooling to a desired degree, and the thicker the battery cell, the greater the number of battery cells. As the number increases, there is a problem that the cooling effect is significantly lowered compared to the heat emitted from the battery cells.

Accordingly, there is a high need for a battery cell with improved safety by enabling more efficient cooling during internal short circuits caused by heat generated during charging and discharging, external shocks, penetration of needle-shaped conductors, and the like.

An object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After the inventors of the present application repeated various experiments and in-depth research, the first heat dissipation member is mounted in contact with at least one of the inside of the electrode assembly and the outer surface of the electrode assembly, and the second heat dissipation member is the outside of the battery case. When thermally connecting them with a connecting member, which is a heat-conducting material, heat generated in the charging/discharging process, external shock, or internal short-circuit due to needle-shaped conductor penetration, etc., effectively dissipates heat generated inside the electrode assembly to the outside Since the cooling effect is excellent even when the thickness of the battery cells and the number of battery cells are increased, it was confirmed that it is easy to secure battery safety, and the present invention was reached.

In the battery cell according to the present invention for achieving this object, an electrode assembly having a positive electrode/separator/negative electrode structure is mounted inside a battery case made of a laminate sheet, and heat generated inside the electrode assembly when charging/discharging or short circuit occurs one or more first heat dissipating members for dissipating heat are mounted in contact with at least one of an inner surface of the electrode assembly and an outer surface of the electrode assembly;

a second heat dissipation member is positioned outside the battery case;

The first heat dissipating member and the second heat dissipating member are thermally connected by one or more connecting members extending from one end of the first heat dissipating member to the outside of the battery case.

As described above, direct heat conduction from the inside of the battery to the outside is possible only by including the heat dissipation member inside the battery cell, but there is a limit to thermal cooling from the outside, and even if the heat dissipation member is exposed to the outside, the Since the exposed portion is extremely small, cooling from the outside is inefficient, and the thicker the battery cell, the more inefficient the battery cell is.

On the other hand, the battery cell of the present invention has a first heat dissipation member located inside the battery cell, specifically, in direct contact with the inside of the electrode assembly and the outer surface of the electrode assembly, and the first heat dissipation member and the connecting member thermally by the connecting member. By including the second heat dissipating member connected and located outside the battery cell, heat conducted from the first heat dissipating member can be efficiently cooled from the outside by the second heat dissipating member, and heat generation according to charging and discharging and the acicular conductor When an internal short circuit occurs due to penetration, it is possible to significantly improve the stability of the battery by suppressing the temperature rise as much as possible.

Accordingly, the first heat dissipation member, the second heat dissipation member, and the connecting member for maximizing the cooling effect may be formed of a thermally conductive material, specifically, a metal material.

The metal material is not limited as long as it is a metal, but may be, in detail, aluminum or copper so as not to be greatly burdened in terms of cost while exhibiting excellent thermal conductivity.

On the other hand, while maximizing the cooling effect, it is undesirable to increase the volume of the battery cell by the first heat dissipating member and the second heat dissipating member. In order to minimize the increase in volume, the first heat dissipating member and the second heat dissipating member 2 The heat dissipation member may have a plate-like structure, and at this time, there is a limit to increasing the thickness in order to maximize the effect of the heat dissipation member. To solve the safety problem, their size may be the same as that of the anode or cathode.

Specifically, the thickness of the heat dissipation members may be about 0.1 to 10% of the total thickness of the electrode assembly, and specifically 1 to 10%. If it is too thin out of the above range, it may be damaged due to weak rigidity, and it is not preferable that a short circuit with the electrodes may occur due to the breakage. If it is too thick, it is not preferable because the volume of the battery cell itself is greatly increased. .

In addition, the size of the heat dissipation members may be 50% or more of the minimum size of the positive or negative electrode, and when it is too small, it is not preferable because it is difficult to easily transfer the heat of the battery cells.

When the first heat dissipation member is located inside the electrode assembly, the position is not limited, but may be interposed between the positive electrode and the separator or between the negative electrode and the separator, and the positive electrode, the separator, and the negative electrode are two or more In an embodiment, in order to maximize cooling efficiency in the thickness direction, the first heat dissipation member may be interposed between the central anode and the separator or between the cathode and the separator.

