Patent Description:
At present, fuse devices used in secondary batteries include a positive temperature coefficient (PTC) thermistor, a thermal cut-out (TCO), a thermal fuse, and the like. However, the thermal fuse is disposable. The PTC or TCO can be used repeatedly, but the resistance increases as the PTC or TCO operates repeatedly, thereby increasing its resistance and thus increasing the resistance of the entire circuit.

In addition, the above elements are all operated by heat generated by overcurrent. That is, the above elements operate to block the flow of current only when an overcurrent is generated on a current path of the circuit due to overcharge or the like and thus the temperature is increased.

Therefore, the above elements are capable of blocking the overcurrent by operating only after a situation where safety is already threatened by heat generation, and it is impossible for the above elements to block the overcurrent immediately when a cause that may raise the temperature occurs.

In addition, since the above elements simply operate according to temperature, it is difficult to use the above elements in a secondary battery that exhibits high output, such as a battery pack used in a vehicle. That is, a battery pack for a vehicle requires a high c-rate, and thus much heat is inevitably generated. However, if the elements such as a positive temperature coefficient (PTC), a thermal cut-out (TCO) a thermal fuse are placed in such a high temperature environment, they may be activated too early.

Therefore, it is required to develop a secondary battery adopting a device that may be reusable, be usable in an environment where a high current flows, and block the occurrence of overvoltage caused by overcharge in advance by forcibly generating a short circuit to consume current before the temperature rises if an event that may cause the temperature rise occurs.

Examples of background art can be found in <CIT>, <CIT>, and <CIT>.

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to preventing the occurrence of overvoltage in advance by reversibly generating a short circuit in advance to consume current before the temperature of a secondary battery rises due to heat generation caused by overcurrent.

In accordance with claim <NUM>, there is provided a battery module, comprising: a first battery cell and a second battery cell respectively having a positive electrode lead and a negative electrode lead and connected to each other in series; and a short circuit inducing member having one longitudinal side interposed between the negative electrode lead of the first battery cell and the positive electrode lead of the second battery cell to be in contact therewith and the other longitudinal side located between the positive electrode lead of the first battery cell and the negative electrode lead of the second battery cell, wherein when a potential difference between the negative electrode lead of the first battery cell and the positive electrode lead of the second battery cell increases over a reference value, the other longitudinal side of the short circuit inducing member makes flexural deformation toward the negative electrode lead of the second battery cell to come into contact with the negative electrode lead of the second battery cell.

The short circuit inducing member includes an electro active polymer (EAP) layer; a first metal layer formed on one surface of the EAP layer; and a second metal layer formed on the other surface of the EAP layer.

The first metal layer is electrically connected to the negative electrode lead of the first battery cell, and the second metal layer is electrically connected to the positive electrode lead of the second battery cell.

When the short circuit inducing member makes the flexural deformation, the second metal layer comes into contact with the negative electrode lead of the second battery cell to induce a short circuit in the second battery cell.

The EAP layer may include at least one polymer electrolyte selected from Nafion, polypyrrole, polyaniline and polythiophene
The first metal layer and the second metal layer may include at least one metal selected from the group including platinum, gold, silver and copper.

The battery module may further comprise a connecting line configured to electrically connect the positive electrode lead of the first battery cell and the negative electrode lead of the second battery cell to each other.

The battery module may further comprise a pair of PTC elements interposed between the first metal layer and the negative electrode lead of the first battery cell and between the second metal layer and the positive electrode lead of the second battery cell respectively.

In another aspect, a battery pack according to an embodiment of the present disclosure comprises the battery module according to an embodiment of the present disclosure. In addition, a vehicle according to an embodiment of the present disclosure comprises the battery pack according to an embodiment of the present disclosure.

According to an embodiment of the present disclosure, it is possible to preventing the occurrence of overvoltage in advance by reversibly generating a short circuit in advance to consume current before the temperature of a secondary battery rises due to heat generation caused by overcurrent, thereby securing safety of the secondary battery in use.

Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the disclosure, while it should be understood that the scope of protection is defined by the appended claims.

Hereinafter, a battery module <NUM> according to an embodiment of the present disclosure will be described with reference to <FIG>.