In addition, when the first heat dissipation member is located on the outer surface of the electrode assembly, the outer surface of the electrode assembly may be the most effective for heat dissipation, specifically, the outer surface meeting the electrodes in the stacking direction.

In addition, the first heat dissipation member is thermally connected to the second heat dissipation member located outside the battery case by a connecting member. In this case, the connecting member may be attached to the heat dissipation members by welding, and the connecting member One end of the first heat dissipation member on which the member is formed may be a side on which the electrode tab is not formed.

When positioned in the same direction as the electrode tab, there is a high possibility that a short circuit may occur even with a slight vibration between the electrode tab and the electrode tab, and there is a limit to adjusting the size of the electrode tab and the connecting member. It is more preferable for the connecting member to be located.

One or more connecting members extending from the first heat dissipation member may be formed, and since the heat dissipation members inside and outside the battery case must be connected, between the upper and lower cases of the battery case, the battery case is an electrode The assembly may be heat-sealed in a state interposed around the outer periphery of the receiving unit in which the assembly is accommodated.

In this case, an insulating tape may be attached to one or both surfaces of the connecting member that meets the heat-sealed portion of the battery case.

In addition, the structure of the connecting member is not limited, but as described above, since it should be interposed on the outer periphery of the battery case, in detail, it may be a plate-shaped structure smaller than that of the first heat dissipation member and the second heat dissipation member.

Specifically, the width of the connecting member may be 10 to 50% of the length of the battery cell based on the length direction of the battery cell, specifically, may be 15 to 30%.

If the width of the connecting member is too large, bending for forming a battery cell structure to be described later is not easy, and if it is too small, it is not preferable because it is cut even with a small impact and heat transfer is not easy.

More specifically, in order to secure both the ease of bending and heat transfer, it is more preferable that the connecting member is made of two or more, and the width of one connecting member satisfies the range of 10 to 30%.

In another specific example, the connecting member may have a bendable structure as described above.

Therefore, by bending the connecting member, the second heat dissipation member can be positioned in the thickness direction of the battery cell, that is, in the direction in which the electrodes are stacked, from the outside of the battery case, and more specifically, in the battery cell thickness direction. You may be interviewed on the outside. Accordingly, there may be a cooling effect not only from the inside of the battery cell but also from the outside, and heat conducted through the connecting member from the inside may be cooled through the second heat dissipating member outside, so that more efficient cooling is possible.

On the other hand, the electrode assembly mounted inside the battery case is not particularly limited as long as it has a structure consisting of a positive electrode and a negative electrode and a separator interposed therebetween by connecting a plurality of electrode tabs, preferably a winding type (jelly-roll). ), a stacked or stacked/folded structure. Detailed information on the electrode assembly of the stack/folding structure is disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059, and 2001-0082060 of the present applicant, and the application is in the context of the present invention. incorporated by reference.

In the case of the jelly-roll, specifically, it may have a structure in which a heat dissipation member is mounted in the center of its winding, or a structure attached to the outer surface of the jelly-roll. The mounting of the heat dissipation member to the winding center may be introduced during the winding process, or after winding by the mandrel, the mandrel may be removed and then the heat dissipation member may be inserted instead.

The present invention also provides a battery module including two or more of the battery cells.

When the battery module composed of the battery cells includes n (3≤n≤50) battery cells, the second heat dissipation member of the first to n-1th battery cells is bent of the connecting member. A structure in which the second heat dissipation member of the n-th battery cell positioned at the outermost side of the battery cell is positioned in the thickness direction of the battery cell from the outside of the battery case and interposed between the adjacent battery cells, and is positioned on the outer surface of the battery cell In the case of having such a structure, cooling by heat conduction is possible from both sides of the first heat dissipation member inside and the second heat dissipation member outside while being compact, and the battery cells located inside the arrangement of the battery modules are heat dissipating members. Since the bar may be included on both sides, the cooling efficiency may be further improved.

Furthermore, the battery module may further include a heat exchange member, and in this case, the bent connecting member may be in thermal contact with the heat exchange member. The combination of the heat dissipating member and the heat exchanging member enables efficient heat transfer, and the contact method may be variously performed by welding, mechanical fastening, or the like.

Here, the structure of the heat exchange member is not particularly limited, and specifically, it may be an air cooling type, but may have a structure in which one or two or more flow paths for the flow of the refrigerant are formed. For example, by forming a refrigerant flow path for the flow of a liquid refrigerant such as water in the heat exchange member, it is possible to exhibit an excellent cooling effect with high reliability compared to a conventional air-cooling structure.

Therefore, the heat transferred to the first heat dissipating member and the second heat dissipating member from inside and outside the battery cell comes into contact with the heat exchange member through the connecting member, and the heat exchange member can additionally dissipate heat by water cooling or air cooling through the refrigerant passage. By doing so, the heat dissipation of the battery cell can be effectively performed.

In addition, the present invention provides a battery pack manufactured by combining one or more battery modules according to a desired output and capacity, and a device including the battery pack.

The device according to the present invention includes a plurality of battery packs in order to achieve high output and high capacity, so that electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, or electric power that are seriously emerging in terms of safety of high heat generated during charging and discharging It can be preferably used for power sources such as storage devices.

In particular, in the case of electric vehicles and plug-in hybrid electric vehicles that require high output through the battery pack over a long period of time, high heat dissipation characteristics are required. It can be used more preferably in a hybrid electric vehicle.

Since the structure and manufacturing method of the battery module, battery pack, and device described above are known in the art using battery cells, detailed description thereof will be omitted herein.

As described above, in the battery cell according to the present invention, the heat dissipation member for facilitating heat dissipation of the battery is exposed to the outside of the electrode assembly while in contact with the inside of the electrode assembly and/or the outer surface of the electrode assembly. The generated heat can be effectively dissipated to the outside, thereby improving the lifespan characteristics of the battery.

Furthermore, in the battery module, the heat dissipation member protruding to the outside of the battery cell is interposed between the battery cell and the adjacent battery cell to increase the cooling efficiency, and the connecting member connecting the heat dissipation members is in contact with the additional heat exchange member, so that the structure is simple. cooling efficiency can be maximized, and the safety of the battery module or battery pack can be further improved.

1 is a cross-sectional view of a battery cell according to an embodiment of the present invention;
2 is a plan view of a battery cell according to an embodiment of the present invention;
3 is a front view in which a plurality of battery cells are arranged for a battery module according to an embodiment of the present invention;
4 is a perspective view of a battery module structure according to an embodiment of the present invention.

Hereinafter, the present invention will be further described in detail with reference to the drawings according to embodiments of the present invention, but the scope of the present invention is not limited thereto.

1 is a cross-sectional view schematically showing the inside of a battery cell according to an embodiment of the present invention.

Referring to FIG. 1 , in the battery cell 100 , the electrode assembly 110 of the positive electrode 111 / separator 112 / negative electrode 112 structure is mounted inside the battery case 120 of a laminate sheet, and these electrodes A first heat dissipating member 131 for dissipating heat generated inside the electrode assembly is mounted inside the assembly, specifically, between the separator and the negative electrode, and a second heat dissipating member is positioned outside the battery case.

Meanwhile, in FIG. 2, in order to further clarify the connection relationship between the first heat dissipation member 131 and the second heat dissipation member 132, a plan view of the battery cell is shown in perspective view except for other components of the electrode assembly such as the positive electrode and the negative electrode. .

Referring to FIG. 2 , the first heat dissipation member 131 and the second heat dissipation member 132 of the battery cell 100 extend to the outside of the battery case 120 from one end of the first heat dissipation member 131 . It is connected by two connecting members 133 , and in this case, the one end means a side on which the electrode tabs 114 extending outward from the electrode assembly are not formed.

In addition, referring to FIGS. 1 and 2 together, the first heat dissipation member 131 and the second heat dissipation member 132 have a plate-shaped structure of a similar size to the anode 111 and the cathode 112 of the electrode assembly, The connecting member 133 has a plate-shaped structure smaller than the first heat dissipation member 131 and the second heat dissipation member 132 .