First, referring to <FIG>, the battery module <NUM> according to an embodiment of the present disclosure includes a plurality of battery cells <NUM> and at least one short circuit inducing member <NUM>, and may further include a connecting line L.

Referring to <FIG> along with <FIG>, the battery cell <NUM> includes an electrode assembly (not shown), a positive electrode lead <NUM>, a negative electrode lead <NUM>, a cell case <NUM>, and a sealing tape <NUM>.

Although not shown in the drawings, the electrode assembly has a form in which separators are interposed between positive electrode plates and negative electrode plates that are repeatedly stacked alternately, and separators are preferably positioned at both outermost sides for insulation, respectively.

The negative electrode plate may include a negative electrode current collector and a negative electrode active material layer coated on one side or both sides of the negative electrode current collector, and a negative electrode uncoated region not coated with a negative electrode active material is formed at one side end of the negative electrode plate. The negative electrode uncoated region functions as a negative electrode tab.

The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer coated on one side or both sides of the positive electrode current collector, and a positive electrode uncoated region not coated with a positive electrode active material is formed at one side end of the positive electrode plate. The positive electrode uncoated region functions as a positive electrode tab.

In addition, the separator is interposed between the positive electrode plate and the negative electrode plate to prevent electrode plates having different polarities from directly contacting each other. The separator may be made of a porous material so that ions may be moved using the electrolyte as a medium between the positive electrode plate and the negative electrode plate.

The positive electrode lead <NUM> is connected to the positive electrode tab by a bonding method such as welding and is drawn out of the cell case <NUM>. The negative electrode lead <NUM> is connected to the negative electrode tab by a bonding method such as welding and is drawn out of the cell case <NUM> in the same direction as the positive electrode lead <NUM>. That is, the battery cell <NUM> applied to the present disclosure corresponds to a one-direction drawing-type battery cell.

The cell case <NUM> includes two regions, namely an accommodation portion 13a accommodating an electrode assembly (not shown) and a sealing portion 13b extending in a circumferential direction of the accommodation portion 13a and thermally fused in a state where the electrode leads <NUM>, <NUM> are drawn out to seal the cell case <NUM>.

Although not shown in the figures, the cell case <NUM> is sealed by affixing and thermally fusing edge portions of an upper case and a lower case made of a multi-layered pouch film in which a resin layer, a metal layer and a resin layer are stacked in order.

The sealing tape <NUM> is attached to a circumference of each of the positive electrode lead <NUM> and the negative electrode lead <NUM> and interposed between the sealing portion 13b of the cell case <NUM> and the electrode leads <NUM>, <NUM>. The sealing tape <NUM> is a part applied to prevent the sealing of the cell case <NUM> from deteriorating due to low adhesion between the inner side of the cell case <NUM> and the electrode leads <NUM>, <NUM>, in a region of the sealing portion 13b of the cell case <NUM> where the electrode leads <NUM>, <NUM> are drawn out.

At least two battery cells <NUM> are provided, and the battery cells <NUM> are connected to each other in series. In the figure (<FIG>) of the present disclosure, a case where four battery cells <NUM> are connected in series is illustrated as an example, but the present disclosure is not limited thereto. That is, the case where two battery cells <NUM> are connected in series, the case where three battery cells <NUM> are connected in series, and the case where five or more battery cells <NUM> are connected in series are also included within the scope of the present disclosure.

Hereinafter, in describing the present disclosure, the four battery cells <NUM> shown in <FIG> will be distinguishably called a first battery cell 10A, a second battery cell 10B, a third battery cell 10C and a fourth battery cell 10D in order from left to right.

Referring to <FIG>, the short circuit inducing member <NUM> is interposed between the negative electrode lead <NUM> of the first battery cell 10A and the positive electrode lead <NUM> of the second battery cell 10B, between the negative electrode lead <NUM> of the second battery cell 10B and the positive electrode lead <NUM> of the third battery cell 10C, and between the negative electrode lead <NUM> of the third battery cell 10C and the positive electrode lead <NUM> of the fourth battery cell 10D, respectively. In this case, the connecting line L connects the positive electrode lead <NUM> of the first battery cell 10A and the negative electrode lead <NUM> of the second battery cell 10B to each other, connects the positive electrode lead <NUM> of the second battery cell 10B and the negative electrode lead <NUM> of the third battery cell 10C to each other and also connects the positive electrode lead <NUM> of the third battery cell 10C and the negative electrode lead <NUM> of the fourth battery cell 10D to each other.