The connecting member 133 is provided outside the battery case 120 to connect the first heat dissipation member 131 located inside the battery case 120 and the second heat dissipation member 132 located outside the battery case 120 . It has to be located in the fusion part formed around it, and therefore, although not clearly shown, the connecting member 133 is thermally fused together in a state interposed at the outer periphery of the battery case 120 , and at this time, insulation is secured In order to do this, an insulating tape 134 is attached to one or both sides of the connecting member 133 where the heat-sealed portion of the battery case 120 meets, like the insulating tape 115 attached to the electrode tabs 114 .

The connecting member 133 is also bendable (indicated by an arrow), so that the second heat dissipation member 132 is positioned in the thickness direction of the battery cell from the outside of the battery case.

In order to show one specific example and the effect according to which the connecting member 133 is bendable, a battery module having a structure in which the battery cells 100, 200, 300, 400 are arranged is shown in FIG. have.

Referring to FIG. 3 , first, four battery cells 100 , 200 , 300 , 400 are arranged side by side, and the connecting member 133 is disposed inside the battery case of the battery cells 100 , 200 , 300 , 400 . It extends from the first heat dissipation member 131 mounted to the outside of the battery case, which is bent in the shape of 'C' so that the second heat dissipation member 132 is positioned in the thickness direction of the battery cell 100 . has been Each of the battery cells 100 , 200 , 300 , 400 has the same structure as the battery cell 100 and is arranged side by side, and the second heat dissipation member 132 of the battery cell 100 is the battery cell 100 . ) and the battery cell 200 , and this structure is the same for the other battery cells 100 , 200 , 300 , and 400 .

Therefore, there may be a cooling effect not only from the inside of the battery cells 100, 200, 300, and 400, but also from the outside, and the heat conducted through the connecting member 133 from the inside is not only the connecting member 133, Since it can be cooled through the external second heat dissipation member 132, more efficient cooling is possible, and the battery cells 200 and 300 and one end of the battery cell 400 located inside the arrangement of the battery module are heat-dissipating. Since the member is positioned on both sides of the battery cells 200 and 300 , cooling efficiency may be further improved.

Furthermore, one specific example for further improving the cooling effect in the arrangement 100, 200, 300, 400 of such battery cells is shown in FIG.

Referring to FIG. 4 , at the lower end of the battery module in which the battery cells 100 , 200 , 300 , and 400 are arranged side by side, the heat exchange member 500 is in contact with the surface where the connecting member 133 exposed to the outside is bent. located in state.

Therefore, the heat exchange member 500 is simply formed in a plate shape to achieve cooling by a method such as heat conduction over a large area, to form a refrigerant flow path for the flow of refrigerant, or to form an air flow path through which air can flow. It may exhibit better cooling efficiency.

Hereinafter, the present invention will be described in more detail through examples, but the following examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

<Example 1>

Preparation of anode

_{LiNi 0.6} Co _0.2 Mn _0.2 O ₂ was used as a cathode active material _{, LiNi 0.6} Co _0.2 Mn _0.2 O ₂ 96.25 wt%, Fx35 (conductive agent) 1.5 wt%, PVdF (binder) 2.25 wt% NMP (N) as a solvent -methyl-2-pyrrolidone) to prepare a positive electrode mixture slurry, and then coating, drying and pressing on aluminum foil to prepare a positive electrode.

Preparation of the cathode

As the negative electrode active material, artificial graphite and natural graphite were mixed and used, and the negative electrode active material 95.6% by weight, Super-C (conductive agent) 1.0% by weight, SBR (binder) 2.3% by weight and CMC (thickener) 1.1% by weight as a solvent It was added to phosphorus water to prepare a negative electrode mixture slurry, and then coated, dried and compressed on copper foil to prepare an anode.

Manufacturing of secondary batteries

Another heat dissipation member of the same type connected by a connecting member with an Al heat dissipation member (thickness 0.4 mm) interposed in the middle of the electrode assembly having a structure in which a PE separator is interposed between the positive electrode and the negative electrode as shown in FIG. After the electrode assembly was embedded in a pouch-type battery case, an electrolyte containing VC and 0.7M LiPF6 + 0.3M LiFSI salt was injected into a solvent having EC: EMC = 3:7 to complete a secondary battery.