In describing the short circuit inducing member <NUM>, the short circuit inducing member <NUM> interposed between the negative electrode lead <NUM> of the first battery cell 10A and the positive electrode lead <NUM> of the second battery cell 10B will be described as an example.

The short circuit inducing member <NUM> physically connects the opposite electrode leads <NUM>, <NUM> of neighboring battery cells 10A, 10B to each other, and its shape is deformed when a potential difference between the negative electrode lead <NUM> of the first battery cell 10A and the positive electrode lead <NUM> of the second battery cell 10B increases over a reference value due to overcharge.

Due to this shape deformation, the short circuit inducing member <NUM> comes into contact with the negative electrode lead <NUM> of the second battery cell 10B, and accordingly, the positive electrode lead <NUM> and the negative electrode lead <NUM> of the second battery cell 10B are directly connected to each other, thereby generating a short circuit. If a short circuit occurs like this, the voltage of the second battery cell 10B drops sharply, and it is possible to escape the risk of overvoltage caused by overcharge.

Referring to <FIG>, a structure and operating principle of the short circuit inducing member <NUM> for inducing a short circuit through shape deformation according to the potential difference are shown.

First, referring to <FIG>, the short circuit inducing member <NUM> includes an electro active polymer (EAP) layer <NUM>, a first metal layer <NUM> formed on one surface of the EAP layer <NUM> and a second metal layer <NUM> formed on the other surface of the EAP layer <NUM>.

The EAP layer <NUM>, namely the electro active polymer layer, corresponds to a layer made of a polymer electrolyte having excellent ion transport properties, and, for example, may include at least one polymer electrolyte selected from Nafion, polypyrrole, polyaniline, and polythiophene.

The first metal layer <NUM> and the second metal layer <NUM> are formed on both surfaces of the EAP layer <NUM>, and may be made of metal having excellent electrical conductivity. The metal layers <NUM>, <NUM> may include, for example, at least one metal selected from platinum (Pt), gold (Au), silver (Ag), and copper (Cu).

If a voltage over the reference value is applied through the metal layers <NUM>, <NUM> formed on both surfaces of the EAP layer <NUM>, the short circuit inducing member <NUM> causes shape deformation. Referring to <FIG> along with <FIG>, the short circuit inducing member <NUM> disposed between the first battery cell 10A and the second battery cell 10B causes a flexural deformation in a direction away from the negative electrode lead <NUM> of the first battery cell 10A, so that the second metal layer <NUM> comes into contact with both the positive electrode lead <NUM> and the negative electrode lead <NUM> of the second battery cell 10B.

That is, at one longitudinal side of the short circuit inducing member <NUM>, the first metal layer <NUM> contacts the negative electrode lead <NUM> of the first battery cell 10A, and the second metal layer <NUM> contacts the positive electrode lead <NUM> of the second battery cell 10B. Here, since the second metal layer <NUM> comes into contact with the negative electrode lead <NUM> of the second battery cell 10B due to the flexural deformation at the other longitudinal side of the short circuit inducing member <NUM>, a short circuit is generated in the second battery cell 10B.

The principle of the flexural deformation of this short circuit inducing member <NUM> is as follows. For example, in the case where the first metal layer <NUM> is connected to the negative electrode lead <NUM> of the first battery cell 10A and the second metal layer <NUM> is connected to the positive electrode lead <NUM> of the second battery cell 10B, the mobility cation that exists inside the polymer electrolyte moves toward the first metal layer <NUM> charged to negative polarity in a state of being hydrated in water. In this case, since osmotic pressure is caused due to an imbalance in ion concentration between the first metal layer <NUM> and the second metal layer <NUM>, the amount of water molecules at the first metal layer <NUM> charged to negative polarity increases, and thus flexural deformation is made at the short circuit inducing member <NUM> toward the second metal layer <NUM>.