<Comparative Example 1>

A secondary battery was manufactured in the same manner as in Example 1, except that a heat dissipation member was not used in Example 1.

<Comparative Example 2>

Secondary in the same manner as in Example 1, except that in Example 1, a heat dissipation member made of Al was interposed only in the middle portion of the electrode assembly and one end of the heat dissipation member was exposed to the outside of the battery case by about 5 mm (there was no external heat dissipation member). A battery was prepared.

<Experimental Example 1>

Ten secondary batteries prepared in Example 1 and Comparative Examples 1 and 2, respectively, were prepared in a fully charged state of 4.25V. Using a nail penetrating tester, a nail with a diameter of 3 mm made of iron was passed through the center of the battery made above, and the ignition was measured.

At this time, the penetration speed of the nail was constant at 25 mm/sec, and the results are summarized in Table 1 below.

ignition or not Maximum temperature (℃) Example 1 no ignition 50.2 Comparative Example 1 utterance - Comparative Example 2 no ignition 82.2

As shown in Table 1, in the secondary batteries according to the present invention, ignition does not occur in all ten batteries and the temperature rise is not large, whereas Comparative Example 1 does not have a cooling effect, so ignition occurs, and Comparative Example 2 is partially cooled Although ignition did not occur due to the effect, it can be confirmed that the temperature rise is large.

Those of ordinary skill in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (16)

An electrode assembly of a positive electrode/separator/negative electrode structure is mounted inside a battery case made of a laminate sheet,
one or more first heat dissipating members for dissipating heat generated inside the electrode assembly when charging/discharging or short circuit occurs are mounted in contact with at least one of the inside of the electrode assembly and the outer surface of the electrode assembly;
A second heat dissipation member is positioned outside the battery case; The first heat dissipating member and the second heat dissipating member are thermally connected by one or more connecting members extending from one end of the first heat dissipating member to the outside of the battery case,
A first heat dissipation member 131 for dissipating heat generated inside the electrode assembly is mounted between the separator and the cathode,
The connecting member is bendable in a “C” shape,
The second heat dissipation member is a battery cell, characterized in that it is located in the thickness direction of the battery cell from the outside of the battery case by bending the connecting member. The battery cell according to claim 1, wherein the first heat dissipation member, the second heat dissipation member, and the connecting member are made of a thermally conductive material. The battery cell according to claim 2, wherein the first heat dissipation member, the second heat dissipation member, and the connecting member are made of a metal material. The battery cell according to claim 1, wherein the first heat dissipation member and the second heat dissipation member have a plate-like structure. The battery cell according to claim 4, wherein the size of the first heat dissipating member and the second heat dissipating member is the same as the size of the positive electrode or the negative electrode. delete The battery cell according to claim 1, wherein one end of the first heat dissipation member on which the connecting member is formed is a side on which the electrode tab is not formed. The battery cell according to claim 1, wherein the connecting member has a plate-shaped structure smaller than that of the first heat dissipation member and the second heat dissipation member. The battery cell according to claim 1, wherein the battery case is heat-sealed in a state in which one or more connecting members extending from the first heat dissipation member are interposed on the outer periphery of the housing portion in which the electrode assembly is accommodated. The battery cell according to claim 9, wherein an insulating tape is attached to one or both surfaces of the connecting member that meets the heat-sealed portion of the battery case. The battery cell according to claim 1, wherein the connecting member is attached to the first heat dissipation member and the second heat dissipation member by welding. delete delete The battery cell according to claim 1, wherein the second heat dissipation member is in surface contact with the outer surface of the battery case in the thickness direction of the battery cell. A battery module comprising two or more battery cells according to any one of claims 1, 2 to 5 and 7 to 11 and 14. The method according to claim 15, wherein the battery module includes a heat exchange member, and when the battery module includes n (3≤n≤50) battery cells, The second heat dissipation member is positioned in the thickness direction of the battery cell from the outside of the battery case by bending the connecting member and is interposed between adjacent battery cells, and the second heat dissipation of the n-th battery cell located at the outermost side The member is positioned on the outer surface of the battery cell, and the bent connecting member is in thermal contact with the heat exchange member.

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