The potential difference that may cause flexural deformation of the short circuit inducing member <NUM> depends on the type of polymer electrolyte in the EAP layer <NUM> used for the short circuit inducing member <NUM>. That is, the reference value of the potential difference mentioned in this specification may vary depending on the type of used polymer electrolyte, and accordingly, by selecting an appropriate polymer electrolyte according to the safety voltage range of the battery cell <NUM> and the battery module <NUM> to which the short circuit inducing member <NUM> is applied, it is possible to prevent the occurrence of danger caused by overvoltage by inducing a short circuit rapidly when an event such as overcharge of the battery module <NUM> occurs.

Next, a battery module <NUM> according to another embodiment of the present disclosure will be described with reference to <FIG>.

The battery module <NUM> according to another embodiment of the present disclosure is different from the battery module <NUM> according to the former embodiment of the present disclosure just in that at least a pair of PTC elements <NUM> is more applied, and other components are substantially the same.

Therefore, in describing the battery module <NUM> according to another embodiment of the present disclosure, the PTC element <NUM>, which is an additionally applied component, will be described in detail, and other components will not be described in detail.

The PTC element <NUM> has a resistance value gradually increasing as the temperature rises, and if the temperature reaches a reference temperature or higher, the PTC element <NUM> exhibits an infinite resistance value to substantially block the current completely. The PTC element <NUM> is interposed between the negative electrode lead <NUM> of the first battery cell 10A and the first metal layer <NUM> and between the positive electrode lead <NUM> of the second battery cell 10B and the second metal layer <NUM>. In addition, the PTC element <NUM> is interposed between the negative electrode lead <NUM> of the second battery cell 10B and the first metal layer <NUM> and between the positive electrode lead <NUM> of the third battery cell 10C and the second metal layer <NUM>. Similarly, the PCT element <NUM> is interposed between the negative electrode lead <NUM> of the third battery cell 10C and the first metal layer <NUM> and between the positive electrode lead <NUM> of the fourth battery cell 10D and the second metal layer <NUM>.

In addition, the PTC element <NUM> may be entirely coated on the first metal layer <NUM> and the second metal layer <NUM> of the short circuit inducing member <NUM>.

If the short circuit inducing member <NUM> operates due to overvoltage generated in the battery module <NUM> to cause a short circuit, the PTC element <NUM> may cut off the short circuit current at the reference temperature or above, thereby preventing the risk of ignition or explosion caused by overheating in advance.

Meanwhile, referring to <FIG>, a battery pack <NUM> according to an embodiment of the present disclosure may include at least one battery module <NUM> according to the present disclosure. In addition, referring to <FIG>, a vehicle according to an embodiment of the present disclosure may include the battery pack <NUM> according to an embodiment of the present disclosure.

Claim 1:
A battery module (<NUM>), comprising:
a first battery cell (10A) and a second battery cell (10B) respectively having a positive electrode lead (<NUM>) and a negative electrode lead (<NUM>) and connected to each other in series; and
a short circuit inducing member (<NUM>) having one longitudinal side interposed between the negative electrode lead (<NUM>) of the first battery cell (10A) and the positive electrode lead (<NUM>) of the second battery cell (10B) to be in contact therewith and the other longitudinal side located between the positive electrode lead (<NUM>) of the first battery cell (10A) and the negative electrode lead (<NUM>) of the second battery cell (10B),
wherein when a potential difference between the negative electrode lead (<NUM>) of the first battery cell (10A) and the positive electrode lead (<NUM>) of the second battery cell (10B) increases over a reference value, the other longitudinal side of the short circuit inducing member (<NUM>) makes flexural deformation toward the negative electrode lead (<NUM>) of the second battery cell (10B) to come into contact with the negative electrode lead (<NUM>) of the second battery cell (10B),
wherein the short circuit inducing member (<NUM>) includes:
an electro active polymer (EAP) layer (<NUM>);
a first metal layer (<NUM>) formed on one surface of the EAP layer (<NUM>); and
a second metal layer (<NUM>) formed on the other surface of the EAP layer (<NUM>)
wherein the first metal layer (<NUM>) is electrically connected to the negative electrode lead (<NUM>) of the first battery cell (10A), and the second metal layer (<NUM>) is electrically connected to the positive electrode lead (<NUM>) of the second battery cell (10B),
wherein when the short circuit inducing member (<NUM>) makes the flexural deformation, the second metal layer (<NUM>) comes into contact with the negative electrode lead (<NUM>) of the second battery cell (10B) to induce a short circuit in the second battery cell (10B).